My Megasquirt adventures over the years

[Map63Vette]

So now that my car has become my primary daily driver, I've been spending a lot more time working on the tune and digging into the little details of things to try to get it running as nicely as I can. For a little history and backstory, my car started life with me as a carbed 318 with a 4 speed. That eventually changed to a carbed 2006 5.7 Hemi with the 4 speed, then I converted it back to fuel injection and put in a 6 speed. I bought my engine with no electronics, so that was one reason I went carb at the start. My Megasquirt adventure began when the guy I sold the stock 5.7 intake to told me he knew a guy taking a system off a 340 if I was interested. I was, and it seemed like too good of a deal to pass up, even if I wasn't going to put it on my car right away. The guy was basically selling a "fuel inject a small block Mopar in a box" kit. I got everything from an intake manifold, throttle body, fuel rails, injectors, fuel pump, wideband O2 sensor and controller, computer, power distribution panel, wiring, etc. I sold off everything I didn't need for the Hemi an ended up with a nice Megasquirt 2 v3.57 system and components for about $200.

Some quick background on the engine as well:
2006 5.7 Hemi
Truck timing cover
Indy ModMan intake
TTI headers
Inertia Motorsports SRT Max Plus cam (with 6.1 exhaust springs on all the valves)
Otherwise stock bottom end and heads, just freshened up with new gaskets/seals/rings/etc.

So this is where the saga begins. I had already bought an Indy ModMan intake for my carb swap (limited other carb options at the time), which I knew could be set up for injectors. I had the MSD Hemi 6 running my ignition for the setup as well. I inquired with Indy about drilling the manifold, but it was going to be more expensive than I wanted. I found an injector drill bit and had a friend at work with a mill, so I bought some blank fuel rail lengths and took them both over to his place and we drilled everything out so I could get the injectors installed. My MS was set up to run a distributor and coil style ignition system (only one spark output basically), so it wasn't going to run the Hemi coils without upgrading. I opted to run the MS as a fuel only setup and leave the MSD box to control the spark. I set up the system as batch fire with two banks of injectors, so 4 injectors would fire at a time. It was fairly simple to set up the MS to run fuel only as I didn't have to worry about any cam or crank triggers or anything like that. I just took the tach output from the MSD box and fed that to the MS to run things. I couldn't tell you where my initial tune came from. I think it might have been the VE table generator in the program (using published hp/tq numbers and rpms), or maybe it was the base 350 Chevy map, who knows. It was 10+ years ago and I know at one point I started that whole tune over from scratch. This initial setup was fairly basic. I wasn't using many of the features/capabilities of the MS, largely because a lot of them control spark to do things (like traction control), and I didn't have that. I had my idle control set up open loop to just modulate my IAC with coolant temp. It ran fine, though I never would stop tinkering with it. Every time I'd get it to the point that it was running pretty good (I thought), I'd tell myself I just needed to leave it alone and enjoy it for a while, but then I'd start looking at things and figuring out the next thing to mess with. The first big overhaul to the system was rewiring everything. The power distribution module that I got with everything liked to melt the fuel pump fuse housing, though never blew the fuse. It was a screw terminal setup and just kind of hokey, so I moved a lot of that stuff into a little enclosure in the engine bay and wired sensors directly into the main MS plug. I drove the car on and off over the years with this setup, but ultimately speaking it really didn't get all that much road time. I would take it to work here and there, but without A/C it was definitely a "fair weather" kind of car. The cover probably only came off once or twice a month if that and it kind of just languished in the driveway.

I did some pretty dumb stuff with the tune on the setup over the years. Probably one of the first "head slap" moments I had was when I set up my original AFR targets to gradually richen the mixture going from cruise to power. I thought it made sense at the time because it made for a nice smooth looking table that went from ~15:1 at light load cruising and gradually worked its way up to 12.5:1 or so on the top end, but that also meant that I could be cruising at 14:1 or something depending on where I was in the table. That's not really how modern engines work, as they generally operate at 14.7:1 almost everywhere but the top end, so I retuned it so the majority of the table was 14.7 and only the top end of load and rpm dropped that for power.

 

[Map63Vette]

Fast forward a few years and I was looking for the next project and things to put on a Christmas/birthday wish list, so I had the idea to upgrade my MS2 setup to an MS3X so I could run the ignition and get all of my tuning in one place vs having to tune the fuel and ignition separately. I got the parts for Christmas and the big redo started a couple of winters ago. I pull the whole harness out of the engine bay and started fresh as I was going to be adding quite a few new things and I had a nice fuse/relay panel I got from work to make things look a little better. I also had a scrap harness from work I could salvage wires from. The biggest challenge was figuring out what all the OEM connectors were as I did not want to do pigtails and splices for everything, but real crimped connections. I managed to track them all down and made a big spreadsheet with all my circuits and the part numbers for the connectors, terminals, seals, etc. for future reference (happy to share if anyone is looking for any particular connector). I also took this opportunity to drill some new holes in my firewall to run bulkhead connectors for all of the new engine wiring instead of passing it through a hole with a grommet like I did before. One connector is dedicated to power (so things like injectors, coils, etc.) and the other is for sensors and signals. I also had to grab a set of spark modules as the MS can't run the Hemi coils directly. I made my ignition table by copying what was in the MSD at the time and got it all back on the road and running again. It seemed to run a little better with the sequential injection now, and having a real spark table was nice compared to the old MSD setup of an rpm curve and a vacuum curve. The MSD was basically a 2D + 2D setup, which isn't quite the same as a real 3D table. While it did seem smoother for fueling, I felt like I lost some get up and go in the conversion as well. The main issue I had initially is that the car couldn't even drive in 6th gear on the highway. It just had no power, but it would do okay if you dropped down to 4th or 5th. This started my quest for timing tables as I tried several. I found some OEM ones, but I had a hard time understanding the best way to use them and there was all sorts of confusion about the numbers on them throughout the internet since they were so low compared to typical engines. It also doesn't help that there are multiple tables (like MBT and WOT varieties). I tried doing a blend of the two originally, pulling WOT table values for anything above 80% load or so, but the car just really didn't like that much. I don't recall exactly what I settled on at the time, but I think I basically just ran the MBT table and pulled some timing from the top as a safety blanket.

I was also starting to look more fully into closed loop idle control as my electric fans put a noticeable strain on the engine at idle and I wanted to be able to adjust for that. That was basically a lot of guessing and checking, and I eventually got it working "good enough" for the time. It would settle okay and bump up the idle a tad when the fans came on so at least the car didn't want to die. I had some spare inputs on the new computer as well, so I decided it would be fun to a add a front wheel speed sensor so I could have traction control. Since I was going through that trouble, I also figured I might as well have launch control, so I looked at ways to get an input from the clutch for it. The main thing I wanted was some tunability in the switch point as the old MSD setup was just a button for the rev limiter, and if you let go of the button before the clutch started biting, the revs would climb too quick and shock the tires like a regular clutch drop. I was originally trying to figure out how to get a pressure switch in the clutch line so I could set a trigger based off of pressure, but I couldn't find a nice way to do it that didn't take something silly like three different fittings to adapt things, so I ended up putting a potentiometer under the dash with a string to the pedal. It actually seems to work pretty nicely and gives me the tunability I was looking for. So now I had everything working pretty nicely again, but my O2 sensor was getting really weird with me. It was an older Innovate LC-1 unit and I had found the software to adjust settings on it and flashed it to a newer firmware and changed some response rates on it looking for better performance, but I think my sensor might have been going south. It was probably 15 years old at this point, so maybe not that surprising. Since I had been messing with adding CAN bus functionality to my car, I ended up getting a 14Point7 Spartan 3 v2 to replace it. It can run either via CAN or traditional 5v output, so I was covered either way. I liked the idea of CAN as it would reduce the chance of any kind of signal interference on an analog line.

Somewhere along the line I also finally managed to track down a knock module to add to my install so I could have knock control. I had been waiting for DIYAutoTune to start selling them again, but they had been out of stock for years and there was no word on them coming back. I found the chip they were using on the board and debated trying to reverse engineer the module myself, but luckily someone had already done that and was selling them on Ebay for the same reason (they were fed up with them being out of stock). I still had the OEM knock sensors on the engine so they got wired up and the switch flipped in the software. I didn't really tune anything at the time because it sort of seemed to "just work" with the default settings, though there was no really easy way to tell without trying to trigger them, which I was hesitant to do given the fragility of the ring lands on the pistons. The knock sensor output numbers on the software seemed to be reasonable though, so I just kind of left them there.

 

[Map63Vette]

At this point I thought I had things running pretty nicely (again), and I just got a new job at the end of last year that was going to have me commuting regularly again. My Viper was my go to commuter previously, but after a cam swap it was getting so loud to drive on the highway that I didn't think my ears would survive. It was also having some A/C issues (a broken blend door), that made it less than comfortable to drive on hot days. On top of that, it doesn't get the best gas mileage (go figure), so the Dart was looking more and more appealing as my standard option. It was called up for daily service and I got a lot of seat time in it and noticed while driving back and forth that my AFR readings were varying a noticeable amount between my morning and afternoon commute as the temperature rose through the day. This started the latest rabbit hole that has sunk many hours of my life over the last few days and taught me a lot about the right way to tune stuff. I dug more into the various settings and tables on the MS and found the MAT correction curve, which seemed like the hot ticket. It's what controls how much fuel is added or removed based on air temp, so with a couple of tweaks on this table I was getting more stable numbers between the morning and afternoon (more on this to come). One of the things I learned while researching the MAT correction curve is that the fuel injector settings can have an effect on them, primarily dead times/offset/whatever you want to call it (the time between the computer sending a signal and an injector first spraying any fuel).

And so the quest for OEM data began. The problem I had was that I had stock injectors. That's only a "problem" because they tend to be difficult to find good data on. People usually go aftermarket with injectors, so the companies often have data available for their products. The OEM stuff not so much. I got the idea that maybe I could pull some numbers from a stock tune file off of something like HP Tuners. The software is free to download and look through tunes with, and as luck would have it, they have a 2006 5.7 Hemi from a Chrysler 300 in the example files. Based on what I could find, it used the same injectors that were on my engine. I also took this opportunity to look through all of the various settings in HP Tuners to try to get an idea how the stock controller handled things. Looking over the timing tables I got the brain blast of how to implement the WOT and MBT tables in a more factory way. The MS has table switching functionality. Most people tend to implement this via a switch for doing stuff like running pump vs race gas or a lean vs rich tune or something like that. I decided to use it to emulate the open/closed loop functionality that OEM controllers do. Technically I'm always "closed loop" since I have wideband feedback, but I configured my setup to switch timing tables at WOT. So I can use the full MBT table for cruising and the WOT table for power. This solved a problem I had before where if I was cruising at low rpm in 6th gear and hit a steep hill and rolled into the throttle I could see the upper end of my VE table on load, but I still wasn't near 100% TPS and didn't need the "power" table. I could leave my AFR target at 14.7 and keep my timing to go with that, but on a hard stab of the throttle it now switches over to the WOT table and gives me the rich mixture and timing to go with it.

With that rabbit hole chased, I went back to seeing what over values I could pull from the HP Tuners tune to adapt to MS. I tried pulling over the VE table and the injector data, but this led to a bit of an issue one morning. I had loaded the tune in the night before and never tested it, so when I went out to go to work the next morning I couldn't get the car to start and stay running long enough to get out of the driveway. I changed stuff back later that day and tried finding some more info on the injectors online. I found some other dead time data that I tried that seemed to work better. I was never sure what size injectors they actually were though. The few places I could online that listed any info at all weren't clear about what pressure they were tested at. The Hemi runs 60 psi fuel pressure stock, but the vast majority of injector data out there is at 43 psi. It's easy enough to convert between the two, but it's never obvious whether or not you are supposed to. The car ran well enough with the new dead times I had found though, and it was actually quite smooth most of the time. I still had some nagging idle issues and weird AFRs though.

I had also added A/C recently, and I learned that my closed loop idle settings were not as good as I had hoped. When the A/C kicked on, I would get a lot of idle surging and AFRs swinging all over the place. I tried playing with the PID settings and I could get it to work okay, but it was never really consistent. I finally learned while sitting in the parking lot at lunch one day watching the gauges what was really going on. Long story short, I have a programmed starting position for the IAC based on temperature and rpm set point, and it was waaaay of where the car actually wanted to settle when it finally would. I adjusted the starting position to be just a bit above where it likes to settle and magically it would actually idle pretty stably now. I still get a little surging if I turn the A/C on right after starting the car, but I'm continuing to work on that. I still had some strange issues with AFRs during warmup and initial starts though.

On a cold start the car likes to idle pretty lean (like 16-17:1), but when I'm actually driving it will run rich (like 14:1). The rich part is fine as my EGO control doesn't come on till 160 degree coolant temp, and it's set to run rich, but that didn't explain why the idle was lean if it ran rich otherwise. Then, once the car heats up, it liked to idle rich (like 14.4:1), but would run lean while driving (15:1). I also recently watched some interviews with Greg Banish (former OEM engine calibrator, really interesting stuff) and he was stressing the importance of having really accurate injector data as on speed density systems, that's kind of where everything starts and any errors there just compound down the line. So I started looking back into the injector data on HP Tuners and the equations the MS was using. I vomited numbers onto pages and pages of spreadsheets and made all sorts of graphs trying to understand what was going on. After reviewing everything, it finally clicked for me what was going on and reminded me of something I heard on the interviews. Every OEM characterizes injectors differently. The MS appears to use a more GM based approach, while Dodge takes a slightly different one. The Dodge data that I had in HP Tuners calls "zero" the moment when fuel first starts coming out of the injector. The MS calls "zero" the moment the computer sends a signal to the injector. That explained why the dead time values I tried to copy straight from HP Tuners originally were way off and caused problems when I first tried them. I made several more graphs overlaying the Dodge data with the way MS calculates things and came up with some new values I put in the car this morning. It might just be my imagination, but it felt like it was running even better this morning and more smoothly everywhere. I'm back to adjusting my VE tables all over again since I changed all the injector info, but fingers crossed this might be the "last" time I mess with it.

All of this stuff will probably make more sense with some pictures, so my plan is to go through my tune and take a bunch on screenshots to add here in the near future. My hope is to explain everything I've learned and to identify some of the snagging points that people seem to run into (at least based on what I found while researching my own issues). It's been a long ride and it's hard to believe how far I think my car has come from the first day I turned the key with the MS. I'm at the point now that I feel like I have a very "OEM-like" tune, and the goal is to make the car act as much like a modern car as possible where anyone can just turn the key and go.

 

[DionR]

I had an MS setup for a /6 that I sold years ago. If I hadn't sold it, I could see myself having gone down a similar path.

Curious if you have tried any of the auto-tune or self tuning features?

 

[mopar head]

Heck of a write up.
This right here gentlemen, is why this dummy-"me" will only run carbs...

 

[Map63Vette]

I had an MS setup for a /6 that I sold years ago. If I hadn't sold it, I could see myself having gone down a similar path.

Curious if you have tried any of the auto-tune or self tuning features?

Oh yeah, I'm pretty deep into the ecosystem now, lol. I cracked and pretty much bought all the software upgrades at this point. Megalog Viewer HD (for autotuning from logs instead of live mostly), originally had the paid TunerStudio but semi-recently upgraded to the full Pro version. I don't recall everything that changed between them (I'm sure the website lists differences), but figured I mess with it enough and it's pretty cheap in the long run comparatively speaking. It's like, $300+ to buy the tuning software for SCT to tune my Viper, and I think that's still locked to just one car or one brand or something like that. I think all the EFI Analytics stuff combined is like, $120 for a package you can have on three computers at once and tune as many vehicles as you want with it (assuming I had any more to tune, lol).

I have used both the live and log based tuning quite a bit. It's handy, but there are caveats. Ideally, you still want your tables to be moderately close to start with. You want it to tweak things, not necessarily build them from scratch. I guess it probably can do that, as long as you can get the engine to run to start with, but it can lead to some pretty spiky tables. Maybe that doesn't matter, but in my head at least airflow shouldn't be changing that drastically from one cell to another, so I wouldn't think the tables values should either. It is kind of fun to watch it bring a table in and to see the AFR stabilize. The offline tuning is almost nicer to use in some regards. It has all the same functionality, but it's nice to be able to try out different filters on the same data to see how it wants to change things.

Maybe one of the most important things for the start of any tune is actually turning off the EGO, at least if you are tuning by hand. You can probably leave it on if you are running the auto-tune, but if you are tuning by hand and the EGO is pulling things all over the place, it's hard to see the effects of your change. I was looking at some datalogs someone else sent me that was having trouble getting his tune dialed in and one of the first things I noticed was the EGO correction swinging back and forth by huge chunks. In my eyes at least, the ultimate goal of any tune is to not need the O2 sensor to operate. It is for minor day to day variations and component wear, not necessarily primary control. In theory, you should only need to know things about what is going into the engine (air and fuel), not what is coming out, at least not once it is tuned.

 

[Map63Vette]

Heck of a write up.
This right here gentlemen, is why this dummy-"me" will only run carbs...

Lol, I know I probably get a bit too wordy at times. I still have a carb on my 71 Vette, and the carb that came on the 318 that was in my Dart when I bought it ran like fuel injection. You could just turn the key and go, no waiting or anything. I never knew a carb could do that, though I also didn't drive it in every weather condition to see the full extent of its tune. I do know that the Hemi did not care for a carb with the ModMan intake though. I tried and tried and put all sorts of different rods and jets and springs and stuff in it, but I never could get it to work. I just don't think the intake was well suited for it, and I probably would have still been messing with it if I didn't get the screaming deal I did on the Megasquirt.

I mostly just wanted to share the success I'd found with it and some of the cool things you can do. There's no doubt the OEM computers are more sophisticated and capable, but they also have to do a lot more stuff than us average shade tree mechanics would care about (like emission control). However, their specialization at controlling things so precisely for a stock setup is kind of their downfall in some regards as soon as you start changing things. OEMs run thousands of hours on dyno with all sorts of sensors to optimize things and meet all sorts of requirements and durability ratings to get those values. It's silly to think I can get anywhere close to that with just some driving back and forth to work every day, but that doesn't mean I'm not going to try, lol. That whole OEM engine controller is basically one big mathematical model of airflow and chemistry (an engine is just an air pump after all, they say). Their model accounts for all sorts of things, so I always cringe a little whenever I'm watching videos where tuners are talking about zeroing out whole tables or setting stuff to constant values or stuff like that. I get why they are doing it, it simplify the process so you have less variables to control. The thing is, those variables were there for a reason.

One of the most recent ones I ran into was a thread on some forums where people were talking about zeroing out the MAT correction table on the MS when you make your base tune, but still having issues with hot starts or idling or it driving different at constant speed vs around town. It generally boils down to bad assumptions, the biggest being that people seem to think the temperature value their IAT sensor reads is the same temp as the air going into the cylinder. My MAT sensor is in the #8 runner and it's wild how much the temperature can change with just some change in throttle. On average, my MAT values are 20 degrees higher than ambient temps at steady state on the highway. That's how much the air heats up just going through the intake, and probably still even a little more after the sensor before it gets to the cylinder. If I roll off the throttle and start coasting you can watch the temps climb 5-10 degrees in seconds. Get back on the throttle and they start going back down. Imagine how much worse it gets if your IAT is all the way up at your throttle body. An OEM plastic intake would probably actually be better than my aluminum one in that regard as I would expect less heat transfer. There's actually a table in the OEM controller that models the heat gain between the IAT sensor and the cylinder if I remember correctly.

 

[mopar head]

Lol, I know I probably get a bit too wordy at times.

A bit?


It`s all good bud, some people, like you probably enjoy the challenge, that **** would drive me nuts

 

[Map63Vette]

A bit?


It`s all good bud, some people, like you probably enjoy the challenge, that **** would drive me nuts

I've often joked I should really just turn off my dash screen and drive the car and I'd never know any better. Kind of like a carb, if it feels okay then it must be running good enough. My problem is that I'm an engineer and I like data, so being able to see all the numbers is a blessing and a curse. My frame of mind at the moment is mostly "make it as efficient as possible" since it's my daily, and "keep it in a happy place" so I don't hurt stuff prematurely. So don't run it so lean that it causes issues, or run it so rich that it causes different issues. Realistically, anywhere between in the 14-15:1 AFR region would probably be more than okay and I'd likely never know the difference or hurt anything.

The other problem is my parents have Hemi equipped vehicles so I have an idea how they should feel, which just keeps pushing me to try to refine things more. It's also a "free" hobby in the sense that tuning doesn't cost me anything. I'm burning gas regardless since I have to commute, so I might as well try to make it as good as I can.

 

[Map63Vette]

****DISCLAIMER: THE VAST MAJORITY OF POSTS BY ME FROM THIS POINT ON ARE MY OWN EXPERIENCE/OPINIONS/UNDERSTANDING ON HOW THESE SYSTEMS OPERATE BASED ON THE INFORMATION I COULD FIND. ALL VALUES ARE FROM MY PERSONAL TUNE AND SHOULD BE TAKEN WITH A HEAVY GRAIN OF SALT. I HAVE A PRETTY WEIRD ENGINE SETUP THAT I HAVE NOT SEEN ANYWHERE ELSE, SO I WOULD NOT EXPECT THEM TO WORK FOR YOU OUT OF THE BOX. IT IS ENTIRELY POSSIBLE THAT SOME OF THE INFORMATION I WILL GIVE IS INCORRECT. IT'S GOING TO GET TECHNICAL. I APOLOGIZE IN ADVANCE.****

So that being said, let's start from the top and follow in Uhcoog1's footsteps and walk through the main MS settings. I also plan to put some HP Tuner info side by side to explain where I got my values from and how I adapted them for use on the MS. I spent way too much time searching for stock values only to find them right under my nose (HP Tuners includes some example files, I was incredibly fortunate that a 2006 5.7 just happened to be one of them). All of the below is based on my current tune as of today (Aug 7, 2025) running firmware 1.6.0.

Basic settings - these define the very basic values of your engine, like how big it is and what sort of control algorithm you want to run. I tried to highlight some of the key values here in red boxes:

The required fuel value is the basis from which all MS calculations are done. Technically speaking you can get this "wrong" and still tune the car to work fine (ask me how I know...), but it might make your tables look a little funny. The control algorithm defines what formula MS uses to calculate how much fuel to inject and determines what kind of sensors you need for your installation. Speed density is what most Dodge products run as far as I'm aware. That setup relies on knowing the pressure and temperature of air in the manifold to estimate the mass. The other main algorithm used by OEMs that I'm aware of is Mass Air Flow. It measures the air mass more directly via a MAF sensor. If you were feeling fruity you could probably retrofit a MAF sensor onto your engine and run this way, but I have a carb style throttle body setup on mine, so I kept it speed density. MS will calculate the required fuel value based on the information put in the box on the far right of the screenshot. This was more of a struggle for me than it should have been and goes back to my lack of information regarding OEM injectors. I searched high and low for values, but never got the full story anywhere I looked. The main caveat is that a lot of places list injector values at 43 psi as that is one of the "standard" pressures that fuel systems run at. Dodges tend to run at 60, so unless the data you have specifically states flow at 60 psi, be wary. I pulled the 30 number from injector data in HP Tuners (more on that to come). The air fuel ratio here depends on what fuel you want to run. Conventional wisdom says to pick 14.7 for pump gas, but a lot of pump gas nowadays is 10% ethanol (E10). The stoichiometric AFR for E10 blends is typically closer to 14.4. The HP Tuners information backs that up:

It's weird, but for some reason Dodge likes to use the reciprocal value for everything. 1 divided by 0.0694 equals 14.41, so that seems to be what Dodge is expecting you to put in the tank for base values. I changed my value to 14.4 to calculate my required fuel, then changed it back to 14.7 later without recalculating (for other reasons I'll mention later).

The rest of the settings on the page are fairly straightforward and the tooltips provided do a good job of explaining things.

 

[Map63Vette]

General settings are up next. These extrapolate more on how the calculations will work and include some sensor smoothing options:

I've seen some people get confused with the baro sensor limit settings. These limits are only for the reference air pressure taken when power is first applied to the system, not the values you might see while the engine is running. There are a couple of different ways the MS can handle barometric correction. If you drive in a place where the altitude doesn't change much, initial MAP reading should suit you fine. What happens is when you first turn the key, the MS records the air pressure before the engine is running to use as a reference for all further calculations. This of this like setting an altimeter on a plane based on the local air pressure. If you are driving up a mountain, this could cause some issues because you probably started your car either at the top or the bottom, and the pressure on the other end is likely pretty different. You can run two separate sensors to combat that issue though. One would be installed in the manifold like normal and the other would be left open to measure static air pressure. This lets the system adjust the reference on the fly.

The general sensors section describes how signals get smoothed between the sensors and the MS. Higher values mean less smoothing. Ideally, you'd have all the values at 100 if you have good clean signals with strong connections and no interference. You might smooth some signals just to make them look nicer on gauges though, like coolant temp or stuff like that.

The right side of the page goes into more detail about your control algorithms. This is related to the original selection on the last page, but I believe is slightly different. These settings determine how the y axis for the fuel table and the ignition table are calculated, independent of the actual algorithm that calculates how much fuel to inject. I haven't messed with these, though I could see how it could possibly be useful. The main setting on here is the "incorporate AFR target". The has to do with the fueling equation and setting this to include the AFR target makes tuning a little easier in my book. It will get more apparent once we start looking at tables, but if you don't include the target, you have to build you fuel enrichments into your main VE table. Functionally speaking they will work the same way, but it gets a lot easier to change things later if you keep the enrichments on the AFR table instead of the VE table, plus it makes table switching (more on that later) easier. This is also where the stoichiometric setting comes up again. It's tied to the value from the last page as well, so if you change it on either of these windows it will change the other. It's hard to explain exactly why to leave this at 14.7 vs the 14.4 I talked about before. It's easier if you think in lambda, which normalizes AFR to the fuel in use. In lambda terms, 1.0 is stoichiometric, regardless of the fuel being used. So whether you put methanol or gasoline or rubbing alcohol in the tank, if you are putting in the correct amount of air to burn it all lambda is equal to 1. I believe most O2 sensors actually read lambda natively and then convert that to whatever number you want for the fuel you are using. I am thinking about changing my tune over to read lambda, but haven't taken that plunge yet. My understanding was that the Megasquirt source code had 14.7 built so deeply into the calculations that it was hard to get away from thinking of it as "normal", even if the fuel is slightly different. Maybe that's changed, but I haven't dug into it enough to see for myself yet.

 

[Map63Vette]

I didn't touch too many of the other settings in this tab. I believe several are only used based on which control algorithm you pick.

Engine state settings is useful to set up, but as best I can tell doesn't really do too much right now. These values define general conditions your engine is in that can be used for some other settings. The primary uses are the VSS threshold (for idle control), the TPS closed, and the overrun for stuff like cutting fuel while coasting. Otherwise, they are just handy for datalogging to see what your engine was doing at a glance.

The fan control page has some novel settings, but is pretty dependent on what fan setup you have to begin with. I could theoretically run a mechanical fan on my truck water pump, but I have some generic dual electric fans on the car right now. I got a little clever with my wiring and opted to run them independently as I wanted one fan to run all the time when the A/C was on, but the other to only come on as needed when the temperatures went up. I have mine set up to bump my idle slightly as well because they hit the electrical system pretty hard when they come on. I also recently adjusted them to turn off over 40 mph because my A/C could keep up fine at that point. Lots of fun little stuff you can do on that page like having them shut off at WOT as well if you wanted that little extra bit of power.

Alternator control was another big update I did on my car with the MS3X upgrade. I was originally running an old factory voltage regulator, but it looked like I was melting the silicone potting compound out of it and I'm not sure it was built to handle the field current of my modern alternator. I got to looking and found that the MS could control it for me, and I had a spare high power output available, so I made the swap. The main control settings were found via the Megasquirt manual. The other values you can play with as they suit you. I have mine set up to drive the alternator a little harder after startup to top the battery off from the starting event, then taper down to a lower voltage for normal running. If you add battery temp or current sensors you can get even fancier, but my car is still pretty basic as far as electronics are concerned, so I kept it fairly simple. So far it seems to work great and it got one more thing off my fender.

 

[Map63Vette]

These next two are probably some of the most important settings and ones that I think a lot of people don't properly account for or understand, the Air density and MAT/CLT correction curves:

I mentioned this in my original post, but the air density correction curve especially people seem to take a lot of liberties with. In my opinion, I don't think they understand the physics of the situation and they use it as a band-aid. Actually, you can see in my screenshot I'm guilty of using it as a band-aid at the moment as well, though I'm planning to try to remedy that. I believe the long version of the story is that this curve used to be hard baked into the code, but people were having issues with heat soak and other things, so they moved it out where it could be modified. I think the biggest thing that drives people messing with this table comes down to sensor placement. What the air density curve is doing is modeling how the mass in the intake is changing as the temperature increases and decreases. As the tool tip and text above the graph state, in theory this curve should follow the ideal gas law. Where I think a lot of people have issues is that they think the air temperature they read at the throttle body is the same temperature as the air that is going into the cylinder. There is a chance it could be, but more than likely you are going to see some heat rise between the two. I think I actually got lucky with this one, because I have my MAT sensor in the intake runner right above the intake valve (I don't have the six pack top plate, but same base):

I'm using an open element style sensor that changes temps pretty quick due to low thermal mass:

You can actually watch my MAT values rise and fall with the TPS signal while I'm cruising down the highway in this datalog:

The yellow trace in my TPS and the white trace on the bottom chart is my MAT. It goes from ~80 degrees on the left to 90 degrees or so at the peaks in the 20 seconds I rolled off the throttle, then it starts dropping back down as I get back into it. If I sit at a stoplight or in a drive thru or something I can see my MAT values hit 180 on a hot day, and I have a hood scoop and 360 degree air cleaner with flow through lid (though it's not sealed to the scoop, something I'm looking at fixing one of these days).

So my soapbox sermon of the day to all the people that say to zero the air density chart when first tuning your car is "don't, at least not at first". The chart is there for a reason, and the ambient temperature is only vaguely related to the actual air temperatures inside your engine. In my experience on my setup (aluminum intake, hood scoop, my particular air filter, etc.), the MAT values I see at my intake runner while cruising down the highway tend to be ~20 degrees warmer than the ambient air at minimum. With more intake vacuum (throttle closed), they tend to rise because there is less mass in the intake, so it takes less energy to increase the temperature. That's not saying you can't tweak this table, but do not zero it out. What you should probably be adjusting is actually the MAT/CLT correction table. That one more clearly describes the issue going on if you read the tool tip. It basically says as air flow goes down, assume the temperature of the air entering the cylinder is closer to the coolant temp than the ambient temp. Conversely, the more airflow you have, the closer it would be to ambient. I see this first hand on my car and am planning to try to play with this table in the near future. I have an issue where my car tends to idle lean, but runs normally once I start driving. I've tried adjusting the VE table to richen up my idle area, but then it's way too rich on first startup, so it's a never ending fight. I'm pretty sure this table is the solution to that, I just need to figure out the values. Okay, rant over.

HP Tuners has similar tables for reference:

I think they are a little less clear on the surface, but I have tried to use some of them on my setup. They split it up into two tables each for CLT and IAT sensors. Each one gets a table for RPM vs MAP and a table for a multiplier based on the direct sensor reading. The IAT table is all ones for RPM/MAP, so it scales purely off of the IAT values. This would be similar to the air density correction curve in the MS. In fact, I actually had these values in my car before today and may go back to them, depending on how my tune adjusts to different weather. I think their values may have some of the heat transfer of the intake built in and may account for the IAT positioning. They used a plastic intake with a sensor around the throttle body I believe, compared to my aluminum intake with a sensor in the runner, so time will tell. The coolant table is interesting because it does care about RPM and MAP, as well as scaling off of the CLT sensor on top of it. The CLT scaling table we'll look at later when we get to the startup/warmup section of MS tuning as I believe that is effectively what these values are. The RPM/MAP table for coolant I believe has a parallel in the MS MAT/CLT correction table, so I have some work to do to see if I can translate those values over. Interesting that table ends at such a low rpm though.

Probably enough for one night of rambling...

 

[jos51700]

I have an SCT for the Magnum 5.9 in my Dart. I'm not afraid of tuning the fuel but spark scares me. I'm afraid I'm going to blow it up by pushing the spark too far.

 

[Map63Vette]

I have an SCT for the Magnum 5.9 in my Dart. I'm not afraid of tuning the fuel but spark scares me. I'm afraid I'm going to blow it up by pushing the spark too far.

Definitely in the same boat there. I was hesitant to stray too much from anything already out there until I got the knock sensors in the car. Granted, you still have to configure the sensors, and mine might not be configured sensitive enough to catch the first knock, but at least it's some kind of safety blanket.

 

[jos51700]

Definitely in the same boat there. I was hesitant to stray too much from anything already out there until I got the knock sensors in the car. Granted, you still have to configure the sensors, and mine might not be configured sensitive enough to catch the first knock, but at least it's some kind of safety blanket.

How do you add that if you're using the Magnum EFI that doesn't have that capability?

 

[Map63Vette]

How do you add that if you're using the Magnum EFI that doesn't have that capability?

The Megasquirt has the knock capability with an add-on module, I haven't touched any factory Magnum stuff. I was more just saying I was hesitant to add any timing to my Megasquirt setup for the same reasons of not wanting to hurt any parts. Fuel is fairly forgiving to mess with unless you get pretty far out there. Spark can be a lot touchier.

 

[Dartsun]

I've got a 1979 Volvo GT that I've had tore apart for awhile. Got a micro squirt for it and lost interest. Reading your threads gives me some motivation. My dogs like to use my Volvo oddly.

 

[Map63Vette]

I've got a 1979 Volvo GT that I've had tore apart for awhile. Got a micro squirt for it and lost interest. Reading your threads gives me some motivation. My dogs like to use my Volvo oddly.
View attachment 1716440771

I toyed with the idea of Microsquirting a motorcycle some time ago. I had a 96 Honda Magna and I know the Interceptor used a very similar engine, but with fuel injection. I debated trying to pull the whole system off that bike to adapt to mine, and also thought about just pulling the throttle body and injector setup and doing the computer part myself with the Microsquirt. Someone swapped the whole motor over to their Magna, but went back to carbs in the process, which I never quite understood.

My 71 Vette also kind of tempts me to go to some form of injection, but I kind of like keeping one carb in the house for the fun of it. That car is more my "vintage" car that I try to keep mostly stock. The Dart is the experimental car I play with and try things on.

 

[Map63Vette]

Alright, I guess it's time for the next tab, fuel settings. This is probably the potatoes of the meat and potatoes of tuning. There are some fairly important settings in here and this is largely where I found the difference between a tune that runs "good" and one that runs "smoothly".
First up, we need to characterize our injectors. When dealing with a speed density tune, these are some of the more important numbers you can find. To reiterate something I heard Greg Banish say in an interview, any errors that you make at this point are just going to get baked in and compound things down the road. Don't let that scare you, it's not like your engine won't run or will immediate blow up if you get things wrong. It's more that you might end up chasing your tail trying to figure out why your tune feels like it changes day to day if you get things way off here. In reality, this is the "fine tuning" portion that I found makes my engine feel much smoother and more OEM like. The biggest problem is finding good data for your injectors. OEM stuff can be hard to find, aftermarket maybe a little easier, though you may need to be wary of any values you get. If you're really interested, the Minnoxide interview with Greg Banish on YouTube is a really interesting watch.

So anyway, we're going to start off with injector dead time settings. Injectors are ultimately just little solenoids. They use electricity to produce a magnetic field to move something out of the way to allow fuel to flow. "Dead time" as Megasquirt calls it, is the time between sending a signal to an injector and when fuel actually starts flowing. This can also be called offset or a number of other things. It's effectively the amount of time it takes the pintle/disk/whatever inside in the injector to move out of the way. The voltage you run them at will affect time timing as lower voltages will produce lower magnetic fields, which causes the injectors to take longer to open. I pulled these values out of my HP Tuners file, but had to do a lot of math and head scratching to end up with what I think are the "correct" numbers for my injectors.

You have the option of setting up to four curves. Generally speaking, I think you would probably only do this if you were running staged injection (so for instance, one set of injectors that runs at low rpm and another that kicks on at high rpm). Or, if you are running dual fuel and have one set that runs your pump gas stuff and another that runs your methanol or something like that. Generally speaking, most people will only need to set one. I'm using the MS3X, so I have full sequential and one injector per cylinder. You can also set these up to vary with fuel pressure (I just learned that clicking through options), but that would most likely be used for a boosted setup where your fuel pressure might increase with boost. I don't know enough about it, so I'm sticking with voltage control. The curve you see is how many milliseconds it takes an injector to start flowing fuel after being commanded to open at any given voltage. This is where the pain/fun begins.

I believe the Megasquirt characterizes injectors in a way similar to GM. Dodge, on the other hand, seems to have a different way of characterizing them. In GM land, 0ms is when the command to open is given. In Dodge land, 0ms is when the injector first start flowing fuel. So the values in HP Tuners can't be directly entered into the table/curve here. Here is the HP Tuners page with offset (dead time) values:

If you compare those numbers to GM ones of a similar size, you'll see that they are quite large, like almost double what you might normally see (note, the MS also takes values in microseconds, not milliseconds, so take all the numbers here are multiply by 1000). The other table you need to make sense of this is the injector PW vs fuel mass table:

This is the really important one that characterizes how much fuel the injector flows based on the commanded pulse width. Graphed out, it looks something like this:

Pretty straight line right? Well...kinda. The slope of this apparent straight line is typically what I'd call the injector size. In my case, this works out to be ~29.94 lbs/hr. However, if we zoom waaaaay in at the very start, we see the interesting part:

See that kink at the start? This is what gave me several hours of confusion trying to understand. The problem is, the MS code wants to assume that injectors are always linear, so it starts at 0 and draws a straight at the slope we established in the last graph:

That's a problem, because that means we're actually injecting more fuel than the MS thinks we are. What we need to do is include the offset value as well to get a more complete picture of a full injection event from the start of the command to the end of the injection event. Let's assume we're running at 14v and pick that offset off the table. That gives us something that looks more like this:

Now we've gone the other way and the MS thinks we're injecting more fuel than we actually are. What we need to do now is add offset to the red line so that it lines up as close as we can get it with the blue line:

Where this red line crosses the X axis is the offset value that we need to use for the MS, which is quite a bit different than where the blue line crosses the X axis, which is the offset value that Dodge uses in HP Tuners. In this case, the offset is ~0.75ms, or 750 on the MS table/curve, compared to the 1.272 or 1272 value that HP Tuners has in the table. I learned the hard way that just because two things might be called the same thing in tunes, doesn't mean they are measured the same way. I tried using the values straight from HP Tuners on a tune and I could barely even get my car to start, let alone idle.

So it's also worth noting that you could have similar problems even if you buy your injectors aftermarket and they provide numbers. It's probably worth talking to your supplier and asking what system or computer those numbers were measured for. Some will say injector drivers inside the computer itself will also matter (the actual transistors switching the current), though I haven't found a lot of information either way to back up that theory. Fortunately, the rest of the settings are a little more straightforward.

 

[Map63Vette]

Next up is some more nuanced stuff with injectors, though this one is maybe less important depending on your setup. From what we could see in the last post, when the injector first opens, it doesn't want to flow linearly (at least these injectors don't, maybe there are some out there that are closer). You'll notice though, that by ~2ms or so, the line is pretty straight and follows the linear curve. What this table does is scale the pulsewidths to adjust for that nonlinear region:

So, do you need to do anything with this? It will depend on your injector sizes. I put in the values because I spent a lot of time in Excel making those graphs and trying to understand how Dodge characterized things vs how the Megasquirt does it, but the reality is that my injectors almost never run under 2ms in practice. At idle or cruising down the highway, I tend to be in the 3-5ms range, so this was all just "for funsies" for me. However, if you have really big injectors, like for a boosted application maybe, you could very well find yourself in this region of flow. What this curve does is basically just overwrites a calculated pulsewidth from an expected linear flow into the pulsewidth required to get the actual amount of fuel desired. Going back to our previous graph, you can think of it as drawing a line horizontally from the linear flow line over to the actual flow line and checking the difference between the injector times.

So for example, say the Megasquirt calculates that we need .001 grams of fuel for a particular cycle. Based on the linear flow rate of the injectors, that would correlate to a pulse width of ~1ms. However, in reality, the injector hasn't even started flowing fuel yet at that pulse width. So you keep following the line over to where it intersects the actual fuel delivered line and then go down there to see the actual pulse width required to deliver 0.001g of fuel:

So the thing to remember is the red line is expected/calculated fuel, and the blue line is actual measured fuel delivered. In the MS table/curve, you would say for an original pulse width of 1ms (the "original" fuel value), instead use the "new" fuel value of ~1.35ms. It took me a while to figure out how to interpret the "original" vs "new" pulse width idea, but I'm fairly certain this is it. Does it really matter for me? Probably not, but it makes me feel good that I think I have the correct values in there regardless.

Similar story here to the previous one where you can set different values for different injectors. So if you went back to the setup where you might have injectors for pump gas and different ones for a race fuel, you can set them individally here. Neat stuff, though probably something very few people will ever need to touch unless you are running a more extreme engine setup.

 

[Map63Vette]

There's some other fun stuff you can do in the fuel menus, but most of it is beyond the scope of my build:

Injector timing is something I could play with one of these days, and I have tried a very small amount, but without something like a dyno where I can really sit and test values in controlled conditions, I don't think this is something I'm going to be able to tune effectively. What it does is time when the injector starts (or finishes, depends on your settings) injecting fuel relative to the intake valve opening. The general theory they use by having 360 degrees in all the cells is that you want to spray fuel on the back of a hot intake valve before it opens to allow for best vaporization. You could get clever and try to inject when the valve is open to spray into the cylinder when the airflow is higher, but head design and injector angles and spray patterns can all affect that. Also, as you get to higher rpm you have less time to inject and may not have time to finish before the valve opens, so it likely only as useful at lower rpms.

Staged injection goes back to the idea of running two sets of injectors. Typically you'd probably switch over at an rpm set point, though there might be other settings you could use. I've never messed with it, so don't know enough to be useful.

Fuel sensor settings I have debated playing with one day just for the fun of it. This is where you can set up a flex fuel sensor (E85) or temp sensor. I've debated putting a sensor in my car just for the novelty of being able to run E85 if I wanted, but I might be injector limited. Neat stuff though and maybe a "down the road" project if I'm really bored.

 

[Map63Vette]

Now we're getting into the fun stuff, which is actual fuel control. The menu starts out with EGO control, though when actually tuning, it's debatable whether you should leave this on or off to begin with. It's nice as a safety blanket, but at the same time the EGO correction could be yanking your tune around while you're trying to change things manually, so just something to be careful of. Like I mentioned earlier in this thread, ideally you should be able to run your tune with EGO completely off. The goal of a good tune is to be able to run "proactively" based on the sensors at the "front" of the engine, not reactively based on what's coming out the back. This is also where I implemented my OEM style "open" vs "closed" loop tuning.

The main EGO control window is where you'll set what kind of algorithm you want to run to adjust fueling based on an O2 sensor. The options here are "simple", "PID", and "no correction" (off basically). The simple algorithm is just that. It's probably designed to be used more with narrowband sensors, but works with wideband sensors as well. It basically looks at your O2 sensor and asks "am I rich or lean?". If it's rich, it will lean it out by the step size value and check again after your delay (either IGN events or a time delay). If it's lean, it will richen the mixture by the step size. So what you'll tend to see in your datalogs are stairsteps as the O2 feedback adds or pull fuel from your mixture. It's not crazy obvious here due to my smaller step size, but you can kind of see it in this trace (white is EGO correction, red is measaured AFR):

The PID setting will instead use a PID feedback algorithm to estimate how much to lean or richen the mixture by based on the measured AFR vs the target AFR. So this would give much quicker adjustments to try to pull things back to your target the further off you are, instead of having to "step" it's way back. I used to have mine set up this way, but went back to simple because I felt I needed to tune my main VE table better and not rely on EGO feedback as much. I'll probably try going back to it in the future as it's one of the benefits of a wideband sensor. Knowing how far off you are from you target can help fix a problem much quicker if one were to arise.

The other important setting here for me is the controller authority. This limits how much you EGO feedback is allowed to change the mixture. This kind of acts like a failsafe in case your sensor loses its mind. Ideally you want this fairly low as your VE table should be accurate enough that you shouldn't be relying on your EGO feedback to get things in line. I started with 10% and have turned it down to 5% since then. I'll watch my datalogs and live gauges from time to time to see what the live correction is to get an idea of how far off my VE table might be. Given that most OEM injectors also operate in a 5-7% kind of tolerance from what I've heard, this also feels fairly reasonable. 10% is likely the safer option though.

Futher down in the settings you can configure when you want EGO correction to be active. Typically, you would want to wait for your engine to be warm (and the sensor for that matter), and some people might want to disable it at high or low rpm based on their preferences. I have mine disable at idle because my AFRs tend to swing around a bit with my cam. You can also set up multiple sensors, like one for each cylinder if you were so included and well funded. At the moment I'm only running a single one on a single bank. I'd like to get one on my other bank some day, but it hasn't been a priority for me.

The AFR tables themselves are where you finally start commanding some actual fuel into the engine. These go way back to the original setup settings where we chose to "incorporate AFR target". If you have that value selected, then the values your put in these tables are the AFR you are telling the MS to try to run your engine at. My first table is set up for cruising and is basically 14.7 everywhere. I richen it up just a bit at the high end of load to be safer, but you could effectively consider this equivalent to an engine running in "closed loop" in the OEM world. My second table is the "WOT" table, or "open loop" to some degree. Technically speaking my car is still closed loop all the time because I have a wideband sensor and am always using the feedback, but this table is only active when my TPS is greater than 85% (more on setting that up later).

Strictly speaking, I don't believe HP Tuners has a "closed loop" AFR target table. However, they do have a "power enrichment" table that is what I made my "WOT" table from:

Again, Dodge is weird and uses 1 / AFR instead of the AFR value directly, so the numbers look weird, but work out to be what is in my table. I'm not 100% certain how this table is used in the OEM setup either. My assumption from the little I can guess based on available settings in HP Tuners is that once the pedal input exceeds the WOT threshold, this table goes into effect. What I'm less sure about is what throttle percentage that actually relates to. They talk in voltage because it's drive by wire (or could still be TPS, but regardless), and I'm not sure what their limits are. Conventional wisdom might assume 5v is 100%, but 3.196v would only be ~64%, which seems low to me and I know most TPS sensors calibrate far less than that. I think several are more like 1.5-3.5v range in actual use, which would make 3.196 more like 90% throttle, which sounds more realistic.

Lastly, the MS does have a neat AFR safety system that will kill spark and fuel if your measured AFR is too far off your target AFR based on the table values you set. This is likely much more useful in boosted applications where things can go south in a hurry. I haven't messed with it because my engine is still pretty mild in the grand scheme of things.

 

[Map63Vette]

And now the main event, the VE table:

*cue angelic choir sounds*

In short, this table is more or less the mathematical model of airflow through your engine. VE stands for "volumetric efficiency" and relates to how much air gets pulled into the cylinder relative to the actual volume of a cylinder. So if you have a cylinder that's 1L in size and you have 100% VE, that cylinder has 1L of air in it at the pressure on the Y axis of the graph before compression starts. It's probably more nuanced than this, but that's a pretty general simple way to think about it. This is where you'll likely spend most of your tuning life. This table should generally also resemble the torque curve of your engine. The same table exists in HP Tuners:

Dodge also likes being silly by inverting the Y axis compared to MS, but that's neither here nor there. I searched high and low trying to find these values before I downloaded HP Tuners and got lucky that my engine was in their sample files. However, this one was also unfortunately not as straightforward to copy directly to MS. In my case, I think it was largely because of my engine changes though (headers, cam, intake). If I had a stock engine, I bet these would have copied over fairly well to give me a good place to start. I still used them as the basis for my tune and have let autotune do some work to tweak things as these should at least get me in the ballpark. You can see where the values peak around 4300-4500 rpm here, which corresponds to the torque peak of the engine on the dyno chart:

You can also see that other tiny little hump around 2500 on the curve reflected in the VE table.

However, with great power comes great opportunity to mess things up as well. The VE table can disguise a lot of things and can be used in a lot of different ways that may or may not be a good idea. For instance, you could in theory bake some amount of "accelerator pump" into it if you wanted by artificially increasing the values at low rpm and high load. Or, if you have the incorrect size injectors, you can scale the VE table to make up for it. I've certainly been guilty of the latter of those two, though it was partially because I didn't know my actual injector specs. It all comes down to the fueling equation that the MS uses. In simple form, it's the following:

PW = required fuel * VE * load * MAT correction * CLT correction * EGO correction + acceleration enrichment + dead time

That's a lot of different knobs you can tweak that will all kind of do the same thing in some regards. The goal in my book is to avoid the "easy" road of using one to cover for the other as it usually will cause some other knock-on effect down the road. The VE table is the core of your engine model, so ideally you want it to be as accurate and unrelated to anything but airflow as you can get.

The last setting on the fuel tab (that I have at least) has to do with controlling your fuel pump. My setup is pretty simple as I just have an on/off pump that is manifold referenced for pressure, so the fuel pressure relative to the intake is always the same (in theory). This makes the fueling calculation a little easier. There are lot of other fun things you can play with in here like individual cylinder trims (like if you have a lean or rich cylinder because of bad air distribution or something) and some other fueling corrections for things like fuel temp (which the OEM computer does). I don't have a fuel temp sensor (yet at least), though I do have a pressure sensor, so I might play with these down the road, especially as I seem to have problems at hot idle with my mixture leaning out that other correction factors haven't addressed yet.

There are also other settings in there for EGO control like authority tables where you can adjust how much it can change the mixture by based on where on the map you are instead of a fixed value. So for instance, you could let it adjust by 10% at idle, but only 5% at cruise or something like that. I haven't gotten that far into it yet as generally speaking I want EGO to be the last thing I tune, not the first.

So that's probably enough ranting for my second session. Next up will be the meat of the meat and potatoes, ignition settings.

 

[racerjoe]

This is some really great info. Thanks for sharing.

Question, when tuning the open loop idle, did you find your idle RPM would vary during normal driving?