Megasquirt values for launch and traction control on 3G swap

[Map63Vette]

As the thread title suggests, I'm looking for some feedback on what people might be using for traction and launch control on their setups. I know Goody had a thread a while back showing the differences on a Cuda 3G swap, but curious if anyone else has played with it at all. I'm mostly just looking for some ideas of what kind of rpm to set for launch control and potential timing reduction curves for traction control. I wired in a potentiometer on my clutch pedal over the weekend so I could tune where the launch control releases, but I'm not sure what sort of rpm makes sense to set it at. I'm guessing it will probably vary pretty widely with engine and tire setups, but figured I'd ask anyway and see what people were having luck with. I tried it out at 3500 on a backroad with my ET Street tires and lit them up fairly well, but I realize it's also not a prepped racing surface. Didn't know if it even made sense to try to launch it that hard or not with my fairly mild build. Another setting I wasn't sure about was the soft limit retard value. It talks about timing reduction, but doesn't really give any advice on common settings. Guessing maybe this is more useful for turbo setups to provide something like anti-lag or building boost for launch, but also curious if anyone has played with different values on an NA engine.

Along those lines, I'm still not sure my traction control is actually working. Need to try to get some better logs one of these days, but when lighting the tires up during my launch test I never noticed any kind of timing cut to bring things back into line. Guessing maybe one of my trigger values is just too high, but it's been hard to reliably cause slip with my street slicks on. That being said, I'd be curious to see what people are using for the reactions settings. Currently running slip% trigger at 10%, but otherwise just have the stock reactions to try to limit power. Only timing retard at the moment, ignition cut and fuel changes are all zeroed out.

 

[DionR]

Guessing @racerjoe hasn't seen the thread yet?

I don't have anything to add, but would like to see some pictures and more info on your clutch switch setup.

 

[RustyRatRod]

"Megasquirt". I've always thought that sounded like a bad **** movie.

 

[racerjoe]

As the thread title suggests, I'm looking for some feedback on what people might be using for traction and launch control on their setups. I know Goody had a thread a while back showing the differences on a Cuda 3G swap, but curious if anyone else has played with it at all. I'm mostly just looking for some ideas of what kind of rpm to set for launch control and potential timing reduction curves for traction control. I wired in a potentiometer on my clutch pedal over the weekend so I could tune where the launch control releases, but I'm not sure what sort of rpm makes sense to set it at. I'm guessing it will probably vary pretty widely with engine and tire setups, but figured I'd ask anyway and see what people were having luck with. I tried it out at 3500 on a backroad with my ET Street tires and lit them up fairly well, but I realize it's also not a prepped racing surface. Didn't know if it even made sense to try to launch it that hard or not with my fairly mild build. Another setting I wasn't sure about was the soft limit retard value. It talks about timing reduction, but doesn't really give any advice on common settings. Guessing maybe this is more useful for turbo setups to provide something like anti-lag or building boost for launch, but also curious if anyone has played with different values on an NA engine.

Along those lines, I'm still not sure my traction control is actually working. Need to try to get some better logs one of these days, but when lighting the tires up during my launch test I never noticed any kind of timing cut to bring things back into line. Guessing maybe one of my trigger values is just too high, but it's been hard to reliably cause slip with my street slicks on. That being said, I'd be curious to see what people are using for the reactions settings. Currently running slip% trigger at 10%, but otherwise just have the stock reactions to try to limit power. Only timing retard at the moment, ignition cut and fuel changes are all zeroed out.

What are you using for your wheel speeds? Lug studs, pinion sensor, etc? I'm assuming you made sure your front and rear wheel speeds match? I did the math for circumference as a start, then put the two speeds on the dashboard to dial them in to match. If you are running ET streets, you probably aren't going to get enough tire spin quick enough, unless you go out after some rain. Start with a low sensitivity and a very high reaction. You will have to data log to see if its doing anything. If you have an N/A motor you likely won't get quickly changing wheel speed, unless you are on wet pavement. My problem was the standing start when I was autocrossing. As it turns out, I had some really crappy tires, which led me to adding traction control. I have much better tires now so it isn't as much of a problem.
I don't have launch control, but I think you will need to figure that out on your own and decide how hard you want to be on parts. There's no way I'm doing a 3500RPM clutch dump with slicks on my car!

 

[Map63Vette]

Guessing @racerjoe hasn't seen the thread yet?

I don't have anything to add, but would like to see some pictures and more info on your clutch switch setup.

I'll try to get a picture the next time I pull the cover off to work on things to show it actually installed, but the short version is I have a potentiometer attached to the pedal with a string and a spring on the other end to keep tension on the setup. It's a similar idea to a string pot for measuring distances, just a bit more homemade and short throw.

Here's a nice 3d model I put together when I printed the pieces mixed with horrible MS paint to fill in the blanks, lol:

I had the pot left over from a motion platform I built for racing in VR. It's hall effect, not a wiper, so it doesn't drag or wear out over time and has really clean output. My clutch master has a 1.2" stroke, so I designed the arm on the pot to match that and targeted ~120 of rotation over that travel (the pot is only a 180 deg variety). Currently I appear to only use about 75% of the travel before my pedal hits the floor according to TunerStudio at least. The whole idea behind this was I could set an virtual variable in the computer that would toggle on and off based on the voltage coming from the potentiometer. That way I can tune when I want the switch to "open" or "close" electronically instead of having to constantly tweak a bracket for a physical switch. I still need to do some more logging with that as well to see where my clutch is starting to engage/disengage maybe before I even set a launch rpm.

What are you using for your wheel speeds? Lug studs, pinion sensor, etc? I'm assuming you made sure your front and rear wheel speeds match? I did the math for circumference as a start, then put the two speeds on the dashboard to dial them in to match. If you are running ET streets, you probably aren't going to get enough tire spin quick enough, unless you go out after some rain. Start with a low sensitivity and a very high reaction. You will have to data log to see if its doing anything. If you have an N/A motor you likely won't get quickly changing wheel speed, unless you are on wet pavement. My problem was the standing start when I was autocrossing. As it turns out, I had some really crappy tires, which led me to adding traction control. I have much better tires now so it isn't as much of a problem.
I don't have launch control, but I think you will need to figure that out on your own and decide how hard you want to be on parts. There's no way I'm doing a 3500RPM clutch dump with slicks on my car!

Front wheel speed is reading the heads of the lugs inside the rotor on the front right wheel, rear wheel speed is the factory speed sensor in the T56 trans I'm using. I checked them in TunerStudio and did some logs and they seem to agree quite well, though there is obviously a resolution issue at super low speed since the front only has 5 teeth per rotation while the transmission sensor is 10 teeth multiplied by the rear end ratio (so effectively 35.5 teeth for me). I tried putting an indicator on my digital dash for when traction control is pulling timing, but I'm not sure if it actually works or not. I know you can set an indicator light output on the computer, but I don't have the output channels to spare at the moment. I've thought about trying to fake it out by running on jackstands and manually turning the front wheel or something, but I don't think that would really work that well with all the other threshold values that the computer looks for. I think I know what you mean about the low speed issue though. My current setup has the minimum TPS at 40%, minimum MAP at 60 kpa, and minimum speed at 4.9 mph. I think I instinctively let off when the wheels start spinning, so guessing I drop under the TPS and MAP thresholds fairly quickly instead of riding it out and letting the computer pick up the slack. I think the 4.9 mph was the lowest I thought the front sensors could read smoothly from logs I'd done before. It has a bit of a stairstep effect due to the low tooth count. I'm also seriously rethinking my launch rpm. I tried looking up what factory settings Dodge uses on the cars that come with it. They typically run pretty low, like 1600 rpm or something like that, but I think a lot of them are automatics as well and may not be able to launch any higher due to converter stall speeds. I'm a stick shift so not a problem there, but I don't think my car has the suspension to actually do anything with a hard launch anyway.

 

[DionR]

I'll try to get a picture the next time I pull the cover off to work on things to show it actually installed, but the short version is I have a potentiometer attached to the pedal with a string and a spring on the other end to keep tension on the setup. It's a similar idea to a string pot for measuring distances, just a bit more homemade and short throw.

Here's a nice 3d model I put together when I printed the pieces mixed with horrible MS paint to fill in the blanks, lol:

View attachment 1716113356

I had the pot left over from a motion platform I built for racing in VR. It's hall effect, not a wiper, so it doesn't drag or wear out over time and has really clean output. My clutch master has a 1.2" stroke, so I designed the arm on the pot to match that and targeted ~120 of rotation over that travel (the pot is only a 180 deg variety). Currently I appear to only use about 75% of the travel before my pedal hits the floor according to TunerStudio at least. The whole idea behind this was I could set an virtual variable in the computer that would toggle on and off based on the voltage coming from the potentiometer. That way I can tune when I want the switch to "open" or "close" electronically instead of having to constantly tweak a bracket for a physical switch. I still need to do some more logging with that as well to see where my clutch is starting to engage/disengage maybe before I even set a launch rpm.

Thanks!

I tried looking up what factory settings Dodge uses on the cars that come with it. They typically run pretty low, like 1600 rpm or something like that, but I think a lot of them are automatics as well and may not be able to launch any higher due to converter stall speeds. I'm a stick shift so not a problem there, but I don't think my car has the suspension to actually do anything with a hard launch anyway.

I will see if the owners manual says anything, but just going off memory, pretty sure I set my launch rpm on my 6M equipped Challenger R/T to 2000 rpm. Seems like the range was 1600-3500 rpm, but it's been a lot of years.

Edit - The SRT owners manual shows a range of 1500-3500 for the A8 and 2000-4500 for the 6M. Guessing this is for the 6.4 and 6.2, they didn't differentiate. There wasn't a range indicated in the regular owner manual for the 5.7 cars. It did say the default rpm for the 6M cars is 3000 rpm, but the 8A cars just says it is a "preset factory value".

 

[Map63Vette]

Wow, guess it goes higher than I would have thought. Though I suppose maybe that's intended to cover slicks and other aftermarket goodies perhaps.

Semi unrelated, but another clutch switch idea I was originally planning was to put a pressure sensor on the clutch line. Same idea where I could tune the release point by the pressure, but I had a heck of a time trying to figure out fittings to make it work. Clutch line is -3AN which evidently is fairly uncommon at a lot of places. Thread on master was just straight SAE. I found a way to make it work, but ended up trying the pedal pot first since I had the parts handy. Pressure would have been interesting as I think it more directly measures actual clutch engagement, but I wasn't sure how linear it might be.

 

[Map63Vette]

Here's a picture of the clutch sensor as it's installed in the car. So far seems to work pretty well, but haven't really put it through much but a handful of drives at this point. The string gets pretty close to the steering column connector, but I think I can always reroute that a bit if I really have to.