I use the progression ignition electronic distributor. You just hook the CC wires to the coil, then the constant power and ground wires. That's it!
Carb Cheater - What Say Yee?
- Thread starter Kmrumedy
- Start date
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That’s just not true. There is nothing static about a carburetor. If that’s what he really said then he is sadly mistaken.
The OEM’s spent millions and millions of dollars developing fuel and timing curves back in the day (yes, fuel and timing go hand in hand) for cars that had carbs and were driven 365 days a year and went from coast to coast and border to border.
At the very extremes the engine might have some slight issues but other than that, no one in 1970 or 1965 or any era of a modern carb was fouling plugs, rolling coal (yes, I’ve seen guys blowing black smoke out of the tail pipes on carb’d engines) and all the rest of it.
The issue is people buy an aftermarket “universal” fit “performance” carb, bolt it on and then want to go out and rotate the earth and get 50 mpg. Those carbs out of the box are hideously fat. Thats so the guy trying to run the carb on his 650 hp engine doesn’t get too far out of line (the carb will still be fat for that but it won’t be screaming lean) and the 350 hp engine guy gets stuck with a nasty, pig fat rich carb.
In neither scenario is the carb correct for the application. That’s why “universal fit” means it universally fits nothing.
And because the aftermarket has spent decades lying to people, telling them carb tuning is some black art voodoo magic **** just to keep the public ignorant so they could corner the market is a magnificent sin.
They are not complicated, but tuning one can be complicated. They are technical but the average guy who is doing this and has a basic understanding of pressure differential can understand the technical side of a carb well enough to tune one to almost perfection.
There is nothing static about a carb.
I have never really paid attention to these until I watched a video about it this morning. I am intrigued by it. More than anything, I am keen on the data logging part of it. I will say though, it might help my efficiency some since I drag race and Street/Highway drive my car alot. I am not a carb tuning expert, more of an enthusiast. I find when I tune for the street, my track tune suffers, and and my track tune isn't ideal for the street. I currently gave a 750 VS Holley that I was contemplating using on the street and swapping back to my 750 QFT double pumper for Racing. Maybe with this, I could avoid this minor screw around.
Cley
Cley
Im not sure why one tune makes the other type of driving suffer. I find this very interesting.
Can you give an example of the track tune and the street tune?
Well, it's possible I am going about it in the wrong way, or maybe my hardware isn't quite what I need, but I always try to keep my jetting as close to even from front to back. That is, the size of the primary jets and the power valve circuit restrictors is about equal to the secondary jet, as I have no secondary power valve.
When I get it to cruise the highway at a decent 13.5 to 14 where everything seems the nicest for smooth running, mileage and overall healthy sounding engine, it will be lean at WOT, say after 660' on track. I have confirmed this by looking at the plugs, not just relying on my AFR gauge. Now, I can increase secondary jet to make up for that, but then I have quite a bit more jet in the back than the front.
This may be able to be solved with air bleeds etc, I have not done anything with that yet.
Cley
When I get it to cruise the highway at a decent 13.5 to 14 where everything seems the nicest for smooth running, mileage and overall healthy sounding engine, it will be lean at WOT, say after 660' on track. I have confirmed this by looking at the plugs, not just relying on my AFR gauge. Now, I can increase secondary jet to make up for that, but then I have quite a bit more jet in the back than the front.
This may be able to be solved with air bleeds etc, I have not done anything with that yet.
Cley
MOPAROFFICIAL
If it has tits, it's a liabilititty.
That's a venturi difference. Smaller hole, faster air...faster air=better mixing.
Through carb, nothing but a plus. Through the head, nothing but a slow burning cyl wall washing detonation sensitive pos lol
MOPAROFFICIAL
If it has tits, it's a liabilititty.
Unless you want gas on your hands, stink in your car... this is a great add on for traveling through diff elevations.
The alternative is bringing gloves, a fuel catcher, rag, jets and a couple tools.. pulling over and changing jets so you A. Don't start running hot and B. Get horrible mpg as you go from say 500 ft.. to 3000ft...
Lastly you will need a couple freezer bags to put the gloves in so your car doesn't smell like gas.. and youre not littering...unless of course you pull over at turnout thay has water and trash cans.
Just my take.
The alternative is bringing gloves, a fuel catcher, rag, jets and a couple tools.. pulling over and changing jets so you A. Don't start running hot and B. Get horrible mpg as you go from say 500 ft.. to 3000ft...
Lastly you will need a couple freezer bags to put the gloves in so your car doesn't smell like gas.. and youre not littering...unless of course you pull over at turnout thay has water and trash cans.
Just my take.
It’s too involved to get into here, but unless you are on a dyno and you can measure the amount of fuel going to each bowl there is no way of knowing if each half of the carb is adding the same amount of fuel to the engine.
If you are driving on the street I suggest you tune for your cruise AFR first. You really need a vacuum gauge hooked up when you do it but it’s not a must do thing. I plug the power valve off and drive the car and tune the primary main jet for the best cruise, which IMO is as lean as you can get it without a lean miss on relatively flat ground. Once you find that, I go up two jet numbers and leave it alone. I never change the primary main jet unless I want to go back and work on my cruise tuning and then I take the power valve back out and test as above.
Once you get your cruise where you want it, then you can start working on transition and WOT but squaring away your transitions is too much to deal with here.
For WOT you will be tuning with only the PVCR and the secondary main jets. I start with a secondary main jet that is close to what Holley used back in the day for a carb with that Venturi and throttle blade diameter. In that case a 750 was (IIRC) 1.375 x 1.687. IIRC thats about an 80ish secondary main jet. Then I calculate the area difference between that secondary main jet and the primary main jet and that difference is how big the hole in the PVCR is to start tuning with.
Then I adjust the WOT fuel curve with the secondary MJ and the PVCR. If it’s rich at WOT and I think I need to go down say 6 jet numbers I split the difference and take half out of the secondary MJ and half out of the PVCR.
It’s tedious but it works. You also have to work on getting the power valve opening timed correctly and the vacuum gauge is invaluable getting that sorted out.
Transition tuning is by far the most complicated and time consuming but of you drive on the street it is by far the most rewarding. It takes a ton of time and the first few times you do it you are walking in blind so you have no reference point to work from.
One reason it’s so difficult and time consuming is because it involves changing air bleeds and emulsion bleeds. These little air bleed affect multiple things. Changing the main air bleed changes when the booster starts so it affects the bottom of the fuel curve (low throttle opening) and the top of the fuel curve (high throttle opening).
You can change the MAB .004 and you will change the shape of the entire fuel curve, and maybe change it in the wrong direction. Even then, you can change the MAB and get the effect you want but you still may need to change the main jet to get the full benefit of the change.
That’s why I said it’s too complicated to get into here, because when you get that far into tuning ignition timing plays a part of it.
It’s like juggling seven or eight balls and not one of them is the same size and weight. When you get a carb dialed in the reward is far greater than the effort to get there.
Edit: see post 57. Thats how I do it. I bring all my tools with me and a catch can to get the fuel out of the bowls and I make a change in a parking lot or whatever. And then I keep going until I get what I want.
Tony ( 70aarcuda ) did a track test with a 3310 VS and 750 DP, both carbs were tuned for his combo. What he found was virtually no difference in ET or MPH at the track.
I actually plan to do the same thing at some point. Just for fun! I love experimenting with this stuff. That is why the carb chrater's data logging intrigues me!
Cley
How much data logging can it do? If it can log MAP that is a MASSIVE bonus.
Perhaps you should look at his statement differently. A carb is tuned to a static environment such as temperature, altitude, etc. Runs great there until the environment changes too much and the engine runs less efficiently due to those environmental changes. In that sense it *is* a static device that cannot change its internal settings for the changing environment.
Right, I thought it might be different because the FBO box is more or less an aftermarket version of the original mopar electronic ignition boxes that get mounted to the firewall.
What he means by this is you can't actively adjust the fuel trim while you're behind the wheel. Changing elevations (if not just passing through) you have to hop out, open the hood, readjust etc. AFRs do bounce wildly all the time while you're driving and that's what the auto tune feature covers.
Maybe that’s what he means but if the quote was what he said I don’t see how it means that.
I know the elevation thing gets brought up. A lot. A carb is a pressure differential device. When the elevation changes so does the pressure. At sea level there is 14.7 psi pushing down on the fuel in the fuel bowls through the vent. As you go up in elevation the pressure on the fuel in the bowls has less pressure on it so the entire fuel curve is leaner.
I know one thing I learned that was hard to get my head around is the farther out of tune the carb is at any given barometer the less the carb can compensate for any given change.
Im not sure of why that is, but it is. If you live in Colorado and your tune is out of tune there, as you start dropping in elevation the carb won’t compensate for that change as well as it would if the carb were tuned correctly to start with.
I remember a while ago, probably in the early 2000’s Warren Johnson said in a magazine article that they could go from Denver (where the corrected density altitude can be as high as 10’000 feet!) to Sonoma California a week later (almost never going above 2000 feet even on a pretty hot day) and he never changed a jet!
I thought he was kidding so years later I asked around and found out he was telling the truth. They may change an air bleed or emulsion but that was it.
A carb can compensate for a very wide set of conditions if it starts out close to what it should be. Another crazy thing Ive leaned on the dyno is when the engine is rich like in the low 12’s for a/f ratio or so, the cylinder to cylinder distribution can be horrible. As you start getting the fuel curve back in shape 90% of those distribution issue clean themselves up.
When there is excess fuel in the manifold it will find its way to the least path of resistance and then that cylinder gets dead rich.
That’s a big deal. If for no other reason that would be a reason to get one. That is a big tuning aid.
It's not just air pressure, but also the oxygen content in the air as well. Higher up you go, there's just less oxygen. The carb might be able to compensate such that it'll run acceptably. But hook up a wideband and watch that AFR bouncing all over the place even on a regular sunday cruise, that's where the CC steps in and lets you get maximum efficiency without worrying about the electronics failing - if that does happen, it just becomes a regular carb.
Luke does sell a carb cheater lite kit, which is just the gauge kit, no auto tune feature. Even just that alone is ridiculously great value for money. Plus if you do decide to try out the carb cheater, you can buy the bits later to upgrade it.
Luke does sell a carb cheater lite kit, which is just the gauge kit, no auto tune feature. Even just that alone is ridiculously great value for money. Plus if you do decide to try out the carb cheater, you can buy the bits later to upgrade it.
That is true. No matter what you do, when you go up in elevation and you have less oxygen you will make less power. Even with EFI.
And that's where EFI shines - the ability to react and adjust to ever changing conditions on the road. The sensors in this kit allow the carb to behave closer to an EFI system.
The ideal setup with CC is to tune the carb to run a bit rich, then let the auto tune function add air as needed, since it can only add air and not fuel. You could probably go one step further, and use the AFR and vacuum gauges to set a base/backup tune for when auto-tune is disabled, mark it with a scribe on the mixture screws or something. Then set another, richer, tune to make full use of auto-tune. Then in the event it stops working for whatever reason, you can just quickly fall back to the base/backup tune.
The ideal setup with CC is to tune the carb to run a bit rich, then let the auto tune function add air as needed, since it can only add air and not fuel. You could probably go one step further, and use the AFR and vacuum gauges to set a base/backup tune for when auto-tune is disabled, mark it with a scribe on the mixture screws or something. Then set another, richer, tune to make full use of auto-tune. Then in the event it stops working for whatever reason, you can just quickly fall back to the base/backup tune.
Can you log AFR as well?
See my previous post with the screenshot - it logs engine RPM, MAP (or rather, vacuum), AFR and GPS vehicle speed if you installed the GPS module
edit: that pic might've been a bit too small, bigger version of the same pic from their site:
edit: that pic might've been a bit too small, bigger version of the same pic from their site:
Is that your actual log? If I’m reading it correctly (it is far easier to read in the second shot) it looks like at a cruise your AFR is moving from a bit over 15:1 all the way down to around 12.5:1 or so.
If that’s correct and you were on a relatively flat road my first assumption would be that carb has too much emulsion. Too much emulsion causes “slugging”, which means the smaller air bubbles introduced into the fuel in the main well coalesce and make less, bigger bubbles. When the bubbles get big enough you end up with a big slug of air, and then a big slug of fuel. And the cycle continues.
It also means the main air bleed is on the big side. That’s what I see just looking at that very small sample graph.
This example is the perfect example of why data logging is so valuable when trying to tune anything. It’s one thing to have an AFR meter and a vacuum gauge you can look at but it’s a whole other thing when you can log it and look at the data after the fact.
I forgot to ask if that can accept a TPS? If you can and you can log it you can tune to a gnats arse.
goldduster318
Overzealous Car Modifier
It's damn good as he was able to drive a 302 Ford with a 4-speed with a lawn mower carb which also doesn't have an accellerator pump on the entirety of power tour.
Simply, if it's even remotely close it will push it to be really good.
The issue is that far too many people (and unfortunately the majority of people scoffing at it, that would actually benefit greatly from it) think it's a substitute for a poorly tuned carb. Luke can't stress it enough, and neither can I; the CC is an augment – not a replacement – for carb tuning. It has the tools needed to tune a carb really well, far more precise than any butt dyno or auditory feedback ever could. Imagine you've had blurry vision all your life and you put on glasses for the first time.
And it does all this for a fraction of the cost of the dedicated tools that would go into reading and logging all this.
And it does all this for a fraction of the cost of the dedicated tools that would go into reading and logging all this.
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