Flex Fuel tuning

[bdubs]

I'm new to flex fuel tuning and trying to tune an C6 with a fuel sensor wired in. Alcohol content is reading 78% and everything seems to be working proper.

How are you guys setting up the scanner to log AFR/Lambda when the stoich values change with alcohol content? I would typically use LTFT vs MAF in the scanner, copy the percent the multiply that in the editor.


In my search for flex fuel tuning I noticed some tuners are multiplying the Stoich AFR table by 2. What is the reason for this?

[Ben Charles]

Setup the stoich table correctly covering all blends, it's your main multiplier for fuel. Based of the alcohol content it looks at the stoich table and fueling is based off that. Don't tune in AFR it will just confuse you. Target lambda

[schpenxel]

I don't understand the question.

AFR or lambda error should take into account commanded AFR...

[Higgs Boson]

he's talking about scaled tunes. bdubs, you don't need to scale your tune.

[schpenxel]

In my search for flex fuel tuning I noticed some tuners are multiplying the Stoich AFR table by 2. What is the reason for this?

Larger injectors.

You can double stoich / half injector flow rate instead of scaling tons of tables when your actual injector flow rate is beyond what you can enter into the flow rate table.. much easier to do it the double stoich way than having to scale airflow and every other table that uses airflow

[bdubs]

Setup the stoich table correctly covering all blends, it's your main multiplier for fuel. Based of the alcohol content it looks at the stoich table and fueling is based off that. Don't tune in AFR it will just confuse you. Target lambda

Ok. So if the stoich table is 14.67 to 8.97 the multipliers like PE will work and log in lambda and make adjustments to VE and MAF as normal?

Larger injectors.

You can double stoich / half injector flow rate instead of scaling tons of tables when your actual injector flow rate is beyond what you can enter into the flow rate table.. much easier to do it the double stoich way than having to scale airflow and every other table that uses airflow

If that method is used how do you log and tune VE and MAF?


Thanks for the replies. I'm eager to learn flex fuel tuning.

[Eaglegoat]

I don't understand the question.

AFR or lambda error should take into account commanded AFR...

Lambda has zero to do with commanded AFR.

[Eaglegoat]

Ok. So if the stoich table is 14.67 to 8.97 the multipliers like PE will work and log in lambda and make adjustments to VE and MAF as normal?



If that method is used how do you log and tune VE and MAF?


Thanks for the replies. I'm eager to learn flex fuel tuning.

It's transparent if you utilize a lambda error pid.

[bdubs]

It's transparent if you utilize a lambda error pid.

That makes sense to me. Now I need to reset my brain and scanner from AFR to lambda and figure out the lambda error pid.

Thanks.

[Eaglegoat]

That makes sense to me. Now I need to reset my brain and scanner from AFR to lambda and figure out the lambda error pid.

Thanks.

Just do some reading on lambda. Then build an AFR error pid, but replace everything AFR with lambda.

[schpenxel]

Lambda has zero to do with commanded AFR.

I am well aware. But lambda error does have something to do with commanded afr/lambda/eq ratio, however you want to do it.

[Eaglegoat]

I am well aware. But lambda error does have something to do with commanded afr/lambda/eq ratio, however you want to do it.

Lambda error pertains to lambda and commanded lambda. Absolutely nothing to do with AFR.

[DSteck]

I am well aware. But lambda error does have something to do with commanded afr/lambda/eq ratio, however you want to do it.

Lambda error has nothing to do with commanded AFR.

[schpenxel]

Actual lambda / commanded afr / stoich afr = lambda error, no?

I know there are other ways to do it. And by stoich I mean what it's set at, potentially not reality when doubling stoich, etc.

[schpenxel]

Lambda error pertains to lambda and commanded lambda. Absolutely nothing to do with AFR.

Yes, and commanded lambda can be calculated via commanded afr and stoich afr. That, or I'm totally missing something, which is always possible.

[DSteck]

Somebody missed the Commanded EQ Ratio PID.

[Eaglegoat]

Yes, and commanded lambda can be calculated via commanded afr and stoich afr. That, or I'm totally missing something, which is always possible.

Why calculate things? Use what the pcm gives you. If you do have to calculate things why would you mix units? Lambda and AFR don't mix. Lambda and EQ mix well.

[schpenxel]

Somebody missed the Commanded EQ Ratio PID.

I am fully aware of it, and use it. I was just saying.. it will work. And I'm almost sure that's the way Greg Banish shows in his DVD, but he doesn't know shit, of course.

Why calculate things? Use what the pcm gives you. If you do have to calculate things why would you mix units? Lambda and AFR don't mix. Lambda and EQ mix well.

My point was only that it works out to the same thing.

One point that I didn't make clear: When I said "stoich AFR" I meant what the computer THINKS stoich is. Not necessarily what it actually is.

Also, for E40 and older, logged EQ ratio is NOT commanded lambda. It's the inverse.. so you still have to calculate commanded lambda.

[DSteck]

I am fully aware of it, and use it. I was just saying.. it will work. And I'm almost sure that's the way Greg Banish shows in his DVD, but he doesn't know shit, of course.



My point was only that it works out to the same thing.

One point that I didn't make clear: When I said "stoich AFR" I meant what the computer THINKS stoich is. Not necessarily what it actually is.

Also, for E40 and older, logged EQ ratio is NOT commanded lambda. It's the inverse.. so you still have to calculate commanded lambda.

There's also things that are wrong on that DVD, so I wouldn't hold that as a standard. Lol. Incorporating AFR into error is completely unnecessary.

E40 just uses inverse lambda for Commanded EQ Ratio, so you can make a unique PID to handle that on E40. I tune flex fuel vehicles all the time without ever using the AFR PID in any sort of way. I could delete it completely from my scanner config, but I use it to actively back calculate volumetric efficiency based on injector size, pulse width, and actual lambda from the wideband.

[Eaglegoat]

I am fully aware of it, and use it. I was just saying.. it will work. And I'm almost sure that's the way Greg Banish shows in his DVD, but he doesn't know shit, of course.

My point was only that it works out to the same thing.

One point that I didn't make clear: When I said "stoich AFR" I meant what the computer THINKS stoich is. Not necessarily what it actually is.

Also, for E40 and older, logged EQ ratio is NOT commanded lambda. It's the inverse.. so you still have to calculate commanded lambda.

Greg is a really smart guy who has offered a lot to the community. He's also a business man. If he throws it all his best techniques on a couple DVDs then he doesn't have much to offer on his live classes does he?

Your point would be wrong, depending on the situation. Like doing an "e85" tune. At best your using an assumed stoich AFR. Then there's a flex setup, which will change the pcm stoich AFR on its own, making your function useless.

1/EQ barely qualifies as a calculation.

There's also things that are wrong on that DVD, so I wouldn't hold that as a standard. Lol. Incorporating AFR into error is completely unnecessary.

E40 just uses inverse lambda for Commanded EQ Ratio, so you can make a unique PID to handle that on E40. I tune flex fuel vehicles all the time without ever using the AFR PID in any sort of way. I could delete it completely from my scanner config, but I use it to actively back calculate volumetric efficiency based on injector size, pulse width, and actual lambda from the wideband.

I learned that one from you. Got any tips for MAT on the gen 3 pcms?