Target AFR's w/ E85 & boost?
 

My car is setup on gasoline right now. I'd like to convert over to E85.
This site sucks trying to search for anything. :eyes:

Is there a general number to multiply the entire VE table to start out with? Like what percentage gain of fuel needs to take place?

9.4:1 compression 6.0L w/ 15psi of boost. What target AFR's are you aiming for w/ E85?

I add 30% across the board and start tuning from there. As far as target AFR, I'd target high 13's and low 14's at idle. For WOT you will need to get on a dyno. There are more opinions than there are assholes as to what E85 likes to be at. For now, I have LS2formula's car targeting 11.5 @ WOT but we haven't been on a dyno to see if it wants more or less fuel. On a 7 sec car, it's hard to see a 15-20 rwhp fluctuation one way or the other at the track. Too many variables. This is using a gasoline scale obviously.

You shouldn't need to do much in the tables. Just change the stoich target afr to 9.85 and set your PE to 1.3 across the board. That gives you a true afr in the mid 7.5's; if using a gasoline calibrated gauge, it will read in the 11.1 - 11.2 range.

Thanks, I got the WB figured out set for gasoline. Just wanted to know what to set the afr's.

Hmmmm..... I expect to see that kind of broad generic statement in the tech section on the corvetteforum.

I would not do it this way. There are a few modifier tables that use stoich value for the calculation. If you miss one, you could end up chassing your tail for a while.

With a gasoline AFR I target 10.8:1-11.2:1 at WOT and 15.5:1 cruise. Max rich power on E85 is achieved around 10.75:1 from the info I've seen. I always feel safer running on the richer side of things, a little extra HP isn't worth a few thousand dollar short block to me.

Don't touch stoich value with E85, what are you guys talking about? That's exactly what GM designed it for and it works fine. Either use that table as intended by design or shrink your injector flow rate table by ~35% for starters. Either way just adding everything to the VE table to compensate for E85 increases your calculated "airflow" in the PCM and that is NOT correct.

On a gasoline wideband I shoot for high 10s A/F on E85, it's alcohol based so it loves to be overfueled compared to regular gasoline.

LoL, Getting in to how you tune the car to get it there is gonna be slightly different for every tuner. It should all be Lambda based tuning anyway so WTF does it matter if you stoich is 14.7 or 200.7 Its just matching all the other values to worth with that value. You can tune using all the gas numbers as lambda is only slightly different for max power, tune accordingly .

You're talkin about changing Stoich but not using a lambda or E85 based wideband. lol.

And for the record, you should have a higher VE with E85 over gas.

Fuel AFRst FARst Equivalence Lambda
---- ----- ----- Ratio -----
=======================--====================================

Gasoline stoich 14.7 0.068 1 1
Gasoline Max power rich 12.5 0.08 1.176 0.8503
Gasoline Max power lean 13.23 0.0755 1.111 0.900

=======================--====================================

E85 stoich 9.765 0.10235 1 1
E85 Max power rich 6.975 0.1434 1.40 0.7143
E85 Max power lean 8.4687 0.118 1.153 0.8673

It matters because that table is basically a global fuel multiplier that has no effect on estimated airflow. It very much matters how you get there.

You do realize that lambda and a/f is relative right? You can use a gasoline a/f gauge and look at it's a/f ratios because it all lines up the same. Every wideband reads lambda and just converts based on the stoich ratio for the fuel. If you understood this you wouldn't have made such a comment.

Ok. So what should I do? Lol.........

Tune it normal. Do not mess with the inj flow rate. Do not mess with the Stoich value. Add 30% across the board to the VE table, leave your wideband on gas and then start tuning just like you would a car that is untuned. Assuming that we are talking about an SD tune.

I target 11.5 WOT and mid 14's part throttle. Then get on a dyno and figure out where max power and timing are and correct accordingly.

But that's just me......

That's the complete wrong way to do it seeing as how that would tell the PCM you have 30% more airflow thus throwing all your airflow and load calculated items like timing, idle, etc out of wack.

I give up.

You make it sound like switching stoich in the PCM is all you need. Regardless of which method you use, you will have to switch several tables and still have to tune. When you are used to tuning on a gas scale, you can easily miss something or calculate incorrectly. I like to keep it simple and the same across the board.

subscribed....

I never said changing one table is all you need, that's a ridiculous assumption on your part. I said changing the stoich table that GM put into the PCM for just this purpose is about as simple as you can get for a global fueling change THAT DOES NOT AFFECT CALCULATED AIRFLOW. Your airflow is not changing because of the additional fuel requirements of E85. I mentioned cutting the injector flow rate by approx 35% as another way to do it because then you don't have to worry about screwing up reported E85 ratios vs gasoline in the scanner, etc. Both of those methods will require far less changes than just adding fuel via the VE table as that changes all load and airflow tables.

This is like tuning 101 here and I don't understand the confusion behind this and how anybody can argue with it.

:corn::chug:

But it effects ALL your fueling modifiers. It also forces you to create a new custom histogram and requires you to switch your wideband over if you are logging it thru your tuning software in order to get a percentage error per cell. I am so used to looking at a gasoline wideband that seeing 7.5 or whatever on the gage would take some getting used to.

And what if they want 2 tunes? One for gasoline and one for e85. Then you're going to switch stoich back and forth in the computer and the wideband? Or are you only going to switch over the wideband when making adjustments?

I'm not saying that your way is wrong. Just that it's more difficult and can potentially cause gremlins. Hptuners and efilive do not provide COMPLETE control over the stock computer.

Yes, the stoich setting does affect all your fueling modifiers as it should.

Also correct if you want to do it that way, or you just leave your wideband set as gas a/f and create your histogram for it since it takes all of a minute to do. Or use the other method I mentioned and then you don't see E85 a/f ratios at all anywhere. Both methods will not skew airflow, load, timing, etc (which is what you want) unlike adding all your fuel to compensate for E85 via the VE table.


Then give them two tunes and leave the wideband in a gas A/F mode like pretty much everybody does.


What? It's as easy as it gets and it's how GM designed it. You are clearly not comprehending what your method of adding all your fuel for E85 via the VE table does to the rest of the "system". You need to do some digging into how these PCMs work with estimated airflow, load calculations, idle, timing, etc. Until you understand this we are at an impasse and I sound like a broken record.

...ok? So w/ my HP Tuners 2 bar SD... all I need to do is change the stoich? To 9.765, dont mess w/ the VE table, leave my WB set for gasoline and tune it as if its normal?
Sounds simple.