TRex

iTrader: (3)

Hmm, ok, so then what does it do in the PCM ? I mean - given the mixture of E85 and Gas could be anything between 0-100%, the AFR would need to be a sliding scale. How do the tables in the calibration work ?

hondo

iTrader: (2)

I have not looked at a flex fuel tune, but I would think that's basically the idea, a table that is % of ethanol vs enrichment the same as coolant temp, iat etc are modifiers to the fueling. there must be tables for timing vs % ethanol also.

Bombguy99z28

I don't think our OEM PCM's will support anything that would sense the fuel type, could be wrong though. Basically, you could figure out the lambda for specific mixes and tune it for that (say 50% E85/ %50 gasoline) but if you wanted to just run random mixes I don't think it would work without a ton of work (installing the hardware to run whatever flex-fuel sensors are involved, plus a PCM and wiring that could support it).

Now, maybe EFI Live can do a custom OS that could handle the PCM side of it, you would just have to figure out a way to get the signal from the flex-fuel sensor to the PCM and have the PCM be able to interpret it. For instance, wire the signal line from the flex-fuel sensor (pretend its 0-5mv, I don't know what it would be) into some unused 0-5mv sensor feed and have something monitor that voltage to determine what fuel is running.

But thats all way over my head, I don't know if thats even a valid idea.

ringram

I think Joecar is on the right track. If you run open loop with a WB to check you can sort out the correct ratio 7.5:1 or whatever it is for E85 stoich.

Remember the O2 sensors measure unburnt O2, so the 14.7:1 is really just another way of saying that with pump petrol that Im burning around 14.7 parts air to 1 part fuel because the O2 I see tells me I must be because of the O2 read from the exhaust.

So running the correct ratio of E85 with air in theory should result in around the same amount of O2 picked up by the O2's.

Someone else mentioned the measure Lambda, which is correct. They switch on complete combustion of air/fuel based on O2 output. So low O2 = high MV, high O2 is low MV.

So for closed loop you dont need to do much. You might want to tune your VE though so things work nicely at WOT.

hondo

iTrader: (2)

I dont know what # the pcm's in the flex fuel trucks are and if theyare compatible with f-bods or vettes, but software wise with efilive you can take "sections" of an OS and paste them into others, (IE swapping a 4l80e into a f-body) maybe the flex fuel OS or parts of it could be written into the f-body pcm, then just use the stock sensor gear from a FF truck. Someone get wait4me (jesse) in here he's worked with alot of this stuff.

Steel Chicken

iTrader: (3)

ringram, you got it.

...

you have to scale the injector tables because you need to flow ~40% more fuel compared to gasoline. (this is for someone who is converting to e85 only, not a mix)
technically, you could also scale your VE table as well. both should give the same result.

for someone who mixes all the time, you need the two VE tables, and a sensor to calculate how much ethanol is in the fuel, and convert accordingly.

as far as the PCM is concerned, 14.7:1 is an calcuated value. take the amount of o2 remaining in the exhaust, extrapolate how much fuel versus air is burned to reach that value, and thats how the AFR is calculated. With ethanol versus gasoline, the 14.7 number itself is no longer accurate, BUT the goal of getting the same remaining O2 left in the exhaust *I believe* is still the same. Its just takes a lower AFR(read, more fuel) to do it, because Ethanol contains its own oxygen.

I know Im not explaining this right, perhaps someone who knows the terminology better can explain it.

RICE ETR

iTrader: (3)

Any of you guys running straight E85 do any upgrades to the fuel system components? I want to try it but can't get a firm answer on if my injector o-rings/fuel pump/stock lines etc.. will handle the alcohol.

Thanks

MIGHTYMOUSE

iTrader: (59)

that is exactly and everything you should need to do. target AFR should remain the same since you are not changing desired lambda.

TRex

iTrader: (3)

Why do you say that ? The VE hasn't changed, only the Stoich with the alcohol ?

Runn

Just changing Stoich AFR should be alot easier. And i think that would be enough.

Bombguy99z28

I think a lot of people posting in this thread aren't reading everything in this thread. Your Volumetric efficiency is airflow. It isn't changing. Your injectors aren't changing. Your stoichiometric is changing. So just alter your stoich to whatever fuel you are burning (i.e. 9.675:1 for E85).

Why on earth would you change your airflow measurements (VE) in the PCM to compensate for fueling? This is a computer. Its all algorithims. You only change the data for whatever variable has been modified.

If X * Y = Z, and you make a change to the data that results in Y and that alters Z, you wouldn't go in and change X to make Z what you need. You can do it, but any other algorithim that uses X will now be innacurate even if Z gives you the result you want.

Your fuel injector data should be static based on what injectors you run. Your VE should be static after being tuned so that commanded afr = real afr.

These two tables are representative of the airmass/fuel = stoichiometric.
At WOT you have your PE factor that that adjusts your targetted air/fuel ratio, which is stoichiometric/PE.

So say X = AIRMASS (VE), Y = FUEL, and Z = (commanded AFR, stiochiometrc/PE)

A simple idea would be X/Y = Z. By changing Z, the computer will alter Y to balance the equation. That easy.

o2s measure lamba. The PCM has no reference to lambda, it referencs GASOLINE lambda, you are just changing that reference to E85 lambda.

Steel Chicken

iTrader: (3)

bombguy now that youve explained that way, it makes alot more sense. certainly the easiest way to solve the problem.

I was looking at a stock non-e85 bin file, and the Stoich AFR ratio has multiple columns for percentages of aklyhol, and in the non-e85s, it looks like all the values are 14.68

so in an e85 vehicle, those numbers would decrease as you move along as the percentage of alky goes up?

Runn

I´ve looked at the L59 engine and it change the Stoich AFR from 0% Ethanol to 100% Ethanol.

hondo

iTrader: (2)

exactly

LoWeLL216

iTrader: (1)

I think a lot of this stems from people still just scaling injector flow rates instead of just plugging in the correct values for new injectors. Someone mentioned it earlier, but it's a very backward (and incorrct) way of "balancing the equation."

soundengineer

iTrader: (16)

I think I can make people understand....

IGNORE the term AFR....it doesnt exist according to your o2 sensors....
all your Stock o2 sensors care about is Lambada 1.0..known as stoich to us...

so it doesnt matter what you burn....or what AFR it is in real life...
if you burn e85 and its stoich AFR is 9.675....then that 9.675 is still lambada 1.0 to your O2 sensors

so your sensor is adjusting to see 1.0 lambada..not adjusting to a specific AFR...


a wideband just happens to be accurate at other lambada values....then its just a matter of a mltiplier to see it as an AFR value..

all the sensor does is report lambada 1.0 as a voltage(in our ls1's around 450mv) and the computer doesnt care that you had to dump in 9.765 AFR to get to 1.0 lambada...
the PCM see's this reported 450mv...and its happy...less and it adds fule..more and it takes away...
once your fueling is all correct then its simple math for the other parts of the PCM..
again..its not PE of 13:1 AFR.its PE of Multiplier of 1.131 compared to the value in the current cell that it is using...

hope this helps some people a I can see some are still confused...

do you need to change anything fuelung wise for E85..yes you either need to get larger injectors by Approximately 40% or you need to bring up you VE and MAF tables by approximately 40%.....in which case..you probably need bigger injectors anyways...
so upsizing the actual injector is the best way to go...get the exact right size of injector and you wouldnt have to change the VE at all...but none of us is that good..LOL

Runn

Here´s the thread with more info... http://www.hptuners.com/forum/showthread.php?t=503

soundengineer

iTrader: (16)

GM uses the AFR stoich value to increase or decrease injector flows for the Alchohol...since it takes more fuel to get a stoich burn with e85..then you have to have some way to tell it to add the necessary fuel...
they could have 2 ve tables...and 2 maf tables and 2 of every table that usues a fuel calc..or they can just have 2 stoich values and a multiplier element...
more e85..higher multiplier...
think of it in the same fashion as PE...only its a fixed amount depending on how much alky is present...50% blend..= 50% between multipler for gas and alky...

Bombguy99z28

Much better explanation than mine

LX1

iTrader: (2)

http://www.turbomustangs.com/smf/ind...?topic=47094.0

Link to a turbomustang guy that runs e85