can you change the target a/f ratio across the board so that you can run e85?

 

Along with this question, your fuel system must be compatible (which I'm most likely sure, the stock one isn't) It can eat up gaskets / o rings, etc...

Raf

 

Yes you can, its the stoichiometric air/fuel ratio.

 

It depends upon which Mask you are running in the '7730. The required changes differ between them. However, the answer is that any of them can be changed to suit E85 or any mix inbetween.

RBob.

 

I am actually thinking of writing some code to use one of the Ethanol content sensors myself (I have one in my hands for a modern 5.3. It shouldn't be too hard, just enable one of the extra inputs (I'd use the VATs input since I don't use it anyway and the flex fuel sensor outputs a frequency between 50 and 150 hz, depending on how much ethanol is in the mix, 50 hz for 0% ethanol and 150 hz for 100%), use that for a lookup table for a multiplier for stoichiometric a/f ratios and AE/DE. I have checked and the fuel around here varies between 5% and 25% ethanol, despite the 10% claim on the pump. Really sucks when you get into some that is doused with extra ethanol.

http://www.megamanual.com/flexfuel.htm

 

I was doing the same as the code changes are rather easy. It all came to a halt when the sensor prices went over $600. From what I've heard GM is having issues with sensor reliability. Some of the newer GM flex fuel vehicles don't use the sensor and use some smart programming instead.

With an open loop calibration the varying E content doesn't do any good. At the same time E85 has become available locally. That makes it easier to play with. I've always thought of it as cheap racing fuel.

RBob.

 

ok thanks for the input everyone i will be checking in with you as i move along since i dont know much about editing masks and such (using charts, graphs and ect is np to edit the tuning but im still learning the rest as i go) i know its not compatable with the fuel system but everything is being replaces since cars being completely rebuilt(trying to keep it somewhat budget hence stock ecu) however e85 isnt as corresive as everyone thinks(approx 30% more corresive then gasoline compaired to 200% more from methanol) anything made 87+ can handle it since thats when 10% was introduced into the gas iirc might be wrong on the year

 

Hey Rbob, if I remember correctly, you are in Pa? where are you finding the E85?

boy that would open up some neat possibilities....12:1 compression anyone?

 

These two stations are listed at the www.e85refueling.com/ site:

S & B Auto
1135 Vine St.
Philadelphia , PA 19107
215-928-9181

Allentown Service Plaza, PA Turnpike
5052 Cetronia Rd
Allentown , PA 18106

Both are a little far for me.

Last weekend I saw a station on Ridge Pike in West Norriton with a sign stating that they carry E85. I still need to get over there with a can to purchase some. I don't want to just pump it into the car and have to tune it with whatever the mix ends up being.

There is a straight forward water test to read the E content. So playing with that is also in the plans.

RBob.

 

The 730 ECM and the 427 ECM have unused inputs that you could run to a toggle switch to switch between the two fuel cals. Some of the things like AE, DECEL, crank_pw aren't AFR based in some bins so you need to look into that a little.

EDIT: I use this "switch" setup to deal with different mixes I put in the water/alky tank under the hood of the truck. It just messes with the inj. PW (AFR) and timing (pulls spark) when the ECM turns on the water/alky pump PWM.

 

Same here. I tend to use more fuel pump and injectors than required when doing a new turbo setup. If you have the fuel system over-sized appropriately, then a simple cal change, up the boost, and sit back for some fun.

 

sorry to bring this back up but i was planning on using the saujp mask, since this dosnt support wideband fueling how would that affect the computer? since a narrowband o2 only reconizes 14.7:1, richer, and leaner would the computer even be able to have consistant fueling?(since really it wouldnt be able to read the correct stoich for e85?) mayby im missing something here. just trying to learn as much as possible im probably about a month away from first startup still

 

A NB O2 sensor will report stoich as stoich, fuel doesn't matter. It will still switch high/low at stoich, even if that happens to be 9.0:1, 10.5:1, or 14.7:1.

The reason to change the commanded AFR is to add the additional required fuel. The PW will be larger with a lower commanded AFR.

When running E85 change the stoich constant (in $8D mask) to 9.7:1 to 9.8:1. Most of the other fueling parameters will fall into line. As they are based (in $8D) as a percentage of the stoich value. Although AE may need to be tweaked.

RBob.

 

Interesting.....

So there is somethng that happens at the stoichiometric point of a burning fuel that the O2 sensor will interpret the same way, no matter what the fuel is?

Any reading in this?

 

its called the lambda system i know widebands use it(they just change the displayed afr according to which fuel is being used but lambda 1 is stoich for every fuel) now that i know nb o2's use it as well it solves much of the worrys i had

 

Yes, a certain amount of gas in the exhaust.

As stated above, the O2 sensor reads stoich always. The ECM reads the O2 sensor and tries to maintain stoich.
The ECM has a stoich. AFR value that RBob mentioned. This is used to "pre-guess" at how much fuel is needed to maintain stoich. The O2 sensor reports back how far from stoich the mixture was. The ECM uses this info to correct the fuel mixture.

Notice all the talk about stoich above............that translates to 14.7 for gas, 14.13 for E10, 9.7 for E85.

The O2 sensor always reads stoich (lambda), and not AFR.

 

Me too. Once an e85 station pops up around here I'm on it. I'm running 10:1 compression and a blower. If I could get more boost or more spark advance or both I'd be happy as pie. Right now I'm only running 21 degrees of advance with 6psi boost because of the high compression.

-- Joe

 

Dennis Burke (Burke Oil) / Chelsea, Ma. is listed as selling E85. Not sure if it is a pump.

I would like to try E85 too. I have a bone stock 1986 305ci TPI (9.5:1 compression) with 8-9 PSI of boost that I run 18* of advance with the water/alky injection on (50% water / 50% eth&meth mix). That is running 87 octane E10 gas. By using 93 octane E10 gas, I can add about 6* of timing and this gains 1 second in the quarter mile ET. The intercooler is 24"x12"x4.25" thick......very big. That helps with the detonation.

I have tried up to 12 PSI of boost with 93 octane, but the 700R4 in the 5000lb rig would just slip when it hits second gear.

BTW, For anyone wondering about E10 fuel octane. What the pumps says for octane is what you are getting. If it says 93 octane and contains 10% ethanol...........all you are getting is 93 octane, NOT 93 octane plus 10% ethanol octane (95.6 octane).

 

I'd probably burn a tank of gas just driving to chelsea and back. I need something local. Like in town or within a few miles. It will happen eventually. I hope.

Your 305 is iron heads right? My motor is 10:1 with alum heads. I've always been told that alum heads take soo much heat out of the chamber its like running a full point less static compression.

-- Joe

 

Yes, stock iron heads (P/N 416). This engine likes 93 octane much better than 87 octane. It will ping slightly during TPS changes under heavy loads on 87 octane. It won't ping with 93 octane. It never pings under boost with 87 octane because I pull so much timing.......and reduce HP at the same time.

Yes, alum. heads allow more timing. Some say the alum. SCR is about .5 to 1.0 point different than iron. SCR.