E-85

[cmitchell17]

I want to start experimenting with E-85 even though its 3.44 a gallon but Im thinking it will go down soon.

Right now I have the stock 24lb injectors and im about to log my duty cycle.

How can I calculate how much ethanol I can run in my tank and keep the stock injectors?

I want to go fill up with some but im scared that I dont have something in my tune right. But I need to figure out how much my injectors will let me run so then I can figure out what stoich command i can run.

Here is what I have now based on if I run about 70% ethanol

Also all this EQ ratio and AFR is messing me up. What does everyone reccomend I use AFR EQ or lambda?

[cmitchell17]

Here is a log that I logged pulsewidth but I forgot to log duty cycle.

[cmitchell17]

Heres a log with %duty cycle. Ive always heard that you should not run above about 95%

[TAQuickness]

Can't tell you much about E85. I'd start thinking in terms of EQ ratio.

[cmitchell17]

Yeah its just just gets really confusing changing all them around. I know it says to use EQ if your dealing with ethanol but why can't i just stay with afr?

[joecar]

Even with pure gasoline, some calibrations set stoich to 14.68 while others set it to 14.63... if you use EQ then these are just 1.00 in both cases.

EQ directly tells you the percentage away from stoich that you are;

I printed a little cheat-sheet that someone sent me, no worries. :cheers:

If you think that's bad, everyone else uses Lambda which is 1/EQ... :chair:

[cmitchell17]

Im going to go get some ethanol and try about a 65-70% blend.

I figure if my duty cycle right now it at 75% the max ethanol I could run is about 70%?

[cmitchell17]

When you set the ratio of fuel to stoichomietry does it automatmatically caluclutate the correct pe ratio too?

So when you chage it from 14.7 to 11 to 1 will it adjust pe mode too?

[cmitchell17]

Would it just adjust the fuel ratio for pe based on what it was set like when it was for gasoline at 14.7 to 1?

Im trying to run about 70% and if E85 needs about a 8 to 1 mixture in PE I should run around a 9 to 1?

[cmitchell17]

I put in 10 gallons of ethanol. I had an almost empty tank. Duty cycle was at about 105% at highest so im going to lean out pe a little.

Fuel trims at first were about -15 then they settlted to about -5% so im going to lean the stoic a little too.

[cmitchell17]

Anyone else that runs e85, how lean do you run it.

Ive also heard ethanol makes more torque with a richer mixture?

[joecar]

When you set the ratio of fuel to stoichomietry does it automatmatically caluclutate the correct pe ratio too?

So when you chage it from 14.7 to 11 to 1 will it adjust pe mode too?Yes, the PCM uses EQ throughout...

If PE says EQ 1.12 then you will get 12% richer than stoichiometric.

EQ 1.00 corresponds to the stoichiometric AFR as specified by B3601.

[vatman02]

Anyone else that runs e85, how lean do you run it.

Ive also heard ethanol makes more torque with a richer mixture?

I run mine at 1.16 EQ about 8.4 AFR

[cmitchell17]

Ok thanks, I wish I just knew how much ethanol I have in my tank.

[vatman02]

If your fuel trims are working they will compensate for it up to certain point. I'm not sure what that ratio would be though. If you just set your PE up at 1.16 you should be ok. I run in OLSP so I don't get any fuel trims in my car but in my truck they where 25%+ on straight E-85 without being set up for it.

[cmitchell17]

Am I right saying that my fuel trims are telling me how far away from the real stoich I am? and that I can keep adjusting my B3601 untill my fuel trims are in line.

Or is the fuel trims telling me how far away from the B3601 stoich?

[vatman02]

The fuel trims are trying to maintain stoich via the narrow band o2 sensors. The o2 sensors only know what stoich is and don't care what the pcm calls stoich. Assuming your tune is spot on, the fuel trims would be telling you how far off B3601 is from stoich. If you don't have a constant ratio of E-85 to gas you would be wasting your time adjusting B3601 because next time you fill up the ratio will change and 3601 would need to be calibrated again. I've been thinking lately that if the injector flow rate is set 15% lower the fuel trims MAY be able to compesate for either one. Effectively turning your tune into a flex fuel tune, so you could use either gas or E-85. I will give it try for my next fill up and see what happens.

Yes, the PCM uses EQ throughout...

If PE says EQ 1.12 then you will get 12% richer than stoichiometric.

EQ 1.00 corresponds to the stoichiometric AFR as specified by B3601.
After reading this, it would seem that my above statement would only work for part throttle fueling because the stoich/EQ value would not be accurate. Although I remember reading that the fuel trims are carried over to PE fueling. Maybe someone else who knows more than I do will chime in.

[cmitchell17]

Yeah that would be good if you could make it flex fuel.

Right now with my pe where it is at about 1.15-1.25 it dosent cut out at high rpms but my duty cycle is at about 98-105%.

So far im running about the same timing and tried to make by base timing table look like the one from a flex fuel tune.

About the only diffrence I can tell is the smell.

[vatman02]

The injector duty cycle is calculated so if you are seeing values over 100% it means that something is a bit off in your tune. I don't think that a stock flex fuel timing table would be the best timing you could use. I have posted up my tune for you to compare the spark tables to. here is a link to my dyno sheets, http://www.fquick.com/garages/Pontiac/Trans_Am_WS6/2002/9712/ you can see the difference my new timing table made compared to the old one. The old one I got with my procharger from a reputable shop that said they use it on all their procharged F-bodies, so I assume it was pretty close. But needed to be tweaked for the E-85.

[cmitchell17]

Ok thanks but my 5.3 just has headers and exhaust. I havent changed the fuel pressure or IFR and my trims are within about 3-4% at 11:1. Im going to log again later to day and see how its doing though.

[vatman02]

I use the same spark table for my stock 5.3 on E-85 and it works really well.

[cmitchell17]

Ok thanks ill try it.

[cmitchell17]

I just put 6 more gallons of straight e85 in and logged my duty cycle and it had a max of 96%. Can my stock 5.3 injectors really flow that much.

It had a 1.16-1.20 pe ratio and about a 1-4% positive fuel trim.