E85 Powered VR4?

[mjannusch]

Originally Posted by Telefonica

You can lean it out way more than that! I cruise and idle at ~18 afr with no problems. Also, after leaning it out, try increasing the ignition advance to help pick up some power. I consistently get ~30 mpg on this set up.

What kind of EGTs are you seeing when cruising that lean?

[Telefonica]

Couldn't tell ya as I don't have EGT. But it's one of the things that I've always wondered. It can't be any worse than cruising at 14.7:1. At that AFR, he should be getting the hottest burn, anything leaner should be cooler.

[mjannusch]

I think I'd want to monitor both knock and EGT for sure if trying to run that lean. With all the residual oxygen in the mixture, oxidation of the cast iron cylinder walls may be an issue. Emissions are also quite bad with lean mixtures (leaner than stoich).

I don't think my car will even run with mixtures as lean as you are proposing. Idle gets quite rough leaner than 16.5:1 or so.

[Telefonica]

It may be that my wideband is not accurate. I haven't had anything to check it against (never been on the dyno with it). I do have logs from the AEM that show ~18 AFR during cruises.

I don't know if it has anything to do with it, but my motor is only about 7k miles old.

A buddy of mine, however, has a Porsche 944T and cruises at ~17.5

[runner4053]

I know whenever I tried to tune for a 14.7 idle, my car would compensate and send it to 16 - 1. It was rather frustrating.

[jay04]

Well i ran a blend of E85...more like a 60% of gasoline and 40% of ethanol. The car ran kind of lean through out the rev range.

Jay

[Fourdoor]

Originally Posted by jay04

Well i ran a blend of E85...more like a 60% of gasoline and 40% of ethanol. The car ran kind of lean through out the rev range.

Jay

Are you still running the stock fuel pressure regulator?

I am heading up to the track today for the last day of the 1/4 mile season and I will be runing a 50% 93 octane, 50% E-85 mix. I just finished installing a fuel system from 3sx, and I will be running around 55 psi static fuel pressure to compensate for the extra fuel needed due to the E-85 mix. Without any ECU tunning, or larger injectors a 50 / 50 mix is the furthest I am willing to go this season since I don't want to run rediculously high fuel pressure. Next spring I will install the injectors and EMU, and then I will run pure E-85 for the summer.

Keith

[jay04]

I am running a after market FPR. I didn't turn the fuel pressure up. Was I suppose to? I am gonna turn the fuel pressure up so it can compensate.

Let me know how it turn out today. Do you have a wideband? If you don't how are you gonna know how much to increase the fuel pressure by?

Jay

[Fourdoor]

Originally Posted by jay04

I am running a after market FPR. I didn't turn the fuel pressure up. Was I suppose to? I am gonna turn the fuel pressure up so it can compensate.

Let me know how it turn out today. Do you have a wideband? If you don't how are you gonna know how much to increase the fuel pressure by?

Jay

My best run today was 13.089 @ 105.30. Keep in mind that is in a spyder with a race weight of 4320 lbs with me driving.

To set my fuel pressure, I did some calculation based on using a 50 / 50 mix of 93 octane and E-85. For 100% E-85 you would need around 30% more fuel, so for a 50 / 50 mix you would need around 15% increased fuel. I used a fuel flow calculator to determin that an increase to 55 psi base fuel pressure would give me around the fuel flow needed, with any other adjustments made by the ECU. Since I don't have the fuel pump hot wired, it will only push around 50 psi at idle on the low voltage feed. I turned the screw in a couple more turns after pressure stopped rising and called it "good enough" .

Keith

[mjannusch]

Keep a close eye on the fuel pressure gauge when running higher boost with the base pressure cranked up that high. A lot of pumps flow a LOT less fuel volumes at higher pressures.