E85Forum.com

jmanley · Joined: 23 Jun 2009 Posts: 13 Location: Fargo, ND

I know that for gas, Peak Torque should be at about 12.2 AFR (0.83 lambda), and Peak Power should be about 12.5 (0.86 (?) lambda).

Do you know if I should use similar lambda values for E85?

Jay

Eric68 · Joined: 01 Nov 2007 Posts: 331

Depends on your engine and combo, but I have found best power on E85 a little richer than on gas. More like .77-.81 Lambda. I haven't done many E85 tuneups on the dyno, just my two motors (both SBC).
_________________
E85 racer and E85 carb builder
www.horsepowerinnovations.com

E85 powered 68 Camaro street car
Best ET on motor 9.96 @ 133 MPH, 5.92 on N2O in the 1/8th

hotrod · Joined: 19 Apr 2005 Posts: 872 Location: Colorado

I also have found best power and torque on richer settings.
One of ethanol's strengths is since it is an oxygenated fuel, it has wider flammability limits. It will burn cleanly at mixtures that are so rich on gasoline the engine would hardly run.

Bottom line maximum power and torque boil down to burning the maximum amount of oxygen possible, since almost all engines are oxygen limited. Your intake air is usually the ultimate limit to power if you do not have problems with detonation or heat over load.

Ethanol allow you to burn up more of your available oxygen and release more heat in the cylinder at richer mixtures.

I usually recommend between 0.76 and 0.82 as the range most engines will give best performance on E85.

The precise mixture will depend on things like compression ratio, head design and mixture motion etc. which are engine specific.

Larry

newalky · Joined: 30 Sep 2008 Posts: 84

Drag Chevette · Joined: 18 Sep 2007 Posts: 458

Eric68 · Joined: 01 Nov 2007 Posts: 331

XL SBC for an XL kinda guy. Laughing

_________________
E85 racer and E85 carb builder
www.horsepowerinnovations.com

E85 powered 68 Camaro street car
Best ET on motor 9.96 @ 133 MPH, 5.92 on N2O in the 1/8th

440Jim · Joined: 01 Jan 2008 Posts: 188

I hope to test and tune on Sunday. I was going to either try a few ignition timing settings (30, 33, 36), or the A/F. Now I am thinking of just leaving my timing at 34 and adjust my A/F from the 12.3 (gas scale) I am currently at.
12.3/14.7 = .836 Lambda on my wideband
.836 x 9.8 stoich = 8.2 actual A/F with E85

440Jim · Joined: 01 Jan 2008 Posts: 188

I went to a test and tune and tried 3 different A/F on my mechanical injection system with E85. I had been running Lamba=0.836 (A/F=12.3 gas) and I tried 0.82 and 0.81 with almost no difference once I accounted for the temperature change as the night went on. The car went 9.38 down to 9.36 at the end (coolest and richest), but I think that was all weather.

This setup does stage (footbrake 2500 rpm) at Lambda=0.76 (11.2 on the gas scale), and shows no lean spike when I mash the gas.

440Jim · Joined: 01 Jan 2008 Posts: 188

As a follow up to Wednesday's test and tune results. I got to the track early this Saturday for the ET bracket race and they had a short open test session, so I got 3 time trials before eliminations. On Wednesday, I had the high-speed bypass set at 77 psi, and since the pill changes were having a smaller effect than I expected, I turned it up to 80 psi for Sat.

I started with a 0.098" bypass pill in the injection setup (rich) and the wideband showed 11.8-11.9 A/F on the gas scale (lambda=0.80). The second pass I put a 0.102" bypass pill in and it went quicker with 0.3 more mph with the wideband showing 12.2 A/F (lambda=0.83). So I stayed with that the entire night of eliminations. It was very consistant.

11.9 __A/F__ 12.2
1.277 sixty ft 1.268
5.923 1/8 ET 5.906
114.25 mph 114.35
9.398 1/4 ET 9.375
140.14 mph 140.46