Target Static compession on E85?
11-07-2007, 01:35 PM
#21
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I have a own dynapack that i work with almost every day. I think i have done 4-5 pcs NA cars that we changed to E85. About 5-10% is what i have seen, with about 10 degrees more timing then pumpfuel.
11-07-2007, 01:40 PM
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11-07-2007, 04:13 PM
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That's the a/f for pure ethanol.
100% Gasoline @ 20,000 BTU's/lb has an a/f 11:1 to 13:1 under "best power" with a stoich of 15.2 for "cruising" (remember fuel is usually watered down with methanol or ethanol creating the 14.7 standard)
100% Ethanol @ 11,500 BTU's/lb has an a/f of 4.3:1 to 8.2:1 under "best power" with a stoich of 9:1 for cruising.
100% Methanol @ 8,600 BTU's/lb has an a/f of 3:1 to 5.9:1 under "best power" with a stoich of 6.5:1 for cruising
100% Nitro "Top Fuel" @ 4,900 BTU's/lb has an a/f of 1.1:1 to 1.7:1 under "best power" with a stoich of 1.9:1
So in reality the A/F you will require for cruising with E85 is going to be about 9.9:1 under cruising and possibly in the range of 5:1 to 9:1 under enrichment.
Also take note the loss of energy from ethanol but the fact that you use more volume in the fuel creates the extra power that you see by using the fuel.
Lambda under its stoich a/f will always read "1 Lambda" on an air fuel meter. It is the PCM's job to convert "1 Lambda" to its appropriate stoich a/f ratio value for the type of fuel it thinks you are using.
Back on topic!
100% Gasoline @ 20,000 BTU's/lb has an a/f 11:1 to 13:1 under "best power" with a stoich of 15.2 for "cruising" (remember fuel is usually watered down with methanol or ethanol creating the 14.7 standard)
100% Ethanol @ 11,500 BTU's/lb has an a/f of 4.3:1 to 8.2:1 under "best power" with a stoich of 9:1 for cruising.
100% Methanol @ 8,600 BTU's/lb has an a/f of 3:1 to 5.9:1 under "best power" with a stoich of 6.5:1 for cruising
100% Nitro "Top Fuel" @ 4,900 BTU's/lb has an a/f of 1.1:1 to 1.7:1 under "best power" with a stoich of 1.9:1
So in reality the A/F you will require for cruising with E85 is going to be about 9.9:1 under cruising and possibly in the range of 5:1 to 9:1 under enrichment.
Also take note the loss of energy from ethanol but the fact that you use more volume in the fuel creates the extra power that you see by using the fuel.
Lambda under its stoich a/f will always read "1 Lambda" on an air fuel meter. It is the PCM's job to convert "1 Lambda" to its appropriate stoich a/f ratio value for the type of fuel it thinks you are using.
Back on topic!
In general with NA applications, you have to run a lot more compression with ethanol than gas to achieve the same power level on similar setups. If you are going to run about 15psi, you can pretty easily run 10:1 static compression. That is the beauty of ethanol, is that it is highly resistant to pre-combustion detention.
Of course there is the down side in that you will have to run a lot more fuel. Gas requires 14.7 oxygen molecules to burn one, while ethanol is around 9 I believe.
Keith
Of course there is the down side in that you will have to run a lot more fuel. Gas requires 14.7 oxygen molecules to burn one, while ethanol is around 9 I believe.
Keith
Last edited by Rodrigues; 11-07-2007 at 04:20 PM.
12-11-2007, 11:07 AM
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My tuner thinks I should keep the CR down to 8.75:1. I think I would have better drivablity, more lower end power, and perhaps better MPG it I raise the CR. I was thinking some where between 9.5:1 - 10.0:1.
Anyone have any thoughts or ideas on this?? Experiance is king! Anyone running a higher CR with boost?
Thanks - Ron
12-12-2007, 05:40 PM
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i'm running at 11.4:1 with 8-9#s. as soon as i get the new fuel pump in i will be putting on the smaller pulley and should see about 13# on the ATI crank pulley. i am trying to get a bigger crank pulley but the guy who makes them is not avalable. i am running 42# injectors at 187% duty cycle with a single walboro? pump. i have no issues with detonation or preignition, and saw and AFR of 14:1 at wot at 6400 rpm. i was running this current set up on my local high octane 91 and still had no issues. if you guys want to run the E-85 full time i would set compression to 11:1. this will leave you the ability to still run pump gas, if for some reason you cant find an E-85 station.
