Target AFR for E85
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Not sure if you know how the PCM calculates the fueling but here goes.
E85 stoich is calculated like this:
Ethanol Stoich: 9.0 x 85%= 7.65
Gasoline........: 14.7 x15%= 2.21
Stoich for E85:.................9.86
So, at lower throttle openings, the A/F ratio is 9.86.
But the PCM to references stoich as "Lambda" which is 1.00 so all you have to do is set the stoich to whatever fuel you are using and the rest of the PCM setting are good.
There are a number of tables for enrichment and they simply work off of Lambda. For example, the PE table multiplier to achieve 13.0:1 for 100% gas is 1.13 (14.7 / 1.13=13.0). So using Lambda then becomes .88 (1 / 1.13=.88).
I know this is a little confusing. For more information, pick up the tuning books written by Greg Banish.
E85 stoich is calculated like this:
Ethanol Stoich: 9.0 x 85%= 7.65
Gasoline........: 14.7 x15%= 2.21
Stoich for E85:.................9.86
So, at lower throttle openings, the A/F ratio is 9.86.
But the PCM to references stoich as "Lambda" which is 1.00 so all you have to do is set the stoich to whatever fuel you are using and the rest of the PCM setting are good.
There are a number of tables for enrichment and they simply work off of Lambda. For example, the PE table multiplier to achieve 13.0:1 for 100% gas is 1.13 (14.7 / 1.13=13.0). So using Lambda then becomes .88 (1 / 1.13=.88).
I know this is a little confusing. For more information, pick up the tuning books written by Greg Banish.
Pro
Joined: Mar 2006
Posts: 583
Likes: 0
From: OKC OK
Depending on the blend ( from e70 to e85), part throttle stoich is 9.7-9.9. I have run as lean as 10.2 at PT.
Wide open throttle power AFR range is 6.9 to 8.6.
Remember, the blend affects it greatly, and will vary from summer to winter.
Your 2008 should adjust accordingly.
Hope this helps you.
Jim
Wide open throttle power AFR range is 6.9 to 8.6.
Remember, the blend affects it greatly, and will vary from summer to winter.
Your 2008 should adjust accordingly.
Hope this helps you.
Jim
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
If possible, to make it less confusing tune on the gas scale. This will also give you finer adjustments (more resolution).
Knowing that above,
I would start @ 12.5:1(gas scale) afr OR .85 Lambda.
Pump e85 may not be 85% ethanol but even the race guys have seen very little difference with varying grades on the same tune.
Knowing that above,
I would start @ 12.5:1(gas scale) afr OR .85 Lambda.
Pump e85 may not be 85% ethanol but even the race guys have seen very little difference with varying grades on the same tune.
Burning Brakes
Joined: Aug 2008
Posts: 802
Likes: 6
From: Oro Valley AZ
If possible, to make it less confusing tune on the gas scale. This will also give you finer adjustments (more resolution).
Knowing that above,
I would start @ 12.5:1(gas scale) afr OR .85 Lambda.
Pump e85 may not be 85% ethanol but even the race guys have seen very little difference with varying grades on the same tune.
Knowing that above,
I would start @ 12.5:1(gas scale) afr OR .85 Lambda.
Pump e85 may not be 85% ethanol but even the race guys have seen very little difference with varying grades on the same tune.
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