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Old 03-16-2006, 02:46 AM   #1
fatray
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Default Tuning for 100% E85 -- 1000c EGT's is it bad?

Tuning for 100% E85 recently, was running 70-80% E85. As you know if you read the E85 sticky the more E85 the leaner you go. I'm sure I might have hit 1000 degrees Celsius a couple of times. No knock, just a good run until I checked my EGT gauge. Yes it was somewhat lean at 12.5 @ around 7,500rpms with water injection. 4th gear up a hill around 115mph.
Should I check anything? Car still running top notch, although my oil cap did blow off. Ha just kidding about the oil cap, car running great AFAIK.
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Old 03-16-2006, 02:57 AM   #2
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I would get those EGTs down, its a bit high. If you haven't knocked with that lean a mix, try advancing the timing a bit where the EGTs are climbing up like that.
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Old 03-16-2006, 03:01 AM   #3
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...that is a bit over 1800F.....I wouldn't think that you would like to see anything higher than that.....like keep it 950C or less.......many turbo's have a MAX TIT of 950C
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Old 03-16-2006, 07:20 AM   #4
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E85 and alcohols like to run fat mixtures. They make max torque at significantly richer mixtures than gasoline. Max torque on gasoline is with about 25% more fuel than necessary for stoich combustion, max torque on ethanol is around 40% excess fuel. EGT's should be DOWN from your gasoline numbers. Richen that critter up, or bump your water flow at high rpms..

Lean on alcohol will melt holes in pistons even faster than lean on gasoline will.

Larry
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Old 03-16-2006, 08:01 AM   #5
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12.5:1 is very lean on E85, stoich is 9.65:1 or something close to that, so you are very lean, max power is mad at like 8.xx and like hotrod said max torque is around 6.xx, so yea, richen your mixtures a lot.

did you have to modify your fuel system to deal with the E85?

Ben
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Old 03-16-2006, 09:33 AM   #6
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I agree with posters above that air/fuel mixture is too lean. If your wideband displays 14.7 at stoichiometric A/F, then you should be richer than 11.4 on your gauge for best torque.

The water injection is an added twist. I don't think anyone's studied the effect of water injection with alcohol fuels. Alcohol fuels behave differently to gasoline in some respects. For instance, adding tetraethyl lead (TEL) is great for boosting gasoline octane but has almost no effect on alcohol fuels. One effect of water injection with gasoline is that burn time is increased, meaning more spark advance is needed. Maybe a similar effect is occuring with the ethanol.

Last edited by Jon [in CT]; 03-16-2006 at 11:42 AM.
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Old 03-16-2006, 11:39 AM   #7
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OK gotcha, I know it was too lean the EGT told that tale real quick. Glad I didn't drive too hard this last week when I started using 100% E85. Those forged piston probably saved me. I am going to add a touch of premium unleaded today.
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Old 03-16-2006, 01:49 PM   #8
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Quote:
Originally Posted by Jon [in CT]
I agree with posters above that air/fuel mixture is too lean. If your wideband displays 14.7 at stoichiometric A/F, then you should be richer than 11.4 on your gauge for best torque.

The water injection is an added twist. I don't think anyone's studied the effect of water injection with alcohol fuels. Alcohol fuels behave differently to gasoline in some respects. For instance, adding tetraethyl lead (TEL) is great for boosting gasoline octane but has almost no effect on alcohol fuels. One effect of water injection with gasoline is that burn time is increased, meaning more spark advance is needed. Maybe a similar effect is occuring with the ethanol.
Jon, why would he want to run even close to 11.4, doesn't he need to run in the 6's if he is going for max torque on 100% e85? I am not understanding that, please explain.

Ben
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Old 03-16-2006, 02:15 PM   #9
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Quote:
Originally Posted by PHATsuby
Jon, why would he want to run even close to 11.4, doesn't he need to run in the 6's if he is going for max torque on 100% e85? I am not understanding that, please explain.

Ben
His wideband meter senses lambda. Most meters have been preset to convert lambda to an air/fuel ratio for gasoline. I want him to be running a lambda that is no leaner than lambda = 0.78 for his E85. If his meter displays 14.7 when lambda = 1.0, then it will display 11.4 when his lambda reaches 0.78.
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Old 03-16-2006, 06:50 PM   #10
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My Tuner Pro seems to read E85 just like gas. If I run anything richer then 10:1 car will stumble and act like it's way too rich. If it goes above 15:1 I get the same results.

At 3,500 rpms, 14.7:1afr, 75mph in 5th gear with -boost my EGT's are steady at 1,400f. This is the same with normal gas in my car. Is my EGT reading high?
I have an Autometer EGT gauge with an EGT probe I bought on an airplane parts web site. My gauge moves with the RPM rev for rev, super quick reaction. It was recomended by many other Suby owners.
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Old 03-16-2006, 08:23 PM   #11
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Quote:
Originally Posted by fatray
My Tuner Pro seems to read E85 just like gas. If I run anything richer then 10:1 car will stumble and act like it's way too rich. If it goes above 15:1 I get the same results.
That is because WBO2 sensors only read lambda.
The display unit uses a scaling factor that is set for the fuel used. If you switch over to Alc scaling it would read ~7:1.

TMS
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Old 03-16-2006, 08:27 PM   #12
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i am with ben here, max lean torque for e85 can't be 11.4 if stoich is 9.65
then what is max rich/lean torque for e85

(gas- max lean 12.5/max rich 11.1)

edit: ok confused
i was under the impression that lambda is 1 = 14.65 to 1
where lambda for e85 should be 1 = 9.65 to 1
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Old 03-16-2006, 09:32 PM   #13
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You guys are confusing "indicated AFR" with "true AFR". If the wideband he is using is "assuming" the fuel being used is gasoline, than it will display the numbers Jon quoted. If you have the ability to change the wide band setting to read lambda directly it solves a lot of problems. If not and it only displays with gasoline AFR numbers then you need to add in a fudge factor to figure out the "real" AFR.

If the wideband displays a reading near 14.7 when he is in light throttle cruise in closed loop, then the meter is displaying "gasoline AFR's". In order to convert to true "E85 numbers" you need to divide the displayed value by 14.7/9.765 or about 1.5.

In a gasoline AFR wideband max power rich on E85 will display as about 10.5:1 and max power lean will display as about 12.7, so he is pretty close to the edge on the lean end of acceptable mixtures. I had good results with a wide band (gasoline) reading of 11.4 on my car on 100% E85, and would recommend he shoot for numbers in that area if he is using a gasoline calibrated wideband.

Code:
Fuel                        AFRst      FARst      Equivalence   Lambda
----                        -----      -----        Ratio       -----
=========================================================================
Gasoline stoich             14.7       0.068        1           1
Gasoline Max power rich     12.5       0.08         1.176       0.8503
Gasoline Max power lean     13.23      0.0755       1.111       0.900
=========================================================================
E85 stoich                   9.765    0.10235       1           1
E85 Max power rich           6.975    0.1434        1.40        0.7143
E85 Max power lean           8.4687   0.118         1.153       0.8673  
=========================================================================
E100 stoich                  9.0078   0.111         1           1
E100 Max power rich          6.429    0.155         1.4         0.714
E100 Max power lean          7.8      0.128         1.15        0.870
=======================--================================================
Larry

Last edited by hotrod; 03-16-2006 at 09:37 PM.
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Old 03-17-2006, 01:11 PM   #14
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still a little confused would a stock narrowband be at all usefull for trimming fuel in closed loop in a e85 fueled car
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Old 03-17-2006, 08:56 PM   #15
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Quote:
Originally Posted by Jaxx
still a little confused would a stock narrowband be at all usefull for trimming fuel in closed loop in a e85 fueled car
The narrowband O2 front sensor on older Imprezas will correctly report to the ECU whether the A/F is leaner or richer than stoichiometric, even though the stoichiometric A/F ratio is much lower than gasoline's.
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