Target AFR's w/ E85 & boost?
06-16-2010, 09:12 PM
#21
Yeah, it's really pretty simple. Setting stoich to 9.765 will richen it up the approximate amount required for E85 and then you can fine tune it as you would any other time with small adjustments to the VE table if necessary. That way it doesn't skew your airflow, timing, load, etc. I also want to clarify that this is not my method per se, this is the way GM does it from the factory for ethanol based fueling adjustments.
06-17-2010, 09:07 AM
#23
Sounds good, thanks.
... And while were on the subject.. what type of gain is achievable (ball park) switching from 93 octane gasoling to E85. I know it will vary... but thought id ask....maybe i'll search and see what others gained....if i can find anything.
... And while were on the subject.. what type of gain is achievable (ball park) switching from 93 octane gasoling to E85. I know it will vary... but thought id ask....maybe i'll search and see what others gained....if i can find anything.
06-17-2010, 01:58 PM
#24
Yeah, it's really pretty simple. Setting stoich to 9.765 will richen it up the approximate amount required for E85 and then you can fine tune it as you would any other time with small adjustments to the VE table if necessary. That way it doesn't skew your airflow, timing, load, etc. I also want to clarify that this is not my method per se, this is the way GM does it from the factory for ethanol based fueling adjustments.
You make it sound like switching stoich in the PCM is all you need. Regardless of which method you use, you will have to switch several tables and still have to tune. When you are used to tuning on a gas scale, you can easily miss something or calculate incorrectly. I like to keep it simple and the same across the board.
I never said changing one table is all you need, that's a ridiculous assumption on your part. I said changing the stoich table that GM put into the PCM for just this purpose is about as simple as you can get for a global fueling change THAT DOES NOT AFFECT CALCULATED AIRFLOW. Your airflow is not changing because of the additional fuel requirements of E85. I mentioned cutting the injector flow rate by approx 35% as another way to do it because then you don't have to worry about screwing up reported E85 ratios vs gasoline in the scanner, etc. Both of those methods will require far less changes than just adding fuel via the VE table as that changes all load and airflow tables.
This is like tuning 101 here and I don't understand the confusion behind this and how anybody can argue with it.
This is like tuning 101 here and I don't understand the confusion behind this and how anybody can argue with it.
http://www.hptuners.com/forum/showth...ght=e85+stoich
Maybe EFILive works different than HPTuners. With HpTuners that stoich value doesn't do much but effect fueling on the fbodies (non-flexfuel).
06-17-2010, 02:03 PM
#25
Read this
http://www.hptuners.com/forum/showth...ght=e85+stoich
Maybe EFILive works different than HPTuners. With HpTuners that stoich value doesn't do much but effect fueling on the fbodies (non-flexfuel).
http://www.hptuners.com/forum/showth...ght=e85+stoich
Maybe EFILive works different than HPTuners. With HpTuners that stoich value doesn't do much but effect fueling on the fbodies (non-flexfuel).
06-17-2010, 06:37 PM
#27
Read this
http://www.hptuners.com/forum/showth...ght=e85+stoich
Maybe EFILive works different than HPTuners. With HpTuners that stoich value doesn't do much but effect fueling on the fbodies (non-flexfuel).
http://www.hptuners.com/forum/showth...ght=e85+stoich
Maybe EFILive works different than HPTuners. With HpTuners that stoich value doesn't do much but effect fueling on the fbodies (non-flexfuel).
I would think (maybe wrong) if changing stoich does not add more fuel in hp tuners the proper way to go about it would be to both change stoich and to use an injector value that is 30% smaller than what you actually have? thats only IF it does not effect fuel.
Im not sure what will work best but I think I will try the stoich value change tune the PE table and go from there
Here is 5 pages of the same argument on hp tuners forum
http://www.hptuners.com/forum/showth...&highlight=e85
^post 23 I think sums it up best.
It seems to me both will work but one way seems to be giving the pcm false air flow readings to get the desired fuel. (like old school piggy back boxes)
Not a knock on Cobrakiller but it seems to me that thats backwards way of going about it, But he has presented some fast cars this year and that is hard to argue with.
Last edited by Professor_speed; 06-17-2010 at 07:30 PM.
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96zjlimited (07-19-2022)
06-17-2010, 10:02 PM
#29
Professor, you should not mess with inj flow rate tables. Please note that the discussion that you linked is for the newer pcms and not for the old fbody pcms. The stoich value that you are changing is only used by the scanner as the commanded pid in order to calculate afr error %. It is not used to calculate cylinder air or any other airflow calculations.
Pwr, I'm glad it worked out for you. Did you create a new custom histogram in order to calculate your afr error correctly? I'm not sure but based on what I read, the open loop and pe tables probably won't need changed using this method as the PCM is still using 14.6 as stoich regardless of the value change there in the general tab.
Pwr, I'm glad it worked out for you. Did you create a new custom histogram in order to calculate your afr error correctly? I'm not sure but based on what I read, the open loop and pe tables probably won't need changed using this method as the PCM is still using 14.6 as stoich regardless of the value change there in the general tab.
06-17-2010, 10:42 PM
#30
I have to agree with NicD. I ran E85 for a while in my truck and all I did was adjust the stoich and modified my WB AFR BEN map so I could use AutoVE to dial my AFR right back in line (was very close) and everything worked flawlessly. I also added some timing. This was with EFILive. 
At the time I didn't have real easy access to E85, (40 miles round trip) so I only ran a few tanks through it, but i really like it! More timing and felt stronger. I might be moving to CO in a couple months, and it's all over down there, so I will probable go back to it. If so then I will just build a couple tunes for various % mixtures of E85 and regular gas and then store them in my V2. With black box flashing, I can change to a different tune in about 25 seconds when ever I want with out the laptop. 
At the time I didn't have real easy access to E85, (40 miles round trip) so I only ran a few tanks through it, but i really like it!
More timing and felt stronger. I might be moving to CO in a couple months, and it's all over down there, so I will probable go back to it. If so then I will just build a couple tunes for various % mixtures of E85 and regular gas and then store them in my V2. With black box flashing, I can change to a different tune in about 25 seconds when ever I want with out the laptop. 
06-18-2010, 02:24 PM
#34
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Injector flow has always been the simplest for me.. no playing around with O2 sensor calibrations, differences in how each OS reacts to weird commanded AFR values (many files will add timing based on commanded AFR, and its hard coded stuff, as in you have to change it yourself, it doesnt auto adjust based on what is "stoich").
You can get in a whole bunch of trouble changing it the "stoich" way on a v6 car... 8 degrees of timing is going to jump out of left field and bite you in the *** before you know what hit you.
I have put every known variation of GM pcm on E85 via injector skew, and I have yet to have an issue.
You can get in a whole bunch of trouble changing it the "stoich" way on a v6 car... 8 degrees of timing is going to jump out of left field and bite you in the *** before you know what hit you.
I have put every known variation of GM pcm on E85 via injector skew, and I have yet to have an issue.
