Gents would it gain me mileage or anything else by setting stoich to pure gasoline instaed of e-10
Here in Canada all premium gas is 100% gasoline
I understand from reading the widebands adjust for stoich , is it adjusting to the stoich that's entered or can it determine stoich for whatever fuel is in the tank
I'm curious about this as well. What changes do you need to make to run a different stoich?
So lets say .82 lambda is the sweet spot for making power at WOT with e10 and you change to pure gas, you wouldn't need to adjust your lambda value of .82 at WOT, just your stoich right? You aren't gunning for a specific Air Fuel ratio, just a percentage of a given stoich correct? .82 lambda would still be the the same magic number for making power even with e85 right?
Last edited by AKDMB; 06-22-2015 at 10:08 PM.
The PCM will compute lambda based on your stoich setting. So if you are running e0, you should change the stoich to 14.64 to get you fuel trims in line.Originally Posted by buzzard32
You should see an improvement in mpg because with your current setup of running e0 fuel with an e10 stoich, you are slightly rich.
There is no way for our cars detect the type of fuel in the tank.
Changing stoich will change your AFR. If you are using .82 lambda with 14.1 stoich, your AFR is 11.56 (14.1 x .82 = 11.56). If you change stoich to 14.7 without changing lambda, you will have a different AFR. (14.7 x .82 = 12.05)
Remember AFR is the result of stoich and lambda, so if either change, your AFR will change too.
So would you then want to lower your lambda value to like .78 (roughly) to get back to the 11.5 Air Fuel Ratio?
So what would you recommend for WOT with 100% gas
With the e10 I had it set at.84 but e10 needs to run richer so with e0 I was running real rich correct?
If you are 100% sure that your fuel is e0, yes.
Last edited by txcharlie; 06-23-2015 at 10:39 AM.
Thanks for all the help man! So I guess you would have to make blanket changes to all the fueling tables, richening them up by a little bit, .4 λ or so?
Last edited by AKDMB; 06-23-2015 at 04:51 PM.
I don't think the fuel table need to be changed. The PCM will make any needed changes based on LTFTs.
Last edited by txcharlie; 06-23-2015 at 06:33 PM.
If you were at .84 on e10 stoich, you were running 11.8 AFR.
If you change your stoich to 14.64, you will need to command .785 lambda to keep a 11.5 AFR.
Last edited by txcharlie; 06-23-2015 at 06:53 PM.
Lol .04λ, not .4λ. This forum rocks guys, can't tell you how much this has helped me
Last edited by AKDMB; 06-23-2015 at 07:23 PM.
No problem! Happy to help where I can. Lot's of guys on here willing to help.
The old LS2's from "down under" had a interesting feature called lean cruise mode. Which meant with light throttle it would bump the AFR up to about 16:1 for better gas mileage. The EPA didn't allow this in the U.S., but an interesting concept. I wonder If you could work that out for better gas mileage with the Copperhead.
I don't think your corn burning monster would like 16:1 very much.
You don't need to change your WOT fueling to adapt to AFR, 0.82 lambda is 0.82 lambda regardless of gas, e0, e10, e85, e100 etc. What you need to tell the pcm is the stoich ratio of the gas in use so the computer can precisely correct fueling for the gas in question.
Measure the content of alcohol in the gas, and adjust your AFR stoich accordingly in the calibration, correct your MAF period table if needed, and enjoy. if you're telling the PCM to shoot for .82 lambda at WOT, and your MAF period table is correct, you'll get .82 lambda at WOT, that's the beauty of tuning with lambda, you don't need to worry about AFR, just tell the PCM what's the stoich ratio is for the gas in use, that's the only time you'll worry about AFR.
I have a Silverado truck E85 ready from the factory, the sensor can tell what I have in the tank, so I only adjust the MAF table (equivalent of MAF period in our stangs) and voila, no matter what I fill the truck with, stoich moves around -2%+2% in CL, and my WOT fueling is .82 lambda in OL regardless of what gas I pump. we don't have a alcohol sensor in the Stang, so we have to tell the pcm what the engine is sipping, after that, the pcm does everything for us.
That makes a lot more sense. Do you have to have a different MAF curve for each fuel? I wouldn't have thought you would have had to adjust the MAF curve at all once you have it established with one Fuel. Why is this?
There is no need to mess with the MAF settings once they are dialed in just because you are switching fuels. The only time MAF settings need to change is if the measured airflow changes which can be the cause of more boost or different hardware such as a CAI.
So just change stoich and go? Obviously you might add a little timing for power or play with the cold start for e85, but functionally, that's all that's required, correct?
If you are N/A and moving to e85, you will need the following:
1. 47lbs. FRPP injectors.
2. Change the Stoich AFR from 14.08 to 9.85
3. Decide what you want your afr to be. Attached is a spreadsheet I put together last year to help with deciding what you may want to run. .82-.85 would be where I would target it and see what nets the best results.
Last edited by wbt; 06-29-2015 at 02:16 AM.
He asked how to switch stoich and keep 11.5 AFR. I believe that's what I told him how to do.
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