tune for better gas mileage?
Mar 15, 2007, 11:01 AM
#34
13:1 might be what a GDI motor likes (which is close to max power gasoline AFR).
The Audi R8 runs 12.2:1 compression and 20psi of boost thru to 37.1mm restrictors on crap Elf fuel. I am sure that a normal compression GDI motor might be able to run leaner.
The Audi R8 runs 12.2:1 compression and 20psi of boost thru to 37.1mm restrictors on crap Elf fuel. I am sure that a normal compression GDI motor might be able to run leaner.
Jul 11, 2007, 06:27 PM
#37
Well leaning out the map in the curse area is stupid the ECU will try and correct it back to a 14.7 and if you go far enough with the map it will toss a lean code.
I think some cars may have O2's that are off a tad causing leaner cruse o2 to get there killer mileage and others will have O2's on there way out that get the very crappy mileage. I have seen 3 evos now with dead front o2's and the ECU has not thrown a coed and is trying to dump a crap load of fuel to get the O2's up.
On my car I have the O2 turned off in the Ecu buy setting all my switch over load points to 10. I have it set to run a 15.0-15.2 on gas. I found if I went any leaner the car would lose some power and the mileage would not get any better. On my last 1500mi road trip I ran it as lean as a 16.0 on a whole tank but found that 15.2-15.5 gave better mileage and drove better.
Also with cars that have idle problems from intakes having the O2 off makes them idle much smoother. The Maf and O2 seem to start fighting each other. set the idle O2 in the 13.9-14.5 range
Also setting the maps to lean will also cause the car to drive like crap when its cold.
On my car on gas I got a avg of 26mpg on my 1500mi trip with one tank right at 29mph on a flat section.
On E85 I have my car tuned to a 15.5-16.0 AFR and it gets about 22mpg on the hwy cruse.
Even on my 1500mi trip with a few mt passes my AFRS were always with in 15.0-15.5 so the stock Ecu does great with the right fuel adj for different conditions. I always run Chevron 92. I guess if you were switching different gases a lot like some with 10% alc and others with out you may really need the O2 to keep things in check.
I think some cars may have O2's that are off a tad causing leaner cruse o2 to get there killer mileage and others will have O2's on there way out that get the very crappy mileage. I have seen 3 evos now with dead front o2's and the ECU has not thrown a coed and is trying to dump a crap load of fuel to get the O2's up.
On my car I have the O2 turned off in the Ecu buy setting all my switch over load points to 10. I have it set to run a 15.0-15.2 on gas. I found if I went any leaner the car would lose some power and the mileage would not get any better. On my last 1500mi road trip I ran it as lean as a 16.0 on a whole tank but found that 15.2-15.5 gave better mileage and drove better.
Also with cars that have idle problems from intakes having the O2 off makes them idle much smoother. The Maf and O2 seem to start fighting each other. set the idle O2 in the 13.9-14.5 range
Also setting the maps to lean will also cause the car to drive like crap when its cold.
On my car on gas I got a avg of 26mpg on my 1500mi trip with one tank right at 29mph on a flat section.
On E85 I have my car tuned to a 15.5-16.0 AFR and it gets about 22mpg on the hwy cruse.
Even on my 1500mi trip with a few mt passes my AFRS were always with in 15.0-15.5 so the stock Ecu does great with the right fuel adj for different conditions. I always run Chevron 92. I guess if you were switching different gases a lot like some with 10% alc and others with out you may really need the O2 to keep things in check.
Jul 11, 2007, 09:26 PM
#43
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I've been running in open loop for the past few months myself. I increased the coolant temp needed to reach closed loop to 103 deg C, I believe. The car does throw a CEL that cannot be held off by a C-reader or the like. I have leaned everything out up to about 90-100 load to ~15.5-16:1 or so, this includes rpm ranges over 3500 and my car has absolutely no problem with misfires in the 3500-4k range. The car drives exactly as it did before, there are no knock counts under load or during tip in. Fuel economy is GREAT. My tires are set to 38 psi all around, my wing is removed, and I average 300 miles to a tank (until the light comes on is considered a tank for me, approx 11.5-12 gallons added each and every time) doing a solid 85 mph the entire trip. I've averaged this time and time again. Very, very happy with fuel economy now.
Last edited by A418t81; Jul 11, 2007 at 09:31 PM.
Jul 11, 2007, 09:43 PM
#44
A418, rather than use the minimum temp for closed loop method you might just set the open loop load #1 and #2 map. You wont get a CEL that might prevent you from seeing CEL for something you would like to see. Both tables directly refer to load % so if you want to enter open loop ONLY on the highway you could set them to 50% (approx average for highway cruise) or less if you want to idle lean.
Jul 12, 2007, 06:39 AM
#45
John, can you explain how the Open Loop Load #1 and #2 tables work? What I mean is when does the ECU use one or the other? If I understand what you've said correctly, this means that the stock fuel map is largely unused/unnecessary under a load of about 90 (down to 50 at higher rpms). This assumes you have the stock values of course. Funny enough, this is the portion of the map that simply has 14.7s in it. 