Bad gas mileage after tuning
03-23-2006, 04:56 PM
#1
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Bad gas mileage after tuning I had been driving with the mods in my sig on the stock tune for almost 2 months and even without it tuned I was getting about 14 mpg in city and 20-22 on the highway.
Now, I have pretty much only messed with my idle tuning and a few other small things tuning wise. but I'm getting about 12 mpg (1/2 hwy 1/2 city) now! Any ideas on what could be wrong or what I need to check?! Thanks
Tyler
Now, I have pretty much only messed with my idle tuning and a few other small things tuning wise. but I'm getting about 12 mpg (1/2 hwy 1/2 city) now! Any ideas on what could be wrong or what I need to check?! Thanks
Tyler
03-23-2006, 05:06 PM
#2
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setting any codes? what codes did you disable? (any front O2 codes?)
When tuning did you turn your MAF off or unplug? if so did you reenable after you were done tuning?
When tuning did you turn your MAF off or unplug? if so did you reenable after you were done tuning?
03-24-2006, 10:02 AM
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here's a link to my thread on the HPTuners forum. I have a normal log from last night posted at the bottom.
http://hptuners.com/forum/showthread.php?t=5225
http://hptuners.com/forum/showthread.php?t=5225
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03-24-2006, 10:18 AM
#8
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hrmmm... can you add your .hpt file to that also?
The O2 readings look weird... it's fine for a while then has periods where it's going pig rich w/out a reason ... then when there's minor load it doesn't appear to be switching around .500 at times
Overall though the car looks to be running too rich and for some reason the fuel trims aren't bringing down enough ... if you post your .hpt up I'll go through it (as can others) to see if there's anything that is set wrong
The O2 readings look weird... it's fine for a while then has periods where it's going pig rich w/out a reason ... then when there's minor load it doesn't appear to be switching around .500 at times
Overall though the car looks to be running too rich and for some reason the fuel trims aren't bringing down enough ... if you post your .hpt up I'll go through it (as can others) to see if there's anything that is set wrong
03-24-2006, 10:21 AM
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!EGR -is- going to cost you some MPG at light cruise. It
has two roles, NOx suppression and some reduction of
nearly-closed-throttle pumping losses.
Bringing PE in earlier, or fatter, would of course also
cost you economy. This is where you trade off leaner
enrichment for lower spark advance. However using PE
as the primary enrichment element limits you, you may
need to concentrate on the OLFA table for the part
throttle, mid-MAP enrichment (which is where you live,
on the street) and use the PE vs RPM only for high-RPM
"upside" while using OLFA for main fuel mapping but have
the PE enable stuff set to put you there (open loop but
largely not-PE, because PE < OLFA if you set it up that
way) to get just-enough enrichment in street driving.
Be sure you are not simply fighting coincidences, like the
!X, !Y, !Z mods just happen to be about the same header
swap that depressed your front O2 readings which is the
real source of mis-fueling / mis-editing of VE tables, or
something like that. You can go a long way into the weeds
if you rely upon corrupted sensor data.
has two roles, NOx suppression and some reduction of
nearly-closed-throttle pumping losses.
Bringing PE in earlier, or fatter, would of course also
cost you economy. This is where you trade off leaner
enrichment for lower spark advance. However using PE
as the primary enrichment element limits you, you may
need to concentrate on the OLFA table for the part
throttle, mid-MAP enrichment (which is where you live,
on the street) and use the PE vs RPM only for high-RPM
"upside" while using OLFA for main fuel mapping but have
the PE enable stuff set to put you there (open loop but
largely not-PE, because PE < OLFA if you set it up that
way) to get just-enough enrichment in street driving.
Be sure you are not simply fighting coincidences, like the
!X, !Y, !Z mods just happen to be about the same header
swap that depressed your front O2 readings which is the
real source of mis-fueling / mis-editing of VE tables, or
something like that. You can go a long way into the weeds
if you rely upon corrupted sensor data.
03-30-2006, 12:00 AM
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Well when you're sitting in the driveway working on the idle tune you're not racking up many miles are you?
Unless you did controlled test loops before and after, then you really can't say your mileage changed.
Things like outside air temperature, tire pressure, and % time idling create a good deal of error there.
Unless you did controlled test loops before and after, then you really can't say your mileage changed.
Things like outside air temperature, tire pressure, and % time idling create a good deal of error there.
