MPG update -> After PCM tuning
08-26-2008, 05:15 PM
#11
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Join Date: 06-29-2008
Location: Tennessee
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Leaner than 14.7:1 may also damage your valves, but... I don't believe it is possible to tune part-throttle operation A/F ratio-- the ECM works with the oxygen sensor to achieve as close to optimal (14.7:1)A/F ratio in real time as it can once you're in closed loop (coolant temp beyond a certain temp threshold). If you've ever watched a real time scanner you can see the oxygen sensor at work. The O2 sensor in front of the catalyst is for A/F ratio the O2 behind the catlyst is for emissions monitoring. A/F ratio tuning is usually only for WOT (Wide Open Throttle) operation. Playing with spark advance parameters in the ECM is a different story, but this can also lead to a need to burn premium fuel.
The Buick GNs from the 80's had a "lean burn" mode. I agree that going too lean can burn valves (and other issues), but we're not talking about going "too lean".
In fact, I'm betting the MPG gains come from optimizing cruise timing, rather than AFR, since as you say it would be hard to tune closed loop (though not impossible).
From my LT1 owning days, I did my own tuning with LT1 edit. By altering the MAF table or the injector constant you can indeed really lean out or richen up the car, even in closed loop, all the way through the RPM range or even at specific places (using the MAF tables modified at specific grams/sec ranges).
I know theoretically the PCM compensates, but there appears to be a limit beyond which it can't recover.
08-26-2008, 05:17 PM
#12
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Join Date: 06-29-2008
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has anyone verified these milage increases? the DIC can be tampered with by modifying the injector tables for its display, therefor causing high or low numbers at will. I would definately verify miles driven vs. gallons to full and calculate it myself. even gaining 1-2mpg is difficult, let alone 5...
Not exactly sure where all the skepticism is coming from. I'm just sharing what my results are, I have no agenda here.
In the interest of full disclosure, however, I will say Vince is a sponsor at my forms (see signature). I paid the equivalent of full price for my tune, however. His sponsorship payment was due a couple weeks ago and we agreed to deduct the full price of the tune from what he owed me.
08-30-2008, 06:33 PM
#13
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Join Date: 03-08-2008
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I am intersted in this if it can be verified
I am interested in this if it can be verified. Someone do an independent test with before and after on similar trips.
Then if it can ve verified I would like to know what all they do and how much it costs.
I bought my HHR for the sole purpose of saving money on gas. My one ton four dour dually was killing me on gas. If I could save 5 MPG on an already decent mileage I would be thrilled. Bruce
Then if it can ve verified I would like to know what all they do and how much it costs.
I bought my HHR for the sole purpose of saving money on gas. My one ton four dour dually was killing me on gas. If I could save 5 MPG on an already decent mileage I would be thrilled. Bruce
09-18-2008, 07:47 AM
#14
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Chris, how is your mileage now?
Chris, How is your mileage now? I would like to know more about how well it worked and if you have made any other mods. I plan on doing the Trifecta tune to in addition to a few other mods. Thanks, Curly
09-29-2008, 07:42 AM
#17
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But keep in mind here we're talking about low load, low RPM, part throttle MPG gains. I agree it would be a DISASTER to lean out WOT on a Turbo motor (or any motor for that matter), but remember as I mentioned before even the legendary Buick GN had a "lean burn" highway mode.
09-29-2008, 08:17 PM
#19
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My tune took me up close to 2 mpg also for my commutes. I have not been out for a trip as of yet and I have a Trifecta Tune and am also a Installer/Dealer for Vince.
Stick might pop in and give his impression of his Trifecta Tune installed over the weekend.
Stick might pop in and give his impression of his Trifecta Tune installed over the weekend.
09-30-2008, 06:07 AM
#20
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Mileage and performance can be increased
Mileage and performance can be increased with out leaning it out. There are many other variables other than fuel ratio such as timing advance that help.
It is never good to lean out a motor.
It is never good to lean out a motor.