Gas Mileage worse after tune???? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

bnsmith78 · 10-15-2010, 10:37 AM

I have a SS CAI and Corsa Catback. I received an HP tune and now it seems I lost about 2miles per gallon. I was averaging about 17, now about 15. I thought it would gain.........Maybe I am driving it harder because it is so smooth and easier to get up to higher RPM's.... ?? Any thoughts?

motorhead · 10-15-2010, 10:41 AM

As long as the tune made it faster does it really matter?

zebra · 10-15-2010, 10:45 AM

it depends on what it was tuned for. if you're pulling more power from the engine, you're more than likely not gonna get as great of gas mileage. on the flip side, you can tune for great gas mileage & lose a bit of pep in the go pedal.

but it could also definitely be that you've had your foot in it. i can personally tell you that my gas mileage is better now than last year when i first swapped a bigger engine in the truck

*GTAHVIT* · 10-15-2010, 12:13 PM

Most likely it's your driving style.

Even with the supercharger my average MPG stayed close to 21.

baby it for a tank or 2 and see if it bumps back up.

Jessika · 10-15-2010, 12:22 PM

Before my MagnaCharger I had my G8 tuned for performance and headers. My fuel economy dropped from 16-17 to 12- 13MPG.... After the MagnaCharger & retune my fuel economy jumped up to 19-20 AND I gained 1 second in the 1/4 mile.

I have always (and still do) driven it like I stole it EVERYWHERE I go.

Frost · 10-15-2010, 02:54 PM

It's NOT normal to lose mileage after a tune; quite the opposite.

4xchamp · 10-15-2010, 09:05 PM

I think I also lost fuel mileage , a clutch and rear tires after my mods and a good tune .

2SSCAMARO · 10-16-2010, 10:34 AM

Quote:

Originally Posted by bnsmith78

I have a SS CAI and Corsa Catback. I received an HP tune and now it seems I lost about 2miles per gallon. I was averaging about 17, now about 15. I thought it would gain.........Maybe I am driving it harder because it is so smooth and easier to get up to higher RPM's.... ?? Any thoughts?

Have you done any logging to check the long term fuel trims. Your long term fuel trims can and do affect the MPG's. The LTFT's should be set slightly negative (or slightly rich). Positive (lean) trims will cause the ECM to add additional fuel to the open loop/PE tables during WOT. I would do a cruise log to check the LTFTs. You need to find a nice long stretch of flat highway such as an interstate. With all temps up to normal, drive at a steady cruise about 2000 RPMs and log the LTFT's. If you find that the LTFT's are off, setting them properly should help improve the MPG's.

06MonteSS_2 · 10-16-2010, 10:38 AM

yeah.. sounds like your fueling wasn't adjusted correctly for part-throttle driving...

you shouldn't have lost mileage... at worst, it would have stayed the same, but you should have gained some mpg if it was done correctly...

BowlingSS · 10-25-2010, 01:12 PM

If you were running lean before the tune I would think after a tune to get the trims/ve table right you would lose mileage. Does anyone buy these cars for gas mileage? I do not.

Bill

Frost · 10-26-2010, 10:21 AM

Quote:

Originally Posted by BowlingSS

If you were running lean before the tune I would think after a tune to get the trims/ve table right you would lose mileage. Does anyone buy these cars for gas mileage? I do not.

Bill

If the car is 5% 'lean', then a 5% positive trim offsets, so it never is lean. Stoich is always the result. The only place it's not is in transitives. That's what trimming is for.

BowlingSS · 10-26-2010, 12:19 PM

Quote:

Originally Posted by Steve@TunedbyFrost

If the car is 5% 'lean', then a 5% positive trim offsets, so it never is lean. Stoich is always the result. The only place it's not is in transitives. That's what trimming is for.

Thanks for the info. My last 2001 Camaro I was running OL Speed Density (no MAF) and had a Custom OS (COS5) from EFILive. I did not have trims, most of the tunning was with the VE table.

Bill

Frost · 10-26-2010, 01:06 PM

COS5 allows for semi-OL ... you can use trimming in some spots if you wish and not in others. The flexibility is definitely nice, especially for large cammed cars and/or large injectors that get fussy at lower IPW's. I like to allow CL in the cruise area on most street cars to help preserve the mileage. Going full time OL puts your mixture into the hands of the flawed IAT/ECT bias and makes you susceptible to heat soak issues with the IAT. If you try and use the IAT modifier to correct heat soak, it will cause issues with legitimately warm IATs. I prefer to relocate the sensor out of the engine compartment on these arrangements.

FRANK121 · 11-04-2010, 03:53 PM

Since my tune I have been averaging around 12 to 14mpg around town and maybe 16 to 18mpg highway

I guess that annoying AFM really was working before

To be fair, my daily drive is about 5 miles one way to work and cruise around town when needed. Our longest highway trip since the tune has been may 30 miles?

10-15-2010, 10:37 AM	#1
bnsmith78 Drives: 2011 IOM SS Corsa/CAI Join Date: May 2010 Location: Shawnee, KS Posts: 190	Gas Mileage worse after tune???? I have a SS CAI and Corsa Catback. I received an HP tune and now it seems I lost about 2miles per gallon. I was averaging about 17, now about 15. I thought it would gain.........Maybe I am driving it harder because it is so smooth and easier to get up to higher RPM's.... ?? Any thoughts?

10-15-2010, 10:45 AM	#3
zebra just can't seem to leave Drives: your mom wild!! Join Date: Oct 2008 Location: cold & windy Posts: 10,625 View My Garage	it depends on what it was tuned for. if you're pulling more power from the engine, you're more than likely not gonna get as great of gas mileage. on the flip side, you can tune for great gas mileage & lose a bit of pep in the go pedal. but it could also definitely be that you've had your foot in it. i can personally tell you that my gas mileage is better now than last year when i first swapped a bigger engine in the truck __________________ Eve ('00 FRC): hot-air intake Rowan ('09 H3): 5spd mom-mobile Penny ('99 Sierra): 5.3 / HD 5spd... gone but not forgotten Samson ('18 HD): compounded 408

10-15-2010, 12:13 PM	#4
GTAHVIT Blessed Drives: 2013 Sonic RS MT Join Date: Dec 2007 Location: Saint Augustine FL Posts: 28,441 View My Garage	Most likely it's your driving style. Even with the supercharger my average MPG stayed close to 21. baby it for a tank or 2 and see if it bumps back up. __________________ Click image to see build thread. PQ - "the love of cars. It's a boys first step toward manhood and a mans last hold on boyhood." Fbodfather - "We do not want to use the Z28 moniker on a car that does not deserve this hallowed name." The_Blur - "Let's not confuse competitors with equals."

10-15-2010, 09:05 PM	#7
4xchamp MURC 666 Drives: 69 Pace Car 68 Camaro Restomod 81 Z Join Date: Jan 2010 Location: New England , U.S.A. Posts: 480	I think I also lost fuel mileage , a clutch and rear tires after my mods and a good tune . __________________ Guys hoarding their Camaros are depriving some youngster the opportunity to restore it 25 years from now . Drive it like you stole it , let the next guy baby it !

11-04-2010, 03:53 PM	#14
FRANK121 Drives: 2022 Camaro ZL1 Join Date: Sep 2010 Location: Sullivan, Missouri Posts: 653 View My Garage	Well Since my tune I have been averaging around 12 to 14mpg around town and maybe 16 to 18mpg highway I guess that annoying AFM really was working before To be fair, my daily drive is about 5 miles one way to work and cruise around town when needed. Our longest highway trip since the tune has been may 30 miles? __________________ 2022 Black ZL1 RotoFab CAI, AWE Touring Edition Cat Back Exhaust. 665 Crank hp. est. and 660 Crank ft. lbs. est. Never been Dynoed

10-15-2010, 10:41 AM	#2
motorhead Drives: Love the one you're with Join Date: Sep 2009 Location: Downtown Charlie Brown Posts: 11,849	As long as the tune made it faster does it really matter?

10-15-2010, 12:22 PM	#5
Jessika Account Suspended Drives: Anything Blown Join Date: Aug 2010 Location: SoCal Posts: 1,194	Before my MagnaCharger I had my G8 tuned for performance and headers. My fuel economy dropped from 16-17 to 12- 13MPG.... After the MagnaCharger & retune my fuel economy jumped up to 19-20 AND I gained 1 second in the 1/4 mile. I have always (and still do) driven it like I stole it EVERYWHERE I go.

10-15-2010, 02:54 PM	#6
Frost Drives: GM anything Join Date: Sep 2009 Location: Tuning GM in Richmond VA Posts: 147	It's NOT normal to lose mileage after a tune; quite the opposite.

10-16-2010, 10:38 AM	#9
06MonteSS_2 Account Suspended Drives: 2006 Monte Carlo SS Join Date: Jul 2010 Location: CT Posts: 41	yeah.. sounds like your fueling wasn't adjusted correctly for part-throttle driving... you shouldn't have lost mileage... at worst, it would have stayed the same, but you should have gained some mpg if it was done correctly...

10-25-2010, 01:12 PM	#10
BowlingSS Camaro Owner Since 1987 Drives: 2011 2SS/RS L99 RJT Join Date: Jun 2006 Location: Lawrenceville, GA Posts: 2,185	If you were running lean before the tune I would think after a tune to get the trims/ve table right you would lose mileage. Does anyone buy these cars for gas mileage? I do not. Bill

10-26-2010, 01:06 PM	#13
Frost Drives: GM anything Join Date: Sep 2009 Location: Tuning GM in Richmond VA Posts: 147	COS5 allows for semi-OL ... you can use trimming in some spots if you wish and not in others. The flexibility is definitely nice, especially for large cammed cars and/or large injectors that get fussy at lower IPW's. I like to allow CL in the cruise area on most street cars to help preserve the mileage. Going full time OL puts your mixture into the hands of the flawed IAT/ECT bias and makes you susceptible to heat soak issues with the IAT. If you try and use the IAT modifier to correct heat soak, it will cause issues with legitimately warm IATs. I prefer to relocate the sensor out of the engine compartment on these arrangements.

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