Johny GTO

Ok. I read about guys who have done Heads, cams, headers, intake, etc on their LS1 and LS2 powered cars talking about they get 25mpg and **** like that, and it has got me thunkin. I get kinda **** poor gas mileage. Now, i wanted power out of my motor, and i didnt go modding it to get better gas mileage. However, it seems like my gas mileage is a good bit lower than a lot of fellas who have done similar mods. I am sure the cam has a lot to do with it, but still. Also, getting low gas mileage could be due to running rather rich, or not enough timing, which means i am leaving power on the table. So i could use some help.
i am curious if there is something off about my tune perhaps?

Here is my setup....
2006 LS2 GTO M6
-dart 225 ported and polished heads from PM-FL (Bob)
-Ed Curtis Street Sweeper 236-240 .610 .610 111LSA cam
-Full cam kit with dual springs and all that bullshit
-kooks 1-7/8th long tubes with no cats
-custom H-pipe, no reasonator.
--Gone through like 5 exhausts, from stock, to straight piped, to sweet thunders, and on and on until what i have now, which is true duals with flow master super 40's near the 04 position.
-Vic Jr. intake with custom elbow and 90mm throttle body
-new fuel rails (cant recall what kind)
-46 or 48lb-hr injectors, maybe even 52lb injectors. i cant recall.
-Catch can from Mike Norris.
-Drag bags.
-Aza wheels 18x8 front and 18x9 with 285's in the rear.
-home made CAI that actually works well. Dash-hawk has IAT within 10 degrees of ambient, sometimes closer.

install was done by mike norris, along with the initial tune. Originally, it was still running the stock ls2 intake when i had everything else done. Reason being was that i had someone back out of a deal to buy their FAST90 intake. with the heads, cam, headers, etc running witht he stock ls2 intake and a tune that was "a bit rich", it put down about 435rwhp and 400 rw trq. The thing ran great, no surging or bucking or anything except at real low rpms (like 40mph in 6th). It felt much more powahful. It did smell like it was running rich though. Idled around 900, which i didnt really care for. Overall though it was nice.
SOon after, i installed the Vic Jr intake and elbow with a board member and had it retuned at PMFL by Bob. He leaned it out a bit, etc. Did a street tune for about 30 minutes. Said the tune was pretty good, that he didnt have to do much. He lowered the idle to where it is now (about 700 rpms) and it idles beautifully, never dies, always starts right up on the first try cold or hot, etc. Got rid of nearly all of the small, residual bucking that happened at low rpms. When i drove it, it felt like a new car again! Much more powerful than the first time it was modded (heads, headers, cam, etc). The intake made a huge difference, and i do not have a sensiitive butt dyno at all!! My butt dyno doesnt notice anything under a 30-40hp change it seems, but i could feel the difference the intake and re-tune made.

The car drives beautifully. I mean, my mother can drive this thing with no problem. You could teach people to drive stick with this car, and thats with a 236-240 cam 111LSA cam, which from what i see is not very common. It is very well behaved, yet has hella powerful.

MY only complaint is my MPG. I average about 13 to 14mpg. I dont beat on the car which would kill the gas mileage. I dont tear *** all over the place (tickets stopped that). But i dont drive like a grandma either. If i reset the MPG calculator while driving on the highway, i average about 18-19mpg while doing 80mph on the highway. I know the large over-lap and the rather largish cam have a lot to do with it, but it seems like that is still too low. I dont have HPtuners or anything to check my tune.

What do you guys think? Perhaps i can get ahold of Bob @ PMFL and have him send me or post my tune file. he should still have it, and it hasnt changed since i saw him.

That should show if my car is running rich, or if my timing is off, ow whatever tuning issues could cause shitty gas mileage and leave power on the table.

Is there anyone local (Im in south florida, coral springs to be exact, but dont mind travelling a lil) with hptuners and some skill that would mind taking a look at my tune and fixing it up if you find issues? I dont have the cash to bring it to a shop to get a whole nother tune done, but i could buy a good samaritan a steak dinner and beer

WeathermanShawn

iTrader: (1)

I would imagine with a heavier car and all those HP mods, it might not be that abnormal. Especially steeping up to bigger injectors.

I would double-check with your tuner. If you are running closed-loop (with O2's) you should not be rich. Is your car set-up to have Trims enabled?

Not second-guessing your set-up, but you would have to do a lot of redesign to get it to be more conservative on gas mileage. My 'guess' would be tune, and double-checking the injector flow rate for your combo.

Good luck.

..WeathermanShawn..

Johny GTO

thanks sean. I am going to contact Bob@pmfl and see if he will email me my tune file.
hopefully someone can take a look at it, preferably locally so that if something is "funky" it can be touched up.