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Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons Bolt-Ons | Intakes | Exhaust

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Old 09-21-2010, 09:21 AM   #1
Larz29
 
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Bad gas mileage with new exhaust on SS LS3

So I just installed a flowmaster cat back exhaust this past weekend, then reflashed my diablosport predator 93 tune. I noticed a noticable performance gain, but my gas mileage tanked.. Before the exhaust i was averaging 16.5 mpg with all in town driving, and now by driving very very nice I'm barely getting 15 mpg.

Seriously everyone I talked to said my mileage would improve with a tune and aftermarket exhaust, and CAI... Not the case with me! LOL.

Do I need a custom tune? Any ideas? Thoughts?
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Old 09-21-2010, 10:32 AM   #2
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If you really are getting that much worse gas mileage it has to be something wrong with the tune. I'd contact them for help for sure.
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Old 09-21-2010, 10:42 AM   #3
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Actually getting worse gas mileage is fairly common. Not because of the mods and the tune but because humans subconsciously change their driving habits without realizing it after during such mods.
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Old 09-21-2010, 10:46 AM   #4
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Actually getting worse gas mileage is fairly common. Not because of the mods and the tune but because humans subconsciously change their driving habits without realizing it after during such mods.
I agree..people dont realise but they tend to stomp on the gas pedel just so they could hear their exhaust and that causes them to get bad gas mileage...
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Old 09-21-2010, 10:50 AM   #5
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So just have your dog drive it and you won't lose any gas mileage
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Old 09-21-2010, 11:00 AM   #6
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I definitely agree with the above posters saying that it's prolly you or the way you drive that changed since the mods. It makes sense that with a new tune and better sounding exhaust you would give it more gas than normal.

A good test would be cruising on the highway, not in town where driving habits and traffic can greatly affect the mileage. How can you be sure that you didn't hit extra traffic or a few more lights? At least on the highway cruising at 65mph is the same everyday.
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Old 09-21-2010, 11:05 AM   #7
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In town driving with so much stop and go is not a very accurate measure of mpgs.

Plus, more power = more fuel. You put in a performance tune. If you put in an mpg tune, I'd be concerned with the results. You put in their most aggressive tune which ups the fuel and spark for more power on premium fuel.

I'd bet your throttle response feels snappier. I think they tinker with the throttle reaction table to make the actual engine throttle react faster to the gas pedal moving. Making the throttle open faster will not improve the mpgs.

I've used that tune before and it does have a real nice throttle response to it, at the price of a little more fuel. Which if you are performance tuning, is the expected result.
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Old 09-21-2010, 11:28 AM   #8
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Originally Posted by Sevn86 View Post
I agree..people dont realise but they tend to stomp on the gas pedel just so they could hear their exhaust and that causes them to get bad gas mileage...


I also installed cat back Flowmaster and noticed I was visiting the gas station more often.

Can't help it, the sound makes you want to....
M
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Old 09-22-2010, 08:41 AM   #9
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Also I would wait a tank of gas before noting gas mileage especially if you put in a new tune.
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Old 09-22-2010, 08:47 AM   #10
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Originally Posted by Mark Myles View Post


I also installed cat back Flowmaster and noticed I was visiting the gas station more often.

Can't help it, the sound makes you want to....
M

Same here !!!

I think 15mpg is pretty good ...
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Old 09-22-2010, 08:48 AM   #11
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Yeah, I put Flowmasters on my 4.6 Mustang, and mileage went down right away. Just couldn't get enough of that V8 sound.
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Old 09-22-2010, 08:49 AM   #12
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I have to say I agree. Try this lower your back seat down, you will hear the exhaust a lot more than normal, and I found myself enjoying it too much!

Quote:
Originally Posted by Sevn86 View Post
I agree..people dont realise but they tend to stomp on the gas pedel just so they could hear their exhaust and that causes them to get bad gas mileage...
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Old 09-22-2010, 11:07 AM   #13
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You have shot your powertrain warranty by installing a tune. Spending a couple of $$ more on gas should not be a big deal. just sayin..
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Old 09-22-2010, 11:29 AM   #14
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Driving very very easy on it in the City Iam 13-14 ... it's not driving habits (when you watching the MPG Gauge and trying to see your Best Milage you can get) .. The OP states he was also trying to see his best milage by driving very easy on it. After you see what you can get then you drive like you really should be.
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Old 09-22-2010, 02:34 PM   #15
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Sounds about right to me.As long as your not driving like a 'Jessie', i've come to not expect much more in,short trip and town driving.
Best MPG is arrived at using 'cruise',that does'nt suit me as no roads are longer than about 10 miles in the U.K.!
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Old 09-22-2010, 02:45 PM   #16
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Quote:
Originally Posted by Mr_Draco View Post
Actually getting worse gas mileage is fairly common. Not because of the mods and the tune but because humans subconsciously change their driving habits without realizing it after during such mods.


love that new exhaust sound? love the increased performance? drive with a heavier foot?
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Old 09-23-2010, 11:26 PM   #17
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what is your average MPG overall ?
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Old 09-24-2010, 05:57 AM   #18
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If you're gonna dance to the music, you gotta pay the band!
Don't worry about it; some people are paying $1 for a bottle of water! At least, you're getting to hear something, and gettin' there faster.
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Old 09-24-2010, 11:56 AM   #19
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Quote:
Originally Posted by Larz29 View Post
So I just installed a flowmaster cat back exhaust this past weekend, then reflashed my diablosport predator 93 tune. I noticed a noticable performance gain, but my gas mileage tanked.. Before the exhaust i was averaging 16.5 mpg with all in town driving, and now by driving very very nice I'm barely getting 15 mpg.

Seriously everyone I talked to said my mileage would improve with a tune and aftermarket exhaust, and CAI... Not the case with me! LOL.

Do I need a custom tune? Any ideas? Thoughts?
Easy on the right foot!
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