Cat Back, MPG & HP
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Racer
Joined: Dec 2004
Posts: 276
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Cat Back, MPG & HP
Installed cat back ( Borla ) . My MPG has dropped by 2MPG and I can not feel the additional 10% increase in HP they say I should get 
Any one else had a similar experiance / comment?? Thanks.
Any one else had a similar experiance / comment?? Thanks.
Melting Slicks
Joined: Feb 2004
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From: I finished a Marathon, did you? Michigan
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I don't think you can gain 10 hp from just a cat back exhaust. I may be wrong, but how can you gain hp when the air is still restricted/the same coming out of the engine(headers)???? I hope someone will chime in if I am wrong. Thats why I did the Headers and Exhaust together I know I did get an increase in hp but I will have to wait until next week or so to find out how much.
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If you're a 6-speed, the mpg loss is due to downshifting to hear the exhaust and staying in a lower gear longer to enjoy the exhaust note. I know that sounds silly but it's true. If you're an A4, I'd guess it has to do with hitting the pedal a little harder at stop signs to hear the sound 
As for 10hp gain. That might be true if custom tuned after install. But 10hp bulk = roughly 8hp at the rear wheels. Not something you'll feel in the seat of your pants (sotp)
I didn't notice any sotp gains until after the headers and custom tuning. (see sig). But the personality of the car changed dramatically with the headers. I drove one car into the shop and drove out in something completely different.
:
$0.02
Michael
As for 10hp gain. That might be true if custom tuned after install. But 10hp bulk = roughly 8hp at the rear wheels. Not something you'll feel in the seat of your pants (sotp)
I didn't notice any sotp gains until after the headers and custom tuning. (see sig). But the personality of the car changed dramatically with the headers. I drove one car into the shop and drove out in something completely different.
:$0.02
Michael
Last edited by WellAdjusted; Mar 6, 2005 at 08:32 PM.
Le Mans Master
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No sotp gain with the Stingers. I can tell you the loss of MPG is because like the rest of us you love hearing those Stingers scream. I didn't feel the gain until I did the intake. The LS1 is starving for air with that little bitty hole in the original airbox.
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You might get a little bump in HP with a cat back, but it won't be enough to write home about. No way there will be 10%. You should not lose 2 mpg with just the mufflers being changed. Perhaps a different driving style is the reason. 
