5th Gear Member
Join Date: Mar 2004
Location: Richmond Hill, Ontario
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Do you want to hear the truth or only what you want to hear? First of all your M3 exhaust isn't an improvement over your stock one. You need to properly match the exhaust pipe size of your exhaust to the headers, otherwise it's useless. And like I mentioned before, having the stock cats on restricts the airflow, without removing the cats or using a hollowed out racing cat, the larger headers are useless.
I have a friend with a 325is 5 speed who has Supersprint headers, Supersprint cat back exhaust, hollowed out cat and a Supersprint performance chip. Guess what? His car is slower than my 318. The reason behind it is you loose a lot of back pressure, you push all your power to high end at WOT (Wide Open Throttle) and you loose a crap load of low end torque.
You can ignore the facts and just believe what the manufacturers tell you. 15HP gain! Think again. Even if you somehow manage to gain 15HP, it would undoubtedly be at 5000-6000RPM. The most important thing you should think about when tuning your motor. Torque is easily traded off for Horsepower, but Horsepower is not so easily traded off for torque. You'll end up with a motor that you have to rev up high everytime to get power. Honda is the perfect example of a no torque lots of high end HP motor. Good for track, very poor for city driving. If that's what you want, then by all means.
Why do you think you need larger exhaust manifolds? Is that a restriction in your motor? What "other" modifications have you done in your car to require you to upgrade your manifolds? Put some serious thought into it. At $800USD for those headers there's definitely something else more worthit you could buy. Plus, buying no name brand headers or incorrect diammeters would ultimately make your car slower. If German engineers could increase your motor by 15HP just by adding a larger header, they would have done it already.
Not trying to put you down, but in real life it's not that easy. intake (5HP) + exhaust (10HP) + headers (15HP) + chip (10HP), wow I've already got a total of 40HP, who needs a turbo!? :wink
<u>1994 M-Technic M42 Saloon - Trillium Chapter - 5130
</u> Stock - 2866lbs Current - 2670lbs
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