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Originally Posted by teen ti i'm doing this to achieve results similar to a sport exhaust system that would run me $400+ for considerably less |
An aftermarket exhaust system only has two benefits for these cars. The first and most obvious is sound. Straight pipes will not accomplish this. In fact, it'll just make your car sound like a riced out piece of crap, thus making you look like a doucher everywhere you go. The only other benefit of aftermarket exhaust is weight savings. The stock exhaust is rather bulky. However, it's positioned in the best possible spot for something of it's size and weight. Low and over the rear wheels. If your goal is weight reduction, there's about a dozen other things that could be addressed before ghettofying your German engineered auto with some cheap ass hillbilly bs.
A NA 1.9L 4 banger is not going to growl like a V8 no matter what kind of exhaust you're running. If anything, there's only 2-5hp max to be gained by installing a QUALITY aftermarket exhaust that has been designed and engineered specifically for our cars. However, whatever you gain on the high end, you're sure to lose on the low end. So while your engine may "breathe" better at high RPM's, it'll "gasp" at low RPM's. In other words, you'll lose low end torque which will cause your car to be sluggish off the line.
Are you considering deleting the catalytic converter? If so, keep in mind it's a $1500 part. So right off the bat, you're decreasing the value of your car significantly. Besides being illegal, your car will not pass inspection and potential buyers can sue you if you do not disclose the fact that you've deleted a critical part of the vehicle's emission system. Before you say that your state doesn't test or you know a place that will cheat the system, it's a FEDERAL law. The EPA is a federal agency and regardless if certain states test, removing or altering any part of a vehicle's emission system that is to be driven on the highway is illegal and punishable by healthy fines and/or possibly jailtime.
Let's say you ignore what I've already layed out and you decide to do it anyway. So now your car is annoyingly loud, runs like crap since the o2 sensors aren't giving ACCURATE readings and the engine is running too lean or rich aside from being a slug off the line from loss of low end torque, resale value and fuel economy have gone out the window since nobody wants to buy a car from some teenager who has molested it with ghetto/hack mods and the only attention you'll draw aside from the cops will be people looking at you thinking you're just some cheap ass idiot teenager driving a de-valued BMW. All so you can THINK you're cool when you tell your friends "my BMW has straight pipes..."
Your car is not going to be any faster and you're not going to look any cooler. But hey, do what you like, that's just my opinion.
BTW FWIW, there's been reports from people with supercharged 318ti's who tried running 2.5" catbacks, only to find out that they lost a significant amount of low end torque. That's with a FI setup, imagine how a free flowing system will affect a NA motor.