EXHAUST SYSTEMS
The story with exhaust systems is much the same as above, a standard exhaust has two jobs,,,,,take the gasses to the rear of the car where there is less chance of gasses entering the car and to keep the sound levels down.
They tend to be small in diameter, very restictive and rob the engine of torque.
when choosing an exhaust for a car it helps first to understand a few things about what will help the most to gain more torque and bhp - (n/a only)
1. When it comes to N/A engine without a turbo bigger is NOT better, if you think otherwise take your car to a rolling road and try your 3" pipe and compare it too a 2" pipe, the torque will be massivly altered and so will your view on the matter.
2. The best way to increase torque is to have medium sized pipeing (for a 2.0l 16v engine around 2") this will ensure there is no restriction but more importantly than that (the bit people dont no) is that the smaller pipe will flow the gasses much faster meaning a vacume will be caused by the momentum of the fast flow of gasses at the next cylinder about to release exhaust gasses and this will cause whats called a scavange effect on that cylinder meaning it will help pull out old inurt gasses and pull more fresh charge in while the valves or on overlap,,,meaning loads of extra torque!
3. Smooth bends (mandral are best) will keep gasses flowing fast and smooth so it doesnt restrict the engine.
4.Modern quality back boxes have a straight through design which causes hardly any resistance and use a wool like material to absorb the sound on the way through, if you come across a box that doesnt have this design dont buy it! it will hold you engine back.
5. In an ideal world wrapping your entire exhaust system with heat lagging will give gains in bhp!! why??,,,,,beacause by doing so the gasses in side do not loose energy to heat escaping through the metal and allowing the gasses to slow down, inturn the gasses will travel through the exhaust faster.
6.Removing the cat from your exhaust will more than likley improve the bhp because the cat tends to be the most restrictive part of an exhaust.
