many people say that a larger diameter exhaust does not help the power situation, because need some exhaust blowback (then again some people say blowback decreases effieciency :confused:) looking at at rover 220 turbo with no custom exhaust so would be looking to increase bhp by about 5-10, what would be the ideal diameter for the powerflow guys to fit. thanks! :)

2.5 inch max i would say.

dont think turbo's suffer as much.

2.5 inch max i would say.

dont think turbo's suffer as much.

The turbos should benefit from better exhausting, mainly from an internal temperature and pressure point when running higher levels of boost, it should allow hot gasses to escape quicker and thus keep the pistons that tiny little bit cooler. The NASP K-Series doesn't benefit from a free flow exhaust at all, before anyone asks.

basiclly backpressure gives your tourque and big (to a point) gives you power, too big and you loose power, too small and the engine is restricted, not sure about the 220 but on my 214 a 2" exaust with a rover 800 2.5 v6 cat seems to give quite a bit of power, but there is less torque

the 2" exhaust is however a scorpion one off a 220 turbo and turbos certainly tend to need larger exhausts as this gives faster exhaust gasses making the turbo spin faster and easier, giving more boost and less lag, and hence more power.

my dad has a 2 litre saab turbo which has a similar sized exhaust which gives more power than the standard one

as i said turbos need slightly larger exhausts to allow the gasses to spin the turbo, the reason people say big exhausts reduce power is because of chavs in 1 litre novas with 3" exhausts and about 3bhp, if you have a proper engine you can put a proper exhaust on!

although this may seem like a bit of a "well thats fine if you have money to burn" but try different sized exhausts and see what works best for you.

n.b. nick, whats this NASP k-series you talk of? if you mean the k-series fitted to rover 214sei's i can confirm that a slightly larger exhaust does increase power!

n.b. nick, whats this NASP k-series you talk of? if you mean the k-series fitted to rover 214sei's i can confirm that a slightly larger exhaust does increase power!

it does increase power, but needs some back pressure to utilise it, I think he was just comparing the two