Back Box's

[DazzyA]

Is there any performance gain from them or is it just noise.

thanks.

[M5pilot]

No evidence of any performance gain over standard BMW (or equivalent).

The only exhaust I know that gives a gain is the one made by BTB - its a single pipe design and sounds well nice.

Alpina claim that their exhausts give gains but again no evidence of this so far.

[DazzyA]

Thank's for the reply sal, is all the power gained in the manifold then?

[maxfield]

Some in the centre section removing cat i think

[DazzyA]

I'm catless at the moment.

[M5pilot]

Only some manifolds are "proven" to give extra power. The Alpina one does as do the BTB ones.

I met a guy at Lakeside who had a dyno print of before and after Alpina manifold - 5 bhp.

The BTB(early one) - shown to give 8 bhp

The new BTB - 18bhp

[DazzyA]

Thank's for that, very handy to know. I wont be tempted to go for 2nd hand one's now.
cheers.

[Turbo-Brown]

Don't ignore the crossover chamber in the middle of the system, can make a fair difference to torque apparently!

[M5pilot]

Turbo Brown - this is exactly why the scorpion centre loses you torque.

Sebrings dont lose you anything from experience.

[oze30]

could you actually delete the centre box and make a crossover pipe instead?

[M5pilot]

You could do - it will be loud!