lead_foot

iTrader: (1)

I can't see there being many (if any) preforamce gains over a relatively straight 4-2-1. Can any one else enlighten me why they have designed it this way other than to look different?

Mike Rainbird

iTrader: (3)

Scavenge effect of engine pulses to help pull spent gases out of engine.

lead_foot

iTrader: (1)

So one and four connected together, and two and three connected together, all being equal length is the idea. So as the exhaust gases are already flowing down say the exhaust runner from number one, the exhaust gases are just exiting the exhaust valve and entering runner from number four and the flow from one will help the gases from four flow? and vice versa?

Mike Rainbird

iTrader: (3)

God this is a mega complicated subject . Basically you get two different designs - 4-1 and 4-2-1. 4-1 is usually for out-right power at the expense of mid-range. 4-2-1 is usually for mid range power / drive-ability at the expense of top end power. However, to achieve a good compromise for a high revving road car, they tune the lengths of the 4-2-1 systems to help negate the down-sides of this set up. Basically you can tune the exhausts to produce the kind of power band you want to achieve, but without variable valve technology (in the exhaust), it will be just a "best" compromise to suit the power delivery of the engine.

There's so much more than I can explain in one paragraph, as there are entire books on this subject .

lead_foot

iTrader: (1)

Cheers Mike.

dave cos4x4

iTrader: (5)

no big explanation then Mike like Stu does.