Exhaust manifolds

[R1 Indy]

Im getting a full custom build exhaust system build for my 7 in a few weeks, but I need to decide between a 4-2-1 or a 4–1 manifold.

Now I know nothing about exhausts or the difference between them.

The engine is a 2008 Yamaha R1 if that makes any difference.

So can anyone advice me on the difference, or which I would be best going for?

Cheers

[Krikkit]

Has the map been adjusted since you fitted the engine? What's it set up with at the moment?

[300bhp/ton]

R1 Indy said:

Im getting a full custom build exhaust system build for my 7 in a few weeks, but I need to decide between a 4-2-1 or a 4–1 manifold.

Now I know nothing about exhausts or the difference between them.

The engine is a 2008 Yamaha R1 if that makes any difference.

So can anyone advice me on the difference, or which I would be best going for?

Cheers

I don't know specifics for these engines, or the manifold options. But on a n/a motor you want a manifold to promote scavenging. As a rule longer primaries work better at lower rpms, although in the case of a motor like this they certainly like revs.

I can't see how a 4 into 1 would offer any scavenging benefits. But the 4-2-1 would only be worth it if designed well. Flow rate is a consideration, but 2nd to scavenging on n/a motors.

If you are going to run forced induction then you'll want the best flowing manifold regardless.

Edited by 300bhp/ton on Tuesday 26th June 09:47

[busta]

I think the general rule is 4-2-1 gives improvements over most of the rev range and 4-1 is tuned for better top end, but I may be wrong!

Given your application, I'd say 4-2-1 is the better suited.

[R1 Indy]

As for map, its got a power commander fitted, but its not set up properly yet.

I would prefer the power more over the rev range, rather than just the top, so does that mean the 4-2-1 would suit best?

Oh and the person who is building it certainly sounds like he knows what he is doing (tube engineering), and have heard good things about the level of work they do.

he mentioned something about equal length, i take it this is quite important?