Manifold Replacement

[scott.a]

My S1 has according to Craig at CMC got the standard OEM manifold. Receipts i have show its been fitted with a Janspeed exhaust at some point from the cat back. Think it also may have the standard cat.

It has the PTP 140 kit fitted including the 52mm throttle body and a pipercross induction kit.

What power benefit (If any) do you guys think id get if i changed the manifold and cat for something a bit better?

[tut]

At the 140hp point Scott changing manifolds, CATS, etc are a very poor return in value for money terms for the small hp return you may get. The standard CAT is heavy and a little restrictive and I used to use a straight through pipe, but that was with 180hp and is a pain for MOT's. A sport CAT would give a slight improvement but at too much expense.

Likewise you only need a freerer breathing larger diameter manifold when you start modifying the head and fitting T/B's and an Emerald ECU. Rule of thumb is that you need a 15 to 20hp increase between upgrades to notice an appreciable difference.

tut

[Shug]

Peak, probably not a lot without remapping, but you'd likely gain some midrange torque that'll make it feel faster than a few BHP at the top end would anyway.

[scott.a]

So probably without other upgrades not worth it.

I would like to go K20 at some point but the costs of building rather than selling and buying a pre-converted car seem to be a bit of a false economy.

[mwmackenzie]

If you're going for a 4-2-1 manifold you need the small diameter piper one, the lager diameter one is said to rob torque if under 160bhp I believe, I could be wrong but that definitely rings a bell!

[Scuffers]

If you're going for a 4-2-1 manifold you need the small diameter piper one, the lager diameter one is said to rod torque if under 160bhp I believe, I could be wrong but that definitely rings a bell!

effectively, you are correct (based on what's currently for sale out there).

sub ~190Hp, the smaller bore 4-2-1's are better suited (and by smaller I'm talking 5/8" primaries over 3/4", both are significantly larger than the OEM item)

[Ferg]

My understanding is that the S2 K series manifold and down pipe provide a small but notable breathing improvement over the S1. Nice and cheap upgrade and they come up second hand quite regularly. There was one on SELOC last week. :thumbs up