GPX exhaust on a GR?

[kevinod]

Hi guys,

I've been offered a used but in good nick cat back stainless steel exhaust. It's what I would be looking for if I did decide to go with an aftermarket exhaust, i.e. looks like stock, not loud. Only problem is, the bore is 67mm, i.e. GPX bore rather than GR bore.

Has anyone tried putting a GPX exhaust on a GR? I know there's the issue of matching up the holes at the cat, but I'm thinking it's going to have a negative effect on power ?

I've been doing searches on here and Ftooc, but haven't really found a definitive answer from someone who has tried it.

Kev.

[colm_mcm]

would have a beneficial effect. GX has same system as GPX as far as I know.

manifolds are same bore for GR and GPX, so you could fit a complete GPX system to a GR no bothers.

You'll need GPX downpipes and cat. I have both for sale.

[kevinod]

would have a beneficial effect. GX has same system as GPX as far as I know.

manifolds are same bore for GR and GPX, so you could fit a complete GPX system to a GR no bothers.

You'll need GPX downpipes and cat. I have both for sale.

I've got Mongoose downpipes, and asked about the fitment, and was told the exhaust would fit ok to the GR cat. I guess it's got elongated bolt holes like Mongoose catback must have?

[colm_mcm]

AFAIK, your mongoose downpipes are designed for a GR cat, which is smaller diameter than GPX. can't see how a GPX system would fit a GR cat

[kevinod]

Just came across what seems an excellent explanation of exhaust theory. At least it sounds good and scientic if nothing else!

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

[colm_mcm]

Just came across what seems an excellent explanation of exhaust theory.

I fell asleep halfway through. I reckon the the larger diameter exhaust system the GX has that the GR doesn't have accounts for some of the extra 10bhp that the GX has

[CJ]

I reckon the the larger diameter exhaust system the GX has that the GR doesn't have accounts for some of the extra 10bhp that the GX has

IIC, this is primarily due to a different ECU map and fueling characteristics. A bigger bore exhaust on the FTO doesn't offer much in the way of extra power and can often led to a drop in torque levels low down the range due to the reduction in back pressure.

CJ

[colm_mcm]

why did they change the GR exhaust on the facelift models then? We're not talking about running a sewage pipe from the manifolds, it's just a slightly larger diameter system. From what I read about the article, the author is referring to grossly mis-matched engines and exhausts when he criticises aftermarket systems.

[CJ]

why did they change the GR exhaust on the facelift models then?

Possibly to standardise exhaust systems between the V6 models or maybe with power hikes in mind. Either way, I doubt the increase in power from the exhuats change alone had any significant impact.

CJ