When Will A Quality 3" Exhaust Begin To Limit Power?

[private9]

Hi All,

Just wondering at what sort of rwkw figure does a good 3" exhaust become a limitation?

I'd like to stick to 3" for budget and ground clearance, but am just wondering where it will become a restriction?

Thanks,

Justin.

[senna_T]

beleive it or not, but the 3" exhaust is about the same as the standard system in the XR. The standard is Dual 2.25" and that equals 4.5" so do the math. 3.5" is the smallest anyone should go on these cars if they are looking for more than 280rwkw IMO

[private9]

well, you're right mate! I just did the maths and got the following results:

Surface area in square inches for each exhaust size:

Twin 2.25 = 10.5

Single 3" = 7.1

Single 3.5" = 15.7

Single 4" = 24.6

Aside from getting higher quality mufflers, why would anyone upgrade to a 3" considering that the pipework itself is less restrictive in standard form? Note, I am only talking about the pipework, not mufflers.

Thanks,

Justin.

[senna_T]

the pipe work is much of a muchness really, if it has press bends in it, then its crap, but if its mandrel bent then it is as free flowing as possible.

Good mufflers are essential - the standard mufflers actually reduce to around 1.75" inside, so they suck basically!

Welds are important, but they would have to be pretty sh*t to make a difference.

What power are you aiming for? That is the question you need to answer before you start modding

[private9]

Yep, naturally mandrel is the way to go!

Power goal isn't really known, I'd just like to go up in stages as I'm on a budget, and see what feels good!

[senna_T]

well, I would follow the standard system power limits, 280 would be the maximum efficient level, after that you are gonna need to upgrade

[private9]

No worries, thanks! The enquiry was actually for another car, which is why I was more interested in the power limits of a 3"

[senna_T]

if you can specify what engine/turbo combo it is, I can give you a bit more info, it is very dependant on the application.

[private9]

No worries and thanks for the advice so far!

It's an AU Falcon engine with a Snort stage 3 turbo kit on it. Currently running 210rwkw on 7psi and an overly rich tune. This is through a factory press bent exhaust, and as I want to do an exhaust next, I was just curious where a 3" will become a limitation.

[senna_T]

what turbo is it running?