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

[Kimberley Scott]

The three inch will be a retriction from the wastegate back.

scotty

[senna_T]

kimbo, you're a sh*tstirrer if ever I've seen one!

[private9]

  Kimberley Scott said:

The three inch will be a retriction from the wastegate back.

scotty

Good call mate!

Senna, it's running a T04E, unsure of the exact specs though. I know that it should be ok for at least 300rwkw.

Edited 22/03/08 01:12 PM by private9

[senna_T]

hmmm, T04E is a decent turbo for the 4.0L, still decently responsive, and a 3" wil be ok, but if you follow the path of 3.5" with a 5" bodied cat - over 300 is achievable with the right intake - either way it will be a bloody quick street car!

[Red t ute]

I made 348RWKW in my ute with a 3 ince X force.

I had orded a 3.5 ince got ripped off a the shop did't find out till the cat converter failed 1year later.

[RAP1D]

  private9 said:

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.

Just go for a 3inch system to keep costs down and it will mate up to the Snort kits dump pipe and external gate.

Have you built the motor or is it a stocker?

Basically your turbo system is alot better flowing and larger than the standard xr6t set up so your gains from just fitting a 3inch exhaust will be better.

I built an ED turbo awile back, it made just over 300 on 14psi, with a similar set up to Snorts kit, and through a 3inch custom dump/external wgate and 2.5inch redback cat back.

You'll be fine with the 3inch, go for it

[private9]

!

  senna_T said:

hmmm, T04E is a decent turbo for the 4.0L, still decently responsive, and a 3" wil be ok, but if you follow the path of 3.5" with a 5" bodied cat - over 300 is achievable with the right intake - either way it will be a bloody quick street car!

Thanks mate, that's the plan! I've already got a decent cat for it (pretty sure it's a 5" body) waiting in the shed, so I've just got to pull my finger out and get the exhaust done!

  RAP1D said:

Just go for a 3inch system to keep costs down and it will mate up to the Snort kits dump pipe and external gate.

Have you built the motor or is it a stocker?

Basically your turbo system is alot better flowing and larger than the standard xr6t set up so your gains from just fitting a 3inch exhaust will be better.

I built an ED turbo awile back, it made just over 300 on 14psi, with a similar set up to Snorts kit, and through a 3inch custom dump/external wgate and 2.5inch redback cat back.

You'll be fine with the 3inch, go for it

Thanks mate - I think a 3" should be fine then. It's a standard low km AU2 bottom end in an EB. They're are a few people getting about with 300+ on standard AU bottom ends without trouble.

I'd like to see close to this, and I'm pretty sure the combo is more than up to it. I won't push for more though until I sort out a gearbox!

[Dyno Junkie]

  private9 said:

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.

Correction on the above calculated square inches. Note no reference is made for wall thickness of the tubing which does put a twin 2 1/4" closer in overall size/flow to a single 3'

Twin 2 1/4" 7.95

Twin 2 1/2" 9.81

Single 3" 7.06

Single 3 1/2" 9.62

Single 4" 12.56

[private9]

Good point, but what did you allow for wall thickness?

[Dyno Junkie]

This depends on the supplier of tubing, can be as small as 1.2mm up to 2.0mm.

It's been a few years since I was in the exhaust industry, but I think 1.6mm was a fairly standard size for 2-2 1/2" tubing.