Hi,

I'm wondering if anyone knows if a decatted 2.5 inch system will support 430bhp as I've bought a TD05H-GXT-R blouch turbo and wondering what supporting mods are essential. I've heard conflicting reports about exhaust diameter.

Cheers,

Chris.

 

Nah, I'd go for a 3" over 400hp

I take it your turbo housing is the 8cm version to why you quote 430?
Basically a sc42 turbo but the 42 comes with a 7cm housing and is sold as a 420 turbo

 

I was at over 400+ bhp with a 2.5 decatted exhaust,but as Busta said 3" inch is the way to go really for better flowing exhaust and turbo spool up.SJ.

 

Just going off the blouch website says it's rated at 430? I thought sc42 was a 20G with a 7cm housing?

 

Bugger, thought I'd get away with a 2.5. Oh well on the look out for a decent 3inch turbo back system then.

Cheers for the info guys.

 

Sc42 is the same turbo, ive got the box with same model number on, but think scoobyclinic have them made with the 7cm housing instead

 

My Bug went to 425bhp on an H & S 2.5" system, and there are others out there that have achieved 500+ on similar systems. In fact if you go to 3" too soon you can lose spool and even power, so don't be too ready to knock 2.5 exhausts.

 

There is no spool to be compromised by the exiting gas, its pre turbo where you will gain spool.
The exiting gas will determine the end power in terms of exiting flow.

 

How can you lose spool rate by increasing the ability to flow gas through the turbine?

 

If that holds true then why not go to 3" when the engine is otherwise completely standard?

 

so would a 3" system be ideal for a 2.5 forged engine?
I know this question has been asked loads of times but who makes a quality system ?

 

Paben is correct, the exhaust gas has more velocity in smaller diameter pipe with a dedicated diameter for a certain flow rate.
As the gas leaves the turbine housing into an exhaust that is too big, it gains pressure and loses velocity.
Whether 2.5 inch pipework is the optimal diameter I don't know but the smaller diameter you can get away with the better as far as spool and response are concerned.

 

In my experience a 2.5 system spools better than a 3" on a smaller turbo.
I gained more power going 3" but also got more lag.
I have a full 3" h&s, sounds bloody lovely but my plans have changed now and I'm only going to 360-370 Bhp with something like a sc36 and a sports Catted 2.5" system.
I really need it to be quieter too with all the early starts I do.
Just to add the finish and build quality on my Hayward and Scott is brilliant.

Siv

 

Thought SC38 was td05 based, and journal bearing

Was sure that SC42 & SC46 used GT30 based ball bearing cores,

Sc turbos not just the Blouch with a 7cm exhaust ?

 

That's more to do with the benefit of exhaust scavenging being acheived with higher gas speeds in a smaller pipe csa than spooling.