Is there a realistic BHP/Torque ceiling that these headers can achieve?

 

I guess it depends on what headers your talking about as there are many different types and design all with differing results

 

Ported OE headers from an 03 car.

 

Same car (03 WRX) with Harvey Smith ported and wrapped OEM headers. Currently at 290HP and having a TD05/06 20G Fitted which is good up to circa 400HP. Been advised that levels above 350HP wont be acheived unless i change them so i suggest thats probably around their peak or not too far off!

Be interesting to hear what other people have to say though!!

 

Ok thanks, look like ill need to change them then

 

Agree with KK.
Ported mine (Harvey does a far better job than me) @ 314bhp (Stock Sti V3) but made a one only run on an optimistic Well Lane RR of 407 bhp with Gruppe S unequal headers and a 20g/AndyF map.

I think most have found that the ported cast headers have a smaller 'bore' and give a nice low-down/midrange engine but fall off at the screaming top end.
i think Harvey can give you very good advice.
Search for him in Drivetrain.

Graham.

 

Thanks,

Im looking at using a GT30 based turbo so just need to make sure that the headers that i use or subsequently purchase will be up to the job...

Thanks

 

See also Andy Forrests articles in the past few issues of scooby mag where he tests the various types of headers which should give you some idea of what to expect.

 

MY00 ported headers and unopened 2.0 engine with 20G did 406 BHP on mine... with5ml/litre NF and lots of booooost

 

i am looking at offerings from GT spec and Borla, the headers need to be able to cope with 500. So i think even the best ported headers will have been long gone by that point!

 

Would tend to agree, but the Rigolis have done silly power on OEM headers.

 

Do the Rigoli have web site?
What boost did you get too John on the 20g?
Graham

 

think its www.rigoliracing.com or similar....


interesting though John...

 

28 PSI Graham.

 

It is a trade off between spool/drivability and more top end power.
Well designed tubular headers will produce more power higher up the rev range but 1 bar in 4th gear for instance may be 350 rpm further up the rev band. Now that may not sound like a lot but it could be the difference between needing a gear change and not.
I think it is down to what you personally are happy with and if you want minimal lag then ported O/E has to be the choice. For best rolling road figures above the mid to upper three hundreds then tubular would be my choice.
In the tests done by Andy for Scooby Mag, on a relatively small turbo, the best tubular headers were 5 bhp ahead of my comparative O/E ported but there was no lag as experienced with the tubular.

 

OK well in your opinion, what would be the best way to go on a closed deck 2.0, 7500rev limit and a GT30?

 

If you want to develop full power go for GT Spec tubular headers on the assumption you are aiming for 475-500 bhp. Spool will be 350 rpm or thereabouts, down on ported O/E but you have a good rev range with the 7.5k limit. BTW, even with tubular the car will probably be quicker changing well before the red line rather than holding it to 7.5k, particularly in the higher gears.