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I had a conversation with Harvey about this a few years back and he sent over some blurb about it.
Might be of interest to you...
"I am well known for ported headers and the perfection of the porting on these has been honed over many years and over the last 12 years on Subarus in particular. I also sell tubular headers, the same ones as Lateral and many others but these are imported to the UK by Roger Clark Motorsport and distributed by various supply houses. When 2 bolt header sets were the norm I was involved with Matt Clark in attempting to resolve distored flanges and blown gasket issues with 2 bolt GT Spec header sets. Matt’s solution was a 3 bolt flange and he did not go for my slip jointed suggestion so we went our separate ways but are still the best of friends obviously. These header sets (3 bolt) are as good as you can get but the supplied uppipe is a big let down and slugs spool which is why I then designed the “Trick” 3 bolt which I now sell direct to enthusiasts and also RCMS, Lateral and others.
Do not confuse the purpose designed, performance matched, 2 bolt upppipe with the Trick uppipes. They are completely different items.
The original “trick” uppipe, christened by Olly Clark of RCMS has a three bolt flange for use with the GT2 Spec Type tubular headers as imported by RCMS and sold by myself, Scooby Clinic, API and numerous others. My uppipe is redesigned to incorporate a slip joint to reduce the possibility of headers cracking and it is designed to incorporate a gentle swage, located and calculated to increase gas velocity and hence quicker spool and greater torque right across the rev range. Results are staggering and a remap is required because you need to fuel much earlier in the map where spool occurs. The “trick” uppipe took 12 months of work from inception to final design. Sometimes what we thought would work did not translate into real gains and indeed we found some losses where we expected gains. There were several expensive flow bench testing sessions to perfect the design along with on car testing.
Because of the great success of the 3 bolt trick uppipe I have also designed and manufactured a similar item but in 2 bolt flange for use with tubular headers with 100mm flange hole centres and 60mm header flow outlet. This is specifically for 2 bolt 100mm flange centre tubular header sets. 60mm exit from headers to uppipe, like the original GT Spec type headers, Gruppe S and their copies. Again performance gains are startling and because of the design and slip joint, providing the flange is flat in the first place, blown gaskets are a thing of the past. Again, a remap is necessary. The design was perfected with flow bench testing.
The “Performance matched 2 bolt” was originally designed after I started porting headers and uppipes but I realised from testing that even with porting the original Subaru uppipe was inefficient. This uppipe is for use on ported Subaru headers sets, standard header sets or tubular header sets where the exit diameter from the uppie is much smaller. In the order of 40mm. These are excellent decat uppipes. Again these were subject to extensive flow bench testing to perfect the design.
There are actually six uppipes in this range and the correct uppipe is chosen for the turbo, displacement and spec in use.
Generally ported headers are a good option to 380-400 bhp at which point the benefits from GT tubular with “trick” uppipe become apparent. Ported headers generally give better spool but become restrictive beyond a certain point as the engine power is increased. That said we have several ported header sets with performance matched uppipe in the 430-450 bhp bracket.
Harvey specced my engine for me, Darren at DLM, and Harvey, built it.
I wanted something that would give an easy 400/400 with early spool and driveability round town.
Harvey told me that at that level, it was a toss-up between ported and tubular headers. I eventually bought some tubular ones off one of his cars, and am very pleased with the way the car performs.
Bob Rawle was also pleasantly surprised when he mapped it.
hmmm, interesting reading but the harvey stuff is obviously harder to get hold of now and i'm not sure what the price would be. Will have to look into it as I plan to venture past 400
hmmm, interesting reading but the harvey stuff is obviously harder to get hold of now and i'm not sure what the price would be. Will have to look into it as I plan to venture past 400
Alyn at AS Performance supplies everything Harvey used to
I think I looked on their site before and couldnt see anything
Alyn is old school, give him a ring he does not list much on his site. As a bonus he gives great advice about modding and wont ever sell you anything you dont need
Well I guess that would depend on what engine your running 2.0 / 2.5
But given what you can achieve from a stock base remap , it isn't going to be much more than that . It's pointless putting the feed in - if you can't push them out .
Thanks to everyone for the advice so far, unfortunately I'm not financially in a position to be able to afford £400+ on a set of the harvey headers so is there a more wallet friendly option?
My aim is to go ver 400bhp at some point in the next 6 months so i'm just in the process of putting the ingredients together.
I've seen various other brands and prices but would like peoples real world experiences as headers are 1 thing i've never needed to buy or look into.
I was told stick with stock mildly ported factory headers and a quality up-pipe for up to around max 380-390bhp on a 2.5L, up-pipe Perrin or Harvey Trick Pipe are an excellent complement but you need to make sure you add suitable heat protection especially to the up-pipe.
I've run this set up on a 2.5 STI with good results and was using the Perrin Small Bore up-pipe on a billet Perrin Small Bore Up-pipe wrapped in ceramic wool and Nimbus Heat Shield Stock ported header wrapped in ceramic wool and Nimbus Heat Shield Stock ported header wrapped in ceramic wool and Nimbus Heat Shield
TD05-18G
Last edited by STI450; 28 December 2020 at 05:43 PM.
Reason: Original Reply on wrong post
30 April 2015, 11:57 AM
Max power on standard headers
