Over the last few days i have been wondering if the header that i have will be suitable for my twin scroll GT40R setup. Each of the below headers are equal length headers which the merged joins of the runners will be separated into a true twin scroll header..

Im running an x-force equal length header to which ill be making a modified twin scroll upipe to suit and. However im unsure whether the diameter of the pipes may be a restriction to flow...

Ive been looking at the perrin equal length headers as there is some data suggesting that they flow very well but i think they are the same diameter as the x-force headers.

The full race equal length headers would be optimal as they are of much greater diameter it appears from the pictures.

What are ur opinions on diamter of the runner pipes for the headers, in terms of flow and outright power??

will the larger diamter pipes be less responsive??

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I'm a jockey kunts...

larger headers will be less responsive due to slower gas velocity till you come on boost then will flow more....

By twin scroll do you mean split pulse???

Is the turbo a garret gt 40r??? would think that would be pretty laggy on a wrx???

Is it the 88mm wheel or the 94????

cause I have a gt 4202 for the rx3 and it's pretty bloody big.... has 102 comp wheel in it..

yeh split pulses and a true twin scroll GT4088R 1.06 A/R... so full boost should come on around 5000rpm 30psi...

but im running a 2.5ltr with rpm limit to 8500.. so i dont think itll be too laggy coupled with a 6-speed box...

but im wondering if flow would be restrictive at these levels and thus require larger diameter piping or that the diameter dosent come into play and the smaller diameter piping would be better suited...

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I'm a jockey kunts...

You gunna run 30psi, jeez, ha ha.... still a pretty big turbo, will be pushing a fair volume of air into the engine.. I don't know to much about boxer engine's as mostly dealt with rotor's, which can turn some pretty big turbo's.. would think you'd keep the runners same size as the ports, as only two cyliders will be going into each pulse of the snail. wrx headers are pretty long, would think the exhaust gases would be to slow and lose alot of there heat by the time they got to the the exhaust housing... I'd stay with smaller headers with such a large frame turbo, that's just my opinion, may not be anywhere near the mark...