August 30, 200916 yr Hi all , I need to know what size engine pipes and up pipe people use when making EA82T headers . My rebuilt engine has ported heads NA MPFI cams (16-60 instead of std 14-56) and just over 8:1 CR . The inlet is Spider modded to use the original early (86) throttle body etc . We are considering using 1 3/4 inch 16 gauge stainless tube for the primary or engine pipes and possibly same or 1 7/8 for the up pipe section . Turbo flange will be T28 to suit a hybrid GT2854R I had made , by hybrid I mean the nicer GT28 NS111 76T turbine and the high temp material S15 0.64 AR turbine housing with the extra deflector vane cast into the back of it . Turbo started out as a GT2554R . The heads siamesed exhaust ports measure ~ 50mm which is probably too big tube size wise so needs to gradually reduce to maybe 1 3/4 or 1 7/8 inch (44 or 47.5mm) . As a rough rule of thumb I consider the wall thickness (x2) to be 1/8 " (3.2mm) so ID's would be ~ 1 5/8 and 1 3/4" (41 or 44m) . I think from memory the std Subaru header measured ~ 33mm round the bend on the far side and a fair bit larger at 41 odd mm at the turbo side . Also that crossover pipe round the front of the sump pan is double thickness with the inner ID being I think ~ 35mm or 1 3/8" . By the look of things it would be easier to have the collector down lower and just a single up pipe tube to the turbos mount flange . Just don't want to lose gas speed with over sized tubes . Thoughts ? Cheers A . Edited August 30, 200916 yr by discopotato03
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