Which downpipe should I buy??
18 January 2003, 11:27 PM
#5
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Have you tried Midland Impreza. They do a Polished Stainless twin dump cat bypass. Looks well smart with as far as down pipes go!! Give them a call, the lads there are great.
www.midland-imreza.co.uk
[Edited by Weenie - 1/18/2003 11:41:55 PM]
www.midland-imreza.co.uk
[Edited by Weenie - 1/18/2003 11:41:55 PM]
19 January 2003, 12:12 AM
#6
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Twin dump no good for mapping for sustained high boost pressures so if you are going that route get a scoobysport or similar.
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20 January 2003, 10:57 AM
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Open neck downpipes give more accurate wastegate control, period. I'm not saying you CAN'T map twin dumps, just that its less consistent and reliable, and that any good mapper would likely factor in a percentage safaty margin losing you valuable peak figures.
22 January 2003, 05:33 PM
#19
just got back from a quik test of the after burner(scoobysport ver1)decat d/p after fitting.it provides much better pick up,turbo whistle and loadsa pops and bangs
just what i was after
just what i was after
22 January 2003, 09:26 PM
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IMHO, there isn't going to be a huge difference in power between most of them. As a rule of thumb, bellmouth (open neck) tend to give slightly better low speed spool, twin dump slightly better at high revs. Closed neck (standard fit, HKS, Power Engineerings "budget" option - T65) are generally less powerful as the wastegate flow is impeded, so avoid them IMHO, but that's about it. You can get "composite" downpipes with a splitter in the bellmouth - eg APS, MRT which claim to offer the best of bellmouth and twin dump; low down and high up power.
Other factors? Some have sports cats, which allow emmissions compliance, at the loss of probably only 1-2bhp for "moderate" cars (say <350bhp). For big power cars, you'll want one that can go to a 3" system, rather than the standard 2.5", but that will generally be noisier. Many will fit to a standard centre section, some are part of a custom exhaust (3" systems will fit in this catgory). One or two have apparently had fitting troubles (e.g. early Magnex, IIRC), though not normally a problem.
Some pipes are noisier than others, which is a noticeable difference. Sports cats tend to be quieter, the BPM twin dump is also apparently very quiet, the HKS is apparenly very loud. Most are 304 stainless steel, although you can get other materials - e.g. cast ones will tend to be slightly quieter, better thermally (i.e. release less underbonnet heat), and could have more accurate shapes.
FWIW, I have an APS. It is a composite (splittered bellmouth), cast, with sports cat and 3" output, so only mates with the APS centre section. Not the cheapest, but the full APS system is emmissions compliant, 3" most of the way back, not too loud and decent power, which suited me. However, nearly everyone is happy with their own downpipe, so you're unlikely to go wrong with most big name ones.
Other factors? Some have sports cats, which allow emmissions compliance, at the loss of probably only 1-2bhp for "moderate" cars (say <350bhp). For big power cars, you'll want one that can go to a 3" system, rather than the standard 2.5", but that will generally be noisier. Many will fit to a standard centre section, some are part of a custom exhaust (3" systems will fit in this catgory). One or two have apparently had fitting troubles (e.g. early Magnex, IIRC), though not normally a problem.
Some pipes are noisier than others, which is a noticeable difference. Sports cats tend to be quieter, the BPM twin dump is also apparently very quiet, the HKS is apparenly very loud. Most are 304 stainless steel, although you can get other materials - e.g. cast ones will tend to be slightly quieter, better thermally (i.e. release less underbonnet heat), and could have more accurate shapes.
FWIW, I have an APS. It is a composite (splittered bellmouth), cast, with sports cat and 3" output, so only mates with the APS centre section. Not the cheapest, but the full APS system is emmissions compliant, 3" most of the way back, not too loud and decent power, which suited me. However, nearly everyone is happy with their own downpipe, so you're unlikely to go wrong with most big name ones.
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