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race exhaust

 
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Steve D



Joined: 09 Aug 2004
Posts: 102
Location: San Diego

PostPosted: Fri Feb 18, 2005 4:09 pm    Post subject: race exhaust Reply with quote

OK. OK. I know the exhaust subject has been beaten to death over on the E30 general forum, with many claiming that free'er flowing exhausts may provide some hp gains at high rpm only at the expense of low end torque. But for those of us who's E30's spend 90% of their time > 5k rpm at WOT, are there actual gains possible on the exhaust side of the equation? Anyone have any dyno data on this?

Also, what sort of mufflers (if any) are most racers using? I've heard mentions of Flowmaster, but which flowmaster (40 series, 50 series...) I haven't heard? Third, any thoughts on removing cats? I've got my spec E30 car nearly done & am in need of more projects!
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dale



Joined: 22 Aug 1999
Posts: 3085
Location: Seattle, WA USA

PostPosted: Sat Feb 19, 2005 8:49 am    Post subject: race exhaust Reply with quote

No articles with dyno time that I know of, but I'll be playing with this in the spring.
My gut feeling based on seeing lots of dynos of different race cars in different configurations, is removing the cat, opens it up a little, for racing use only, headers help a little, big free flow exhaust helps a little.
Let's say each one helps 1hp,
$300-$1200 for headers, plus installation
$100 bypass the car, racing only
$500 for custom exhaust, or bolt on aftermarket
Looks like you can easily spend $2k on just the exhaust system, for cool sound, and maybe maybe as much as 5hp.

I'm going with a new $300 shorty header as my old Stahl $700 header is all beat up as my car is so low.

Anyone in Seattle area want to buy a used Stahl header for M20 325i, lots of flat tubes on the bottom, but not that much affect on HP. $150

Hooking a custom exhaust up to that, which I can get a deal on, maybe, for around $400ish.
But a factory exhaust isn't really an option for me as it wouldn't survive the beating I put my exhaust through.

Dale
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