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3" Exhaust

2641 Views 13 Replies 6 Participants Last post by  [email protected]
Would anyone be interested in a custom made 3" exhaust with your option of straight pipes from header back, to only muffler / resonator , or both? Thinking I might be able to easily make kits for 600 - 700 bucks for the full system. Just wondering how many may be interested. I'm going to make a straight pipe one for my car wed to see how it sounds and acts and will be posting a video.
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if you have no muff / res you have no business charging 600-700 bux sorry man.. not to mention 2.75 is the absolute largest I would go on a stock turbo vt and even that would be pushing it.. an exhaust that had a 3" dp.. then dropped to 2.75 then tapered down to 2.25-2.5 would probably be best. but since no one would actually make that.. 2.5 is good enough
Why does everyone think that 3" exhaust for our cars are too big? Only problem with the exhaust being too big is sound issues (loudness).
because even in a turbo car.. where you want " no backpressure" you need to keep up proper exhaust velocity and there is a very fine line between proper velocity and not. if you don't have the correct velocity your will lose out on low end torq, the reason people normally go with big exhausts or cutouts is because the loss of torque is offset by better top end flow.. but being that the car doesn't even have a 2.5" ID pipe to begin with (hell it's like 2.3 or something like that) raising the exhaust diameter is huge.. put it this way... the turbo cobalt comes stock with 260 crank hp... the amount of HP that is gained from putting a 3" exhaust on those cars is like 5-10 whp, a 2.5-2.75" exhaust is good till 300-320 whp on most cars without seriously hindering anything.. Hell I know a guy that pushes 340-360 whp on a supercharged ion that still only runs a 2.5" catback and he's found that you're only gettins miniscule gains which in his opinion don't offset the difference in sound.

for a car that prides itself on low end torque.. because of the tune this car doesn't have low end torque.. why would you want to pull it out more...

this feels like this is another case of "i want it just because it's what other people with other cars talk about syndrome" I see a trend arks catback is going to be 2.75.. and thats the largest one that is giong to be out.. every other one is 2.5... now if you want when i drop my car off for R&D I can see if they can do a 3" version and dyno the difference between the 2.5 and 3" but thats all up to who I'm dropping my car off and if they want to waste material

I think the better question isnt why people think it isn't good.. it's why do people think it's necessary?
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Also we're talking about turbocharged cars, not supercharged cars...supercharged/na cars both benefit from scavenging.

3″ Exhaust Too Big for your Turbo Mini? » PERRIN Performance Official Blog

your right we both are talking about turbo cars.. I merely brought up a sc car because of the fact it ran a much smaller exhaust with more power which people would assume would create more back pressure

and no i'm not talking about the scavenging effect which as you said is determined by the collector / runner design of the manifold I'm talking about exhaust velocity (however scavenging can ALSO be slightly effected by exhaust design)

not to mention.. holy cow I cant take that article seriously when "Because turbo cars have lower compression, the sooner you get it making boost the sooner you have torque, the more torque at a given RPM means more HP" is in there.. boost is a measure of restriction....... and keeping slightly more pressure in the exhaust keeps higher cylinder pressures which can help spool the turbo faster thus giving more low end torque.. which is what I was saying.. the the advantage of what I was saying about the stepped exhaust is it keeps a similar dynamic pressure due to the fact the exhaust cools and gets more dense as it travels on the length of the exhaust so it allows to you keep high flow as well as low torque

it's simply due to the length of the pipe.. say if you were runnging a fender exit exhaust a larger exhaust wouldn't be as much of an issue because the gasses are imediately exiting the system.. where as if you're running to the back of the car.. too large of an exhaust pipe can create reversion.. you want as close to 0 back pressure as possible.. more on the POSITIVE side if possible ( things always flow from high pressure to low pressure).. pulling negative backpressure is problem and a side effect of a much too large exhaust
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I for one think the price suggested for $600-$700 is money wasted if its all pipes, perhaps if the valuation were more in the $200-$300 then there would be greater likelihood that a few might try the 3" route, but for $600-$700, may as well go for the Magnaflow GB posted in anther forum for under $600 shipped
this was originally what I was saying 600-700 bux for a no name straight pipe is way too expensive
well good to know what people think. Like i said still haven't priced it all out with mandrel bends and weld time involved. But, depending what you do, mufflers and res, a 3" would be fine bc those will add a little back pressure. or at least a 3 down to 2.5 near the back. dealt with this stuff a lot and will just have to dyno it to see what will work the best. All i know is im not spending 1200 on an exhaust that only gets 10 hp gain. If its possible to get 10hp gain for 400 and that is a viable option i will make the kits. But, not going to sell kits if there is no money to be made. I dont mind making 20 bucks a kit for my time but still. Plus, if i do this right there will be more then 3 options for an exhaust and this will be the least expensive.
holy crap someone knows!!!!!!!!!!!
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