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Went to look at the MS6 at lunch time again. This is to the people looking to get a aftermarket exhaust. Clearly the stock exhaust is more then adequate handle 300whp with stock 2.5 exhaust. I was surprised to see that this car lacks a mid resonator that the proteges have. The exhaust is nice and straight, only thing bottleneck I can see is the cat and precats which can be replaced with catless downpipe and a high flow cat. I dont have the article handy with me but there was a test done that 2.5inch piping is more then enough to put down 300hp to the wheels on turboed cars, anything bigger then that is just for show.
 

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Went to look at the MS6 at lunch time again. This is to the people looking to get a aftermarket exhaust. Clearly the stock exhaust is more then adequate handle 300whp with stock 2.5 exhaust. I was surprised to see that this car lacks a mid resonator that the proteges have. The exhaust is nice and straight, only thing bottleneck I can see is the cat and precats which can be replaced with catless downpipe and a high flow cat. I dont have the article handy with me but there was a test done that 2.5inch piping is more then enough to put down 300hp to the wheels on turboed cars, anything bigger then that is just for show.
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id like to see this article. having a larger diameter exhaust increases the volume in which the exhaust is released into.

in the formula PV=nRT, where P is pressure, V is volume, and we assume nRT is constant so the formula transforms into P=c/V. thus, the greater the volume, the lower the pressure.

now if we have a lower pressure on the backside of the turbine, we have a greater pressure change across the fins. so thus Bernoulli's law ( P + v^2 /2 ) entrance = ( P + v^2 /2 ) exit, where v=velocity. so if the pressure is greater at the entrance of the turbine, the velocity is lower, and the opposite is the case for the exit so the velocity is higher exiting the turbine.

thus, a 3" turboback will always, ALWAYS, outperform a 2.5".

just to add, the only way a 2.5" will outperform is if the flow in a 3" is turbulent. this can be caused by 90 degree bends or lousy welds.
 

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id like to see this article. having a larger diameter exhaust increases the volume in which the exhaust is released into.

in the formula PV=nRT, where P is pressure, V is volume, and we assume nRT is constant so the formula transforms into P=c/V. thus, the greater the volume, the lower the pressure.

now if we have a lower pressure on the backside of the turbine, we have a greater pressure change across the fins. so thus Bernoulli's law ( P + v^2 /2 ) entrance = ( P + v^2 /2 ) exit, where v=velocity. so if the pressure is greater at the entrance of the turbine, the velocity is lower, and the opposite is the case for the exit so the velocity is higher exiting the turbine.

thus, a 3" turboback will always, ALWAYS, outperform a 2.5".

just to add, the only way a 2.5" will outperform is if the flow in a 3" is turbulent. this can be caused by 90 degree bends or lousy welds.
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Exactly right...I'm looking to have changes to the exhaust system merely, however, on the basis of aesthetics as those shonky looking exhaust tips are just pathetic, particularly looking at the car directly from behind where one sees the end of the standard system, poking through...bloody awful! I'm off to Wallsend Mufflers to talk to Old Phil...this guy's a genius with exhausts and may come up witha solution, by the way he imports into OZ Magnaflow :yesnod: .
 

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id like to see this article. having a larger diameter exhaust increases the volume in which the exhaust is released into.

in the formula PV=nRT, where P is pressure, V is volume, and we assume nRT is constant so the formula transforms into P=c/V. thus, the greater the volume, the lower the pressure.

now if we have a lower pressure on the backside of the turbine, we have a greater pressure change across the fins. so thus Bernoulli's law ( P + v^2 /2 ) entrance = ( P + v^2 /2 ) exit, where v=velocity. so if the pressure is greater at the entrance of the turbine, the velocity is lower, and the opposite is the case for the exit so the velocity is higher exiting the turbine.

thus, a 3" turboback will always, ALWAYS, outperform a 2.5".

just to add, the only way a 2.5" will outperform is if the flow in a 3" is turbulent. this can be caused by 90 degree bends or lousy welds.
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ryceboy, you really got to lay off the engineering books... relax a bit man. You don't have to try to find an equation for every topic on the forum :) ... class is over!
 

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ryceboy, you really got to lay off the engineering books... relax a bit man. You don't have to try to find an equation for every topic on the forum :) ... class is over!
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heh. what can i say, i love physics.
 

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I just took a quick look under my car and it seems that after the y split the piping get smaller. looks like it could be 2 1/4 piping. dunno but can someonelse confirm this?
 

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what I'm saying is that 2.5 inch 300whp is more then enough effiency. there won't be any noticeable gain with a 3inch.
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now u see why i do my proofs elpepe? :D even tho it didnt really help here.
 

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what I'm saying is that 2.5 inch 300whp is more then enough effiency. there won't be any noticeable gain with a 3inch.
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On a NA car that is correct... but on a turbo car dead wrong....
 

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Wait until you see the dyno of CP-E's catback, I think you'll be VERY suprised what kind of gains their 3" piping made.
 

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I have always been curious about the efficiency of exhaust flow from the exhaust manifold or turbo, through the system.

Assume you have an aftermarket downpipe that is belled off the turbo and 3" down to a 3" cat, then mates to a 2.5" cat back...

is there that much velocity after the cat still where a full 3" catback would offer significantly more flow than a 2.5"?

I like OEM style exhausts because they are low profile....so my goal would be to keep the oem cat back w/ a downpipe and high flow cat and lose the perhaps "marginal" gains of going w/ a 3" catback.

:drive:
 

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I have always been curious about the efficiency of exhaust flow from the exhaust manifold or turbo, through the system.

Assume you have an aftermarket downpipe that is belled off the turbo and 3" down to a 3" cat, then mates to a 2.5" cat back...

is there that much velocity after the cat still where a full 3" catback would offer significantly more flow than a 2.5"?

I like OEM style exhausts because they are low profile....so my goal would be to keep the oem cat back w/ a downpipe and high flow cat and lose the perhaps "marginal" gains of going w/ a 3" catback.

:drive:
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the stock mufflers are sure to hurt it. the less back pressure in a turboback, the better.
 

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some DSM's run over 300whp with a 2.5" most use 3" then again some use 3.5 and even 4" systems... the only downfall to a 3" with stock turbo is boostcreep. I'm not schooled on the design of the MS6, but i know from experience that it does happen with DSM's even though we have a larger stock turbo...

IMO i'd go with a 3" and monitor it for boost creep...
 

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the stock mufflers are sure to hurt it. the less back pressure in a turboback, the better.
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Don't forget about weight savings also. Every aftermarket exhaust I have put on my cars has been significantly lighter than the stock system.
 

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some DSM's run over 300whp with a 2.5" most use 3" then again some use 3.5 and even 4" systems... the only downfall to a 3" with stock turbo is boostcreep. I'm not schooled on the design of the MS6, but i know from experience that it does happen with DSM's even though we have a larger stock turbo...

IMO i'd go with a 3" and monitor it for boost creep...
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i asked anthony at cp-e about it and he is aware of the possibility of boost creep. im assuming that the wastegate port is large enough to defeat boost creep considering that it completely dumps all boost during powerloss.
 

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i asked anthony at cp-e about it and he is aware of the possibility of boost creep. im assuming that the wastegate port is large enough to defeat boost creep considering that it completely dumps all boost during powerloss.
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Its been mentioned that during powerloss, the ecu will limit the throttle to 33% of WOT (thank you drive by wire). It might not be changing the behavior of the wastegate at all.
 

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i heard some pretty spectacular numbers are being produced by the 3" single exhaust by cp-e. they think the large gains might be from the CRAPPY stock exhaust. i, however, know its from pixie dust.
 

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Went to look at the MS6 at lunch time again. This is to the people looking to get a aftermarket exhaust. Clearly the stock exhaust is more then adequate handle 300whp with stock 2.5 exhaust. I was surprised to see that this car lacks a mid resonator that the proteges have. The exhaust is nice and straight, only thing bottleneck I can see is the cat and precats which can be replaced with catless downpipe and a high flow cat. I dont have the article handy with me but there was a test done that 2.5inch piping is more then enough to put down 300hp to the wheels on turboed cars, anything bigger then that is just for show.
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Lets clairfy some of this. First, the stock exhaust is not 2.5" it's 60mm which is between 2 1/4" and 2 3/8" OD. Second, where the exhaust splits in two, the piping is about 1.75" or 45mm. Third, the mufflers are an unknown quantity as to how poorly they flow. Fourth: A 1" pipe could probably support 300hp if you work the turbo hard enough. Just because you make a given amount of power, doesn't mean the exhaust supports it properly.
 

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If a Y pipe is used, it's not as effective as a single pipe, and the diameter NEEDS to be reduced - this far down the exhaust stream the exhaust is colder, and to keep the velocity up you need to make the pipe smaller. If you kept it the same size all the way, at the split you would have a big drop in velocity, and you'd have poor flow from the Y onwards.

Mazda does know a thing or two about cars. And I'd agree with 2.5" being sufficient, but most "tuners" like a 3" pipe - bigger is better right.
 
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