Has anyone got dyno proof of the gains going to a full 3" exhaust?
06-11-2005, 11:53 PM
#31
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Andrew,
Didn't they do dyno runs with that 944 turbo project car in (?) European Car Magazine. ...or whatever it's called. If I remeber, they changed the exhaust all the way back from the headers. I may not be remembering it exactly, but I recall substantial gains. I have too think that there is a direct correlation with better spool up. Though I have a 2.5 downpipe, I am running 3" , with no cat (btw...almost anyone will delete it for you guys. Not a big conspiracy in any state. It's illegal for you to drive it, not for them to remove it.) and my car has a very noticeable increase in power.
I would think that you're right about the issue being only one of back preasure. Then again, if your turbo is creating enough preasure you should lose power with a bigger down pipe, right?
The question is where does your car fit within that spectrum? You make a lot of power, with lots of mods, so (obviously) my dyno dynamics would be SOOO different then yours, or yours to anyone elses.
on another note, that shouldn't ever even have too be addressed, Rolex, your bs is wearing thin around here. If you have a prob with Andrew, take it to pm. I've noticed you "chasing" him all over the board. Cut it out. (Cripes! I never thought it possible that someone could make Andrew look like the good guy!) Chill out already.
Didn't they do dyno runs with that 944 turbo project car in (?) European Car Magazine. ...or whatever it's called. If I remeber, they changed the exhaust all the way back from the headers. I may not be remembering it exactly, but I recall substantial gains. I have too think that there is a direct correlation with better spool up. Though I have a 2.5 downpipe, I am running 3" , with no cat (btw...almost anyone will delete it for you guys. Not a big conspiracy in any state. It's illegal for you to drive it, not for them to remove it.) and my car has a very noticeable increase in power.
I would think that you're right about the issue being only one of back preasure. Then again, if your turbo is creating enough preasure you should lose power with a bigger down pipe, right?
The question is where does your car fit within that spectrum? You make a lot of power, with lots of mods, so (obviously) my dyno dynamics would be SOOO different then yours, or yours to anyone elses.
on another note, that shouldn't ever even have too be addressed, Rolex, your bs is wearing thin around here. If you have a prob with Andrew, take it to pm. I've noticed you "chasing" him all over the board. Cut it out. (Cripes! I never thought it possible that someone could make Andrew look like the good guy!) Chill out already.
06-11-2005, 11:57 PM
#32
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Ehall,
I thought that changed the headers at the same time... or didnt include the SFR downpipe till later. I will go check it out again, I forgot about that article. I will start with the back pressure I think and then go from there. I would love a 3" exhuast to get me closer to 400WHP! Its "free" power really.
I thought that changed the headers at the same time... or didnt include the SFR downpipe till later. I will go check it out again, I forgot about that article. I will start with the back pressure I think and then go from there. I would love a 3" exhuast to get me closer to 400WHP! Its "free" power really.
06-12-2005, 12:01 AM
#33
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That may be the case. I would think that you could still extrapolate a bit of real info from the different results. Then again, everytime you think you have it all nailed down with this process, something jumps up and surprises you.
06-12-2005, 12:04 AM
#34
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Yeah exactly, John's comment about finding a loss in power is a good example of a jump out and surprise! Getting the back pressure should give me a clue to make an assessment based on data though, rather than a "it should work" basis.
06-12-2005, 12:06 AM
#35
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I think a better solution would be going to 2 3/4 inch
for the test pipe & 3 inch from cat back.
BTW, has anyone ever thought about converting the
axial flow of the exhaust to linear flow by using stator
blades ?
for the test pipe & 3 inch from cat back.
BTW, has anyone ever thought about converting the
axial flow of the exhaust to linear flow by using stator
blades ?
06-12-2005, 12:23 AM
#37
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Rolex, you dont need to post that you sent someone a PM, it adds nothing to the thread. I am not attacking you in particular, just keep it in mind, the person will know you sent them a PM when they get it...! cheers.
06-12-2005, 12:32 AM
#38
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Originally Posted by J Chen
I think a better solution would be going to 2 3/4 inch
for the test pipe & 3 inch from cat back.
BTW, has anyone ever thought about converting the
axial flow of the exhaust to linear flow by using stator
blades ?
for the test pipe & 3 inch from cat back.
BTW, has anyone ever thought about converting the
axial flow of the exhaust to linear flow by using stator
blades ?
Interesting idea, I am not sure that it would easily be tested though as the design would be key which means mapping velocity vectors... not an easy task!
06-12-2005, 02:58 AM
#39
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Originally Posted by NZ951
Rolex, you dont need to post that you sent someone a PM, it adds nothing to the thread. I am not attacking you in particular, just keep it in mind, the person will know you sent them a PM when they get it...! cheers.
06-12-2005, 04:22 AM
#41
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Hi NZ,
The point of it all is that every one including the press
seems to think that the bigger the exhaust the better.
Yes they right in a certain way but nobody has ever
examine the true cause of back pressure. Is it just
the volume of exhaust gas against pipe volume ?
My bet is that it's two folds.
1. Axial - It creates lots of turbulance down the line
& as distance, temperature drop & pipe
diameter increases, it gets worse.
2. Pipe Diameter : Going too big immediately just after the
down pipe will actually slow down the
exhaust velocity as well as creating unwanted
turbulance.
Ofcourse this is in theory. Without proper testing, we'll never know.
As to 4 inch exhaust, take note that in race cars, the engines almost
never stays below 3500 rpm.
The point of it all is that every one including the press
seems to think that the bigger the exhaust the better.
Yes they right in a certain way but nobody has ever
examine the true cause of back pressure. Is it just
the volume of exhaust gas against pipe volume ?
My bet is that it's two folds.
1. Axial - It creates lots of turbulance down the line
& as distance, temperature drop & pipe
diameter increases, it gets worse.
2. Pipe Diameter : Going too big immediately just after the
down pipe will actually slow down the
exhaust velocity as well as creating unwanted
turbulance.
Ofcourse this is in theory. Without proper testing, we'll never know.
As to 4 inch exhaust, take note that in race cars, the engines almost
never stays below 3500 rpm.
06-12-2005, 04:33 AM
#44
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you know, I forgot to consider the high rpm issue. That makes a lot of sense. Even "off" throttle, you're on throttle, as opposed to a street car. Damn I hate math!
06-12-2005, 04:40 AM
#45
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Upto my 8th year at Univrsity and avoided math (calc) the whole way! Stats nailed me a few times though.
J, are you going to do before and after pressure or HP / Torque testing?
J, are you going to do before and after pressure or HP / Torque testing?