exhaust loss on FI
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exhaust loss on FI Guys,
OK this has been edited, I am rephrasing my sentence.
I have two exhaust designs, how much MORE power will I have with the second design, over the third, of course ill have to find out myself, but any guesses?
scenario one. 2.5" turbo-downpipes, 3.5inch piping to tip with 3.5inch metal-core catalytic converters on each side, and one 3.5' / 9inch long bullet muffler.
Scenario two: 3" dumps right after the turbo downpipes.
My idea is to have BOTH the exhaust for quite normal driving, and dumps just after the turbo-downpipe and before the catalytic converter, to bypass both mufflers and cats for maximum power/sound and least backpressure possible.
Ideas?
Thanks.
OK this has been edited, I am rephrasing my sentence.
I have two exhaust designs, how much MORE power will I have with the second design, over the third, of course ill have to find out myself, but any guesses?
scenario one. 2.5" turbo-downpipes, 3.5inch piping to tip with 3.5inch metal-core catalytic converters on each side, and one 3.5' / 9inch long bullet muffler.
Scenario two: 3" dumps right after the turbo downpipes.
My idea is to have BOTH the exhaust for quite normal driving, and dumps just after the turbo-downpipe and before the catalytic converter, to bypass both mufflers and cats for maximum power/sound and least backpressure possible.
Ideas?
Thanks.
Last edited by ayousef; Nov 30, 2008 at 02:53 PM.
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http://www.quicktimeperformance.com/Controller/
Is this what ure lookin for dood (DMH/DHM sleeper cutout).
Is this what ure lookin for dood (DMH/DHM sleeper cutout).
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Bro, the stock exhaust is soo quite it gets on my nerves, I dont mind noise. My initial plan was to customize a weird exhaust and have vaccum valve dumps before the cat/mufflers, however im thinking its a tight fit on the corvette, and I am stilll looking for ideas to implement this.
In this case, above 3000rpms, the car WILL be loud whether i like it or not.
Thats when I thought of having a good flowing CUSTOM exhaust, I think since the turbo-downpipes are 2.5inches, having a 3.5inch metal core catalytic converter, 3.5inch resonator and 3.5inch bullet muffler would coz NO backpressure at all, of course I need the LEAST backpressure as possible after the turbos.
any other ideas?
In this case, above 3000rpms, the car WILL be loud whether i like it or not.
Thats when I thought of having a good flowing CUSTOM exhaust, I think since the turbo-downpipes are 2.5inches, having a 3.5inch metal core catalytic converter, 3.5inch resonator and 3.5inch bullet muffler would coz NO backpressure at all, of course I need the LEAST backpressure as possible after the turbos.
any other ideas?
ayousef,
a quiet exhaust will not lose as much power as most people would tend to think
on a huge cam car (C6Z, ported TFS's, LG Headers, 440 forged rotating assembly, somewhere between 17 and 24 horsepower was lost when going from Corsa Z06's to the stock C6 exhaust), and this was on an average of 3 dyno runs, lowest was 17hp loss, highest was 24 hp
i think you will lose less if a C6Z stock exhaust was used instead of a C6 stock exhaust
on another car, C6, built A4, forged 427, 8.5:1, TTiX twin turbo setup, ported LS7 heads, with B&B C6Z fusions, the car dynoed at ~850 rwhp or so with the B&B's, and then again a C6Z exhaust with the valves closed was dynoed: ~820 or so rwhp
the loss on a high boost FI car was somewhere around 30 rwhp for a C6Z exhaust with the valves closed, which would have also been restrictive but quiet
but would have had less of a loss with the valves open of course
i believe that the sacrifice of ~15-20hp NA and ~30hp high FI is worth the quietness that it gains
also, these figures represent the worst of each scenario
typical losses are less than 10rwhp for NA for going to a C6 exhaust and less than 20rwhp for FI going to a C6Z exhaust
most the the power loss people attribute are in the headers on NA cars
also, for comparison, there is another possibility, and thats to weld in a center muffler section similar to a bassani exhaust AND the rear section from a traditional/conventional rear muffler exhaust for a C6 vette
e.g.
then imagine if you had the center muffler AND a stock C6 2.5" exhaust, quieter than stock
_
a quiet exhaust will not lose as much power as most people would tend to think
on a huge cam car (C6Z, ported TFS's, LG Headers, 440 forged rotating assembly, somewhere between 17 and 24 horsepower was lost when going from Corsa Z06's to the stock C6 exhaust), and this was on an average of 3 dyno runs, lowest was 17hp loss, highest was 24 hp
i think you will lose less if a C6Z stock exhaust was used instead of a C6 stock exhaust
on another car, C6, built A4, forged 427, 8.5:1, TTiX twin turbo setup, ported LS7 heads, with B&B C6Z fusions, the car dynoed at ~850 rwhp or so with the B&B's, and then again a C6Z exhaust with the valves closed was dynoed: ~820 or so rwhp
the loss on a high boost FI car was somewhere around 30 rwhp for a C6Z exhaust with the valves closed, which would have also been restrictive but quiet
but would have had less of a loss with the valves open of course
i believe that the sacrifice of ~15-20hp NA and ~30hp high FI is worth the quietness that it gains
also, these figures represent the worst of each scenario
typical losses are less than 10rwhp for NA for going to a C6 exhaust and less than 20rwhp for FI going to a C6Z exhaust
most the the power loss people attribute are in the headers on NA cars
also, for comparison, there is another possibility, and thats to weld in a center muffler section similar to a bassani exhaust AND the rear section from a traditional/conventional rear muffler exhaust for a C6 vette
e.g.
then imagine if you had the center muffler AND a stock C6 2.5" exhaust, quieter than stock
_
well, lets start over then
to begin, with your TTiX kit, there is already less drone and the exhaust is already quieter than what you would otherwise have with headers on
adding headers on a C6/C6Z creates drone because of the total length of pipe on the vehicle is or so happens to be at the resonate frequency
which to eliminate completely, the total length of pipe has to change, adding resonators or bigger mufflers will not help nearly as much
when you add or reduce the total amount of length of pipe to the exhaust, you effectively move the resonate frequency up (reduce pipe length) or down (increase pipe length)
so for example, the reason that on the C5 it is so easy to create a really good sounding exhaust that naturally does not drone is because the length of pipe happens to be long enough so that the actual resonate frequency is actually low enough to not be heard, e.g. less than idle speed
but back to the original question:
you should specify if it is quiet you want or simply just no drone
depending on the combination, it is also possible to have LOUD but no drone at all and very quiet but huge drone, to the point where your entire frame is shaking and vibrating
turbos actually muffle some noise because it "chops up" the exhaust noise pattern
e.g. where as before lets say that the noise is -_-_-_-_-_-_-_-_-_-_-_-_ , now with a turbo on there it would actually become tiny pulses of air escaping between the fan gaps, e.g. -_ -_ -_ -_ -_ -_ -_ -_ -_
also, as sound waves hit the turbo "blades", the blades are always at an odd angle to the direction that the sound waves are traveling at and therefore again a slight reduction in sound pressure
that would be a very unscientific way of explaining the turbo "muffler effect" or why turbo cars sound slightly quieter and why the exhaust sound sounds more mixed up compared to NA cars
also, the cam choice in your car also has an effect with the sound
in general, the wilder the cam, the better the engine sounds and the louder it gets (again, an unscientific explanation)
so if you're really looking to use a mild or tiny cam, its going to be quieter anyways
to quantify the amount of noise difference
a wild cam can make corsa sports sound like corsa extremes on a LS3 OE cam
and turbos usually reduce the exhaust volume somewhere between 6-9 db depending on spool and turbo size
_
to begin, with your TTiX kit, there is already less drone and the exhaust is already quieter than what you would otherwise have with headers on
adding headers on a C6/C6Z creates drone because of the total length of pipe on the vehicle is or so happens to be at the resonate frequency
which to eliminate completely, the total length of pipe has to change, adding resonators or bigger mufflers will not help nearly as much
when you add or reduce the total amount of length of pipe to the exhaust, you effectively move the resonate frequency up (reduce pipe length) or down (increase pipe length)
so for example, the reason that on the C5 it is so easy to create a really good sounding exhaust that naturally does not drone is because the length of pipe happens to be long enough so that the actual resonate frequency is actually low enough to not be heard, e.g. less than idle speed
but back to the original question:
you should specify if it is quiet you want or simply just no drone
depending on the combination, it is also possible to have LOUD but no drone at all and very quiet but huge drone, to the point where your entire frame is shaking and vibrating
turbos actually muffle some noise because it "chops up" the exhaust noise pattern
e.g. where as before lets say that the noise is -_-_-_-_-_-_-_-_-_-_-_-_ , now with a turbo on there it would actually become tiny pulses of air escaping between the fan gaps, e.g. -_ -_ -_ -_ -_ -_ -_ -_ -_
also, as sound waves hit the turbo "blades", the blades are always at an odd angle to the direction that the sound waves are traveling at and therefore again a slight reduction in sound pressure
that would be a very unscientific way of explaining the turbo "muffler effect" or why turbo cars sound slightly quieter and why the exhaust sound sounds more mixed up compared to NA cars
also, the cam choice in your car also has an effect with the sound
in general, the wilder the cam, the better the engine sounds and the louder it gets (again, an unscientific explanation)
so if you're really looking to use a mild or tiny cam, its going to be quieter anyways
to quantify the amount of noise difference
a wild cam can make corsa sports sound like corsa extremes on a LS3 OE cam
and turbos usually reduce the exhaust volume somewhere between 6-9 db depending on spool and turbo size
_
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Well, the idea was to have cats and bullet mufflers on the quite (drivable side), and dumps just before them, lets say the best of both worlds 
but I still didnt make up my mind, well see what I come up with in the next few days, anyways Ill get the car out of the shop minus the axle-back exhaust, and ill be driving it like tht for a few days, ill see how loud/tolerable it is.
Any more input?
but I still didnt make up my mind, well see what I come up with in the next few days, anyways Ill get the car out of the shop minus the axle-back exhaust, and ill be driving it like tht for a few days, ill see how loud/tolerable it is.
Any more input?
