Am I running too big of an exhaust?
08-06-2008, 01:17 AM
#1
Am I running too big of an exhaust? Stock heads and bottom end but I have a Futral F13 230/232 on a 112 +2 cam, full intake (lid, bellows, TB, LS6, etc...) and a 100hp shot of nitrous.
It MIGHT get heads in the future (so please keep that in mind) but it definitely will stay stock displacement...
The exhaust is Mac Mid-Lengths (ported) with the crappy flanges cut off and replaced with V-Band clamps (so they are straight 3") into a dual 3" y-pipe (with high flow metal core cats) into a Flowmaster y-pipe then into a 4" Mufflex with Spintech muffler and dual 3"s out...
EXHAUST (pics are before the cats were on):
Is it too big for my car? Is it actually causing me to loose power? No dyno/track numbers yet, just wondering... Thanks!
It MIGHT get heads in the future (so please keep that in mind) but it definitely will stay stock displacement...
The exhaust is Mac Mid-Lengths (ported) with the crappy flanges cut off and replaced with V-Band clamps (so they are straight 3") into a dual 3" y-pipe (with high flow metal core cats) into a Flowmaster y-pipe then into a 4" Mufflex with Spintech muffler and dual 3"s out...
EXHAUST (pics are before the cats were on):
Is it too big for my car? Is it actually causing me to loose power? No dyno/track numbers yet, just wondering... Thanks!
08-06-2008, 09:05 AM
#6
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i dont understand how a 4 inch cat back would be too big. logic would tell you that your exhaust is only gonna flow as much as its most restrictive part. so if you had a 2 inch section of pipe followed by a 10 inch exhaust it would only flow as much as that 2 inch pipe could support. also how is his setup any different then someone with a cutout on the Y pipe? it would then be venting into the atmosphere with even less restriction then his 4 inch catback. i guess thats the old "you need some back pressure to make power" arguement huh.
08-06-2008, 09:19 AM
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Don't even worry about it, that's not too big. Spintech mufflers are known for flowing poorly so the extra size will help that cam breathe up top. I've got a 4" flowmaster merge followed by a 4" cutout then reduced back into a hooker catback. Its great, I love it. Loud or quiet comes at the flick of a switch.
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08-06-2008, 09:23 AM
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i dont understand how a 4 inch cat back would be too big. logic would tell you that your exhaust is only gonna flow as much as its most restrictive part. so if you had a 2 inch section of pipe followed by a 10 inch exhaust it would only flow as much as that 2 inch pipe could support. also how is his setup any different then someone with a cutout on the Y pipe? it would then be venting into the atmosphere with even less restriction then his 4 inch catback. i guess thats the old "you need some back pressure to make power" arguement huh.
Cross-sectional area of 4" pipe => = 12.46 inches squared
Cross-sectional area of 2X3" pipe => 14.13 inches squared
Its funny how people claim a 3" TD exhaust is the best flowing but a 4" y-pipe is too big. You can say what you want about scavenging effects, but I believe that the cross-sectional area of an exhaust system is the key factor.
Can somebody please shed some light on how backpressure creates TQ? And i don't mean some redneck BS about how there car feels torqier with a catback then open headers, but a real explination of the physics behind it.
08-06-2008, 09:34 AM
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i have heard the scavenging is more in the headers. hence the big changes in power going to a LT. something about the gases cooling further down the line and losing velocity. i dont remember exactly but it made sense at the time. once you get to at least a 3 inch diameter pipe with a bolt on/cam car...ORY, TD, cutout, or 4 inch catback i dont think makes any difference unless you are a dyno queen. most performance mufflers prolly can produce similar HP numbers and obviously there has to be a winner and loser. at a 3 or 4 inch level, i would choose my exhaust on the most important factor for you. i chose bullets bc of their size and the 100% straight through design.
08-06-2008, 09:51 AM
#10
wow, somebody actually knows what are they are talking about for once. I wouldn't spend any money modifying your exhaust. I have TD 3" over the axle. using the formular for area of a circle (pi*r^2), you get the following:
Cross-sectional area of 4" pipe => = 12.46 inches squared
Cross-sectional area of 2X3" pipe => 14.13 inches squared
Its funny how people claim a 3" TD exhaust is the best flowing but a 4" y-pipe is too big. You can say what you want about scavenging effects, but I believe that the cross-sectional area of an exhaust system is the key factor.
Can somebody please shed some light on how backpressure creates TQ? And i don't mean some redneck BS about how there car feels torqier with a catback then open headers, but a real explination of the physics behind it.
Cross-sectional area of 4" pipe => = 12.46 inches squared
Cross-sectional area of 2X3" pipe => 14.13 inches squared
Its funny how people claim a 3" TD exhaust is the best flowing but a 4" y-pipe is too big. You can say what you want about scavenging effects, but I believe that the cross-sectional area of an exhaust system is the key factor.
Can somebody please shed some light on how backpressure creates TQ? And i don't mean some redneck BS about how there car feels torqier with a catback then open headers, but a real explination of the physics behind it.
I was going to point out that the single 4" flows the same or less then a 2x3" setup. I'm glad you posted up the math behind it.
08-06-2008, 03:00 PM
#14
You'ld be more likely to hurt performance with too big a primary tube on your headers than a cat-back on the large side. You're fine. Even taking the cat-back off altogether, you might lose 3 ft-lbs and gain 9 rwhp
Last edited by Whistler; 08-06-2008 at 03:07 PM.
08-06-2008, 03:01 PM
#15
no man, your exhaust is fine, the only thing that might be hurting you powerwise is that spintech muffler
08-06-2008, 03:17 PM
#16
A buddy of mine has the same headers with SLP LM1 (flowmaster y) highflow cats and CME... For some weird reason it actually sounds throaty like a Mustang and reminded me of yours and Keith's setup.
I searched but couldn't find sound clips of either of your cars (you or Keith) to see if I was just making the memory all warm and fuzzier than it was
Also, if I did your setup I'd be using dual 3" all the way back and didn't know if that would change the sound too much as well... Basically I'm chasing the golden egg, the LS1 that sounds like a Mustang.
The Mufflex on this car just doesn't sound as killer as it did on the 94Z...
08-06-2008, 03:33 PM
#18
Heads probably won't happen for awhile, just dropped $2000 into the tranny.
So no sound clips of either of your cars?
08-06-2008, 03:49 PM
#20
You think MadKilla has a sound clip somewhere?