4inch Exhaust
exhaust doesnt really "support" hp. it all depends what kind of setup you have. while it may be beneficial to one, it might to do no good on another setup.
for FI....4" is usually what the guys use in the 1000hp range. NA.... i think thats the biggest youll ever need
for FI....4" is usually what the guys use in the 1000hp range. NA.... i think thats the biggest youll ever need
4" pipe will suport 656hp with zero loss. 115cfm per square inch cross sectional area, 2.2hp per CFM.
I have a 4" I pipe with a cutout, then a 3" reducer. Pics/writeup of it in the sig link.
I have a 4" I pipe with a cutout, then a 3" reducer. Pics/writeup of it in the sig link.
Thread Starter
Teching In
Joined: Dec 2006
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Thanks for the input. I was hoping someone would know some formulas to figure that out. TheBlurLS1 if your bored how about 5"? I think 656 will be over what I will be making but, I didn't think the Flowmaster 3" kit I have would do it, I was thinking Flowmaster said either 350 or 450 HP. I am hoping to be in the 500-550 HP range. Thanks again, Mike
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Originally Posted by TheBlurLS1
I have a 4" I pipe with a cutout, then a 3" reducer. Pics/writeup of it in the sig link.
Originally Posted by TheBlurLS1
4" pipe will suport 656hp with zero loss. 115cfm per square inch cross sectional area, 2.2hp per CFM.
Area = 3.14 x r x r
= 3.14 x 1.25 x 1.25
= 4.9 x 2 (dual pipes)
= 9.8125 sq in
From your formula above:
CFM = 115 cfm per sq in
= 115 x 9.8 (from the above area)
= 1127 cfm
hp = 2.2 hp per cfm
= 2.2 x 1127 (from the above cfm)
= 2479.4 hp
Which is obviously wrong...am I messing up my math?
woops nevermind I realize you have to divide by 2.2 in the final step...it's 2.2 cfm per hp not 2.2 hp per cfm...so here are the hp support numbers I get:
Is this fwhp or rwhp?
Code:
single 3" = 369 hp single 4" = 656 hp dual 2.5" = 512 hp dual 3" = 738 hp
Is this fwhp or rwhp?
Originally Posted by Turbo LS1 SS
so my 3" is only good for 369hp? the dyno must have been wrong when it says 900hp... :gotme:
o i know its a HUUGE restiction....im actually in the process of making an exhaust. for power ill use the cutout. havent decided whether to use 3.5 or 4". im stepping it off the 3" from the downpipe after about 2'. then ill prolly step it back down to my magnaflow for easy driving. i made teh 750rwhp with the 3" cutout open. i was exagerating a little bit. with it closed, i can feel the backpressure like u wouldnt believe
oh ok, im not saying that you cant make that kind of power through a 3" but it just wouldnt be smart
As far as your exhaust i would do a 4" i pipe with a 4" cut out and then step it down to a 3 inch and go though your Magnaflow... You should check out TheBlurrLS1's exhaust to give you some ideas.... How big is your down pipe?
As far as your exhaust i would do a 4" i pipe with a 4" cut out and then step it down to a 3 inch and go though your Magnaflow... You should check out TheBlurrLS1's exhaust to give you some ideas.... How big is your down pipe?
You can make 10000hp through a 2" pipe, but you could be making more with larger.
If you're pipe isn't rated for zero loss at whatever you're making, don't sweat it, you're probably not loosing much. Flow rate is determined by cross sectional area and differential pressure. Final pressure is always 14.7, because your exhaust pipe is opening into atmosphere.
To move the exhaust gas out at a certain rate, through a given area, you need a certain pressure differential. If you make more power, you'll have to increase that pressure differential in order to move the same amount of exhaust per the same amount of pipe. Increasing that pressure differential costs you horsepower, but not very much in most cases.
If you're pipe isn't rated for zero loss at whatever you're making, don't sweat it, you're probably not loosing much. Flow rate is determined by cross sectional area and differential pressure. Final pressure is always 14.7, because your exhaust pipe is opening into atmosphere.
To move the exhaust gas out at a certain rate, through a given area, you need a certain pressure differential. If you make more power, you'll have to increase that pressure differential in order to move the same amount of exhaust per the same amount of pipe. Increasing that pressure differential costs you horsepower, but not very much in most cases.