When do you need 5" exhaust??

[Smokin Joes 2500]

I was readin another thread where a guy wants 5" duals on his truck. That seems totally overkill to me? Ive (looking at sigs) seen some pretty peppy trucks on here with 4" exhaust! My 05' had 5" on it and it, at low rpm's, sounded like there was a bunch of turbulence in the exhaust. Ive heard people say, that turbulence causes back pressure. Is this true? When do you NEED to step up to 5"?

 

[nickleinonen]

at about 500 or so. . standard rule of thumb my teachers at college went by was about 1"/100hp. . i like the deeper sound of a 5" over a 4", but performance wise gains are nil until you have a 5" turbine outlet [twins]

 

[Smokin Joes 2500]

at about 500 or so. . standard rule of thumb my teachers at college went by was about 1"/100hp. . i like the deeper sound of a 5" over a 4", but performance wise gains are nil until you have a 5" turbine outlet [twins]

Well lets be a-orderin them twins:-laf

 

[johncameron]

When do you NEED to step up to 5"?

I'd say more like 700-800HP



JC

 

[Mobius1]

Actually thinking about it Smokin Joes, I may not totally need a 5 inch turbo back. Maybe just 5 inch from turbo's to my mbrp muffler. It then outs to 2 (four) inch outlets. That may be plenty right there. So what I really need is a 5 inch cat delete pipe able to mate to the mbrp

 

[Smokin Joes 2500]

at about 500 or so. . standard rule of thumb my teachers at college went by was about 1"/100hp. . i like the deeper sound of a 5" over a 4", but performance wise gains are nil until you have a 5" turbine outlet [twins]

So 1000 horse power trucks need 10" pipes:-laf

 

[ToddK]

Save your money! I had a cat back dual system on my '06. EGT's seemed very high, so I was told that I needed to get a turbo back 5" and remove cat. So I did. Not a darn difference!(well one, sounds cool)

 

[Highfinance97]

When do you NEED to step up to 5"?

when you want to tick off your neighbers



Michael

 

[betterthanstock]

standard rule of thumb my teachers at college went by was about 1"/100hp. .

That is so wrong...



So a 4 HP lawnmower needs a 0. 040" diameter hole? Good luck pulling the rope on that one! Or a 50 hp with a half inch diameter exhaust pipe. That's barely good enough for a 2 hp chainsaw.



It goes by the area, not the diameter. You want a certain area, depending on CFM, EGT, and speed of sound.

 

[Highfinance97]

Kind of like 10 lbs. of boost per 100 HP:-laf





Michael

 

[nickleinonen]

So 1000 horse power trucks need 10" pipes:-laf

could be... depends on what your application is and how you want to control turbine outlet tempratures



below stack size is about 8"x24" or so. . turbo for 4000hp.

-



dual 5" manifolds feed the turbo

-

Kind of like 10 lbs. of boost per 100 HP

the above charger when in good shape and the engine is tuned, will put out about 38psi making the 4000hp. . [the one with the glowing exhaust has a similar turbo for 4500hp, makes 42psi at 4500hp but that pic it was making 26psi @ 4300hp]

So a 4 HP lawnmower needs a 0. 040" diameter hole? Good luck pulling the rope on that one! Or a 50 hp with a half inch diameter exhaust pipe. That's barely good enough for a 2 hp chainsaw.

and... ?



on a turbo diesel engines in the 250-550 hp range [factory output], that 1"-100hp is pretty close [±1/2"]

 

[OT-OF-HERE!!]

5" exh,.. when do you need it

I'll probably spell this wrong,. . but probably 2 years ago Jannety Racing (an east coast performance shop) did a comprehensive test,. . all on the dyno and you don't get any increase until you're over 500hp and then it's modest until you really get the power up into the 700+hp on #2. It's obviously different with NOS as I believe if you ck it out that the Banks truck (World Land Speed Record Holder) is running 4".



In my personal compulsive changing out of my exhaust like underwear, then I do think I have now achieved lower egts by a 100 or so by going to a full 5" system except for my dual tailpipes which are 4",. . but 4X2 is still 8" total for the tailpipes so I can't think that I have any problem exiting the 5" from the turbo to the tail pipes. My $. 02.

 

[TAbbott]

Dual 4's have essentially the same flow characteristics as a single 5".

 

[lcaad1249]

Dual 4's flow more than the single 5. Is has to deal with the area, not the diameter. The single 5 has 20 in^2 where the dual 4's have 24 in ^2