4 inch exhaust big enough?

T

Todd W

Comp Diesel Sponsor
I am pulling out my gt4208 as the atmosphere charger on my street truck and am replacing it with a gt4718. I currently have a 4 inch system and am wondering if it will flow enough for the new turbo.

I have read that a 4 inch is good to 1000 hp in the gasser world, don't know if its the same on diesel. also the turbine exducer is approximately 3.3 inches.

I am planning on running a 5 inch down pipe and reducing to my 4 inch system. Will this system be a restriction or will i notice no difference, other than noise, between a 4 inch and 5 inch?
 
Personally I think 5" is quieter. as far as power I don't think 4" is much of a restriction at all. My system is 90% 4" and I feel like its adequate. Now when you get into the big 15 liter engines that our primary turbos come off of, yeah 4" is a restriction.

Stepping up eh?? that truck is a rocket already!
 
YOUNG GUNS15 said:
Personally I think 5" is quieter. as far as power I don't think 4" is much of a restriction at all. My system is 90% 4" and I feel like its adequate. Now when you get into the big 15 liter engines that our primary turbos come off of, yeah 4" is a restriction.

Stepping up eh?? that truck is a rocket already!
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Yeah it ran great, it was very fun and met all my goals. The problem is that the stupid frozen boost cooler sent crap through my second stage compressor and chunked it up, Primary is fine. So I decided to go ahead and step up to a bell interstage cooler, and rather than rebuild the stock turbo I thought I might upgrade. So if I am doing all that already, seems like a good time to step up on the big guy.

Also I think you are the only person I have ever heard say that a 5" is quieter than a 4".

What are you smoking tonight?
 
Man I don't know all my class 8 stuff has 5" at 600hp as stock issue, so we double the mass flow and stick it down 4"....I suppose if it floats your boat. No data myself either way, but considering compounds, compound back pressure as well free flow takes new meaning.
 
I still run the factory 3.5" with muffler on my CR. love it. But 4" is good enough for most applications.
 
JasonCzerak said:
Two turbos is way too quite for me! Tho I'm happy the drone is gone.

5" turbo back with out a retarded chrome tip looks better and sounds better then 4" imho.
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With 4" pipe I can still hear myself making motor sounds as I go through the gears. Just like i used to do in my pedal car.
 
Im not smoking anything! There are two identical 12 valves in my home town and one belonged to a good friend of mine and we installed your run of the mill 5" system with a muffler. The other one belonged to a close neighbor and he installed a 4" system with a muffler, the 5" was the quieter system inside the cab by quite a bit. Both were extended cab long bed trucks with manual transmissions.
 
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