4" vs 5" exhaust system which one ????

[HeberRam]

Does anyone have any infomation regarding the difference of using a 4" or 5" exhaust system on a heavy modified diesel? What are the pros and cons? Does the fact of reduced back pressure using the 5" reduce spool up? Does it help top end? Anyone have dyno results comparing the two? Trying to decide to leave things alone or go to 5"???



Thanks,

 

[Joseph Donnelly]

I found that with the engine over about 570 hp with a 12 valve, 5” exhaust helped over 4” by maybe 10 hp.

 

[HeberRam]

Sickly???

Joe are talking about "sickly" ??? Anything would help that truck. :-laf :-laf



Just kidding, What about 3rd gen? Help or hurt, forget about HP increase.

 

[Joseph Donnelly]

On a third gen it can be tough getting rid of the drone, and the rpm range of droning tends to be 500 rpm vs. 200 rpm where it is bad on a 12 valve.