Engine/Transmission (1994 - 1998) Does a 4" exhaust do any good?

[MKline]

If the exhaust manifold outlet is only so big, Why does a 4" exhaust system differ from a 3" exhaust system? It seems to me that the real restriction is with our manifolds. Just looking for imput since I've been contemplating new exhaust.

 

[Gary - K7GLD]

If the exhaust manifold outlet is only so big, Why does a 4" exhaust system differ from a 3" exhaust system? It seems to me that the real restriction is with our manifolds. Just looking for imput since I've been contemplating new exhaust.

The spent hot exhaust gasses from our engines powers the turbo, and requires sufficient space past the turbo for rapid expansion and escape from the engine and maximum overall efficiency. Best efficiency depends upon the basic engine configuration and various mods added - typically, the more mods, the more air passes thru the engine and turbo and out the exhaust system - and also the more need for that flow to happen with the least practical resistance to flow.



Some guys get carried away - and exhaust system size CAN get beyond the point of need or efficiency - but that's sort of a personal thing and judgement call...

 

[Forrest Nearing]

what he said... twice!

 

[Vaughn MacKenzie]

It's not unusual to lose a little low-end spoolup and in-town fuel economy going to a 4", but when loaded or working a truck that has the power turned up the 4" is worth the upgrade.

 

[pwerwagn]

Im still running a 3", and dont mind it. Im not running the cat or muffler, though.

I have a 4" for it, just awaiting time to get it on. Ive been running the 3" with the walker now for 3 years though, and dont mind it at all. lowered EGT's somewhat, sounds a little better, and has absolutley no drone.



If you dont have a lot done to it, and money is tight just stick with the 3" and straight pipe it. If you want the sound and the looks, with better flow, go ahead and spring for the 4".

At lower power levels (<350hp), it really comes down to a matter of preference more than necessity.



--Jeff

 

[Matthug]

4'' sounds way better than 3'' IMO... . less backpressure means lower EGT's (to a point). There's no point in a 5'' exhaust until you atleast have 400 RWHP.

There's 4'' straight pipe systems on ebay 24/7 for $275 shipped to your door, if you can't afford that you probably don't own a CTD.

 

[MKline]

Nobody said I can't afford new exhaust. I was just asking about the restriction of the manifold outlet verses Keeping 3" exhaust.

 

[Matthug]

There has to be a restriction in the manifold/turbo or else the turbo wouldn't spool up... . but anything after the turbo the less backpressure the better.

 

[MKline]

Thanks for the info guys.