4" Exhaust ?


New member
I have a friend that just bought a new Dodge Ram Truck with a Cummins Diesel motor. It's a 4x4 and I was under it looking around at all the new shiny stuff when I noticed the huge exhaust pipe :shocked: . He said it was 4" pipe. So, my question is - is the pipe dia. large because it's a diesel? What would this type of exhaust do on a gas motor?


New member
With the size of the diesel and the compresion ratio it requires that size of exhaust.. On a gas engine i.e. 4.0 it would make it sound like crap and it will have no backpressure and in turn burn your engine up.. 2nd of all you would waste time and money putting it on i.e. an XJ because as soon as you go offroad it would be crushed or ripped off...


New member
Even a 2.5 inch pipe is a tight fit in certain areas on the XJ - there's no way a 4" pipe would fit. Aside from that, exhaust flow (and power) would suck because you wouldn't maintain any gas velocity or heat. If you were turning 9000 rpms, then it MIGHT be applicable (but even then it might be too large...). And XTrmXJ was correct in stating that the exhaust would be torn off at the first rock or stump you went over. Don't forget - you'd need a muffler that can handle a 4 inch pipe as well, and that means BIG size....

The diesel uses this large pipe because it's 5.9 liters, plus being turbocharged, they are going for minimal backpressure after the turbo for best efficiency.