Backpressure on exhaust

[94f350]

I was thinking about straight piping my truck but I don't want to make it any slower than it already is. Does anyone know if an idi needs exhaust backpressure or is that more of a gasser thing?

 

[Rdnck84_03]

I was thinking about straight piping my truck but I don't want to make it any slower than it already is. Does anyone know if an idi needs exhaust backpressure or is that more of a gasser thing?

In all honesty it's more of an urban myth even with a gasser. There may be some efi systems that need some backpressure to keep the computer happy.

All of my diesels are straight piped. And in reality my gassers are as close to straight piped as you can get with mufflers. I run 12" glass packs on them with true duals.

James

 

[u2slow]

The IDI with straight pipe is quite raspy in my experience. A turbo knocks it down a bit.

I would probably do a 3-4" single with one of those hi flow see-thru style mufflers.

 

[Jesus Freak]

If your truck is NA, straight pipe is LOUD!!! Some type of simple muffler will shut it up a bit. If you're turboed then no muffler is alright.

 

[chillman88]

I have a glass pack on mine and it's not terrible but it's still pretty loud. It gets old on the highway for long trips.

The common myth about back pressure comes from the fact that a properly sized exhaust will have a scavenging effect which will actually assist with pulling the exhaust gases along where an oversized exhaust will flow less efficiently than a properly sized exhaust.

Neither of which has any back pressure....

 

[Nero]

Having very light exhaust restriction helps with variable turbo setups, otherwise straight pipe it up.

 

[FrozenMerc]

Since our beloved IDI's have zero overlap between the intake and exhaust valves, reducing back pressure just frees up horsepower that would otherwise be used to pump the exhaust gases out. No engine "needs" backpressure (with the exception of 2 strokes, but that is another conversation entirely). However, on engines that have overlap in the valve timing, scavenging caused by the momentum of the exhaust gases as they leave the cylinder can help to draw in the intake charge, increasing overall volumetric efficiency.

 

[IDIBRONCO]

(with the exception of 2 strokes, but that is another conversation entirely).

I thought about this yesterday, but also decided that it didn't have a place in this discussion.