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.

 

[parkergn]

What would you’ll recommend for a proper sized exhaust system for a 6.9 non-turbo.

3”?

 

[Nero]

What would you’ll recommend for a proper sized exhaust system for a 6.9 non-turbo.

3”?

Stock size. Only need to go bigger if you're moving more air volume. Non turbo doesnt move that much.

 

[parkergn]

Stock size. Only need to go bigger if you're moving more air volume. Non turbo doesnt move that much.

What about the “restrictive y-pipe” some have claimed should be replaced / improved. Mines shoot and considering upgrading my full exhaust. Custom SS and call it done for 10+ years.

Maybe I’ll start a new thread in 6.9

 

[franklin2]

You can talk and dream about all types of exhaust, stainless, etc. But where are you going to get this done? It's not cheap. I do my own exhaust work, so I use the stock stuff you get from Walker muffler. Stock exhaust with a glasspack is not too loud. Someone had split the exhaust on my truck when I first bought it, with two glasspacks on it and it was very loud when it was pulling.

If you find links on aftermarket pipes that fit our trucks, and are not "out of stock" post them up.

 

[Jesus Freak]

You can talk and dream about all types of exhaust, stainless, etc. But where are you going to get this done? It's not cheap. I do my own exhaust work, so I use the stock stuff you get from Walker muffler. Stock exhaust with a glasspack is not too loud. Someone had split the exhaust on my truck when I first bought it, with two glasspacks on it and it was very loud when it was pulling.

If you find links on aftermarket pipes that fit our trucks, and are not "out of stock" post them up.

It's the K.I.S.S.E.D. method....
Keep it simple stock exhaust duhhhhhhh.

 

[parkergn]

You can talk and dream about all types of exhaust, stainless, etc. But where are you going to get this done? It's not cheap. I do my own exhaust work, so I use the stock stuff you get from Walker muffler. Stock exhaust with a glasspack is not too loud. Someone had split the exhaust on my truck when I first bought it, with two glasspacks on it and it was very loud when it was pulling.

If you find links on aftermarket pipes that fit our trucks, and are not "out of stock" post them up.

Got a shop here in Toronto that can do the whole truck custom from the manifold to tailpiece. Quoted SS, magnaflow, all mandrel starting 3” of y. $1150 USD all in cash.

Just really questioning how it’ll help the engine. Because I’ll never do it again.

 

[Nero]

I ran 100% stock exhaust on my truck with a wastegated 093 kit and it did just fine. I only went to a larger exhaust when I blocked off the wastegate, did head studs and a larger pump because I needed more flow.

I still say you'd be fine with stock exhaust if you never plan to do any power mods. But it is your money.