Exhaust back pressure

[04sd]

I've got a 4.0 in my Bronco II and I'm currently running the original 2.9 exhaust system minus the cat. The muffler is about 1/2 the length of the Explorer muffler. Do you think this is hurting performance and/or gas mileage?

 

[tigercat]

it all depends on the pipe diameter anything between 2.00"-3.00" is plenty

 

[Blacksheep Josh]

I think there's a Bronco subforum on here... might have more luck over there. If not, I'd say message 410Fortune, from what I know he's the BroncoII expert round these parts, lol

 

[Anime]

It's probably holding it back some, but even the factory exhaust for the 4.0 held it back.

If you're worried about it, adding a 2.25" exhaust with your choice of a performance muffler might be just the ticket.

 

[Masterd]

Yeah even the stock 4.0 system is probably holding it back a little.

I think it'd be safe to say the 2.9 system might be marginally more so.

 

[04sd]

I've got an almost new Explorer exhaust system, I'll have to measure the pipe size compared to the Bronco. I'd really like to keep it quiet so maybe I can fit the Explorer muffler, given I'm not running a cat it should still flow pretty good.

 

[Masterd]

The cat(s) are probably where the most restriction takes place, and I'm also sure that the factory pipe is crush bent as well, probably hurting flow there too.

 

[HahnsB2]

Other than the muffler the 2.9 exhaust is almost identical.

 

[Anime]

Stock pipe size is 2", but 2.25" makes a huge difference in terms of flow and exhaust gas velocity.

If you want quiet but better than using the stock muffler, you can go with a Dynomax Super Turbo. They have mufflers with a 20" long case, like the 17747, which is what comes on the cat-back systems for 91-92 Explorers. It's pretty quiet.