exhaust system

[ridinak]

i have a 94.5 7.3 and i have recently got a edge evalution programer and have been lookin at exhaust systems and have found some with a 3in down pipe and 4in straight pipe out the back and have also found a system with a 4in down pipe and 4in straight pipe out to the back i kinda want to go with the one with the 4in down pipe would i have any kind of trouble with that system due to lack of back pressure or exhaust temps from the pipe bein to big for good air flow????

[SINSTER96]

not sure if u can get a 4" down pipe on a OBS, its pretty tight already. If ya can it would be better in everyway in my opinon. Dont worry about back pressure , yer still running an exhaust system anyways

[97powersmoker]

you would need to modify the firewall to fit 4" dp

[tgroy]

Originally Posted by 97powersmoker

you would need to modify the firewall to fit 4" dp

yup on hat I have a 1994 f350 and just put on a mbrp tb exhaust and we had to do some adjustments to the firewall to get the 3 inch downpipe, you would have to modify the firewall to get on a 4 inch but the 4 inch would be better. I have the edge evolution tuner with the exhaust and 410 gears and she hauls real nice!

[lil o rinny]

Has anybody tried doing a body lift, then a 4 in down pipe. Dont know if it would make it any easier, but it seems like it would give you more room.

[Tony V]

3inch is all you'd need. The body lift may help, but you'd have to lift it probably at least 4 inches to even make it different. I think.

[MichaelP]

Is it a true 4" downpipe? Because our stock turbo outlet is just 3" anyway. Mine is an expanding 3" to 3.5" to 4" downpipe. It took a little extra clearancing at the pinch weld (but even a 3" needs some clearancing), and it works great. Mine opens up into a sewer-pipe 5" exhaust right at the end of the downpipe, so I have as little post-turbo backpressure as you're going to find.

Regards,
Michael Pliska

[ridinak]

i dont know if its a true 4in down pipe all the information i could find on it said 4in down pipe how much work and what do you have to do to the firewall to get it to clear?

[ianjadkins]

Don't bother. You would have to cut the shape out of the firewall and weld in new metal. Just use a 3" dp. Turbo outlet is 3" anyways.

[DDD 96'250]

I had to customize my firewall a bit jus to fit a 3in dp... 4in deffinatly not gonna fit...