exhaust dummy..

[I Eat Catfish]

I just got a 06 F250 at the end of Feb. I just got a 58v FICM from Swamp's cause the original took a big fat dump on me! I'm planning on getting a Gryphon and want to know about exhaust opinions. I've heard some people say "straight 4" no cat, no muffler" and others say "that engine needs some backpressure or it will be a slug to drive." So what's the deal? I'm not looking for a wild, smoke pouring tune, just a little more "oomf" and some better mileage.

[907DAVE]

Do a turbo back and be done with it.

The whole back-pressure idea is a gasser thing and does not apply to our diesels. The turbo can generate all the back-pressure you want.

[I Eat Catfish]

cool. That will give me an excuse to get a straight pipe.

[KT Performance]

The straight pipe is also your cheapest option.

[Power Hungry]

Originally Posted by 907dave

Do a turbo back and be done with it.

The whole back-pressure idea is a gasser thing and does not apply to our diesels. The turbo can generate all the back-pressure you want.

I beg to differ just a bit. I've personally dynoed a truck with a 3.5" downpipe and a 4" downpipe and under load lost about 25-30 ft/lbs below 1750 RPM running the 4"... making no other changes. Of course, the 4" flowed better in upper RPM ranges and power was better there as well as having lower EGTs. So there is some truth to the backpressure stuff.

[907DAVE]

In school we were doing dyno runs trying different combos on our three fiftys, and yes we did pick up around 6-10 hp's in the lower RPM ranges with mufflers on. But from there on they were causing a very slight loss in power.

Bill do you think the 4'' was actually creating more backpressure in the low R's because of turbulence or expansion in the down pipe(not sure on the technical term), and the 3.5'' actually had a smoother flow?

[Power Hungry]

I couldn't really say. I'm not big on fluid dynamics but if I had to venture a guess, it is very possible that could have the case. I know gassers backpressure is needed to help improve low RPM performance and I imagine there's a similar effect in the way the exhaust is discharged into the downpipe.

[tuckman]

Bill,

Could you write a tune that keeps the turbo veins closed a bit longer to get that lost power back, for owners that have the straight pipe? Or is that something that is already done in tow tunes?

[NHRA6002]

I've got a Magnaflow 4" T/B with the muffler that came with it and no cat. Muffler keeps it from being anoying when idling and putting around town, but sounds killer when my foot is in it. The muffler that comes with it is straight through anyway so no real backpressure difference than straight pipe.imo