Thread: Straight pipe on DE?

i ran 2.5 in straight pipe. dont do it if you plan on driving in a city, near any cops, near people, and not on a track. it is not worth it.

so it's better to use 2.5 straight with diagonal exit for freeflow muff.. just to give extra breath for the headers. also gain some small hp

Back flow/pressure, you can believe in it or not. Quite a few people don't believe in it. Hence the short fender exits, exhaust cut outs and such.

Personally I believe in it and think some is needed. why do you think collectors on the headers are the way they are; they don't just put as big as a collector as possible.

One last question. Just to clear it up (mostly to myself) do you mean a straight pipe, like trucks do, with out a single bend in it?

Just wanted to chime in, that back pressure is an issue on carbeurator engines, but fuel injection usually can adjust for any changes in airflow. Not really a 'belief' but a technical fact.

Collectors are mostly designed for efficiency and noise comfort, so there's a balance. In general, a bad collector design creates pressure, a good design releases pressure or draws negative pressure across the pipes.

Huh... Learn something new everyday.

My HS automotive teacher never explained it like that. Just sorta said some was needed no matter what, showed a few mixed(carb & efi) examples and moved on.lol

Well thank you for clearing that up

I think he mean running without a cat...

I tried the "no cat straight pipe" thing once.It was the quickest way I could find to subtract the most torque. The car couldn't get out of it's own way.Went to a high flow cat with much,much better results.On the dyno,the no cat setup lost about 10 lb ft of torque and gained 0 hp.With the high flow,2 lb ft of torque was gained,along with 4 hp.Just my experience,yours may vary.

4-1 headers straight 2 1/2 pipe with 18" resonator.. then 2.5" / 3" inlet freeflow? would it better ?

Depends what you're doing it to, what your build is, and what the car is for. Exhaust isn't a starting point for upgrades, it's usually the result of other things. Like, this motor + this upgrade = this exhaust. I've yet to work with a race team that built the exhaust system before they had the other components figured.

Ask Bes... you should do it.