yamaha537

alright so i figured out my exhaust from my h pipe back had a million holes in it, so i thought i would have some fun with it. i took off the mufflers and tail pipes and just ran the headers to an h pipe any maybe 12 inches off that. i drove it around just for fun, and it had no low end, because of the decrease in back pressure. so im wondering if i end up going with the "dumps" am i going to see the same issue? or is just those mufflers going to give it enough pressure. i was going to just get a whole cat back but im tight on cash, so i was looking on the dumps( just the mufflers with the turndown tip and thats it). do you guys think ill run into the problem of loosing low end, or do you think it will have enough and run fine.
thanks

mjr46

you'll be fine with dumps= no real loss of power

67mustang302

Yeah, you'll be fine with dumps. And you actually want 0 backpressure, what people THINK is backpressure is actually shockwaves that are moving throughout the exhaust system, and wave fronts are TOTALLY different than pressure. If the exhaust isn't the right length or diameter for the setup, then it throws the wave tuning all out of whack and you lose power.

yamaha537

alright thanks guys, i just wanted to make sure i wasnt going to short.

yamaha537

67mustang302, than how come i lost so much bottom end subtracting the mufflers and tail pipes? if you want less back pressure than wouldnt that not affect it?

5spd GT

You can gain excess backpressure by either having the wrongly tuned length or too restrictive an exhaust system.

This is not good for power output.

The problem in your scenario is that you did not lose backpressure, but you gained backpressure.

Unlike typical math, you actually want a negative wave to be present when the intake and exhaust valve are open at the same time. Gaining backpressure (bad) is when you have a positive wave during overlap. This can cause intake reversion, caused by either the wrong timing of the wave (positive) or a restrictive exhaust diameter or design.

I used stock 5.0L parameters with short style headers to get the following:

Best HP/TQ Tuned Collector Lengths= 13.4 , 26.8 , 53.7 , 107.4 inches long
Worst HP/TQ Loss Collector Lengths= 40.3 , 80.5 , 161.1 inches long

If you want to learn more about exhaust systems, speak with Larry Meaux. He sells a easy to use software known as PipeMax. Many "big-wigs" use it. I like it a lot.

mjr46

just buy a good cat back when you can afford it

yamaha537

damn, didnt know there was that much too it haha. i think im going to get mufflers for now. put a turndown tip on them, and if i dont like it than ill suck it up and just buy the extra piping.

mjr46

for a street car there is no reason to get that technical..if you get hung up on the little things like that..you'll never move on to more important issues like a decent h.c.i

5spd GT

There is even more to it that that. That was the tip of the iceberg...

[&:]

Good Luck!