back pressure??

[97ForMuLa]

i am running midlength headers and open y pipe, no cats no muffler. the car feels strong, but i have the suspicion that i am not getting enough back pressure... can anyone tell me their thoughts??? thanks.

[KissMyWhtSS]

I'd throw a pipe on it and throw a muffler/dump before the axle.

You moved your powerband up a bit by removing the cat/muffler. Your car won't have as much initial power but once your into it you'll gain it back up top.

In other words your fine, my biggest concern would be exhaust temps under the car depending on where your y-pipe lets out.

[jakesz28]

Back pressure is over rated. If the noise doesn't bother you you want it as free flowing as possible.

[bad88camaro]

depense on the build on a n/a you need back pressure for low end torque
to much b/p is bad to little is bad to there is a balance between to much/little for what you r doing street/drag/roadracer
if nos or f/i freer the better

[YZF]

From the Y-pipe, put a chunk of 3" and dump it with a turn down right before the axle. And you're game on.

[96LT1355Z28]

Here's what I did. 3" pipe form the Y to a 1 chamber Flomaster then a turndown. It's still loud but with a deeper tone and not the "open headers" sound.

http://ltxtech.com/forums/attachment.php?attachmentid=238&d=1235429824 (http://ltxtech.com/forums/attachment.php?attachmentid=238&d=1235429824)

[Wilburbeest]

Back pressure is a common misconception. If our engines needed back pressure for low end power then you would loose low end power going from a cat-back and shorties to duals and LTs. I have heard people say that they felt they had less low end from that before, but I've never seen a dyno agree. Yes the power band is shifted up some with more power up high, but not any less down low. Maybe if the car isn't tuned for the LTs it might lose some because the O2s are moved further back and cause the engine to run rich. That would make sense. If I'm off my rocker somebody PLEASE CORRECT ME. What you are after is scavenging, which is the vacuum effect from your headers/exhaust. I notice that you say the car feels strong. Is there something particular that doesn't feel quite right? Sometimes with headers or a loud exhaust the stock knock sensor will pick up false knock. Now that will kill off some power.

[StangeatinZ28]

i lost a shitload of bottom end when i ran longtubes and open y for a while, and picked it all back up when i put the cat back on

[jakesz28]

Back pressure is a common misconception. If our engines needed back pressure for low end power then you would loose low end power going from a cat-back and shorties to duals and LTs. I have heard people say that they felt they had less low end from that before, but I've never seen a dyno agree. Yes the power band is shifted up some with more power up high, but not any less down low.



I agree. Most of the time all you need is a 18" extension on a set of open headers to get the most power you can get.

Some exhaust systems flow well enough not to hurt the performance on some of the more common builds. But if it's and all out race theres no need for back pressure.

[Spartan7]

i lost a shitload of bottom end when i ran longtubes and open y for a while, and picked it all back up when i put the cat back on

What do you mean by "open y", you mean just dumping out the y-pipe?

I ran open headers for a week, and yes, bottom end suffered. But it's because the O2's are exposed to more air and the car will run pig rich causing a loss of power. But back pressure on a fuel injected car is NOT a factor.

Read this: http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

[jakesz28]

What do you mean by "open y", you mean just dumping out the y-pipe?

I ran open headers for a week, and yes, bottom end suffered. But it's because the O2's are exposed to more air and the car will run pig rich causing a loss of power. But back pressure on a fuel injected car is NOT a factor.

Read this: http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm



18" extensions on those long tube headers would have kept the fresh air off of the o2 sensors.


You should see my low end wideband recordings without the extensions.

[Spartan7]

18" extensions on those long tube headers would have kept the fresh air off of the o2 sensors.


You should see my low end wideband recordings without the extensions.

I only did it because I didn't have enough time to finish my header install. That was a fun week though. :D

[97ForMuLa]

yes dumping right out the y pipe. i dont have either of the rear o2 sensors in and i know its running really rich cause its backfiring a shitload. gears are going in next weekend then tune.

[JohnnyFormula]

What do you mean by "open y", you mean just dumping out the y-pipe?

I ran open headers for a week, and yes, bottom end suffered. But it's because the O2's are exposed to more air and the car will run pig rich causing a loss of power. But back pressure on a fuel injected car is NOT a factor.

Read this: http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm


Very good read and good way to explain it :metal:

[StangeatinZ28]

What do you mean by "open y", you mean just dumping out the y-pipe?

I ran open headers for a week, and yes, bottom end suffered. But it's because the O2's are exposed to more air and the car will run pig rich causing a loss of power. But back pressure on a fuel injected car is NOT a factor.

Read this: http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htmyeah just dumping off the y-pipe. but i agree with you