backpressure arguement

[camaro_zach]

Now, is it true that you get less torque with the cat off? that is bad for 1/8 mile times, correct? Now, when i had my cat off, my car quit on me once (when it was an auto) and backfired once. Thats because of the lack of backpressure. ALso, i was able to light up my tires WITH the cat a lot easier. Now, the arguement was over the fact that "no matter what, its how fast you can get the fuel in and out of the car" and i said yes i know, however, the v6 doesnt have enough HIGH output to take advantage of this. He then said the reason my car quit once and backfired was because of the comp, not the cat. So hes saying that if i had my comp reprogrammed it wouldnt do that, and it would take advantage of the no cat. (i agree with the last part)

So basicly, tell me whatsup, good, bad, and why. lol, thanks.

[bluecmaro96]

if you remove the cat you instantly fried an o2 the only way around that is o2 simms. magnus ran an open y pipe with o2 simm and he gained 2 mph and .2 in the 1/4

[camaro_zach]

Ok, do you think that with any kind of computer programing it would benefit more? and my o2 sims are fine now that i put a high flow cat on it.

[strange_trp]

to an extent, lower exh backpressure will result in decreased low-end torque. you will make up for this with increased top-end HP and tq at peak.
remember that there is a short period of time when both the intake and exh valves are open. each combustion event causes one "high pressure" pulse in the exhaust system, followed by a slight "low pressure" pulse. this low pressure pulse helps to draw in more air/fuel through the intake valve, since both valves are open. when you decrease exh backpressure, you lose much of this "scavenging" effect, resulting in reduced low-end torque.

my situation: most of the driving i do is around town and some interstate. i like the feel of hard acceleration off the line. for my purposes, i like to keep the low-end torque instead of exchanging it for top-end peak HP that i rarely ever see. like everything involving modding, it depends on what you're looking for. depends on what you want your particular car to do.

[Camaro Bob]

I felt a difference in off the line torque, and high end horse power when I put a straight pipe in the place of my Catalytic converter. And, it sounds way meaner. I like it, but I don't have smog here. I don't think I lost any torque, but I'm pretty sure I gained some. It sure feels like it, but I don't have a dyno in town, so I couldn't be sure. [img]graemlins/burnout.gif[/img]

[MustangEater8251]

Magnus is in a 3.8l, isn't he running the duel sensor thing before and after the CAT?

3.4L have the sensors on the Y-pipe before it meets.

Gutting the CAT will not give you a total loss of backpressure as long as you have a muffler, maybe even an I-pipe.

I have run with no I-pipe muffler or CAT, and my times were very slow, loss of topend and lowend. I was like .8 secs slower, my best times are with the I-pipe off but the CAT on. And recently with my ful exhaust on it feels faster but I have to get it to the track.

As for the backfire cuz of no CAT? I ran no CAt I-pipe or muffler on my car for nearly 2 weeks. No backfires, just normal popping.