back pressure

[MATT2007]

Ok my question is does having no or very little backpressure decrease the life of your motor people at school argue about it all the time what do you guys think my friend has had a 95 cavalier with a 2.2 and no cat and a burnt out glass pack and has put 80,000 miles on it that way

[pontiacdohc@gmail.com]

i have no idea man im looking for an answer on that too, i asked ben on the fourm he said he didnt know for sure if it was going to cuz problems or rob tq he just said it will be louder, but im looking if anyone has took the cat off there car and left the res and 2 mufflers on there grand prix 3.4DOHC and noticed any lower end tq power loss, cuz i reallly hope not mine is clogged up and dont have the 165 dollars for a high flow when i can simply just get it cut off and new exhasut from the down pipe back with Summnits new Super Turbo Mufflers for 80 bucks with the labor !!! so if anyone has done this to there Lq1 let me know what i should excpet after doing so.

[IsaacHayes]

LOL, back pressure is a myth. You don't want back pressure, but you do want velocity. Removing the cat won't harm the motor. If you gut it, you might cause some turbulence but if you go with straight pipe there you'll be fine. Your torque curve might shift some, but it's not gonna hurt the motor and will free up flow.

I say go for it, go with a bigger pipe size (with in reason for your motor). You should feel a difference. I'd go with a straight through muffler though for less restriction, like a dynomax ultraflo, magnaflow, etc.

People that hack the exhaust off right before the cat at the downpipe and loose low end grunt probably loose it mainly because they are shortening the length of the exhaust and they are loosing velocity. Unless they had full length headers they will loose some velocity. That's why a motor doesn't make power with no manifolds, it looses the velocity and scavenging affect the headers/exhaust pipe creates. It's just the exhaust hitting a wall of non-moving air...

[pontiacdohc@gmail.com]

first off i have more low end grunt at like 25% than i do 100% the exhasut guy told me the cat is clogged and that is the reason why ive seen to lose that low end tq, this motor has 83,000 miles on it, i have replace the TPS and IAC Cleaned the K&N filter new plugs and wirees, i went with the Ac Delco Rapid Fire Plugs ???? any comments on them? As of right now the setup that is being used is as follows, Jet Chip stage one(which is going soon as i get ben to make me one of his),Short Ram Intake ebay speaical i made a shield Box To cover the crosover pipe and the hot air blown by the fan (l67 thrasher type box) and for the exhasut, stock down pipe,clogged cat,stock res, and two cheap ass thrush mufflers.

What i want to do with the exhaust is Get rid of that car put in a stright pipe leave the res and put two new summnit super turbo mufflers, that are sopost to make 21 more hp and 5800 rpm then dynomax super turbo walker muffler.

[IsaacHayes]

I don't know about no 21hp, but I'm not talking about the dynomax super turbo. I'm talking about the dynomax ultraflow which is straight through and flows more. It's like a glass pack but with more packing around it so it's quieter.

I would remove the resonator if I were you. I did on my car and it didn't get louder really, just a little more rumble, and actually gave me some performance since the exhaust didn't open and get turbulance, then slam into that flat wall at the back of it and find it's way out. If you cut it off then you'll see what I'm talking about and realize it's not good for flow.

[pontiacdohc@gmail.com]

so u suggest getting rid of the cat and res. and the muffler is pretty much a choice of sound you want to an extent, the reason why i bought the summnit super turbos is that they said they have a nice sound with out being to loud.i see what your saying about exhasut just coming out and hitting a wall tho and about the res it does open up there to like 3 inch and then goes back into i think 2 1/4. so go with the no cat no res with duals?

I don't know about no 21hp, but I'm not talking about the dynomax super turbo. I'm talking about the dynomax ultraflow which is straight through and flows more. It's like a glass pack but with more packing around it so it's quieter.

I would remove the resonator if I were you. I did on my car and it didn't get louder really, just a little more rumble, and actually gave me some performance since the exhaust didn't open and get turbulance, then slam into that flat wall at the back of it and find it's way out. If you cut it off then you'll see what I'm talking about and realize it's not good for flow.

[IsaacHayes]

Yeah that sounds like a plan. The super-turbos will still flow pretty darn good, it's just more bends vs a straight through muffler. Removing the cat will make the car louder though. The resonator is just to take out certain frequencies and rumble.

The resonator in addition to getting large then tapering back down, is that it doesn't taper back down at the end. At least mine didn't. At the end it has a big flat washer, with a small hole. So from the outside it looks like a smooth taper back to your pipe, but inside it's hitting a flat wall with a hole in the center...

If you want a resonator to quieten it down before the mufflers, then put a perforated glass pack instead. The stock one sucks for flow.

But yeah I think no cat, no res, and your mufflers you should be pretty happy. Go for it.