backpressure

[SVX10]

I think I've gone too low in backpressure with all my exhaust mods. Can anybody tell me how I can raise it a little bit temporarily to see if mileage/power seem to increase? I just want a temporary test solution...like sticking a potato in one tail pipe

[oab_au]

Originally posted by SVX10
I think I've gone too low in backpressure with all my exhaust mods. Can anybody tell me how I can raise it a little bit temporarily to see if mileage/power seem to increase? I just want a temporary test solution...like sticking a potato in one tail pipe

What have you done to the exhaust and why do you think you have a problem.

Harvey.

[Phast SVX]

hmm backpressure.....dont you mean scavenging?

Some backpressure is actually necessary for low-end torque. Open exhausts make high-end HP at the expense of low-end torque. You either need a good compromise or a power valve, like some motorcycles.

CJ

[SVX10]

Yea I mean scavenging. It's related to backpressure and exhaust flow, so I just called it backpressure. Anyway, I have the 2.5" cat back pipes from the KC kit with 2 magnaflow mufflers. That alone should reduce backpressure. I also made the mistake of cutting out the first 2 cats and replacing with straight pipe. The guy at Midas told me one was cracked and falling apart, so I decided to just get rid of both before they damaged the third one. So, I think there may be a problem because I have a mad buzzing noise (probably a leak...I'll explore that when I have a chance to get the car up), but I also seem to have lost low end power. I have also dropped in gas mileage by 1-2MPG city and 5-6MPG highway. Finally, the check engine light comes on often. Usually it comes on after I've driven for a while and stop for just a few minutes (gas, grocery store), and restart. The light usually goes off, but sometimes it remains on. Also, probably unrelated to the exhaust, I have a problem with hesitation and stumbling when the car is cold. So, there's a whole lot of info to work with. Can you tell me what's wrong, Doc?

[Earthworm]

Ask your ECU what's wrong.

[SVX10]

I axed the ECU what was wrong, and the ECU dun said Knock Sensor #?. The same Knock Sensor that has been replaced. So, I don' trust that thar ECU. I shuud, but I don' cuz I don' wanna re-replace mah Knock Sensor.

[Phast SVX]

hmmmm welll thatr mad buzzing sound is fro mreomving the cats/resinators....install a 14" straight through resinator before the mufflers..or two smaller ones where youtook out thecats.....this will get rid of your buzzing sound as long as tou dont have a bad gasket somehwere...
speaking from experience on this subject,
phil

[SVX10]

Hmmm, sounds interesting. What kind of buzz was it. Mine is there only from about 2000-5000 rpm...was yours like that. I'd gladly put resonators where the cats were cut, but I wanna make sure its the same kind of buzz as you had. I'll also try the gasket thing firts too, cuz that costs alot less. Also, how do I pick a resonator...don't some make your exhaust sound like a$$? Do you know why this buzzing occurs when you don't have cats?

[Phast SVX]

buzzing occurs due to severe resonation, and the fact that without any sort of resontaors nothing is there to catch the the exhuast that" doubles back" in the piping......you need to get a STRAIGHT THROUGH resonator, not a glass pack., A straight through resonators has little pockets to catche the air from doubling back and keep if flowing correctly, which is is succeeded in the stock exhuast system by the beeds in the cat and the primary/sec muffler to an extent, maybe not directly speaking, will keep resination to a minimum. Ever here a honda "fart" thats becuase honda owners have no clue what they are doing and install a canister and remove the chambered resinator becuase they feel it is restrictive. They dont however know that a straight through resinator is not restrictive, especially on a NA car. You get it between certain RPM's becuase the wavelength is resinating at that range......ya physics!!....anyways im not completly accuareate on this....but as much as needed. IM me at BIGDHILLL if you want to talk about it further.... But i spent alot of trial and error getting the exhuast system on my last SVX to growl and not fart or blurb...ask svxboy about it....it was mean....

phil

[immortal_suby]

Originally posted by SVX10
Yea I mean scavenging. It's related to backpressure and exhaust flow, so I just called it backpressure. Anyway, I have the 2.5" cat back pipes from the KC kit with 2 magnaflow mufflers. That alone should reduce backpressure. I also made the mistake of cutting out the first 2 cats and replacing with straight pipe. The guy at Midas told me one was cracked and falling apart, so I decided to just get rid of both before they damaged the third one. So, I think there may be a problem because I have a mad buzzing noise (probably a leak...I'll explore that when I have a chance to get the car up), but I also seem to have lost low end power. I have also dropped in gas mileage by 1-2MPG city and 5-6MPG highway. Finally, the check engine light comes on often. Usually it comes on after I've driven for a while and stop for just a few minutes (gas, grocery store), and restart. The light usually goes off, but sometimes it remains on. Also, probably unrelated to the exhaust, I have a problem with hesitation and stumbling when the car is cold. So, there's a whole lot of info to work with. Can you tell me what's wrong, Doc?

I have open pipes from the manifolds then a y-pipe, then a single glasspack and open pipes back to a flowmaster 1 in 2-out muffler. I still get about the same exact gas mileage - 26 highway and around 19-21 city. No CE light yet. I feel that I have lost some low end torque measured on the butt-o-meter and the way my wife's svx jumps off the line a little quicker than mine but I catch back up and equal or pass her's in the top end. Her's is stock.

[wawazat??]

Originally posted by immortal_suby


measured on the butt-o-meter and the way my wife's svx jumps off the line a little quicker than mine. Her's is stock.

Hey Matt, when was the last time you had your butt calibrated?

Like my wifes car, Kim's car is faster than Matts!

[immortal_suby]

I should have known you'd pounce on that one

Todd: 2
Matt: 1

I'll be watching...

[wawazat??]

Bring it brother!

Todd (fat old non-threatening white guy trying to sound tuff)

[mbtoloczko]

Originally posted by immortal_suby


I have open pipes from the manifolds then a y-pipe, then a single glasspack and open pipes back to a flowmaster 1 in 2-out muffler. I still get about the same exact gas mileage - 26 highway and around 19-21 city. No CE light yet. I feel that I have lost some low end torque measured on the butt-o-meter and the way my wife's svx jumps off the line a little quicker than mine but I catch back up and equal or pass her's in the top end. Her's is stock.

Which model Flowmaster did you use? Did you dump all the Cats?