New gears and exhaust...Killer!!

So i see this is a big issue as well with everybody else. So if i install a resonator on each side(Where the old cats where) Before the 2into1 pipe this noise will go away? It sounds good all up until the resonating starts, then it sounds like a cat stuck in a tin can.

[SVXRide]

What's the engine at (rpm-wise) when "the cat gets stuck in the can"? You may just have to extend the length of the primary pipes before you join them together with a "Y"
-Bill

[mbtoloczko]

Originally posted by SVXRide
What's the engine at (rpm-wise) when "the cat gets stuck in the can"? You may just have to extend the length of the primary pipes before you join them together with a "Y"
-Bill

I think that Bill has the correct idea. This may be one possible way to stop the resonance from forming.

[odepaj]

haha, i have that same problem on my car. im thinking about running duals, but i read somewhere that that creates a "two raspy 3cyl. engines running at the same time" sound and i deffinetly dont want that. any suggestions?


dustin

[SVXRide]

Originally posted by odepaj
haha, i have that same problem on my car. im thinking about running duals, but i read somewhere that that creates a "two raspy 3cyl. engines running at the same time" sound and i deffinetly dont want that. any suggestions?


dustin

A couple of us are playing around with different exhaust theories that drive the final design of the exhaust system and the final verdict is still out. Right now I can only suggest that you extend the duals to at least 60 inches back from the engine block and then tie them together with a preformed piece of Y pipe. 2.5 inch pipe from the pipe back to a magnaflow muffler (or similar) would be a start.
-Bill

[mbtoloczko]

It may have to be a bit more than 60 inches. I'm at 58 inches right now, and the car sounds like crap from 3000-4000 rpm (and there is a slight drop in power too). I think 70 inches or so will be necessary... about the location of the factory pre-muffler.

[mbtoloczko]

I just looked at my notes. If this is a constructive interference phenomenon occuring with the next cylinder firing, then the way to minimize the interference is to either place the y-pipe at about 120 inches from the manifold (past the back of the car?) or place it at around 24 inches from the manifolds.

[SVXRide]

Originally posted by mbtoloczko
I just looked at my notes. If this is a constructive interference phenomenon occuring with the next cylinder firing, then the way to minimize the interference is to either place the y-pipe at about 120 inches from the manifold (past the back of the car?) or place it at around 24 inches from the manifolds.

Would you make up your mind already?
-Bill (almost done reading the 4cyl aircraft exhaust system article...)

[odepaj]

i looked up some pictures of the stock exhaust, and it turns out i basically have the stock exhaust with two resonator tips at the very end instead of the stock secondary muffler. dont blame me if this is a bad thing the previous owner had this done. opinions about this?




dustin


ps. i was wrong earlier, my exhaust doesnt resonate at the same rpm's as yours do, i just have a rattle somewhere at 2500-3000 after you let off the gas.

[oab_au]

Connecting the two engine pipes together with a Y pipe, is not the best way for engine performance.
The two pipes should enter a box of some kind, to drop the gas pressure, before they join. If a Y pipe is fitted to the engine pipes, the high gas pressure from one, is going to enter the other pipe, to cause a high pressure in the other exhaust manifold.

The way they join now is the two pipes enter the space in the front of the second cat, where the gas pressure drops. This has the pipes joining in a low pressure area, to prevent one from affecting the other.

If you are dividing the system into two pipes, the dia of the pipes should stay the same as they are now. The idea that because there is only three cylinders on the pipe now, it can be smaller is wrong, as the cylinder size, is what sets the pipe size, not the number of cylinders. Only one cylinder's exhaust is using the pipe at a time.

Harvey.

[SVXRide]

Harvey,
I should have been more specific...the Y connection I suggested would feed into the stock (or aftermarket high flow) secondary cat, thus achieving what you've noted (given that the primary cats have been replaced by straight pieces of pipe). Just trying to keep the air a little cleaner and minimize the chance of anyone not passing their state's emissions testing.
-Bill

[mbtoloczko]

Originally posted by SVXRide


Would you make up your mind already?
-Bill (almost done reading the 4cyl aircraft exhaust system article...)

Well, I had the resonator (expansion box) removed from my exhaust line today. The expansion box was in the location of the OEM expansion box. The expansion box I was using was a hollow box (7"W x 3.25"T x 14"L) with a single "V" deflector towards the rear. With the expansion box removed, the resonance at 3000-4000 rpm was greatly reduced in loudness. I think that the exhaust pulses were slamming into the "V" deflector and making a hell of a lot of racket. I also think that if I put a standard muffler style resonator in the position of the expansion box, the exhaust will sound pretty nice.

BTW, removing the expansion box had zero effect on the butt-dyno HP estimate.

[SVXRide]

"OEM expansion box" = OEM resonator??
-Bill

[SVXRide]

Originally posted by odepaj
snip*

dustin


ps. i was wrong earlier, my exhaust doesnt resonate at the same rpm's as yours do, i just have a rattle somewhere at 2500-3000 after you let off the gas.

Dustin,
The rattle could just be from your heat shields. Do you still have the stock primary cats? You might want to get the car up on a lift and see if anything is loose.
-Bill

[mbtoloczko]

Originally posted by SVXRide
"OEM expansion box" = OEM resonator??
-Bill

Yep.