A few weeks ago I had my stock exhaust resonator removed and replaced with a straight pipe. Ever since then my car has felt like it's not a "peppy" as it was. Almost like the power curve is flat. Also, I notice a sort of buzzing, humming noise occasionally while driving which seems to be coming from the area where the resonator was.

The exhaust note is unfortunately also not as good as I was hoping. It's ok running around 3000 to 3500, but anything more than that and it's fart-can city! Also, if you don't let your car warm up for a while before you start driving, it has a VERY bad buzzing sound above 2500 RPMs.

Has anyone else removed their resonator and felt a noticible loss in power? I am trying to figure out what I should do.

-Chris

 

Maybe a hole in the exhaust or poor welding? It would display those symptoms..

 

Shouldn't be a loss of power--but it does sound like ***.

 

Well, I had disconnected the muffler a while back and put a washer in between the bolts so there was a like a 1/16th gap between the pipes in an effort to make my exhaust sound louder. It definitely did, but now that you mention it, there was a sililar loss of "oomph" after doing that.

The way my exhaust is currently everything should be welded up nicely, but who knows, maybe there is a leak somewhere? I guess my first step should be to take it to the muffler place that did it and have them check for leaks. If there aren't any then I guess I'll have them weld the resonator back in place and see what happens after that.

-Chris

 

What happens is with exhaust, if you create turbulence in the system (ie. cuts/welds/re-cuts/re-welds) it'll slow down the normal exhaust gas movement and you'll have an increase in backpressure. I definately would NOT re-weld in the resonator, however, I would check the welds/cuts to make sure that it's smooth on the inside/outside. That's why I'm a big fan of well made exhaust systems instead of shop made ones

 

Well, I'll buy that. I think that I will however get my resonator re-welded because as 350zSpeedRacer pointed out, it does sound like a$$ without it. If I am going to have the backpressure problem, I would at least rather have the exhaust sound good.

 

Get ya the Borla or InJen to fix that back pressure problem.

 

Good idea!

P.S. can I borrow about $800??

 

Wanted to get you opinion on this y pipe!!

http://cgi.ebay.com/ebaymotors/ws/eB...912684074&rd=1

 

Actually Chris, I'll bet what's happened is that with the removal of the resonator, your backpressure has *dropped*, not increased. This engine relies heavily on backpressure for torque at the low-end. With too little back pressure, the valve overlap will allow some of the intake charge to spill out into the exhaust system before the exhaust valve closes. The stock back pressure keeps the intake charge "pressed" into the cylinder until the exhaust valve can close.

I noticed this when I installed my GReddy EVOII TD exhaust. I lose power at the low end until the RPMs build the back pressure up enough to eliminate the problem induced by the valve overlap.

Sometimes, our performance mod's really aren't!

Incidentally, there is a great article on back-pressure/valve overlap over on **********.com that really explains this whole thing well.

Good Luck

 

^ Exactly. You'll loose the "quickness" by less backpressure.

 

Knowing all the collective faults of the oem exhaust, just removing the resonator is not going to impact exhaust gas volocity. I can understand going after some power on a budget, but straight piping is not the thing to do from a sound stand point alone. You alway's want to get your "power" impression's off the car when it's less then 80 degree's out and you haven't driven in town for very long.

It is likely that the pipe narrow's down to 55mm as it goes into the oem resonator and goes back to 65mm once it passes out, that's a reduction of 3/8'. Not earth shattering, their are crush bends elsewhere on the system that do the same thing. Instead of straight piping, try installing a 18" long 4" round Magnaflow muffler as a resonator. Your oem Y-pipe is not friend for flow, consider chucking that, but watch collector size very carefully, no mismatches.

 

Actually, I'd prefer to grep -v. That's just not right!

 

Thanks for the info. I'll have to check out that article. I have actually talked to a few other people who have said the felt a drop in power too after removing the resonator. I am looking at getting the resonator replaced, or just find a complete used midpipe that I can pick up for a few dollars. Then I can see for sure if that is the cause or if it's something else that's causing the power loss.

-Chris

 

Hmmm... I went to **********, but I couldn't find this article. Do you happen to have a link to it handy?

-Chris

 

Well, I was able to obtain a new midpipe and as soon as I installed it yesterday the car is back to normal. There is a dramatic difference in the way the car accellerates now. I can't believe how much of a decrease in power it creates by replacing that little cannister with a straight pipe!

For anyone even thinking about cutting out their stock resonator.... DON'T!!! Your torque will go into the crapper!

-Chris

 

I realize that your intentions are good with this explanation... but... I hear the "backpressure needed theory" all to often and for some reason feel the need to help dispell this.

Backpressure is bad. By backpressure I refer to any pressure in the exhaust port during the CRITICAL phase of the exhaust cycle... the period that the piston rises from BDC until the exhaust valve closes. Pressure will work against the piston area to reduce power in the exact same way that it makes power.

Velocity is good. Velocity is the accelerated mass of exhaust that wants to continue in one direction... away from the engine... this encourages scavenging. MANY things effect velocity.

This is a very simplistic response to a very complex condition but rest assured... backpressure is not desirable.

 

Here Here JBrady
The "Backpressure Myth" must me stopped!

Chris

 

I'll find that article. It is very well written and directly contradicts you guys who believe that I'm full of it. .

 

UPS delivered this Y-pipe to my house today, so i will see about the quality and the fit. it is an exact copy of the Nismo/Fujitsubo, for about half the price. 2.5" inlets that merge into a 3" collector, with all mandrel bends. it is also 304SS.

Chad