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Vibration/Buzzing on Accel

Sesshomurai

Ok, I'm halfway through my race conversion with plenty more to go.

I just had the JPC stainless over axles put on, along with the Kooks longtubes, off-road H pipe, Kooks side pipes and GT500 mufflers.
I have the QTP electric side pipe cutouts and they are closed.

When I press the throttle a good inch or so in 2nd or 3rd going 30+mph there is a slight to harsh vibration coming from underneath somewhere. metal on metal. I can't pinpoint it.
You don't hear it cruising along or slow accel.

Any ideas? I checked the sidepipes touching the pinch welds and made sure that wasn't it. All the fasteners are tight that I can tell.

It doesn't make the sound stopped in neutral.

So far, I'm stumped.

D
 

Sesshomurai

cloud9 said:
Possibly the LTs contacting the steering mechanism?

Hmmm. I'll have to think of a way to identify that. So could it be that when accelerating the engine is torquing into the steering column? That sounds like "a very bad thing" if it could happen. Will try to rule that out.

But actually, I don't "feel" any vibration. It's more audible and sounds aft of the transmission - 90% sure its related to the exhaust system, but everything seems so tight and snug. Also, I had a DSS shaft put on today but it made this sound before and now after, so probably not related to that either.
 
I've just read about that happening to a few guys that have installed LTs. Google it and see how they isolated it and corrected it......on my phone or I would try to find it for you.
 

Sesshomurai

Its definitely coming from behind me. The exhaust sounds and feels sturdy but there is something vibrating on accel.
I don't have rear seats or trunk liner so I'm sure any slight vibration is amplified 500x to my ears, but I'm convinced its something minor.

The mufflers are very snug. I checked all the obvious fasteners in the rear part of the car. Seems fine.

Maybe the pipes are vibrating against each other inside the ball clamp or sleeve joint? They are pretty tight though.

The only clue I have is the noise only appears under load and tapers off as the engine eases under constant speed.
 

Sesshomurai

thebull said:
Maybe something is in a bind....loosen the exhaust connections wiggle and re-tighten.

I loosened one side muffler and resealed. Even though they were very tight to the hand.
I also bent some of the aluminum heat shields so they weren't close to the chassis.

Huge difference. I can now accelerate without hearing any vibration/buzz. But under harder accel its still there. Can't hear it with the side pipes open though.

My best theory is that its the flimsy heat shields resonating from the much louder sound waves flowing from the much larger pipes next to them.
Do they serve a big purpose or can I remove them?
 
darreng505 said:
Do they serve a big purpose or can I remove them?
Race cars don't need them. ;)
 

Sesshomurai

I think the primary culprit has been identified. Even though I had to double check all the usual NVH suspects.

The frickin tow ring in the rear is loose enough to vibrate. The bigger exhaust must vibrate the chassis in just the right way. Of course its attached to the bumber/chassis and resonates in my rear compartment.

Duck taped that ring down and the vibrate on accel is almost completely gone now. I'll add some thick axle grease to the ring or something to prevent any wiggle in it.
Just happy that the exhaust is not the problem here, or valvetrain noise from it. Would drive me nuts.
 

Sesshomurai

NFSBOSS said:
I noticed my rear tow ring doesn't fit tight. I wonder if some thread tape would help tighten it up?

Yeah, that's a cleaner solution. Will give it a try.
 

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