Looking for thoughts here. When I hit the throttle hard my my XKR I hear a "buzzing sound" coming from the engine. It could best be described as a power saw sound. I can drive hard but really only get the sound when I really open the throttle leading me to think its blower/intake related. Not sure if it effects power simply because when I hear the sound I back off the throttle.

Not sure how to attach audio clips but this link is a quick recording of the sound.

https://fastlanedocs.box.com/s/4uaxr...jf4c3tjalqvs8c

Any thoughts before I start digging deeper?

 

I'm sure somme knowledgeable folks will drop in soon but in the mean time I would recommend using the search button for an advanced search for "supercharger by-pass valve". It is possibly the source of your noise at full throttle.

 

Gave up trying to get audio... so, failing cat(s)?

 

There is s solenoid in the air box that opens to allow additional air when you're at full throttle. From memory it works with the ignition on and the engine off so you may able to fault find it easily. Key on, floor the pedal, you should hear the click of it operating and it could be the source of your buzzing.

 

No Air Box solenoid on 4.0 Liter XKRs,

Try his link for Sound:

https://fastlanedocs.app.box.com/s/4...e/223031108408

Don't know what the sound is but my 2000 XKR does NOT make that sound.

It could be a bad bearing in the Supercharger Drive.

It could also be the Supercharger Bypass Valve opening when it shouldn't.

 

Yea, I really noticed it after I removed the stock intake and went to a CAI so who knows if it was happening before and I just didn't hear it.

I suppose removing the supercharger is a good starting point, I can see if the rotors are contacting each other and make sure the bypass valve is functioning properly.

 

Could be your answer right there. The stock intake has those stub pipes for a reason. Is your CAI just another air box, or does it have a pipe to the throttle body?

 

It is of course your vehicle but before I would tear off a supercharger I would remove the belt and rotate things by hand and see is you have any bearing problems. fmertz is probably right those stubs on the intake were silencers for noise, but my vote still goes to a faulty bypass vavle.

 

Odd, am not thinking about the supercharger though, but more about something touching something else. Remember when you put full torque on the engine, it turns a little (to the right side), so that could explain that only under these conditions you hare this noise.

 

interesting, I am trying to think what might be rubbing. the sound is clearly not under the car so driveshaft or exhaust is out of the question. It's too close to the dashboard to be anything on the front of the engine and since I installed a larger crank pulley the noise actually got louder and easier to replicate (less throttle needed) so I am back to something intake related. To answer the intake questions, I never had an airbox, the car had a cone filter when I bought it I moved the cone to the fender and replaced the factory intake tube with a 3" aluminum pipe so yes I would lose the benefit of silencers but this is not typical intake sounds.

I will make another recording and post it up later today so you get a better idea of the sound after the pulley changes.

Thanks again for all the input, we really have a knowledgable group on here.

 

How about a failing motor mount allowing contact with the hood?