Ok I just noticed a new noise today on hard acceleration, if I drive it easy I get no strange noises. Symptoms as follows:
- definitely coming from the front
- any speed or gear, likely up to about 70 or so, as much as I have tested
- engine revs freely and does not make the noise at standstill
- easier to make it do it in lower gears as I can accelerate harder
- It almost sounds like that vibration sound you get when you push a wooden chair with no castors or other leg pads across a wood floor (that's the best I can do on a description, sorry)

Recent work done:
- top motor mount replaced under warranty as it was leaking. (Belt slipping?, but I do not have any experience with a slipping belt, I thought they squealed when they slip and this is definitely not doing that. Anyway, I have a 15% pulley with a 3 month old Napa 060535 belt with 7/8 hole showing so I certainly do not expect to slip. However, is it possible that the bleeding motor mount hydraulic fluid has soaked the belt and causing it to slip even though it is tight?)
- Other warranty work included front control arm bushings.
- I just added an X-brace, but I am sure that is unrelated.

Possibilities:
- Slipping SC belt
- Slipping clutch, still on original
- Some kind of suspension something?

Next step, I need to go for another test drive and pay attention to the boost gauge when it is making this noise.

BTW, power and tq are around 245whp, and 195ft-lbs. This is an '06 JCW car with only 17K miles on the clock. So, it has the limited slip diff and big brakes.

Thanks for any advice............

 

Sounds like drive shafts to me. Bad CV joint.
Also, just make sure the wheel studs are not loose. Check only by putting a wrench to them as they could fool you otherwise.

Do you get any of this when you let off the gas at speed?

 

I only get it when under hard acceleration. I did get a somewhat similar sound when coming off the gas, a few months back and that actually was a loose front wheel, thanks to the dealership. I was lucky the wheel did not leave me.

 

Then sounds like a bad CV

 

OK, new theory........... how bout the RMW street header vibrating on the X-brace? It seemed to clear plenty enough, but the engine can really torque under WOT.

Time to crawl back under there and remove the X-brace, look for missing paint, and go for a another ride.

Just came back from a ride and the boost gauge seems fine , I am still getting full boost, and no boost issues when the noise is induced.

Does anyone know if the RMW shorty header and TSW X-brace are compatible?

 

If you don't find anything, listen to onasled. It does sound like a bad cv.

 

OK, I guess it could be a bad CV, but I thought the first sounds they make are at low speed and hard lock or close to hard lock steering wheel, left or right. Also, I would not expect a CV to go out with only 17K, both boots are still good. But then again, I also did not expect the motor mount and control arm bushings to go at 17K, and they were just replaced under warranty.

 

OK, we have a winner! With the ~245whp/195ft-lbs of my engine the RMW shorty header and the TSW X-brace are not compatible with stock motor mounts and no additional engine dampening.

The rear of the cat is smacking right on the top of the plate/gusset on the 'X'.

Tomorrow I will install the TSW engine damper up top. If it really works then my problem is solved.

I am sure the lower mount urethane inserts would also go a long way toward reducing the engine motion enough to eliminate this strange noise (actually a vibration) but I just can't stand the NVH transmission to the cabin side effect.

 

Update, the TSW engine damper is helping! Even with the as shipped 'street friendly' setting from TSW, the engine movement and therefore the cat and X-brace vibration was reduced.

I have made a few adjustments to the damper, dialing in more preload to increase the dampening affect and the vibration is about 90% gone. I can just hear/feel it under the most extreme pedal applications and then just in first and second gear. I still need to test my last adjustment. So far , I have increased the preload by 1 and 1/4 turns.

I am trying to inch up to the proper setting as if I go too far I will introduce excessive NVH and that aint good.

 

Terry: That lower mount will also help movement a lot. I have had a top damper thingy for a few years and since I put the lower mount insert in, the movement has reduced considerably. Now if only we could get a new mount to replace the hydraulic leaker...

 

Good Dr, welcome to the thread and yes, I expect it could be very valuable in reducing this vibration, but I am very reluctant.

I already have the Madness lower inserts and the added NVH is just crazy on my car. The OEM rubber is nice for isolation, but it certainly does allow more movement. If I can't get the dampening I need with the TSW top damper alone I might try to put in only one side of the urethane insert, maybe that is a happy medium.

The nice thing about the TSW unit is that the firmness factor is adjustable, so hopefully I can tune in to a sweet spot with no vibration and minimal NVH.

Other options include.....
1. Change back to stock header(NO!), or maybe the RMW race header, tempting for sure, but then I also will need to get a new catback (too expensive)
2. Remove the X-brace or modify it ? No, I don't want to do this either, the goal is to get it on the car, not take it off. Howver, the fitment issues are very frustrating.

Oh, and I like your new tag line............I don't use that word very often, maybe cause it is not really a word.

 

Yes, I discovered that he "invented" it in 2000 and has used it repeatedly throughout his terms usually in regard to the press. He used it again in his speech this morning (Jan 12, 2009). At least he thinks it's a word...

 

c'mon doc time to beat up on the masia now after all his campaign promises are dropping like flies ,. think he got the big boy talk behind the scenes . oddly clintonesc.....sorry but those tax cuts cant happen right now ....lol . same crap different guy .

 

Update, 98% of the vibration/fitment issues are tuned out now. I have added 1.5 turns on the TSW engine damper and added one large washer each at the rear X-brace mounting points. This slightly moves the X-brace down, lower and further away from the cat.

So now, instead of the engine rotating in position as it torques the mounts, I have a super strong mount on top and still weak on the bottom so I guess it is kind of pivoting from the top now, with the bottom of the engine still wanting to move forward under heavy acceleration. Overall it might be better to add some strength on the bottom and maybe back-off on the top some.

I think I will try to add half, or rather one side of the lower urethane bushing inserts, such that I might be able to back off on the TSW damper a little. At the present damper preload adjustment it seems to transmit a bearing noise or whine into the cabin, no not a nice SC whine, this is more of a noise.

Hopefully I can find a sweet spot, where everything plays together nicely.