Resonating vibration between 2200 and 2500rpm, any ideas?
04-27-2011 | 03:19 PM
#16
Nordschleife Master
Joined: Mar 2005
Posts: 8,809
Likes: 0
From: In the garage trying to keep boost down
Constantine, thanks for your thoughts. That is what i figured also.
Bret, motor mounts are brand new Rein Auto which are basically the OEM mounts with the numbers ground off, trans mount is the LR semi-solid. The engine is probably sitting 5mm or so higher because the original mounts were both at the wear limit pretty much. This is why i figured it could have been an exhaust, bracket, wastegate rubbing on something due to the extra height. Have not seen anything obvious though. I have not thought of putting it on stands and testing it that way.. i feel a bit nervous running her up to 3k or so with it in the air like that but i will give it a shot
. Maybe i can borrow my buddies lift for that.. =D.
I did check all the hard lines from the bottom of the fender well back and also the hard brake lines back there. Did not see anything obvious. I did put a piece of silicone hose over the fuel feed line around where it bends across the frame rail (near the caster block). I am going to pull the fender liner off today and insulate all the lines using some cut up silicone hose also. I know they were touching a bit up here from when i installed the rail and fittings last week.
I dont think its likely it is the fuel rail but i am out of ideas and it is one of the new things added on. What i may try and do possibly tomorrow is hook up my old fuel rail to see if the noise is still present. I have my old Aeroquip lines still, need to take a ride to the Parker store and pickup some -4 and -8 AN fittings an an -6 to -8 AN adapter, this way i can hook up my original rail.
I still need to check the trans mount by actually getting a wrench and socket on it, but i used all new locking hardware when installed and nothing looks like its moved when i stuck a mirror up there.
I am totally out of ideas and really not sure what i am likely overlooking. Wish i had more 944 knowledgeable people close-by!
Bret, motor mounts are brand new Rein Auto which are basically the OEM mounts with the numbers ground off, trans mount is the LR semi-solid. The engine is probably sitting 5mm or so higher because the original mounts were both at the wear limit pretty much. This is why i figured it could have been an exhaust, bracket, wastegate rubbing on something due to the extra height. Have not seen anything obvious though. I have not thought of putting it on stands and testing it that way.. i feel a bit nervous running her up to 3k or so with it in the air like that but i will give it a shot
. Maybe i can borrow my buddies lift for that.. =D.I did check all the hard lines from the bottom of the fender well back and also the hard brake lines back there. Did not see anything obvious. I did put a piece of silicone hose over the fuel feed line around where it bends across the frame rail (near the caster block). I am going to pull the fender liner off today and insulate all the lines using some cut up silicone hose also. I know they were touching a bit up here from when i installed the rail and fittings last week.
I dont think its likely it is the fuel rail but i am out of ideas and it is one of the new things added on. What i may try and do possibly tomorrow is hook up my old fuel rail to see if the noise is still present. I have my old Aeroquip lines still, need to take a ride to the Parker store and pickup some -4 and -8 AN fittings an an -6 to -8 AN adapter, this way i can hook up my original rail.
I still need to check the trans mount by actually getting a wrench and socket on it, but i used all new locking hardware when installed and nothing looks like its moved when i stuck a mirror up there.
I am totally out of ideas and really not sure what i am likely overlooking. Wish i had more 944 knowledgeable people close-by!
04-27-2011 | 11:46 PM
#20
Rennlist Member
Joined: Jan 2004
Posts: 314
Likes: 6
From: Tenn.
Torque sensitive, not speed related, RPM sensitive, if it was the rail I would think it would be more consistent across a broader range of RPM. If it just that RPM range regardless of gear, it shouldn't be related to half shafts as those will increase rotation with road speed. Possible something resonating on intake/exhaust which would stay rpm related regardless of gear/speed. If you go to the sensitive rpm band and do a light throttle opening to hold rpm steady maybe slight uphill so you can keep it in the resonance, it might give you more time to listen and diagnose/pinpoint source.
04-28-2011 | 11:16 AM
#23
Three Wheelin'
Joined: May 2009
Posts: 1,507
Likes: 4
From: Carson City NV
+1,my NA was doing this, I did the belts, took it into the shop for adjustment and the guy said the B Shaft belt was 180 out. The marks on the B Shaft belt are kinda odd!
04-28-2011 | 11:38 AM
#24
Three Wheelin'
Joined: Feb 2007
Posts: 1,408
Likes: 0
From: Indianapolis,IN
Wouldn't the balance shafts being off cause it to shake in neutral, also? Not that they couldn't be off, but the problem occurs under load. I'm not sure the BS's care/know if a car is under load or not.
If it won't make the racket with the clutch "out", my opinion is it probably eliminates engine, clutch, TT and input shaft.
If it won't make the racket with the clutch "out", my opinion is it probably eliminates engine, clutch, TT and input shaft.
04-28-2011 | 12:17 PM
#25
Three Wheelin'
Joined: May 2009
Posts: 1,507
Likes: 4
From: Carson City NV
It was so long ago I can't remember but it was kinda odd, I though tires at first.
I posted on Pelican, see if I can find it.
Oh I'm chip18 on there, yeah I'm a dumb *** different user name on there.
Got it look at post 251 here:
http://forums.pelicanparts.com/porsc...er-hood-2.html
I think they talk about the marks in here also, something weird about them?
Not say that this is your problem but it is the first place I would look especially if it started after a belt change?
I posted on Pelican, see if I can find it.
Oh I'm chip18 on there, yeah I'm a dumb *** different user name on there.
Got it look at post 251 here:
http://forums.pelicanparts.com/porsc...er-hood-2.html
I think they talk about the marks in here also, something weird about them?
Not say that this is your problem but it is the first place I would look especially if it started after a belt change?
04-28-2011 | 11:56 PM
#28
Addict
Rennlist Member
Rennlist Member
Joined: Feb 2002
Posts: 5,384
Likes: 1
04-30-2011 | 01:29 AM
#30
Three Wheelin'
Joined: May 2010
Posts: 1,956
Likes: 9
From: Edmonton, AB
Turbos don't come with rubber clutch centres. So that's not it. And it wouldn't matter when it's engaged: once a clutch is engaged, it's engaged, unless the clutch/flywheel is unbalanced. But just from looking at TechnoDuck's track record, I doubt he would be careless enough to have an unbalanced clutch.
My bet is either your BS is off, or your tranny mounts are loose. I would check the BS's first though. But it wouldn't be hard to find out if your tranny is dangling by a thread just by giving it a good nudge with your foot.
As a last resort, it could be a loose exhaust mount, where the engine produces a certain resonant frequency that shakes the **** out of the car (RPM based)...
GL
My bet is either your BS is off, or your tranny mounts are loose. I would check the BS's first though. But it wouldn't be hard to find out if your tranny is dangling by a thread just by giving it a good nudge with your foot.
As a last resort, it could be a loose exhaust mount, where the engine produces a certain resonant frequency that shakes the **** out of the car (RPM based)...
GL