sergiomartins

http://uk.youtube.com/watch?v=3AX4D2bTX-4

Im very happy with the DIY engine rebuilt in the summer,the car pulls very strong.
Also can be seen the vibration problem ive been trying to figure out but to no avail. you can see the gearshift shaking.
as i reported in this tread.
https://rennlist.com/forums/924-931-944-951-968-forum/428167-need-help-gurus-diagnose-vibration-prob-please-need-everyone-s-opinions.html

So any ideas about the Vib prob?

Jaap968

Hi,

In your original thread you say the vibration starts to change at 2900 rpm and disappears afters 3100. This would be the variocam switching point (for no or very low load). So what happens if you disconnect the variocam and rev past this rpm range. Does the vibration still disappear?

Jaap

future

Thats a good point

PorscheDude1

The variocam activates at 1500rpm and deactivates at 5500... I don't see why it would make a noise in the 2900 to 3100 range.
The intake manifold produces positive pressure @4100 rpm.

Jaap968

Activation of the variocam depends on many variables and can indeed start as early as 1500 rpm but will always be active from 2900 rpm till 5500. So if he did the vibration test with the car stationary the variocam probably activates around 2900 rpm.

Jaap

PorscheDude1

Ok

Damian in NJ

Can we assume the car didn't vibrate before?

sergiomartins

Hi, regarding the vibration, 2 separate things happen,
1st
At idle the car seems to have a slight vibration like its a missfire, but its not missfiring, this can be felt thru the whole body of the car, even the lights sometimes seem to be shaking. Also felt in the driver seat and also the gear shift vibrates. this vibration is at higher frequency.

the 2nd the vibration on the gearshift only appears between 2900rpm and disapears at 3100 rpm, but its a complete diferent from the 1st one.

Thats what throws me off, the car revs happy to 7000 rpm doesnt miss a beat, i fully rebuilt the engine in august and still have the same problems,
Re-timed cams and belts again to no avail.

The car didnt vibrate before at all, it started when on a road trip the balance belt broke , but i didnt noticed at all, until a shop put one back on, this is almost 18 months ago, since there its been on the 3rd belt, 2 garages, 1 engine rebuilt and im starting to loose hope.

austex

Although your Balance belt marks may line up you may still be out of balance, have a really good look at the balance shaft drive gears on both the upper and lower shaft to make sure you have the keyways in the right spot, they can be lined up two different ways and it must be spot on.

LTCMontana

THis is a classic symptom of a motor mount going bad. I've felt it at those same RPMs in a 944.

FRporscheman

I was going to say MM as well, or tranny mount.

sergiomartins

My first instinct was the MM and the gearbox mount , they were changed with original parts. no change
The sprockets from the shafts were taken out and both keyways are pointing up, on the upper shaft the "O" is top, and on the lower the "O" is down (upsidedown).
sound right? right?. no change
keep those ideias coming plz

PorscheDude1

Never assume anything.

PorscheDude1

The DMF is very heavy, and probably slightly out of balance.

I would have the new DMF checked for balance.
If you do have it balanced, be sure to have it done with the pressure plate attached.

sergiomartins

Well it cant be the DMF cus i changed it with the clutch kit, as an atempt to solve this as well. but even if not balanced it wouldnt shake like this would it? are they balance from factory?