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Tough Technical Q?

PaulHere

PaulHere

PCGB Member
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Can anyone answer this technical query from a 924 Turbo S2 owner?

Could you please tell me if you know if porsche ever changed the crank/ignition-reference point on any of the 924 turbos.
I have a series 2 924 turbo, it has had it's engine changed with another turbo engine from another series 2, although this engine came without a flywheel.
After the garage fitted the engine, and then consequently fitted my flywheel, they could not get the marks from the crank to align up with the marks from the flywheel ,no matter what they did, all 6 positions were tried but to no avail. Both engine codes are 3103,sugesting that they are indeed series 2, so why will my series 2 flywheel match up with the crank mark, with no.1 piston at tdc, but this one won't.
I have been told even if i had used a series 1 engine block, the crank would be in the same position as it was never changed, is this true?
I have asked all the so called experts ,and nobody knows the answer.
Any ideas, any help would be most appreciated.
Many Thanks.
 
I have no idea why the timing marks are not aligning, that sounds a bit wierd and maybe thats why there was no flywheel with the replacement engine.
Where did come from, they may be able to shed some light on it.

I can confirm that the crankshaft and bearings are the same used in the 924, 924 Turbo S1 & S2 and the Carrera GT (M31.03/50), the flywheel for the '81 onwards Turbo should be part number 931 102 206 03, the GT had a different flywheel 931 102 206 01.
 
The part number for both the mk 1 turbo is 931 102 205 05.
For the mk 2 it is 931 102 206 03
For the Carrera GT it is 931 102 206 01

so there are three possible flywheels.

The mk1 used conventional ignition, the mk 2 / GT the Siemens DITC system with a flywheel sensor. A mk 1 flywheel will NOT work in a mk2 car as it doesn't have the modification to trip the pulse transmitter.

So far as I know there is no difference between the Carrera GT 31/50 and mk2 31/03 flywheels, they are interchangeable, but use different clutch plates.

All cars after engine XK 003213 use the same crankshaft.

In other words, it should work ! Remember the flywheel will only attach in one position

(copied from the other thread)
 
Here is a bit more info on the problem.

This is the history, i purchased an engine from a breaker called Porsh-apart,i asked him for a series 2 engine.
The garage my car went to is okay they are not specialist's.
They removed my old engine, and fitted the new one, the problem came about when they installed my flywheel off my series 2 engine, and although it fit straight on they couldn't get the position right on any of the 6 holes.
They said that when no. 1 piston is at tdc,and in line with the crank, it will not line up with the flywheel mark at all, they say now matter what they do it is about 30 degrees out, so obviously it will not start.

My dilemma is this if my engine is a series 2, and this new one is a series 2, why are the crankshaft marks in a different place, they say the crank looks in a different place than on my old engine.
I have never heard of this before, and i asked around to see if the engine could be a series 1, although i was told even if it was the crankshaft, and reference point would be the same.
I looked on the net, and phoned a porsche dealer with the engine numbers, which both begin with 3103, thus meaning they are both series 2 ,and it was confirmed they are both series 2.
So why this problem ?or is it the garage?, they say if i drill the flywheel, they can then get it to line up.
Please tell me what you think, should i take it somewhere else, a specialist, or did they change the ignition ref-point, or could have the engine be modified i have written and spoke to other people about this, and nobody knows the answer.
Any info would be of help i am at a loss.
Many Thanks.
 
You say both engines are 31/03, and both other people as well as myself have advised that the crankshaft is the same for NA 924, S1 931 and S2 931.

I think you need to be changing garage....... do NOT drill the flywheel or crankshaft.

I have just opened my 924T workshop manual at page 13-2, it says, and I quote

"As from 1981 models the flywheel has a press fit on the crankshaft. Consequently heat flywheel to 60 degrees C for installation"

The flywheel should have 6 holes for the retaining bolts. In addition there is a locating dowel / mark between two of the bolt holes on the flywheel. This should line up with a similar mark on the crankshaft when the crankshaft is at TDC.

Remember the 931 engine is not installed vertically..... and so even if the engine is on an engine stand at the angle of installation then TDC will NOT be in the vertical plane. You can ensure the engine is at TDC by making sure that both the mark on the c
ankshaft pulley (front of engine) is in line with the pointer on the casting and that the camshaft timing pip is lined up with the mark on the rocker cover.

Look in Haynes manual P31-32 for pictures and read section 9 to get a better idea

edited to remove confusing info.. It was late last night[:)]
 
Thanks David, I'll pass this information on. [:)]

BTW you seem quite handy on the technical side of things - are you a pro mechanic?

Ta [:)]
 
ORIGINAL: PaulHere


BTW you seem quite handy on the technical side of things - are you a pro mechanic?

Ta [:)]
Click to expand...

No, I'm not a pro mechanic..... just someone who has probably had more than his fair share of problems[:D]
 
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