Carrera GT and Turbo ignition 'pulse' sensor

[PaulHere]

I received a very helpful e-mail from member Julian Richards that may be of help if the pulse ignition sensor should fail on a 924 Turbo or 924 Carrera GT.
If anyone contacts the companies mentioned please let us all know if they were able to help.

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Hi Paul

As promised here is some information on the GT ignition sensor.

Its a reluctance type with no active element, I had to replace mine a few years ago, It's made from a soft Iron core with a coil of wire around it and a magnet at the end.
It works like this, when a gear tooth passes through the magnetic field created by the magnet a voltage is induced in the coil, this gives 200 pulses per revolution.
The soft iron insert at TDC induces a much larger pulse allowing the unit to discriminate between ordinary pulses and TDC as shown below.

Testing the sensor requires and OHM meter it should be 600 - 1600 ohms, if it's shorted or open circuit it's not possible to repair the coil.
There is a 3 pin plug, two pins are the coil the third is for the cable shield BOSCH LH Jetronic as used on 928, Volvo etc used a similar RPM sensor it might be possible to adapt one of those.
There are similar off the shelf sensors used with MO_TEC and other systems that might be usable if the resistance is in the right range.

Freisinger Motorsport (http://www.freisinger-motorsport.de) in Germany had lots of GT specific bits they might be a possible source.

Electromotive ( http://www.emi.cc/ ) make an ignition only system that could be used to replace the factory box
930 motorsport should also be able to help with replacement systems

Kind regards
Julian Richards (via e-mail)

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[924nutter]

I need the loan of a working sensor so that a company in US that I have unearthed and contatced can perform some non-destructive test on, with a view to manufacturing new sensors. They believe that they can supply, them based on the info I have already passed on but need to get real resistances and the shape. My sensor has definitely gone as it has only has a resistance of 5 ohms which is 595 under the low spec of 600 so some of the windings must be shorted. Don't know whether it is good news or bad but they also reckon $250 or £150 is a good ball park figure.

 

[tref]

I should have a spare good one... but it may take me a while to dig it out... Is there a difference betwen series one and series two Turbos? If so, which are we talking about? Mine is I believe series two, but if we can compare engine numbers, that would probably be better.

Regards,

Tref.

 

[924nutter]

I thought the series one had transistorised contact breaker ignition and no engine management under the heater matrix, so engine numbers is the way to go.

 

[924nutter]

PET doesn't give engine numbers for the change, it simply states item 16 pulse sender 81 on. If you have got one check it has a resistance of 600 to 1600 ohms.I would think that we should be able to mail this to the States using some of my regional funds as this is definitely for the benefit of members.

BTW, does £150 for a new sender sound reasonable?

 

[tref]

£150 for any part otherwise unobtainable which means your car will go rather than no chance of going sounds reasonable to me!

 

[924nutter]

My old ebay special that has been sitting for nigh on three years might have one, but my suspicion is that they fail, probably due to interstitial condensation, if not used regularly. I am not optimistic about it working. I am on holiday for two weeks. I am going to start the rebuild and damn the sensor. Worry about that when the time comes.