I haven't posted here for a while. The short version is that the car has spent more time in the workshop than on the road, and we have finally tracked down the problem.

JM Autos' conversion (carried out for the PO) turned out to have rather a fundamental error. While the 993 engine is from a 5-speed manual car, the ECU and wiring loom are from a Tiptronic!

Amazingly, the car runs really well in most respects, but has one key problem. After sustained moderate to high revs (eg. running on a highway for a while), the engine dies when you come off the throttle.

The ECU we need is BOSCH part number 0.261.203.376. The engine-to-ECU loom needs to be from the exact same car.

I'm not following the board at the moment (too depressing with my car off the road while this is sorted), but will be following this thread. If anyone can check with their favourite breakers, that would be enormously appreciated!

Thanks,

Ben

 

The only difference between tip and manual in the 55 pin DME which are used on the euro 993 vrams is in the backup light switch wiring. A manual harness will have a wire at the trans fot this the tip is triggrered from the shifter.

The engine ding at idle is another issue entirely. The conversion flywheel is considerable lighter(~30#) than on a stock 993.

Supposedly a vram has std. electronics to compensate. On mine I have a custom chip so can't say for sure. If not a chip w/ idle compensation can be installed easily enough.

 

Your custom chip, is that in place of the standard ECU, or something additional?

Any sources for a chip with idle compensation?

Ben

 

Steve Weiner

 

On the 993 engine, the idle compensator can itself be adjusted to help prevent the engine from dying. If you do a search on the 993 forum, you'll find several posts where the process is described in detail. In fact, recently John Dunkle described adjusting the 993 idle compensator, I believe on the 964 forum.

 

Just a note here,.....

The OBD-I non-varioram 3.6 ISV can be modified successfully to reduce stalling however the much-more-complex engine management of the OBD-II varioram 3.6 will "adapt" around any alterations to the ISV so be forewarned.

Varioram engines normally handle light weight flywheels without an issue as long as the ISV is clean and not excessively worn.

 

Thanks for the replies. It seems that I didn't quite have the full story - the engine is a varioram one, but the ECU is from a non-varioram car, so that is the core problem.

The car also refuses to start when hot (starts fine from cold). That was thought to be because the original starter couldn't cope with the higher compression of the 993 engine, but the same appears to be true with a much beefier starter, so this may again be engine-management related.

I've asked my Porsche specialist, Jon Mitchell, to pop in here, as he will be able to discuss it more intelligently than I can.

Any advice anyone can offer on sorting it out would be greatly appreciated. So far I've chucked a tonne of money at the car (rust removal, respray, starter, alternator, rewire, etc, etc) and barely been able to drive it. :-(

Ben

 

Just chiming in...

Ben's car is currently in my workshop here in Bournemouth on the south coast of the UK.

The problem isnt that his ecu or engine is a tiptronic, the problem is that it has the wrong ecu for his engine... His engine is a 993 Varioram, the ecu and loom is a 993 PRE Varioram.

If he had the correct ECU (varioram) then the ecu would "probably" in our experience be able to compensate for the fact that it has a light flywheel. (variorams normally are quite happy with a lighter flywheel, but can benefit from a chip in some cases).

We currently have two 911SC's on our books, both with 993 engine conversions carried out by JM-(YEE-HAR! Ride em cowboy!)Auto's, and both have Varioram engines and pre varioram ECU's, both are suffering from similar problems!

To compound Bens problems, his current ECU is faulty, but there isnt much point in fixing the ECU, when its not the right one for the car (or the harness) and the faults could have been caused by being attatched to the wrong engine in the first place.

Our other customer has consulted with RennSport, who are also in agreement that with the correct ECU, the symptoms seen in both cars should go away (partly due to the ECU having better coding to deal with over run and partly because the ECU they both currently have is mapped for a different engine!)

The ECU both cars need, is Bosch part number 0.261.203.376 and ideally either a complete engine harness to match or a partial harness (the bit with the ECU connector) as this ECU is an 88pin item, where as the current pre varioram ecu's in both cars are 55pin items.

 

As a side note, hot starting cured, does not seem to be a problem any more.. Standard 911SC starter could not cope, that had over stressed the battery (trying to turn over the engine and being drained flat) and alternator (trying to recover the battery from flat all the time)... Now fitted with gear reduction starter, new alternator and new battery.

 

One other note JMAuto's is not me! (Jon Mitchell Independent Porsche Specialists)

JM-(Yeehar)-Auto's is a company based near London, previously owned by a chap called James just before he moved to Australia.

If you have had a 911SC to 993 engine conversion, or anything done there, get it checked out by an independent specialist or an OPC.. In the last couple of years I have had to sort out more of their mistakes than anything else.

As the technical advisor to the independent Porsche enthusiasts club (Tipec) here in the UK, I have also had to advise MANY club members experiencing problems following James's handywork. Beware!

 

There is a fellow named Harold Julicher?(I'm fairly sure that I have mispelled it) that goes by the name Speedster94 on the Pelican board. I don't have his contact info but he is in the salvage business in Germany and may be able to provide the correct harness and DME.

I would go to Pelican and do a search on the user name Speedster94

 

Thanks for that, Bill - I'll drop him a line.

Ben

 

Fingers crossed, this looks like a solution. I've arranged with him to buy an ECU and loom set. Watch this space!

Ben

 

See this thread: https://rennlist.com/forums/911-forum/166260-caution-re-harald-j-licher-automann-freenet-de.html

Ben

 

"The ECU both cars need, is Bosch part number 0.261.203.376 and ideally either a complete engine harness to match or a partial harness (the bit with the ECU connector) as this ECU is an 88pin item, where as the current pre varioram ecu's in both cars are 55pin items."

The 88 pin DME has two versions (neither of which has an EPROM - removeable).
The earlier has a mask ROM and the later has a flash memory (EEPROM). Also, as
has been mentioned, lighter flywheels cause "undershoot" on de-accel at idle,
which can result in engine stalling. This problem can be reduced by an ICV mod,
but it generally requires a DME firmware change.

The other key issue is that the 88 pin DME requires an immobilizer interface,
i.e. It must receive a "start" command from the immobilizer to allow cranking
and DME functioning. Without this command, the engine will not run.
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