Mysterious engine problem

[FelixF]

My businesspartner owns a 512TR which has come up with a strange engine problem...

A while ago his car got confiscated temporarily because the car was a bit err... too loud (135dB), to get it back, the German TÜV made him change the exhaust to a road legal tubi style exhaust - it was then the problem started to appear.

When the car is driven hard, the ECU sometimes decides to switch cylinders 1-6 off completely (as indicated by the dash display). According to the manual this indicates that the exhaust temperature (the car does run probes as standard) on that cylinder bank is too high. Nothing apart from the exhaust has been changed at all.

Up to date, Ferrari has not offered any explanation.

Has anyone ever experienced / heard of a similar problem and / or has any idea what it could be (apart from "its' the exhaust") ?

Thanks, Felix.


>>> Edited by FelixF on Friday 31st January 16:45

[manu]

It physically cannot be the silencer as this is mounted AFTER the exhaust thermocouple. Any make of aftermaket sport exhaust system lowers temperatures becuase they reduce backpressure by being less baffled and restrictive.....
Off the top of my head - the faulty Cat is either retaining too much heat triggering the light (could be "blocked"... or it has already damaged thermoucouple/ECU for that bank of the engine which is causing the ECU to shut down 1-6.

Time for new cats or test pipes or new ECU or thermoucouple (called "Cat control unit") - classic 348 problem solved by binning cats and fitting test pipes.

>> Edited by manu on Friday 31st January 17:18

[domster]

I would also get him to check exhaust valve clearance/cam belt/chain timing.

If the timing was slightly out, you could get bizarre exhaust temps that would be enough to cause severe engine running problems.

Why this would happen after a new exhaust has been fitted I'm not sure - may be coincidental. Certainly the most obvious route (as manu was getting at)m is blocked cats causing too much back pressure, or maybe a cat warm up valve not opening if there is one on these systems.

[FelixF]

I would have hoped that the dealer had checked if all the sensors/ecu's were working correctly when the car was serviced (dealer said he'd found nothing wrong). Maybe the cats are a possibility.


Thanks guys.


Felix.

[domster]

The ECU will not throw up an error code if the timing is physically out, as far as I know, say if the timing chain jumped a tooth. That said, the car should feel more sluggish than normal under normal driving conditions, and you should be able to spot that.

Cats seem a real possibility, especially as I've heard that they can 'go off'.

Cheers
Domster

[360N-GT]

As Manu said, most likely unrelated sensor/cat control unit problem. Can happen at any time.

To test for thermocouple problem, simply swap control unit (most likely) from 1-6 to 7-12, and vice versa. If problem follows to 7-12 it's the unit, if it stays 1-6 it's the thermocouple or cat.

On our 360 challenge cars we race in Australia, we simply bridge the thermocouple connection on the unit, and leave the thermocouples in the cats, which stay under the bench in the workshop at all times!

.....not sure of the accuracy of domster's advice, sorry mate. Clearances/timing just won't make THAT much difference to combustion temperatures.

But a cheap way of having a quick check, is to look at the spark plug colour from each bank.

Nice brisk run in the car, not balls out. Then plugs should be chocolate brown, not too grey or white.

[FelixF]

Thank you - very much appreciated.

We will try your suggestions as soon as the weather permits running. I'll keep you posted.

Thanks again.

[domster]

.....not sure of the accuracy of domster's advice, sorry mate. Clearances/timing just won't make THAT much difference to combustion temperatures.

LOL, you are probably right. I am a bit of a dunce with these things, but learnt far more than I should about engine problems with a Lotus Carlton.

I only mention exhaust valve timing because this caused serious pinking and a miss on one of my cars once, presumably through increase in cylinder head temp (and therefore compression).

Mind you, it wasn't on a Ferrari!

Cheers
Domster