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        General >> Problems >> Diesel Smoke at Certain Revs
        
(Message started by: hybrid on Mar 20^th, 2005, 4:21pm)

Title: Diesel Smoke at Certain Revs
Post by hybrid on Mar 20^th, 2005, 4:21pm

Hey Peeps.

I have a niggling problem I've had with the 2.5TD for about 6 months now. When accelorating, the engine seems to accellorate fine until around 1500 revs, then the power drops and smoke, or unburnt fuel, im not sure, comes out the exhaust. Once the turbo kicks in above 2100 revs the acceloration is fine and theres no smoke. Is there a valve or something somewhere that detects the amount of fuel being injected that may be blocked? I'm pretty sure the turbos ok, due to the fact i forgot to reconect a while back and accelorated like the QE2.

Thanks for any help you can give
HybRiD

Title: Re: Diesel Smoke at Certain Revs
Post by richardcoles on Mar 29^th, 2005, 1:02am

Hi HybRiD,

Have considered your problem before passing on my opinion, however a question first:
When did you your last MOT, what was the smoke test reading?
I keep the print out every year and it serves as a check on how the injectors are performing. This year my reading was 0.23M-1 (which is practically no smoke, the old Granada used to give readings of 1.2M-1 to 1.8M-1). This will indicate if you have a fuel injector problem and remember it only takes one injector to be “hose piping” (not atomising) to produce the smoke. However if it was a bad injector it would be smoking over the full range.
Now for the theoretical side that may help put things in perspective. As you rightly say your turbo does not take effect till higher revs and load. Turbo charger boost output is not instantaneous it takes time and the reason is you can not accelerate a turbine rotor from 10,000 revs to say 40,000 plus, in a fraction of a second, its called “turbo lag”. Do a little test at night, accelerate and look in the mirror and in the headlights of the car following you will see the smoke produced by the “turbo lag”. The dark smoke is produced by the in balance of the fuel air ratio, which is not in the correct proportion i.e. not enough air for the fuel being burnt, when the turbo catches up the smoke disappears.
A few facts and figure to put the output of turbochargers in perspective; a 15,000 bhp ships engine turbocharger will produce, if you could put a dynamometer on it about 2,500 to 3,000 bhp (turning at 15,000 to 20,000 revs) so you can see these turbochargers or centrifugal compressors are quite high output machines and not to be underestimated. Your car turbocharger follows the same principles.
You can improve the reaction time of your turbocharger by ensuring the air filter is clean and by assessing its performance when the oil is hot and by reducing the oil drag or by using friction-reducing additives. Bear in mind that all engine-lubricating oils are not the same and some have special additives, which lower the drag effect of the oil. One of these oils is MILLERS and I have used this diesel lubricating oil for years and swear by it. If your engine has upwards of 100,000 miles on the clock then you should really consider flushing the engine out with flushing oil, however use it carefully. Do not drive the car with it in and do not rev the engine up too much.
Hope the info was of some help, however by the sound of it you do not have a severe problem.
Best regards
Richard

Title: Re: Diesel Smoke at Certain Revs
Post by jackman on May 27^th, 2005, 3:53pm

Hi Hybrid

I think you might have the same problem i have with mine took it to lucas they said it was the throttle prteniometer which is on top of the diesel fuel pump.

Been to F M C for a price its about £320 pick your self up lad!!!!! hope this helps

Jackman