Questions about Citroen Diesel engines?
How to get current specs (in English) for new car engine?
How to treat a turbo?
What is intercooling?
What is the difference between semi synthetic and synthetic oil?
Sorry if these are familiar questions but would appreciate help
regards
Vercin
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It is indeed. We just need to build up the client base for you to get some feedback.
David W [Moderator]
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mailto:david_moderator@honestjohn.co.uk
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For semi synthetic & synthetic oil use the search engine.
You will find an absolute mound of information.
Mark.
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Hello there Vercin,
The big issue with the turbo is that it uses the hot exhaust gases to spin a turbine like impeller and pump air into the engine. More air and hence more oxygen in the engine means you can inject more fuel and hence get more power. This impeller runs at very high speeds and high temperatures, ie it glows cherry red if you are giving it some welly. If you just turn off the engine when the turbo is hot and spinning fast, the oil supply to the critical fully floating bearings is cut off, the heat soaks, carbonises the oil, and the bearings can pick up and premature turbo/seal failure results.
The recommendation is that for long turbo life, say you pull into a motorway service after a hot hard drive, idle the engine for two minutes. This is called simmering, allows the turbo impeller to spool down, cool somewhat whilst still supplying a good flow of oil to lubricate and cool the bearings.
If however your last few miles before stopping have been fairly slow, then it might need only a short while of idling if at all. To decide which category you fall into at the time just needs a bit of judgement at the time.
At start up, personally I just let the engine idle a short while, only a few seconds before pulling away, on the basis of getting oil round the system.
What is interccoling.
This is also called charge cooling. As the intake air passes over the hot turbo, whilst it is compressed it also heats up, a) due to the compression, and b) as the turbo itself is hot. Hot air is less dense than cool air. So the air is passed through and air-air heat exchanger, where ambient air is passed in order to coold the compressed charge air. This increases its density and thus more air and therefore more oxygen is packed in, and so even more fule can be injected, hence yet more power.
Regards,
FiF
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Vercin, FiF has nicely outlined the general principles to answer your questions. Perhaps I can add that if your vehicle is a diesel (Citroen ?) diesel turbo's do not, generally, get as hot as those fitted to petrol engines but, the practice of "running on" any turbo'd engine, for a short while, especially after a long motorway run, is good sound practice. Also, you might find that your turbo is water cooled (some are not), and this helps to overcome the "oil carbonising". Also, after start up,(as FiF mentions) a few moments, running at light load, before the turbo starts to "boost", does ensure that adequate lubrication is passing through the turbo bearings before they start to work under load.
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Hi John,
thanks for the additional info and yes it is a Citroen diesel.
I'm going back to the info that came with the thing to check the water cooling bit.
cheers
Vercin
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Hi FiF,
Many thanks for this clear explanation which goes a long way to help the wife and I understand this new fangled technology.
Now on to the CD changer!
I'm very grateful
regards
Vercin
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Are any diesel engine turbos water cooled? I wouldn't have thought the [Diesel]turbo would run hot enough to warrant this feature?
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DD,
Renault 19 for example. If you hear a whirring on one of these after the engine is turned off it is the coolant pump on a timer relay that keeps the thing going for up to 15mins after switch-off.
Had a pig of a problem with it where the battery kept going flat because the pump never turned off.
David W [Moderator]
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mailto:david_moderator@honestjohn.co.uk
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Dave W
An unexpected bonus solution as I've just sold a Renault 19 which was beyond economic repair and I could not work out why it kept flattening the battery when not in use for relatively short time
At last a plausible explanation
cheers
Vercin
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Yes, the Toyota Masterace/Townace range ( I don't know about the Hiace) with the 2C-T 2 Lt engine, have water cooled turbo's. Some of the Camry models have the same engine and I assume this beneficial feature is also fitted to them.
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Ha! Well you learn something new every day don't you?
I really don't see this as a benefit on a Turbo-Diesel.
Petrol Turbo, yes..
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David, sorry must show respect, Dr Dave,
Agree that diesel turbos run cooler, but is there any published info on how much cooler?
I presume this is because the diesel is unthrottled and therefore the flow of cold air is always higher, or have I misunderstood?
Cheers,
PS as long as you don`t get as sarcastic as that Dr Diesel chap
;-)
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"as long as you don`t get as sarcastic as that Dr Diesel chap"
Fear not FiF, I won't!
I think the turbocharger running temperature in an oil-burner is lower because the combustion temperature is lower in a Diesel engine compared to that of a Petrol engine.
I've never seen a Diesel exhaust manifold glowing red after a run!
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"the combustion temperature is lower in a Diesel engine compared to that of a Petrol engine."
Thanks, never knew that it was that different.
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My brother-in law changed the carburettor on a Reliant 3 wheeler and put on one with smaller jets/weaker mixture.
He found the engine was running hot, stopped and found the exhaust manifold glowing nicely.
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