Diesel vs. Petrol

fastesthamster

fastesthamster

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Looking at buying a 4X4 (Nissan hardbody). I hear that you should let a diesel engine idle for a few minutes before switching off the engine. Now, I work 7km from home, does that mean I would have to sit for 5 min after a short trip?
 
Get a bicycle. :p

Short trips aren't kind to cars, be they diesel or petrol. The issue is that any car's drivetrain takes amplified strain until everything reaches optimum temperature. So it's a cumulative problem, as your car will spend an inordinate percentage of its working life basically grinding itself apart... The advice to idle turbo-charged cars before shut-down relates to giving the turbo an opportunity to spin down (it operates at up to 200,000rpm) whilst still properly lubricated, so nothing more than 30s to a minute is needed. Even if you consciously drive the last 500m to your parking spot below boost you'll be fine, or at least as fine as with a non-turbo.
 
letting a diesel with turbo idle for a couple of minutes before shutting down is good practice to avoid the possible scenario of shutting off with the turbo at high RPM and it coasts down without oil pressure - I think the modern turbo diesels have addressed this and there's no longer a need for the idle time before shutting down.
 
Idling is fine, but slow driving is also fine. The aim is too cool the turbo which can run at up to 800 degrees, and allow it to run down from up to 200 000 rpm. These are extremes. I have a Ranger 2.5Td. Driving it at 60 km/h produces an EGT (exhaust gas temp) of 250 degrees and the turbo, although spinning, is not going very fast based on the observation that there is no noticeable boost below 2000rpm.

Driving around at normal speeds in suburbia, idling while parking, and switching off immediately (without blipping the throttle) will is a completely acceptible turbo shutdown.
Doing 140 down the freeway, howling into the 1-stop offramp, and killing the motor as you arrive at the pumps, is not.

I never idle my motor before shutting down, but I do drive the last few km at reasonable speeds. I've owned 3 Td's, done plenty mileage on them, never had any turbo issues.
 
Why is the title versus a petrol? :/
 
enigma243 said:
The issue isn't petrol vs diesel, it's turbo vs non-turbo... ;)
Click to expand...

Ah, okay. I was going via this:
http://sites.google.com/site/invest.../nissannavaravsnissanhardbodyvseverythingelse
Checking with a friend of mine who used to work for Nissan as to “why the petrol rather than the diesel”………… He tells me ………”most mere mortals don’t know how to treat a diesel with the correct love and care”………… making sure to not over rev the engine when near to the end of a journey and then sitting in the car in the parking lot for 5 minutes (listening to some half brained DJ rambling on about his pet hate for the day) to let the turbo cool down
Click to expand...

Just assumed it was diesel specific.
 
fastesthamster said:
Ah, okay. I was going via this:
http://sites.google.com/site/invest.../nissannavaravsnissanhardbodyvseverythingelse


Just assumed it was diesel specific.
Click to expand...

Most diesels are turbo-charged though as they are positively asthmatic without a turbo; petrol cars are still more likely than not to be naturally aspirated. With highly-strung, small-capacity forced induction petrols becoming more mainstream (think VW's new 1.4 TSI) expect petrol turbo-popping to become an equally popular hobby.
 
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