Not that I would ever endorse the labouring of an engine but is there some technical reason why it would clog injectors up?.
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Well its putting a *big* strain on the main bearings.............and transmission.
Over on the Fiat Forum some lads think its OK to keep hitting the rev limiter in *regular* driving and believe there will be no future consequences at all.
Your mates are *booming* along taking years off the life of the engine bearings and transmission.
No way am I ever going to risk a used car, the more I read about things like this the surer I am :)
( saddest thing of all is that some poor sap will come along and think they have a great buy with these cars in the future and that 100,000 miles is *nothing* for a modern diesel)
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Crikey... someone better tell commercial drivers then before all trucks and coaches suddenly break down with premature engine failure! They spend most of their day driving round between 1200 and 2,000 rpm!
Ditto taxi's...... their main bearings must be *really* knackered by the time they clock up 300,000 miles!
Oh, while we're at it, someone should take out a lawsuit against Audi for their sheer incompetence - their DSG auto 'box often changes up at 2,200 rpm settling at 1,400 in the next gear. If only Audi had access to some of the expertise on this forum, they wouldn't make such stupid mistakes...
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"Crikey... someone better tell commercial drivers then before all trucks and coaches suddenly break down with premature engine failure! They spend most of their day driving round between 1200 and 2,000 rpm!"
And some ship diesels are happy at 100 revs...... :)
Apples and pears.
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It depends on the diesel engine characteristics and gearing combination. Some diesel cars will pull happily from around 1000 - 1200 rpm whilst others need 1200+ rpm before they pull enough. Gear changes again depend on the torque curve but for most modern car diesel engines they have max torque around 1750 to 1900 rpm but will happily pull from lower than that.
A new diesel engine will be tight and they need a few thousand miles to loosen up and letting them judder at low revs is mechanically unsympathetic. When the revs are right the engine and car won't jugger, if is does that it's time to swiftly change to a lower change gear. As already pointed out a class professional lorry driver will change up gear whilst still running at low revs pre-2000 rpm. Mr average Motorcar driver still drives their diesel car like they drive a petrol engine when it's completely unnecessary to do so, no wonder some peoples diesel economy is little better than a petrol engined car, use the torque not the power.
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"Mr average Motorcar driver still drives their diesel car like they drive a petrol engine when it's completely unnecessary to do so, no wonder some peoples diesel economy is little better than a petrol engined car"
Absolutely, and by the looks of things, there's quite a few Mr average motorcar drivers on here!
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Pointless post.
Ship engines bear little in common with car engines.
Lorry engines on the other hand have a great deal in common with car engines.
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The ideal situation is to use change gear at the "appropriate" point for a particular throttle opening.
A.) So, trundling along, very light throttle, off boost, change up early, why not? Just clatter along at gently at 1000rpm or so.
B.) Moderate throttle, using the turbo, change up a bit later, anywhere around 2500rpm so you don't go off-boost in the next gear.
C.) Full throttle, use all the revs up to max power, although you will only go a tiny bit faster than B.)
...and all the incremental variations in between.
What doesn't make much sense is using full throttle at 1000rpm, or slowly going to 4000rpm on a light throttle, and most auto gearboxes know this.
Getting it wrong isn't going to make a big difference unless you drop below idle speed and the engine does that horrible judder like it's trying to jump out of your engine bay. That's because a 4-pot engine can produce some quite large out-of-balance forces at very low revs, and it really is trying to jump out of your engine bay.
dv.
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>>That's because a 4-pot engine can produce some quite large out-of-balance forces at very low revs
That's not quite true - out of balance forces are all proportional to engine speed squared. So, as the engine slows down, these forces are reduced - dramatically.
However, the engine is mounted on compliant rubber mountings such that the 6 rigid body vibrational modes (or natural frequencies) of the engine/gearbox are below the idling speed. Force an engine to run for any time below idling, and the engine will build up a large amplitude response - but this isn't because the forces are high, it's because the system is near resonance, where low forces can produce large motion.
This is one reason why some diesels have shut off valves, which make the engine spin down faster after you turn the key off, preventing these vibrations offending the driver, and the large amplitude response damaging engine to body pipework.
Number_Cruncher
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That may well be the case, but it still feels as if the engine is trying to leave via the nearest exit.
dv.
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Yes, dv, I agree - the engine moves a lot, but not because it is producing more force - it is because the restraint is weaker at that frequency.
Number_Cruncher
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Maybe the booming at low revs is due to a fault with the mountings? My 90 hp Audi and later 110hp Passat were quite happy at low revs, but I drove it in the manner dv described. Made sure it got more of a stretch on Mway and slip roads though. It was was quite untroubled either way. I drove window open in a high gear at moderate speeds on back lanes, as the burbling was quite pleasant. Takes all sorts I suppose......
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My Punto 1.3 multijet would "boom" if put into 5th and the change dropped the revs to 1500. Really changing into 5th has to be above 50mph to have around 2000 revs, for it to feel as smooth as higher in the rev range.
I think the old Perkins prima I had years ago in a Maestro could smoothly pull from low revs , but then it felt only one step up from a tractor engine :)
There`s a difference and although I have driven lots of diesels, the multijet seems to need a driving style that is between the traditional Diesel and Petrol styles.
No complaints though its just adapting after so many years of *old sluggers*
I wonder what is the best Diesel in current production for pulling low revs without the *boom*?
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When I turn the Mondeo off it's like someone's suddenly jammed a stout bar in the flywheel ring gear. CLUNK. Stop dead.
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I've also noticed that there's no real performance gain from accelerating to the red line - changing up at about 3500RPM drops the engine smack in the middle of the turbo range for the next gear at a reasonable number of revs. Above that it just makes a lot of noise.
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Crikey... someone better tell commercial drivers then before all trucks and coaches suddenly break down with premature engine failure! They spend most of their day driving round between 1200 and 2,000 rpm!
1200 is long way above tickover and labouring, 2000 is getting near the red line.... That's why the things have 16 or so gears, do you really think they'd bother with that many if it was OK to labour the thing????
Oh, while we're at it, someone should take out a lawsuit against Audi for their sheer incompetence - their DSG auto 'box often changes up at 2,200 rpm settling at 1,400 in the next gear. If only Audi had access to some of the expertise on this forum, they wouldn't make such stupid mistakes...
Not when it's doing the equivalent work of 1200 rpm up-hill flat-out in 5 th it doesn't....
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It seems there's some confusion. Although i talk about the car engine booming and complaining under massive stress. I'm well aware that is a function of many factors and not directly related to engine wear, but...
The question is: WHEN is the labouring starting to damage the engine?
I remember petrol ohc vauxhalls in the '80's used to go really smooth, tight and quiet when you loaded them up a lot. eg 25 mph in 4th, this was before the onset of labouring, but still considered bad for the engine all the same.
Personally: I'm pretty sure that if you're driving 1200 rpm in 5th uphill and the whole car is booming and the engine starting to jerk, that the forces on the bearings are overcomming the oil pressure. If someone has a sensible engineering reason why this is not the case, then please post. Sarcasm and drivel can better find another thread to litter....
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I think that someone should tell this chap that the reason coaches and trucks spend all day at 1200 rpm is that they red line at just over 2000 rpm hence they are nicely in the middle of their rev range at that speed.
How does this mean its good to shudder around around in a car at 1200 rpm?? Why would anyone compare a family car with a truck??!!
My 2.0l diesel redlines at 5000rpm....which is why i spend most of the time between 2000 and 3500rpm.
With regular blasts up to 4000rpm....refer to Honest Johns FAQ's.....its all in there.
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