My Scudo's manual says that to start the engine, one should press the clutch down, and turn the key.
I assume that the main benefit of this is to reduce starting strain on the DMF.
If this is true, is it advisable to press the clutch down when stopping the engine?
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Starting with the clutch down is to let the engine spin more easily. I do it on all cars.
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Yes, but I am referring to strain on the DMF.
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>>I assume that the main benefit of this is to reduce starting strain on the DMF.
No, gearbox friction on startup would represent quite a benign load for the DMF compared with what it must bear in use on the road.
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"Gearbox friction" on startup? That's RR's take.
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OK I've looked it up anyway. There does seem to be advice that this (clutch use) is indeed helpful in preventing DMF failure.
Last edited by: FotheringtonTomas on Fri 3 Sep 10 at 11:48
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Good advice from a decent source? If so, I'm surprised.
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>> OK I've looked it up anyway. There does seem to be advice that this (clutch
>> use) is indeed helpful in preventing DMF failure.
No its not. The way you change gear, the use of sufficient revs, and smooth not wheelspin starts are the way to prevent DMF failure.
Last edited by: Zero on Fri 3 Sep 10 at 13:21
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It is certainly popularly held to be true that starting and stopping the engine with the clutch down reduces wear on the DMF.
Isn't the starting point so as to reduce wear on the starter motor, so as to limit the amount of work it has to do?
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>> >> OK I've looked it up anyway. There does seem to be advice that this
>> (clutch use) is indeed helpful in preventing DMF failure.
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>> No its not.
OK, why not.
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1/ There are insufficient engine starts, compared to gear changing and pulling away to make a significant difference.
2/ There is minimal DMF shock or torsion on starts compared to pulling away, changing gear or running lumpily at low revs.
NOt saying you shouldnt start with the clutch in, I always do it.
Its mostly a hangover from living with a BL product, where any little thing that may help a cold start was tried.
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>>OK, why not.
I gave the answer to this near the top of the thread.
For the DMF, turning the gearbox during starting, or stopping represents such an insignificant load compared with the loads the DMF transmits during sriving that pressing the clutch during starting and stopping makes no discernible difference.
Consider the nature of the load - the resistance offered by the input shaft is a small, viscous drag, at cranking speeds it's not a large load for the DMF.
Yes, gearbox friction or drag does make a difference to the starter, but, the starter never handles drive loads, and is sized only to turn the engine over just fast enough to start in worst case conditions.
The DMF, on the other hand is sized to trasmit peak engine torque, sudden application of load via poor clutch use, and the impulsive torque when each cylinder fires - i.e., this peak, impulsive torque is larger than the time averaged, or smoothed, torque figue which would be measured on [most] dynamometers.
As Zero has mentioned, poor clutch use and abuse is bad for DMFs, as also is any activity that puts a lot of heat into the clutch.
A friend of mine works in the clutch engineering/design section of a volume vehicle manufacturer, and he tells me that they got their sums wrong on one DMF application, and didn't properly assess how the heat conduction path changed when going from a solid flywheel design case to a DMF design case, and they had a large number of failures. The manufacturer involved won't be making that mistake again, but, it's interesting to note that the DMF supplier didn't warn them of this problem.
Last edited by: Number_Cruncher on Fri 3 Sep 10 at 15:44
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>> >>OK, why not.
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>> I gave the answer to this near the top of the thread.
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>> For the DMF, turning the gearbox during starting, or stopping represents such an
>> insignificant load
Again, I am not referring to this blindingly obvious fact!
www.jasperengines.com/newsletter/nljan2005.pdf
(Page 3, approximately in the middle)
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>>Again, I am not referring to this blindingly obvious fact!
You're not making yourself particularly clear, and that badly written article you point to isn't much help either. What, exactly, is your question then?
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Jesus wept. Go back to psot#1. If that does not help, please do not bother to reply.
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If you know all the answers, why are you bothering to ask the questions.
Last edited by: Zero on Fri 3 Sep 10 at 16:33
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Fully agree Z - I'm not wasting any more of my time.
He can't even be civil about it.
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FT's question is should he depress the clutch when *stopping* the engine.
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And he was told No,
But that wasnt good enough.
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yep silly season is still open apparently
i blame global moaning
now all sit down and shake hands
mines a pint
a trophy bitter that thinks its a quart........................ :-)
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It doesn't matter. I've looked up the answer, and it is true that it does help. Shrug.
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If you say so, why didnt you look it up earlier and save us the agro of being Sooooo wrong.
Tell us the reason WHY it helps the DMF?
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I wonder if the van even has a DMF? Not that I care.
if the manual says something and you don't do it and something breaks.... assume there will be a way for the manufacturer to wiggle out of a warranty claim.
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If this is true, is it advisable to press the clutch down when stopping the engine?
As it's a Fiat, I suggest not driving it is the solution.. Then you'll never experience DMF failure...:-)
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The clutch and the DMF. - Robin O'Reliant
