Conference terri::cars_uk

    
    YES.
    
    Mark
    
    PS I'm beginning to worry about you Art. First you want an MR2 and now
    this! :^)

Labouring an engine in a high gear at low revs puts just as much, if not more,
strain upon it as screaming along at max revs in a low gear.

Dick

what exactly does it do to the engine?

I really want this info so that I can explain the benefits of not labouring
the engine to someone who causes the engine to labour because they believe 
1000rpm is far more fuel efficient & kinder to the engine than 2.5-4Krpm is

thanks...

...art

1000 rpm = less oil pressure, particularly when warm = more wear.

Under power, you actually need MORE throttle to move along at 1000 rpm,
therefore more fuel consumed than at 1500 rpm or so (normal 30 mph revs?)

1000 rpm = less than efficient alternator (usually designed to run at 1250
or more), therefore run down battery faster.  This could be dubious! :-)

Why shake your engine to bits anyway!!!  

Brian

>> Under power, you actually need MORE throttle to move along at 1000 rpm,
>> therefore more fuel consumed than at 1500 rpm or so (normal 30 mph revs?)

  Are you sure ??? Surely, if you use MORE throttle, the engine revs will
  rise ...

 I would suspect that it all depends how the engine is set up. It must be
 possible to set up an engine to be most efficient at any point in the
 effective rev-range. 

 I head once about a study being done with a bus engine that ran at
 constant revs. The 'throttle' pedal caused the gears to change to make 
 the thing go faster or slower. The economy was supposed to be much improved,
 but the drivers found it difficult to get used to ...

Mark

    
    I wouldn't worry, Mark.  MR2 <> Low revs....
    
    Nigel

Most volume produced cars around today are designed so that they are at their
most fuel efficient at somewhere between 2.5-4.5k rpm. The clue here is the revs
at which peak torque is delivered.

If you apply a constant load to the engine, but vary the engine revolutions, as
the efficiency falls off at low revs, you will have to put more energy into the
engine, in order to get the same amount of work out. This means that you waste 
fuel. You also load up the moving parts of the engine, which induces wear. This
is compounded by the low oil pressure of the low revving engine.

Dick

    
    Yep,
    
    It did strike me as an odd combination. :^)
    
    Obviously for the ultimate economy low(ish) revs are preferable, but
    there is a line. It seems common sense that an engine which is chugging
    along can't be running healthily, but you just can't tell some people.
    
    I'm not sure of any ACTUAL reason why labouring an engine is bad for
    it, but it might be worth pointing out to this person that the engine
    is having to do more work (and therefore needs more power/revs) to
    move a car than it needs just to turn the engine over while coasting.
    
    Mark

>>	Wear is caused by force...
>>forces in the engine increase when you try to extract power at low RPM.
>>At high RPM the forces are lower for the same power.
>>at high RPM more of the forces are in the gear box which is built to
>>take it.

   This is probably the case, but why ???

   Is it anything to do with inertia ??? The higher the revs, the greater
   the inertia, so the engine has a tendancy to keep spinning ??? 

   If it is, then perhaps the bore/stroke ratio is important.

   Also, why don't diesels seem to mind running at very low revs ???

thanks so far...

what causes the engine(?) to shudder like it does at low RPMs?


ta..


...art

>what causes the engine(?) to shudder like it does at low RPMs?


big ends shaking themselves to bits, maybe...

;-)

    
    The engine could be shuddering if the mountings have been knackered.
    The mountings should endure the 'low rev & straining on the engine'
    but once they're worn out...
    

    Shuttering in my daily use BX TGI does not occur.
    This is because the injection type of fuel distribution.
    
    I guess carburettor cars suffer much more of this.
    
    Shuttering is caused I think by overloading the engine, in comparison
    to power produced at this low rev. Engine tends to shut down....
    
    Hans

    Shurely shuddering is because the revs are below the normal idle speed
    of the car and thus the engine is
    a	being starved of fuel
    b	reving so low that the individual strokes are identifyable.
    
    Diesels don't necessarilly run at lower speeds, it's just their torque
    comes on-stream at lower revs than a petrol engine(typical petrol, peak
    torque @4k-5k, typical diesel peak torque @2k-3k)
    
    Richard

    I would certainly think that revving an engine so slowly that it is
    'shuddering' (makes me shudder to think of it) is bad for economy, if
    not for engine longevity.
    
    In agreement with .16, point b - identifying each stroke.
    Not sure about point a - being starved of fuel.
    
    I think that an engine would shudder due to the combustion process
    not going on in the manner to which it was designed.
    If an engine is turning over slowly, fuel is not being drawn in at
    a high enough velocity, this would mean it will not mix so readily
    with the air, causing poor combustion, hence 'rough' running.
    
    When more throttle is used, with the engine under load, this situation
    will not improve readily, as ignition timing will (usually) be changed
    and more fuel injected (or sucked in), but amount of air will be the
    same - until revs rise.  If the engine isn't losing the battle too
    badly, it will recover - but if the unwitting driver has let the revs
    drop [much] too far, it will not accelerate at all.
    
    
    Personally speaking, I don't let the engine shudder - but I am guilty
    of making it scream on occasions...
    
    John Rutter

    Surely the reason for the juddering is due to the engine coming close
    to stall speed ? ( and don't call me shirley !)
    
    
    Shaun

	Maybe this is drifting off the point, but that's never stopped me
	in the past...

	My engine is carburetted, that means that the throttle opens a 
	valve to let more petrol into the carb.  However, an engine sucks
	petrol in because of the differences in  pressure.  So, even if I
	open the throttle wider than I need, the engine will only take what
	it needs.  [aside: is this true?]  So, running an engine so slowly
	that it judders and nearly stalls doesn't neccessarily mean that
	petrol usage is bad, just not the most efficient that a given engine
	can manage.

	Now, what happens if the engine is injected.  Presumably the injection
	is controlled via sensors, but of what?  Again, it shouldn't be 
	possible to overfeed the engine.

	Dave

    >>the throttle opens a valve to let more petrol into the carb
    
    Wrong!  The throttle opens a valve letting more air into the carb.  The
    petrol is sucked into the air flow by the pressure differential at the
    mouth of the jet (same principle that keeps aeroplanes up).  However,
    most modern carbs have an accelerator pump that "injects" petrol into
    the air stream as you depress the throttle, to compensate for the
    sudden drop in vacuum, hence speed of air flow.  The air flow then
    speeds up again as the engine revs rise...
    
    Most modern carbs have a "by-pass idle" circuit, which is a subsidiary
    jet supplying petrol when the throttle is "shut" and the engine is
    idling.  The supply of air / petrol thorugh this path is just enough to
    keep the engine idling, and isn't enough to keep the engine at low revs
    under load.  This may explain the lumpy running at low revs.
    
    More likely though is that the engine just isn't going fast enough to
    run smoothly: try riding a bicycle in a straight line very slowly.  You
    tend to wobble a bit.  As you go faster, you can keep in a straight
    line.  As the engine goes faster, the momentum in the flywheel keeps
    the engine running smoothly, ironing out the lumpiness in the
    individual power strokes...
    
    Scott

	Aha, enlightenment is coming (slowly).  However, I don't know if
	my carb has a by-pass idle circuit.  To vary the idle speed, I 
	adjust a little grub screw which stops the lever going fully home
	(or to zero, or whatever).  I guess that this must leave the
	engine with an appropriate amount of air (to suck).  As for 
	squirting, you're quite right, mine does.

	Oh, and I believe that the air flow trick that sucks the air/petrol
	mix into the engine is called the venturi effect?

	Dave

.19 seems to be correct.

I've noticed that you can coast right down to idle without any lumpiness,
but if you try to accelarate, then the engine does shudder.

As current thinking says that you use the brakes to slow down, then start
from the right gear, then this seems right.

Mark.

    > "coast right down to idle without any lumpiness"

    I've always been an advocate of the police school of thought where you
    use your brakes to slow down rather than braking and changing down
    through all the gears as is the case in the driving test.

    As they say, brake pads are cheaper to replace than gearboxes.

    Do you agree with this ? and would it not be more economical to "coast"
    in neutral when braking (I know you're not supposed to).

    - Roy

    On a similar subject, how about starting off in the morning.
    
    I'm sure i've heard/read/imagined that you should start up and drive
    off.  While the engine is cold you shouldn't do excessive revs.  This
    sounds right, but is it ?
    
    Some people i know insist on turning their engine on and letting it
    idle for 5-10 minutes ( have a cup of coffee) before jumping in and
    driving off.  Is this better for the car ?
    
    
    Nigel
    
    As an aside a few months ago i saw a sign in a Swiss Garage which said
    that modern cars didn't need idling before setting off and that it was
    also bad for the environment.

	Hmmm.  What I usually do, is to start the engine and then buckle up
	and get comfortable.  Thus, when I pull off the drive, the engine has
	been running for a couple of minutes.  Then, once I'm going, I keep
	the engine to less than half its possible revs until it has warmed
	up.  I would certainly never start the car and move off immediately.

	The first few minutes of an engine running is the most 
	dangerous 'cos the oil and engine parts are still cool so the most
	wear happens.  With more modern (synthetic) oils, this is less
	dangerous.

	Presumably, the Swiss say that idling a car until it is warm is
	environmently unfriendly because the car will take longer to warm
	up, and, because it is running on the choke, will chuck out more
	gung into the atmostphere.  

	Dave

You shouldn't let a car idle to warm up.  It takes *ages* to warm up that way,
so spends more time running cold, hence more damage.  I've always been told to
start up and drive off straight away.  Don't know about driving the first few
miles at low revs though.  I would have thought higher revs would give you
better oil pressure sooner...

Scott

    
    Isn't the argument that the oil is thicker at cold temperatures and may
    not be lubricating all the moving parts properly. If this is true (not
    that it probably is now with super-thin multigrades) then there may not
    be enough lubrication to suitably withstand high-revs.
    
    Mark

    
    My regime is to start the engine, check the guages and watch the oil
    pressure rise to its normal level. On a cold morning, the car will
    idle at around 2K rpm (maybe a tad high). After the oil pressure has
    stabilised, I'll raise the revs to perhaps 2500 or 3000 rpm for a
    few seconds - just to clear any misfire etc.
    
    Then I drive off, trying to keep the revs to below 3000 rpm (difficult
    as I drive out of the village and onto a dual carriageway) or 4000 rpm
    at most. Its hard to judge when the engine is warmed through (I use
    the water temperature as a first guide, but water warms a lot quicker
    than oil), but I'll try to use minimal throttle and revs for the first
    few (say five) miles at least.
         
    Bill.

    
    Any owner of Alfa's, Ferrari's, Maserati's etc will tell you that the
    Owners Manual INSISTS you warm the engine up for a few minutes - even
    in the summer.
    
    Few do, hence the head damage on many older Alfa's. Suspect not warming
    may well be the problem with the horrendous head difficulties with
    '70's BMW's -- & even Hillman Imps.
    
    Needless to say, not many Italians follow the book, but they have been
    told. Interesting that most Italian motorcars have (had?) a hand
    throttle that was meant for waming, but was also splendid when you were
    desperately trying to balance your Webers ...

    the owners manual for the vw golf (1.3) that i used to have stated
    that you should drive away as soon as possible; and NOT to leave the
    engine idling to warm up.
    the manual for the renault strongly recommends letting the engine 
    idle for a minute or so before moving of
    
    ...art 

    
      I recall from somewhere that you should never let an engine idle
    (whether warm or cold) for more than 1 minute (I believe it was
    an ~Austin Rover~ manual for the MG Metro) ?
                                                 
    
    Mark.
    

    
    Can mass produced engines really be that different that they require
    minutes of warming up (Alfa etc), no warming up (VW), or 
    somewhere in the middle ?
    
    Coming back to engine longetivity, what is the possible damage from
    getting it wrong, and will it be better/worse than running the engine
    at low rev's (as a comparison) ?
    
    Nigel_whose_cars_'ticks_over'_at_upto_2400_on_coldish_days.
    

    It is a fact that revving a cold engine will be bad for it !
    
    As for starting engines/waiting/driving off, I wouldn't know
    what is best - or for what engines.
    
    Driving 'gently' is the obvious way to warm it up.
    
    Oil pressure will actually be highest just after start-up (as long
    as it has actually circulated through the engine) as cold oil will
    be 'thicker' (even modern synthetics).
    
    I used to make a point of not running high revs until the water guage
    reached its 'normal' position - then I got a car with both water and
    oil temperature guages.  I was surprised to find that the oil temp.
    did not even start to rise until the water was at 'normal' position.
    
    I now wait until the oil temperature at least starts to rise before
    giving the engine 'some stick' - this may take quite a few miles on a
    cold morning (I don't like to wait, but that's the way it goes).
    
    John Rutter (change oil regularly, but synthetic, don't mix types)
    
    P.S.
    
    Running a turbo engine also requires that you let the engine cool down
    before switching off (following high-boost travelling).
    
    Seems like I should spend more time waiting for the engine to warm-up
    and cool down than I can save by driving faster !!!
    
    Answer to that - drive faster still, or sod the engine ?

	My understanding is that excessive revs while the engine is cold
	has two possible effect. Firstly cold oil on cold bearings does not
	lubricate as well as when both are warm. Secondly when the oil is
	cold its viscosity is higher, hence its pressure will be higher - even
	the relief valve will not handle this fully - so there is a risk of
	oil seal damage.

	There is also an effect, that I think is called 'wiping', that
	can occur in plain bush bearings (i.e. big ends and crankshaft main
	bearings) where the combination of high pressure and high loading
	(that can occur when red lining a cold engine) can cause the bearing
	shell material to be actually wiped off by the oil.

	- John.

Here's the way I start off in the morning:

(1)	Leap in & shut door.
(2)	Turn key in ignition.  Engine coughs and stalls.
(3)	Remember choke & pull out. (Prev car had auto choke)
(4)	Wheelspin out of parking place at max revs.
(5)	Attempt to simultaneously put seatbelt and radio on before I get to 
	corner of road where I need hands to steer.

Is this recommended?

Jon

    well you're along the right lines there, however you are going wrong
    at one point; you must remember to slam in the Bananarama tape and turn
    the volume up full whack before you try to wheelspin away...
    
    ...art			:-)

    
    You need hands to steer? Wot a wimp ;-)
    
    Bill.

    Re .37/.38
    
    And I was partly responsible for these guys being employed at Digital !
    
    Rich
    

    
    A major contribution to road safety, Rich. (Well, it keeps them off
    the streets...)
    
    Bill.

  <<< Note 1245.42 by VANTEN::MITCHELLD "Spin? Who Me? I'm only the driver" >>>
                                -< Wrong tape >-

>Half way thru "The Chain" by Fleetwood Mac from the Rumours LP
>Its a bit difficult to synchronise with traffic lights. Perhaps its due
>to having that silly amber light in the sequence


wrong part fitted: you need "It'll end in tears" by "This mortal coil"
you can synchronise with _anything_ with this tape

    Re .-1 (The Chain)
    
    Traffic lights, huh ?
    
    Follow the lead of 'touring car' racers, or better still the Trucks,
    they have a rolling start - Red light = Continue for another lap ?
    
    Other option, play "The Race" - by Yello, then shift through the box,
    hoping not to jump the lights - or find any corners !

I suppose there's so much torque-steer you don't need a steering wheel ;-)

Scott

Ok then.

I have just purchased a Long wheel base Landrover with a 3.5 Lt V8 under the 
bonnet.

What tracks would the panel recomend to play whilst driving this beast.

				~~~~~~~~~~~~~~~

And on a more serious note, how would you look after a V8.

Simon.

LOUD ones !!

    Re .47
    
    You mean you have a STEREO in your Landy !!!
    
    What is the world coming to ?
    
    
    As for looking after the V8, earlier reply about oil etc. makes sense.
    
    Of more importance is keeping water out of it, that would give
    it a terminal illness for sure.
    
    I do expect you will be taking it off-road, won't you ?
    
    
    John Rutter (who until last week was the owner of a rusty CJ7 JEEP,
                 was a shame to let it go - I must replace it sometime soon)

re..

...	    You mean you have a STEREO in your Landy !!!

/	Not yet, but soon. I do have an amateur radio already installed.

...	    What is the world coming to ?


/	Fun fun fun	:-)		(see my title)

...	    I do expect you will be taking it off-road, won't you ?

/	But of course, what do you take me for?   ;-)

...	    John Rutter (who until last week was the owner of a rusty CJ7 JEEP,
                 was a shame to let it go - I must replace it sometime soon)

/	You could always buy a Landrover	;-)

    Re .-1 'could always buy a Land Rover'
    
    Running a Land Rover would appear to conform too much !
    Good they may be, but they seem to be a few 'too many' around.
    
    I also thought it was difficult getting V8 versions, unless you
    buy a recent version.  Of course, Range Rovers are available with
    V8 engines and COIL SPRINGs, but then don't you also get thick,
    luxurious carpet and a free pair of green wellies with those ?
    
    Anyway, I though off-roader types didn't take much notice of
    how to 'take care of' engines, just fill it up, bog it down,
    winch it out and keep on going...
    
    As this appears to be going on about the vehicle type, rather than
    the topic title 'engine longevity', perhaps you could point me in
    the direction of an 'All-Wheel-Drive' topic or conference ???
    
    J.R.

If you do roll your Landy, don't undo your harness if you remain upside down.


Simon   ;-)

    ref .52
    
    Why not try a Lada Niva instead ?

    
    re.52 - there may be a lot of Landys about - but not that many ex MOD 
    lightweights - (especially not bright green! :-)  ) 

Don't you mean a 110 ?



Simon

    
    Off road performance is to some extent limited by torque to weight
    ratios.
    
    The Lada Niva offers 17 kg/lb.ft
    The Suzuki SJ413 softtop is 18 kg/lb.ft
    The Isuzu Trooper II short wheel base diesel offers 15 kg/lb.ft
    The Land Rover Discovery TDi 14 kg/lb.ft.
    The Toyota Landcruiser II (SWB) 14 kg/lb.ft.
    The Daihatsu Fourtrak EX 12.6 kg/lb.ft.
    The Daihatsu Sportrak EL EFi 16 kg/lb.ft
    
    So, at least as far as engine "grunt power" is concerned the Niva is a
    competant performer - certainly no worse than several others.
    
    The Daihatsu would be great except that the ground clearance and
    suspension both leave a lot to be desired.
    
    The Disco and 'Cruiser are clear winners - but you could buy three
    Nivas for the sort of price either of those bring!
    
    /. Ian .\

is it bad (in terms of wear etc) to change gear without use of clutch
when the engine is not running?

ta,


...art

    But I can't remember for the life of me why.

    
    .61, Changing Gear without Engine Running !
    
    Why would you want to do this ? Apart from fiddling around 
    waiting for the missus to finish shopping ;-)
    

>>  Why would you want to do this ? Apart from fiddling around 
>>    waiting for the missus to finish shopping ;-)
 

I guess that reason; just saw someone doing it and it made me wonder if
it was a bad thing to do?!


...art


ps. is it any better if the clutch is depressed before fiddling around?