Any opinions as to what the effect might be of only driving a 940 turbo 3 days a week?

Is it bad for the engine to routinely sit for two days without being started... and then start it up?
I'm wondering if the oil might totally drain away from the rings and turbo and therefore cause damage at startup...

I know it's proably impossible to prove anything one way or the other... but thought I'd ask anyhow.

If you really want optimum engine life what you should do is drive the
car at constant speed on a highway 24/7 and refill on the roll - NO STOPS!!

I once bought a Buick 364 engine that had been run the equivalent of 350,000
miles with only a couple startups, and it had very little wear, certainly not
enough to do anything about it. On the other hand they had used the dynaflow
tranny to couple it to the dynamometer, in "drive", and I broke the shift
linkage trying to change gears. Had to clean the spool valve block with carb
cleanter. The biggest downside was that it had factory 14:1 pistons and
12 volts would NOT crank it at operating temperature. If the pistons were
cold it would start fairly easily. I had it mounted in a 1951 Cadillac
funeral coach which originally had a standard tranny so it peaked out at
about 85 mph but it got there pretty quick.

Dear Peter,

Good p.m. My guess is that an oil film clings to cylinder walls, rings, bearings, etc. Oil is pretty viscous, so even if free liquid has drained back into the pan, oil will cling to working surfaces. Over a three-day period, even if a high-temperature climate, this film is likely to be plastic. Over several months, especially in a high-temperature climate, this film likely will dry.

If inadequate lubrication at start-up - after a period of idleness - were a major issue, I'm sure cars would have electric oil pumps. Such a pump would pre-pressure the system, just as does the fuel pump (for 1-2 seconds, after the ignition key is moved to the "start" position).

As the starter motor turns the engine a for few seconds before ignition, the oil pump should restore at least some of the oil pressure.

I'd be interested to know, from those, who have an oil pressure gauge, how quickly the gauge shows positive oil pressure, once the ignition has been put into the "start" position.

Hope this sets your mind at ease.

Yours faithfully,

spook

My 'other' sporty type car is a Jensen Healey. The engine in a Lotus 907, which had quite a reputation for lack of upper end lubrication on startup. Many owners, as evidenced by their testimonies on th JH webpage, have resorted to installing a pre-oiler. These are no uncommon on mofdified engines, or those with simalr reputations to the Lotus. It consists of an electrically operated pressurized oil can which sits in the engine bay, that, when signalled at pre-stat, injects presurized oil into the engines galleries. One may sit in the driver seat and watch oip pressure climb to 70ps1 before starting the engine. This is a comforting thing to see when one has been used to seeing no pressure on the gauge for 4 to 5 seconds post-start on a high priced Lotus engine.
If you want I can dig up the links.
Cheers
JD
Fort St. John BC
65 1800S
74 Jensen Healey
84 24GLE
89 760GLE
92 960GLE

Thanks Spook...

I sometimes think that cars ought to have some kind of hand crank to get the oil flowing first before the real force of ignition moves the cylinders. I seem to remember reading somewhere that most of the wear on engine rings, etc. occurs at startup.

Dear Peter,

May this find you well. You're right about "most of the wear on engine rings, etc. occurs at startup". However, using a hand-crank to turn the engine, and so to circulate oil, would be inconvenient and would require considerable upper-body strength to move. It would also require passage for the crank, through the radiator and the grill.

It would be better to have a secondary, electric-powered oil pump, which pre-pressurized the oil system, so soon as the ignition key had been moved towards "start". Fuel pumps on 940s pre-pressurize the system, when the key is turned.

Yours faithfully,

spook

Yeah, the last time I owned a car with a hand crank was a '72 Land Cruiser, back when they were really off road vehicles. I am here to tell you that if hand cranks became a method of getting oil up to the rings, etc. we'd be looking at a decidely different level of upper body strength in our population.

Beyond this, how do you people sleep at night with all these insideous assaults on your car lurking in the dark corners of your mind?
--
John Shatzer, '97 V90 @ 110K

Dear John,

Good a.m. and hope this finds you well. On both points: Well said!!!!

Yours faithfully,

spook

interestingly a lot of cars DID have handcranks goign thru the grill & rad...my father-in-laws morris minor (1960's) still has this feature...and it can be used to START the car, indeed in the not to distant past this was how all cars were started!

many motorbikes (even some current high compression two stroke off road ones) have a feature that allows the cylinder to be de-presurised for this purpose...but we digress...

there are devices on the market that allow a charge of oil to be held at the head of the engine then released via an electrically operated valve into the head, i believe (never seen one!) that this is operated by the key goign into 'run' position.

I personnaly have a couple of issues with this...(1) it still doesnt lubricated the rings...(neither i suspect would an electric pump) (2) think when you fill a car with oil howe long it takes for it to drain to the sump...you realy need a minute or two for the oil to drop...


waht would be MORE interesting would be a way wehre you could use the starter to turn the engine over slowley (relatively) with the ignition & fuel injectors disabled....

When starting a car that's been sitting a long time (several weeks, or even months) it's common practice to remove the coil-to-distributor wire, crank the engine for several seconds to allow oil to come up to pressure, then re-connect the wire, and start the car. It does nothing for the rings, but it helps in other areas.

That being said, I agree with Spook that a few days isn't enough to worry about.

To answer the question about how quickly oil pressure comes up... on my Benz, it's about one second after the engine starts. About 2 seconds after the starter in engaged. I'm sure it varies from car to car though.

Jeff Pierce
--
'93 945 Turbo ( one kickass family car ! ), '92 Mercedes 190E (my daily driver), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece -- sold to a loving home), '85 Jeep CJ-7 w/ Fisher plow

My first car, a 1963 Triumph TR4 sports car had the radiator/grill holes and the dog in the front of the crank shaft extension for a hand crank. So I bought one, thinking it would come in handy if my battery ever went flat.

As was inevitable, with Lucas electrics, the day came. What a joke it was to try cranking that engine by hand. I could only turn it over by letting the compresion pressure leak away. Never could I have turned it through compression in a manor to make it start!

BTTT, (Been There Tried That)
--
'96 965 with 16' wheels at 120K. Had '85 745 Turbo Diesel for 200K.

Dear the kick inside,

Good p.m. To disable the fuel injectors, one need only have a loop - with a switch - on one wire from the radio interference suppression relay. Open the switch, and no power flows to the injectors. As a result, the starter moves the engine, the sparkplugs fire, the valves move, but the engine does not start, because the injectors aren't working. Equally, the wire that is switched could come from the RPM/crank relay. If there's no signal from the relay, the fuel pump does not stay running, so the engine will not start.

By either means, the starter would turn the engine, and the oil pump would move oil through the system, before ignition could occur.

When the switch was closed, the flow of power to the injectors - or to the fuel pump - would allow ignition.

I think it would be well, to allow the engine to stop turning, before closing the switch, that allowed the normal starting sequence to unfold.

This would not involve getting out of the car and using a crank. Whether it would damage anything, I can't say.

Yours faithfully,

spook