Engine On/Off, Pressure Lubrication, Engine Wear

[Simonas]

We've all heard it, right? "Most engine wear occurs when starting the engine".

I've read of engines running for something like 50 years without a stop for an electrical plant or something like that. Then someone tears it down and finds that the bearings look like new.

The theory behind it all appears to be that after an engine stops, the oil, by gravity, drains out of all the bearings. The bearings rub more or less directly (though there will probably be a minuscule oil film still on it) Then, when someone starts the engine, there is a split second where nothing is lubricated. This is a bigger problem with OHC engines than other types, as the cam is the farthest component from the oil pump. At least it is on all the engines I know.

Some manufacturers try to help the problem by using thinner oil, and then just making bearing clearance smaller. This works well, but the engine still isn't lubricated when you first start the engine.

So... I was pondering the problem and thinking about how wonderful it would be to have an engine that was lubricated before the engine started. So I came up with an idea. It is actually quite simple.

First, lets assume your oil pump normally gives about 65psi. Of course, the pressure varies somewhat depending on engine speed. Assume that the pressure release valve starts dumping oil back to the crankcase at 60psi. Now, you tap into the oil channels after the pump, but before the pressure release valve. You connect a hidroaccumulator much like a water tank (capacity of about 250ml.) in there, then hook a one way electric valve in front of the hidroaccumulator. When the valve is closed, fluid can enter the hidroaccumulator, but not flow out. When the valve is opened, fluid can flow in either direction.

Using this arrangement, if the hidroaccumulator is full when then engine is stopped, you can hook everything up electrically such that until the engine stops, the valve is closed. When the engine is not running, the valve should be closed. Then, when the key is turned on, the valve opens and sends oil throughout the engine before the oil pump even starts working. Once the pump starts working, your accumulator pressure has fallen, so if it is as, say, 45psi, the pump pumps it back up to 60 and the engine and accumulator fill. Ideally, there should a biased valve in there to make sure the engine gets oil before the accumulator. Using that type of hydraulic circuit, the accumulator is filled with the extra pressure and volume that would have been spit out the pressure release valve.

A manual switch, or a switch that only goes off with the glow plugs would be required with diesel engines, as the accumulator would probably be dry before the engine is turned after waiting for the glow plugs.

Also, this would be particularly beneficial on engines that have holes in the connecting rods for oiling the cylinder wall.

Another side benefit is that theoretically, one should be able to use thinner oil because there is no minuscule oil film needed on the bearing surfaces.

BTW, I'm not responsibly if you try this and blow your engine. So far, this is only a theoretical solution for the increased engine wear caused by repeated engine starts and stops.

Feel free to critique my idea, its advantages and problems and whatever else I may have said wrong or right

[Frank Lee]

The engine seems to be the last thing to fail; the rest of the car is junk first.

[markweatherill]

"Most engine wear occurs when starting the engine"

I read somewhere that this is true, but not because the engine is grinding itself away due to lack of lubrication, more like wear from acidic blow-by - on cold starts. Warm starts, much less of either.
Even so, pre-oiler devices do exist.
But for repeated warm starts, I would say they aren't needed. To aid cold starts, engine pre-heating might be a better solution.

[redneck]

So... I was pondering the problem and thinking about how wonderful it would be to have an engine that was lubricated before the engine started. So I came up with an idea.

Someone beat you to it.

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[Simonas]

I hadn't heard of the acidic blow by problem, but wouldn't that be because the stuff is getting by the rings? The oil should help keep the rings seated and not let the stuff blow by.

Also, faster starters would be preferable to slow ones as the rings would have more pressure against them, making them seal well before the engine even fires.

I suppose engines not wearing out is less of a problem now than it was thirty years ago. I'm rebuilding an engine that was rebuilt once before at a minimum, and before that there was another engine that was the original. Either the guy didn't change oil or something...

Interesting... The price for that accumulator is quite high. I mean, for that price you could buy a 3000 psi accumulator. Just a normal water pressure tank would work assuming it could handle 70psi and the bladder wasn't affected by the oil.

Also, the electric valve kit doesn't appear to be made to prelubricate the engine; that has to be done manually...

I have an electric valve that is for 3000psi, a one way when off and two way when on type. It cost $48 at surpluscenter.com.

I also have heard of electric pumps that keep oil flowing to a turbo even after the engine is turned off.

[cRiPpLe_rOoStEr]

One thing I like about 2-stroke engines is the absence of a valvetrain to wear out

But I agree with you regarding your concerns about engine wear when the head is still not soaked in oil right after the start-up.

[RobertISaar]

a lot of high-dollar racing groups already do this..... if you ever see their shutdown procedures, they run the engine up for a few seconds, then idle, then shutdown. while the engine speed is raised, they're filling the accumulator and then closing a valve on it to prevent it from running back out when the engine speed(and oil pressure) come down and finally stop.

it works, and it pretty well at that, but considering the average engine already can go 200+(or 300+)K miles without any kind of lubrication failure(assuming the oil and filter are changed when they need it), it seems like an unnecessary expense.

if you had an engine that you knew was weak in this area..... could certainly be useful.

[serialk11r]

Accusump haha. I'd put one on a car that might ever see the track unless the car was already dry sumped or something. Also since I take turns fast to save fuel, preventing accidental oil starvation is also possibly a good idea (it happens on some cars stock!).

Porsche has an electric primary oil pump I think, which prelubricates the engine before start up. Not sure how much it helps, it seems like bores usually oval out before bearings go since they are not well lubricated compared to the rest of the engine.

[oldtamiyaphile]

Are you guys familiar with Castrol Magnatec? I use it in my rarely driven Jeep (about four times a year for a total of ~1000km), and dry valve train noise is completely eliminated even after standing for a month.

I was skeptical for a long time but it really does work. I also used it in my MB100 which needed EOC to get any sort of decent milage, just in case.

[Thenorm]

Originally Posted by Simonas

I also have heard of electric pumps that keep oil flowing to a turbo even after the engine is turned off.

thats waht i was thinking. electric oil pump to get things circulating and upto pressure before cranking engine