Increased crankshaft/bearing wear with stop/start systems - Fuel Economy, Hypermiling, EcoModding News and Forum

Frank Lee · 04-23-2011, 07:33 AM

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Basically they figure stop/start systems will go through 3x the number of start cycles than regular engines, and a start cycle is a cycle the crank and bearings experience lack of pressurized lubrication.

Of course if new bearing tech doesn't fix it, an oil pressurizing system could be added.

Those of you who extensively P&G might want to consider that 3x wear thing being a possibility for you...

tjts1 · 04-23-2011, 12:03 PM

Many cars with start stop already use an electric oil pump to reduce the load on the engine.

Christ · 04-23-2011, 12:15 PM

Shame that the warning comes from an advert, eh?

I don't disagree, but at the same time, I've seen plenty of really high mileage cars with no engine rebuilds on them to suspect that this is more like slick 50 and ptfe-additive oil.

vtec-e · 04-23-2011, 12:37 PM

I recall an article that mentioned that the crankshaft bearings etc was made of tougher stuff to hold up against the extra start/stopping. It was a while back though so don't ask me where it was!

bestclimb · 04-23-2011, 04:50 PM

Don't load your engine till oil pressure comes back up. Should solve most of the issue.

dennyt · 04-23-2011, 05:03 PM

I wonder which is greater - connecting rod forces before the oil pressure comes up (very low load, just compression), or the radial load from the starter pinion gear? What I'm getting at is, would hybrid systems with electric motors coaxial with the crankshaft avoid a major component of startup wear, by eliminating the pinion gear load on the crank bearings?

A quick calculation for my car: 92mm bore = 10.3 square inches, at 170psi (last time I checked compression) that's 1750 lbs on the connecting rod. I don't have my starter motor torque & pinion diameter handy...

320touring · 04-23-2011, 07:13 PM

Pulse withe E(on)c would eliminate this:0

Failing that, at £500 for a hunkajunk, I can get through 30 new(to me) cars before hitting the price of a car with start/stop

vacationtime247 · 04-24-2011, 12:55 AM

Should be less of an issue with good oil and smart use. I'd venture to bet that they were not nice at all to the test engines. Testing them under a worst case scenario. When I EOC, the engine is already at operating temp. Don't accelerate hard after re-start and be smart. Mostly use it on the Escort and it was a freebie. So if something terrible happens, I'm not really out anything.
VT247

rbrowning · 04-25-2011, 09:59 AM

I was always under the impression that the worst wear came from a "dry" start, after the engine had been off long enough to allow the oil toy drain down to the sump and reducing the remaining film too much. If you engine is only off a minute I don't believe that this is the case.

Unfortunately the engine is restarted as you are trying to accelerate with the herd away from a light. With an electric oil pump, you could give it a second or two to build some pressure or you could use an accumulator for instant pressurization, albeit with a more complex system.

euromodder · 04-26-2011, 05:51 PM

Quote:

Originally Posted by rbrowning

I was always under the impression that the worst wear came from a "dry" start, after the engine had been off long enough to allow the oil toy drain down to the sump and reducing the remaining film too much. If you engine is only off a minute I don't believe that this is the case.

Dry and cold - thick oil that doesn't lube as well.