Electric Oil Pump??
Electric Oil Pump??
(OP)
Just a crazy old Structural that likes to break things - and fix them.
If we believe all the oil advertising and engine mfgs, they say the worst engine wear happens during the first few seconds of startup due to lack of oil pressure.
Why not install an auxiliary electric oil pump that cycles for a few seconds before ignition and then shuts off once started. Seems simple and couldn't cost too much. Or am I just missing something here??
If we believe all the oil advertising and engine mfgs, they say the worst engine wear happens during the first few seconds of startup due to lack of oil pressure.
Why not install an auxiliary electric oil pump that cycles for a few seconds before ignition and then shuts off once started. Seems simple and couldn't cost too much. Or am I just missing something here??





RE: Electric Oil Pump??
http://www.accusump.com/
RE: Electric Oil Pump??
Mike Halloran
Pembroke Pines, FL, USA
RE: Electric Oil Pump??
Cheers
Greg Locock
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RE: Electric Oil Pump??
A better system might be to incorporate a starting protocol into the ECU that delays start up until the oil has reached all bearings and to severely limit power until it has had time to splash onto the bores then somewhat limit power until a reasonable operating temperature (and therefore internal clearances) is reached. Oh that's right, they mostly already do the last one.
As Greg already implied. It solves a problem that really does not exist as most engines outlive the car they are in.
Regards
Pat
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RE: Electric Oil Pump??
Regards
Pat
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RE: Electric Oil Pump??
The Toyota Prius does that...
Ignition and fuel is not applied until oil pressure is up..
And, there is sufficient range in the variable valve timing to delay closing of the intake valve to the point of serving as a compression release during the initial spin up of the engine.
RE: Electric Oil Pump??
I disagree that this "wear" is excessive in most street applications. It is not at all uncommon to have modern engines make 400,000 miles and still be serviceable. My son and I put over 385,000 on a '77 360 Dodge PU before we sold it and there were no problems in the engine dept.
My auto insurance agent has a MB that is at the 400k mark.
My point, is that this simply means that there is no incentive for OEM to do anything with pre oilers/after oilers/accusumps, etc.
For the uninitiated--- I use the Canton 3 qt. Accusump with an electric pressure (55psi in the Mini, 35psi in the Lotus) regulated solenoid and prior to any cold startup crank the engine over several times before turning on the ignition...simple...and...if the engine has been sitting around over the winter, I take out the plugs and crank it over for a bit before final startup. Again, simple.
Rod
RE: Electric Oil Pump??
RE: Electric Oil Pump??
Most of the sliding contacts in a recip piston engine (rings, wrist pins, valvetrain, etc.) are capable of operating safely for short periods with whatever entrained oil is present at start up. Most of these components normally operate with boundary type contacts and thus don't require much oil to be present.
As for the hydrodynamic contacts present in the main and rod bearings, these also do not require much oil flow at start up. The oil volume that must be present to produce the load supporting hydrodynamic film is extremely small (ie. a small drop). The normal operating oil flow required by journal bearings is based entirely on cooling requirements. And for the 2 or 3 seconds of light load, low speed operation at start-up before oil pressure is built up and flows begin, no real damage should be occurring to the bearings since they won't build up much heat.
Bearings are more likely to fail due to surface fatigue, corrosion, or contamination. Not "wear" at start up.
Regards,
Terry
RE: Electric Oil Pump??
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Electric Oil Pump??
They have pre-oilers, as specified by the customer.
Mike Halloran
Pembroke Pines, FL, USA
RE: Electric Oil Pump??
I have also experienced engines that have run for several hour with an empty sump, so not even enough for real splash feed.
The role of oil pressure in my opinion is to provide enough flow to cool the bearings to allow the great increase in speed rather than load that modern engines utilise.
Not having oil pressure at start up therefore is no serious disadvantage so long as the surfaces are wet with oil and the time until pressure builds is short enough to prevent excessive heat build up. At low rpm and load this is a considerable time. Unfortunately once heat starts to build, clearances close down, then heat builds faster then clearances close down faster etc etc
The ECU restricting power output and speed significantly until oil pressure is obtained should solve any problems if they in fact existed.
Regards
Pat
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RE: Electric Oil Pump??
As to the 'splash oiling' of early engines v bearing wear at startup...I think I have posted here a time or two that in Jan, 2000 I rebuilt my 1930 Ford engine with machining for modern bearing shells, counterweighted crank, solid valve guides w/Buick SS valves, etc. Well just last year the engine lost a head gasket and hydrauliced the #4 cylinder bending the OEM rod.
Fast foreword---New engine is in place with aftermarket rods, etc.---At teardown we inspected the bearing shells of rod and main with some 25,000 miles of use in a totally splash oil system...NO APPRECIABLE WEAR! in fact, the bearings still looked NEW.
Now what does that say about pre oiling? Not much. I simply cannot compare my Model A engine at ~4:1 CR with my Mini Cooper engine at 15.33:1 CR...Loading on the bearings at startup are vastly different.
Until someone can show me different, I'll stick to the system of oil accumulator/pre oiler that has proven effective for many years.
Rod
RE: Electric Oil Pump??
That's a good question. There's a few things I can think of that could be done, although I would not specifically classify them as "compromises".
For one, the ignition spark can be interrupted briefly when the engine first cranks over, as well as keeping the throttle fully closed (SI engines only). This will limit the max pressure loads on the crank and rod journals.
The layout of the lube circuit can also reduce (but not eliminate) the delay in oil flow to critical points like the crank and rod bearings. Most auto engines are wet sumps, and putting the pressure pump inlet at or below the oil level will promote rapid priming and minimize the delay getting oil flow going. The same goes for the way the filter bowl/housing is positioned, so that it remains full of oil during shut-down.
Another thing to consider is that no oil pressure at start-up does not mean there is no oil present at the bearings. There are drilled galleries between the crank journals that usually trap some oil at shut-down. When the crank rotates at start-up, this oil will be pushed out to the rod bearings.
As I noted in my previous post, journal bearing oil flows are entirely a function of cooling requirements. Creating a load supporting hydrodynamic oil film takes very little oil volume. Having full oil pressure feeding your crank's journal bearings provides no benefit for the few seconds at start-up, versus simply having some entrained oil present within the bearing gaps. The fluid pressures within the hydrodynamic oil film can be 20,000psi or more. The pressures are created through viscous effects in the oil itself, and not by the pressure of the 60psi oil circuit feed.
With regards to the original post, while an electric oil pump would not really help with perceived "wear" issues at start-up, it would have other benefits. The most important being the ability to vary flows independent of crank speed.
Hope that helps answer your question.
Terry