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Posted: Thu Oct 22, 2015 10:05 am
by T04GTR
hello all.
can we have a pre start engine oiling pump strategy? (electric oil pump to prime the engine before the starter is engaged?(dry sump engine)

also have a similar output to control oil accumulator/pump if unstable oil pressure detected? usually if oil surge happens it will flutter the pressure say minus 10-20 psi off currant pressure but not loose pressure all together



Posted: Mon Oct 26, 2015 8:32 pm
by pat
Hiya T04GTR!

Pre-start oil priming is something I did on an Impreza many years ago to get round one of the perceived issues with that engine design. It worked well, but I had it on a manual switch. Was pretty cool for doing oil changes too. Just wind off the filter, put a bucket under the engine, turn on the pump, wait for it to empty the sump, wind on the new filter, fill with oil, re-prime, job done. Bearing wear only happens when there is no hydrodynamic barrier, and if there is always oil then the only time you get no barrier is if the oil is too poor for the application. In short, a damn good idea :)

The question about priming is interesting. Haven't done much with it since few people actually have a means to prime, and of those that do, most will have an Accusump or something like that. The issue there of course then becomes one of limited time. The Accusump empties eventually. So... in order to do this *right* we would actually need to interrupt the start signal, use it to fire the pump or Accusump valve, wait for the pressure to stabilise a little, and only then allow the starter to turn. We can't just enable it when the engine is stopped since that would only work for a pump. But then you have an issue interrupting the start signal. And on something like a GTR where it is routed through the body control module (or some other power control module, I forget exactly where it goes), the issue is that it will only crank for so long before giving up. And it will be more than a little confused if it doesn't see the engine spinning..... so to "fix" that we'de also need to pretend that the engine is spinning - outputting virtual RPM both on the CAN bus and also on the Tacho pins.

As you can see it is not a trivial thing to do. I suppose with some thought it could be done. For your application you could probably use the Starter Enable strategy on the ECU and have that lock out the starter - so it will run the pump and also enable the starter, ergo you cannot crank unless the output is on, and if it is on then your pump will be running. It won't stop the starter from turning the engine until pressure is achieved but as a quick solution it would work. Adding a starter lockout strategy based on oil pressure could be done and that should be fairly trivial. So between the two I guess that you could make your installation work automagically.

With regard to firing the pump if unstable oil pressure is detected... I think you're clutching at straws here. *IF* you are getting aeration in a dry sump system then I can't see an electric pump doing any better. You will of course need a one way valve - there are some nice low forward drop ones from Mocal which will work well. But trying to push the volume of oil you would need to overcome an issue with the main pump, when it is fed from the dry sump tank (ie pretty much ideal conditions) is going to be a nightmare. You'de need a high displacement pump, and unlike the one attached to the crank which can have many tens of horsepower to overcome pumping losses with cold oil, your electric pump is going to have to be huge if it is to have any chance of still working when it is cold. Added to that the fact that the oil in its feed pipe will be cold when it is needed to give pressure, and you relly have got the worst of all worlds. Nice idea, great if it could be made to work, but not as trivial as it might first seem.

Hope this helps,



Posted: Thu Oct 29, 2015 9:10 am
by T04GTR
thanks pat. nice reply.

i actually have a pre oil pump on my evo pajero to stop the death rattle. super ghetto using a hobbs switch. power from the start solenoid supplies a ssr. start signal powers the pump and when oil pressure is reached it switches the relay sending power to the starter solenoid. (had to play with some capacitors across the trigger to avoid "bouncing" the relay.

the pump i question is re-purposed aviation oil or fuel pump (spur gear) with a ampflow dc motor i modified to drive it. cold 10w40 oil 10 bar pressure on a stopped engine.

i could set up a pdu strategy with not much mucking around now that i think of it. cheers.