Engine Oil Pressure

[Doughnut]

Hello Everyone,

We tested the stock Honda CBR600RR as well as our custom oil pan with the help of an Oil Pressure sending unit and gauge a couple of days back.

These are the pressure values we got for different RPM's:

Stock:

4000 6000 7000 8000 9000 10000 11000 12000
40 78 85 90 93 95 95 96

Custom Oil pan:

4000 6000 7000 8000 9000 10000 11000 12000
62 88 94 96 97 100 102 102

I just wanted to know if these readings are acceptable. Are they too high? I've read on a couple of other posts that the oil pressure relief valve opens around 70-80psi. Shouldn't the pressure values be restricted to that range then?

[Ockham]

Unless you're talking about 100,000-mile durability, slight deviations from stock oil pressure won't cause any worries. The crankshaft, rod, and camshaft journal wear characteristics will change, but that shouldn't cause any real trouble over the relatively short life of an FSAE engine.

For some reason, the 78psi regulator in the 600RR engine doesn't seem very predictable. We logged oil pressures at 200Hz with and without our first-generation dry sump system, and were able to see the pressure spikes from the relief valve fluttering open and closed. In spite of living in an oil bath, there's apparently high stiction in Honda's design, which may explain the oil pressure deviations many teams see with custom oiling solutions. But it's nothing to lose too much sleep over.

[VFR750R]

What was the oil viscosity and temperature.... even with a bypass set at 78psi, you'll get higher readings if the oil is cold. It effects the amount the regulator will flow at a given opening meaning you'll have to open it more to flow the same volume flow rate of oil. Additionally, temperature effects the clearances in the engine meaning less oil is flowing to parts/pieces, and more must flow through the bypass.

It could also read hi if you're reading it pre-filter, but you're probably ok there, that's hard to do.

You may also want to check your gauge. you know what they say, "A man with a watch knows what time it is. A man with two watches is never sure." Double check your gauge and or calibration.

[Wesley]

If you modified your pan and not your oiling system at all, nominally you'd have no change in pressures (provided you have proper inlet/relief port clearances) and you'd see any real problems as massive spikes or drops in pressure.

I think VFR is right, it sounds like temperature/viscosity variation in your numbers. An oil temperature gauge is invaluable for testing. Even if coolant temp is the same, oil temp could be very different.

[Jan_Dressler]

I agree with temperature/viscosity, different temperatures result in quite impressive differences in pressure.

Additionally, did you use exactly the same pressure relief valve (if you use the stock Honda one)? We had variations in pressure from about 83 to 92 psi at higher revs, at the same oil temperature, with the same lubrication system, only depending on which of our stock PRVs we were using.

[Pradeep]

We do have a oil temperature sensor also but we still need to make an adapter to fix it in th oil pan.

The readings were taken almost immediately after starting the engine, so I think the oil temperature would have been on the lower side.We'll do the test again with the oil temperature sensor.

I think Akshay forget to mention that we are using a custom CNC'd oil pan (the stock RR sump sticks out too much), not a dry sump. No other changes to the lubrication system.

@Jan_Dressler: yes we used the same pressure relief valve during both the tests.

Thank you all for the help.

[Adambomb]

One more note regarding the effect of engine temperature/oil temperature on oil pressure: in addition to the change in fluid properties, you also have engine tolerances that grow/shrink with temperature, most notably crank and rod bearing surfaces. Just one more reason oil pressure typically drops as an engine warms up.

As for having pressures that are higher than relief valve pressure, I've seen that quite a bit in automotive applications. As far as I know that's mostly due to the relief circuit providing additional flow restriction (much like a turbo with too small a wastegate). Seems to be much more common with "high volume" oil systems and "tight" engines. I've got a Buick V6 with a high volume oil pump and 65 psi relief valve, it typically gets to 80 psi or more when cold (according to a crappy gauge that I don't personally have a lot of faith in, FWIW). When warm it drops to under 30 psi at idle, maybe 60 psi max. As far as I know the biggest problem with excessive oil pressure (outside of unwanted parasitic loss) is excessive wear on all the parts that drive the oil pump, or the chance of shearing an oil pump drive shaft on engines with distributor-driven oil pumps.

[Doughnut]

Hello,

We ran into another problem a few days back. When running the engine, the oil pressure gauge suddenly started to show zero pressure.

We stopped the engine immediately, opened the oil pan and checked if everything was alright. The strainer and oil pressure relief valve were both intact.

After checking if everything was okay, we ran the engine again, suspecting it to be a problem with the sensor. The gauge showed us a reading initially (around 20 psi), went back to zero in a couple of seconds and then would go up to 15psi when the engined was revved higher. The engine seemed to run smoothly even with the gauge reading zero pressure, without any over heating or fumes being visible after 4-5 minutes of running.

We've since opened the oil pan twice more to check if things are okay. We are sure that the oil pump is working, since the level of oil in the oil window is decreasing when starting the engine. We have also tried using two different pressure sensors, but still the same result.

We are a little clueless as to whats wrong at the moment and were wondering if anyone has faced similar problems before?

[Akos]

Doughnut,

Sounds like you are cavitating your oil pump. Did you modify the oil feed to the pump, added additional bends or restrictions?

If unsure, use a mechanical gauge. Fire extinguishers come equipped with a convenient (not very accurate) but readily available gauge.

Akos

[Doughnut]

Hello Akos,

Thanks, I appreciate the prompt reply.

We ran the engine again a few hours back after changing the oil pressure relief valve. The pressure sensor gave us perfectly normal readings for around a minute after starting and then suddenly went back to zero.

If we were facing cavitation issues, shouldn't the pressure sensor still give us some pressure value(instead of resetting back to zero and staying there)? I understand it blanking out momentarily but can't somehow seem to understand why it should continue to show no pressure. I'm reading up on cavitation and this is the first thing that came to my mind.

Lastly, we were planning to lambda tune the engine tonight and were wondering if we should go ahead with it? Or should we just wait and figure this out first?

PS: Yes, we have used a different strainer, but there are no bends in it, in fact it goes straight into the pump.

[Wesley]

If you're concerned with the sensor/wiring giving you problems, I'd suggest hooking up a mechanical gauge if you have one. I don't recommend them for in-car setups, but for testing they're valuable when you're trying to chase wiring gremlins.

I would advise against running it until you eliminate the possibility of an oiling problem. Engines are too expensive (and sometimes hard to find) to guess about something that critical! Good luck!

[Doughnut]

Originally posted by Doughnut:
Hello,

We ran into another problem a few days back. When running the engine, the oil pressure gauge suddenly started to show zero pressure.

We stopped the engine immediately, opened the oil pan and checked if everything was alright. The strainer and oil pressure relief valve were both intact.

After checking if everything was okay, we ran the engine again, suspecting it to be a problem with the sensor. The gauge showed us a reading initially (around 20 psi), went back to zero in a couple of seconds and then would go up to 15psi when the engined was revved higher. The engine seemed to run smoothly even with the gauge reading zero pressure, without any over heating or fumes being visible after 4-5 minutes of running.

We've since opened the oil pan twice more to check if things are okay. We are sure that the oil pump is working, since the level of oil in the oil window is decreasing when starting the engine. We have also tried using two different pressure sensors, but still the same result.

We are a little clueless as to whats wrong at the moment and were wondering if anyone has faced similar problems before?

Well, we ceased an engine day before yesterday... the 3rd piston ceased and we've got a broken connecting rod by the looks of it.

Now, we were running this engine on a CNC Oil pan. We'd installed the pan around 2 weeks ago and the engine seemed to be running perfectly with it. Then, what I've quoted above happened.

We ran the engine with the gauge showing zero pressure for almost 3 days, [suspecting it to be a problem with the sensor and double checking if everything was okay within the oil pan- relief valve, strainer both intact and no visible damage of any sorts )including a day when we ran it on load a couple of times to test run the car. And there seemed to be no problem at all.

However, when we ran the car day before, we had blowby streaming out of the catch can virtually instantly. The engine ran for another 2 minutes or so and then jus suddenly mellowed down, as if it had lost a cylinder.

We found pieces of the connecting rod in the oil pan on opening it.

Now, we were running the CNC Oil pan along with a cut Honda F4i strainer(chose that instead of the RR's cuz its made of steel which can be welded easily), 2 baffles and a windage tray. The strainer is a bit different, but has no bends, goes straight into the pump.

I'm postin photos of the oil pan, wanted to know if anyone can find something at fault which none of us can.

Without the windage tray....the two baffles and the mount for the oil pressure relief valve between the baffles on the left.

http://www.4shared.com/photo/7GyRjJxT/Photo0274.html

With the windage tray after the engine failure...
http://www.4shared.com/photo/Cw29Fk8I/Photo0285.html

As of now, we've installed a cut pan on the new engine... which is basically a shortened version of the stock oil pan... we tested it yesterday...and at least up till now.. it seems to be running perfectly...


I also wanted to know what is generally considered to be an acceptable oil pressure drop while cornering... in terms of percentage... We're going to start testing the car around a track now and i wanted to know what kind of data is acceptable... Its something we've never done before.. and are going to be very cautious about especially after blowing up an engine..

Will be glad if anyone could help...

[oz_olly]

I had a look at your pictures. Does the pick up almost completely fill the circular hole in the windage tray? I don't know much about how quickly the oil flows through your windage tray and down to the pick up but it could be that the flowrate into the pick up is signifcantly higher than the flow rate through the windage plate. If this was the case the majority of your oil could be pooling on top of the windage tray leaving little to no oil for the pickup to suck up. This could have the follow on disastrous effect of splashing your crank shaft with oil.

To eliminate this you could measure the oil flow rate at operating temp through your windage tray (with the pick up in the right spot). If it is much lower than the rate at which your pickup sucks the oil, this could be the problem... Or I may be completely wrong.

Have you checked the internal oil pump? It may have stopped working. In our GSXR 600 the oil pump shaft is quite a small diameter so I could imagine a small foreign object could jam the pump causing the shaft to break. However, seeing as you said you were getting a huge amount of oil in the overflow it makes me think the pump is still working but not seeing enough oil at the pick up.

Let us know what you're problem is when you figure it out. Did the conrod do much damage to the block?