Cranking oil pressure

[Pazza]

Hey all,

Does anyone know what oil pressure you should expect when turning over the engine with the starter motor?

We have an f4i with a dry sump setup. When we switch on the solenoid, a mechanical gauge indicates 3-4 psi. This is with no ignition, just turning the motor (like primeing the engine).

We made an adaptor that holds in the pressure relief valve and we thought this was an issue, but we took it out and blocked it up and thew same pressure level was attained.

Thanks

[Pazza]

Hey all,

Does anyone know what oil pressure you should expect when turning over the engine with the starter motor?

We have an f4i with a dry sump setup. When we switch on the solenoid, a mechanical gauge indicates 3-4 psi. This is with no ignition, just turning the motor (like primeing the engine).

We made an adaptor that holds in the pressure relief valve and we thought this was an issue, but we took it out and blocked it up and thew same pressure level was attained.

Thanks

[BeaverGuy]

That seems like it would be about right. I don't specifically remember the oil pressure at cranking as we never thought to look at it. However, we see about 20psi at 4000RPM when warm and twice that when cold on our ZX6R.

[Dave M]

we also get around 20psi at Idle. It it picks up just off idle. You guys should be fine. Start it up and if it doesnt pickup in 3-4 seconds, then shut it off.

[drivetrainUW-Platt]

Ours was reading 0 when we crank it, I asked the engine guy and he said watch it once it starts. It jumped right up no problem.

[osubeaver]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">made an adaptor that holds in the pressure relief valve and we thought this was an issue, but we took it out and blocked it up and thew same pressure level was attained. </div></BLOCKQUOTE>

I believe the pressure releief valve on the ZX-6R for example goes off at like 60 psi, so you really shouldn't have to mess with that. You're definitely not going to see that kind of oil pressure on cranking. The starter motor turns the motor pretty slow (i think around 300-500 rpm), so 3-4 psi is definitely not unreasonable for these speeds. A lot of engine damage on a street car actually can occur during start up because you have such low oil pressure (I emphasize street car because they are turned on and off so often and in such varying conditions). That's sort of how it is, being that the oil pump is coupled to the crank shaft, unless you have an electric oil pump or something like that.

[Pazza]

Cheers for the suggestions

Well we started the bitch up and we got oil pressure. 25 psi at 3750. We couldnt get it to idle below that. But when we cranked her up to 6000 rpm we were still seeing 25 psi. This is not good because the pressure relief opens at 71psi at 6000 rpm or so.

We had to back track. We looked at the feed for our pressure pump. We were using -6AN fittings. (oil from the bottom of our oil tank was fed through this and then into the pressure pump) The internal orifice was 8mm. The standard pickup is 20mm.

We have concluded that the -6 sizing is too small. As engine revs rose the oil level in the crank case rose which was a clear indication that the pressure pump could not get enough oil.

Orifice size is critical throughout the system. The reason that we used this size is because the scavenge runs off the same shaft as the pressure pump and water pump and is located into the crank case. Great idea but we have to feed the pump with bigger line.

We are going back to wet sump to do our map and will be trying to get the larger feedlines integrated asap.

Any comments here are welcome and are greatly appreciated.

Regards

Pazza
UniSA Motorsport
Adelaide, South Australia

[Travis Garrison]

Make sure you leave room for plenty of flow on that relief valve...once you get your pressure lines sorted, you'll see pressures of 100+ psi well below redline if you leave that thing blocked off, or fail to provide stock clearance on it's shroud.

[Dave M]

-10 line will give you what you need. We used to use a -8 for our return line on the external pressure regulator

[osubeaver]

So you are saying you were using 6AN fittings on the return line of your dry sump? When you say pressure pump, you mean the stock oil pump, right? Why do you need to run any lines for that?

On our dry sump, we use -8 AN for each pickup in the scavenge system (there are 2 stages), and a -10 AN for the return to the oil tank. It seems to work pretty well. I always figured that using a slightly larger hose for the the scavenge system would help because it will keep the velocity down and hopefully foam the oil a bit less when it enters the tank.

[Storbeck]

"As engine revs rose the oil level in the crank case rose which was a clear indication that the pressure pump could not get enough oil."

I don't understand this, seems like if oil level is rising in the crankcase that would be a scavange pump problem. Or the pressure pump pumping too much, but that sure doesn't seem to be the case. Could someone explain?

[osubeaver]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Storbeck:
"As engine revs rose the oil level in the crank case rose which was a clear indication that the pressure pump could not get enough oil."

I don't understand this, seems like if oil level is rising in the crankcase that would be a scavange pump problem. Or the pressure pump pumping too much, but that sure doesn't seem to be the case. Could someone explain? </div></BLOCKQUOTE>

If your oil level is rising in the crank case then your scavenge pump can not keep up with the pressure pump, right?

[Storbeck]

That's what I thought.

It sounds like his pressure pump wasn't getting enough flow because the line from the resevoir was to small. Didn't see the connection between that problem and the level in the crankcase rising.

[Pazza]

Yes you are right I wrote the wrong word. We had two major flaws in the system, in that the hose sizes were too small and our scavenge was totally inefficient. We used a stock oil pump off a 6 cyl and ran it in reverse. This meant the oil inlets were not going to work in our favour: because when the gears were in a position of maximum suction the oil inlet had closed off.

Just about the pressure pump feed with -6 hose: The system worked like this.

1. Oil is pumped through a remote oil filter and then through the engine by the standard oil pump.

2. Oil ends up at the bottom of the sump where the scavenge pick-up sucks it into the external oil tank.

3. At the bottom of the tank the return line goes to the pressure pump pickup. I.e it is hard plumbed into the crankcase so that the sump can be removed easily.