Foaming oil?

[Mike]

His original message says something about a ZX pump. Steve, how did your oil do on the return trip? No problems? Or, did you say that you couldn't sustain the 90mph because of the cops?

Anyway, 20w-50 Castrol is decent stuff. I wouldn't think it did that type of thing. Did you verify that the oil was in fact bubbling up at all? Or, was that just speculation due to the dropping pressure?

Check the contacts for the sending unit and make sure they aren't working loose. Maybe you have a short and it gets worse as the engine heats up or as the wind blows through your engine compartment at 90+mph.

[Zvoiture]

1. I don't recall ever calling anyone on street racing. It's bad, yes. But we all own sports cars.....because.....??? And sports cars are produced.....because.....???? Women have breasts.....because.....???? Maturity removes impulsiveness, not testosterone.

2. I was not RACING. I was merely cruising up a reasonably deserted highway at an off-peak hour in an automobile which has had every suspension, braking, and drivetrain-contributing part replaced. I am in greater control of the Z at this speed than my any car I have driven. I drive my LS400 at 85-90 all the time, and nobody even notices. The driver doesn't even notice!!! "Oh, wow. I'm going 90. Wonder how long I've been doing that?" In control? Sort of. Aware of road conditions? No way. Driving the Z is like pointing your finger.

3. Brand new 280 ZXturbo oil pump. This is a very simple switch which gives you considerably more oil pressure.

4. No, I did not see the oil foaming. That was just a guess. A stupid one. I seriously doubt if the crank is slapping the 'lake' and there is no water in the oil....

5. I don't think the viscosity has anything to do with it. I also don't think heat is a factor. Once the engine gets hot, it isn't going to get any hotter. It was at operating temperature the first 5 minutes of going 4300 and driving it for 15 hours that way is not going to raise the temperature any. Likewise, once the oil has thinned down as much as it's gonna, it's not going to thin down any more.

6. I don't think temperature alone can be a factor on the operation of the sending unit itself. I suppose gradual heat rise on the contact wire could be?

7. Still, it HAS to be the sending unit. Somehow. I just can't picture modern oil (not to mention brand-new oil) causing this kind of situation in a motor.

8. The SU is also brand new. It is a NAPA, though, not a Nissan. Each brand has its fans among Z drivers and I have always found NAPA oem parts to be top-notch.

9. 4200 r's isn't extreme!?!?!? Is it? The car just starts to run good there! It is well below the yellow-line. Is it?

10. A cooler? The need for oune would suggest the oil in the pan is not the same temperature as the engine. I would think the oil would be the same temp as the engine almost immediately and stay that way. How can it get hotter than the engine?

11. Plenty of oil in the car too. My car holds 6 quarts.

12. Never did another sustained run like that again....Haven't since. The oil pressure guage still works perfectly. Don't know how accurate it is, but as I said before, it responds quickly and predictably to engine conditions. It used to be real sluggish, but put the new SU on and it practically follows the tach. Likewise, when I installed the turbo pump, all ranges took a very noticeable jump.

13. Maybe I could put fins on the pan. There has to be a certain cooling effect at 95! Speaking of which, anybody ever try those fins that go around a filter? Pretty dorky looking, but seems plausible.

Did I miss anyone? Just messing with you guys and thinking out loud...

steve77

[smg1404]

Hey that is what I run...... Steve ... That is a good name, since its is also mine.... Do not defend your driving habits.... In the right place (judgement required) I do no thtink speed laws apply. To heck with the guys with the guns, and stinking badges. Runn your arse off, If you run into the weeds and blow up it's your buisness. Try not to take anyone with you, unless you get lucky and get some psycho on the way. I think I would not get too concerned about the issue with the oil pressure. After all does the car still run OK?, dioes the pressure now look OK?, Was the circumstance a little beyond normal operating conditions (what the car was designed for).... SO what? If you plan to extend the operating parameters to include long term full throttle rides. then modify the car to handle the extra load. otherwise I think you do not need to spend your money chasing ghosts.

[2ManyZs]

FWIW, I ran Castrol 20-50 in my 280 ITS car for 4 years. Then the last year I ran Syntec.

High volume pump, mechanical oil pressure gauge and an oil cooler. Never had any variations in oil pressure even at water temps of 200-220 degrees. Always steady at 60 psi.

How many miles are on the bottom end?

[Seanh]

Actually.....that temp guage on your dash is showing the temp of the Coolant, not the engine, there shouldn't be a considerably difference, but they are different under some circumstances. So you oil could be hotter then your coolant is going to be. Oil can get hotter then the engine also, so don't rule out that as a possibility. An oil cooler would be a good idea if you plan on running that hard regularly. I would go ahead and slap an oil cooler on there anyway, I have one on mine. I also put an oil temp guage, and engine head temp guage in there also, so yeah, before I put an oil cooler on there, the oil at times got considably hotter then the coolant temp, which gave me the idea of a cooler. There fairly cheap, and easy to install also.

[Phred]

Zvoiture:

Too many questions, not enough answers.

Guessing is as bad as taking things for granted. Lets assume the SU is good, and the gauge is good. For now. That means the engine is really producing less pressure when certain conditions exist. Why? Oil pressure relief valve not functioning properly? possibly, not likely. Which gets us back to thin oil. If this is the culprit, this may explain why.. General info on tests I performed on an engine dyno using both a 1600 & 2000cc formula ford engines. The tests were performed to evaluate the differences between petroleum vs. synthetic oils. Oil pressure, oil temp, horsepower, and torque, were the main focal points. Brefly, the results showed: At 180 degrees water, 160 degrees oil, the synthetic showed 2 to 3 more horsepower than petroleum. it also indicated 3 to 5 lbs. less oil pressure. (synthetic is thinner than a similar petroleum, producing less resistance within the pump). At 200 degrees water, 200 degrees oil, Horsepower figures were the same. Why? because the petrolium oil thinned, and presented the same internal friction coefficient. At 200 degrees water, from 200 to 220 degrees oil, both oils produced basically the same power. However, at 200 degrees water, starting at 225 degrees oil, the petroleum oil started to show a power loss and a drop in oil pressure. Power loss was notable at 240 degrees. Due to an increase in internal friction. ( the oil was starting to break down.) The synthetic oil did not cause a loss of power.

My point being, pressure is directly related to temp. And is directly related to RPM. More RPM, More H-P, More heat. I drove a six hour enduro once, where we had excess oil temp. by dropping the shift point 250 RPM, oil temp was reduced nearly 10 degrees.

An oil temp gauge is the only way to know for sure. Good luck.

Phred

[Zvoiture]

All right! Thanks Fred....So what synthetic 40 wt should I get?

steve77

[Phred]

Steve,

Your kind of between a rock, & a hard place. If you know your oil temps on the high side, Synthetic will protect your engine better than petroleum. However if your pressure is starting to drop when things get warm, it will continue to do so.

If I had to make a decision without any more info. This would be it.

I ran 20-50 racing Synthetic (any brand as long as its 100% Syn.)

in a turbo motor for eight years. But I live up here where it can be 20 degrees in the morning, and sixty in the afternoon. Its probably more moderate where you live, so you could get away with a straight 40 or 50 wt. I would also replace the oil pressure relief spring, with the Nissan Comp. spring(s). Or Shim up your current spring with a couple of AN washers. 2manyZs hit on the other factor. If your bottom end (rod & main brgs) have even a thousanth too much clr. (.003 instead .002), it will tend to "bleed" off oil when things get warm. This is noticed as a drop in oil press. It should'nt be harmfull, just bump up the pressure with the relief valve spring. If you have an accurate gauge, consider 40lbs. absolute min. when hot. 50lbs. preferred. With your eng. probably a little loose on the bottom end, you might end up seeing 70/75 psi when its cold, and 40/45psi when hot, and 50psi when everthings warm & fuzzy. OK, so syn. costs $4.00 a quart. Your eng. will thank you.

Phred

[Doehring]

Zvoiture,

90 mph for an hour is nothing for a Z engine in good condition. Here in Germany we still don't have a speed limit on the Autobahn.

At day times all german Autobahns are to crowded to drive high sppeds for a longer while, but at night there are some routes where you can go faster. 110mph is a cruising speed for cars like ours. You can also go up to your limits. That's where the Z32 Twin Turbos get their Turbo problems, not the Z31 Turbo, not the 280ZX Turbo and not na Zs.

I had a similar problem as you on my Z31 Turbo 2 times and it always was the gauge. I also heared that todays light syntetic oils are good for Turbos and todays engines whereas the former engines have been built with less fit. That's why I use in my 240 Castrol Classic. Did you check your compression rates ? I think it is the gauge that fools so many of us.

Rolf

[Zvoiture]

Yeah, if a car can't turn 4200 r's for an hour, then somethings wrong! I have a 5-sp and I really don't feel 90+ for an hour is working anything to the extreme.

It is very temperate here. Never get a frost and never goes above 90.

Even with the turbo oil pump--STILL shim it and bump up the relief spring?

On an older engine, would there be seal problems?

Stupid ?....Where is the relief? I'm guessing IN the pump?

steve77

[Phred]

Steve:

The relief valve is easy to get to. If you installed the pump your self, you had your hands on it. Its the big hex bolt head on the bottom side of the oil pump. Its either a 19mm or 7/8 in. hex. Its actually a cap plug with a spring and plunger behind it. A 1/4 in. AN washer fits perfectly in plunger. Any race shop or aviation supply has AN washers. They come in thin1/32) or thick(1/16) sizes. Mix & match till your happy with the pressure.

Phred

[Zvoiture]

Yes, I did the pump myself....Talk about easy. There are a few reasons you just can't beat a Z! WAYYY up there on the list of effort/result mods!

steve77