Hi,

 

As my engine is lying in bits I was thinking (dangerous combination).

 

The oil cooler works off a pressure operated valve over 47PSI and the oil cooler gets flow, below that none.

 

There are pros and cons to this system, the pressure valve is on the oil filter bracket, I took out the pressure valve's spring yesterday and this would leave the oil valve completely open.

I have found a source for oil cooler thermostats and have plans to convert the oil cooler feed to a temperature operated system.

 

Opinions would be gratefully received

 

Mark

if thats the case then its a very poor design. as the oil gets hotter, the pressure will drop due to the oil being thinner. so the oil cooler will be mostly used when the engine is cold!! hmmm

 

i suppose they wanted the flow through the cooler at higher engine speeds, but a thermostat is much better than a pressure spring for an oil cooler.

 

i know the mercs have a thermostat. it will allow the oil to get up to operating temp quicker - which is what you want in an engine.

Yep, IMHO a thermostatically controlled valve would be a better solution, these are so cheap these days.

 

Try: http://www.thinkauto.com/oilstats.htm

 

For ideas.

 

Tim

I am going to pop into Mocal this week and see how much they are, I think they are $25 in the states!

 

I have heard the reason why Nissan designed it this way is so that if there was a leak it wouldn't send all the oil out of the cooler!

 

My only concern is positioning the thermostat so that it gets enough hot oil to it to open it, or do they have some sort of toggle as in the Rad thermostat?

 

Mark

I thought it was with a thermostat too till someone here put me straight about the pressure valve. However I think it is OK this way as it is really at high rpm and high power output that you really need it and the Z runs with such a small oil quantity anyway - 4 litres. So it heats up fast whatever with 2 turbos and with slow traffic work the oil never gets near the cooler.

 

Maybe high speed and very cold weather means the oil would be overcooled a little but the water cooling is thermostatically controlled anyway and would in itself keep the oil warmed by compensating and reducing the degree of water cooling if over oil cooled - if you see what I mean.

 

Is there not a danger that the time delay with a thermostat could catch you out with run bearings and toasted turbo seals if you are in to heavy footed stuff and give it a 10/10ths roasting suddenly on a hot day after running hot but not hot enough to open the oil stat?

 

Willie

Hi Willie,

 

I live in London and do lots of stop start and short journeys,

I can be exercising my right foot a little and then be stuck in a jam for an hour. So having a thermostatically controlled oil cooler is slightly more desirable, it also satisfies my desire to tinker!

 

I have talked to people with eng oil temp gauges and upgraded coolers, in the winter the oil sometimes never rises above 75 degrees celsius which I believe is the minimum optimum operating temp for the oil!

 

I think the benefits for me would be a faster warm up of engine oil and continued cooling of the oil if stuck in traffic.

 

No I don't think blowing up the engine due to a blocked oil cooler is that much of realisitic probability.

 

Mark

Hi Mark

 

I agree that in theory a thermo valve is a better technical solution.

 

Also if a thermostatic valve fails does it fail wide open like a water one? Then you really would have over chilled oil.

 

Incidentally at what rpm would the normal pressure one open? My oil press gauge reads all over the place but in the summer I had to drive pretty enthusiastically on normal roads to get the engine oil cooler even warm. Maybe I have a lower running pressure due to 0-40 grade oil and some wear in the pump and bearings with age and mileage.

 

I thought about 47psi would equate to something like 2600-3000rpm hot. I know it is way past that at 1500rpm cold but it has to be hot that counts. Manual says 51-65 is normal at 3000rpm. When my gauge wants to it does sit around this range at this rpm

 

So you have to normally be at 80 plus in top or going up through the gears way past 3000rpm to be squirting some oil into the cooler. At this sort of duty there is likely to be no problem with oil temperature. I thought it became an issue at 120mph plus or in hard track use.

 

Would be interested to hear the results with your stat.

 

Maybe theres even a case for covering up the engine oil cooler in winter if you drive gently?

 

Fellow tinkerer - but also learned if it aint broke then dont fix it!

 

Willie

Hi Willie,

 

"If it ain't broke don't fix it", maybe we can translate it into Latin and have it as the Forum Motto, LOL;)

 

There are no perfect solutions to this just personal opinions, I have consulted two proffessional mechanics over this and they both agree it is a better system.

 

Oil needs cooling if it is too hot, the current system does not operate on this criteria.

 

The problem you have with your oil 0-40 is that it operates at a lower pressure due to its viscosity, so the engine has to run at higher revs to run oil through the cooler. It is hard to say at what point the oil cooler valve opens on each engine, because their are too many variables, temp and viscosity,wear, pressure spring in the oil pump!

 

Also for your information, UK Z's have Nismo uprated oil coolers, imports have very small standard oil coolers.

 

To judge your oil's temp by touching it with your hand is very inaccurate because you would have to race the car and then come to an immediate stop, because the slow down over whatever distance would cool the oil within the cooler.

 

To not do something because of it's potential for failure is not my style, as my own personal Motto demonstrates

 

"If at first you don't succeed, hide all evidence of trying"

 

LOL

 

Mark

Originally posted by TopLess

"If it ain't broke don't fix it", maybe we can translate it into Latin and have it as the Forum Motto, LOL;)

Cam belt ?:D ;)

Originally posted by TopLess

Hi Willie,

 

"If it ain't broke don't fix it", maybe we can translate it into Latin and have it as the Forum Motto, LOL;)

 

.

.

.

 

 

Si fractum non sit, noli id reficere !

Just to add my 2p.

 

Bear in mind that there will be a pressure drop across the cooler & pipework.

 

When your oil is 90C and you're idling, the pressure is pretty low.. Hopefully not so low that the drop across the cooler makes it zero!

 

Other than that, I think a stat controlled cooler is a much better idea than a pressure controlled cooler, especially if you plan on doing any trackdays.

 

IMHO.

Thanks Guys,

 

Aaron the return feed for the cooler goes into the sump so that eliminates the returning oil being too cold.

 

Had a result today visited Mocal to see the thermostats and they their ZX uprated oil cooler in the flog off cheap bin for 40 squid, WooHoo!

 

Asked about their thermostats, they all open up at 82 celsius, they fail in the closed position and return the oil to the sump!

 

Mark

Sounds ideal then - presumably their oilstat is a sandwich plate type one, that goes between the oil filter bracket and the oil filter, so you actually block off the stock oil cooler lines entirely, or is it an inline one (so remove the spring from the stock bracket, and then fit the cooler inline to the output oil line)?

Hi Aaron,

 

They sell either type, but I wasn't sure if the added thickness of the sandwich plate might make the oil filter interfere with some of other mechanical item in our oh, so spacious engine bay!

 

Plus the sandwich type could return cold oil to the engine as mentioned by yourself in the previous post. So I am taking out of the spring and installing an inline thermostat!

 

Mark

I think the only thing it'd end up potentially interfering with would be the road - it's quite low down afterall.. :)

 

And it wasn't so much returning cold oil that I was worried about - it was if the oil was hot enough to open the stat, and you were at idle with bugger all oil pressure - if the oil cooler was the first thing in the system, you might end up with zero oil pressure - not handy..

 

But as it must be the last thing in the system, if it returns to the sump, that shouldn't be an issue, I don't think..

UUUUUMMmmmmmm,

 

You might have put a foil in my plan Aaron!!

 

I am not sure that the feed is on the return, I will have to study a bit more.

 

If the thermostat closes it bypasses the cooler it feeds the oil straight to the sump.

 

If I take the spring out completely does this mean the valve may open too much and send too much oil to the cooler then the sump and less to the engine?

 

After looking at the oil flow chart this is indeed the case and Aaron you win tonights prize, you get to buy me a pint LOL!

 

The only option is to use a sandwich plate with a built in thermostat, which then sends the oil all through the engine.

 

Bit of a serious design query from Nissan though!

It means when the engine is cold or at higher revs some of the oil is sent on a permaneant loop and not sent to circulate around the engine when it needs it the most?

 

Or did the they do this on purpose to stop too much oil pressure at higher revs? If this is the case my option could be to just install a piece of hose directly between the pressure valve and the where the original cooler enters the sump?

 

 

Mark

Mark

 

This subject had me scratching my bonce again. Bearing in mind that the bearings must get oil under pressure first and always you cant simply have an oilstat divert oil to the cooler or the pressure will collapse when it opens. If you put the pressure divert back in then you need both pressure and temperature to be above the set levels to get oil to the cooler. The only other possibility is some kind of restrictor to restrict the oil flow through the cooler. You get back to a spring loaded pressure regulating compromise oil stat. I suppose if it only cracks open a little then the pressure would stay up but right after a 10/10ths run your oil pressure could collapse if it opened right up.

 

Doesnt it come back to the fact that the oil pump tries to deliver oil by volume directly proportonal to rpm. The bearings need a minimum pressure related to rpm to feed them, to spray oil under pistons, feed turbos, feed hydraulic cam followers, variable timing etc but not burst seals. So you have to have pressure relief anyway above a certain pressure to bleed off some unwanted oil to ease pressure rise on seals.

 

It makes sense that the max heat comes at higher rpm and big bhp outputs anyway. This is also where the pump has excess capacity and can easily maintain pressure, oil flow as fast as the engine can take it and also bleed some via the cooler to cool it. It means to me that the standard arrangement is correct. You just dont need oil cooling at low rpm. If your engine or oil pump was so worn it couldnt get enough pressure to divert some oil through the cooler at high rom then its over anyway.

 

I think that this argument about thicker oils can also be false security. I used to be always worried about oil pressure on other sports cars I owned and sure using thicker oil can give higher running pressure but the flow and cooling effect in litres of oil per minute reduces with thicker oil - more goes past the pressure relief valve. If Nissan say a 40 weight oil is right for this engine in this climate then I am happy to stick with my full synthetic 0-40 weight. I'd rather have thin oil doing its job spraying on the underside of pistons and lubing the bores in this cold weather than thick oil not even spraying even if my oil pressure guage was reassuring me all was well. A lot of oil at the extra pressure is bled past the relief valve anyway and not through the engine.

 

Just my 2p

 

Willie

Hi,

 

 

I don't believe the oil stat is a split second open and shut valve and I believe it gradually opens still allowing oil to the engine, when it flows the oil cooler is already full of oil anyway!

 

I have decided not to use the inline thermostat using the current pressure valve feed, because it might cause to greater pressure drop in the engine. I have opted for a sandwich plate feed with a built in thermostat.

 

I will put in a continuous hose, taking out the cooler, just in case the oil cooler pressure valve is a suplementary pressure release, to the one built into the oil pump.

What I might plan to do is take readings from someone with an accurate oil pressure meter then block off my the original oil cooler feed and see if the pressure raises too high!

 

When I say the problem with 0-40 oil is, I am only talking with regard to the pressure regulated feed, not with using the oil itself.

 

I am also wondering if the problem that some people have had with bottom end oil starvation, could possibly be linked to weak oil pump relief and oil cooler springs, which would cause the oil just to get pumped back to the sump and not to the engine!

Quote

 

 

"I am also wondering if the problem that some people have had with bottom end oil starvation, could possibly be linked to weak oil pump relief and oil cooler springs, which would cause the oil just to get pumped back to the sump and not to the engine!"

 

Unquote

 

I took a relief valve apart on one of my previous cars when I suspected it was causing low oil pressure. It was a bit scored but the spring was fine. A new valve made no difference. On that car a new oil pump sorted the problem. I dont think much goes wrong with springs and relief valves.

 

I wondered if the starvation issue is like the track use cavitation problem which encourages dry sump lubrication for race engines.

 

A "V" engine is also susceptible on curves where hi g's (.9 +) are pulled say on a long sweeping bend. The outermost cyclinder bank will tend to well up oil in the camshaft area as the g force impedes its progress back to the sump. The oil in the sump will then be lower than normal and at the same time be at almost a 45 deg angle. The risk then is that the strainer pipe sucks air for a few seconds and bang go your big end bearings.

 

Didnt someone here suffer bearing problems after a track day?

Originally posted by WillieO

A "V" engine is also susceptible on curves where hi g's (.9 +) are pulled say on a long sweeping bend. The outermost cyclinder bank will tend to well up oil in the camshaft area as the g force impedes its progress back to the sump. The oil in the sump will then be lower than normal and at the same time be at almost a 45 deg angle. The risk then is that the strainer pipe sucks air for a few seconds and bang go your big end bearings.

 

I seem to remember reading about that being a problem for people who did a lot of autocross driving in the states - though I'm sure someone (infinitely more knowledgeable than myself) said it wasn't a problem on the VG30DE engine (Eric Lymon, I think)

 

Originally posted by WillieO

Didnt someone here suffer bearing problems after a track day?

 

They did.. erm.. erm.. his name escapes me.. wild turkey, I believe.. That's the badger (or turkey, perhaps)

The mystery continues!

 

 

I will definately have a look at my oil pump now!

 

I must admit the lack of baffling in the sump would probably add to the cornering problem!

 

I have spoken to mocal regarding their sandwich plate thermostats, they are continously open to the cooler and engine. Since oil always takes the path of least resistance the vast majority goes to the engine. When the engine oil reaches 82 degrees it gradually closes the link to engine which then forces the oil through the cooler! I also asked about oil pressure at idle being enough to feed the oil cooler and they said that the low oil pressure at idle would feed the oil cooler without any problems!

 

All I need to know now is at what pressure the oil pump relief valve opens and if it is sufficient to dispense excessive oil pressure on its own?

 

Mark

I already had a discussion with Mark about this very interesting subject.

Personally I think Nissan have choosen to use a pressure operated valve for a good reason.

They have extensively tested these engines on testbenches and on tracks and they must have had a good reason not to go for a temperature operated valve.

 

So what about an external (electric) oilpump that pumps the oil from the sump through the cooler ?

You could even make this pump temperature/rpm operated if needed

I was thinking of using the electric gearboxpump that is on the UK/EURO-spec Zeds.

You'll have to create a tap in the sump to get the oil from and you can use the stock return line.

 

-Eric

Hi Eric,

 

Always glad to have your input!

 

I am sure Nissan did have a good reason to put in a pressure fed oil cooler.

 

One of the reasons I have heard is so if one of oil lines is compromised, then all of the oil won't be completely lost through the cooler.

 

Again this is only hearsay and it is difficult to know the real reasons without learning Japanese, flying to Tokyo and stalking the bloke who designed the engine LOL

 

Mark

Eric

 

The UK leccy differential oil pump might be good for this it is separate and small and has the thermostat as well. Maybe available from a breaker doing a UK car.

 

The leak issue is a worry. My UK car did leak diff oil from this very source. I only noticed it by chance as it had dripped onto an exhaust after a fast run. I think the oil pick up pipe is set not too deep in the diff so it cannot totally empty your oil in case of a pipe or cooler leak. Still it took a quite lot of oil to refill my diff up. An engine is not so tolerant of low oil.

Willie

Hi Eric,

 

Just wondered what temp the electric pump kicks in and would you connect the existing pressure fed oil cooler line to the oil return on this new set up?

 

Mark

Mark, in this setup it's probably best to block the existing oil feedline and have the electric pump do all the work.

You could still use the returnline though, since it goes straight to the sump

 

I don't know what temperature the diff-pump kicks in...I'll have to look it up

A small pressure sensor in the return line after the cooler and electric pump could warn you if something went wrong in case the pump fails or something starts to leak.

(Although in the current system you also run the risk to loose a lot of oil in case of a leaking oilcooler.)

You could also place the pick up pipe at a "safe" position, so it won't loose all oil in case of a severe leak.

 

Another advantage of an electric pump is that you can connect a timer to the pump (and electric airconfan), so the pump keeps running after the engine has been shut down...sort of like a turbo timer, but better IMHO

 

-Eric