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Oil pressure on Z20 engine?


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#1 Spiff

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Posted 12 December 2017 - 10:27 AM

I'm installing an oil pressure gauge with a programmable low pressure warning on my Z20 So I'm just wondering what a typical oil pressure on these are and what I should set my low alarm threshold to...



#2 DanielC

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Posted 12 December 2017 - 11:02 AM

On a hot summer day, after being on the freeway for the last hour, at idle, 15 to 20 PSI is OK, as long as it goes up with RPM off idle.

 

General rule of thumb, 10 PSI per 1K RPM.

 

If your oil pressure gauge is plumbed correctly, the oil pressure should rise and fall with the tachometer reading,

 

There is a pressure relief valve in the oil pump, that limits the high oil pressure to 60 to 75? PSI.

 

See post 139 on this page.  http://community.rat...tsun-521/page-7



#3 racerx

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Posted 12 December 2017 - 11:34 AM

Fairly sure its similar to an L18, so at traffic light I'm at about 25 to 30, then as I speed along, it is usually 40 then about 60 on freeway.

#4 datzenmike

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Posted 12 December 2017 - 05:48 PM

Well I've found that just cranking the engine, if I let the key return to ON the oil light is out for a few seconds and then it comes on. So cranking speed is enough to make more than the oil pressure sender's threshold of 5-8 PSI.

 

The stock gauge is not an instant reading gauge, same as the gas gauge or it would constantly jump around from gas sloshing or going around corners. I don't care for this on an oil gauge but the factory does so that owners don't freak out about the readings jumping around. If low on oil and you hammer the brakes to a stop you can get the oil light to come on yet the gauge is still reading 40 PSI. If your new gauge reads quickly set for 15 or 20 or as high as you can get it without it coming on all the time. The last thing you want is to become used to it coming on. If you are hammering down the highway at 80 and it comes on you know you just passed 15 PSI and not 5-8 PSI. This might give you a second or two to slow down or get it out of gear.

 

 My tired old L20B had a hot idle pressure of 17 PSI. I put a high volume KA24 oil pump from a D21 on it and the same hot idle pressure jumped to 29 PSI. The top pressure remains the same but from idle to max is higher sooner. A D21 oil pump is a great safety net and a peace of mind.


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#5 Spiff

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Posted 13 December 2017 - 01:49 AM

The reason I'm putting this gauge in is because my oil pressure light takes a while to go off after I've started it, I found out recently that my pressure switch is leaking so that might have something to do with it. I assume this gauge(innovate mtx-d) is a lot more responsive than anything stock.

I also want to keep an eye on oil temp since I have a turbo to see if it needs any additonal cooling(probably not now but maybe in the summer).

The higher volume oil pump is definately on my to-do list for this engine! 



#6 datzenmike

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Posted 13 December 2017 - 06:23 AM

This is a regular oil pump. In the inlet hole yopu can only see the top of the pump rotor.
 
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This is the high volume pump. Note that the top of the rotor extend upwards and the edge is visible. LOOK FOR THIS and know what you are looking for.
 
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This is because the high volume rotors are 13% longer than the regular pumps. I measured them.

 

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More oil is moved with every turn so it replaces oil that bleeds past the bearings and jets faster. This allows the pressure to back up sooner at lower RPMs than a smaller pump. It would also reach maximum pressure sooner and at a lower RPM but as it's spring regulated it will still have the same maximum pressure. You can put washers under the relief pressure spring to raise the maximum pressure. Have a care though, this is basically a positive displacement hydraulic pump with the capability of hundreds of PSI. I did have a regulator jam on me once on my stock pump 521. It split the oil pump open.  

 

Car KAs with this pump.......... only the early S13 with the single cam KA24E has it.

Truck KAs with this pump....... all D21 Hardbody with KA24E and KA24DE engines.

 

Yes the 280sx turbo automatic has a high volume pump also but they are not the same part number nor are the internal parts, so as I haven't had one apart I don't know if the same... these may be larger? I have had these pumps on all my L20B and Z24 engines. I just pull them off KA's in the wrecking yards.

 

If buying from a store LOOK at them and confirm the rotor size!!!!!! Know what you are looking for and buying.


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#7 Stoffregen Motorsports

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Posted 13 December 2017 - 09:02 AM

The reason I'm putting this gauge in is because my oil pressure light takes a while to go off after I've started it, I found out recently that my pressure switch is leaking so that might have something to do with it. I assume this gauge(innovate mtx-d) is a lot more responsive than anything stock.

I also want to keep an eye on oil temp since I have a turbo to see if it needs any additonal cooling(probably not now but maybe in the summer).

The higher volume oil pump is definately on my to-do list for this engine! 

Whenever I'm trying to diagnose an oil pressure issue, I hook up a mechanical gauge directly to the block (with an adapter fitting and a -3AN hose) and compare that against the dash gauge reading. If the pressure on the mechanical gauge reads different, that will help you rule out the sender and/or the stock gauge.



#8 kelowg

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Posted 13 December 2017 - 07:56 PM

Careful, sender threads in block r british pipe thread. Diff from all aftermarket guages/kits. Auto mter sells adpater



#9 datzenmike

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Posted 13 December 2017 - 08:04 PM

A low pressure warning is great. For all others, get an adapter that allows you to keep the original sender. Oil pressure gauges are great but you can't watch them all the time. Always good to have the red warning light too. The 720 has a gauge and the red light.


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#10 Spiff

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Posted 14 December 2017 - 12:21 AM

I don't have factory gauges on my 720.
I'm using a sandwich plate between the oil filter and block since the stock oil switch location is used for turbo oil feed.
You can get a 1/8 bspt "T" with a 1/8npt for aftermarket senders on eBay, that's where I bought mine.

#11 distributorguy

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Posted 14 December 2017 - 07:44 AM

Its normal to not see oil pressure at the gauge port for a few seconds after cold startup - even with the high volume pump.  

I'd go with 5 psi for a warning light.  Installing a 5 psi ignition cut-out may result in an engine that needs to crank a while before starting.  

 

I tap the block for 1/8 pipe thread during the rebuild.  Much easier to adapt to aftermarket gauges and lines.  



#12 datzenmike

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Posted 14 December 2017 - 02:51 PM

My thoughts are that if running a 5PSI warning light it could be running at 7PSI, which I wouldn't care do do, but the warning light out assures you that everything is OK.


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#13 Spiff

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Posted 14 December 2017 - 03:20 PM

I think I'll just connect it and see where I'm at and then set the warning a little under what it's normally running



#14 distributorguy

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Posted 15 December 2017 - 11:32 AM

Mike, the warning light just gives you time to shut the motor down before you lose a rod through the block.  How many motors run at 7 psi???  None.  You either run out of oil pressure or you have oil pressure.  Who cares if its 5 psi or 10 psi or 15 psi?  Either way, its essentially the same margin of safety.  If you're going 60 mph when you lose oil pressure, we're talking semantics.  



#15 G-Duax

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Posted 15 December 2017 - 11:45 AM

I run a 40psi switch on my Toyota, and a large red light to let me know something isn't right.

My hot running pressure is 80 psi on both it, and my 620.



#16 datzenmike

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Posted 15 December 2017 - 12:09 PM

Because a warning at 15 PSI comes on sooner than at 5, that's why.


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#17 distributorguy

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Posted 15 December 2017 - 01:05 PM

LOL yep 10 psi will buy you a 1/4 second or so.  Who cares?  The real point is to get off load when the light comes on and shut down ASAP.  On a street car you have a LOT more time than a race car.  

 

We peak at 85 psi on the race motor- 45 to 55 at idle (don't honestly remember).  I've read too many folks damaging oil pump gears running 100+ at speed.  I don't run an oil warning light.  It might scare the driver away from setting a record.   :thumbup:   

I'd rather spend the extra money on coated bearings and pistons and better oil to prevent damage than a 1/2 second dummy light.  



#18 Spiff

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Posted 30 December 2017 - 12:17 PM

So now the gauge is installed and today I got it warmed up and then proceeded to give it a good thrashing up the mountain.
Oil temp ended up at about 100 degrees Celsius at the most, so nothing to worry about for now, will probably get higher come summer. The pressure however...
At idle(700rpm) oil pressure was about 0.3-0.5bar(4-7psi). I think that's low?
At 2000rpm it was 2.8 though (40psi) and at 3k rpm it was 3.8 (55psi)
The service manual says 47-67 psi at 3000rpm and 10.7 at idle. So it's a little bit low at idle but within spec at speed.
Also when returning to a more sane driving mode oil temps where around 60-80 degrees C and pressures a bit higher with idle pressure at about 1 bar(14.7psi)

#19 banzai510(hainz)

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Posted 30 December 2017 - 12:23 PM

 run 15-40 oil see if that helps and increase idle abit.

try a different oil filter.

 

I think your fine. Mine goes low also with 10-30 and low idle.


Throw on some Weber sidedrafts, Rising Sun hood.... call it good

#20 datzenmike

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Posted 30 December 2017 - 12:52 PM

Turbo may have pounded the bearing clearance wider and why the idle oil pressure is 4-7 PSI. A KA pump will definitely raise that but if this low probably not up to 30.


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