JaxFL_RX8

Please excuse my ignorance about this, but your answers would be appreciated.

Reading the manual, I noted "normal" oil pressure is represented by the Oil Pressure Guage needle resting at the mid-point. I read that having not enough oil results in needle showing "low" pressure. Does having too much oil result in having "high" oil pressure?

I ask because ever since getting my car (7/16), the needle rests 2.5 ticks past the mid-point line. I'm concerned this might be indicative of too much oil. If this is correct, would letting "a little" oil out result in Oil Pressure needle resting at mid-point?

Thanks Everyone.

eccles

Grossly overfilling the oil may lead to engine damage, but a little over won't hurt. But either way, the gauge won't tell you anything except you have "some" oil pressure.

You see Mazda, in their infinite wisdom, decided that a real oil pressure gauge would confuse us all by actually fluctuating as the oil pressure rises and falls, so they gave us the analog equivalent of an "idiot light" - a gauge that sits at one point on the scale whenever the engine has ANY oil pressure over a certain (low) threshold.

If that gauge ever moves, it will be to drop to zero, and you'd better shut the engine down immediately if that ever happens.

mikecarlton

I too would like to have a "real" oil pressure gauge -- but I'm not surprised.

My 93 Miata does have a real pressure gauge and the needle swings from 30 to 90 under various circumstances. This is a large percentage (at least 1/2) of the range.

At first it concerned me, but I investigated and found that it was normal and no cause for concern.

But I'm sure Mazda (dealers presumably) got a lot of phone calls asking about it... and so it isn't a surprise if they dumb it down for newer cars.

--Mike

JaxFL_RX8

I had an '88 RX7 convertible (NA) and the oil pressure gauge would fluctuate as well. I had no idea the RX8 gauge was basically an "on/off" kinda deal. What a waste.

DreamWarrior

If it makes you feel any better mine does the same thing, sits a bit above half.

My Z28 was a real gauge too, which was nice because I could tell once the oil was hot because the pressure would come down a bit as the viscosity changed.

Anyway, I hear there are ways to change the gauge to reflect what is really going on...anyone know how?

eccles

With the Miata gauge, it's a matter of replacing the sender switch with an analog sender unit, and repositioning the needle on the guage (which of course involves removing and partially disassembling the gauge cluster).

This may also be possible with the RX-8, but nobody has yet seen a schematic or seen the cluster out of the car. The gauge may be driven by the ECU, which would make it pretty much impossible.

DreamWarrior

Well I do not like the idiot gauge...I'd prefer to know what's going on...so when someone finds a way to rectify this with the RX-8 I'd love to be on the inside of the info circle :D.

edit: BTW, I'd like to thank you again for the first good pics I seen of the Winning Blue ages ago from your Rev-It-Up event in Houston. The color looks gorgeous and I'm happy I stuck with it!

eccles

Following up on that thought, I remember the Technical Highlights CD made much of the fact that most of the signals on the RX-8 wiring harness are multiplexed into some sort of bus architecture. If the OPG signal is one of these, the upgrade process is going to be somewhat more involved than the Miata's.

p.s. Glad the pics were helpful.

Sputnik

It's easier than it sounds. All you have to do to the gauge cluster is remove the hood, then the plastic "glazing". You don't even have to remove the cluster.

But like you said, whether it will be this easy on the RX8 or not has yet to be seen.

---jps

DreamWarrior

Well, I'd guess the sensor is still analog? If so we could parellel off it's signal and send it to a similar driver box and just disconnect the stock gauge wiring and reconnect the gauge to our new sender unit??

Otherwise I guess we'd have to install another oil pressure sensor and then do the same thing and fit a unit to send it to the gauge.

This doesn't seem that hard...besides, the gauge is just being sent a voltage to move...something needs to convert whatever signal is there (be it from a bus, or directly from the oil pressure gauge, or a signal from the ECU, or whatever) to a voltage that makes the needle move. Either you harness that reading, or disregard it and replace it with an analog voltage tuned to the sensitivity of the factory gauge.

Or am I just way off?? I REALLY WANT THIS...my dad's an EE, maybe I'll have him look at it and we can offer up a kit for you all...it seems like there's an interest in it. First I have to figure out how to get him to the gauge readings and then how to simulate the low oil pressure conditions though so we can figure out exactly what's going on.

wakeech

...have the ignition in the "on" position without starting the motor??

OverLOAD

I'm interested in this too.. However I can only speculate at what's going on until I see the back of the gauge cluster, and the connectors for the OPG.

From what I understand, Denso makes the majority of Instument Guage Clusters for many automotive companies. If someone with Denso contacts could see about getting the customer prints of the schematics for the cluster..

If the OPG does indeed act like an On/Off switch, I can almost guarantee that the ECU is reading the actual oil pressure, and converting it into a "user friendly" value that shows up on our wonderous OPG. My level seems to always be between 2 to 4 notches above the midpoint..

OverLOAD

dcfc3s

*sigh*. I wish I knew how many times I posted on this...

OIL PRESSURE IS NOT THAT BIG OF A DEAL ON A ROTARY.

Of the 15+ engines I've been through/rebuilt, NONE failed due to low oil pressure.

If you're worried about the oil *level*, the idiot light that kicks on when the oil level is too low is the deal.

What you guys SHOULD be worried about is the idiot light water temp gauge - THAT will get you in trouble. I've already e-mailed Mazda an exhaustive writeup about the water temp gauge being an idiot light - I firmly believe that's why many 3rd gen RX-7 motors failed prematurely. When that needle moves off the halfway mark, you're likely in motor meltdown territory. A water temp gauge will show you trends, like a thermostat that's getting close to failing, an obstructed air path, etc.

Dale

B-Nez

And incidentally, the gauge IS wired digitally into the ECU, as is the fan speed selector, and nearly everything else in the car. If you put the instruments into the diagnostic mode, you can sweep the needles through their ranges and also observe the values in the odometer display.

Edit: BTW, the sweep range for the OPG is from 0 to the point at which it normally rests.

Zoom2X

If you have a spare $1400 you can go this route (gauge pod /gauges 5th item down) :

http://www.corksport.com/main.php3?p...3Fcat%3D260826

Gauges all read in metric units though.

Smoker

Hi, from what I 've read on this forum, Oil Level and Oil Pressure are two completely different thing. I understand Oil Level is how much Oil you have available in your engine. But I don't really understand what Oil Pressure really indicates. What does it mean when it is up/down and what would it to go up or down ?

Thanks.

OverLOAD

for about $200, plus a laptop, you can read out all of the guages to a laptop, and record them, if you like..

http://www.autotap.com/

The ODBII connector in the RX-8 is below the steering wheel column (same location for many, many cars).

I'm stongly considering getting this, since it can tell you just about anything that the ECU knows.

OverLOAD

jdl

There doesn't seem to be any cross-references to Mazda vehicles. Seems like it could be a handy tool to have in your arsenal, particularly for this ability to read/reset diag codes. But which S/W package would you get for our RX8s?

syntrix

Especially since I tried 2 different obdii tools and they didn't work.

It's like 60% CAN and 40% ISO, which is a very weird combo. See the PCM Info / Scan Tool Update thread.

Zoom2X

The moving parts in a engine are seperated from touching by a film of oil, this oil film must be constantly replaced. The oil film is replaced by pumping the oil to where it is needed through a system of oil passages. A pump is used to create enough pressure to move the oil to the areas where it is needed. If the oil pressure is too low the oil film breaks down and the moving parts of the engine touch, this causes a GREAT deal of heat and if the low oil pressure conditon continues the engine will sieze up. In order to provide enough oil at low engine speeds but not have too much at high speeds most engines use one or more relief valves to control the oil pressure within the engine. A relief valve is a sping loaded piston that uncovers a bypass port which allows excess oil to return to the oil pan.

Oil pressure in a engine is controled by several varibles, these include:

Oil pump speed (which is controlled by engine speed)

Oil viscosity (grade of oil and it's temp.)

Conditon of the engine (seal and bearing wear)

Relief valve setting


Having oil pressure that is too low can cause the engine to rapidly fail (sieze up) that is why it is important to immediately pull over and stop the car if you get a low oil pressure warning. (some cars will disable the engine if a prolonged low oil pressure condtion is present).

Things that can cause low oil pressure include:

Low oil level (the oil pump is sucking air)

Incorrect oil viscoisty (wrong grade of oil) this can also occur because of contaminated oil, a water or fuel leak has occured which has flooded the oil pan and thined out the oil

Stuck open relief valve (sometimes caused by very dirty oil)

A massive oil leak (a seal or hose has just blown and allowing the oil to leak out)

A worn engine (the bearing clearances have worn to the point that the oil pump can't move enough oil)


Oil pressure that is too high is also a problem it can cause a hose or seal to fail. If this happens you will then get a low oil pressure warning.

Problems that can cause high oil pressure include:

Incorrect oil viscosity (wrong grade, oil is too thick)

A stuck closed relief valve

A very cold engine (the high pressure should go away as the engine and oil warm up)

Hope this answered your question

Smoker

Zoom2X,
just got around to see your post to my question. Thanks a lot for the detail explanation ~!!!