Bad oil pressure gauge or sender?

[boca rat]

The CTSC car has run with about 4 bar under load, 1 bar at idle since I got it. While the car was at Mase for a tune we discussed the age of the engine (145k, 20k or so with the CTSC) and they thought that adding an aftermarket oil pressure sender would be a wise move to get the true 'health' of the engine, feeding into the AEM v1. Plan is to feed that output into a Gaugeart display...still...but I digress.

So that work was done and Mase told me the stock gauge was reading under by X% (can't remember exactly now but I think 15% or so), Good news.

Last week, car started and drove fine but then I noticed that the stock gauge seemed down by a bar, hovering around 0 bar at idle, 3 bar at load. And then after a a bit would revert back to 'normal' as described above.

As best I can tell using the AEM sender and parameters, the oil pressure stays constant at a given rpm regardless of whether the stock gauge is in 'normal' or 'low' mode.

Assuming this is correct and I don't have a real problem, based on experience what is the most likely culprit here? Stock sender unit, or the gauge itself?

Thanks!

 

[darock]

I have a similar issue. Dead cold it reads only 2 bar. Most of the time 4 and 1 like yours. Sometimes 6 and 1.5 (probably the real number.

i think it's the sending unit.

bernhard

 

[boca rat]

darock, mines a little different. Reads higher when cold, then eases down a little once warmed up, but then for a minute or two drops down another bar across the board, then comes back up again, repeat.

 

[boca rat]

Update - this got really flaky for a while so sprung for the SoS remote sender. Will get that installed and report back,

 

[NSX2398]

Update - this got really flaky for a while so sprung for the SoS remote sender. Will get that installed and report back,

Hate to burst your bubble but I had the same flakey problem .. installed the SOS remote sender .. and still have the same problem. Mine has about 190k miles on it. Only ever noticed it at idle when it's warm and it will occasionally sit at the 0 mark .. which originally concerned me so once when I had it into the dealer, I had them put a gauge on oil filter block and they said it was within spec. As you probably know, there is the oil pressure sender which connects to the rear head .. and then there's the oil pressure switch which is connected to the oil filter block and drives the low oil pressure idiot light. Not the best idea to trust the idiot light but it has never come on when the gauge is reading low. There's also no unusual valve noise which I've been told there would be if the pressure was really that low. So, it might be the gauge but I've been on the site for about 15 years and I don't ever recall anyone ever changing the gauge in the dash.

 

[boca rat]

Thx NSX2398, hopefully this will take care of it. Will post back with results.

 

[nsxspdfreak]

Oil pressure at the sending unit tap located on the back end of the front head will only read about 1 bar (14.2 psi) at an idle. It may even go lower depending on sender/gauge accuracy, oil viscosity and temps. It should reach 4-6 bars at higher RPMS. If your pressure was high at an idle it would probably be an indication of a plugged oil circuit. The pressure measured at that location is the residual pressure from oil that has already passed through the crankshaft so it's dependent on the tolerances across the crank journals. Tighter tolerances will result in a slightly lower pressure. If you take a reading at the port for the idiot light sender you'll see pressures at around 56-65psi at an idle and >100psi at higher RPM's. The SOS sender is more accurate and responds better than the oem unit, and due to it's placement it isn't susceptible to damage from a vibrating motor and high temps. Unless you're current oem unit is not accurate you won't see any difference in pressures.

- - - Updated - - -

I plan on installing aftermarket gauges for reading oil pressures at both locations.