Oil Pressure Gauge Fluctuation
 

Hello All,

So my car has been having a weird symptom after i did a 1.8 Swap and the FM2 kit.

When i hit boost my oil pressure climbs and climbs (could easliy max out the gauge if the symptom was not there). Once i hit 5200RPM in boost the oil pressure would drop to about 35psi then around 5500-5800RPM it would jump right back up.

I assumed this was a Knock issue from the research i did so i immediatly pulled timing. I ran the car again and got the same exact issue. So I tried the next pull in vaccum no boost and also resulted in the same issue.

Background
I live in CT and run 93 octane fuel.
Air fuel is in the mid to upper 11's for now in boost
My oil pressure sensor is run off a tee on the cold side block (stock pressure sensor location) shared with the oil feed line for my turbo
Engine is 1.8 JDM engine (no oil feel port on hot side block, hence me feeding my turbo Tee'd off the oil pressure sensor)

My timing map originally was the DIY tune base map that was downloaded but i pulled alot of timing to see if i could get the car to have a steady oil pressure ready through the RPM band but there was no luck .

Here is my current Ignition map. Very conservative, in my opinion i should not have any knock here running in the 11's for AFR

https://www.miataturbo.net/attachmen...ine=1431343035

knock makes the gauge go erratic. Sounds like you have some other issue.

your timing in boost is INCREDIBLY conservative.

Thanks Brain. The issue is the same whether i have more timing or the amount i have posted above. I pulled alot out just to see how it would respond but the issue persisted so i will more than likely go back to the original DIY Base map timing until i get it tuned.


I would just really want to figure out the issue before i tune the car for reallllll

Check your base timing.

Good Point. I Suspected that also, so i took off all the front covers and found the exhaust cam was off a tooth. I retimed it, drove the car and was getting the same issue. I double checked the timing yesterday to make sure it was still set correctly and it is good. (fix timing at 10 degrees in Ms and align the first mark on the crank pulley at 10, the second mark naturally lines up at TDC

Might want to recheck base timing with a timing light to make sure.

Is that megatune??

Yes that is only a copy of the map i was running as a precaution. I am actually on MSPNP2.
I will check my base timing again later today but i had just reset the timing the other day. I cant imagine that it would be off again already. But i will double check that reguardless .

Note: i did a pull in vaccum down a hill yesterday in 2nd gear and right about 5300rpm the oil pressure gauge did drop from about 65 to 45. The gear that i see this occuring the most with is 2nd gear. Maybe because it is the easiest one to get my revs up and still pay attention to everything carefully

Are you using the stock 1990 oil pressure sensor on the stock gauge?

I've had instances where the spade terminal of the pressure sensor is dirty or loose and causes dropped pressure readings for short periods of time (a couple seconds). It's usually not at a specific RPM as you describe, but possibly it's loose and occurring at a specific RPM frequency.

Thanks M.Adamovits i will check on that later also. I am also thinking of buying an aftermarket oil pressure gauge to see if i would get the same results as i am now. If i am getting the same results i know it would not be a connection issue and i know it wouldnt be knock (the 1990 sensor picks up knock buy frequency changed as i understand)

I have a mechanical oil pressure gauge you can have for shipping costs. Took it of Blaen99's car after he did the same thing, used it to verify actual oil pressure, then stated trusting the stock electrical gauge.

Thanks Curley I'll shoot you a pm about the gauge!

Also checked base timing again and it is still dead on. My connection to the sending unit is kind of loose but still making a connection.

Oil Pressure Gauge Fluctuation
 

Which in my case gave partially incorrect readings. Clean the spade and connector, and stiffen up the connector on the harness.

IIRC the 1.6 used a real gauge and the 1.8 used a "idiot light" gauge. Are you running the 1.6 sender or the 1.8 sender?

I will clean the spade and tighten up the connection on the harness. I did transfer over the 1.6 sending unit so it will read actual.

The first time I started my car after tapping the oil pan and installing my turbo kit the oil pressure gauge was pegged at 0 and would barely move. Of course I though I hit the pickup but I was fairly certain I didn't. Turns out I dropped the sender while everything was being installed. Bought an aem unit and never hooked the stock one back up. Did the same thing in my ram pick up. I think the rest of my vehicles in life will have real oil pressure gauges

I just wanted to update this in case anyone comes across it in the future. So FINALLY last night i got to installing my aftermarket oil pressure gauge. I bought an Autometer mechanical gauge and instead of using the stupid plastic tubing or copper tubing i had a Stainless braided line made at FluidDynamic which worked beautifully.

The gauge reads great all through the RPM range without any drop at ~5000RPM. Just to clearify, the movement that i was seeing was not a small FLutter on the stock oil pressure needle (which this smaller movemet seems to show knocking), My gauge would fall do about 25psi and jump around a little bit before returning to 50-60psi at WOT (this was only occuring around 5000RPM no matter if i was in vaccum or i was in boost.

Next thing to do is make a set of DET CANS just to cover my arse

'94 was the only year you could get a 1.8L and a real oil pressure gauge.