Fixing the dummy oil pressure gauge

[scsi]

Well I've decided I'd like to take on the oil pressure gauge project and I've learned a lot doing some research. If this is news to you, here's some good reading to get you started:

http://www.miata.net/garage/opg.html
http://www.miata.net/garage/opg2.html
http://www.miata.net/garage/opg2/Oil_Sender.htm
http://quadesl.com/miata_oil.html
http://www.miata.net/garage/opg2/index.html
http://www.mazda-speed.com/faq/opg/

right now i'm wondering about what pressure sender to use. they are recommending using a VDO product which seems to be popular among the articles, but the VDO unit is rather large and requires a thread adapter. im just wondering if anyone has used any other alternatives to the VDO sender. i like the idea that some senders have a warning contact, but none of the VDOs that people have used seem to have that. i wonder if a warning light could be spiced from the single lead as well..

[Agent☣Orange]

It's a good topic and it's great that you're taking it on here. Hopefully we'll see some good ideas from folks here rather than advertise for m.net.

[Dilly]

Off topic; But YellowYata..... that avatar is pure GOLD.

[NW Bill]

With apologies for posting yet another link to m.net, for those who do not want to undertake rewinding the coil in their OEM gauge, here is what may be the best alternative for having a working oil pressure gauge in an NB:

http://forum.miata.net/vb/showthread.php?t=484030

Since I have a spare OEM OPG I may still try the modifications to make it function correctly (which means rewinding the coil), but in the meantime will be taking this alternative, including the optional warning light in the gauge for low oil pressure. I just ordered the gauge mounting piece described in the thread (and made by one of the m.net members) for $37 shipped.

I will also be modifying the OEM coolant gauge to read accurately -- this is a much simpler fix than the OPG. A voltmeter and other missing gauges have been added via an Android smart phone I replaced with my current phone (so it no longer has a phone connection), the Torque application, and a Bluetooth OBD2 reader. Even with my aging eyes, I can have two gauges large enough to read on screen at one time, and multiple pages with different gauges.

I like gauges in my cars -- I hate dummy gauges.

Bill

[Pfunk]

If you take the OEM gauge and soak it in contact cleaner while it sits in an ultrasonic cleaning vat you remove the damping oil and the gauge, with a proper sender like the TDR unit uses, will function as a decent OPG. Not great, but decent, and is easy to do. I did that on my NB, though now I have the Speedhut gauge set.

[NW Bill]

Just curious -- what is the difference between "decent" and "great" OPG function?

My initial plan was just to swap in a pre-'95 OPG, until I read how difficult that is, and especially the comment from the guy who did the write-up that he didn't think it was worth the amount of work it took. My second plan was do what you did, which is why I bought a second cluster with gauges, so I could redo the OPG and coolant gauges and minimize the Miata downtime, but the more I read about some people not getting the response time to what it should be (residual grease?) and the non-linearity of the gauge (compressed at the upper end) I realized the rewind route for the OEM gauge is necessary for what I want (and then still have to get a new gauge face if I want numbers). Using the VDO gauge, I still haven't decided if I will stick with the ivory face (which is pretty similar, although the color may be slightly off from my white gauges) or transplant an OEM white OPG face (although that again means dealing with the no numbers issue).

When I bought the Miata I thought it was weird that the OPG didn't move -- I've had enough cars with OPGs to know how they should function.

Bill


If you take the OEM gauge and soak it in contact cleaner while it sits in an ultrasonic cleaning vat you remove the damping oil and the gauge, with a proper sender like the TDR unit uses, will function as a decent OPG. Not great, but decent, and is easy to do. I did that on my NB, though now I have the Speedhut gauge set.

[Pfunk]

Just what you listed: not getting the response time to what it should be (residual grease?) and the non-linearity of the gauge (compressed at the upper end). It functions well enough to show trends, and can better indicate current conditions but not the same as a fully functional gauge. Still, the effort level is much lower than for a rewind effort or making a VDO fit.

[NW Bill]

Doing the rewind is clearly the most difficult path (except, perhaps, fitting the pre-'95 gauge), but seems to have excellent results. But, frankly, the write-ups make it seem like a PITA, and there is still the problem of no numbers on the gauge. Using the VDO approach in the write-up by scottvs is easier, I expect about the same as the path you took, but more expensive (cost of adapter & cost of gauge; the sending unit is needed either way). The biggest drawbacks to it are that the gauge face is non-OEM (although very similar, and an OEM face can be used), the VDO ivory face is not an exact color match for the OEM white face (although, again, similar; the VDO black gauge seems to match the EOM black gauge nicely), and there are still some issues with getting the gauge back lighting to match OEM. When I bought the adapter from him, Scott sent me some additional backlighting approaches to try (other than what is in the write-up). Once racing season is over (when I contacted him he was at Laguna Seca racing his Miata) he intends to work out the backlighting issues.

Which Speedhut gauges did you get? How was the install? Any pictures?

Bill

[NW Bill]

Doing the rewind is clearly the most difficult path (except, perhaps, fitting the pre-'95 gauge), but seems to have excellent results. But, frankly, the write-ups make it seem like a PITA, and there is still the problem of no numbers on the gauge. Using the VDO approach in the write-up by scottvs is easier, I expect about the same as the path you took, but more expensive (cost of adapter & cost of gauge; the sending unit is needed either way). The biggest drawbacks to it are that the gauge face is non-OEM (although very similar, and an OEM face can be used), the VDO ivory face is not an exact color match for the OEM white face (although, again, similar; the VDO black gauge seems to match the EOM black gauge nicely), and there are still some issues with getting the gauge back lighting to match OEM. When I bought the adapter from him, Scott sent me some additional backlighting approaches to try (other than what is in the write-up). Once racing season is over (when I contacted him he was at Laguna Seca racing his Miata) he intends to work out the backlighting issues.

Which Speedhut gauges did you get? How was the install? Any pictures?

Bill

[Pfunk]

I had SH make me custom faces for their Revolution gauges: speedo, tach, fuel level, water temp, water pressure, oil temp, oil pressure, voltage, AFR. I have pictures on here somewhere, I think in the interior section in a thread about where to mount gauges. I had to make a custom dash pod face and center console panel to mount them.

[Pfunk]

Not sure if this link will work: http://mazdaroadster.net/showthread.php?5710-Where-to-mount-gauges&p=89944&viewfull=1#post89944

[NW Bill]

Nice job on the gauges and the pod/console! What four warning lights did you add?

Did you mod the fuel level sender so the liter numbers will be accurate? On my gauge (OEM), starting from "F", it seems each 1/4 tank mark actually refers to a smaller and smaller amount of gas, so it's pretty non-linear.

I'm debating whether I should replace the face of the OEM water temp gauge with one with numbers, once I have fixed the gauge so its accurate. I'm not tracking my Miata, and can have the Torque app display the actual temp, so I may just fix it (which is easy) and leave the face alone.

Bill

[Pfunk]

I have seatbelt, abs, side brake, and airbag lights; all the gauges have their own warning lights. Regarding the gauge for fuel level, you set empty and full on the gauge but I have yet to fill the tank at different points to see how accurate it is. I know what you mean about the OEM setup--at first it's as if you own a hyper-miler and the last 1/4 tank appears to used as if you were drag racing while towing a sumo wrestler in the passenger seat.

[chiefmg]

I'll have to do some searching to find where I put the info, but I seem to recall someone saying you could use the pressure sender off some Isuzu product that fits without an adapter and isn't as large as the VDO unit. This mod is on my list of things to do once I get the big ones done.

[NW Bill]

I'll have to do some searching to find where I put the info, but I seem to recall someone saying you could use the pressure sender off some Isuzu product that fits without an adapter and isn't as large as the VDO unit. This mod is on my list of things to do once I get the big ones done.

Take a look at post #22 in http://forum.miata.net/vb/showthread.php?t=484030; unfortunately, the poster does not include either the part # or the Isuzu truck model it is for, so you may have to check with him directly.

VDO also has/had a couple of appropriate BSP-thread senders: #360-080 (for the gauge only) and #360-082 (for the gauge and a 5.7psi warning light). While an internet search for these part numbers will show them in various marine parts catalogues and boating websites, they seem to be unavailable unless you happen on them NOS. In any case, the list price on them was about double the cost of the VDO senders needing the adapters (and the adapters ranges in cost from about $3 to about $15, depending where you get it and whether it is brass or stainless steel).

Bill

[chiefmg]

Here is the sender I had bookmarked: http://www.autopartswarehouse.com/shop_parts/oil_pressure_switch/isuzu/trooper.html I don't recall how I settled on that one, but it should be correct as I don't keep links to things I can't use. Being on a ship my connection is painfully slow and it makes it difficult to do searches, if I come across what led me to it I'll post that. It is a bit pricey, I would see what Rock Auto sells them for.

[Pfunk]

Did you mod the fuel level sender so the liter numbers will be accurate?

Quick update: the SH gauge appears to be dead accurate. Today I filled the tank with the gauge reading just under the tick between 12 and 24, so I expected I'd need slightly more than 30 liters if it was accurate. I needed 31 liters. That said, the rate at which the needle drops isn't linear. If I were to estimate my kpl for the first quarter-tank to be used I would think I was getting 10km/l but once past the half-tank mark it's more like 8km/l. Because the gauge uses a 270º sweep, I swear I could almost see the gauge drop as I drove before I filled it. Still, the gauge accurately indicates how many liters remain at any time.