Also received and installed today was the Defi Oil Pressure Gauge:
If you've been following this thread, you'll know that I have the SMY ClusterMaker
Dual Gauge Pod. It is an amazing piece, but I have been running it with only one gauge (boost), and one gauge blank. I wasn't sure what my second gauge would be, but I eventually decided on oil pressure. There are a lot of useful gauges out there, but I thought the oil pressure seemed the most useful on a day to day basis. Other gauges like EGT and AFR that are good to monitor, but really matter most during tuning, and not as much once you're done. Oil temp also seems like a good option, but oil pressure will allow me to monitor pressure (obviously) as well as get an indication of oil temp indirectly, through pressure readings. Some people may disagree what the best second gauge should be, but this is what I chose, and I am happy with it.
When I was looking into oil pressure gauges my first concern was install. I initially planned on getting a sandwich adapter. Seemed like the easiest solution. But once I researched it more, easiest isn't always best (greater possibility of leaking), and it was also more expensive. After more research, and help from Kirill at RallySportDirect, I eventually confirmed that the Defi oil pressure sender has 1/8PT (metric) threads, just like the galley plug that the OEM oil pressure sensor uses (located under the alternator). And since the Defi unit is so small it would fit into the same spot as the OEM sensor. This meant I could simply remove the OEM oil pressure sensor, and install the Defi sender unit. No extra parts to buy (sandwich plate, thread adapter, relocation kit, etc).
To do the install you need to remove the alternator cover (1 bolt), and the alternator itself (2 bolts + 1 bolt connecting the power wire). Once the alternator is out of the way you can pull the wire off of the OEM oil pressure sensor. To remove the OEM sensor you will need a 24mm socket. I highly recommend using the socket instead of some other method. I attempted using a large, adjustable, open ended wrench for about 5 minutes, then went and bought a 24mm deep socket and a 10" extension for my 1/2" drive ratchet. With the socket and extension the OEM sensor literally took 5 seconds to unscrew. The Defi sender unit is larger on top, so you cannot use a socket. It is 17mm so I had the open ended wrench to fit. I put on a few wraps of teflon tape and tightened it down with the wrench. Took a while, but was not difficult.
Once the sender is in place, re-install the alternator and cover, and move on to wiring the gauge. I went through the same procedure as my boost gauge, so it was all pretty straightforward. I removed the fender liner on the driver's side and put the wire through the boot underneath. I didn't remove the wheel this time, and it was tighter work, but not an issue. Wired it up to the same fuses as the boost gauge and installed the gauge into the pod. I did pull off all of the driver's side trim (and the OEM gauge cluster) in order to get all the wires situated properly. It is not difficult to do, and makes things much easier to work with.
Once that was all done I reassembled the dash and turned on the car. The gauges both work perfectly. Oil pressure was around 100psi at idle (cold start). Dropped to just over 20psi at idle once the car was warm. Not quite sure of the pressure when cruising, but I think it was closer to 100psi, and maybe even more when in the high rpm range. Overall I am extremely happy with how the Defi gauges look in the SMY gauge pod. Spending the extra money on the Defi's was definitely worth it in my book. They look perfect, and function just as well. The response is instant, and very smooth. Installing the oil pressure gauge was not hard at all, and I definitely recommend using the galley plug that the OEM oil pressure sensor uses. If you're doing two gauges it would definitely save some time to do them both at once, and get them both through the firewall at the same time.