Grassroots Idiot Lights

Turbos don't need a lot of oil, just a trickle. In fact, turbo feed lines need a restrictor in them or you will have way too much pressure and blow oil past the seals. And at idle, the turbo isn't spooled up either, so it's just barely turning over.

What cam pulleys does your 907 have? My 910 came with the smogged out pulleys. When I did my recent 9 month "routine maintenance" job of, ah, about half of everything, I changed out to "green dot" 104 MOP pulleys and it really did make a difference. I'm spooling up about 200 RPM sooner now and there's more low end punch. My wife even noticed it sitting in the co-pilot seat. I also "lost" the exhaust gas back pressure valve at the same time, so that may have helped some as well, but I think changing the pulleys to run the cams where they were designed to helped a whole bunch.

Mine has the 'square' tooth 110 pulleys. I believe those were 907 motor only pieces. Lots of the JH guys use the 104 pulleys and they say for a real 'seat of the pants' increase use those with the 107 cams. When I was putting my car together, I got a lot of stuff from Richard Appleyard Engineering. In one phone call, their shop manager told me they had converted an NA 907 to fuel injection and digital 3D map ignition, kept stock bore/stroke/compression, used that setup with the stock 907 exhaust header and a freeflow exhaust. They got dyno results of ~235 HP @ (IIRC) 6200 RPM. Compare that to the 146 @ 5600 from a stock motor. One of these days...

OK, flipping through the NAPA document that novaderrik linked, I've got a question for those of you whose brains aren't the size of a pea.

When the notes say: "T1–3 N/O C@1–9.5 Psi"

Does that mean the sensor is closed ONLY between 1 and 9.5 psi, or does that mean is is open at 0 psi and closes at anything above 1-9.5 psi?

WRX idle pressure is supposed to be 14psi @ 700rpm. I'm shooting for a circuit that closes at anything less than 10 psi. The above sensor would fit the bill if it goes open above 9.5 psi.

peter wrote: OK, flipping through the NAPA document that novaderrik linked, I've got a question for those of you whose brains aren't the size of a pea. When the notes say: "T1–3 N/O C@1–9.5 Psi" Does that mean the sensor is closed ONLY between 1 and 9.5 psi, or does that mean is is open at 0 psi and closes at anything above 1-9.5 psi? WRX idle pressure is supposed to be 14psi @ 700rpm. I'm shooting for a circuit that closes at anything less than 10 psi. The above sensor would fit the bill if it goes open above 9.5 psi.

'T1-3 N/O = 'Terminals 1 and 3 normally open'

'C@ 1-9.5 PSI' = Closed @ 1-9.5 PSI'

That means Terminals 1 and 3 make no connection when there is no pressure, but once the pressure is over 1-9.5 PSI there is a connection. I would venture to guess this is a 3 prong GM switch that lets the fuel pump run ONLY when there is oil pressure.

You didn't mention Terminal 2. That one is probably closed when there is no pressure, meaning that terminal can be used to trigger a warning light.

IMHO, 1 PSI is WAY too low to trigger a warning light in time to save a motor. I'd look for a single terminal switch that opens at 10-15 PSI. That means if the oil pressure drops below 10-15 PSI the light will come on.

I think we're getting open/closed mixed up here, but I think you answered my question - the action happens in the range 1-9.5psi and stays in that state above 9.5psi.

I agree with you that 1psi is far too low to save a motor. Something like 10-12psi would probably be good, as 14psi is "normal" idle behavior. Need some "wiggle" room there to minimize false positives.

Thanks!

I read that as normally open, but between 1 and 9.5 psi it's closed. In other words, it would be perfect for a warning light. At 9.5 psi or lower, the circuit closes and turns on the light. Above that, it's open. That's a good description of how the Miata one works, for example.

In reply to Keith:

I think we're in agreement. My issue with the Miata part is that it's freakishly large for what should be a simple on/off function. I'm hoping one of the alternatives is smaller. I've seen elegant solutions that involve some flexible braided tubing going from the tap to the sensor, but a smaller sensor that didn't need remote mounting would be awesome.

The difficult sensor to source seems to be the coolant level sensor. It's overkill, but if I'm going to do this thing, I'm going to over-engineer the hell out of it. Lots of these sensors seem to plug into a specific radiator or rely on plastic fittings that are obviously not meant to be part of the pressurized system.

I've found two, count them, two, large truck sensors that use NPT threads, but are nice and expensive. Argh!

Make sure you're looking at the Miata oil pressure switch, not the pressure sensor. The 1990-94 one is big, and it's a real pressure sensor. The 1995-05 unit is about the size of your typical knock sensor.

Not saying you should use the Miata parts, just saying that the 9.5 psi switch point is about what that unit uses. I think the Miata one is 7. In other words, it says "you now have engine trouble".

When you're looking at braided hoses, you're probably looking at mechanical gauges.

So Keith, you're saying just connect the 95+ switch to a light rather than the phony gauge? If so, that may be a better option than the adjustable (but only down to 20) sensor that I got from Pegasus. I could eliminate the kill switch for light.

Yup. It still comes on with the ignition before you start the car (it is closed below 7 psi), but that's not a big deal to me.

Cool. I think I may have two of them kicking around.

peter wrote: I am an idiot. Having recently overheated my WRX and cracked the heads, I obviously need a backup system to the conventional gauges, something that says "PAY ATTENTION". Hence, idiot lights. Preferably with a loud buzzer too. I'm thinking coolant over-temp, low oil pressure, and maybe over-boost. But also coolant-level-low (what killed my motor). For now these would go into the WRX, but in a year or so they'd be an integral part of my 818 kit. Anyone know of any pre-made solutions? Otherwise I was going to get all engineer-y and roll my own. This switch looks good for low oil pressure, but I've had less success finding a good over-temp switch. And I'm guessing that over-boost would have to rely on a sensor (instead of a switch) with a variable resistor to set the alert point. Anyone done this before, or have any thoughts/pointers?

since you are looking for a Grassroots solution, just take the hood off and wait for the flames,

Just a thought

A couple months ago I was also looking for a bright idiot light to go with my oil pressure guage. I wanted a LED for reliability and also low current draw. I found a light from Aqua signal a marine parts manufactuer designed for use in bait livewell tanks that is not only very bright but waterproof which was important because tye car it is going in ihas an open cockpit. The lights come in white, amber, blue and red. The red part number is 16415. The lights are on page 17 of the catalog

http://www.aquasignal.info/us/cms/files/content/series_interior_lights.pdf?id=

Because the 1 1/2" bezel is domed the light seems glow and is very bright. I paid about $10.00 ea on a site I found on the internet. Just thought I would pass the info along if anyone is still looking or interested.

While I am thinking about it, Pegasus has a 4PSI coolant pressure switch, it's NC below 4 PSI. Wire that puppy to a big light and a catastrophic coolant loss would be almost instantaneously recognized.