Grassroots Idiot Lights

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?

I have given this thought. I, too, like idiot lights. The idiot light saved my Camry motor when it ran out of oil (oil pump O ring blew) 1 block from work. For my locost, I am planning on an idiot light for the oil. For the light, I am going to use a LED 18 wheeler trailer brake light mounted in the dash. I figger I should be able to see that. To trigger it, though, I am either going to have to plumb a low pressure switch into the oil feed line (4AGE 20V has a pressure sender, not a switch) or tap into the sender line. I think that I can work up a circuit to turn on the LED lights when the pressure sender is at one point or another. Maybe an op amp in some kind of voltage comparator circuit or something. The circuit shouldn't be too hard to come up with. That's where I'm heading anyway.

seems like all the sensors are variable resistors... if you know the calibration you could set a light to come on at whatever the value is set to... or a buzzer... or whatever...

i've been thinking of similar things on my volvo powered s10

I just bought gauges with programmable warnings. I have autometer elite series gauges, the dial faces turn from white to red (that's what mine are, you have the choice of 7 colours) when over or under a specified pressure/temp. There is also a second warn function where the gauges will flash red to really let you know to pay attention.

http://www.pegasusautoracing.com/productdetails.asp?RecID=1855

Pressure and temp. switches:

http://www.pegasusautoracing.com/group.asp?GroupID=PROLITE

We are running an adjustable oil pressure switch and a BIG light for the driver, small light for the "data acquistition system" (video camera).

Last track day I learned hard braking drops pressure. How much??? consult the "data acquistition system" to see the light come on at 40lbs but read the gauge and know that it never dropped below 30psi.

Accusump time.

Longacre Racing makes several kits for low oil pressure, water temp, etc. They come with light, sender and I think wiring. I would prefer an LED to a bulb as they are a bit more vibration and bump resistant. Warning light does little good if the bulb is burned out and you don't know.

For the low oil pressure, you can probably find something in a junkyard. For example, the 1995-05 Miatas have an oil pressure "gauge" that is really just an idiot light. The sender grounds out if there's less than 7 psi, perfect for a light. I run both a real gauge and an idiot light on my cars, so I can both monitor the system and get an instant "in your face!" warning of a problem like a holed oil pan. Different cars will likely have sensors with different trigger points. I'll bet NAPA has a big book of all the sensors including thread pitch and pressure level.

With the low oil pressure, it's easy to make sure the light is working. It'll come on with the ignition before you turn on the car. Because of that, I wouldn't recommend a buzzer.

Overboost should be obvious to the driver, but one solution is something called a "Turbo fuse" that turns your bypass/blowoff valve into a pop-off valve. Made by Turbosmart, you can get them from Flyin' Miata as well as other Turbosmart dealers. Of course, any good engine management setup will have overboost protection as well.

Over temp should be easy enough - get an adjustable fan trigger and set it to whatever your danger level is. If it'll turn on a fan, it'll turn on a light. Some experimentation may be required of course.

I use a truck clearance light with a standard 194 'wedge' base bulb for a charge indicator in the Jensenator.

Rotaries do NOT like overheating, if the belt comes off the WP and alt quit turning, the BIG RED LIGHT quickly comes on and the dummy driving can't possibly ignore that. He kills the engine, thus saving it for another run. I used an LED at first but it turns out the LED finds enough voltage to be lit even when the alternator is charging normally. There's got to be a way around that, but that's a project for another day.

The oil pressure light would be very easy to wire.

Thanks for all the info folks. Longacre looks like an easy single-source solution. I still think a buzzer might be a good idea, even if it goes off for a little while when the car first starts.

Keith wrote: Overboost should be obvious to the driver

Did you read the part where I'm an idiot? :) WRX is my first boost car, I am quite sure the reason I missed the coolant temperature gauge is because I was watching the boost gauge, trying to learn when/how/where the boost came on, etc.

at least you are honest about ito

Watching NASCAR right now and they were showing and discussing the perfect solution. Gauges with obviously two set points. When it hit the first point the lighting in the gauge turned from white to red. When it hit the second point the red lighting started flashing.

Probably very expensive but would certainly do the job. Think about an oil pressure gauge that turned red at ~20psi and started flashing at ~5psi.

Hal wrote: Watching NASCAR right now and they were showing and discussing the perfect solution. Gauges with obviously two set points. When it hit the first point the lighting in the gauge turned from white to red. When it hit the second point the red lighting started flashing. Probably very expensive but would certainly do the job. Think about an oil pressure gauge that turned red at ~20psi and started flashing at ~5psi.

Run_Away mentioned those - the Autometer Elite series. At nearly $200/gauge, a bit rich for my blood right now. Great idea though.

go to NAPA and have the guy pull out the Echelin electical catalog.. find the pressure and temp light switches that fit the threads of the holes you need to put them into and have the proper temp/pressure settings.. stop at Radio Shack and pick up some LEDs for the switches you bought at NAPA to light up.

if you'd rather look things up at home- the catalog can be seen online here:

http://www.napaechlin.com/upload/NAPAEchlin2/Documents/ECH_NA141_HQr.pdf

i bought a switch from them for the electric fans in my 74 Monte Carlo- 215 on/205 off- it cost me $17 for the top of the line option..

As far as the low coolant level goes, most 90s VWs (all three of mine do, there's probably other marques that have them as well) have overflow tanks with a level sensor. There's a float in the tank hooked up to a electrical switch. Float drops to the fill mark, light comes on (and actually flashes, on my stock ones). Don't know what you'd have to do to get it to talk Subie, tho.

FC RX-7s have a simple one wire low coolant sender in the top of the radiator.

On my Miata, I added a small blinking LED (like the one that gets mounted to the dash to show that an alarm is armed) and an adjustable low pressure sender that I plumbed into a tee on the line for oil pressure gauge sender. It's small and not directly in my line of sight, but the fact that it's bright and blinks is enough to draw my eye to the gauge.

When the oil is hot and the car is at idle, the oil pressure falls just below the 20 psi threshold and the light blinks, so I added a switch to deactivate it for the street.

Forgive the crappy photo. The switch is visible to the right, near the glove box, but close enough to reach with a harness fastened.

Woody, you should do like Lotus did on the 910 motor. When the RPM's are below 2000, the oil pressure light is disabled. There's a relay that does it. No more oil warning light on at idle.

Dr. Hess wrote: Woody, you should do like Lotus did on the 910 motor. When the RPM's are below 2000, the oil pressure light is disabled. There's a relay that does it. No more oil warning light on at idle.

So...you're suggesting that I adopt an electrical solution that was employed by Lotus...

Prosport Premium series are affordable, and have warning lights.

Woody wrote:

Dr. Hess wrote: Woody, you should do like Lotus did on the 910 motor. When the RPM's are below 2000, the oil pressure light is disabled. There's a relay that does it. No more oil warning light on at idle.

So...you're suggesting that I adopt an electrical solution that was employed by *Lotus*...

My 907 idles at ~25 PSI when hot, runs 55-65 at 3K RPM on a hot day, 75-80 on a cold day. Why would Lotus see a need to disable the oil pressure warning light on the 910?

Curmudgeon wrote: My 907 idles at ~25 PSI when hot, runs 55-65 at 3K RPM on a hot day, 75-80 on a cold day. Why would Lotus see a need to disable the oil pressure warning light on the 910?

Because when it warms up, the light comes on at idle. Duh.

So the Esprit's oil pressure light comes on at 25 PSI? Wow.

Duh?

No, 910 motors don't waste HP with little BS things like oil pressure when you don't need it. Spec for minimum oil pressure hot at idle is 5 PSI. The RPM relay disconnects the oil light below 2K. I don't recall what pressure the light comes on at, but I'd guess that it's around 10. I know someone I could ask that would know off the top of his head if it is that important to you. Minimum spec for 3500 RPM (hot) is 35 PSI.

Naw, not important, just find it weird. Wonder how it feeds the turbo sufficiently.