One thing I've learned while putting together all the wierd systems on my car is, first, try to imagine all possible scenarios with the new system. If you can think of a circumstance with a system that could happen, no matter how remote, treat it as though it will happen and ask yourself, do I want this to happen? If the answer is no, change the system.
Low oil pressure cut-off switch
- Thread starter gnxtc2
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One thing I've learned while putting together all the wierd systems on my car is, first, try to imagine all possible scenarios with the new system. If you can think of a circumstance with a system that could happen, no matter how remote, treat it as though it will happen and ask yourself, do I want this to happen? If the answer is no, change the system.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
- Messages
- 5,802
Put a 7-10# hobbs switch in line on your power supply to the ignition box on a distributor car. Once you crank the car over for a couple seconds, it will build pressure and supply power to the ignition box. If you ever loose oil pressure, it will kill the power to the ignition system.
Todd (Black Sheep) set this system up on his car and it works. We unwillingly tested it at BG last year. He was making a pass, just as he launched the drive mandrel for his external pump came out of the crank. He was about to make a 1320 foot pass with no oil psi. Just as I heard the car shut off, the pulley rolled out from under the car. The cause was the bolt Peterson had supplied was not long enough to get enough thread engagement. After 3 passes or so it became loose enough to come out of the crank.
Todd (Black Sheep) set this system up on his car and it works. We unwillingly tested it at BG last year. He was making a pass, just as he launched the drive mandrel for his external pump came out of the crank. He was about to make a 1320 foot pass with no oil psi. Just as I heard the car shut off, the pulley rolled out from under the car. The cause was the bolt Peterson had supplied was not long enough to get enough thread engagement. After 3 passes or so it became loose enough to come out of the crank.
No......the motor will not re-start unless you crank it, it's not a manual trans.
That's why I tapped into the brake circuit due to the oil pressure falling when I'm on the brakes hard/pulling the chute at the end of the run. By applying the brakes at the end of the run, the pressure switch is bypassed. I also run a manual master cylinder.
Billy T.
gnxtc2@aol.com
Correct me if I'm wrong. I admit I've never tried this, but if you're on the freeway with an automatic transmission car and the engine dies, will the drivetrain keep the engine rpm up until the car coasts to a slow enough speed where engine friction will be greater than the hydraulic drive through the torque converter and finally wind to a stop? Assuming the transmission was never kicked into neutral after the engine died.
No, once the engine shut down, you are coasting. No drag on the motor.
On the older cars (50-60s) that had front and rear pumps in the automatic transmission,you could push the car to start the engine.
If the car was moving (20 to 30 mph) and you put the transmission in gear it would slow down the car. If the key was on it would restart the engine.
Gary
On the older cars (50-60s) that had front and rear pumps in the automatic transmission,you could push the car to start the engine.
If the car was moving (20 to 30 mph) and you put the transmission in gear it would slow down the car. If the key was on it would restart the engine.
Gary
Think of this, though. The car is moving at 140 mph in high gear (typical 3 speed automatic transmission). The engine is running and pressure has already been established in the transmission. As long as the engine continues to turn (whether fired up or not) the front pump will generate fluid pressure that can be used to hold clutches.
In this case, you're running a 3 speed automatic in third gear. Overrunning is not possible, as it would be with a 200-4R in OD position.
The engine loses fuel, spark or both. Wouldn't you still have a level of engine braking? Even though the engine is shut down, engine braking would keep the engine turning, keep the front pump pumping and clutch packs holding direct range (3rd gear) until the vehicle mph and engine speed is low enough to see enough of a pressure drop to where the clutches lose hold on direct range.
Is there something I'm missing?
It's been awhile since I've blown a few engines, but I seem to remember the engine continuing to turn, making a bunch of racket with the broken rods and all, until the car had slowed to a very low speed. With a reverse shift pattern, you just can't throw the shifter into neutral in a situation like that.
In this case, you're running a 3 speed automatic in third gear. Overrunning is not possible, as it would be with a 200-4R in OD position.
The engine loses fuel, spark or both. Wouldn't you still have a level of engine braking? Even though the engine is shut down, engine braking would keep the engine turning, keep the front pump pumping and clutch packs holding direct range (3rd gear) until the vehicle mph and engine speed is low enough to see enough of a pressure drop to where the clutches lose hold on direct range.
Is there something I'm missing?
It's been awhile since I've blown a few engines, but I seem to remember the engine continuing to turn, making a bunch of racket with the broken rods and all, until the car had slowed to a very low speed. With a reverse shift pattern, you just can't throw the shifter into neutral in a situation like that.
UPDATE
The way I originally wired the pressure switch utilizing the XFI ign wire (B17), I would need to add an additional over ride switch so I can program the XFI unit via laptop when the motor wasn't running. With the switch in the open position (no pressure) there is no power going to the XFI unit with the key ON. I would have to keep the brake pedal depressed-----> no good. To many wiring issues that can develop.
I switched to the ign wire on my ignition box like Dusty stated. I tested the shut down and the fuel pump shuts off also (no hydrolock issue).
Oh yea, I didn't mention it in the original post that you need to add a diode to brake over ride wire so the brake lights don't stay on when the pressure switch closes. I tied into the blue/w black stripe wire (3rd brake light) on the brake switch.
Billy T.
gnxtc2@aol.com
If anyone is wondering how you would test this theory out with a 200-4R, make sure the shifter is in the manual 3 position. With a 200-4R engine braking occurs in manual 3, 2 and 1.
Which would confirm my suspicion in post # 20..... the brake switch... IMHO.... isn't the place for a bypass.....
Maybe if you wanted to be sneaky..... a microswitch on the emergency brake pedal......could tie that into a sneaky theft deterrent also?
GNBRETT
Pelennor Fields
- Joined
- Feb 8, 2004
- Messages
- 15,860
Nice work Billy. You need a few more braided lines in there....
