A question for the wiring experts.

[Weaselman]

I want to make a system where the fuel pump will be cut off when the oil pressure to the engine drops below a certain level.
I'd like it to be stand alone and have an override switch for cold starting with a warning light inside the car on a switch panel.
I guess I need a way to rob the signal off the oil pressure sender and a switch that can trigger at a certain OHM measurement.
I could wire it with a diagram but am unsure how to go about it.
So it would be:
Rocker switch override.
A light to show the override is armed
A light that flashes to show the pump is cut off
A blade fuse
Earth to chassis
Some kind of switch that would work at the correct OHM's
An advice on gauge of wire I'd need ect.
Thanks guys.

[slingy88]

Ok, not exactly what you asked for but a already had it drawn and saved so a starting point.
It does exactly what you want but in a different way i suppose.
So, the pump will only run when the oil light goes out (ie engine running) and will stop the pump when the engine stops, car crashes etc.
But, to make sure starting isnt an issue, it will also always run the pump while the engine is cranking on the starter, then once the motor catches and fire up, the oil pressure side kicks in and takes over keeping the pump running.
So no need for overide switches, temp senders etc.
It works really well and you dont have to listen to a pump running when ever you turn the key on etc.
The wiring colour codes are for GSXR so just go off descriptions.
Wire size... 1mm would be fine as pumps only draw around 5A from memory, but maybe 1.5mm for main supply and pump supply and earth as these will probably be the longest runs and may encur voltage drop, then 1mm for the relay and sender loops.
Sorry dont know what 1mm and 1.5mm are in gauge,but i am sure google does lol.

Anyway hopes that a start for yah.
cheers slingy

http://i557.photobucket.com/albums/ss11/slingy88/750%20slingshot/fuelpumpcircuitMedium.jpg (http://s557.photobucket.com/user/slingy88/media/750%20slingshot/fuelpumpcircuitMedium.jpg.html)

[Tony Nitrous]

I'm no sparky, but it makes sense what your trying to do.

We looked into a similar system where a pressures switch in the fuel feed
triggered the live feed to power the nitrous solenoid. No fuel pressure = no nitrous = safe.

[slingy88]

Oh and I would suggest that you get the relays and relay connectors from Jaycar or the like, as from what I have seen of it supercheap don't do relays with both the normally open and normally closed contacts. If you look in the packet they are the ones with 5 pins. You need at least one of these for the R2 in the above circuit. R1 can be a relay with 4 pins which will only have a normally open contact.
But generally I only buy the 5 pin type as more usefull.

[Weaselman]

Thanks a heap slingy. I might instal lights in line of the circuit to my engine panel just so I know its working for quick reference with a helmet on.
I'd still like however to be able to have the fuel cut before the oil pressure is to a point where the light triggers.
By the time the light would come on with how hard this engine runs it woud be toast. So I'd like to be able to set a pre determened cut out. Hence the need for an override switch.

[Weaselman]

I'm no sparky, but it makes sense what your trying to do.

We looked into a similar system where a pressures switch in the fuel feed
triggered the live feed to power the nitrous solenoid. No fuel pressure = no nitrous = safe.
I'm going it because I'm racing in a flying mile event so because the engine has to sustain high revs for a fairly long period at high boost I don't want to fry the the thing.

[slingy88]

Not a problem my good man ,glad to share.
But, i think i may of had the wrong end of the stick here. Normally people want a way to run a lecky pump without having it running all the time just off the ignition and so if you fall off a bike ,or crash the car or whatever its in the pump wont just keep pissing fuel out everywhere Goose in mad max styley.
But, you actually want to kill the pump if the oil pressure drops below a certain level to act as a motor kill to save the engine.
Is this the case?
Is it efi or carby? You say high boost, so are we talking turbo/supercharger. If carby, draw through or blow through?
What engine?
Sorry for all the questions, just trying to get a handle on what you want to best assist.

Cheers Slingy

[Weaselman]

It's an RB20DET with a pricision turbo.
22psi with a walbro pump and 750cc injectors.
Stand alone ECU too. No original engine controllers.

I think I'm going to use an Arduino micro controller and write a program with help. These little controllers come with banks or relays you can plug in and assign tasks with simple code.
I'll find out the ohm range for the sended and run the main pump power through the relay nd have a switch to short it across the relay as an override. I'll also rig up a flashing warning light to the controller to tell me if the pump is cut off.

You got it in one though slingy. It's to cut the engine BEFORE the pressure drops to the point that would toast the engine.
If I'm doing 200 and only notice it when the low oil light comes on chances are I've toasted the bearings already.

[slingy88]

It's an RB20DET with a pricision turbo.
22psi with a walbro pump and 750cc injectors.
Stand alone ECU too. No original engine controllers.

I think I'm going to use an Arduino micro controller and write a program with help. These little controllers come with banks or relays you can plug in and assign tasks with simple code.
I'll find out the ohm range for the sended and run the main pump power through the relay nd have a switch to short it across the relay as an override. I'll also rig up a flashing warning light to the controller to tell me if the pump is cut off.

You got it in one though slingy. It's to cut the engine BEFORE the pressure drops to the point that would toast the engine.
If I'm doing 200 and only notice it when the low oil light comes on chances are I've toasted the bearings already.

Right, good, good.
Ok, heres my thoughts.
On my bike, i have options in the ecu to opperate the rev limmiter. Spark Cut Only, Fuel Cut only or spark and fuel cut. I opted for Spark Cut only based on this theory.
When under boost, high revs, the worst case scenario is to go lean, even for a split second result in piston melting temps. So any form of fuel cut will replicate a lean scenario.
Where as Spark Cut, This leaves the fuel going but cuts spark events leaving unburnt fuel going through the chambers and resulting in a Rich scenario. Much safer in my book.
And this is with the fuel cut being the injectors actually being stopped from firing. If you do a fuel pump cut, the fuel rail will drop pressure over a number of engine cycles resulting in leaner and leaner running untill it stops.
If running full chat under load and peak boost, this could be melting time. Saved the bearings but melted the pistons.

Heres a supplier of simple adjustable pressure switches

http://www.gauge-shop.com.au/catalogue/14-products-by-brand/5-vdo/52-senders-switchestransducers-adapters/75-pressure-senders-a-switches/559-adjustable-pressure-switches-nonc

Does your ecu have any features or programable inputs that could be triggered by one of the above switches of a suitable pressure rating to do a spark cut and save the engine.

Or, use the above circuit i posted to run the coils rather the fuel pump. Most engines put the oil light out durring cranking so should transition from cranking to running ok anyway, or if needs be put a manual toggle switch as you suggested in parallel with the normally open contact of R1 to make sure you have a good spark for starting, then switch it off so the coil is being kept energised by the pressure switch for the run.
Be alot simpler than an Arduino, unless you just fancy playing with them lol

Anyway, just some thoughts. All sounds like good fun to me though
;)

[Weaselman]

I'm using an EMS stinger 4 in the motor. It doesn't really have the ability to do that, that I'm aware of. I could just use the controller to throw the relay on the coil side anyway without to much modding.
This would remove the need for me to play with the ECU in anything more than its job of running the engine. When I rebuild the engine I'll upgrade to a haltech anyway but yeah it doesn't provide for cutting ignition based on oil pressure values. I'd still need to run a voltage divider to convert the ohms to volts that the Arduino can read. The ECU cant read ohm's either so it's still easier to use a stand alone system.
I could also piggy back a sensor off the fuel pressure reg in case of a lean condition too I guess.

Edit: re jigged it slightly. It'll run off the low oil switch and cut the spark. It'll still have an override but I'm stripping out the old sender and using a mechanical one. RB's always have had problems with shit senders and I trust mechnical ones more.

[slingy88]

Ok, cool, sounds like you have it covered good luck. You'll have to let us know how you do

[DCRacing]

you could always go agricultural, we use watchdogs on the irrigation pumps, they have an adjustable gauge that will kill the motor if oil gets low or engine hot, or even lose prime in the pump. but not probably usable if looking for space