Installing FIA Battery Cutoff Switch

[Paul JA]

Hi

I'm installing an FIA battery cutoff switch into a Megane R26 Race Car. I have no issue with the main battery contact and the resistor install. I need an a way of stopping the engine because just cutting the battery will leave the engine running from the alternator. I'm looking for an easy ignition cut without delving deep into the awkward fuse box (if possible). I'm thinking of breaking into the ECU supply to pin M2 on the Sagem 3000 ECU.

Any other suggestions ?

 

[plugsandsparks]

Depends on the type of cut off your are using. There are the simple rotary type with the red key or there is the electronic type which has buttons.
If its the red key type , you can get aux contacts at the back of the switch and simply cut the supply to ecu, i cannot say what is the best way into the wiring of the Megane but if you have a simple wiring diagram then look for ECU supply or coil supply if fused separately. One way or another you have to get in there....
cheers
P&S

 

[UNG]

Does the car have a fuel solenoid or pump that could be isolated by the auxillary contact on the battery isolator

 

[Paul JA]

Depends on the type of cut off your are using. There are the simple rotary type with the red key or there is the electronic type which has buttons.
If its the red key type , you can get aux contacts at the back of the switch and simply cut the supply to ecu, i cannot say what is the best way into the wiring of the Megane but if you have a simple wiring diagram then look for ECU supply or coil supply if fused separately. One way or another you have to get in there....
cheers
P&S

Yeh it's the red rotary type with the main battery contacts and the 2 aux contacts.

I would like to cut the coil supply but it looks as if they are fired in pairs so there isn't one wire to cut. I'm struggling to find a decent R26 wiring diagram to assist.
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Does the car have a fuel solenoid or pump that could be isolated by the auxillary contact on the battery isolator

The car runs 2 pumps, one feeding a scavenge tank, the pump internal to the scavenge tank feeds the fuel rail. I could cut the relay that's been added in by the installer to cut this pump - that would be straight forward. I'll pull the fuse for the second pump and see how long it runs on for.

I would like to cut the ignition if possible so the engine cut is immediate.

 

[UNG]

Can you not put the auxiliary contact on the isolator in series with the the car ignition switch

 

[Strima]

Just use a switch with built in ignition isolation: FIA Approved Battery Isolator Switch - Removable Key & Ignition Isolation - https://www.12voltplanet.co.uk/battery-isolator-switch-removeable-key-with-ignition-isolation.html?gclid=CjwKCAjw-5v7BRAmEiwAJ3DpuArojpquefF2ZlzLWLFZrnCfC2-nY5JzF6K1h2MBxbjgFhuV7ixonBoCbt0QAvD_BwE

 

[plugsandsparks]

Its never as simple as that with these here modern cars... lol
Cutting fuel pump is not a great idea as car runs on and upside down may well be enough for engine to keep spluttering on. Need to cut ignition, either at ECU or preferably finding the relevant fuse for the coils and diverting the wire to the cut out. I would suggest go to coil packs, probably 4 wires, 2 thick, 2 thin. Identify the thick wire that is not going to earth. This is probably the one to the fuse box, note colour of wire, say red/white and look for all the similar wires at fusebox and check which one is going to coil packs by pulling fuse and checking at coil pack for voltage. OR you may have a Relay which the coil power comes from, if so you can intercept that relay which will do a similar thing.
Good Luck

 

[Paul JA]

Can you not put the auxiliary contact on the isolator in series with the the car ignition switch

The ignition is by key card and the start stop is by push button - so not that obvious where to break into the wiring
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Its never as simple as that with these here modern cars... lol
Cutting fuel pump is not a great idea as car runs on and upside down may well be enough for engine to keep spluttering on. Need to cut ignition, either at ECU or preferably finding the relevant fuse for the coils and diverting the wire to the cut out. I would suggest go to coil packs, probably 4 wires, 2 thick, 2 thin. Identify the thick wire that is not going to earth. This is probably the one to the fuse box, note colour of wire, say red/white and look for all the similar wires at fusebox and check which one is going to coil packs by pulling fuse and checking at coil pack for voltage. OR you may have a Relay which the coil power comes from, if so you can intercept that relay which will do a similar thing.
Good Luck

Thanks

The engine run on is my concern if cutting the fuel pump, I think I need to find the coil supply of cut the ecu supply

 

[plugsandsparks]

This might help. Its on page 293, gives coil supply pin outs.

I had a similar experience with a cayman rallycar. I needed to get rid of ABS but retain speedo, get rid of steering lock but still be able to start the car....and lastly find an engine cut for both the Safety cutoff and flat shift gearbox controller, whilst keeping all the other systems "happy" - Non trivial and thats after getting the full wiring diagrams off Porsche..

I would check to see if when the battery is cut that you dont have the steering locked, this can be tricky if you want pulling out of the gravel or need to get on a trailer and for whatever reason cannot power the car up.
cheers
P&S
BTW if the car is local to Derbyshire , PM me and may do a driveby and at least identify the stuff for you

 

[Paul JA]

This might help. Its on page 293, gives coil supply pin outs.

I had a similar experience with a cayman rallycar. I needed to get rid of ABS but retain speedo, get rid of steering lock but still be able to start the car....and lastly find an engine cut for both the Safety cutoff and flat shift gearbox controller, whilst keeping all the other systems "happy" - Non trivial and thats after getting the full wiring diagrams off Porsche..

I would check to see if when the battery is cut that you dont have the steering locked, this can be tricky if you want pulling out of the gravel or need to get on a trailer and for whatever reason cannot power the car up.
cheers
P&S
BTW if the car is local to Derbyshire , PM me and may do a driveby and at least identify the stuff for you

Thanks for the info

So PPM2 pin8 is the common supply to all 4 injectors.

Im assuming the ECU switches the -ve side ?

It looks like the white wire on the injectors is the common and they are switched in pairs. See attached 20/21/22/23 are the coils.

I'm in Stoke on Trent so not a million miles away

 

[plugsandsparks]

That makes sense. Its possible to fire two coils at the same time , "wasted spark" but would expect ecu to fire injectors sequentially in a modern car.
Its also looks like Renault are using semiconductor power distribution units, rather than fuses and relays.
So, i guess, best way to try is : identify the "wire" best you can. Start engine, whilst running cut the wire cleanly with wire cutters, ensuring none can come into contact with anything else. Engine should stop immediately.
BTW - yes, generally power , +12V is generally fed to injectors and coils with the ECU completing the ground connection using semiconductor switching.

 

[Paul JA]

I'm having difficulty identifying which fuse protects the coil common, I've found which connector from the fusebox it comes from, there is one fuse @ 5A that says injection computer. Any idea what load (amps) 2 coils would take ? Aux contact on the switch is 5A rated I believe

 

[plugsandsparks]

Me too, the coil common supply appears on the drawing to be fed from a PDU output not a fuse. "Injection Computer" - i would read that as the ECU which is around 5 amps.
Coil amps for four cylinder is typically fused at 15A, never tested one as it depends on revs as the current draw is proportional to the No of sparks per second.
I dont think the 5A fuse you have identified is the coil supply.

 

[Paul JA]

I think the easiest option is to cut the ECU supply local to its connector and route that to the aux contact on the cutoff switch

 

[Jrautolec]

If the car has a coil pack, usually it will have 1 12v ignition supply, and 2 ignition drivers, easiest way is to cut the 12v and run it through the 2 normally open terminals on the red key switch, if it has individual coils, unfortunately your going to have to do a bit of delving into the wiring harness to find the common supply to all the cools,

 

[Paul JA]

I've made progress on this, I've ditched the mechanical switch and gone for a Cartek GTS. This switches the battery 0V leg. It also needs a permanent supply and can switch up to 40A to use to control the ignition / ECU etc.

There is a fused 30A supply on the battery that feeds the under bonnet protection unit, if lifted this cuts the coil supply and a few other things. The only issue is that the hazard flashers come on when the supply is re-instated so needs a button push.

I have also identified the coil supply wire in the engine loom so if there's an issue I could use just that. The only minor thing is that the CarteK GTS would keep a permanent supply to the coil coil packs even with the ignition off. I could get around this by feeding the new coil supply via an ignition controlled relay.

 

[plugsandsparks]

Thats the one i use. When you switch it off, it cuts supplies to everything so no issue, current draw when off is very small but not insignificant so if the car is off road for a while occassional battery charging will be required. I use the 30A aux supply to feed the coil supplies, this kills the engine dead.

 

[Paul JA]

Looks like I'm on the right lines now. It will all be done when I rewire the battery etc to add a fuse local to the re-located battery and bigger battery cables (they are 'small' at the moment)

 

[Paul JA]

Thats the one i use. When you switch it off, it cuts supplies to everything so no issue, current draw when off is very small but not insignificant so if the car is off road for a while occassional battery charging will be required. I use the 30A aux supply to feed the coil supplies, this kills the engine dead.

So does this mean you have a permanent supply to the coils even with the ignition off as I assume you have used a +ve feed direct from the battery?

Any pics of the install ?

 

[plugsandsparks]

Yes correct, in a normal car this would have gone through a large relay triggered by the ECU. My car is only used in competition and occasional road use and most of the time the Cartek is off. To start the car , cartek on, ignition switch on, press start button. I have removed all mechanical relays for reliability and only used either a solid state PDU or solid state relays.