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PostPosted: Fri Dec 30, 2016 4:22 pm 
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Hi All,

Something that I have been thinking about for a while is that my car often starts with almost no cranking at all - it just bursts into life. Whilst generally this is considered to be a good thing with cars, given that my car sometimes goes 3-4 or more weeks between being used I have been thinking about is this good for the engine as there won't be any oil apart from a film particularly at the top.

When I change oil I always remove the EFI fuse and crank the engine until I see oil pressure in the head before I start the car. I was wondering if there was any merit in installing a switch in the cabin to prevent firing whilst turning the engine over and then the engine can be started. If it is a good idea when any thoughts on how I would do this - which circuits would need to be used?

Cheers :)

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PostPosted: Fri Dec 30, 2016 11:14 pm 
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I would simply spur from the EFI fuse location the cabin and add an inline fuse as a precaution.


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PostPosted: Sat Dec 31, 2016 1:35 am 
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If it were me, I would interrupt the live feed at the ECU as there is then no need to bring wires in from the engine bay.

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PostPosted: Sat Dec 31, 2016 11:36 am 
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Not sure if your link ECU has this but....

Some links support an oil pressure sensor input that could be used to prevent the engine running without pressure. That would give a very neat and idiot proof solution

In the past I wondered about buying a pressure switch from RS/Maplin etc and chopping it into the efi wire in the fuse box. As usual apathy won in the end


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PostPosted: Sat Dec 31, 2016 2:55 pm 
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two_OH_five wrote:
Not sure if your link ECU has this but....

Some links support an oil pressure sensor input that could be used to prevent the engine running without pressure. That would give a very neat and idiot proof solution

In the past I wondered about buying a pressure switch from RS/Maplin etc and chopping it into the efi wire in the fuse box. As usual apathy won in the end


Excellent idea, it will also help reduce damage caused by oil surge.
A quick look at G4 ECU settings indicate a number of options - anto theft or dual ECU - either will stop both injectors and ignition. For other ECU's which don't have these maybe something like flat shift or dual map with second map set for zero fuel.

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PostPosted: Sat Dec 31, 2016 6:13 pm 
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This is similar to the strategy with my track project. With long periods between running the engine oil tends to drain to the lowest parts of the engine so it is necessary to prime the external dry sump oil pump before starting the engine. Whilst this can be done with a speed brace, cranking using the starter motor with the fuel pump, injectors and ignition off is a lot simpler. Ideally I would also have a couple of T-pieces in the oil lines for an oil warmer. Maybe this last mod isn't practical for a road car though!

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PostPosted: Sat Dec 31, 2016 8:14 pm 
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Thanks for the ideas - gives me something to start with.

I am nervous of the idea of a switch for the ECU as I don't really want the possibility of the ECU switched off whilst in motion.

The ECU idea seems like the best possibility, what I really *think* I want is a push (not latching) switch that interupts the starting process but only whilst that is happening ie:

Starting the car:

Press and hold button > turn key - starter spins - oil pressure builds > button is released and car fires

Whilst driving - pushing the button does nothing

No idea if that is even possible.

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PostPosted: Sat Dec 31, 2016 9:03 pm 
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You could do it the old fashioned way. Many an old car came with a manual pushbutton under the bonnet that would turn over the starter motor. All it would require is a wire from the battery POS to the starter solenoid terminal via a momentary push to make switch. You'd have to open the bonnet to activate though so you're now a million miles away from yanking the EFI fuse anyway. Unless you routed said switch and wires into the cabin somewhere. It has the advantage of being failure proof but the disadvantage is that pushing the button with the engine running would also engage the starter motor

I think what you suggest could possibly be achieved via the main circuit opening relay next to the stock ECU but I don't have wiring diagram to hand to see if that would also cut out the circuit to the key switch that activates the starter
It could alternatively be done via a relay on the steering column along the lines of a turbo timer but working in reverse so to speak. Quite simple to get the action you want where the override button is non functional once the car is running


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PostPosted: Sun Jan 01, 2017 2:17 pm 
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Having a button that does nothing while running is difficult without building in logic in the ECU. If you investigate the anti-theft input to the G4 it may have this logic - i.e. the engine won't cut once started.

iirc the 'circuit opening relay' is actually the relay which switches on the fuel pump and has a dual coil - one being driven by the ECU and the other by the starter circuit.

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PostPosted: Mon Jan 02, 2017 11:28 pm 
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Needs a "self energising" (possibly known as a latching relay depending on which college you went to :lol: ) relay where the NO contacts are also connected to the coil drive. You feed (say) IGN to the coil via a NC switch and also via a set of NO contacts. If the button is pushed when the ignition is switched the relay isn't activated and the IGN signal isn't fed on. As soon as the button is released the relay is energised and further button pushes do nothing as the relay now provides its own coil drive

I sort of have a feeling the main circuit relay might do this if you interrupt the start signal


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PostPosted: Tue Jan 03, 2017 5:30 pm 
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I wonder how the engine will respond to this on start up.

Pretty much all ECUs (including stock & Link) have an initial injector squirt prior to cranking (circa 8-40 mS from memory for stock 440cc ST185 subject to water temp) which you'd need to consider the impact if the button was released during cranking.

It would be much cleaner IMHO to undertake the oil priming as a totally individual event, shut-down engine and then start normally.

The "anti-theft" shuts down both fuel & ignition but I've yet to find this option for the G4 but have located it for G4+!

I'm still learning the Link software so may well be wrong.

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PostPosted: Tue Jan 03, 2017 10:43 pm 
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Diceman wrote:
........It would be much cleaner IMHO to undertake the oil priming as a totally individual event, shut-down engine and then start normally................

Agree :)

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PostPosted: Wed Jan 04, 2017 3:05 pm 
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Alright so this would appear to be more complicated than I had first imagined.

Perhaps the simplest solution would be to do as Don and JP have suggested and seperate the priming from the starting.

To do this I propose to have a switch that just works the starter motor to prime the engine. Then I will start the engine as normal with the key. To avoid accidental pressing of the button whilst the engine is running I will fit some sort of cover or protector to the button.

Can anyone suggest what he wiring might look like to do this?

Cheers,

Mike

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PostPosted: Wed Jan 04, 2017 5:17 pm 
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Why not switch the circuit that the EFI fuse supplies?

This would be straightforward as the car would function as normal albeit without opening the injectors... just add a toggle switch with protective cover?

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PostPosted: Wed Jan 04, 2017 5:41 pm 
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Kris wrote:
Why not switch the circuit that the EFI fuse supplies?

This would be straightforward as the car would function as normal albeit without opening the injectors... just add a toggle switch with protective cover?


Would that best be done in the engine bay and running two cables in to the cabin or can this circuit be accessed from inside?

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