Battery Cut Off switch WITHOUT ECU-Reset?
Discussion
Yes there is, wire the ECU supply to the unswitched side of the battery, there is a big but though
You will very likely have noticed that the majority of posters to this forum wire master switches in series with the main positive battery cable, if they are racing the car and need to wire the master switch to FIA Regulations.....ok it's a must
If you're not racing the car you could do a much better job than thee above......If the main supply from battery to starter motor is run safely and well secured it will never cause a problem, wiring problems/fires more often than not start from harness or component short circuits
Are you going racing?
You will very likely have noticed that the majority of posters to this forum wire master switches in series with the main positive battery cable, if they are racing the car and need to wire the master switch to FIA Regulations.....ok it's a must
If you're not racing the car you could do a much better job than thee above......If the main supply from battery to starter motor is run safely and well secured it will never cause a problem, wiring problems/fires more often than not start from harness or component short circuits
Are you going racing?
Edited by Penelope Stopit on Saturday 15th June 15:24
LLantrisant said:
is there an easy way to install a battery cut-off switch which leaves the ECU under power, hence no ECU Reset each time the cut-off switch is operated?
Other than re learning a few things until upto temp why is disconnecting the Ecu an issue for you if you don’t mind me asking. 
LLantrisant said:
my car is only used on the road.
my impression is that without cnnecting the battery, it nees less cranking for starting and it has a better "idling-behaviour" straight away.
i also thought that the ecu will "learn" also over a longer periods, hence my question.
If this is the case, as you have already thought, keep the ECU live where it mattersmy impression is that without cnnecting the battery, it nees less cranking for starting and it has a better "idling-behaviour" straight away.
i also thought that the ecu will "learn" also over a longer periods, hence my question.
You need 2.5 mins at around 90'c at a fixed idle to re learn the long term trim. If you want to keep power on the ECU you will need to run a separate 12v wire from the battery (id suggest with a 1 amp fuse) to bypass the switch, but you will need to cut the 12v feed wire to the ECU before you connect this new supply to the ECU. If you don't the 12v feed will feed back into the now switched 12v supply and make your isolation less effective and it will blow your 1 amp fuse if something draws more than 1 amp on the 12v un switched supply like side lights.
Edited by blitzracing on Sunday 16th June 19:40
blitzracing said:
You need 2.5 mins at around 90'c at a fixed idle to re learn the long term trim. If you want to keep power on the ECU you will need to run a separate 12v wire from the battery (id suggest with a 1 amp fuse) to bypass the switch, but you will need to cut the 12v feed wire to the ECU before you connect this new supply to the ECU. If you don't the 12v feed will feed back into the now switched 12v supply and make your isolation less effective and it will blow your 1 amp fuse if something draws more than 1 amp on the 12v un switched supply like side lights.
Is your above post a tongue in cheek one or are you being serious?Edited by blitzracing on Sunday 16th June 19:40
If you are joking I won't comment any further
Your point is what? A separate dedicated fused supply to the ECU to keep the RAM alive for the trim values. I'm going to love this one, as it will no doubt involve a massive fire risk or a potential huge arc that will electrocute someone with 12 volts as is the way in Penelope land.........
You can use something like this (or build it yourself with a breaker instead of the fuse) https://www.autosparks.co.uk/quick-battery-isolato...
blitzracing said:
Your point is what? A separate dedicated fused supply to the ECU to keep the RAM alive for the trim values. I'm going to love this one, as it will no doubt involve a massive fire risk or a potential huge arc that will electrocute someone with 12 volts as is the way in Penelope land.........
You forgot the relay(s).Steve
The Battery Brain remote battery disconnect device has two male spades that remain permanently live even after you've activated the unit. These permanent live spade terminals are intended for the clock and the radio, the idea is when you disconnect the battery your clock retains the time and your radio retains its channel presets.
You could easily use one of these permanent live spade terminals to supply your ECU, but to be honest you could just as easily use a ring terminal bolted to the battery terminal clamp bolt which would of course always be a permanent live no matter what type of battery disconnect system you choose.
You could easily use one of these permanent live spade terminals to supply your ECU, but to be honest you could just as easily use a ring terminal bolted to the battery terminal clamp bolt which would of course always be a permanent live no matter what type of battery disconnect system you choose.
Steve_D said:
blitzracing said:
Your point is what? A separate dedicated fused supply to the ECU to keep the RAM alive for the trim values. I'm going to love this one, as it will no doubt involve a massive fire risk or a potential huge arc that will electrocute someone with 12 volts as is the way in Penelope land.........
You forgot the relay(s).Steve
blitzracing said:
Your point is what? A separate dedicated fused supply to the ECU to keep the RAM alive for the trim values. I'm going to love this one, as it will no doubt involve a massive fire risk or a potential huge arc that will electrocute someone with 12 volts as is the way in Penelope land.........
My point is that you have cut the battery positive supply to the ECU that is fused at 20 Amps or close to and connected a 1 Amp fused supply to the ECUPerhaps you're not loving it so much after all
Chimp871 said:
Why not cut the sarcasm, it's tedious to read.
There is no sarcasm on my part.blitzracing said:
Your point is what? A separate dedicated fused supply to the ECU to keep the RAM alive for the trim values. I'm going to love this one, as it will no doubt involve a massive fire risk or a potential huge arc that will electrocute someone with 12 volts as is the way in Penelope land.........
blitzracing is definitely not going to love this onePenelope Stopit said:
blitzracing is definitely not going to love this one
If you knew what you where taking about you would realise that all the main current switching for the ECU is done by grounding the relays in the loom or grounding the injectors, the ECU itself does not supply any significant current so you don't need a 20 amp fuse to supply 12v on the ECU Pin 15 as this is where your permanent feed would need to go. I'm beyond bored with your nit picking, go and bother another forum with your 3 posts a day about nothing of any use, you wont find any friends here.
Edited by blitzracing on Tuesday 18th June 21:49
blitzracing said:
If you knew what you where taking about you would realise that all the main current switching for the ECU is done by grounding the relays in the loom or grounding the injectors, the ECU itself does not supply any significant current so you don't need a 20 amp fuse to supply 12v on the ECU Pin 15 as this is where your permanent feed would need to go.
I'm beyond bored with your nit picking, go and bother another forum with your 3 posts a day about nothing of any use, you wont find any friends here.
I'm beyond bored with your nit picking, go and bother another forum with your 3 posts a day about nothing of any use, you wont find any friends here.
Edited by blitzracing on Tuesday 18th June 21:49
Steve_D said:
A 1 amp supply into pin 15 of the RCU will probably be more than enough to keep the memory going.
At present that comes from fuse 2 (20 amp) but fuse 2 also supplies the main supply into the ECU pin 2 plus the MAF and 8 injectors hence why it is 20 amp.
Steve
OP The two posts above are from people who know what they are talking about; they both have extensive knowledge of the ECU that manages the injection system on these vehicles.At present that comes from fuse 2 (20 amp) but fuse 2 also supplies the main supply into the ECU pin 2 plus the MAF and 8 injectors hence why it is 20 amp.
Steve
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