Wondering if any Fabia 5j ecu experts can tell me if you can attach a failsafe wire at Either 12v positive or a failsafe ground that goes either positive or negative In a error scenario to cut timing ? 

cheers guys 

That question sounds a little oddly-put!

 

Are you asking if you can fit a cut-out switch to the car, to cut the power so as to prevent any danger/problems?

 

There will be a rev limiter fitted as standard so if you go in to the red zone too much, it will cut the revs until they drop down, then ignite again and so on.

 

There will also be what is commonly called the limp mode, whereby the engine detects a fault and retards the engine power, running on a very low power, with little acceleration etc. This is to help protect the engine and components from mis-use/damage whilst enabling you to drive home or to a workshop, to get the fault analysed. Yu will almost certainly get a warning light come up in this instance so don't try to thrash the car, unless you want a pelican! 

 

If that answers your question, great but also, if you meant can you fit a cut out switch in general, I would think you could do this to almost anything that uses an engine. It is just a question of if it will then go on to cause other electrical gremlins, etc so may be worth avoiding unless you know what you are doing!

 

You could also fit an isolator to the battery negative terminal if you so wish. Switch this on and off when doing certain jobs on the car or to cut the power if needed. I am not sure how this will affect other systems if the car WAS running, though as I remember many years ago, someone scrapping a car, who started and warmed it up, then whipped off the battery to keep it, whilst the car was still running. This would have been a pre-ECU vehicle but it ran, albeit possibly without certain functions. An isolator like this will prevent the vehicle from being started by key but will also possibly upset any alarm fitted and stop the clock, lights, windows, central locking, etc from working until switched back on. Probably again, an idea for the workshop but in day to day work, not worth it. Might be worth having if you have the fan overrun issue some people have had, until it gets sorted!

My question would be why the need for it ?

Kinda why I wondered what he meant...

I have a water meth kit with failsafe gauge if the meth goes into failsafe there is two wires one grounds out in a failsafe condition the other goes to 12v+ so want to connect to either a sensor of the ecu to retard timing 

2 hours ago, thomasaspin said:

I have a water meth kit with failsafe gauge if the meth goes into failsafe there is two wires one grounds out in a failsafe condition the other goes to 12v+ so want to connect to either a sensor of the ecu to retard timing 

Surely the remap needed to make this setup work would have that built in?

1 hour ago, chimaera said:

Surely the remap needed to make this setup work would have that built in?

How would the map know when the water meth isn’t working as the water meth is a standalone unit 

52 minutes ago, thomasaspin said:

How would the map know when the water meth isn’t working as the water meth is a standalone unit 

If it's standalone then how is it advancing the timing (your original question of how to retard the timing in the event of a problem suggests that something is advancing the timing when this kit is active)? TBH I think putting methanol into the engine without remapping/replacing the ECU to control it is looking for trouble.

11 minutes ago, chimaera said:

If it's standalone then how is it advancing the timing (your original question of how to retard the timing in the event of a problem suggests that something is advancing the timing when this kit is active)? TBH I think putting methanol into the engine without remapping/replacing the ECU to control it is looking for trouble.

I think your confused here bud , the ecu is getting remapped the remap itself is advancing timing fueling etc I have a Aem water meth kit with a failsafe gauge the failsafe gauge has inputs which measure meth injection cc/min / low level , pump failure etc in a water meth fail it has two wire outputs one being 12v positive the other being ground I want to connect this to a sensor or piggy back a wire on the ecu to cut timing as to protect the engine, I also have a boost controller that alters boost pressure I’m going to use a relay and take one of those wires and it will cut the boost pressure to wastegate pressure in a fail scenario but I want that added level of protection to basically put the car into limp mode in a fail 

23 minutes ago, thomasaspin said:

I think your confused here bud , the ecu is getting remapped the remap itself is advancing timing fueling etc I have a Aem water meth kit with a failsafe gauge the failsafe gauge has inputs which measure meth injection cc/min / low level , pump failure etc in a water meth fail it has two wire outputs one being 12v positive the other being ground I want to connect this to a sensor or piggy back a wire on the ecu to cut timing as to protect the engine, I also have a boost controller that alters boost pressure I’m going to use a relay and take one of those wires and it will cut the boost pressure to wastegate pressure in a fail scenario but I want that added level of protection to basically put the car into limp mode in a fail 

This is all information that you should have posted in the OP. If the ECU doesn't know what the methanol kit is doing, it's dangerous as the engine is effectively out of control. This is also a question that should be put to your tuner rather than asking here, as the tuner (assuming they're competent and familiar with what you're trying to do) is going to have a better idea of how to do this. If the tuner has already suggested that this is a bad idea, it would be a good idea to listen to them.

...Perhaps he wanted to keep the mod under the radar, so to speak. Might well be for insurance purposes. I think thomasaspin, you are getting in to serious modding here, rathe the needing help with a fix to a common issue, etc.  think Chimaera's advice is well worth noting!

 

Good luck with the project.I

The usual solution to your issue with the methanol injection is to use a piggyback programmable interceptor ECU, this can also control nitrous etc.