Nistune Forums

I have gauges with warning function, and I'm thinking to set up an engine failsafe system, trigger by those warning output.
Anyone tried such failsafe on stock ECU ?
Which way to cut ? Injector power ? Boost solenoid ?
Any suggestion are welcome !

Factory ECUs only really have limp values for missing MAF, coolant sensor and then for idle limits (speed=0) then lower RPM and TP limits. All limits cut only the fueling from the ECU

One of the projects I have in mind (that I'll never have time to build) is to take boost from a boost sensor and AFR from your wideband as inputs - and output some sort of alarm any time AFR goes leaner than say 12.5:1 when boost is more than 5psi. That'd save a lot of engines when the fuel system fails. Like they do so often!

In the same way you could also take coolant temp as an input.

I had another idea when tuning a car with water/meth injection the other night. Obviously if you tune for water/meth and the water/meth fails you're in a world of trouble. But how to incorporate the failsafe from the W/M system into factory ECU? Easy - have it operate a transistor or relay that shorts out the knock sensor input to the ECU. ECU then jumps to knock maps. It'd also create a fault code but in the scheme of things that doesn't matter. Your engine has been saved.

You could do a similar thing with the coolant/boost/AFR failsafe project that I'll never have time to do. Have an output to short out the knock sensor. Most Nissan ECU's that we deal with have separate knock maps for fuel, IGN and later ones also have them for boost control (S14/15 and R34).

PL

PL wrote:One of the projects I have in mind (that I'll never have time to build) is to take boost from a boost sensor and AFR from your wideband as inputs - and output some sort of alarm any time AFR goes leaner than say 12.5:1 when boost is more than 5psi. That'd save a lot of engines when the fuel system fails. Like they do so often!

In the same way you could also take coolant temp as an input.

I had another idea when tuning a car with water/meth injection the other night. Obviously if you tune for water/meth and the water/meth fails you're in a world of trouble. But how to incorporate the failsafe from the W/M system into factory ECU? Easy - have it operate a transistor or relay that shorts out the knock sensor input to the ECU. ECU then jumps to knock maps. It'd also create a fault code but in the scheme of things that doesn't matter. Your engine has been saved.

You could do a similar thing with the coolant/boost/AFR failsafe project that I'll never have time to do. Have an output to short out the knock sensor. Most Nissan ECU's that we deal with have separate knock maps for fuel, IGN and later ones also have them for boost control (S14/15 and R34).

PL

It is a very good idea to use knock sensor, to trigger using knock map, you also remind me no need to use pull down switch to switch between rom files.
What I'm thinking....
water temp / oil temp warning activate stage 1 protection >> cutting boost control solenoid power = lower the boost to wastegate spring pressure
water/meth failsafe kit activate stage 2 protection >> force ecu to use knock maps + cutting boost = bring up the richer mixture from the knock fuel map / retard timing / lower max boost
AFR failsafe kit warning activate stage 3 protection >> cutting MAF or injector power = hard cut for maximum protection
Thank you very much !

Yes, there's only one problem with shorting out the knock sensor - the ECU will raise a fault code. So it'll jump to knock maps but some will also go beyond that by adding extra fuel and taking timing. So it's not a clean way to force the ECU to simply run on knock maps. But for a failsafe strategy I think it'd be worth a go.

PL

>water temp / oil temp warning activate stage 1 protection >> cutting boost control solenoid power = lower the boost to wastegate spring pressure

this can actually be achieved in a very simple manner and I normally do this standard in all the cars that I install an EBC in:

cut the wires that normally go to the standard boostsolenoid and have these wires switch a relay instead.
Have this relay switch the connection between the EBC and the EBC's solenoid and this way you retain the standard ECU's safety control over boost.

>water/meth failsafe kit activate stage 2 protection >> force ecu to use knock maps + cutting boost = bring up the richer mixture >from the knock fuel map / retard timing / lower max boost
>AFR failsafe kit warning activate stage 3 protection >> cutting MAF or injector power = hard cut for maximum protection

these other levels of protection shouldn't be too hard to achieve using an arduino or similar simple MCU.
Hook up a 0-5v wideband and boostsensor signal and a meth level switch to the arduino's inputs, let it do some if..then..else stuff and if not good then disconnect knock-sensor and/or EBC and have it flash a warning light, so you actually know something is wrong and it's not that the car just feels a bit sluggish today