Bbjsw10's
Kill switch how-to thread got a little hijacked by details, so I'm starting a new thread to cover diesel engines and how to make them stop.
I recently found some detailed info on the workings of my engine and hopefully it will be enough to make a safe kill switch. I also hope that this will help others in their quest for understanding the Zen of Diesel.
Quick intro:
My engine is a commonrail turbodiesel. It is a second generation version of PSA's (Citroen/Peugeot) HDi direct injection technology. The first generation were the 1.4, 2.0 and 2.2 liter 8v engines, the second are the 1.6 and 2.0 liter 16v. The 1.4 and 1.6 engines can also be found in Fords as the TCDi Duratorq, and also in Volvos, Suzukis, Renaults, Fiats, etc.
Older diesels had a pump for each injector, while in commonrail technology there is one pump responsible for creating very high fuel pressure in a reservoir used by all four injectors. This, along with direct injection, gives a much better air-fuel mixture, which increases engine efficiency, power by around 25% and low end torque by 50%, reduces fuel consumption by around 20%, and reduces emissions. Of course, this is made possible by heavy use of electronics (calculators with myriads of sensors). This may help in finding a safe way to stop an running diesel engine, but may be very easy to break something (like something very small and very expensive).
After finding out that neither disconnecting the cam position sensor, nor the crankshaft sensor stops the engine (doesn't even throw a code),
dcb proposed unpowering the fuel pump. HDi engines have two fuel pumps, the first pumps low pressure fuel from the tank, the second creates high pressure (200-1350 bar) for the injectors. Turning the first one off may just starve the second one, causing the pressure at the injectors to get lower and lower, possibly messing up emissions. On the other hand, the high pressure pump is powered off the camshaft, so it can't be easily turned off. It does, however, have a switch for disabling one of its three cylinders. This is used to reduce the pressure when there is no load on the engine (in normal operaton the high pressure fuel pump uses up to 3.5kW of power!). The pump uses the third cylinder either when load is between 66%-100% of max or when idling. I guess that deactivating this third cylinder during idle won't turn the engine off, but would it help use less fuel? I need that SGII!
So, next I tried to find out when the ECU cuts the injectors. This happens either when engine speed is above 5300rpm, or when the gas pedal is in "0" position when in gear. In the second case, fuel is sent to injectors when engine speed drops below 2200rpm. Hmmm, could I trick the engine into cutting the fuel supply to the injectors by sending it a sygnal to make it think that engine speed is above 5300rpm? Somehow, this doesn't seem like a good idea. But maybe I could tweek it so that fuel is cut off down to about 1200rpm, instead of 2200rpm (I hardly ever go that high, even when engine braking)? I really need that SGII!
Here is what happens when ignition is turned off (key turned):
- Fuel pressure regulator voltage = 0 = minimum RCO (open cycle ratio?)
- Fuel pump (low pressure) power off
- Stop engine thru injector cut off
- Turn off injector calculator
Every time the engine is stopped, these four events are done in a different order to allow the ECU to run a diagnostic.
There is also an emergency engine shut down procedure, which happens when the ECU finds an error in one of the following:
- EPROM in the injector calculator
- Engine speed sensor
- Cam position sensor
- Fuel pressure sensor
- Injector error (1 to 4)
So, all of this information, and what to do with it? I have a few ideas on how to kill the engine, but I'm not sure whether they would harm the engine, harm the ECU, or at least make it throw a code and go into limp mode until I pay $$$ at a service station to turn it off. How about
:
- Kill the lower pressure fuel pump and see what happens
- Hack the fuel pressure sensor to tell the ECU the pressure is too low/high
- Trick the ECU into thinking the engine speed is such that the fuel should be cut to the injectors
- Cut sygnal to one of the injectors and see if the ECU sends an emergency shut down (rebuild engine if not)
Any safer ideas? As I mentioned earlier, the engine doesn't react to unplugging neither the cam, nor the crankshaft (engine speed) sensors, though I didn't pull both at the same time, so maybe the ECU is able to get its info from only the one that is available? Or maybe instead of unplugging it, the sygnal lead should be grounded to mass? I'd like input from anyone who's tried, even those dumb hall sensors cost a fortune.