How a TD5 starts.

Can fuelling be calculated by the injection timing map within the engine ECU using data from both crank position/speed sensor and the electronic unit injectors?

Though I got another 5 on the Richter scale down here. Has the AC been on road test yet?

WSLR said:

Can fuelling be calculated by the injection timing map within the engine ECU using data from both crank position/speed sensor and the electronic unit injectors?

Though I got another 5 on the Richter scale down here. Has the AC been on road test yet?

Click to expand...

Yep,the ecu uses a fuel map and references all the sensor inputs to calculate initial point of injection and duration.Remember the ecu only outputs to the injector solenoids,the cam has no position sensor and the lobes just pressurize the fuel in the EUI's - no injection takes place till the ecu fires the solenoid.
The AC is sorted,and from the way it goes,(wheelspin in first and second with little effort.) I think its making the 600 bhp it was built for.Keep an eye out on the M5 this afternoon and you might see it.

eightinavee said:

Yep,the ecu uses a fuel map and references all the sensor inputs to calculate initial point of injection and duration.Remember the ecu only outputs to the injector solenoids,the cam has no position sensor and the lobes just pressurize the fuel in the EUI's - no injection takes place till the ecu fires the solenoid.
The AC is sorted,and from the way it goes,(wheelspin in first and second with little effort.) I think its making the 600 bhp it was built for.Keep an eye out on the M5 this afternoon and you might see it.

Click to expand...

How far down the M5 are you going?

Not me - the owner ! (Depends how long it lasts before he blows it up or crashes/runs out of fuel,or gets stopped by the cops )
Have you got the "drilled" TD4 going yet ?

eightinavee said:

Not me - the owner ! (Depends how long it lasts before he blows it up or crashes/runs out of fuel,or gets stopped by the cops )
Have you got the "drilled" TD4 going yet ?

Click to expand...

Yes, Monday morning as per your prediction. The 2 x 6 pin multiplugs on the ECU had been put in the wrong place.

Anyone got any ideas then ?

Are we still on this question?

:nothingtoadd:

eightinavee said:

Anyone got any ideas then ?

Click to expand...

What's your theory on it then?

Ok,I have a couple of ideas - they all involve the crank sensor.This sensor does more than tell the ecu speed and postion of the crank.it also looks at the rate of change of speed,this is useful for cylinder balancing esp at idle.But I'm thinking the ecu looks at the rate while cranking,so as # 1 piston comes up on compression the crank will slow down as its harder to turn.So when its going up the bore on the exhaust stroke there is very little resistance so it will speed up.I'm thinking that the ecu decides from this difference.
The other thought was that it gives a squirt to the injector on each turn of the crank then just shuts off the one that does not make progress - ie the crank will speed up massively when the cylinder fires.But I sort of discounted this as putting unburnt fuel out of the pipe is not too clever for emissions.
When I get a chance I'm going to try to prove what happens by scoping the crank sensor and # 1 injector.

still reckon it's simply a case of the valve is closed so fuel can't be injected into the combustion chamber. after all the full cycle is in four stages hence a four stroke cycle.

Induction - compression - ignition - exhaust.
inlet open - all closed - all closed - exhaust valve open.

redhand said:

still reckon it's simply a case of the valve is closed so fuel can't be injected into the combustion chamber. after all the full cycle is in four stages hence a four stroke cycle.

Induction - compression - ignition - exhaust.
inlet open - all closed - all closed - exhaust valve open.

Click to expand...

Which valve ?

I'll have a think about this...

the fuel is stored and pressurised in the injector. not like a commonrail diesel. there has to be some sort of pump or solenoid attached to the camshaft.

is the crank shaft sensor reading direct from the shaft - or from a rotation that is gear driven by the crank at 2:1 - so that it can differentiate the inlet and outlet strokes?

Anderzander said:

is the crank shaft sensor reading direct from the shaft - or from a rotation that is gear driven by the crank at 2:1 - so that it can differentiate the inlet and outlet strokes?

Click to expand...

Thats the problem,the crank sensor reads the teeth around the flywheel - so not really an obvious answer.The unit injectors develop hydraulic pressure from the 3rd lobe on the cam in between the inlet/exhaust lobes - then the pressure is released when the ecu fires the solenoid.

Is there sommat in the injector that prevents the solenoid from firing unless there is sufficient pressure? That way, it wouldn't matter if the ECU sent a "fire" signal every revolution of the crank - it would only work when there was sufficient fuel pressure, i.e. at the top of the compression stroke.

Doozils dun't need a fire signal. It's fired by compression just needs fuel fired in at the correct moment. still reckon it's simply a case of cam timing supplying the fuel. ECU just decides when and how much to inject the doozil.

redhand said:

Doozils dun't need a fire signal. It's fired by compression just needs fuel fired in at the correct moment. still reckon it's simply a case of cam timing supplying the fuel. ECU just decides when and how much to inject the doozil.

Click to expand...

When and how much - there you go - WHEN....

eightinavee said:

Here is a little teaser for you TD5 fans....
Being that the TD5 only has a crank sensor and no cam sensor,(Unlike the BMW engines in TD4 and TD6.) how does the ECU know when piston 1 is on the correct stroke,(IE firing stroke,not inlet stroke.) to commence injection and fire it up ?
I think I know how it does it but I wondered what others thought or indeed know.

Click to expand...

Great question! Here's my thoughts.

The ECU knows the crank position from the sensor, but presumably the injectors will only fire fuel in when (1) the ECU tells it to (via electrical signal), and (2) the overhead cam for that injector is in the right position to pressurise it. I.e the injector only injects fuel when the crank is at the correct TDC (compresion not exhaust).

The question remains then - how does the ECU know the cam position ?