How a TD5 starts.

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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...
OK let me try to explain. The TD5 ECU does NOT fire the injectors as most peeps assume.

The injectors "fire" once the internal fuel pressure, which is generated inside the injector body by the cam lobes pushing on the injector rod via the roller rockers, reaches a predetermined value approximately 2200 to 3000 bar depending on whether you have an EU2 or EU3 spec engine.

The solenoid merely releases the pressurised fuel to the spillway and effectively shuts the injector under spring pressure as the fuel pressure is released. The ECU adjusts the injector pulse width according to the injector code, engine throttle position, engine temp, fuel temp, ambient air temp, inlet manifold pressure, and a host of other variables to achieve optimum fueling and to "throttle" the engine and control the engine speed. Dont forget that diesel engines control speed by limiting how much fuel enters the cylinder and not by means of choking of the air supply as in a petrol engine.

This is why its important to program the injectors to the ECU to achieve optimum performance. The injectors are accurately measured and coded at the factory. It is the injector code that tells the ECU about each individual injector and its operating characteristics. You can physically swap the injectors around and they will work but not necessarily as well as they could.

To save money and simplify things the TD5 ECU uses a redundant operating cycle for each injector and operates the solenoids on each crank rotation but obviously if the injector is not pressurised it does nothing to affect the engine operation. Some ignition systems use the same principle.

Therefore you do not need a second sensor as the camshaft controls when the injector operates relevant to the crankshaft via the timing chain. You only need to know which cylinder is at TDC at any one time.

Simples.
 
redhand said:
So I weren't far off when I said the camshaft determined whether the injectors fired or not??? :D
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Spot on. Its the camshaft turning at half the crankshaft speed that generates the injection pressure that fires the injector. The ECU controls how long the injector fires for. We are talking micro second adjustments to the solenoid operation so dont expect to be able to see the differences unless you have sophisticated measuring equipment.
 
Shifty1962 said:
OK let me try to explain. The TD5 ECU does NOT fire the injectors as most peeps assume.

The injectors "fire" once the internal fuel pressure, which is generated inside the injector body by the cam lobes pushing on the injector rod via the roller rockers, reaches a predetermined value approximately 2200 to 3000 bar depending on whether you have an EU2 or EU3 spec engine.

The solenoid merely releases the pressurised fuel to the spillway and effectively shuts the injector under spring pressure as the fuel pressure is released. The ECU adjusts the injector pulse width according to the injector code, engine throttle position, engine temp, fuel temp, ambient air temp, inlet manifold pressure, and a host of other variables to achieve optimum fueling and to "throttle" the engine and control the engine speed. Dont forget that diesel engines control speed by limiting how much fuel enters the cylinder and not by means of choking of the air supply as in a petrol engine.

This is why its important to program the injectors to the ECU to achieve optimum performance. The injectors are accurately measured and coded at the factory. It is the injector code that tells the ECU about each individual injector and its operating characteristics. You can physically swap the injectors around and they will work but not necessarily as well as they could.

To save money and simplify things the TD5 ECU uses a redundant operating cycle for each injector and operates the solenoids on each crank rotation but obviously if the injector is not pressurised it does nothing to affect the engine operation. Some ignition systems use the same principle.

Therefore you do not need a second sensor as the camshaft controls when the injector operates relevant to the crankshaft via the timing chain. You only need to know which cylinder is at TDC at any one time.

Simples.
Click to expand...
At last ! A considered answer,the "wasted" firing is what I was looking for - be interesting to see it in real time on the scope when I finally get round to it.
I have to say though that although the ECU does not fire the injector,without it being energised to close the spill port there would be no injection event at all.Also the timing of the solenoid closing has a direct effect on the point of injection - the earlier it closes the earlier the pump will build enough pressure to lift the needle and commence injection.This is how the ecu can control injection advance - otherwise if it were just down to the cam the initial point of injection would be fixed,which is no good at all.
 
eightinavee said:
At last ! A considered answer,the "wasted" firing is what I was looking for - be interesting to see it in real time on the scope when I finally get round to it.
I have to say though that although the ECU does not fire the injector,without it being energised to close the spill port there would be no injection event at all.Also the timing of the solenoid closing has a direct effect on the point of injection - the earlier it closes the earlier the pump will build enough pressure to lift the needle and commence injection.This is how the ecu can control injection advance - otherwise if it were just down to the cam the initial point of injection would be fixed,which is no good at all.
Click to expand...
Now this is where I reach the extent of my limited knowledge. I'm not sure that diesel engines require advancing of the fuel injection like petrol engines do. As I understand it the actual fuel injection is done at or just after TDC as the heat and compression needs to be in the cylinder before the fuel enters in order for the fuel to ignite unlike in a petrol engine which would pre ignite or "knock" or try to run backwards.

I had not considered whether the ECU closes or opens the solenoid but assumed it merely opened the injector to the spillway once it calculated enough fuel had been injected from a given point in the engine cycle. Your theory that fuel is constantly flowing through the injector into the spillway until the ECU closes the solenoid and allows injection pressure to build is sound and makes more sense in that the ECU could control when the injector starts to build pressure and for how long. Yet another reason to properly code the injectors.
 
There was me thinking you were the kiddy on TD5's. TD5's vary injection advance according to speed ,load coolant temp etc,etc. Just like a petrol,even the old Bosch VE pumps and CAV DPA pumps use variable advance.For instance a 300TDI motor runs approx 8 degrees BTDC at idle,advancing up with speed.
 
eightinavee said:
There was me thinking you were the kiddy on TD5's. TD5's vary injection advance according to speed ,load coolant temp etc,etc. Just like a petrol,even the old Bosch VE pumps and CAV DPA pumps use variable advance.For instance a 300TDI motor runs approx 8 degrees BTDC at idle,advancing up with speed.
Click to expand...
Your words not mine. Like I said I'm at the extent of my knowledge in regards to the injection system. Ask me about TD5 mechanical stuff all day long. Electronic wizzardry no. I'm always learning which is why I like these kind of discussions.

So what you are saying is that a diesel engine needs variable injection timing (controlled by the ECU on a TD5 or the injection pump mechanical advance on the TDi) just like a petrol engine does with the ignition?
In that case today I've learnt something new. Tomorrow I'll learn something else.
 
Yep,thats it,the electronics give a much better control for more power,lower emissions and fuel consumption.The older mechanical systems were much more limited in terms of upgrades,often resulting in black smoke....;)
But they all have variable advance.
Totally agree about the discussion,gets you thinking - and learning,got to be good.
 
Can I ask a couple of injector related questions of you guys, for information on something I was wondering about - this is my first TD5 and it's been 30 years since I last owned a landy (a 1953 ex-army 2¼ litre petrol - it was born same month as me.)

My TD5 Defender has had a replacement engine fitted by the previous owner. I am assuming that he hasn't has the ECU re-programmed with the injector numbers.
so:
Q1. Are the injector numbers those that are stamped into the solenoid body?
If so, mine are 2-3-1-2-3 reading from the front (I just fitted a new harness so noted this down while I was in there.)
Q2. If not, how/where do I find this number?
Q3. Can a Hawkeye diagnostic tool, which I have coming to me in the mail, read this info?
Q4. Can the Hawkeye also programme in this info if it has the wrong info?

Your advice would be much apreciated - even if I do have to go to a LR dealer to have it checked/programmed.

Thanks in advance.

Ron.
 
Last edited:
Clanforbes said:
Can I ask a couple of injector related questions of you guys, for information on something I was wondering about - this is my first TD5 and it's been 30 years since I last owned a landy (a 1953 ex-army 2¼ litre petrol - it was born same month as me.)

My TD5 Defender has had a replacement engine fitted by the previous owner. I am assuming that he hasn't has the ECU re-programmed with the injector numbers.
so:
Q1. Are the injector numbers those that are stamped into the solenoid body?
If so, mine are 2-3-1-2-3 reading from the front (I just fitted a new harness so noted this down while I was in there.)
Q2. If not, how/where do I find this number?
Q2. Can a Hawkeye diagnostic tool, which I have coming to me in the mail, read this info?
Q3. Can the Hawkeye also programme in this info if it has the wrong info?

Your advice would be much apreciated - even if I do have to go to a LR dealer to have it checked/programmed.

Thanks in advance.

Ron.
Click to expand...

AQ1. the code is next tu the plug(i think that's the one u mentioned)
AQ2. + AQ3. = Yes

(A=answer;))
 
Wow, that was quick - I thank you for that info, I'm also very glad you could sort out my deliberate q numbers error (I only just noticed I have two Q2's) Thanks. Ron.
 
You can only read the injector codes that are already programmed into the ECU with any type of diagnostic kit. It can not read the codes off the actual injectors. You need to manually program the injector codes on the top of the injectors into the ECU if you have changed injectors or moved their cylinder position. The injectors are cylinder specific in terms of where the ECU stores the codes.
 
Shifty1962 said:
You can only read the injector codes that are already programmed into the ECU with any type of diagnostic kit. It can not read the codes off the actual injectors. You need to manually program the injector codes on the top of the injectors into the ECU if you have changed injectors or moved their cylinder position. The injectors are cylinder specific in terms of where the ECU stores the codes.
Click to expand...

Hi Shifty,

Thankyou, I didn't phrase the Q very well, I did mean can the Hawkeye read the codes stored in the ECU and change them to what the actual codes on the top of the solenoid for each injector if they are different.

To be honest, I have a loan of Sykes Pickavant ACR4 (and a bunch of pods) which is sitting on my coffee table at the moment, but after reading through most of the documentation, I decided I'd rather buy my own Hawkeye for TheBus.

Thanks again for the info - I can't wait to get my hands on my Hawkeye to start getting to know my Landy better.

Ron.
 
I should have read up more about the various systems available, but I did think the Nanocom was dearer than the Hawkeye, so I choose what I thought was the cheaper option as I'm only a diy'er I thought it would be enough for me.
 
I went for the Nanocom because I've used one before and I know it can read and write complete fuel maps and loads of other stuff if I need it to.
I dont think there is much difference in the price between the two.
I had heard that the Hawkeye was a rip off of the Nanocom with fewer options but I cant verify or confirm this.
 
I know nothing of the Nanocom, nor the Hawkeye yet, but when I was thinking about buying a diagnostics tool, I had Googled for info and I found a few posts and threads on LZ where several peeps mentioned they had Hawkeye and seemed very impressed with it. It was also from my having a look round LZ after that that made me decide to join as until then I had only joined 1 other forum, and tyhis one appeared to be much friendlier - though in fairness, the other one wasn't unfriendly.

I find stuff on here when I do a search - or ask a question.

Anyway, I digress,

Time for an oil & filter change then have a look at cleaning my MAP & MAF sensors which are mentioned so often - and lookinto blanking my EGR (if it hasn't already been done.)
 
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