Polygonum was asking how the thoughts of the ECU were translated into actual events inside the cylinder. On its own, the thoughts of chairman ECU are nothing. It is what it does with them that matters!
Which you have described.
I hadn't realised that diesels had ever been designed that took in fuel and air mixture (like a petrol engine) and then relied on critical level of compression/temperature to determine the engine timing. That must have been a very irregular timing, giving rise to very lumpy running. Would you really want detonation to occur a long time before TDC (if the engine was very hot) or a long time after TDC and approaching BDC (if the engine was cold). Seems very hit and miss.
Did it apply it apply to all non-turbo engines, or just some of the very early ones?
Eh? Don't know of any modern engine that needs de-coking regularly. Think this was more a function of older oils anyway.
It's not even strictly true. Direct injection diesel engines have been around for at least 80 years.
Model aircraft diesels still do.
And a compression adjustment screw for ignition timing.
However the diesel I am tyhi8nking of - 60s tractor, seemed to have injection,but it wasn't into the cylinders. Into the manifold.
And of course in between are indirection injection, which is not exactly into the cylinders, either.
Ok' I'll bite.
What do you hook the strobe up to - an injector?
What about multi-injection engines?
What is the relationship between actual ignition time, fuel-air ratio, combustion pressure, engine temperature, given a certain injection time?
Or are all these mere handwaved away?
A little knowledge makes you look stupid,
If I remember things right (my father worked in the truck industry, but I had no real interest in diesel engines) indirect injection gives a slightly more refined result. Early direct injection engines were very efficient, but agricultural.
The advent of electronic injectors and very high fuel rail pressure made direct injection the way to go these days - while giving acceptable refinement for car use. And I've a feeling some engines use a mixture of both.
No it doesn't.
If conventional pump there is kit to measure timing, Ross-Tech do a plugin. You can still have drive by wire on a conventional pump which can calculate injection quantity based on load, turbo etc.
For common rail the timing is dependent on various temperatures, crank speeds, various pressures and load demand. It's important the pressure is limited to ensure damage to pistons, rods etc. An "injection" can be a number of separate events, I recall 5 being mentioned on one system. I would expect this information can be generally gleamed from an ECU diagnostic port.
The OP hasn't come back to say the type of system he has. ECUs may also be different for different levels of tune, or certainly mapped differently. I know the Duratorq engine has different injectors for its range of power outputs on essentially the same engine. For all I know the 'wrong' ECU has been fitted.
Its funny how Diesel stole the limelight when there were various patents that predate his work.
Most model airplane engines are akin to hot bulb, and are not truly compression ignition.
Can you provide an example? Even semi-diesels / hot bulb diesels use low pressure injection.
But not a 'strobe'
At least you understand the complexity. Its almost certain that the engine is running slightly off because its not been connected back to some sensor. OR there is a faulty sensor. If et ECU was needing to be changed it may be whatever broke it, broke the sensor too,
"Checking the timing" is pointless as there is no way to change it directly... If the engine is pinking, more than normal diesel clatter, the timing or fuel air mixture is wrong. Measuring it wont help fix it.
What is needed is to check all the diagnostics and see if there is a sensor fault.
That's not strictly true for all.
What is interesting is that glow plugs are sometimes hot just to reduce emissions. Sort of getting close to a hot bulb engine!
The implication by abusing Mr Cheerful is that it can't be wrong.
Is this reply your way of accepting you could be wrong and Mr Cheerful's post was appropriate for the information at hand?
In message , "Dave Plowman (News)" writes
Umm.. Don't know how the single cylinder Marshall tractor of my youth worked. Starting was hand crank with either cartridge or glowing corrugated cardboard:-)
More recently agricultural diesels have changed from indirect to direct injection (I think) Something to do with bowl in piston from offset chamber.
>
Please read what I wrote. I am not talking about glowplug engines, but 'diesels'.
They run on paraffin and ether, plus oil as they are 2-wstrokes.
I've been looking, but can only find indirect injection examples
It was a long time ago...maybe the one I saw was indirect, just the the injectors weren't straight into the cylinders.
No.
You and mr cheerful seem to be under the false impression that I criticised his post on the grounds of being wrong.
It was on te grounds of being stupid. Not wrong
I.e.
Like 'Oh, my hamster has died" "You had better check is blood pressure"
What is 'pinking'?
IT'S PRE-IGNITION, DUH!
But there isn't, on a diesel any 'timing' you can measure or alter. It is a complex result of many calculations performed by the EMU depending on the input from its sensors. That determines *injection* timing, but it doesn't determine *ignition* timing, as there are then things like flame propagation rates and so on before you get to peak cylinder pressure, which is probably the nearest parameter that corresponds to 'timing'. And that is affected by fuel amount mixing ratio and air temperature and so on.
None of which you can 'measure'. Not without gear even a top garage wont have. And in-cylinder sensors.
Since Mr Cheerful didn't seem to understand any of that, I asked him if he actually knew how a modern diesel works.
It appears he doesn't.
You seem to, a little, but you haven't caught the original point. Measuring whatever you think is 'timing', on a diesel is almost impossible to do to any level of accuracy, and almost completely pointless when you have.
You can't rotate the distributor to 'fix' it. There isn't one.
You can look at where the injectors are firing if you want, but that doesn't tell you any more than that is when they are firing, Maybe they are firing too early. Maybe they are firing too weak.. The EMU will tell you that.
And tell you if any sensors are out of spec. Or you may have to guess at which one is faulty. e.g. it might be that a temperature sensor appears OK, but isn't sensing inlet air temperatures correctly.
We so far don't know what the diesel type is, and we don't know what led up to the EMU being changed. If the engine was running good and not pinking before, why was the EMU changed.
E.g. my boiler started leaking, and before it could get fixed, it stopped firing, but the air and fuel pumps would run indefinitely. Then it fired, but went into lockout and wouldnt run at all.
There turned out to be three distinct faults which all had occurred either one because of te other, or purely concentrically.
It was leaking. It was soaked in te combustion chamber and the wire to the photocell had corroded and was sometimes touching, sometimes not. Ther was an issue with the fuel solenoid I think.
The sensor and the control box were changed, but it wasn't till the solenoid was fiddled with that it all sprang to life
The moral is that sometimes fixing one thing reveals a problem elsewhere that was masked.
True, but then nor can you make any comparable adjustment with a modern petrol engine. In both cases, timing is determined (at least in part) by sensors such as crankshaft position, with timing offsets controlled partly by non-adjustable algorithm behaviour in the ECU and (maybe) partly by tweaking parameters in the ECU. It is the latter which is the nearest equivalent to rotating the distributor.
Did old non-ECU have any equivalent of rotating the distributor on a petrol engine - for example, to alter the timing of the mechanical fuel injectors relative to TDC.
I take you point about timing of *ignition* in a diesel being a bit less precise than in a petrol engine, because it doesn't happen precisely when the spark of a petrol engine triggers it, but is subject to extra uncertainty about the delay between injection beginning and detonation beginning. Presumably there are sensors in the cylinder head which can sense the delay between the two at any instant and can adjust the injector timing accordingly so the detonation occurs exactly when it is wanted - ie it compensates for the variable injection-to-detonation delay.
I really must read up about indirect injection and try to understand how it works. The simplified "Ladybird book" diagrams/explanations for petrol and diesel engines always show (for a diesel) fuel being injected directly into the cylinder, not into an ante-chamber or manifold. When I first heard about cars having direct injection, as if it was a new innovation, I was left thinking "but what other sort is there"?
Why is it that my first diesel car, a 1997 Peugeot with a 1.9 TD (not HDi) engine, usually needed a pause between turning on the ignition and the engine firing when the starter is turned on, whereas my newer cars (Peugeot
2.0 and 1.6 HDi engines) don't require a delay: you can turn the key straight to starter motor and the engine will fire immediately. Presumably the delay in the older engine was for glow plugs to heat up the cylinder to the operating temperature that is normally caused by the previous combustions, but why do HDi engines not need this to occur, or at least heat up so quickly that you don't have to allow for it?
Now. Just. A. Minute., NP.
Are you now claiming that it's a waste of time to check the blood pressure of a dead hamster? Some clarification required here.
I'm pretty sure he has said somewhere that it just simply conked out one day. You seem to be jolly clever with this diesel malarky, NP. Let's say the OP could insert some sort of delay line in the injector leads so when an actuation pulse comes down the wire, it can be momentarily 'held' by an adjustable interval to correct this pre-ignition (if that's what it is). Would that be viable? Obviously you'd have to do this by the same delay for each injector control wire. Or how about a similar arrangement for the crankshaft position sensor - only requires one intervention rather than several. Just a thought....
That was before the introduction of common-rail injection systems, though, n'est pas? The good old days when everything was simpler.
Nope. Certainly not in the conventionally accepted sense.
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