high voltage injectors (HDi diesel)

[ecoxantia]

Exactly so; I'm not familiar with your TDi I'm afraid!

I got my bits from NKC, a bargain.

[ecoxantia]

The HDiguino is now boxed and looking half decent!

A colleague tells me that flow will scale with square root of pressure.

At the moment I've got a calculation that:
-multiplies press by 1000 - to get bars
-multiplies sqrt (press) by injus - to scale injus

It's almost there; with the max allowed "us per gallon" I get a very small mpg in instant display mode, so another factor of 100 and it might display something useful!

[ecoxantia]

Ran a scope over my connections - I still don't have a -ve injector input!
Interesting to see the "pilot" injection and "main" injection.

dcb - will the software be able to cope with these 2 pulses, and where is the code for measuring injector us please?

[dcb]

Cool, so at whatever speed/load that was, the preinjection was about 2ms

the guino should detect what is on that graph, but I don't know the full range of signals.
Dont forget to turn "Injector DelayuS" down to compensate for the higher pressure.

[ecoxantia]

That's at idle.

At the moment the displayed pressure signal is erratic. Seems to me like I need to learn more about programming the arduino if it's to work on this engine.

[ecoxantia]

I can't get a "negative" signal for my injector input with respect to battery (and duino) ground.

dcb - is there any way to change the code to accept the waveform above? Or will I have to do it with hardware?

[dcb]

Sorry, eco, I don't understand your comment, your graph doesn't seem to go negative.

re: code, since you have a scope, I would simply display the injHIus value on the guino while scoping a couple injector pulses and compare the injHIus per half second duty cycle with what you calculate from the scope, and see how far off it is.

You might want to sample some other pulses at the high end of the pressure gauge/rpm scale to see how small that gap might get.

[ecoxantia]

Thanks - good idea about checking the numbers agree.

As the the negative issue -I thought I'd read that I need a negative-going pulse. Well, I scoped both leads to my injector, with respect to battery earth. A black one is shown above, goes from 1 to 3.5V (after the 100k resistor). Is this OK for a mpguino?

So, I scoped the other injector wire - it pulses from 0 to greater than 20V even after the resistor, so is not suitable and looks like the 80V injector feed.

Numbers on my pressure display fluctuate wildly- I need to scope this as well and find out why.

My leads are all screened as I expected noise pickup from the injection system. So far I've thought of noise on the signal that needs to be averaged; noise pickup that I need to filter out, arduino hardware issues that I'm unaware of, and maybe software issues. This is taking a lot longer than I expected!!

[ecoxantia]

Originally Posted by dcb

Sorry, eco, I don't understand your comment, your graph doesn't seem to go negative.

re: code, since you have a scope, I would simply display the injHIus value on the guino while scoping a couple injector pulses and compare the injHIus per half second duty cycle with what you calculate from the scope, and see how far off it is.

You might want to sample some other pulses at the high end of the pressure gauge/rpm scale to see how small that gap might get.

OK I have got some data to check the injector signal - scoped the injector at a range of rpms and noted the raw data (us). Note that this is all with no load, simply revving the engine at standstill.
This is what I got -

rpm [guino (us)] [scope pulse width (us)]
800 398000 10700
1800 260000 9500
2500 191000 9500
3000 91000 11000

The guino appears to be timing between pulses as it drops with rpm.

Also tried to look at the fuel pressure.

The red line is fuel pressure, which rises from 1.3V at idle to 1.8V at 2800rpm (again no load) so that's around 400bar.

Interesting that blips can be seen in the fuel pressure signal, which I reckon are shock waves from the injector suddenly opening and closing.

On driving today, the pressure signal displayed looks OK and I think it's just the display that's erratic. At idle it's about 6, rising to around 32 at the redline. Often it displays 6 digits like "234567" and flashes back to something more believable.

The MPG is inverted, just as you'd expect from the us figures in my table. Looks like it's reading the us between start of injector pulses, rather than the duration of the pulse? So more accelerator pedal = higher displayed mpg!

On a downhill coast, the mpg increases with speed, so the link with mph works OK.

Mph is very stable.

[dcb]

Wow that is a little hard for me to get used to Your injector times are longest at idle though, so as you predicted the pressure plays a much larger role.

An injector sanity check might be to look at the injpulses per half second and try and fugure out if it is counting the gap at different rpms or not (watch out for the cold start after pulse).

on the pressure sensor, do you think those "blips" at 0,2,~11,~13 on the red line might be a kind of pwm? does their spacing change with pressure and if so, how?

re: 20 volts, where is the zener?!? I'm not %100 on which wire you want. I don't quite get how one side of the injector can have higher highs and lower lows than the other, but for now it looks like you found a working signal (1-3.5 is sufficient for off and on to the atmega).

The atmega triggers on at ~2.5 volts and off at ~ 2.2 volts, so I'm not sure that the red line is registering. might need to amplify it or something (ugh)