Wednesday, 18 August 2010
Written 17th August
Are dull. And tedious. And very, very slow. Which is not something you expect in Germany which is famous for its lack of speed limits on autobahns - not that that is an advantage in Jules of course, although I did consider a trip to the Nurnberg ring... ;). Well, relaxed about speed they may be but they do not deal with road works very well
Jules' triumphal visit to its ancestral homeland was less than exciting. No sooner than we got on the road than the traffic ground to a halt. And then craaaaaaaawled along. Not good for a little van that stalls if you let the revs drop - through, say, changing gear or putting your foot on the brake for example - and refuses to start again if the starter's hot and bothered. Will ended up pushing it for a bit, as it was just as quick as driving at the speed of the traffic and it gave the starter a chance to calm down. And some people did offer to help which was nice. The thing about a little van like Jules is that it is cute and people expect it to have problems because it is quirky and old so they most often do help. And much as I hate a) conforming to stereotypes and b) people casting aspersions on the reliability of my brave little van - which is very good really! - this is nonetheless quite nice of them.
We made it to a layby in the middle of the roadworks and decided to stop for lunch, before we ended up stopping traffic. Surrounded by other people with bonnets open, steaming engines and bottles of water - oh dear. It was quite funny watching people crawl past us and see their looks of concern at our imagined plight turn to jealousy as they saw the cup of tea and cheese sandwich in our hands whilst they were many long, slow miles from sustenance of any kind . I love my little home on wheels!
Back on the road when the traffic was moving only for it to stop again only a couple of kilometres further on. Dull, dull, dull. But fortunately just by a rest stop exit - again full of hot steaming engines - so we decided just to sit it out, with the radio on, where the only bit of the traffic announcements we could understand being a list of motorway numbers followed by "elf kilometers", "sieben kilometers", "ein-und-zwanzig kilometers" (sp?) All buggered then.
Still, we were ok in our little rest stop with tea and then dinner and tantrix, until much later on when we were able to get almost as far as the german side of the netherlands border late that night. Not quite the plan but we don't fancy trying to drive into any cities with a poorly van and if the roads stay like this, we'll never make the port in time.
In fact, by the time we had parked up in a layby on the outskirts of Bruges and were sat in a totally steamed up van in the gathering gloom with the rain beating down on us, listening to Just A Minute, it was almost exactly like a cold november evening we spent in the Cornwall the day before Land's End. You wouldn't believe it was still August! The rain was so battering that some of our window seals have started leaking again, something which hasn't happened since we bathroom sealed them all up in La Rochelle! There must be something about this particular brand of north-western european rain which makes it particularly penetrative.
Still all good acclimatisation for coming home :)
We discovered the other day that we had recorded copies of "Britain's Best Drives" - you remember, BBC series from last year where Richard Wilson follows the "Motoring Guide to Britain 1959" or some such publication, and drives round in a series of 1950's cars to see how they've changed. So we're watching some in preparation. The Yorkshire Dales episode we watched the other night was beautiful but I kept getting distracted by the fact that he was driving on the wrong side of the road... I'm sure it will all be fine...
We're suddenly seeing lots of UK cars here as well (actual UK cars with GB stickers unlike all the UK plated cars we saw in eastern europe which were all clearly being driven by locals - all R-reg which is a bit odd) but as we, and they, are not so exotic, surprised to see someone else who is english in such a remote/far flung/out of the way/unlikely place, or desperate for english conversation (or a combination thereof), there isn't the same incentive or compulsion to stop and chat.
We are very nearly home!
And back to the van for english lunch of boiled eggs and soldiers, accompanied by the melodious tones of Radio 4. Perfect.
A simple multimetre test has proved the problem is not the solenoid, so the starter motor is now on the van floor, and whilst he's got the battery disconnected - so no radio 4 :( - and is up to his elbows in spanners and emery cloth cleaning contacts, I'll give you that ecu update I keep promising. Although I will probably get interrupted every now and then to find, pass or hold things...
If you're not interested, skip to the bottom and hopefully by the time I'm done there will be a starter motor update!
< ECU UPDATE >
So, ecu, where were we? Actually, I can't remember so here's a quick recap of the story so far.
Jules is a fuel-injected US import. But, they didn't have computers in those days - not small diddy engine bay sized ones anyway - so all the sensors and controls were done with analogue electronics and mechanical hardware. This is actual space-age technology!
For Jules, this means that the fuel input requirement is a function of airflow. Airflow is controlled by the throttle* and measured by a flappy paddle which moves with the volume of air and pushes a slider along a track, into which is built a cunning variable resistor. Literally the fuel map is etched into the hardware with lazers. The resistance changes depending on whereabouts on the track the slider is. The ecu responds to the voltage and squirts an appropriate pulse of fuel into the cylinders, which is adjusted according to the temperature of the air and the temperature of the engine.
Now, when we set off, we had three problems. Well, we had several problems and an uprated cam shaft may not have helped. But, the three main problems were:
1) a leaky throttle which didn't close properly - so it was always having some airflow when you didn't want it and over revving,
2) air leaks within the engine - so the airflow meter wasn't actually measuring all the air which was going into the engine so the fuel mix was wrong anyway, and
3) worn area or holes on the physical
fuel map - so at some airflows, especially 20mph in second gear - just what you need for pulling away, motorway queues, town centres, corners, slowing for traffic lights etc etc - it suddenly doesn't get a proper voltage signal and bunny hops down the road.
All of this meant we weren't very fuel efficient and, more importantly, were more often than not running with an incorrect fuel/air mix and being either too rich or too lean is bad for the engine.
So, once we were underway, Will set about trying to do something about this.
The first step was to replace the throttle - which he did in La Rochelle for one out of a citroen saxo which we happened to have kicking around (as you do, don't ask, it will be replaced for something bigger and more suitable when we get home). He then set about plugging as many air leaks as he could find by various means, including new hoses, corks, bike inner tubes, tape and various types of goo.
He then fitted a new airflow meter (from an Ford) inline with the old one (which necessitated a new performance airfilter as well) and plugged a lamda sensor into the exhaust pipe just before the silencer.
The plan was to create a new mini ecu using an arm development board he 'borrowed' and a pick and mix selection of electronic components scavenged from the electronics shops of europe and eventually replace the old airflow sensor. Basically using a centimetre square chip with a level of processing power which would have required a computer the size of the van dealership to brute force override the original hardware. The original designers would be flabbergasted.
As you know, this worked. To a point anyway. We ended up in Poland with something which did control the fuelling but Will discovered that in the process that he needed more than the two inputs he had, at least enough to process throttle position, engine speed, lamda and airflow, to make it work properly
But with no possibility of a rearchitecture at that stage, Will took delivery of a fancy new circuit board from an ex-colleague who is also on the trail of creating his own ecu, this one as an open source project designed to be applicable for cars with up to 12 cylinders!
This shiny new board has a squillion analogue and digital inputs and an inlet manifold air pressure sensor** and pages of complicated equations to convert air pressure readings to appropriate fuel input at volumetric efficiency. Hurrah!
This means that Will can hook up the following :
- two temperature sensors (raided from a metro if I recall correctly) which are now calibrated (thanks to the fridge and the kettle we have on board) and which measure air temperature and cylinder head temperature***,
- the air pressure sensor,
- the lamda sensor, and
- the rev counter he has designed which reads the spark frequency off the distributor to calculate engine speed,
Will's task from Adam was to put together the fuel injector drivers from the components provided and write the driver software. Which he has done. He's also adapted a lot of his 'hunting' code from the old project which adjusts the fuel according to whether the lamda reading is rich or lean.
The problem now is integrating into our engine bay.
The natural next step would be to connect the existing engine up to some diagnostics and measure the fuel injector pulses for given revs, copy that into the new software, hook up the new ecu and simply tune it.
But, as he keeps reminding me, Will is doing this on the road without the benefit of a garage or proper tools. By choice, as I keep reminding him :)
But this means he is without the benefit of useful things like an oscilloscope. So he is currently using the new ecu just to replace the old airflow sensor - so using all the temperature, pressure measurements and complicated equations to determine the fuel required - and, by using a variable resistor to change the output voltage, turning the output from it into something which looks like the output from the old sensor for the same fuelling and feeding that into the old ecu. A bit like having an external heart pump doing the actual work whilst your old heart is still in there before going in for the big transplant manoeuvre.
But things are never that simple and there are always bugs in your code, especially if you don't have any way of bench testing it. So whilst we've been driving along on these nice flat roads where Will can hold the engine at a relatively constant rpm (which is more difficult than it sounds as we don't actually have a rev counter on the dash for reference), I've been in the back with the 'stuff' - there are wires everywhere coming out of the lid of the engine bay like rainbow coloured spaghetti! - twiddling the variable resistor until the voltage output from the new ecu is the same as that which is coming off the old airflow sensor (there are technical reasons why it can't do it by itself which I have forgotten) then Will is pulling the knob which switches the engine to using the input from the new ecu - he's wired up the defunct rear screen demister knob for the purpose, which is much, much better than having to duck dive into the engine bay and slide my morrisons miles card between the contacts of the old sensor to physically disable it, which was the previous solution! - and we see what happens as it hunts for perfect lamda at that rpm. Exciting stuff! There have been some code rewrites required along the way which have been dictated to me and then reprogrammed into the chip - I am quite the expert now! - but I think it works! Well the graphs I am creating seem to be showing it doing something which Will says is 'the right thing' so there we go! Just need to create some kind of map for the whole rev range now....
But we have run out of motorway for now. So I'm not sure what happens next.
But there we are, progress!
And on the subject of progress, I need to go hold the starter motor and pass some spanners, hang on...
< / ECU UPDATE >
Hurrah! Success! The starter motor is back in situ with all its internals back internally, all its contact surfaces cleaned and all its wires hooked back up and not only does it work, it is much more enthusiastic than the low pitched grumbling we were getting before! Hurrah! It will need a new bearing in it at some point soon but should last at least until we get home. One less think to worry about.
And perfect timing. Just in time for the news, Cabin Pressure and The Archers on Radio 4 then we can go into town and celebrate our last night on foreign soil.
Mmm beer. Sweet, sweet Belgian beer.
* Engine Mechanics 101:
1) The throttle is connected to the accelerator pedal. You press the pedal, the throttle opens = more air flow into the engine therefore more fuel required = higher volume of air/fuel mix into the cylinders = bigger 'bang' in the cylinder to drive the piston up = faster engine. Took me a while to understand it was all about airflow and not that the accelerator pedal made the engine pixies cycle faster...
** Engine Mechanics 101:
2) Modern fuel injection systems use inlet manifold air pressure and temperature to determine fuel requirements, not airflow. This brings us kicking and screaming into at least the 1980's!
*** Engine Mechanics 101:
3) the metal lump of engine which houses the inlet valves into which the fuel is squirted.
With love for now from Becky, Will and Jules on Wednesday, August 18, 2010