[Hometune]

The system you are talking about is the one fitted to all vehicles now and why we are having so many queries about faults and breakdowns. The reason is that you need expensive diagnostic equipment to stand any chance of finding the fault.
As the ECUs are all linked, a fault in one can be transferred down the line to another e.g. engine management light on but the fault is in the ABS ecu. Unfortunately, this technology is so advanced that drivers have no understanding and why some faults are so difficult to fix.
I have copied the following to give an idea of what it means in nice simple terms ;)

CAN Bus is a multiplexed wiring system used to connect intelligent devices such as Electronic Control Units (ECU's) on vehicles, allowing data to be transferred in a low-cost and reliable manner. CAN means 'Controller Area Network' and was developed by Bosch in 1980. Most new vehicles use this system and it is becoming increasingly difficult to install after-market products without using a CAN Bus Interface.

Why is this system used?

The reasons for the vehicle manufacturers using CAN Bus are:-

(a) Significant reduction in wiring leading to:-

(i) Significant reduction in manufacturing cost and hence retail cost.

(ii) Reduction in weight resulting in improved fuel consumption.

(b) Reduced number of interconnections hence improving reliability.

How can I find the CAN Bus Wires?

It is easy to identify the wiring as it is just a twisted pair of thin wires. These will be found all over the vehicle - sometimes in with a conventional main loom. The wires are called 'CAN High' and 'CAN Low' and it is important that any interface is connected correctly to these wires.

So much for progress. :(

[Snowball]

Considering the increased number of cars on the road, I believe that they are now generally a lot more reliable.

For many years, like many others, I used to service and repair my own vehicles; rebuilding engines, gearboxes, etc. Now retired, I prefer to have the work done at my dealership.

I am engineering trained, cars were a hobby, and I think I can claim to have been very proficient in my work on cars.
However, many car owners still do carry out their own repair work on their cars, and not all of them end up with the car in a safe state of repair.
Latest technology has greatly reduced this practice, and is that a bad thing?

Strict legislation has been introduced for DIY electrical work in the home, yet a complete novice can do whatever DIY work he wishes on his vehicle, and then go hurtling along roads among other vehicles.

At least, the difficulties for DIY work due to the complexity of the modern car is going some way towards doing what the government has so far failed to do; which is to limit how much DIY fiddling about can be achieved without immobilising the vehicle.

[Rolebama]

For what it's worth, I used to come across a lot of unsafe cars due them fixed by 'a friend'. Funny, these same people wouldn't let me dismantle their video player/recorder even though I guaranteed it would still work after I re-assembled it. People generally will not read their handbooks, and let almost anybody 'play' with their cars. The best part for me though is when I ask what garage these 'friends' work for, it's usually Blockbuster, Domino Pizza or some such.

[wagolynn]

Originally Posted by Hometune

So much for progress. :(

Can’t say I have come across that so far, sounds like trouble.:eek:

From memory the AB system would have controlled the power to a 'normal' ignition setup or the power supply to an ECU, with no data link between the two. The problems you describe are just poor design. But that sounds about right for cars.:(

[Snowball]

I can't agree that car reliability has not come a long way in the last fifty or so years.
I can remember when a car owner (we didn't have "keepers" then) would proudly claim he had managed 30,000 miles out of his car without a rebore and/or cylinder head top end overhaul. And my 9 HP car struggled to achieve 30 mpg. Even with clear roads, journey times took much longer, because doing 50 mph over anything greater than a short sprint was thrashing it.
I can remember an advertisement for Viscostatic oil, where the AA oversaw the stripping down of an Austin saloon, circa 1960's?, with the proud boast that it had shown little wear after 155,000 miles. Nobody sees that as unusual anymore.

Admittedly, you cannot do running repairs with a hand toolkit and bits of wire on the modern car. But they go on a lot futher in both time and distance without needing attention.
From my early motoring days, and in spite of the enormous increase in car numbers and mileage covered, I see far fewer breakdowns now than I did in those days.

[wagolynn]

But it took legislation to force the car manufacturers to this point – cars must not pollute for 50,000 miles – I don’t think it says it that way but that is what it boils down to.
I cannot think of one car that is a decent piece of engineering. The brief is to get from A to B in safety, quickly and efficiently, I cannot think of one current car that will. All certainly fail on the efficiently bit, yet it is not all that difficult to do. But it will not sell cars I suppose.

[Hometune]

Originally Posted by wagolynn

Can’t say I have come across that so far, sounds like trouble.:eek:

From memory the AB system would have controlled the power to a 'normal' ignition setup or the power supply to an ECU, with no data link between the two. The problems you describe are just poor design. But that sounds about right for cars.:(

The claims in my view are not exactly truthful about the CANbus system. The main one is supposedly to reduce weight of the old fashioned harness. But does it?
If you were to remove the following from, say a BMW, would it be lighter? There are the 4 electric window motors, 5 central locking motors/solenoids, climate control pack, airconditioning radiator, condenser, pipework and aircon pump (very heavy), electric motor for sunroof and all the other non-essentials that the German manufacturers say we demand in our cars today. Do we? I don't. I can open my window manually. I can reach across to unlock the doors. I can open a window when its hot (just like at home where I don't have aircon so why any different in a car?). I can move my seat back and forward with a lever. I don't need to burn my backside with heaters in the seat squabs. I can push a lever and the sunroof opens. So, who does need all these 'extras'?
On top of all the above parts there are the ECUs which operate them, and the instrument panel, the body control module, the seat memory positions, the door mirrors (I kid you not), etc etc. And all these ECUs have to be manufactured which is a waste of resources.
Unfortnately, the motoring public is being taken for a ride by the manufacturers who dictate what we should have in the car. Once we have been accustomed to these 'luxuries', it is very difficult to get people to go back to simpler machines.
I do accept that ABS and airbags are necessary for safety but the rest can be thrown in the bin. All the research and development of these unnecessaries would be better spent on making the actual car better e.g. a suspension system that can cope with the potholed roads. Now that would be progress.

[wagolynn]

That sounds like a man that has to fix em. Agreed though novelty for the sake of it.

[Snowball]

Originally Posted by wagolynn

But it took legislation to force the car manufacturers to this point – cars must not pollute for 50,000 miles – I don’t think it says it that way but that is what it boils down to.
I cannot think of one car that is a decent piece of engineering. The brief is to get from A to B in safety, quickly and efficiently, I cannot think of one current car that will. All certainly fail on the efficiently bit, yet it is not all that difficult to do. But it will not sell cars I suppose.

In 2001, I bought a 1997 VW Golf 1.9 TDI estate. It already had 46,000 miles on the clock. This car gave me excellent reliability and service for four years (and I used it to tow my caravan during those 4 years), and then it was passed along to my son-in-law. Eight years later, he still uses it every day, and still takes it onto the continent, even though it has done over 120,000 miles.

I moved on to a VW Touran just over 4 years ago, and have recently changed to my second Touran. In both cases, I have towed/tow these cars with my caravan, and took the previous one on a 7-week tour around France.
The car is economical, at 30 mpg plus with a caravan in tow, and typically 50 mpg plus when solo.

I only changed to my second Touran because I wanted a properly stowed, full sized spare wheel. A bit pricey perhaps, but it's my money.

Sorry, but you must be choosing the wrong cars, or just had a lot of bad luck.

[Rolebama]

Hometune, I agree wholeheartedly about chucking that lot in the bin. I would swap the lot for quarterlights.

[wagolynn]

Originally Posted by Snowball

Sorry, but you must be choosing the wrong cars, or just had a lot of bad luck.

If you do the number crunching then the best efficiency will come from a Compression Ignition engine. Why are we not using them? Also max efficiency means minimum pollution. :confused:

Looking at development: VW/Audi went to direct injection for petrol, but that only brings petrol on a par with diesel, at a high cost. Others have followed on the same development path.

Diesels in general have gone to direct injection for efficiency. Diesels will tend to have a longer engine life due to, more robust build to accommodate higher pressures, lower average revs and lower average running temperature.

I do not remember when the 50,000 miles legislation came in but it came in because of catalytic converters if that helps to fix the date.

[Snowball]

Originally Posted by wagolynn

If you do the number crunching then the best efficiency will come from a Compression Ignition engine. Why are we not using them? .

We do use them. That is what a compression engine is; diesel.

[wagolynn]

Originally Posted by Snowball

We do use them. That is what a compression engine is; diesel.

A common misconception, a CI engine is very different, fuel and air is premixed. Mixture is ignited by compression but on low power there is no hot flame. Therefore very small amount of heat lost to the cooling system. For a fuller description please look at an earlier post on this site General Driving Discussion / VED rates / Page 2 / Post #12.

[Rolebama]

No, sorry, Wagolynn, a diesel is a Compression Ignition engine. The type you refer to is also a Compression Ignition engine. Just different fuelling systems.

[Snowball]

All types of internal combustion engine reply upon the compression of gases to create a controlled expansion of those gases (fuel plus air mixture) when they are ignited.
But, commercially at any rate, the only fuel/air mixture that relies on compressive forces to achieve ignition is diesel.
There will be other elements capable of achieving compressive ignition (e.g. model aero engines; I used to fly these), but on a cost/quantity basis they are not economically practical.

[wagolynn]

No the diesel engine compresses air then injects fuel, this creates a flame within the combustion chamber which is many times hotter than is required, hence the heat loss due to radiation from that flame and also the particles of ‘soot’ which are lost fuel.

With a CI engine because the fuel (any fuel that can be mixed) and air are premixed, when the mixture is ignited the energy is evenly distributed into the air. There is no flame or flame front just an increase in temperature of the air and products of combustion, hence less heat loss to cooling and more useful work from a given amount of fuel.
So we would have an engine that mechanically is the same, no major changes in production, more efficient, just as drivable.

Chrysler has one car in the states with a compromise engine. It is basically a petrol engine that runs in CI mode in the mid range saving about 15% (they claim). But looking at their development of this engine they appear to have set off along the (in my view blind alley) charge control path and stumbled into CI along the way. I find it disappointing that manufacturers cannot see the wood for the trees.

One of the interesting spin offs would be that, there would be very little disadvantage in having larger engines fitted in vehicles but with limited fuel input. This would give low working temperature in the engine, high efficiency from less waste heat, high torque hence fewer gears lower cost, longer engine life. Perhaps the latter is the reason why the industry is not interested.

Yes model aircraft engines, commonly referred to as diesels, were CI engines. They were all 2 strokes. Happy days though probably high on dope and ether!
:D

[Rolebama]

Wagolynn, just for clarification. CI engines come in different guises. There are two-stroke and four-stroke versions of them. It is how the mixture is ignited, and not how the fuel is delivered that makes them CI. They can be run on a variety of fuels. LPG probably being the most popular 'alternative' fuel. An attempt was even made to run a 'diesel' engine on coal dust years ago, and although it was actually adopted, it was not very efficient because of the metering problems involved. As to the low heat loss, this is why I think there will be problems putting the engine in a car. It is very difficult to get people to accept that an efficient CI engine has no 'excess' heat to spare for creature comfort. (Some manufacturers are already using 'glowplugs' in the cooling system to help engine warm-up.)
**Deutz, I believe, pioneered a set-up for diesel engines which was a hybrid between two and four-stroke, with just an exhaust valve.**

[Snowball]

I have been scanning several authoritative articles on Google. I have to concur with Rolebama on this.

The subject matter for Compression ignition engine technology (CIET) always comes back to "diesel".
As Rolebama says, compression-ignition is the principle of the technology, whereas how the fuel is added to the air is dependent on the methodology.

Where direct injection is used, the fuel is injected in atomised form into the hot air before the piston reaches maximum stroke. This atomisation is achieved at something in the order of 25,000 psi, so this method of the distribution of the fuel/air mixture is probably more efficient than it being mixed at lower temperatures outside the cylinder. I think the improved mpg increases and reduced CO2 emissions obtained by direct injection have proved the point.

For over eight years, my own vehicle has been a 1.9 TDI and in the same make of vehicle. I am now on my third vehicle and the fuel consumption/CO2 emissions have improved each time, without foregoing power output. And I believe they have not yet reached their limits for further improving the efficiency of this engine.

[wagolynn]

Originally Posted by Rolebama

Wagolynn, just for clarification. CI engines come in different guises. There are two-stroke and four-stroke versions of them. It is how the mixture is ignited, and not how the fuel is delivered that makes them CI. They can be run on a variety of fuels. LPG probably being the most popular 'alternative' fuel. An attempt was even made to run a 'diesel' engine on coal dust years ago, and although it was actually adopted, it was not very efficient because of the metering problems involved. As to the low heat loss, this is why I think there will be problems putting the engine in a car. It is very difficult to get people to accept that an efficient CI engine has no 'excess' heat to spare for creature comfort. (Some manufacturers are already using 'glowplugs' in the cooling system to help engine warm-up.)
**Deutz, I believe, pioneered a set-up for diesel engines which was a hybrid between two and four-stroke, with just an exhaust valve.**

But the difference is the fuel (usually in gaseous form) has to be intimately mixed with the air and evenly distributed around the combustion chamber. Diesels do not do that; they produces what the designers call a ‘torch’ a central fuel rich core. The core becomes short of Oxygen hence some of the soot, the rest is due to the droplets of fuel carbonizing before oxidization can take place.
In petrol direct injection, the fuel is injected and immediately volatilizes but forms a cloud which is driven over to the spark plug just as the plug fires. CI avoids all these problems.
I have not seen any diesels yet, does not mean they are not there, that have minimum water volume in the cooling system, I do know that there has been some development on thermostats to give tighter control.

[wagolynn]

Originally Posted by Snowball

Where direct injection is used, the fuel is injected in atomised form into the hot air before the piston reaches maximum stroke. This atomisation is achieved at something in the order of 25,000 psi, so this method of the distribution of the fuel/air mixture is probably more efficient than it being mixed at lower temperatures outside the cylinder. I think the improved mpg increases and reduced CO2 emissions obtained by direct injection have proved the point.

The improved MPG is due to the characteristics of a diesel engine, variable temperature combustion, as opposed to normal petrol’s constant temperature combustion. The atomized fuel is still droplets of diesel however small. On the web you should find articles from assorted universities clearing up the difference between different engine types. They make the point that CI is fundamentally different hence the different name.

[Rolebama]

It is true that if the fuel is injected in the way you describe, there will be soot formed in burning diesel. However, that is not truly the case. The compressed air reaches a temperature above which atomized diesel fuel will burn, at which point the fuel starts to inject. The fuel ignites, and the injector continues to inject fuel, adding to the 'burn', also causing 'swirl' in the combustin chamber so spreading the 'burn' more evenly. The point being to produce expanding gases over a period of time, not a simultaneous ignition of all fuel present, which causes premature wear, and you do not get a smooth power generation. Which is one of the drawbacks of having air/fuel mixture introduced into a CI engine. It will all try to ignite at pretty much the same time, causing more of an explosion. The 'burn' aspects of a diesel are dictated by the compression ratio, piston travel during combustion, camshaft profiles, valve timing and diesel injection timing, and if these are correct for the design of the engine, the soot produced is absolutely minimal.

[wagolynn]

Originally Posted by Rolebama

It is true that if the fuel is injected in the way you describe, there will be soot formed in burning diesel. However, that is not truly the case. The compressed air reaches a temperature above which atomized diesel fuel will burn, at which point the fuel starts to inject. The fuel ignites, and the injector continues to inject fuel, adding to the 'burn', also causing 'swirl' in the combustin chamber so spreading the 'burn' more evenly. The point being to produce expanding gases over a period of time, not a simultaneous ignition of all fuel present, which causes premature wear, and you do not get a smooth power generation. Which is one of the drawbacks of having air/fuel mixture introduced into a CI engine. It will all try to ignite at pretty much the same time, causing more of an explosion. The 'burn' aspects of a diesel are dictated by the compression ratio, piston travel during combustion, camshaft profiles, valve timing and diesel injection timing, and if these are correct for the design of the engine, the soot produced is absolutely minimal.

Combustion shock in CI is minimised by having the fuel so well dispersed, from what I gather it is no more than that produced by a diesel. The minimal soot is still said to be carcinogenic. It is still wasted fuel.

[Rolebama]

Every vehicle on the road produces carcenogens, either with its use, or as part of manufacturing processes. Every time an organization like Greenpeace or Friends of the Earth try to prove this, the Govt produces fallacious statistics to disprove them and shouts them down. As for soot, just watch the exhaust of the vehicle in front when it pulls away from a set of traffic lights a bit quick.
As to fuel dispersion reducing engine knocking, the most common methods of averting this usually involve reducing the efficiency of the engine, although water injection would probably be a solution if it could be sorted.

[Snowball]

Modern diesel engines and the fuels such as city diesel are actually cleaner than petrol, partly due to the greater economy achieved.
And benzene, which was added to petrol in order to get rid of the lead content, is actually a carcinogen. Specialists in their fields have made this point, but it fell on deaf ears.

[wagolynn]

Originally Posted by Rolebama

Every vehicle on the road produces carcenogens, either with its use, or as part of manufacturing processes. Every time an organization like Greenpeace or Friends of the Earth try to prove this, the Govt produces fallacious statistics to disprove them and shouts them down. As for soot, just watch the exhaust of the vehicle in front when it pulls away from a set of traffic lights a bit quick.
As to fuel dispersion reducing engine knocking, the most common methods of averting this usually involve reducing the efficiency of the engine, although water injection would probably be a solution if it could be sorted.

But knock is not a problem with CI. Knock is usually caused by the flame front trapping air/fuel which then explodes due to excess local pressure but in CI there is no flame front.

[wagolynn]

Originally Posted by Snowball

Modern diesel engines and the fuels such as city diesel are actually cleaner than petrol, partly due to the greater economy achieved.
And benzene, which was added to petrol in order to get rid of the lead content, is actually a carcinogen. Specialists in their fields have made this point, but it fell on deaf ears.

As far as I know the benzene carciogen after it is burned, correct me if I am wrong.

[Rolebama]

Wagolynn, 'But knock is not a problem with CI.' Knock can be a problem with any engine, and if there is no flame front, it can only be instantaneous combustion, which is not conducive to engine efficiency. It is the continuation of the flame front as the piston is on the down stroke which helps to smooth out the power stroke. Knock in most engines is caused by a localised hot spot, whether it be a carbon deposit, electrical spark or too weak a mixture not 'quenching' the burn.
'Knock is usually caused by the flame front trapping air/fuel which then explodes due to excess local pressure but in CI there is no flame front.' Again, if there is no flame front, there has to be instantaneous combustion.
I cannot see that as being good in any way.
According to: http://en.wikipedia.org/wiki/Benzene
Benzene is carcenogenic both before and after combustion. See Health at the bottom of the page. I do not endorse Wikipedia as I know it contains errors, but this makes sense.

[Snowball]

Off topic, Rolebama, but I found the Benzene and Health article interesting.
My father was in engineering, smoked and died of prostate cancer at the age of 69.

One of his hobbies for years was watch and clock repairs, and he used to regularly repair watches for family, friends and colleagues.
For cleaning the watch mechanisms, he used to swill them in a small dish which contained Benzene.

Significant? Who knows?

Sorry for the drift from topic.

Regards, Snowball.

[Rolebama]

My father was a welder in a brick making factory for years. Asbestos helmets, gloves, overshoes and aprons everywhere all giving off small fibres. Makes you wonder?

[wagolynn]

Originally Posted by Rolebama

According to: http://en.wikipedia.org/wiki/Benzene
Benzene is carcenogenic both before and after combustion. See Health at the bottom of the page. I do not endorse Wikipedia as I know it contains errors, but this makes sense.

Thanks for the Benzene info.

Ok humble pie time. The name I have been using is out of date. The fashionable name for the technology I was trying to describe is Homogeneous Charge Compression Ignition engines (HCCI). Said to have been accidently found in lab test of lean burn engines (1970), but model aircraft engines pre date that. Sorry about that guys.

However it is very difficult to access any really up-to-date information on what is going on because of commercial advantage.
GM are in production with the engine I mentioned before which runs in HCCI mode in mid range and saves about 15%.

In the UK we have a company called Oxy-gen Combustion Ltd who are deeply involved in HCCI they appear to be selling knowhow.

Looking at the research I could find (probably out of date now) the hang-ups appear to be; controlling the ignition point, slightly higher HC and CO. Both the later are due to, mixture next to cylinder wall being too cool and or isolated mixture in piston crown to first ring area. Though these are said to be well within the range of a catalytic converter. Figures of 20% to 30% fuel saving are talked of.

Exhaust re-cycling can be used; it has been tried as a means of controlling the ignition point without success. Also using different blends of fuel (on the run) to control fuel flashpoint has been worked on but is not practical (two fuel tanks etc.). The model aircraft engines; changing geometrical compression ratio works but is mechanically too complex.