OT: Why can't a petrol engine start itself?

[Archibald Tarquin Blenkinsopp]

You need to get completely away from any preconception of the engine and drop it down to the minimum.

As I stated before the pistons and crankshaft are a must, although someone might go further and remove the crank, but I really would think that this is taking projection of the design beyond reasonable limits.

Storage has to be electrical, as the remit is no starter motor, any external rotational device would by default have to be discounted, otherwise One would just be using a different pattern of starter motor.

Compressed air is an interesting possibility, but it would have to be applied to a flywheel/ turbine combination and thus not too far removed from a starter motor. Or it would have to be introduced to the cylinders in a timed fashion, in which case, One is better to go the whole hog and add the fuel and spark as well. The only logical conclusion to this is individually acting mechanically isolated valves and injectors along with spark generators and linear transducers to provide the precise positional feedback of valves.

Temperature, fuel, air mix and needless to say the crank position would need to be defined also, although there is an argument that to make life almost liveable for your AA patrol man, each piston would need it's position defining.

Best not to think in terms of an ECU incidentally, it encourages entry into the rut.

Try CPU instead :-)

AB

[tabbypurr]

sic sense. They were a mostly typical 1960s car with some mods to adapt the m to Russian use. For reasons that had nothing to do with their qualities o r shortcomings a lot of people talked a lot of b- about them.

I see you don't know a lot about Ladas. Moskvitches I don't know a lot about.

NT

[tabbypurr]

On Saturday, 24 March 2018 12:37:04 UTC, Archibald Tarquin Blenkinsopp wro te:

is in the right position gets an injection of fuel and air mix and a spark and stars the engine rotating, without the need for a starter motor? Espe cially 8 cylinder engines, surely one is always in the right position to ge t it going?

e valves even without it turning. You'd need some backup plan for when it d oesn't fire first go, which will be often.

You don't need anywhere near that level of detailed refinement just to get a cylinder to go bang.

NT

[Archibald Tarquin Blenkinsopp]

I certainly know enough about both to enable me to function effectively on a day to day basis.

I,m afraid I never considered a Moskvich as a serious motor, I was briefly considering the purchase of a Lada, they were amazingly cheap and anything used by taxi drivers has to have some damned good points, in particular becuase at the same time the Japanese had started to bring a lot of vehicles into the UK. [The home grown Leyland garbage was useless].

I am certainly not an expert, and Ladas [apart from the camshaft] didn't seem to have the long list of repeatable traits Leyland models sufferred from. But as I say I intended to buy one, so I did take a passing interest.

Anyway what do you want to know? I may be able to assist. I knew a lot of Lada owners and covered quite a few miles as a passenger. In fact come to think of it, all the owners swore by them. I remember serviceing was a big plus point, it was really cheap.

Ayway, I ramble, how may I help you?

AB

[Archibald Tarquin Blenkinsopp]

Oh dear, we really haven't been following have we :-)

No you dont.

You dont need a piston

You would need a cylinder although trying to get one to go bang would need careful consideration of its physical and chemical properties.

It would be a one way event.

It would be a cheap car to "run".

You have not only entered the rut, you have filled the rut in and sealed the top.

AB

[James Wilkinson Sword]

That's different, I'm needing the few hundred amps for the starter.

[James Wilkinson Sword]

I might try that if it annoys me enough. But all that happens at the moment (with a croc clip directly onto the battery post, no original connector), is sometimes the starter only turns round once then stops. I simply retry and it goes. Must be a lack of current due to the small area of contact with the pointy ends of the teeth against the battery post. I already changed it to a brand new battery thinking that was the problem (as I needed an extra old battery for other things anyway).

However I do remember having slightly loose round post connectors on my Peugeot (by accident), and while driving along the vibrations would make it lose contact momentarily which was enough to confuse the alarm while I was driving - the hazards flashed once which confused the driver behind me. Presumably something worse could happen.

I think if I had to change it I'd get a bigger croc clip - like the ones on the end of jump leads.

[NY]

"Archibald Tarquin Blenkinsopp" wrote in message news: [e-mail]...

Does the valve timing mean that if compressed air is applied to the inlet manifold, it will always cause one of the pistons (the one which happened to have its inlet valve open when the engine stopped) to turn the crankshaft

*forwards*, and never *backwards*? If the compressed air continued, would the timing cause successive cylinders to experience that pressure and therefore cause the pistons to move as if the engine was running normally?

If so, could that be used as a "starter motor" to turn the engine at a high enough speed to allow explosions (once fuel is admitted) to be self-sustaining?

Leaving aside compressed air... If you had a way of reliably triggering just

*one* cylinder to burn fuel for *one* power stroke, would that, in conjunction with the inertia of the flywheel, be enough on its own to move another cylinder through its inlet and compression strokes ready to "c*ck the trigger" for it to experience a power stroke?

[NY]

"Archibald Tarquin Blenkinsopp" wrote in message news: [e-mail]...

A cylinder without a piston isn't much use to man nor beast, because it will not provide power to the wheels. And, of more immediate relevance, it will not set up the next cylinder in the sequence (and then the next after that) to go through a power stroke. But as you say, a closed cylinder with the right fuel/air/pressure/spark conditions will ignite - and then probably explode because the high pressure caused has nowhere to vent to (as it would if the pressure moved a piston).

Normally, you set up the conditions for a power stroke (fuel and air in cylinder, at high pressure) by running the engine and letting the other pistons turn the crankshaft so a given cylinder undergoes first an induction and then a compression stroke.

You could mimic that by having an auxiliary high-pressure fuel-and-air system which blows high-pressure fuel/air into the cylinder (replicating the effects of induction followed by compression) and then apply a spark. You'd probably need to do that in several cylinders in succession until the explosions were happening fast enough to be self-sustaining.

Think of starting a car using the starter motor. It usually takes a second or so before the engine fires, and therefore each cylinder probably goes through several power stokes before the engine has started. Now on modern cars with an ECU, that may be deliberate: prove that the engine is turning faster than some threshold before allowing fuel in and/or turning on the spark. But in the days before fuel injection and ECUs, fuel/air mixture went into the cylinders right from the first movement of the pistons, and a spark occurred right from the start too - but even if each cylinder fired, those sporadic explosions would probably not happen fast enough that they keep the engine turning - that only happens when the starter is turning the engine fast enough for the process to be self-sustaining

It is this "fast enough" concept which may prevent one single isolated power stroke being enough to get the engine turning unaided, and thus this may be the reason why instant-start has never been possible.

[Dave Plowman (News)]

Not so. You had to waggle the advance retard lever.

[Dave Plowman (News)]

You can run with an enormous amount of ignition advance if you keep the load on the engine low.

[The Natural Philosopher]

Just about, yes.

If you look at some old aircraft engines starting, thats about how it works. one pop and that kicks it into pop two, and then half the cylinbders are popping and than the thing starts up.

[Dave Plowman (News)]

Depends on engine design. Not all are so called interference types where the valves could hit the pistons if mistimed.

[Dave Plowman (News)]

There days, absolute crank position is calculated using a multi-tooth wheel, with a tooth missing, mounted on the end of the crank, or built into the flywheel. If you wish to know cylinder phase, you also need a cam position sensor. But that doesn't need to be so sophisticated.

[James Wilkinson Sword]

Is it legal to carry a retard in your vehicle?

[James Wilkinson Sword]

So your engine only fails due to a timing belt snap if you happen to be flooring it at the time?

[Dave Plowman (News)]

Sigh. You seem not understand the difference between ignition and valve timing. Why does that not come as a surprise?

It depends on the engine design if it will come to harm when the timing belt breaks. Although most these days will. But you could buy a decent make that uses a chain rather than belt.

[Mr Pounder Esquire]

Prick

[Mr Pounder Esquire]

Asks the prick who was incapable of changing the oil in his car. He said, "The sump plug could be all rusted up and could snap off".

[James Wilkinson Sword]

I have no interest in why my complicated engine won't run. They should all be electric motors in this century anyway.

So they've designed them to be worse?

They should all use a chain. How much does a chain cost?

And I buy whatever I find in the used car ads. Only fools buy new vehicles and lose half their money in depreciation in 3 years.