Wouldn't it be possible to design a petrol engine so whichever piston 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? Especially 8 cylinder engines, surely one is always in the right position to get it going?
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? Especial ly 8 cylinder engines, surely one is always in the right position to get it going?
Yes indeed. But with too many ifs. You'd need to be able to control the val ves even without it turning. You'd need some backup plan for when it doesn' t fire first go, which will be often.
NT
About time we got electric motors in cars.... I guess it's just the batteries that are shit.
Yes, very easily, although fuel would have to be injected into the appropriate cylinders in the correct sequence.
A few more sensors and a bit of number crunching in the EMU might do it.
Valve, fuel pump and injector operation must be mechanically independent of the drive, so if for some reason the mixture failed to ignite over two or three cylinders it would be time to lift the bonnet and gaze in until that nice AA man came with a tow rope. Or unscrew the plugs in the cylinders that were injected, blast out the condensed vapour and try again.
As most engines are designed to run and drive something rather than just start, efficiency at starting will invariably give way to that required to get the thing to run.
I seem to recollect that the other side of the design process saw some fishing vessel diesel engines that had to be started by an Engineer going into the engine room with a blowtorch to preheat the cylinders.
It's a damn good job that the early minis didn't have diesels or it wouldn't just be HGV drivers doing their burning oily rag performance :-)
AB
Early Rolls-Royce cars can often be started "on the switch", described here by one of the real experts:
***** The other use of the ignition control is to amaze people by "starting on the switch". In that case, when the engine has been stopped for a short time, as when filling up with petrol, if you switch on the ignition and move the ignition control down its quadrant, watch the ammeter for it to show the contact breaker breaking (zero amps to about 4 amps discharge) as you move the lever. If you wiggle the lever to cause several make and break cycles, the engine may start. Murphy's Law is that the engine has stopped at a point where the breaker doesn't break, though. Generally you should not do this trick with later higher compression engines; it was, however, a normal starting technique with a trembler coil on early Ghosts, and is aided by the action of the governor on Ghost, Phantom I and early Phantom II, because when you switch off the engine, as the revs drop, the governor opens the throttle so that there is plenty of mixture in the cylinders. On a small hp RR (e.g. the 20hp), the technique works better if you set the mixture a little rich and the idle a bit fast before switching off. *****and you don't even need fuel injection. But you do need a starting handle, in case the engine has stopped in the wrong place.
Post Brexit, Jeeves can have a few zero hours contract peasants in the boot for starting purposes.
Times have moved on from starting handles.
AB
So there's no way I could do this on a modern car? Turning off the ignition while pressing the gas pedal for example, then turning the ignition back on? I don't think it would even try to go. I assume the ECU doesn't make the spark happen unless it thinks the engine should be running?
On Friday, March 23, 2018 at 7:41:24 AM UTC+11, James Wilkinson Sword wrote :
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? Especial ly 8 cylinder engines, surely one is always in the right position to get it going?
Oh yes, it is like Big Bang happening, "timing" has to be perfect for a sta rt! A little late or early it is all miss.
On Thu, 22 Mar 2018 23:55:25 +0100, Peeler
The ECU would need a few tweaks to change it's mode of operation, in fact an almost total rethink would be needed of the timing functions, along with the need for additional sensors as the camshaft would no longer be a requirement.
Pressing a gas pedal with the ignition back on is a nice thought but would be about as relavant as control shift break is to an Ipad.
If you are dropping down to that level of practicality, forget it. An engine that is optimised to start in that fashion would not be a realistic power source anyway. Even with modern diagnostic equipment there are a lot of engine components replaced in error before the true problem is found, so something that consists of literally hundreds of sensors and transducers that all have to be related to the rest in a timed sequential fashion without a common mechanical coupling would be a nightmare for any garage mechanic or bill payer.
The running costs would also be eye watering as all the valve operation would be electrical.
Long wave would definately be out of the question on the wireless also :-(
AB
On Thu, 22 Mar 2018 23:57:29 +0100, Peeler
The right mixture in more or less 33% of the available cylinders. One go only!
A bit rough for the poor old Honda 125cc motorcyclists, they would really feel left out :-(
AB
Well there would be an awful lot of stresses involved in doing this from a standing start, and what happens if the engine will not turn over, does the engine blow up? Having said that I'm sure in history I've heard of engines designed like this and I suspect the reason we don't have them is that there was a serious problem! I'm sure you are being semi trolling here, but it is something I have to admit I pondered about when I was young. Brian
No what you need is akeep fit car. The passengers all have pedals and this winds up a clockwork motor which is used to turn the engine over instead of the starter motor. It can also be used during the need for a little more power, making sure not to run the clockwork down when the driver is the only person in the car was a problem with this design...:-) Brian
You'd have to inject compressed air tho.
FWIW, one of the current start/stop systems (Mercedes IIRC) keeps track of where the pistons in order to aid restarting.
"Archibald Tarquin Blenkinsopp" wrote in message news: snipped-for-privacy@4ax.com...
That is effectively what glow plugs do: pre-heat the cylinders to help the fuel ignite before the combustion has heated the cylinders to a temperature at which ignition will occur.
I'm not sure why glow plugs are not *always* needed in a modern HDi diesel engine.
My Peugeot developed a problem with the glow-plugs. Normally if a glow plug fails, the engine "limps" on three cylinders and you get acrid blue exhaust until the combustion in the neighbouring cylinders has heated the cold cylinder by conduction after a few seconds.
But in my case the engine started perfectly and then failed under load after running for about 5 mins. The garage (both my local one and the Pug main dealer) told me that with modern engines, the glow plugs aren't always needed to fire the engine - except in very cold weather - and that their main purpose in warmer weather is to trigger the DPF to burn off the soot that it has captured. The loss of power was the engine management unit killing the engine because of the glow plug fault. Fortunately the engine would always restart after a couple of seconds and after a couple of restart/die cycles it would run perfectly for the rest of the day, even after a long rest which would have le the engine cool down. Thankfully it's now fixed, though at a hefty cost - for some reason on my car there is a very large stripping-down labour cost to replace the glow plugs (they also warned me that I'd have to pay this even if the plugs turned out to be OK on inspection). I though glow plugs were screwed into the cylinder head roughly in the same place as sparking plugs in a petrol engine, so it would be a five-minute job to remove them for inspection/replacement.
Maybe start it with just the compressed air alone? A short burst.
No ignition sparks with the engine stopped.
To start that old Rolls, you effectively moved the distributor round so the points opened. Manual control over ignition timing disappeared getting on for 100 years ago.
On Thursday, 22 March 2018 21:21:07 UTC, Archibald Tarquin Blenkinsopp wro te:
in the right position gets an injection of fuel and air mix and a spark an d stars the engine rotating, without the need for a starter motor? Especia lly 8 cylinder engines, surely one is always in the right position to get i t going?
all electrical is not a problem now
how do you get 2 or 3 goes out of a stationery engine?
thats what the valves are for
not really, IC engines don't need efficiency to start.
that was standard practice in the days of single speed semi-diesel glowplug engines. I'm trying to remember what they were called.
NT
s in the right position gets an injection of fuel and air mix and a spark a nd stars the engine rotating, without the need for a starter motor? Especi ally 8 cylinder engines, surely one is always in the right position to get it going?
tart! A little late or early it is all miss.
It doesn't need to be anywhere near perfect. If the spark happens half way down the power stroke you get somewhere vaguely around half the power out.
NT
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