Technical Becky's timing belt - the ongoing saga!

[s130]

Decokes? What are they? Really enjoy your posts s130. Thank you
Regards
Jock

Many of the older cars got heavy build up of carbon baked onto the cylinder head. This was normally detected by "running on" after the ignition was turned off. The hot carbon would retain heat, even glow and take over ignition from the sparkplug. Only solution was head of an fully decarbonise ("decoke") the cylinder head.

 

[Pugglt Auld Jock]

Many of the older cars got heavy build up of carbon baked onto the cylinder head. This was normally detected by "running on" after the ignition was turned off. The hot carbon would retain heat, even glow and take over ignition from the sparkplug. Only solution was head of an fully decarbonise ("decoke") the cylinder head.

Sorry s130 that was intended in a joking way. Actually the first decoke I ever did was on my 1936 Morris 8 as a teenager and I did it with the lawnmower tools I found in the machinery shed! Metal head gasket which I reused with some Stag jointing compound and away she went! It was the 2nd car I ever owned, the first being a 1930ish Morris Minor (didn't look anything like the Morris Minor we are familiar with) bought it from the scrappie for 5 pounds 10 shillings around 1960 or so. It used up most of my saved pocket money but did include delivery to my dad's house. I was too young to hold a license but we lived in the country and had 2 fields which I used to race around in until one day it blew up in a cloud of steam. Took the head off to find a pinhole in one of the bores letting water in! I think the scrappie gave me 10/- for her but I remember he picked her up for free. The Morris 8 lasted a couple of years to be replaced by an 850 Mini when I passed my test.

Wish I had them both now! The Mini would occasionally do that running on thing. It didn't really "run" it was more that it would "kick" over 2 or 3 times after you'd switched off. Probably, I'm ashamed to say, because of the merciless thrashing I'd just handed out to it trying to keep up with my friends 107e Ford Prefect!

 

[s130]

Suggest we move further discussions about anything other than Panda Cam Belt Timing somewhere else. Possibly Technical (Tech Talk) ?

 

[Pugglt Auld Jock]

No objection to that. Run out of things to say for now though!

 

[DaveMcT]

Dave Vizard's video presentations on YouTube are well worth watching. He's mostly talking about Austin Mini A Series engines but the basics are the same. I believe he says there is a point on the inlet valve opening where even though it's "cracked" open the flow is still negligible. I dont know what that point is but it will be mentioned somewhere. Exhaust valves however will always lose gas when they lift off the seat. In fact, most of the gas has gone and dropped the chamber pressure to (up to) 50% vacuum before the exhaust valve is anywhere near closing again.

That pressure drop helps to draw in the next inlet charge and is why the exhaust valve stays open after the inlet opens. It also maintains a continuous gas flow. An inlet valve with very light springs would actually deliver a considerable valve overlap, but it would not be controllable at high revs so it has to be done by the cams. That said, 2 strokes often use inlet reed valve which are atmospheric valves. Has anyone tried them in a four stroke?

Vizard also says that if you look at the area under the curve of a valve open time, the peak above 50% is a much smaller percentage of total. You will get more performance by concentrating on the part open gas flow than on peak gas flow. He went on to prove that with his vacuum flow bench testing.

Here's a interesting valve system though to be really clever it needs separate control of inlets and exhaust so the overlap can be altered according to engine speed. The authors seem to have entirely missed the point about why the inlet and exhaust valves overlap.
https://waset.org/publications/9997...haust-mechanism-in-internal-combustion-engine

Konisegg is now building "free valve" engines for ordinary cars. There is no camshaft just hydraulically opened valves. The valve stroke and timing is all controlled by computer. Just like Fiat's MultiAir, there is no throttle valve. Unlike the Fiat there is no camshaft. It can even run as a two stroke or miss out strokes to run more efficiently at low power. I may also not need a starter motor as fuel can be injected into the best positioned piston, valves closed and a spark fired.

http://www.freevalve.com

 

[Pugglt Auld Jock]

Suggest we move further discussions about anything other than Panda Cam Belt Timing somewhere else. Possibly Technical (Tech Talk) ?

Dave, at s130's suggestion I'm going to continue comments in "tech talk".