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V8 with no Cam or Valves

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Old 02-23-2004, 01:33 PM
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Quote:
Originally posted by Reed Jensen
... two stroke technology took a step ahead with a movable "window" in the exhaust port to change the timing... ( yamaha TZ motorcycles)
Works great, but the system has a couple of flaws. Yamaha engineers have had a hard time keeping the powervalve retaining pins locked in, when they fail they fall down into the cylinder taking the engine with it. Also, the powervalves build up carbon and if they aren't cleaned at least every so often they can jam up and again pop the engine. Even though they have problems, the system still makes impressive power.
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Old 02-23-2004, 01:43 PM
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Quote:
Originally posted by SS930
Works great, but the system has a couple of flaws. Yamaha engineers have had a hard time keeping the powervalve retaining pins locked in, when they fail they fall down into the cylinder taking the engine with it. Also, the powervalves build up carbon and if they aren't cleaned at least every so often they can jam up and again pop the engine. Even though they have problems, the system still makes impressive power.
Oh yeah.... but who is running two strokes any more? When was the last time you saw a two stroke bike? I haven't seen one on the streets in years.. I don't think they will ever meet current smog requirements.
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Old 02-23-2004, 03:37 PM
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Quote:
Originally posted by Reed Jensen
Oh yeah.... but who is running two strokes any more? When was the last time you saw a two stroke bike? I haven't seen one on the streets in years.. I don't think they will ever meet current smog requirements.
Yamaha is still producing engines that use this system. Their HO jet skis (1200 and 1300?) use this system. The same engines w/o the powervalves only make about 85% of the power compared to the models with them. As far as the bikes go, correct me if I'm wrong, but I believe the 2 stoke street bikes are still really big overseas (mostly in Japan). The reason they died in the states has more to do with popularity than it does with emissions requirements. Although those same models from the 80's (like the RZ350) wouldn't pass a current sniff test, the technology to build clean 2 strokes has been around for many years now... DFI systems will pass all of today's requirements with flying colors.
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Old 02-23-2004, 03:43 PM
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There's been Diesels running with rotory valves since at least the early 40's. The Fairbanks-Morse diesels used in WWII subs had rotory valves. The Viet Nam era Nasty Class patrol boats used 18 cylinder, aluminum block, rotory valved, diesels built in england by Napier.
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Old 02-23-2004, 04:14 PM
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So how did this guy get all those patents? He must have something new??
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Old 02-23-2004, 04:19 PM
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You can patent anything you want.. doesn't mean it works well... or will sell or make money... One of my friends has a patent on an ice cream scoop.... he sells them to Baskin-Robbins.. go to www.uspto.gov and do a search on anything.. you will be surprised at the sh*t that has a patent.
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Old 02-23-2004, 07:29 PM
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This design of engine has been around for a long time, the most notable being the Bristol Engine Company's Centaurus sleeve valve engine used in the Hawker SeaFury carrier-based fighter of the mid 1940's. I had the opportunity (or misfortune ) of working on these engines while restoring some of these fighters back in the early 80's.
18 cylinder radial (2 rows of nine)
3270 cid (53.6 litres)
2485 hp or [email protected] rpm with water/methanol injection
These engines have more thrashing parts insides than anything ever designed, but damn did they sound cool when we had them running right with good sealing sleeves and cylinders.
The following link has some cool pics of how this thing looks apart.

http://www.enginehistory.org/buckel_galleries.htm
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Old 02-23-2004, 07:32 PM
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This is the best layman's description I have comparing sleeve-valve engine design to poppet-valve design................



In a normal engine using poppet valves, the valves are opened by the camshaft pushing down on the top of the valve, often via a long pushrod and rocker taking the power from the crankshaft area to the top of the cylinders. The valve closes itself when the cam stops pushing on it, using a spring.
The problem with this system is that as the RPM of the engine increases, the speed at which the valve closes must also increase, and that requires a stronger spring. In addition the "perfect" design requires as large a valve as possible for easy airflow, but a large valve requires considerably more force to open due to the pressure against it inside the cylinder. These changes would require a stronger camshaft, and considerable energy to run it. At some "magic number" it would seem that all of the energy of the engine would go into the huge camshaft needed to push the huge valves and their equally huge springs.
The sleeve valve avoids all this. As the name implies, the valve is constructed as a sleeve, one that fits around the piston inside the cylinder. Several ports (holes) in the side of the cylinder replace the more normal intake and exhaust ports on the head. Similar holes in the sleeve open and close the ports like a poppet valve would, but do so by being rotated into position. The sleeve has a gear ring on the bottom that runs in a channel, and a small cut in the cylinder wall exposes the gear so that the sleeve can be turned.
There is no need for a spring in the sleeve valve, and the power needed to operate the valve remains largely constant with RPM so the system can be used at very high RPM, and with no penalty for doing so. Furthermore it does away entirely with the camshaft, pushrods and rockers, replacing them all with a single gear running directly off the driveshaft. For an aero engine this sort of simplification and weight savings is an engineer's dream.
Another advantage of the system is that the actual size of the ports can be easily controlled. This is important when the engine runs over a wide range of RPMs, because the speed at which the air can move into and out of the cylinder is defined by the size of the tubing, and does not vary linearly with RPM. In other words at high RPM the engine typically wants larger ports that remain open longer, which is very easy to arrange with a sleeve.
Less important advantages include leaving the cylinder head empty so the spark plug can be placed wherever is best, the valve is not being continually "hammered" into the port leading to rapid wear, and the exhaust's heat is spread evenly around the cylinder, rather than generating a hot spot on the exhaust valves. Hot spots in engines must be avoided, they can often lead to the destructive problem of knock. In the sleeve valve engine this is not an issue, so they can be run at higher compression.
The sleeve has one major disadvantage though, and that is that it can't be sealed well. In a normal engine the piston is sealed into the cylinder with rings, and after a "breaking in" period any imperfections in one is scraped into the other. The result is a tight fit. This sort of fit is not possible on the sleeve valve however, because the piston and sleeve are moving in different directions.
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