maxflo777

Well Mr. Maximillian, you first told me to go to and do some reading, and then you come to say that you find me comical. I dont know about your tongue, but your fingers run on ball bearings. As if you know what I have or have not studied. What I've worked with and what I've havent.

In this thread - actually in many others too, I've seen you trashing anyone who doesn't think what you think - you are the only person that has insulted anyone and the only that has made the stupidest "arguments", if you can call it that, comparing apples to maybe rotten oranges, and then you come and you've been talking, cover yourself like a kid and say that you dont talk because you dont know, well guess what, defending it without an argument is ridiculous, pittyful indeed. Maybe you think you had an argument, even worst.

You even look naive believing a salesman that has not sold his product in 15 years to anyone.

Obviously not today, but Dude, 10 years ago GM, Ford, Toyota, Mercedes, and probably ten other brands had the money to not only buy that design, buy the designer, his children and grand children. An F1 team spends over$250,000,000 in their racing season, believe me, Ferrari shows a check to this guys for half of that, The whole company probably does a collective shit on their pants. I've given reasons leading to good arguments, you can agree, or not, but come back with one of your own.

This thing may work, who knows, but everything points in the other direction when you consider the common racing poppet valve, that is a fact that you only look childish if you deny. I have no problem with being wrong, I've been wrong before, and I would love to be able to take that valve out of the way, but I wont just believe the first crap that apears in front of me becouse someone says its good or it looks cool if every single physical characteristic it has says the contrary.

Get your arguments straight. Kid.

DP-buggyboy

iTrader: (1)

Guys, use the PM button if you want to argue.

Even if some ideas, concepts, or information may not be right, proven, or were complete failures in the past, it still makes us think - and great things come from creative thinking. In my mind, that is what is so great about this thread.

I love the flow of information and ideas in here. Let's keep it rolling.

DP-buggyboy

iTrader: (1)

Stroke will be the same as a "long stroke" .21 buggy engine.

So, when I got out of the shower last night after coming home from a race, I had a little flash of an idea of how to use the crankcase to supercharge a 4 stroke engine. You could simply valve it with reed-valves. The intake charge would get sucked into the crankcase when the piston goes up, then pushed back out into a the intake manifold as the piston goes back down. This would happen twice as often as the intake stroke, so I'm guessing it could give a significant boost without adding more rotating parts. Of course, other types of valves could be used, but it's just a generic and random idea at this point.

Has anyone ever seen this used in any type of 4 stroke engine?

Eccentric

iTrader: (3)

The closest I've seen would be the Husqvarna 4 stroke MX engines of the early eighties. They didn't have a regular oil pump (for weight and parasitic loss reduction), but had a reed valve in the bottom of the case to control oil flow. When the piston moved down and pressurized the crankcase, oil would be forced through a small reed valve and on its way through passages to where it was needed. This created the pumping action. Worked OK as long as the oil was changed OFTEN, and was high quality synthetic. They were air cooled, didn't carry much oil (by 4 stroke bike standards) and had a rep for cooking the oil (and failing).

Two stroke (GMC type) diesel engines use an external supercharger to pressurize the crankcase. The engine has exhaust valves in the heads, but no intake valves. The cylinders have ports like a two stroke gasoline engine.

I think you wouldn't have any gains by having the engine draw the intake charge into the crankcase and then forcing it through some other valve (reed or otherwise) into the cylinder (only using the botom of the piston as your 'supercharger'). Remember that the pumping action is the same on both sides of the piston. You'll have losses rather than gains. Now using an external supercharger to pressurize the crankcase on the other hand would be a different story, and would allow you to get plenty of lubrication to the lower end.

maxflo777

I haven't seen an engine using it, but again, the reason is likely based on energy loss. The problem with that system is given by the actual lower crankcase compression. Since the case's compresion is so low relatively speaking, there is not enough energy to supply the combustion chamber with enough fuel/air at the higher flow/rpms.

When the valve opens in the usual combustion chamber in a high compression 4 stroke, there is so little space in the chamber at TDC that the pulses that the piston produces as it moves up and down are reflected with very high efficiency so there's a lot of energy to move the gases to and from the chamber to fill it up. Actualy the higher the compression, the easier it is for the engineto breath at high rpms.

X

DP-buggyboy

iTrader: (1)

Hmmm. I thought it was a good thought experiment. I understand the crankcase is not efficient at pumping, but it's how many high-peformance, high-RPM 2 stroke intake systems work.... and they only get one "pump" per intake, where the 4 stroke version would get 2.

Again, it's something I would love to try and may not work at all... Maybe something to try sometime later on.

maxflo777

You are absolutely right on that, but the 2 stroke engine is not that good in volumetric efficiency, its the actual "one combustion per every other stroke" what makes "the good overtake the bad", BMEP on the racing 2 stroke usually is not high compared to the 4 stroke counterpart, which is the real measure of efficiency and thus, torque production at a given rpm. The 2 stroke combustion process is very dirty, the fresh mixture mixes a lot with the used one, so it's unlikely to get the eficiency of a 4 stroke if we consider only the power stroke, the 4 stroke's cycle stages are so well separated that they can do their respective jobs better, without the intrusion of the next stage. It's easy to see that in a 2 stroke, the overlap of the intake ports with the exhaust port is 100%!, in a 4 stroke is what, 5%? just around TDC.
So what I'm sayin is that the 4 stroke uses more air, rpm being the same.

X

DP-buggyboy

iTrader: (1)

I completely understand... but there's a part of my brain that won't let it go.

It's definitely on my "want to try" list. I'm going to have lots to do this winter during the off-season. It could be done fairly easily with an existing engine, and probably could be better than reed valves with a backplate-based rotary valve driven the same way a pull-start shaft is. I'll need to make a test stand with some sort of dyno so I can tell if it's a gain or loss.

maxflo777

The day we let it go is the day we stop learning.
There's something I really like from that system, in a single cylinder 4 stroke like ours, how do you properly seal and lubricate the crank case? and how do you keep the preasure pulses from blowing the front engine seal? with reeds andair/fuel passing through the crankcase lubrication is not a concern and the preasure delta goes down considerably. that could be preatty cool.

X

DP-buggyboy

iTrader: (1)

Here's another idea I came up with while shaving the other morning:

A sliding valve that works similar to an electric shaver.. 3 steel plates with many small slots in them -

The top one is stationary, and the slotted area covers the entire top of the combustion chamber (except for the glow plug). The intake and exhaust ports could each cover half of the combustion chamber except for the glow plug area.

The bottom plates slide the distance of the width of one of their slots (very little movement). It's reciprocating, but since it doesn't move very far, it could be actuated by a very non-linear captured cam, thus requiring no springs.

Of course, the limitation of this design is that each open "port" could only account for less than 1/4 of the total cylinder head area, but there would be very little time spent opening and closing valves. Each valve's cam could also have an independent profile.

The other cool thing about it is I think the valvetrain would be much more compact than my other rotary valve designs. It would also have a very tidy combustion chamber with a centered glow plug. It even has the potential to be designed with a hemispherical or slightly coned shape - of course flat is easier to make...

dieselpilot

YS does very well with crankcase supercharging in their four stroke engines. It is effective and efficient. It has been attempted one way or another many times over then last 30 years. I found maybe a dozen patents for such systems.

Greg

Eccentric

iTrader: (3)

Doesn't YS use a supercharger to pressurize the crankcase ? That's not using the engine's piston to 'supercharge' the the intake air/fuel like DP was thinking of. I suggested to DP that using an external supercharger to pressurize the crancase would work well. The YS engines have the supercharger built into the back of the engine, but it is still external (or rather seperate from the piston)...

Two stroke engines do move the intake charge through the crankcase and into the cylinder via ports, but don't 'supercharge' the intake charge. I didn't say the engine you proposed wouldn't run at all....just that it wouldn't have an advantage over a conventional four stroke that breathes straight from the carb to the intake valve (and certainly not one that has a supercharger).

I believe the 4-Mix engines that Stihl makes (for some of their string trimmers, brush cutters, and backpack blowers) breaths through the crankcase some how. It does have valves....is a four stroke....and doesn't have a seperate sump of lubricating oil. It runs on premix...

dieselpilot

Take a look at one.

http://www.google.com/patents?id=zcY...age&q=&f=false

http://tech.flygsw.org/ys91.htm

If you guys haven't studied the history of model airplanes engines you are missing out on a lot of interesting designs. Think the RCV concept is original? it was done by a German company in the 70's. Four stroke with reed valved crankcase supercharging and Aspin valve, Webra early 80's, though the engine wasn't strong at all.

I bumped into this today.

http://www.youtube.com/watch?v=eJlE-1dmEak

Greg

Eccentric

iTrader: (3)

Interesting. The YS I looked at years ago had a roots type supercharger on the back of it (as did a supercharged OS I saw around the same time)....not that air chamber thing on the engines you linked to. Realy cool stuff you linked there. Same guy at the field also had a Webra with belt driven cams and an HB with the rotary valves. Neat. I've been into old model engines for decades. They've tried some weird stuff over the years. Always wanted to play with an OS wankel...

dieselpilot

I'll have to do some searching. I've never heard of a Roots type YS. Webra engines were all rotary valve. There was an OPS OHC belt driven four stroke.

Greg