Supercharged XR80

[Husky500evo]

I scanned an article from an old Dirtbike magazine which features an XR80 top end on a KX80 bottom end & uses the idea of a crankcase supercharger setup. The crankcase supercharger is basically the same idea that was used on a Maico 4 stroke prototype a few years earlier . I have posted an article on the Maico prototype in the Maico section . I don't really know why this idea never took off , but I read that the Maico had problems because the inlet tract was too long & that it got hot very quickly & lost power . 

[GMC]

I think the problem with this idea is that the crankcase volume is the same as the volume above the piston so it's not really supercharging it with any extra.
It may have some scavenging benefits by having some pressure buildup for when the valve opens, but they would be minimal.

I recall this article & seem to remember this project gathering dust in a corner of his workshop when I visited Dave's workshop in 85

[Lozza]

It never took off because it won't fly. Where exactly is the 'supercharging' coming from???  A decending piston creates very little in the way of positive pressure in the cranckcase. A falicy which seems to be what that all seems to be based on. Can't enlarge the text either anyway of doing that

[Tim754]

Thanks Lozza and GMC that is exactly what I was pondering on the above. It just does not actually do anything.

[mx250]

It might work as a multi cylinder.

[mx250]

The Norton Wolf two stroke tried something similar didn't it. It had a piston with two bores, the lower larger bore was to act as additional pumping.

[YSS]

Same as the PUCH 125  ?

[pokey]

I wonder if the Date on that article is April 1 ?

[Husky500evo]

I am still learning to drive my new scanner . I have tried a different way of posting the article , but it appears a bit blurred when magnified . I also have to scan the last page . Any tips on making it more clear .

[pokey]

to get the words one would need a scanner with OCR
 Optical Character Recognition.
 many have that these days .
 It transforms what we see as a picture of words or even hand writing into actual text.

[grouty]

From memory, CCM tried something similar back in the 70's. They called it the "Five Stroke" project. I think it used the decending piston to create more pressure fed back up through transfer ports similar to a 2 smoke. It retained the inlet and exhaust valves.
Must dig out the book.
It is all a bit acedemic now as modern fuel injection and electronics have made it obsolete.

[oldfart]

Crank speed may be doing all the work rather than piston .

[Mick22]

Crankcase supercharging works, there is a group from Melbourne that have the patent on a type of this design and have engines up and running and are currently marketing it to manufactures. It is mainly to be used where traditional 2 strokes would be used as it has a lot less emissions but similar power/weight of a 2 stroke www.hhed.com.au

[T250K]

  You may have something there, oldfart.   In the late sixties Smokey Yunick sealed the bellhousing on his NASCAR and ran plumbing up to the airbox over the carby.   At top speed the flywheel gave about 2 psi of Supercharge.

[Marc.com]

keeping constant pressure i imagine is the biggest drama, you have the crankcase displacement being realtively linear to acceleration but the engines air requirement is not a constant....it all works much better if you hold things at a constant speed .

I work for turbocharger manufacturer, we are currently up to almost 5 atmospheres, so 70 odd psi of charge air pressure on large engines at relatively constant pressure.