1938 DKW GP racer

[Puffs]

Yes, very interesting technology. And beautifully made. Particularly that water-cooled record one...

Any idea how their performance compared to modern racing 2T's, with a resonating expansion exhaust, a power valve on the exhaust & reeds (or a rotary) on the intake?

Of course with a compressor the concept of stroke volume blurs a bit; the compressor contributes to compressing the mixture, hence should partly be included in the stroke volume. Maybe because of that ambiguity they banned them in racing.

[GPbikes201]

I know that pistons fire in parallel to a single combustion chamber etc. I'm 20 and am always willing to learn and keen. I like motorcycles and come from that background. I'm not really satisfied with all I know, but you learn something new every day.

[Puffs]

Well, if you're interested, search for 'ladepumpe' or 'DKW ULD 250'. DKW won everything in their time, and their latest pre-war prototype 250 (the DKW US 250) did 40hp. For the sidecars they had a 600cc version that did 48hp.
But development continued and modern 250cc 2T singles, as were used in MX before 4T became the norm, have a broad powerband and are around 55+hp, in a 96kg (dry) package. Road racing 2T 500's peaked around the 200hp mark, in a 130kg (dry) bike (see for instance https://www.motorcycle.com/manufacturer ... plica.html). And then they were banned & replaced by 4T's.

[GPbikes201]

Yeah, I know. They're awesome. They just sound out of this world. The RPM shows it all. These things did over 7000 back in the 30s! When some race bikes back then only did 5000. They could go above. There's one here, although I can never figure out the location.
https://www.vintagebike.co.uk/pictures/1936-dkw/

[GPbikes201]

@zippy There is a DKW here, in the Stanley Woods documentary. Always love the new stuff on YouTube which leaves the old stuff so updated. I had an image in my head though one time, when i was looking, vice versa, weeks ago, about his, the one he had an overhaul with, thus I tried to find it and had a brief visage, image in my head, when I watched Ralf Waldmann on his. Like I said, though, brief, but the bike is almost identical in the documentary and has the #27 plate which the bike Ralf was riding had and tank the same shape. People, take a look.

https://youtu.be/MpdPVhFZApU