ESE's works engine tuner

[Frits Overmars]

One question to Frits: Has a FOS cylinder ever been run actually? 50 or 125cc? I an still curious after 10 years.
The somewhat similar 'Foekema system' was a complete disaster.....Even worse than the RYGER.

Curiosity keeps you young; you're welcome Jan .
A number of people have built engines with the FOS scavenging system, the best-known being Neil Hintz and Ken Seeber, both present on this forum.
Neil also incorporated another idea, variable port timing, and Ken has such an engine running on the dyno. He reports that it is extremely eager to rev .
https://www.youtube.com/watch?v=2p0d...ature=youtu.be

[jbiplane]

Curiosity keeps you young; you're welcome Jan .
A number of people have built engines with the FOS scavenging system

Hi Frits&Niels. What do you thinking of this kind of completelly symmetric tuning pipe for FOS use (shown by red)? An initial test on opposite engine gives some positive results. I make it by superposition of 2 classical pipes. Each cone play as expantion as reflexion role for each other.

[Frits Overmars]

Hi Frits&Niels. What do you thinking of this kind of completelly symmetric tuning pipe for FOS use (shown by red)? An initial test on opposite engine gives some positive results. I make it by superposition of 2 classical pipes. Each cone play as expantion as reflexion role for each other.

Well, that's funny Valery. A couple of years ago I posted a similar drawing; not as sophisticated as yours, but showing the same principle. I tried in vain to find it back, so here it is once more; maybe you'll have more luck than me tracing it back. The nice thing is that this type of exhaust system can work with 180°-firing as well as with 360°-firing cylinders.

[emess]

The Aprilia, developing its maximum power at a piston speed of 23,6 m/s, needed all the blowdown flow it could get. Huge auxiliary exhausts alone were not enough;
the main exhaust port had to be given a timing of no less than 202°, which is clearly too much for optimum resonance, but which was necessary in order to strike a compromise with sufficient blowdown time.area.
The MB40 engine has no piston ring, so the single exhaust port could be made as wide as we wanted, shown in the picture below. With 192° exhaust timing, which is fine for resonance, we could achieve sufficient blowdown time.area without having to wrestle for the last bit of flow coefficient.
It's more or less the same story with the FOS cylinder. It does have a piston ring, but it also has exhaust ports at both sides of the cylinder, again with 192° timing, and with more than enough blowdown time.area.
I must admit that I'd like to try radiused top edges, but that would raise the timing too much for my liking, or I would need new 'castings' (they're not really castings since the FOS cylinders were made via Selective Laser Melting).
Attachment 334849

Many thanks for all the replies Frits, Wobbly and Jan.

The question came from having an exhaust port with little metal to remove in the duct so the minimum area is about 10mm from the port.

Maybe Wobbly's 0.8 Mach in Engmod is the best guide to the area problem.

Would be interesting how Jan approached making a cylinder work with another design pipe.

Mick

[breezy]

Evening... well it is here... i think this reed block is off a mini moto.....does anyone know where i could get some thing smaller than this off the shelf?

maybe with only one petal... this reed block is approx 50 x 60 mm.. thanks.

[speedpro]

Honda MB100 reed blocks are single sided. With a carbon petal and the bridge removed they are still good for at least 19.9hp and that was with poor porting and a substandard pipe

[husaberg]

Evening... well it is here... i think this reed block is off a mini moto.....does anyone know where i could get some thing smaller than this off the shelf?

maybe with only one petal... this reed block is approx 50 x 60 mm.. thanks.

DLE 20

Arrow Motorized Cycles

Also some chainsaws have very small reed valves.

[lucf]

One question to Frits:

Has a FOS cylinder ever been run actually?
50 or 125cc?
I an still curious after 10 years.

The somewhat similar 'Foekema system' was a complete disaster.....
Even worse than the RYGER.

The whole story after exact 10 years:
FST-twostroke-design https://www.facebook.com/notes/luc-f.../4080202582494
https://www.kiwibiker.co.nz/forums/s...post1131082527

[wobbly]

Haha, the link doesnt work - sadly,like a Ryger.

[Yow Ling]

Link works fine

[husaberg]

Works better than Jacinda's birth control anyway

[jbiplane]

Well, that's funny Valery. A couple of years ago I posted a similar drawing; not as sophisticated as yours, but showing the same principle. I tried in vain to find it back, so here it is once more; maybe you'll have more luck than me tracing it back. The nice thing is that this type of exhaust system can work with 180°-firing as well as with 360°-firing cylinders.

Thanks Frits. My objective is to make 2 cylinder paramotor engines (to reduce vibration on human being back) and exhaust system very important for.
Before implement is nice to know if idea is in general good, but I dont know simple and robust method to design system like this. My friend make some
calculations in Fluent, but it complicate, time consuming and non evident.

[jamathi]

Curiosity keeps you young; you're welcome Jan .
A number of people have built engines with the FOS scavenging system, the best-known being Neil Hintz and Ken Seeber, both present on this forum.
Neil also incorporated another idea, variable port timing, and Ken has such an engine running on the dyno. He reports that it is extremely eager to rev .
https://www.youtube.com/watch?v=2p0d...ature=youtu.be

I am happy to hear that Frits!!

[breezy]

thanks for messages/ replies on the reed valves,

[breezy]

[QUOTE=TZ350;1131081218]Thanks for taking an interest in my EFI project. I am not sure I know much about 2T injection either but I am finding it a fun and challenging learning curve.



Tonight I ran the bike up and put my finger over the pressure sensor hole in the cylinder. At idle there was plenty of hot gas coming out but as I revved the engine up the volume and temperature of expelled gas significantly reduced.

The temperature drop... can this be explained? would it be different if it misfired?