HP of a 47.mm BBK / 1 ring or 2

[skuttadawg]

I was blown away when I read this " The successor of the popular Stage6 70cc Racing cylinder is called Stage6 Racing MKII 70cc. It has been completely revised and has 1hp more out of the box. Re-designed aluminium cylinder with high-strength Mahle/Nicasil coating. The former flat piston has been abandoned in favour of an R/T replica with 0.8mm ring and domed crown. The thermal stability has been improved in all areas. Generous flushing of the bridged exhaust port; pentagonal design and inner cooling fins; one-piece head with scavenging passages - to name but a few of the improvements. With the right components, this cylinder yields 17-19 hp right out of the box. And there is still enough material left for everyone to do some own work and get more than 20hp out of this cylinder.

Wow !!!!! That is twice the HP of a GY6 !!!! . I know there is a lot of factors that determine how well it will run

A 49cc 2T most say 1.9HP when restricted and up to 4.9 HP with restrictions removed . I saw a Polini that said it was 7 to 8 hp and only 49cc so even this would be a step up and better quality of metal .

Why would I want a single ring when ther eis a dual ring which to me seems like 2 would hold in the compression better .

[reveeen]

Why would I want a single ring when ther eis a dual ring which to me seems like 2 would hold in the compression better .

Typically, on a daily driver, you wouldn't. The engine life, with a single ring piston, is less than 1/2 that of a dual ring.

Personally, I *think* you have to take anything the Stage6 advertising department says "with a grain of salt". If, in fact, you ever get to see in excess of 12hp out of a 70cc engine I am convinced you will be measuring your engine life in hours, not weeks.

Honda, who has been at this a LOT longer than Stage6, (and actually makes their own parts, not sub-contracts batch manufacturing) never claimed 20hp out of their water cooled 85cc engine that is notorious for a short life.

[90GTVert]

I've read OverRev (a very experienced tuner) saying that he could get 15HP out of that cylinder with porting and the right pipe. He's 1st class, so don't expect 17-19HP. I think reveen is closer around 12HP. What pipe you choose can make a big difference there.

I also don't like single ring stuff for street motors, unless you don't really mind sacrificing longevity for a little extra performance. A single ring kit creates less friction, which especially helps at higher RPM. I believe the single ring pistons are also slightly lighter than their dual ring counterparts. Two rings do a better job of sealing in compression, which helps both with longevity and some even claim to lose some bottom end power with a single ring for that reason. Of course most single ring kits are intended to rev high, so you would likely be adjusting the CVT to bypass low RPM anyway. Another thing is that pistons transfer heat into the cylinder walls for cooling via the rings so I'd think a single ring piston would run hotter.

[lshigham]

Single rings give more power above 9k due to the friction reduction and less below due to more blow by, hance why they're only used on high revving kits.

For a street motor, I'd be expecting 12-13 hp from one.

[jmkjr72]

you wont see that kind of power with out a lot of work a sky high reving pipe and a 28mm carb

you try to run that kit with your 19mm carb and you will burn it up

and your 700 dollar budget well plan about 400 to 500 out of that for the pipe to get into the power range they are talking