Earth Surfer
Posts: 524
Joined: 7/27/2006
From: Grand Rapids, MI, USA
Status: offline
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Ryan is right, but a stock G260 (the new or the old) will make about 4hp with a good pipe. I think that is what your talking about.
IMO the Zen cylinders and the GP29 cylinder are the best quality on the market (and both could be better). The GP29 cylinder has a lot of compression though, that will hurt top RPM (but great for grunt). The stock porting of the newer Zen cylinders is ported for more top RPM than the port timeing of all the other CY cylinders. The CY cylinders knocked off the old Zen port timeing--and never changed it. The exhaust choice might not let you see that difference in actual performance, and you might actually get the opposite results with different set ups--because a pipe,that is actually matched to porting for a particular application is really pretty rare so far.
A cy29cc (35,, bore and 30mm stroke) will not out rev the ESP30.5 top end---everything else being equal. The 30.5 piston is bigger in bore dia, for more power, the compression is corrected and uses a better gemoetry for more top end. The cy29 engines I tested three years ago (when they came out) reved lower than any other RC engine out there (stock), but they have good low end (the 36mm bore GP29 cylinder did not exist at that time--Go-Ped came out with it less than 2 years ago). The CY29 head kit (the pretty heads) revs lower than the non head kit (and is the lowest reving of all RC engines stock) version and does not perform across the RPM range as well as the CY29 non head kit top end.--The 30.5cc engine beats both of them in power everywhere, more top end (everything else being equal) and is much more reliable. (no funy piston wear the 35mm bores have--or warped cylinder tops that tend to leak)
I am not a fan of the Zen 32mm bore, because it is just a smaller engine, But it's a good engine. So, IMO, I only choose between the Zen G260 cylinder (or moded G260 cylinders) or the GP29 cylinder (espically when head modded) to build the best engines that I think can be made. IMO, other than the high compression of the GP29 cylinder, the quality is just as good as the Zen top ends.
For top speed, I would start off with a G260 because of it's shorter stroke and more high RPM porting--and try to find a high reving pipe. When you start hitting about 19,000 RPM, your doing a respectable job for a higher RPM engine.
For track racing and bashing, the bigger 30.5cc is more fun out of the tight stuff and into the next jump. A good pipe may make the ESP30.5cc actually rev pretty good (if it is a controlable power delivery), and I would not be suprised to see up to 17,500 RPM out of it with the right pipe.
I have not done any RPM testing on my RC car yet---my numbers are based with my 200 plus lb body on a Go-Ped with one gearing choice, and one chosen pipe. I am not sure if a RC car would rev higher, lower, or the same.
Exhaust choices are the big question mark right now. If you want top end, you can easily buy the wrong pipe for your hyper G260, and end up with a moderatly reving engine (pipe does not work well with the high reving porting). We don't know if a pipe can be raced on a track and stay in control for fast lap times on the 2 wheel drives (until we start racing them), and we don't know which pipes want to rev and which ones have more low end power--how hard they hit--how smooth they are--etc etc. Pipes have just as many, if not more, combinations in geometry to enhance the power where you want it.
The CY 27 is actually a good size for good torque and really good RPM and a lot of people like their performance. It could be a step up from the G260 if it had updated porting, corrected compression and better quality---but both the CY27 and CY29 (both 35mm bore cylinders) have quality issues I don't like, and I think should have and could have been fixed years ago. Both cylinders will wear the piston badly on the intake skirt because I think the piston to cylinder wall clearance may be too tight. The cylinder squishes the stock gasket a bit when you tighten them down, and it actually pushes the cylinder wall (near the intake side bolt) inward enough to cause piston scuffing near the bottom of it's stroke. (I have over 60 brand new 35mm bore top ends here, that were test run at the factory as complete engines, to prove it.) Most of the time, the problem could be solved by using a .020" copper gasket instead of the stock .020" paper gasket. The copper gasket does not compress like the paper, and usually you won't feel any binding by turning the crank shaft (not flywheel) by hand with no plug in it and the ignition removed. With the stock gasket--it is like--tighten the cylinder to spec--feel the bind--loosen the cylinder a bit--the bind goes away. I never measure it, but I am almost positive that the cylinder to piston clearance could use another .001" clearance. The 29cc CYhead kit engine (I never used the 27cc head kit version) is a good low end performer, and has a pretty respectable mid range performance for bashing---But the quality for function is poor on that head kit. IMO, that kit should have been redesigned about 2 years ago. The head kit was designed for sales (probably by sales people)--not performance. The stock CY cylinders I tested worked quite a bit better and more reliable, and were the best top end out there when they came out (accept the plating stunk).
I like the GP290 cylinder the best because it is bigger, and Go-Ped (who came out with the bigger cylinder) worked with CY well to make their product better. Their plating also stunk at first--it was even worse then the other CY cylinders--I think they still use different plating than the other CY cylinders. I personally called the owner of Go-Ped and thanked him for working with CY to make the plating better on that large bore 36mm cylinder that was a shame to be a waste. Go-Ped did a great job, and CY is more willing to work with their customers than Zenoah is (typical japanese company--they allways know what is best for their customers). The other companies using the CY factory don't seem to have that same drive in working with CY (and other people who know two stroke design) to improve their products. The other companies did offer us larger bores, and stroked cranks first though---so my hat is off to them for that. I just wish they would not be so worreid about retail price and do some improvements so I did not have to say--"I don't like the 35mm bore cylinders".
< Message edited by Earth Surfer -- 2/15/2007 5:34:29 PM >
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Zenowa or CY? - 
