RPM Range? Claimed HP and torque? Dyno runs?

Discussion in '2-Stroke Engines' started by Nerobro, Mar 23, 2008.

  1. Nerobro

    Nerobro Member

    So what RPM range are these motors designed for? Has anyone done a port map of one? Has anyone thrown those numbers into a calculator? Or used something like the 2 stroke handbook to design a pipe?

    So, what's the claimed numbers on the 48cc? 60cc? 80cc motors?

  2. feelinright

    feelinright New Member

    I believe the 48cc is 1.6 horse and the 80cc is around 3 hp. They say they peak a little higher. I have used both engines and they are not terribly impressive as far as engines go but they are actually designed for bicycles and are resonably priced.I started with a 48cc kit and peaked at 28mph and now have a fairly modified 80cc and have peaked at 38mph.
  3. caddymankc

    caddymankc Guest

    So there is a diffrence between the 50cc and 80cc engine, i thought i read somewhere they are the same engine.
  4. Nerobro

    Nerobro Member

    they most likely are, just with different pistons and barrels.

    so who can talk to the RPM ranges they're designed for?
  5. BoltsMissing

    BoltsMissing Active Member

    I use a section of a mile long main road to get a rough idea on the engine's strength ( those aware of the section in Adelaide, it's the section between Main North and Bridge Roads, going up the hill starting at Gepps Cross).
    The 50cc will strugle a bit, the 70cc won't strugle as much.
    During the heat wave we just had, the 50cc got hot, but it was new then and not fully runnin, helps if you pedal and not strain a new engine, any engine for that matter.

    I have switched fuels from 92 Octane to 95, may cost a bit more, but found I get better MPG with the 95.
    When the engine is fully runnnin I'll try 98 Octane fuel and see how it goes.
  6. feelinright

    feelinright New Member

    Yeah I've had both engines. The (80) cc engine seems a little more torquey and seems a little better overall. Can't say it's twice they power as advertised. These engine run a 6 to 1 compression ratio which is totally lame. I don't have a tach hooked up but I'd say it starts to struggle about 5-6000 rpm. Which again is lame for an engine this size. A good two stroke this size should easily hit 10,000 rpm but you get what you pay for and thank uncle sam for the chinese import ban on 2 cycles. There are other engines out there and I'd be intersted in what works. Most engines I look at in the 80cc range put out 8-9hp which is like 3 times the power of these engines.Maybe someday I'll do some more experimenting but for now I'm happy just to be up and running fairly well. So far I've meessed with intakes,carbs,exhaust, gas/oil mixes,intake resonators and even nitrous oxide but the improvements hav'nt really been worth the time or money.
  7. Nerobro

    Nerobro Member

    feelin, the trick, is to read up, and follow the math. That's why I asked what I did to start this off. :) go read the 2 stroke tuners handbook, or any of the many 2 stroke books out there. These motors could easily make 5-15hp depending on displacement, it just depends on how far you're willing to go with the dremmel. :)
  8. BoltsMissing

    BoltsMissing Active Member

    Anyone got some pics on what CAN be done with a dremmel on the HT ?
  9. feelinright

    feelinright New Member

    Going to take alot more than a dremel. I'm sure nero could enlighten me with all his knowledge. You tune one of these to 15hp and I'll send you a thousand bucks for it, sound fair??
  10. 15hp...for how many seconds?!!?
    This engines couldn't handle...the clutch couldn't, the gears couldn't, the head bolts couldn't, the crank couldn't...
    So I don't know what part could.
    maybe 6hp or so tops.
  11. Nerobro

    Nerobro Member

    It might cost that much to do it. :) But 15hp from 80cc isn't a ridiculous number. You're actually going to make me do this aren't you? I'm not willing to go that deep money wise. (I'm not about to start ordering forged pistons, and having combustion chambers custom machined) But 5hp? Sure, I'd be willing to go for that goal.

    The Honda MB5 made 7hp with a 49cc 2 stroke. Air cooled, no oil injection, nothing silly. The disk valve, air cooled, TS-90 in my garage supposedly has 19hp.

    If you want to be really silly, so long as we weren't trying to do it for a long period of time. There's no reason we couldn't try for RS50 horsepower levels. That little "moped" makes 15hp. In factory tune.

    I don't have one of these motors yet.... Do any of you have the inclination to port map one for me? And give me some idea of the RPM ranges these motors are designed for?
  12. You WILL need another clutch design that won't fit in that width. This is, a multiple disc one, like on motorcycles. It is simple math. More contact area= more power transfered without slipping and burning.
    And it has been done. There was a post somewhere here about six months ago, from a guy from Estonia I believe. He used the russian bicycle engine similar to the chinese HT as a starting point. That engine had a big reed valve and intake welded and through the case like a CAG pocket bike. He made it watercooled and with a multiple disc clutch. The bike had a red frame and he had a series of pictures posted here.
    Yes it can be done.
    But it won't be in the HT format no more.
    I have seen the gears from the crank to the clutch break in stock form. So...EVERYTHING from bearings to crank, rod, etc. might have to be revised. And swaped for something else. At the end of the day you might have more foreign parts than original ones.
    Is it then a HT engine still?
  13. Nerobro

    Nerobro Member

    That's only if you exceed the torque rating of the clutch. Really there's a finite amount of torque a given displacement motor can make. (as long as we aren't talking forced induction) To make power beyond that, you need to move that torque curve up to a higher rpm. Same torque, means same clutch specs. Higher rpm means more horsepower.
    That's a good question. :) Not one Im' willing to try to answer. Though we're far off the topic I started.

    Who's put one of these things on a dyno? :) Who knows how much power they REALLY make? What RPM do you run?
  14. HI,

    I looked into factory made dynos for small engines and go karts and they are pretty expensive ($7500+......I admit it would be nice to KNOW what these engines actually make power wise and to see what kinds of power gains we are actually making when we are tinkering with them....There is another thread here that talks about making a low cost home made dyno....Might be good if one of us can make one!

    In answer to one question here, I've had my dax 70 up to 6400 RPM's briefly (Measured on a Sen Dec tach with peak speed hold feature)....Personally, I would not want to run it at length at that speed though)....

    Just a random thought but if one could find a level stretch of road on a calm (no wind) day and had the bike outfitted with a digital speedo and stopwatch and had a video camera filming the instruments (for later playback to plot speed VS time)...One could approximate the HP output of the engine by knowing the total weight being accelerated
    (bike and rider) VS time....Of course the figure HP figure calculated using this method would be a little on the low side since aerodynamic drag would not be figured in (If there is a tail wind the calculated HP figure would be high (less time per given speed with the aid of the wind), if a head wind the HP figure would be lower than actual since the wind would be holding back the rider and make it seem like the engine is weaker in accelerating the bike....Of course dead calm also, would make the HP calculated read a little low since the bike still has to fight wind resistance....

    Hmmmm but then again, some home weather stations have a device for measuring wind speed and that info can be video taped as well (wind speed VS bike speed off the wheel).

    Anybody else have any other ideas?

  15. Nerobro

    Nerobro Member

    the real problem we have with using the "accelerate vs time" while on a bike is we have 2 stroke motors. And they have very funky powerbands. To make that work well you need to have a high sample rate. Say.. several times a second. And then aerodynamic drag sets in. so you'd need to factor out the drag to find the real number you're working with.

    That method however, is exactly the method used on inertial dynos. You take a known weight, hook up a motor, and open the throttle. The computer checks weight speed constantly, and measures how much the weight has accelerated. Since you know the rate of acceleration, and the mass it's accelerating, you can calculate the power input. And because the drag on the spinning weight is minimal at best, you don't need to calculate the value out.

    The bikes already have a chain output. so hooking them up to a weight wouldn't be hard ;-)

    Dynos don't need to be expensive. The most expensive bit would be the software to run it. And even that can be "fudged" If you setup the microcontroller to output a TDF file, any spreadsheet program could take it and make a graph of it.
    Last edited: Mar 29, 2008
  16. funker

    funker Guest

    The engine in the Dyno

    A friend of mine, who´s brother is go-kart racing mechanic have a test bench (inertial dyno) that uses for tuning his two strokes engines, and put one of this HT 65cc engine, standard condition, on test.
    The results are in the pictures below, with the entire setup.
    The engine stock standard give a disappointing 1.5HP over a relative big range of RPM, it´s was a fast test, and some things may be tuned but gives you and idea of the relative performance of these engines.
    The brother of my friend said that this engine ( HT 65cc), can be tuned to give almost 5 o 6 HP easily (im not an expert just repeating other´s words).

    PS: Extracted from the thread of my spanish motored bike forum MotorKit

    Attached Files:

    Last edited by a moderator: Mar 29, 2008
  17. Nerobro

    Nerobro Member

    That's a beautiful rig. Perfect. Thank you.
  18. HI Funker,

    That's a nice setup your friend has....Man I wish you guys were near me!

  19. echotraveler

    echotraveler Member

    i enjoyed reading this thread! thanx!

    do yo guys think the new chinese engines have evolved to give more HP now?

    ive seen a couple that claim 5hp out of 80cc
    plus the general consensus ive read is that the newer chinese motors have better quality...

    and that dyno is great!