"New" 2-stroke tech

Discussion in 'Advanced Technology & Engineering' started by WorldWideRacer, Jun 18, 2001.

  1. WorldWideRacer

    WorldWideRacer Rookie DRN Member

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    Most of you have probably seen the prototype of the 2002 Honda CR250 by now and are probably asking all kinds of questions about the electronically controlled powervalves, and whatever else might be new to this bike. Well, here is some news: this technology has been around for quite a while. I just purchased a 1994 Honda NSR 250. For those of you who dont know about this machine, here are the details: It is a v-twin 2-stroke 250cc street bike that uses some pretty advanced tech that allows it to achieve nearly 65hp at the rear wheel, with no engine mods. The heart of the technology (as much as I understand it) is a computer that monitors engine RPM, speed, temperature, and throttle position which it uses to control the ignition timing, exhaust powervalves, and powerjet carb. This system was also designed to use a card (kind of like a credit card) as the key. In the racing scene, you can use different cards to "tune" your bike for different tracks (high RPM or low RPM powerband as you choose). So here is the question for the experts: If this technology has been proven since before 1994, why have we not seen this technology move to the dirtbike scene sooner?


  2. marcusgunby

    marcusgunby Lifetime Sponsor

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    Because of the dirt;)
  3. CRGuy

    CRGuy Posts Too Much DRN Member

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    To much wieght? too expensive?
    CRG
  4. Norm

    Norm Rookie DRN Member

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    Servo controlled power valve

    I posted a similar question a while back (tried a search, but it's gone now). I found out that the Yamaha WR200 from the early 90s actually had an electronically controlled powervalve, although it probably wasn't as high tech as the one in the NSR or the new CR. I also heard that electronic powervalves weren't legal according to AMA rules. Don't know if the rules have been changed since. Otherwise, it doesn't make a whole lot of sense for Honda to use the technology on their MXers.

    Norm
  5. FERNANDO

    FERNANDO Rookie DRN Member

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    My friend ( a.k.a. MTRHEAD ) told me a while back that Bob Hannah rode works Honda's back in '85 that had electronic / servo drive power valves in supercross and nationals. He also said that several PWC and snowmobile companies have had them in production for some time. He also mentioned the WR200.

    He's very excited about this new motor and seems to think it's a milestone for modern two stroke MX engines. Claiming that from what he's seen in the photos he can tell that it should make some big top end. And that the new case reed / power valve set up should allow them to also have a very wide powerband with a lot of tuneability.
  6. WorldWideRacer

    WorldWideRacer Rookie DRN Member

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    I dont think weight can be that much of an issue, this stuff is pretty light in construction.

    I should also add that this particular engine (NSR250) used this same design from around 1989-1998. Then Honda quit selling them.
  7. Taliesin

    Taliesin Rookie DRN Member

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    The last (Swedish) Husqvarna CR250 of 1987 had a servo/motor controlled powervalve.
  8. JasonJ

    JasonJ Rookie DRN Member

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    Yamaha has been using exhasut tuneing in street bikes (YZFs) for a while and I read an artilce on Honda 01s I think 929 RR and the RC51 that use electroicly tuned air boxes and exhaust to frequency resonate or "ring" the the whole flow. They even changed the color of the airbox plastic to white cause they claim it matteres! I too wonder why MX seems to be so low tech. I think the overall cost of what people are willing to pay, how hammered the bikes get, seems to behoove the manufactures to keep the cost lower for the average non pro MX folks where as road bike raceing is no holds bared what ever it takes to go .2 MPH faster than the competetion. Where is direct fuel injection on 2 and 4 strokes? Where are these hydro electronic valves for 4 strokes? This stuff is out there but Cannondale seems like the only one trying to push the envalope. Maybe cause they have the most to gain and the most to loose if their bikes dont prevail at a competitive cost.

    P.S. I saw a moutain bike at the bike shop that had an electronic suspension valve button on the handel bar that let you lock out the shocks for going up hills or on pavement.
  9. LB400

    LB400 Rookie DRN Member

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    Dirt bike tech does seem to be lagging. Some snowmobiles have electronic suspensions that adjust 1000 times/second, exhaust gas sensors that adjust the ignition timing to suit the conditions, throttle position sensors, and electronic exhaust valves.

    We're talking some extreme conditions for sleds, albeit, no dirt. The prices aren't that outrageous either. The future for bikes is EXCITING!
  10. motopuffs

    motopuffs Rookie DRN Member

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    true about sleds, but in other areas, steds have been lagging behind for years. Wasn't too many years ago that damping adjustment (clickers) became available on sleds, and it still isn't available on some models. Spring preload adjustments are more popular.

    I think dirt bikes have had damping adjustments since at least the early eighties.

    Some sleds still have round slide carbs...I don't think any "performance" bikes still have round slide carbs.

    Kawasaki already has tried throttle position sensors a few years ago, didn't seem to have much benefit, at least the way they applied it.

    The Bombardier "RAVE" valve system, now in production for maybe 10-15 years, is simpler than most dirt bike power valves, and seems to work well. Very few moving parts.
  11. Daniniowa

    Daniniowa Subscriber

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    The technology hasn't been mass manufactured because of costs. It is expensive, and does add some weight also I'd guess up to 10 lbs or more for all the sensors and devices to run a fuel injection system, with up to 5 more pounds for a direct injection system. All the pumps, hoses, sensors, and wires are heavy, especially when it is only on a single cylinder engine, not spread out along multiple cylinders. Hence, Canondale's extra weight.

    My 1985 Yamaha RZ350 uses a Banshee engine, but has servo controlled exhaust valves in different cylinders. It also came with catalytic convertors to pass emissions for street bikes at the time.

    Direct injection technology is coming from a company called Orbital . It seems all the companies are contacting them for development help.
  12. Road/Dirt Rash

    Road/Dirt Rash Rookie DRN Member

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    I think that one of the reasons you won't see much of the streetbike tech stuff on true race caliber dirt pounding bikes is that it requires a steady, spike free power system, thus a battery as a ballast which means charging coils and circuits. Technoligy will probably catch up to the weight, heat, and vibration problems soon, so who knows.
  13. Phildirt

    Phildirt Lifetime Sponsor

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    direct injection

    There are other alternatives to the Orbital direct injection system, previously mentioned. Rev! is proceeding with the Ram Injection system developed at OMC / Bombardier. It has some advantages over the Orbital system. There are other systems that merely use a high pressure pump and injector (similar to a diesel system) that have merit.

    A decent electrical system will use good regulation components and properly sized capacitors to control ripple.
  14. WorldWideRacer

    WorldWideRacer Rookie DRN Member

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    He, he, here's another one for you:

    I just picked up a 1985 Suzuki RGV 250 Gamma Walter Wolf edition that also has selenoid operated powervalves. Geez, I didnt realize they had this stuff around for this long...:eek:

    On a side note, I picked the bike up for free, and it even runs!:)
  15. someday

    someday Rookie DRN Member

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    Do all these high tech road bikes and snow mobiles require the amount of engine maintnance (top ends) that dirt bikes do? Are their riders, as a group, as inclined to work on their equipment as dirt bikers are? Perhaps one of the reasons dirt bikes aren't more electronic is the makers fear of providing a product that people feel they could no longer work on. Possible?
  16. Phildirt

    Phildirt Lifetime Sponsor

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    There should be no fear on working on products that contain sensors and electronics. It just requires that the OEM supply, or have available, the proper diagnostic equipment for a reasonable price. It's a new set of tools.
  17. KaTMandoo

    KaTMandoo Rookie DRN Member

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    Someday, you make a really good point. I know that my buddies new Prairie650 fourwheeler is all electronical and stuff, and although he has so much more experience with engines and the like than I do, even he wont work on his fourwheeler. I can definitely say that if they move more towards electronics that I would probably be sticking with my '99 KTM 300 for quite a while, just becuase I wouldn't wanna take my bike to a mechanic to have it worked on.

    KaTMandoo
  18. someday

    someday Rookie DRN Member

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  19. nephron

    nephron Dr. Feel Good

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    FI--what's the point?

    I mean, what's the point in a 2 stroke? That's not an actual question, but rhetorical, unless somebody can come up with a convincing answer. Where does fuel go in a 2 stroke? CRANKCASE What mechanism "pushes" fuel during intake cycle on a 2 stroke? PISTON What determines volumetric efficiency of a motor? HOW MUCH AIR AND FUEL CAN BE SHOVED INTO THE COMBUSTION CHAMBER BEFORE FIRING What typically provides impedance of this process in a 2 stroke? EXHAUST

    Obviously, an electronic powervalve would be much more likely to result in improved efficiency than fuel injection in a 2 stroke, unless we're talking about a "supplemental" injection during the late intake cycle directly into the chamber?

    I'm not tryiing to be a smartass or knowitall, it just seems that fuel injection is being thrown around here like it is really an advance in 2 stroke technology. Also, I am solely here to learn, not teach. And if anyone can provide an answer that would provide me entirely wrong, I'd be happy as a clown!!:)

    While we're on the topic, 2:1 cc 4 stroke: 2 stroke allowances are unfair in the AMA. Volumetric efficiency of 2 strokes suck because of the amount of exhaust still present in the combustion chamber during firing. I think the VE of a typical 2 stroke dirtbike motor is around 60%. The 4 strokes are achieving about 90-95% VE.

    The rule should allow for this. ie, a typical 250 4 stroke should have to compete against a 160-170cc 2 stroke. Sorry 4 stroke folks, that's just the way it is.

    I'm sure none of the above is new...:think
  20. Rich Rohrich

    Rich Rohrich BioHazard

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    You are glossing over the rather complex relationship between fuel curves and how they are related to pressure. A conventional carburator is nothing but a series of passages that react to pressure differentials between the engine and the atmosphere. Your average carb's inability to adequately adapt to the changes in atmosphereic conditions and the resulting changes in carb metering as well as volumetric density leaves huge room for improvement.
    Without going into a disseration level explanation suffice it to say that while standard slide needle carbs have served our purposes quite well up till this point they are remakably crude and pale in comparison to what is possible with closed or open loop feedback EFI systems. There is no question that there is a cost and complexity associated with moving forward, but as Charles Kettering so eloquently put it "the price of progress is trouble"

    As far as displacement factors go, if you do a stroke averaged analysis of BMEP you'll find your math is off.



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