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"New" 2-stroke tech

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Posted by: WorldWideRacer---------------------

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?


Posted by: marcusgunby---------------------

Because of the dirt


Posted by: CRGuy---------------------

To much wieght? too expensive?
CRG


Posted by: Norm---------------------

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


Posted by: FERNANDO---------------------

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.


Posted by: WorldWideRacer---------------------

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.


Posted by: Taliesin---------------------

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


Posted by: JasonJ---------------------

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.


Posted by: LB400---------------------

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!


Posted by: motopuffs---------------------

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.


Posted by: Daniniowa---------------------

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.


Posted by: Road/Dirt Rash---------------------

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.


Posted by: Phildirt---------------------

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.


Posted by: WorldWideRacer---------------------

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...

On a side note, I picked the bike up for free, and it even runs!


Posted by: someday---------------------

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?


Posted by: Phildirt---------------------

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.


Posted by: KaTMandoo---------------------

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


Posted by: someday---------------------

Zackly!


Posted by: nephron---------------------

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


Posted by: Rich Rohrich---------------------

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.


Posted by: nephron---------------------

Rich, I agree with "the price of progress is trouble", but that's about it. Use BMEP, FMEP, IMEP, Int Manifold pressure analysis and calc. VE to build v8's, via various programs and confirmation on a dyno when available. Been doing this a long time. Nothing complicated about it.

I can tell you everyone jumped on the fuel injection bandwagon in high performance about 5 years ago, including myself. I tried various types/ thr. body, port inj, etc. It's nice, but it's also real, real hard to replace a good Holley carburetor if it's set up right, which is quite easy. Down low, you're talking small percentages "off" as regard air:fuel ratio carb vs. fuel injection, with equivalent efficiency above 5000 rpm. Throttle body injection, which is probably what would go on a 2 stroke (although I'm not sure), litterally pales in comparison to carb up top. I could never get one set up on an LS6 454, even with closed loop/O2 sens. This is probably why Pro Stock Big Chevy V8's running 6 second quarters run 2 Holly Doms, and not injection (well, besides the rules, hehehehe).

So, in "out and out" performance, I have to say that in 4 strokes, there's little difference, and absolutely no horsepower gain if the carb is set up by an expert. The ONLY benefit in my mind, is running constant 14.7:1 air:fuel continuously, resulting in improved emissions and gas mileage . But, like I was saying above, there's too much "dirty" activity going on between crankcase injection and the combustion process to improve efficiency, and there's no way in hell you could run closed loop given the inefficient combustion process and excess of unburnt fuel in a 2 stroke. That leaves the good ol worse than carb "throttle position sensor" open loop technique. :silly: Kawasaki already tried this and failed, as I recall.

When it all comes down to it, people end up going back to what they know, and fall back on simplicity. The current trend in high performance automotive is to go back to the carb. The carb will always have a devout following, for good reasons. :D

Now, don't flame me. I don't pretend to know what you know, and I hope to god you're not a 2 stroke mechanical engineer or something, cause I'll just stick my f>>>ing foot in my mouth right now. :scream: I just see this whole concept as being pushed by regulators and people trying to make the "tree huggers" happy as a final effort prior to eliminating 2 strokes altogether. In the meantime, I'm gonna kill as much plantlife as possible with my rancid smoke and rear tire.


Posted by: Phildirt---------------------

My good man nephron, you obviously know a bit about engines to ask such an intelligent question. Fuel injection on 2-stroke cycle engines is being driven by emissions and nothing else. A carbureted 2-stroke cycle engine makes very good power but the scavenging process is very inefficient when it comes to fuel usage. That wasted fuel becomes unburned hydrocarbons floating around in the atmosphere, just waiting to mix with other things (like oxides of Nitrogen to form smog).

It is direct injection (injecting fuel directly into the cylinder, somewhat analogus to diesel injection yet retaining a spark plug) and not port, throttle body, or crankcase injection that is applied to 2-stroke cycle engines. While it's difficult to retain all the power of a carbureted 2-stroke, there are some advantages; torque down low, improved fuel consumption, and improved fuel control (no jetting) while achieving similar peak power to name a few. Cost, complexity, and weight are not among them.

I'm fairly certain that all 4-stroke cycle engines will need to be injected (port injection) to meet the emission regulations in a short period of time as well. Just look what bikes are actually green sticker legal in California right now. Not the YZ426.

Anyway, I figure we'll all be riding injected off-road bikes (2 and 4 stroke) or not riding off-road bikes at all. I know which I'd prefer.


Posted by: nephron---------------------

Oh. :o

By the way, how's your 2 stroke fuel injection (port I take it) coming along for the 2003 Rev?

Jack


Posted by: Rich Rohrich---------------------

Quote:
Originally posted by nephron
This is probably why Pro Stock Big Chevy V8's running 6 second quarters run 2 Holly Doms, and not injection (well, besides the rules, hehehehe).


Actually carbs are a laughable attempt by the NHRA to "control" the cost of Professional racing. It's funny but Warren Johnson, Pat Musi, Reher/Morrison and countless others have come out in favor of EFI from a performance, ease of use, and cost standpoint. Anyone who has attempted to chase the mixture distribution problems associated with plenum based carb systems would give a left arm for the control afforded by port or direct cylinder injection.

Quote:
Originally posted by nephron

So, in "out and out" performance, I have to say that in 4 strokes, there's little difference, and absolutely no horsepower gain if the carb is set up by an expert.


There is no evidence to support that claim and clearly all the current evidence in racing formulas that allow EFI would prove your point completely wrong. Large bore short stroke high rpm four-strokes like the current generation of dirt oriented singles are equipped with carbs that are nothing but a series of major compromises. EFI on these engines would be a definite step forward irregardless of emissions considerations.

Quote:
Originally posted by nephron

When it all comes down to it, people end up going back to what they know, and fall back on simplicity. The current trend in high performance automotive is to go back to the carb. The carb will always have a devout following, for good reasons. :D


Only because people fear the unknown, not because they are reaching for an optimized setup. Your same arguments were bandied about when electronic ignition hit the streets. When was the last time you longed for a dual point distributor?

You are certainly entitled to your opinions but thankfully the move towards EFI and the improved performance it brings will take place with or without the blessing of the naysayers Guys like Phil are doing a lot to help speed up the process. Way to go Phil


Posted by: Phildirt---------------------

Rev!'s marketing must have failed if there is but one dirt biking enthusiast thinks that the 2-stroke displayed at the Indy show was port injected. It was an early prototype using the Ram Injection (Direct Injection) system from Bombardier (formerly known as OMC). The DI 2-stroke that Rev! is developing is being driven by imminent emissions standards and will only see production when it is fully developed. That may not be before the EPA has stepped in (2006 time frame).

Feedback generated from the DI bike has been very positive for Rev!, in that we're addressing the emissions situation with 2-stroke technology. There are people out there that would like one even before the government requires it.

BTW I didn't respond earlier because I was out enjoying the mild western PA summer on a Rev! prototype and a Beta Zero. I'm showered, sore and tired. I hope you all didn't let a good day pass you by pecking at the computer (now there's some technology that scares me)!


Posted by: Rich Rohrich---------------------

Quote:
Originally posted by Phildirt
BTW I didn't respond earlier because I was out enjoying the mild western PA summer on a Rev! prototype and a Beta Zero. I'm showered, sore and tired. I hope you all didn't let a good day pass you by pecking at the computer (now there's some technology that scares me)!


I'm with you Phil. We were banging out laps on my NitroPropane fueled CR125 and testing Eric's latest 2001 CR144 iteration. Everyone is tired , sore and grinning like idiots from all the fun


Posted by: spanky250---------------------

Quote:
Originally posted by nephron
This is probably why Pro Stock Big Chevy V8's running 6 second quarters run 2 Holly Doms, and not injection (well, besides the rules, hehehehe).
Correct me if I am wrong, but don't top-fuelers (7000-8000+HP) use injection, not carbs? I don't think you could get the extreme flow rate required by these fuel-eating monsters from a simple vacuum operated carb.


Posted by: KXKen---------------------

Top fuelers don't use carbs.


Posted by: spanky250---------------------

Quote:
Originally posted by Rich Rohrich
We were banging out laps on my NitroPropane fueled CR125
So what does that thing run like, Rich?


Posted by: nephron---------------------

Quote:
Top fuelers don't use carbs.


The reason Top fuelers don't use carbs goes all the way back to fuel they use-- 99% Nitromethane, CH3NO2.

Every internal combustion engine mixes air and another fuel of some sort…The purpose of the carburetor is to meter those two ingredients in just the right proportions, and every individual engine has a requirement for a specific proportion of liquid fuel and air. Try to push in too much liquid without enough air, and the engine won't run at all. That's the purpose of the turbocharger….to cram in a lot more air than a simple vacuum-induction can deliver.

Now…..suppose we were to find a way to run more liquid through our engines without increasing the air supply, and yet still have a very efficient combustion? That would add power, wouldn't it? Well, that's where Nitromethane comes in. An internal combustion engine can burn more than 2 ˝ times as much nitromethane to a given volume of air than it can even methanol, let alone gasoline. In the "process" of combustion of Nitromethane, mole per mole, approx. 1/3rd of a mole of O2 is elaborated. Hence the need for less "air", which is only 20% O2 anyway. Voila! More Power! That's how it works.

What these bigass Nitro motors run are high pressure port injection of somewhere in the range of 80-90% Nitromethane. Obviously, you can't make a carb "meter" that kind of air:fuel ratio, and it cannot be done.

Therefore the argument that the "fastest" cars in the world use fuel injectors and not carbs is superfluous. Here, the indication for injection is obviously not to optimize air:fuel ratios or that they're "better" than carbs, but because it's the only damn way you can shove nearly 100% fuel with no air into a combustion chamber of a motor spinning at 10000rpm! Comparison in this case isn't possible.

Quote by Rich:

Quote:
Actually carbs are a laughable attempt by the NHRA to "control" the cost of Professional racing. It's funny but Warren Johnson, Pat Musi, Reher/Morrison and countless others have come out in favor of EFI from a performance, ease of use, and cost standpoint. Anyone who has attempted to chase the mixture distribution problems associated with plenum based carb systems would give a left arm for the control afforded by port or direct cylinder injection


The only thing accurate about that statement is that high level execs in NHRA are attempting to change the Prostock "rules" to allow FI. The rest: Warren Johnson could care less. He's top dog this year. Pat Musi believes brother, believes in FI, since he and his Nitrous injected big block Camaro gets its nuts kicked in by fuel injected turbo charged Mustangs every week. Pat Musi has actually been crying foul about these cars, stating they're unfair and should be moved to another class (and bye the bye, he doesn't race NHRA, only NMCA and NSCA). And Reher-Morrison doesn't even make a fuel injected motor. They'll make you one, but all their up front custom motors are carbed. And lastly, the general idea of cost and converting all cars to FI is ridiculous. What makes all these Organizations (NHRA,NMCA,NSCA) great is the multiply different classes with specific rules applied to each. For instance, in Pat Musi's class (Pro Street in NSCA) both carbed and fuel injected cars are allowed. He chooses to run carbs.

2 final points: 1) The carb will never die. 2) I don't have any problem with FI, typically jump into new technology head first, and absolutely agree to its superiority in certain cases. To reiterate, I just think you'll gain even less on a 2 stroke than a 4 stroke, in which case Injection vs. Carb on a 500 hp bigblock Chevy is worth about 10 ponies and a little bit more torque lower in the curve. I can back those statements up also, if you'd like.

Jack


Posted by: Rich Rohrich---------------------

Quote:
Originally posted by nephron

The only thing accurate about that statement is that high level execs in NHRA are attempting to change the Prostock "rules" to allow FI. The rest: Warren Johnson could care less. He's top dog this year.


Actually the NHRA execs are trying to STOP EFI, and Johnson along with a few enlightened teams seem pretty pissed about it. WJ has come out in print numerous times in favor of EFI. He runs carbs becuase he has no choice.

Quote:
Originally posted by nephron

Pat Musi believes brother, believes in FI, since he and his Nitrous injected big block Camaro gets its nuts kicked in by fuel injected turbo charged Mustangs every week. Pat Musi has actually been crying foul about these cars, stating they're unfair and should be moved to another class (and bye the bye, he doesn't race NHRA, only NMCA and NSCA).



Musi's complaints have seemed to center around weight breaks associated with Turbos not with the use of EFI. Read closer, I never claimed Musi was an NHRA racer
Funny that the crate engines Musi built for Holley are EFI equipped even though Holley's bread and butter product is high end carbs. Must just be a coincidence.


Quote:
Originally posted by nephron

And Reher-Morrison doesn't even make a fuel injected motor. They'll make you one, but all their up front custom motors are carbed. And lastly, the general idea of cost and converting all cars to FI is ridiculous.



They sell to racers for the most part and class structure is predominantly carb based so it makes sense that their product line would reflect that, but it hasn't stopped them from coming out in favor of EFI as a better long term solution. Based on the dollar numbers that Warren Johnson quoted for the Dominator stock they have to keep on hand, it's clear that carbs at that level of racing are a false economy.
Drag racing is a poor example anyway, the rules structure dictates usage more than the relative merits of a technology. Once you step out of the tradition steeped world of straight line racing you'll find that EFI is the preferred technology in serious high level racing. Actually I think two-strokes have the most to gain, but the engineering involved to see the advantage for our use is more involved than that required on a four-stroke single.

Spanky - The CR runs like a scalded dog on Nitropropane but transitional response is not where I want it to be YET. The trick it seems is finding the balance between the carb's fuel curve and the distillation curve of the fuel. It makes for lots of opportunities to test different fuel combinations.


Posted by: nephron---------------------

Rich

Give me references, page numbers or internet addresses of WJ's supposed statement. If you think I'm going to believe that a couple DOMS, let alone a couple hundred DOMS, even begins to crack @ the price of running a several hundred thousand dollar car with 50,000 bucks in the motor alone, .....:silly:

Hell, they're probably cheaper than the fuel.

And I hope like hell we get to see Rev's 2 stroke fuel-injected bike, but like he said, it probably won't make it out til 2006, (or was that 2003:think ) I think it's a fine idea, and for the folks that can't live without the "brand new" technology for more than 2 weeks (without feeling ashamed :o ), that'll be great for them. I'm just counting on there being minimal performance/efficiency difference, and if you got the "jist" of REV! cycles themselves, they admit they're doing it only to satisfy the EPA.

But most importantly, this subject is nothing to argue about and I want you to know I'm not flaming you or pissed. Just trying to keep a good conversation going.


Posted by: Rich Rohrich---------------------

Quote:
Originally posted by nephron
Rich

Give me references, page numbers or internet addresses of WJ's supposed statement. If you think I'm going to believe that a couple DOMS, let alone a couple hundred DOMS, even begins to crack @ the price of running a several hundred thousand dollar car with 50,000 bucks in the motor alone, .....:silly:


He originally brought up the price comparison in his Speed Reading column in National Dragster, and then went into more detail with exact numbers in an interview he did with one of the drag racing magazines. Might have been Drag Racing USA. I don't know which one for sure as I don't save that stuff. I'm afraid you'll have to do your own leg work if you want to read the specifics as I'm not really that interested in appeasing your disbelief

Personally I'm putting my money where my mouth is and will have EFI on my four-stroke bikes LONG before it becomes the norm and it's not because of the EPA. :confused:


Posted by: helio lucas---------------------

someone bumped this thread so i will throw this..
http://www.autoblog.com/2008/08/12/...mnivore-engine/
it seems the 2 stroke engine might have some future. nothing less than lotus knows that and is researching along with jaguar, QUB and some others agency...
take a look



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