Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: miedosoracing on August 15, 2011, 04:02:56 PM
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LL 250B stock class. Here's what you should observe. How many 4 stroke KTM and Yamaha bikes are out there. Plus the fact that as we've stated, the fastest guys are on 4 strokes, I'd be willing to bet, sponsored heavily seeing what names they have.
Loretta Lynn's 2011 250B Stock Uncut ft Bell / Martin / Hill (http://www.youtube.com/watch?v=rs93wDnNFR0#ws)
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Zac Bell had the fastest lap at Lorettas all week with a 1:52.791. That guy was flying
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Not sure what you are getting at.
Enlighten me.
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Not sure what you are getting at.
Enlighten me.
The fact that when the riders in this class had a choice, they chose the 250 2 stroke over the 4 stroke. The orange and blue bikes I saw were 2 strokes.
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Thanks.
But wouldn't you also agree that 250=250 is a fair class structure to have.
I have been slammed on here before about its not fair.
That race proves it.
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Thanks.
But wouldn't you also agree that 250=250 is a fair class structure to have.
I have been slammed on here before about its not fair.
That race proves it.
Agreed.
Actually as muddy as that moto was I think the guys on 2 strokes were at a disatvantage.
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Thanks.
But wouldn't you also agree that 250=250 is a fair class structure to have.
I have been slammed on here before about its not fair.
That race proves it.
Are you asking me? Umm, I'm pretty sure I've NEVER slammed anyone for saying that is fair. Have pointed out multiple times here and Vital, that the 250 2 stroke isn't gonna win in pro class still, because the fast guys will still be on the 4 strokes. But atleast it gives the normal guy a chance to compete on a level playing field without having to spend thousands on a PC motor or rebuilds. I've even asked DC to allow the 2 strokes to just be completely bone stock in the motor. He said they would not be able to protect from cheaters. etc etc etc. I'd like to compare a big bore non ported 250F bike against the HP from a PC bike. If I was a 35th guy, I'd have to ask myself, is it really cheating with a big bore, compared to a PC bike? I'd love to see a completely stock pro class.
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Thanks.
But wouldn't you also agree that 250=250 is a fair class structure to have.
I have been slammed on here before about its not fair.
That race proves it.
Are you asking me? Umm, I'm pretty sure I've NEVER slammed anyone for saying that is fair. Have pointed out multiple times here and Vital, that the 250 2 stroke isn't gonna win in pro class still, because the fast guys will still be on the 4 strokes. But atleast it gives the normal guy a chance to compete on a level playing field without having to spend thousands on a PC motor or rebuilds. I've even asked DC to allow the 2 strokes to just be completely bone stock in the motor. He said they would not be able to protect from cheaters. etc etc etc. I'd like to compare a big bore non ported 250F bike against the HP from a PC bike. If I was a 35th guy, I'd have to ask myself, is it really cheating with a big bore, compared to a PC bike? I'd love to see a completely stock pro class.
The 250 class at the recent NZ national champs was won by a pro on a 2T, just.
His results and times on his modded 2t were about the same as the results and times of the other pros on modded 250f's. He is also the manager of the yamaha team in NZ so guess he can ride what he wants.
250 vs 250 is totally fair in my opinion mod or stock, pro or clubman.
The little extra power from the 2t is offset by the easier to manage 4banger.
just my opinion of course though.
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I don't even think 250 vs 250 is fair. Yes the 250 2 stroke makes more power everywhere but in more of a reliable sense long rod small piston perfect mid range bike, but the reason the 250 4t does so well is because of the fact of running such a large piston with such a very short stroke(CHEATING). This sort of thing is actually outlawed in certain race series. I thought I pointed this out in the other thread. 4 strokes by them self don't make more power, its how the motor laid out. If this was replicated with the 2 stroke, lets just say we wouldn't be having this discussion right now and that there would be a 4 stroke forum complaining about it.. ??? The best part if you were to replicate this with a two stroke is that it would lower engine weight by compressing the motor a bit, leaving you with a smaller lighter bike.
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Trololol 4 strokes? whats that?
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lol
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(http://i53.tinypic.com/6z6frc.jpg)
Crude but its sure as hell easier to explain to people who don't understand.
This also go hand in hand with more kids dying of late, they're riding larger bikes that have been slightly detuned, so in other words this has the potential to be a lawsuit.
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HOLY SMOKES DOC!1 never knew this!
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Negative nancy.
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I am sorry Factory but you have it all wrong.
Comparing the difference in stroke length between 2's & 4's is pointless.
A 2 stroke "NEEDS" a long stroke to give it sufficient porting area in the bore to "Breath" to its potential.
The exact same reason as a 4 stroke "NEEDS" as large a bore as practicle to allow sufficient porting ( ie Valves ) to Breath to it's potential.
Thats why 2 strokes are "undersquare" & 4 strokes are "oversquare".
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ther were a bunch of 2 strokes in the class but more 4 strokes i watched that class while i was there ,i think a third of them was 2stroke
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How am I wrong? Short rod = more rpms So when you throw a larger piston you will regain lost torque, which also allows you to run larger valves. This is their way of pulling more power out of the 4 stroke engine while making it lighter in the process. As for porting, the majority of 2 strokes already use case induction, and there are such things as bridges in the middle of ports to keep rings on :-X. What I am talking is plausible, and this is the reason of success with the modern 4 strokes. These motors are not equal in anyway. In the last 20 years the 4 stroke motor has been transformed while two strokes remain similar to 70's/80's design.
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Short rod = more rpms. Yes i wasnt argueing that.
You said to replicate it in a 2 stroke. Best of luck.
As I said 2 completely different types of motors that achieve things a different way.
How is a 250 2 stroke going to get enough port area with a 55mm bore.?
Not sure what you mean by port bridges & case induction. You can only move the ports around a bore so much before you run into turbulence problems.
2 stroke MX engines do not need high rpm's.
4 stroke engines can NOT make good horsepower Without high rpm's. AND THAT IS THE PROBLEM WITH THEM.
Short rod = high rpms = $$$$$
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but wouldn't a larger piston on short stroke increase torque and top end on a two stroke? It may be not be logical, but neither are $20,000 4 stroke motors.
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Piston size dosn't really play a part in torque.
Normally the longer the stroke the higher the torque.
But for any given rpm the longer the stroke the higher the piston speed.
4 strokes by design need to run at very high rpm's to make power even close to a 2 stroke.
Look at Moto GP . The modern engines are doing 18,000rpm to make 240Hp out of a 1000cc engine.
Go back 10 years the 500's were putting out 210Hp at 13,000rpm.
The motors are 100% bigger turning 30% more making only 13% more Hp.
Half the problem with the 4 stroke is the piston skirt length or lack of.That thing wears so quick its stupid.
But to lengthen the skirt the piston would then be too heavy for the rpm,s they are doing. The designers have dug themselfs abit of a hole they can't get out of.
Ive said before they are a brilliant peice of race engineering for a factory race team but for the public :-[ >:(
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Long stroke 2T motors are considered to have a traction advantage as well.This was more or less pioneered by Maico and eventually all 250 2Ts copied Maico's engine geometry (don't forget the YZ 68mm stroke long rod upgrade kits).
When you are comparing 2 cycle and 4 cycle engines don't forget as well that per unit time the 2T engine generates two power impulses to the 4T$ one impulse.Soiricho Honda's solution was to spin the 4T engine twice as fast to generate the same output.That is why we are where we are now.
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FactoryX,
How is designing an engine the way it has to be, to be competitive, CHEATING?
It's what you do as an engineer. A 4t has bugger all torque, when compared to a 2t with a comparable level of tune, so 4ts have always had to go the route of revs to get their HP. So be it. HP is a product of torque, multiplied by revs, then divided by a constant (5252).
TMKIWi has it right.
Now, tech like DFI may allow 2ts to get more mixture into the combustion chamber with a short stroke format (by replacing air charge lost by shorter stroke / shorter duration transfers and inlets) - it depends on the tech used for the pressure/ volume of the stratified charge. That's where the arguments put up against DFI being heavy / complex can come in - to get very high pressures / volumes of the stratified charge, for short stroke 2ts, is going to require tech / parts that will be far to bulky for dirt bikes, at least for the foreseeable future. The DFI outboards seem to have gone to over square dimensions, and bigger capacity engines, ironically - part of the weight benefit of 2ts , you can use a bigger engine, when you are dealing with an Output oriented sport / market.
Let the 4ts rev their tits off - they just keep getting 'pipier and pipier' (11 / 12krpm 450s, hitting the rev limiter constantly - I never thought I'd witness that).
Mind you, Moto 3's regulations, limiting revs to 13,000 (lower than most std 250f MXers rev to) rpm will, keep things in hand - the customer spec Honda 250 is claimed to have 35.5 KW = 47.6 HP, that shows what is still to come with 4ts, without mind blowing revs. They are allowed to use 81mm pistons, yet Honda has gone only to 78, as with the rev limit set, they have seemed to believe that there's no need for the max. sized piston. And that HP level, Has to be produced at a noise level much lower than allowed at the GPs (115Db), for those bikes to be run at race tracks around the world. Check out the huge, under case uffler it has. The GP bikes, will probably have open , or near to it, pipes.
To make Moto 3 interesting, the homologated engines, are going to have to pump out 55 /65 HP, to get the speeds of the 125s. It will be interesting to see what is to come.
Though, it should have been a class that allowed 4ts And 2ts, with spec / cost controls - better still, it Should have been 125s, with spec / cost controls. That would have delivered low cost racing, much more effectively.
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What I pointed out is exactly why its considered cheating. A modern two stroke piston is 66mm-68mm, while a modern 250 4t piston is 78-80mm... A 78mm piston is about enough for a 370cc big bore kit for a 250 2t. That's why its cheating. And at this point I agree with TMWIKI and you as well.right hilarious.
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FactoryX,
The DFI outboards seem to have gone to over square dimensions, and bigger capacity engines, ironically -
The outboards were actually oversquare to start with. It was needed to keep the V-Block engines compact.
FactoryX,
Mind you, Moto 3's regulations, limiting revs to 13,000 (lower than most std 250f MXers rev to) rpm
Easiest way to make 4 strokes more reliable.
RPM's & noise control. Drop both and you have a more reliable motor.
Less HP but I don't care. ;D
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It's not considered cheating by anyone I've ever come across, until you. ::)
Put it to the uninitiated - all they will care about is the capacity. When I point out to people that the 4ts, that commentators are usually raving about, are up to twice the capacity, by the rules, Every time, I get a comment along the lines that that is unfair / cheating. The general public, actually have a good grasp of what is fair, and what is not, when they are informed of the current, biased rules.
Short Stroke - It is how most modern 4ts are made. So be it. I've no problem whatsoever with it, if engineers want to go that way in engine design. I've actually put forward in other sites, that I'd like to see a true 'open class', with 2ts and 4ts, with someone like Buell, Katech, perhaps making a modern, long stroke, big capacity, utterly minimalistic, push rod engine, for dirt use. Idiots could not get away from their '450 4ts are the greatest bikes ever made', mindset. It was quite hilarious. Usually, those same drongos loved their big old push rod engined muscle cars. And despised the modern car engines. Classic. I grew up with BSAs and CCMs in the family, and loved the 630cc CCM engine that was in one of the bikes. Whilst rabidly charging around on 125 2ts, and stirring up my Dad and Uncle about their old boomers, at the same time.
Let 4ts be screaming, peaky engines, it's not what I want from an engine. That's why I ride a 5500 / 6000 rpm, 500 2t.
As for the stroke on outboards, well, short stroke can force use of a wider V, as against the narrower V a longer stroke can allow. Depends on what you regard as compact / want to compact. It's a case of either, either. My 500, has an over square bore and stroke - indeed, many open class 2ts have been over-square, as many were developed from 250 modules. A matter of expediency, for many manufacturers, but also, it might have been exactly what they wanted from their engines. Oh, by the way, I've owned several Maicos, so don't bother with trying to inform me how 'magic' their engines were / are - I know a fair bit about them., and I am quite a devotee of the brand..
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I wasn't going to inform you about maico engines, as I know nothing of them. :D The only reason this hasn't popped up before is that people have not noticed or did not realize that there was that much of a difference. You're right, TMKIWI is right, but then I have point as well. Either way 2 strokes have to change or face death, as people are to stupid to understand otherwise. There are still a handful of people who ride 2 strokes, but then again there are still a handful of people who ride 3 wheelers, fl250/350/400s, 2 stroke utility quads, etc..
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You blow me away when you say stuff like that. Seriously two strokes are becoming more popular where I'm at. When you say 'face their death' I say BS they are coming back.
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Not in America, its gone to point of being political.
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Simple fact is that regardless of what the manufactures make to sell, the RULES dictate what people will buy - even if they don't race.
Basically you have 3 types of consumers in the dirt bike market. Racers (MX'ers, desert, enduro, etc), and trail riders or newbs. The trail riders sit on the fence between off-roaders and newbs but that is not a derogatory statement.
Racers buy a bike as a TOOL. They want the best product for the job at hand. No one is going to buy a bike that is not going to be competitive in their chosen class. Fortunately for the 2T, the off-road rules are based on capacity rather than stroke and the 4$ are not given a handicap. This make the 2T often a better TOOL. For these people, the products from the manufacturers are valid. They create TOOLS based upon the RULES, (not the RULES based upon the TOOLS). Want proof of this? Do you see a 175 class? A 200 class? A 350 class? No, but the manufacturers build these bikes for two reasons; 1) because there are people who will buy them to use as a better TOOL for their job or 2) there is somewhere with flexible enough RULES to allow their use. In American Enduros/Hare Scrambles etc, it is 0-200cc. In Europe, E2 is 0-175cc. (MX2 is 125-150cc).
Serious Trail Riders buy TOOLS. That is why the XR and KDX still sell today and why KTM is the largest producer of off-road vehicles. For all these groups, those who buy TOOLS, the manufacturers are in constant competition to build a better tool.
For the casual buyer and the newb...they have to have what the PROS have. Why spend $7000 on a much more useful and reliable KDX or KLX when you can have a KX450F just like Villapoto! Then drop $100 on Monster/PC graphics and nifty matching riding gear! THESE ARE THE PEOPLE THE MANUFACTURERS ARE TARGETING. The racer will always buy the best TOOL. The newb kid that wants to look like Dungey or the newb big guy thinks a 250 is too small for is 200 lb butt. The Racer will drop $20k into suspension and motor mods; the newb will just let it hand grenade and buy a new one!
Now back to my first statement. The FIM and AMA have taken responsibility for the SPORT; like is their charter. They dictate the rules. If you want to race, you will use X range cc motorcycle. You as the consumer/competitor choose the best TOOL for the job based upon your ability with that tool, the RULES, and you budget.
@Factoryx - What you are saying is correct but...you can only go so far before other variables come into play. That is what TMKIWI et al are trying to say. No so much that you are wrong but that you have gone too far in your measurements for it to work as you intend.
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that highly oversquare piston is what put 4 strokes back in motocross, as it allowed them to rev high to find their horsepower. Totally fair in my opinion - a 250cc engine is 250cc no matter how you slice it.
And THAT is the beauty of direct injection. Because now, 2 strokes can be oversquare!! They no longer need to depend on port timing like conventional 2 strokes. Check this out: one of the DI 2 stroke outboards (evinrude etec) is running 433cc cylinders at 91mm bore X 66mm stroke. Not as oversquare as the 450F's, but oversquare nonetheless. Can you imagine an open class 2 stroke that revs to the moon?!
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Can you imagine an open class 2 stroke that revs to the moon?!
Hell yeah!
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that highly oversquare piston is what put 4 strokes back in motocross, as it allowed them to rev high to find their horsepower. Totally fair in my opinion - a 250cc engine is 250cc no matter how you slice it.
And THAT is the beauty of direct injection. Because now, 2 strokes can be oversquare!! They no longer need to depend on port timing like conventional 2 strokes. Check this out: one of the DI 2 stroke outboards (evinrude etec) is running 433cc cylinders at 91mm bore X 66mm stroke. Not as oversquare as the 450F's, but oversquare nonetheless. Can you imagine an open class 2 stroke that revs to the moon?!
Unfortunately a 2T engine is always going to rely on the ports and the pipe to do the work.They are the heart an soul of a Two Stroke.Over square dimensions have heavier pistons which severely limit RPM.That's why a 250/450F needs a minimalist slipper piston to survive the RPM the stroke is capable of. Sooner punters get over the DI dream the better because it isn't going to happen, well probably not until Ficht or Orbitals patents expire.
Over square dimensions didn't put the 4T back on the map it was moving away from plain bearing bottom ends to roller bearings in the big end.
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OK, now we are getting into semantics. The roller bearings allowed for the higher rotations capable with the shorter stroke. Improvements in heads and the overall metallurgy also played a role in all this, but the point is that the advancement of 4$ technology to produce more horsepower came at a price and that price is high revs. The tax placed upon that cost of higher revs, regardless of engine design, is reduced reliability.
Back in the day, the 4$ was dead reliable because it was long stroke (compared to a 2T) and turned slowly. Today, the tables are turned with the 4$ having a short stroke and revving to the moon and the 2T being considered reliable precisely because of the lower revs per HP produced.
@2T Institute - Disagree with you completely. DI may not be the answer of all our ills but we will see it and soon. It is already available in outboards and snowmobiles. It is only a matter of time. And the reason may surprise you. They will not produce it for America though we may see it here. It will be produced for the developing markets (India, China, Brazil) where the 2T is more common and emissions more of a concern.
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I think you guys all got off track here. Who cares about all that stuff you just chatted about. In MX it comes down to on the track. The videos all over Youtube show that cc vs cc is very fair racing. The 4 strokes still are winning all over, but there are more and more 2 strokes coming back. So from the beginning of this post, when it was stated cc vs cc is equal. I agree. Maybe not on your charts or calculators, but in the real world. Neither one of them are whooping up on eachother. But what my point was, that for cost and other reasons, when someone has to go out and purchase their own bike and pay for parts etc, they chose 2 strokes if they could. They weren't any faster than they were if they chose the 4 stroke, but they probably have a lot more money in their pockets.
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<snip>
And THAT is the beauty of direct injection. Because now, 2 strokes can be oversquare!! They no longer need to depend on port timing like conventional 2 strokes.
<snip>
Could you please explain how DI could accomplish such a thing?
-It is, after all only another way of delivering fuel, not air, into the combustion chamber.
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Can someone please explain undersquare and oversquare? I am having a hard time keeping up.
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Undersquare - stroke exceeds bore.Example:72mm stroke by 64mm bore 250 2T engine.
Oversquare - bore exceeds stroke.Example:any modern 4T.
Square - bore equals stroke.Example:typical 125 2T.
As 2T Institute has stated a DI 2T would still be governed by port timing,the advantage of a DI 2T is that at lower rpms due to the fuel/air charge being injected into the combustion chamber after the exhaust port is closed you would not experience charge losses out the exhaust port (at low rpm).
This would result in an increase in low rpm torque,and coupled with other efficiencies related to DI,would create a new generation of 2T capable of beating the 4Ts under the present rules.There,I've said it,I think a DI 125 2T could beat a 250 4T (for example) - delusional mensch that I am. ;D
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As 2T Institute has stated a DI 2T would still be governed by port timing,the advantage of a DI 2T is that at lower rpms due to the fuel/air charge being injected into the combustion chamber after the exhaust port is closed you would not experience charge losses out the exhaust port (at low rpm).
This would result in an increase in low rpm torque,
Correct.
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And THAT is the beauty of direct injection. Because now, 2 strokes can be oversquare!! They no longer need to depend on port timing like conventional 2 strokes.
<snip>
Wrong sorry.
- delusional mensch that I am. ;D
Correct :P
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OK, now we are getting into semantics. The roller bearings allowed for the higher rotations capable with the shorter stroke. Improvements in heads and the overall metallurgy also played a role in all this, but the point is that the advancement of 4$ technology to produce more horsepower came at a price and that price is high revs. The tax placed upon that cost of higher revs, regardless of engine design, is reduced reliability.
Back in the day, the 4$ was dead reliable because it was long stroke (compared to a 2T) and turned slowly. Today, the tables are turned with the 4$ having a short stroke and revving to the moon and the 2T being considered reliable precisely because of the lower revs per HP produced.
@2T Institute - Disagree with you completely. DI may not be the answer of all our ills but we will see it and soon. It is already available in outboards and snowmobiles. It is only a matter of time. And the reason may surprise you. They will not produce it for America though we may see it here. It will be produced for the developing markets (India, China, Brazil) where the 2T is more common and emissions more of a concern.
Yeah sure whatever you reckon. 4T engines don't rev to the moon they make peak powerat 11,500 or so 250F
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TMKIWI - that's why Evinrude didnt consult you when they were designing their oversquare DI engine. But i admit, i should have said DI's are no longer "fully" dependant on port timing. When the injector releases its spray into the combustion chamber is now at the discretion of the engineer, not the piston
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Not in America, its gone to point of being political.
I am in America. Most racers here don't give a hell about the politics of motocross, they just like to ride, race, have fun, and compete! And most of them are coming back to smokers. the top three to five racers in every class here are on smokers.
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Its besides the point, what I stated was the fact that there are only a few new 2 strokes being sold in the united states today, this goes for ATV's as well. As for political, 2 strokes are considered dirty while 4 strokes are media biased. :-X Local racing is one thing, Nationally coverage races are another.
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Yeah sure whatever you reckon. 4T engines don't rev to the moon they make peak powerat 11,500 or so 250F
Sorry, I guess saying the "rev to the moon" is an exaturation. However, many 2T 250's are making peak at about 7.5K. Much lower than the 11.5k revs of the 250F you reference. Rev the 2T that high and you'll think you are going to the moon! A motor making peak hp with less revolutions will generally be more reliable than one spinning faster.
About dirty 2 strokes: I am not going to look it up again so I won't quote, but the 4$ has cleaner emissions in all but 1 measurement, the worst one. However, referencing the engine tested in the report I was reading, the same 2T outfitted with DI made more HP, better fuel economy and MUCH lower emission numbers across the board than the equivalent 4$'s they were comparing it to.
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I think rev to the moon was more referring to what we know of on older 4 strokes or even current mx 2 strokes. Take a XR250 and compare the RPM to a CRF250. You will see it matches approximately with increase in RPM's to power. Same can be said with 2 strokes. They can be set up to rev much higher, take a look at GP 125's. BUT, they also have 0 bottom end. So on an MX track, it would outright be horrible. But 2 or 4 strokes, to increase peak HP, you can increase RPM's.
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TMKIWI - that's why Evinrude didnt consult you when they were designing their oversquare DI engine. But i admit, i should have said DI's are no longer "fully" dependant on port timing. When the injector releases its spray into the combustion chamber is now at the discretion of the engineer, not the piston
I'll try again...
That injector injects fuel (and depending on injector type, a tiny bit of air to help atomize the fuel) into the combustion chamber, but in order to burn that fuel you need a lot of air, and that air is delivered the same way as it is in a normal carbed two-stroke. Any improvement in the power spread (due to DI) will be a result of improved engine management.
Now, drastically reduced emissions and reduced fuel consumption aint bad either...
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DI is pretty cool with respect to emissions. Would be as well on a 4T. The poster that said the DI 2T was cleaner than the 4T was probably referencing a comparison of 2T DI to a carb 4T. Any high performance 4T will have valve overlap -- i.e. the intake and exhaust valves are open at the same time for some short period. That allows unburned fuel air mixture to short circuit the combustion chamber -- just like from xfer to exhaust in a normal 2T. The degree is less but the same effect as far as emissions. By making the 2T DI, you end up with a bike cleaner than a 4T and therefore get the EPA and Sierra Club off our backs (for that factor anyway -- other "reasons" will persist of course). I also like the lower fuel use aspect. If you can go riding on 2 gallons on a trail that use to take 3 gallons, well -- you just more than made up the extra weight of the DI gizmos.
KTM, Yamaha, GasGas, HBerg, are you listening? If I can get a green sticker 2T in good 'ol CA for the same price and less weight than a 4T, with equivalent chassis performance and at least as much HP as a carb 2T I will buy it tomorrow! Make them street legal in CA and I might have to buy 2 of them!
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I just saw 1 2-st in the vid, where,s the 125 jr. video thanks. I have a 2mm longer rod in my cr125 mod bike, much higher revs,top end pulls further. This is what a 250 2-st needs.
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TMKIWI - that's why Evinrude didnt consult you when they were designing their oversquare DI engine. But i admit, i should have said DI's are no longer "fully" dependant on port timing. When the injector releases its spray into the combustion chamber is now at the discretion of the engineer, not the piston
I was talking about 125's & 250's.
Nothing wrong with oversquare in larger motors. ;D
As I said in an earlier post chris2t, the ETEC motors use an existing carby engine design.
Being short stroke has nothing to do with DI.
P.S. You would be surprised what they have consulted with me about.
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A 2 stroke CAN be made to no longer be Fully dependent, or have any dependency on Any inlet ports, other than the injector itself. That it Can be done, sure as hell doesn't mean it will be done.
DFI can be made to deliver the Entire fuel / air charge to the combustion chamber. But, it's not very practical - a very uncalculated (just to cover myself with regards to pedants) assumption is that the 'charging system' would be very large / bulky /heavy/power draining etc. etc. With no charge generating parts, the carriage of sufficient air / oxygen charge storage would be rather 'difficult' to deal with......... :o :D.
So. it is a very doubtful thing that it would ever appear on a motorcycle, of any type.
For 2ts to remain available for Any applications, in the future, more than just a carb is going to be needed. AST, trapping valves, AR, and Many other techs are out there to enable continued use of carbs. EFI, just an electronic carb, used with the previous sentences techs, is a possibility, to meet coming regulations. I recently had a very serendipitous encounter, and a subsequently long discussion, with a high level person from Victa Australia , and their commitment (and, now, Briggs and Stratton [sp?], their 'owners' ) to 2ts for future use over 4ts was very encouraging. DFI, is just another way to deliver fuel / air charge, to deliver improvements - more than just the environmental and fuel economy that is so largely at the forefront for it's coming use. But environmental issues and economy are what is focused on with 2ts (and 4ts), by legislators. Unfortunately, the very real advantages 2ts already have in terms of production environmental costs, and 'whole of life' environmental costs, has been swept under the carpet
The posting of the Athena video (and the patent numbers) shows that DFI, as most tend to know it (coming in from the Cylinder head), is far from the only solution. When you see companies such as Athena doing this, and, hopefully, having it applied, you know there are a lot more (in terms of numbers)viable solutions than just variations on Orbitals Stratified charge DFI.
Short stroke / long stroke - both have been around for along time. Both configurations (and the mid ground between each extreme), offer advantages. And disadvantages.
4ts went to short stroke for high power applications long, long ago. Check 4t road racers/ multis from the sixties. Your basic XR250 was a very over square engine compared to the vast majority of 2ts. The over-square dimensions have just got a bit more extreme. What's the general F1 V8 dimension - 90/92(?) x 39.?mm, now? Ironically the KTM 350 has lesser over-square dimensions than the 'Berg 390 / KTM 400. The previous 'split case 'Berg 450 was a higher bore stroke ratio again. Close to, or at 1.8 to 1, I think? Yet it wasn't set up to be much of a 'screamer'.
For dirt use, we are talking about limited traction. So, we don't use engines highest levels of tune - not even if they are true tiddlers - we need tractability and a reasonably wide spread of power. Electronics, further development will help with usability issues, when going for higher and higher outputs - but, as ever, it means more complication, and higher costs. So goes it.
There are people here getting Long Rod set ups, confused with long stroke set ups.
I'd be happy to just play with a simple Keihin carb, but, I'll deal with Whatever is required to keep 2ts available to me. And I'll be trusting (naive?) enough to expect that it will deliver real improvements, just as the majority of new tech has done during the development of ICE engines.
DFI kits have been used in Asia, to clean up the emissions from millions of little 2ts engines, that are in use there.
2tInstitute:
You've seemed to be a bit negative with regards to DFI, for quite some time, here. These are questions, not attacks, on you:
Would I be correct in thinking it might come from a perspective of it not being the Only solution available to apply to 2ts?
I can see that as being a very valid point, hence my always citing other techs available for use in 2ts. I share that line of thought to a certain extent.
I do, however, think DFI may become the 'norm', as, like so much in engineering, the one solution is inevitably focused on by manufacturers, if it has proved to be viable, and cost effective - if only by it's sheer weight of numbers. A simple example, being the almost exclusive use of the Keihin FCR carbs (a lower tech example, certainly, but a hell of a carb) with 4t dirt bikes, up till recently.
Bringing us , the long way, back to current 4t ascendancy over 2ts :D :'(
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You say negative I say realistic. Comes down to a 2T engine not playing by rules, it can be done though and the more time you spend at WOT the easier it becomes.A 125 with DFI and a dry bottom end(fuel-less) would not see out a 30min moto or a proper GP length road race without a complicated big end/main bearing oiling/cooling system, or you would have to inject fuel into the crankcase(there goes the emissions) etc etc etc, it just gets harder and more complex with yet anonther ancilary system with a carb you have that and a cable.
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... without a complicated big end/main bearing oiling/cooling system...
It doesn't have to be complicate. It just has to be wet. Oiling the mains has nothing to do with the emissions. It's just another part of the process because of the scavenging effect.
Cars, boats, and other engines are using EFI and DFI. Only cost and people unwilling to change are holding back the 2T Motorcycle.
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Thanks.
But wouldn't you also agree that 250=250 is a fair class structure to have.
I have been slammed on here before about its not fair.
That race proves it.
Are you asking me? Umm, I'm pretty sure I've NEVER slammed anyone for saying that is fair. Have pointed out multiple times here and Vital, that the 250 2 stroke isn't gonna win in pro class still, because the fast guys will still be on the 4 strokes. But atleast it gives the normal guy a chance to compete on a level playing field without having to spend thousands on a PC motor or rebuilds. I've even asked DC to allow the 2 strokes to just be completely bone stock in the motor. He said they would not be able to protect from cheaters. etc etc etc. I'd like to compare a big bore non ported 250F bike against the HP from a PC bike. If I was a 35th guy, I'd have to ask myself, is it really cheating with a big bore, compared to a PC bike? I'd love to see a completely stock pro class.
The 250 class at the recent NZ national champs was won by a pro on a 2T, just.
His results and times on his modded 2t were about the same as the results and times of the other pros on modded 250f's. He is also the manager of the yamaha team in NZ so guess he can ride what he wants.
250 vs 250 is totally fair in my opinion mod or stock, pro or clubman.
The little extra power from the 2t is offset by the easier to manage 4banger.
just my opinion of course though.
Darryl King is something else though. Plus he is about 50 years old. To win the lites class is an amazing result and shows really how good he is. Could be the last man to win a national lites championship on a two stroke ever. Unless we get out way. In respect to some of the other posts though, I do think that some peoples desires completely outweigh reality. 2T institute makes some very good points that I completely agree with.
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Darryl King is something else though. Plus he is about 50 years old.
42 Acually. :P
Question for our American readers.
I have been trying to work out how quick DK really is.
At the World Vets he is always diceing with Doug Dubach for the win.
How quick is Dr. D these days.Would he make a main ?
Just trying to put things in perspective.
Cheers.
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He could qualify for a national for sure. Im not sure where he would finish though
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I'm gonna say Doug would maybe qualify. But he would get smoked by someone like Ryan Hughes. So, the question would be, where would Hughes be in the pack of 40. I'm gonna say Top 20, maybe top 15, so Dr. D would probably be close to the tail end. JMHO.
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... without a complicated big end/main bearing oiling/cooling system...
It doesn't have to be complicate. It just has to be wet. Oiling the mains has nothing to do with the emissions. It's just another part of the process because of the scavenging effect.
Cars, boats, and other engines are using EFI and DFI. Only cost and people unwilling to change are holding back the 2T Motorcycle.
I don't think your grasping the concept of what fuel does in the crankcase.
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I agree with 2T in that if DI makes it to bikes the last we will see is a 125.
If we do get DI it will start with relatively low reving large capacity off road bikes first.
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... without a complicated big end/main bearing oiling/cooling system...
It doesn't have to be complicate. It just has to be wet. Oiling the mains has nothing to do with the emissions. It's just another part of the process because of the scavenging effect.
Cars, boats, and other engines are using EFI and DFI. Only cost and people unwilling to change are holding back the 2T Motorcycle.
I don't think your grasping the concept of what fuel does in the crankcase.
Why not explain then ;)
-a lot of cooling, mainly of the big end bearing.
On the other hand Ski-Doo seems to have solved that part of the puzzle as well with their E-tech's.
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I agree with 2T in that if DI makes it to bikes the last we will see is a 125.
If we do get DI it will start with relatively low reving large capacity off road bikes first.
For once, I have to disagree with you. I think we will see it on the SMALLER engines first. The Lawn and Garden industries will be hit hardest with any change in the emissions laws as the marine and motorcycle industries have adapted to 4$ or DI already. 2T motorcycles in the first world countries are a very small percentage and would not put up much of a fight if they were legislated away. However, in the third world (or more PC: Developing Nations), the small bore 2T is the predominant form of transportation and a large contributor to the emissions pollution. That is where DI will have the biggest effect.
Yes, there are engineering challenges, but nothing that can't be overcome. Only the cost/desire limit it.
2TInstitute: You answered your own question. On the other hand Ski-Doo seems to have solved that part of the puzzle as well with their E-tech's.
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I agree with 2T in that if DI makes it to bikes the last we will see is a 125.
If we do get DI it will start with relatively low reving large capacity off road bikes first.
For once, I have to disagree with you. I think we will see it on the SMALLER engines first. The Lawn and Garden industries will be hit hardest with any change in the emissions laws as the marine and motorcycle industries have adapted to 4$ or DI already. 2T motorcycles in the first world countries are a very small percentage and would not put up much of a fight if they were legislated away. However, in the third world (or more PC: Developing Nations), the small bore 2T is the predominant form of transportation and a large contributor to the emissions pollution. That is where DI will have the biggest effect.
For the two-stroke in the developing nations, it's already there. -Google "Envirofit two-stroke". Otherwise I agree with the quote from TMKIWI above.Yes, there are engineering challenges, but nothing that can't be overcome. Only the cost/desire limit it.
2TInstitute: You answered your own question. On the other hand Ski-Doo seems to have solved that part of the puzzle as well with their E-tech's.
I don't think 2TI want to be linked to that quote, if for noting else, my less than perfect English :P
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I agree with you vintageblue on the 3rd world issue but as teriks said that is already being delt with.
What I was talking about was "High Perforance Engines".
Making DI work in a 13,000rpm screamer race engine is alot harder to achieve then in a low horse power scooter or weed wacker.
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In another thread it appears that an Athena DI equipped Aprilia 50 (?) is revving to at least 11,500 rpm so maybe we are closer then we think. ;D
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KTM already has a DI 300 exc that is working. they will release it when emissions require it. all the problems have been overcome so all there is to do is wait until the emission laws are strict enough to make DI on a 2 stroke necessary.
This is a quote from the July issue of Australasian Dirt Bike Magazine from Rob Twyerould who is KTM australia's tech guru.
" there is definitely a well developed prototype at KTM, but they are waiting for the next round of emission restrictions to be announced before pushing forward. KTM has developed and patented its own mechanical fuel pump system and a very compact oil delivery system to the bottom end bearings and the whole bike works really well. While there has been some reasonable performance improvements the real advantages of the system are in emissions and fuel economy. so the motivation for bringing to market will only come with the new emission targets."
A couple of questions i have tho.
1) with a self lubricating bottom end, will that mean there is no need to premix?
2) with no unburnt fuel and air escaping out the pipe will there still be a need for an expansion chamber?
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A couple of questions i have tho.
1) with a self lubricating bottom end, will that mean there is no need to premix?
2) with no unburnt fuel and air escaping out the pipe will there still be a need for an expansion chamber?
Question 1: No primix.
Question 2: I think yes, but maybe a bit different then normal. Not 100%.
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2) with no unburnt fuel and air escaping out the pipe will there still be a need for an expansion chamber?
2) with no unburnt fuel and air escaping out the pipe will there still be a need for an expansion chamber?
Yes.
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Etec sleds use grease filled bearings, they also have oil injection to the lower end.
Yes fuel cools the bottom end on a race engine.
IF ktm has a injected 300 how come nobody has ever seen it or ridden it? It is a yeti/yowie/sasquatch ;D if at all the would have is a throttle body in place of a carburetor. Not direct injection.
Most motorcycles in developing and developed Asian countries are already 4 T powered.
A performance two stroke will always have a chamber