Rumours,Rumours!

[2T Institute]

For the 100 millionth time.............

Sleds have a CVT and that allows a narrow operating rpm and on/off throttle applicatons, which like a outboards lend themselves to EFI.

ECU's have trouble coping with the different demands on fueling between on and off pipe.

Free or cheap pipe calculators are worth every cent you pay for them There is a lot more to making a good pipe than punching in a few numbers into a program.

Trouble is getting enough power in the ECU to cope with the rapid change in dynamics that the pipe causes. That is expensive and cause packaging contraints. Which on a sled or a Outboard are not an issue.
  
Right now nobody wants to spend the $$$ to make the ECU.

EDIT
I haven't seen any dyno charts yet

[SachsGS]

In theory,and I'm thinking aloud here,if the ECU could keep up with the increasing RPM of a 2T and ALWAYS inject fuel into the combustion chamber after the exhaust port closed at the correct time before TDC ,an expansion chamber would not be needed?The reality is that due to time constraints the injection timing has to be advanced relative to increasing RPM to the point where the exhaust port is open at a certain engine speed.Hence, an expansion chamber is still needed and the ECU,given the present level of technology,has great difficulty making this transition.With this in mind,wouldn't it be easier to adapt DI to a relatively low RPM 500cc motocrosser then a screaming 125?    

[ford832]

For the 100 millionth time.............

Sleds have a CVT and that allows a narrow operating rpm and on/off throttle applicatons, which like a outboards lend themselves to EFI.

ECU's have trouble coping with the different demands on fueling between on and off pipe.

Free or cheap pipe calculators are worth every cent you pay for them There is a lot more to making a good pipe than punching in a few numbers into a program.

Trouble is getting enough power in the ECU to cope with the rapid change in dynamics that the pipe causes. That is expensive and cause packaging contraints. Which on a sled or a Outboard are not an issue.
  
Right now nobody wants to spend the $$$ to make the ECU.

EDIT
I haven't seen any dyno charts yet

Interestingly,I've never realized that a clutch system had any bearing whatsoever on the fuel delivery system of an engine.
A snowmobile clutch does allow the power to be delivered over a steady,narrow,optimal band but this has nothing to do with the design or engineering of the engine.Snow mo's still use expansion chambers  as well.Technically speaking,if you're not entirely spastic with a motorcycle,you can accomplish a reasonable facsimile of the sno mo set up with your throttle hand,clutch hand and left foot.A DI system doesn't only work at one exact point,it works better everywhere.The "hit" you long for isn't as a result of superior,archaic engineering but rather a result of that point where everything is working optimally.DI doesn't lose anything but it does vastly broaden this range and would therefore minimize the perception of a "hit"
As for the "ECU's have trouble coping" thing,all I can say is   
It's also not that hard or expensive to build one-and a small one at that.Many modern day cars ECU's are no bigger than a paperback but thinner.Do you suppose they have to make less calculations than a 2t single cylinder running a DI system would?
DI is the present and future,it's already proven and vastly superior-for the 100 millionth and one time.I just hope someone sticks it on a bike.

[factoryX]

 

[teriks]

TMKIWI, you can read up about the Orbital concept in the link I posted earlier: http://www.orbitalcorp.com.au/tp/pdf/2007-32-0001.pdf

2T Institute, while I agree that the two-stroke puts a tremendous load on the ECU, and with your view on cheap pipe calculators, I strongly disagree  with the statement that sleds are an on/off application. CVT and relatively constant RPM,  yes, but limited to on/off operation, no way! -Imagine running a 160hp sled in on/off operation on a tight trail... On to the outboard engine, it needs to be able to run at different loads over a wide range of rpm, although the normal operating condition would be more or less constant throttle.

SachsGS, the pipe is still needed to achieve high specific power. DI addresses only the "simple" part, getting the right amount of fuel into the combustion chamber. You still need to squeeze in as much air as possible, and that's where the pipe come into play.

The amount of computing needed increases with increasing RPM, and the available time window for fuel injection and evaporation decreases with increasing RPM. -So yes, it should be easier to implement on a large low RPM engine. The Etec 800 reach max power close to 8000rpm thoug..

[George]

This new fangled DI business seems all a bit over complicated, ive never like fuel injection and never want a vehicle with it, just give me a carb and a cable going to my right hand and ill be happy!

[VintageBlueSmoke]

This thread and threads like these are actually why I come to TSM. The exchange of ideas with like minded people.

@ George: Although I agree with you and probably everyone else here visiting TSM pretty much agrees with you, many of us also believe that if 2t engines and motorcycles in particular don't evolve and become cleaner and more efficient, they will be legislated out of existence.

@ 2TInstitute: Yes, you are correct about the $14 pipe designer software. However, I was hoping you would read into my comment though that 'if a $14 pipe program is available - and works, don't you think a well designed FI system and ECU could adjust for it and work well too?'. I really don't (and didn't at the time) mean to offend you. That is why I put the comment "...I'm sure the knowledge of an expert 2-stroke pipe builder/turner is irreplaceable,...". Pipe builders are 'GODS' had have a magic like that of a fine luthier. I have the utmost respect for them and I am confident that there will still be a place for performance improvements in the pipe of a DFI production bike. If for nothing else than the pipe will still be a major part of the system that a rider can 'tune' to his (or her) own needs on a given track or terrain type.

@ teriks: Thanks for the sled information. I have wondered about that for awhile but not bothered to look it up. I really do love this stuff!

@ TMKIWI: Yes. I said the same thing. Although I drug my feet with mechanical FI, not trusting Bosch electronics, I always knew FI was the way forward. However, even though we adapted it on the boats quickly, on our desert buggies, we still used the carbs for the longest time.

@ Ford832: As to your thoughts about the clutch, the 'hit' of a 2t is MOSTLY a product of the flywheel; less hit - heavier flywheel, and vice versa. Being that 2t engines are small, you have wasted HP in having to keep that weight spinning. To paraphrase, "in the battle for performance, he who can ride with the smallest clutch weight (most HP), wins." Compare 2 Yamaha products, the DT and YZ. They are both 125's but the YZ makes a ton more HP and even 'detuned', still has a significant hit. Yes a lot of that has to do with things like porting, exhaust, piston and head shape but the DT was designed for the street and has a huge flywheel and rides almost 'electric' like. I don't have the experience with the sleds but I believe your experience is 100% valid, and that was the main point of my original post. FI (of some kind) is the way of the future, we should be embracing it and encouraging manufacturers to supply it.

I am of the belief, and correct me if I am wrong, that the problems with FI are 3 fold; The ECU, Cost, and Perception.
-First, that the ECU is fragile and susceptible to exposure to heat, dust, water, and vibration. Packaging one to survive on an off-road motorcycle and making it small enough might be an issue. Powering it (without adding the weight of a battery and charging system) might also be an issue. Of course if the trend set by Husaberg and KTM continues of putting electric starters on 2t's, problem solved!
-Second, will the product and development costs be recouped by a company who produces it or will it price itself out of reach of the consumer?
-And third, will the consumers embrace the new technology and buy it or will they clamp down to the old ways like I did with drum brakes. (Yes, I was one of those who didn't trust the fragile disks and was reluctant to accept change). That might not be an issue if carb'd 2t's are legislated away.

[2T Institute]

In theory,and I'm thinking aloud here,if the ECU could keep up with the increasing RPM of a 2T and ALWAYS inject fuel into the combustion chamber after the exhaust port closed at the correct time before TDC ,an expansion chamber would not be needed?The reality is that due to time constraints the injection timing has to be advanced relative to increasing RPM to the point where the exhaust port is open at a certain engine speed.Hence, an expansion chamber is still needed and the ECU,given the present level of technology,has great difficulty making this transition.With this in mind,wouldn't it be easier to adapt DI to a relatively low RPM 500cc motocrosser then a screaming 125?    

That is correct there is a retro fit kit for 125 commuter bikes(for use in developing countries) that have an injector plumbed into the head, I know think is out there somewhere, the carb was removed and the reeds just sucked air, but yes the engine was not dependant on the chamber. 

A CVT is a constant velocity transmission  not the clutch, the CVT (as with the DI Aprilia 50 scooter) has no gearbox ratio, but infinitely variable, so the engine is tuned to a very narrow band, with out 'gaps' between the gears they don't fall out of band. So you just hold a relatively constant throttle when moving  and the CVT does the work. A bit different story to going round a snotty , rutted off camber corner or up that snotty hill, where the rider will be just 'surfing' the point of the engine going into band, feeling the optimum point to open the throttle.(That's what MotoGP riders do with traction control)

Well if ECU's don't have trouble making all the calculations , you should have no trouble making one work on a 2T then should you?

Time is the killer or lack there of, so we go to simple maths, most sleds have the ex port open at 80deg ATDC,  piston rises and falls and rises to TDC 133 times a second, or 0.0075 seconds to go from TDC to TDC, the time from ex port close to ex port open is 0.00375seconds(that's for 90 deg to make my calculations easier), assuming that ignition is at 14 deg BTDC, which is 0.00058 seconds BTDC we have to inject before then, that leaves a period of 0.00317 seconds to get all the calculatons right for that cycle. I know, I know that the piston is decelerating as it approaches TDC  but for illustration purposes you get the idea, which again is fine on pipe but off pipe the ECU cannot distinguish the fueling needs because of the unreliable inputs from the pipe. A carb does this with ease as it is an intellignet device, the ECU has to be told what to do. What normaly happens is the ECU get tricked into thinking the engine is lean (off pipe).

I install programmable ignitions every week and there are robust as, there is no 'brick wall in the head' about the use of technology, BUT you have to accept that when groups of talented engineers like HRC and at Cagiva attempt EFI engines and GP riders call them 'unridable pieces of shit' (sic Carl Fogarty) they probably are. If the nut was easy to crack it would have been cracked many moons ago.

Don't forget it took a few attempts to get discs (on road bikes) anywhere near the performance of good 4LS drum brakes, by the time discs appeared on dirt bikes they were pretty sorted(first few aside)

[teriks]

That is correct there is a retro fit kit for 125 commuter bikes(for use in developing countries) that have an injector plumbed into the head, I know think is out there somewhere, the carb was removed and the reeds just sucked air, but yes the engine was not dependant on the chamber. 

Envirofit
http://www.youtube.com/watch?v=EjBcxyKkpEE

[SachsGS]

I forget,so the expansion chamber in a 2T functions as well like a megaphone exhaust on a 4T in that it helps "draw" the spent fuel/air charge out of the combustion chamber (in addition to providing a return resonant wave to block the exhaust port)?

Would it also be true to say that most of the pollution in a 2T occurs in an "Off the pipe" situation and that small utilitarian 2T applications that typically don't have tuned exhaust (ex.:weedwackers and chainsaws) would be the worst offenders?It would seem to me that small,all position and essentially single speed applications,like a weedwacker once again,would seem to benefit the most from DI.

[Super Trucker]

I don,t like the DI  system, a pal of mine worked with the KTM mx team, if you change the pipe you have to reprogram the computer, and that,s a on a 4-st. I  had  numerous break downs in the last 2 weeks, the 20 inch deep potholes and rough roads, tear a truck up. Some of the stuff is computer related and sensors, wireing to sensers breaking, I bypassed a couple sensers just to get the truck to move out of a dangerous break down spot. IMO sensers do not belong on a mx bike. A mx bike doesn,t get half the beating a truck gets, but still, Honda doesn,t need DI to sell the bike. Who has over 200.00 in gas to go riding anyway.

[teriks]

I forget,so the expansion chamber in a 2T functions as well like a megaphone exhaust on a 4T in that it helps "draw" the spent fuel/air charge out of the combustion chamber (in addition to providing a return resonant wave to block the exhaust port)?

Yes, if we keep it simple.

Would it also be true to say that most of the pollution in a 2T occurs in an "Off the pipe" situation and that small utilitarian 2T applications that typically don't have tuned exhaust (ex.:weedwackers and chainsaws) would be the worst offenders?It would seem to me that small,all position and essentially single speed applications,like a weedwacker once again,would seem to benefit the most from DI.

Not necessarily so, but the real killer for HC pollution is four stroking operation, -IE misfiring every other stroke.

[ford832]

2T institute.CVT's on snowmobiles are commonly called the primary and secondary clutch and are both the clutch and transmission but if nit picking the terminology trips your trigger,that's cool.
A DI set up is hardly a standard engine with an injector plumbed in to it.If time available to inject the fuel is your issue you need to realize the BRP DI injector operates at 500psi.Even a car at a 600 RPM idle with an old style low pressure injector has an  pulse width of about 2.5 milliseconds.
As we all know,on a standard 2t,after the fuel has traveled the transfers and the backpressure wave has forced some of the unburnt fuel back into the cylinder and the piston has closed the exhaust port,the charge still has to be compressed before the plug fires.This takes time,and time enough for an injector to fire.The backpressure wave is virtually irrelevant in a DI system as pertaining to lost fuel charge because there is none so the exhaust port window can be altered to allow more time if that was ever an issue.
It's not a matter of how someone could solve all your perceived issues,BRP has already done it on a 9000 RPM snowmobile engine.How much power is your bike still making at this point?The injector has time to fire,the ECU makes the calculations even with the "unreliable inputs from the pipe"(whatever that means).
I like Foggy's quote though.When was that?10 yrs ago?15?Things have come a long way in the last few years.
The "nut" was mostly cracked with BRP's SDI system and is fully now.Naturally,you're right,I couldn't build one.I'm just a dumb mechanic,not an computer programmer or a mechanical engineer.I'm also not vain enough to assume that just because I'm too dumb to do something that no one else could do it either.Not everyone shares this perspective however.
I've never heard a carb called an intelligent device before.I was unfortunate enough to have to work through the carb era in auto and EFI systems have been a godsend.Carbs worked fine when that was all that was available but they were outdated many years ago-in every possible way.Maybe some carbs I've yet to see are "intelligent" enough to compensate for temperature,pressure,crank pos,intake temp,exhaust etc,etc,etc like all EFI systems.I guess I just missed that one.
On the other hand,if you want to really know how crappy the new sno mo/outboard systems are,ask TMKIWI.If I remember correctly,he works on them.

[ford832]

VintageBluSmoke.The "hit" isn't a product of flywheel weight but rather engine design.Granted,the exact same engine with a heavier flywheel will have less hit than the same with a lighter flywheel but this is due to the fact that the heavier flywheeled engine has more rotational mass hanging off the end of the crank and therefore more "load" on the engine.It takes more to get this spinning which softens the perception of the hit.Interestingly,a bike with a strong bottom,mid and top has less hit that a bike with a poor bottom and strong mid.
This often makes slower bike seem faster due to the fact it takes off when it actually gets in to the power.

[TMKIWI]

I like this thread.
I under stand what you are saying 2T about injection time. It has aways been the issue. The problem with your comments about Foggy is that was a long time ago.
When Honda and co were working on injection systems the problem was aways EMM speed or lack there of.
Also in the late 90's as you know 500GP's were going to be replaced with 4 strokes so there was not much point in continuing with developement. And as you have said trying to make it work on a 13000rpm GP bike was never going to be easy back then.
The same issues were found on the early Fichts which had no end of problems mostly caused by EMM/ECU's.The early Optimax/Orbital Mercury's had issues with pistons melting   and other issues. These have all been overcome.
I have been in the outboard industry 10 years and the early days were nightmares with all sorts of weird and wonderfull breakdowns. (Thats why I am half bald)
BUT all the problems were solved and the main reason is better electronics.
Back to injection time: You dont actually need to inject the fuel AFTER the exhaust port has closed. If the porting and combustion chamber design is correct the incomming air "swirl" will scavange the motor as it does now AND keep the fuel away from the exhaust port when it is still open. Combined with the exhaust return pressure wave the fuel can be injected before the exhaust port closes and no fuel will escape. This is what BRP have done.
Here are my thought on making it work on a dirt bike. The engine needs to be 300 to 500cc so you have a 8000rpm ceiling.
To help with the exhaust pulse issue remove the power valve from the engine. In it's place put a exhaust valve/flap in the pipe which will vary the exhaust pulse lenght further away from the comustion chamber and leave a nice large port. Operated by a simple servo motor.
Some model ETEC's have this and when driving you can feel a "Hit" as the valve opens.This should give you an engine with mountains of torque over a broad range.
It might not be a 70Hp CR500 killer but will still produce more power and torque then a 4 stroke. Baby steps are needed.
Not saying it will be easy but I certainally don 't think it is impossable.
Thats my thought on the matter.Lets keep it going