Rumours,Rumours!

[SachsGS]

Ford,I wouldn't worry about being a "Dumb mechanic",most mechanical engineers are very good mathematically but lack mechanical intuition,the odd guy who has both skill sets is the one most companies are after.At one high tech company I worked for a "Greasy wrench" out of a garage in northern Alberta really did change the course of an industry.His ability to approach a problem from a new and unique perspective allowed the company to leapfrog ahead of the competition.

Werner Von Braun,the guy who put the Americans on the moon,not only had a doctorate in Physics but could also,with his hands,build the rockets.

I like the direction of this thread as well.History often repeats itself and I wouldn't be surprised if a bunch of Honda engineers are secretly tackling the problems of 2T DI.

[VintageBlueSmoke]

@Ford832, I think I said the same thing  (re: "Yes a lot of that has to do with things like porting, exhaust, piston and head shape"). But my point was (and maybe my meanderings lead us astray) that the hit is designed into the bike for whatever the use. Since a 2t is so finicky (pipe, timing, flywheel, port shape, weather, terrain etc), a street engine would be designed for very little hit and a wide range of power whereas an  MX engine would be produced to provide peak power in a very limited range and those riders that could harness when it was on the pipe were heroes (i.e. Hannah, Jonny O, even Bubba!). Another example was the old Can-Am range. The '75 Can-Am TNT made more power than most any other 250. It was like riding an Open class bike as it had gobs of power all through the range. The MX version however was an Expert Only bike. It made a bit more power but it hit so hard that you had to have a name like Jones, Tripes or Ellis to use it. Ok, that's a bit of an exaggeration but it wasn't your 'average riders' bike. Of course, that had to do with the rotary disc intake as the engines are the same but it serves my analogy.

As for the whole injection timing issue, and I must preface this as I am not a mechanical or electrical engineer, I don't think that is the issue. Maybe 15 years ago, but not today. Nor is processing power in the ECU (although electrical power may be an issue in packaging). F1 engines turn at 19,000 RPM and that is limited by a common ECU (they used to turn more but were limited for longevity by the rules in the cost cutting initiative). Yes, they are multi-cylinder 4$ engines but the principal is the same: Inject x amount of fuel at y time (with y being a product of rpm and other inputs).

[TotalNZ]

The way i understand it, is the difficulty in getting the necessary information to the computer, how do you monitor the fuel air mixture and prevent a lean situation. I'm thinking the usual sensors wouldn't cut it ie lambda probe or air flow meter. I'm thinking it would be very hard to manage, especially with the more variable throttle input and direct drive nature of dirtbikes.

[teriks]

The way i understand it, is the difficulty in getting the necessary information to the computer, how do you monitor the fuel air mixture and prevent a lean situation. I'm thinking the usual sensors wouldn't cut it ie lambda probe or air flow meter. I'm thinking it would be very hard to manage, especially with the more variable throttle input and direct drive nature of dirtbikes.

Food for thought: What information does the carb have access to?

[George]

The way i understand it, is the difficulty in getting the necessary information to the computer, how do you monitor the fuel air mixture and prevent a lean situation. I'm thinking the usual sensors wouldn't cut it ie lambda probe or air flow meter. I'm thinking it would be very hard to manage, especially with the more variable throttle input and direct drive nature of dirtbikes.

Food for thought: What information does the carb have access to?

A carb doesnt need information as they are designed and set up to work alongside engines, the engine sucks and the carb gives as much fuel and air as your right wrist is telling it to, but with injection, the engine sucks and the injector tries to know how much fuel and air to squirt at the engine given throttle postition and engine speed etc, so the carb needs no information other than the cable pulling the slide up where as the injector needs to know alot, but you do have a good point.

edited to correct grammer

[Bioflex]

Without trying to be pedantic, it's probably correct to say that a well sized, jetted and working carb knows how much fuel to give the engine due to the engines needs and the control of the right hand.
When sized and jetted properly, a carb will provide the correct amount of fuel, however the modern carb with its different jets, matched venturi and everything else is the result of many decades of refinement.

The limitations of fuel injection are ONLY due to current technology and while I am sure the technology is there at the moment, whether it is cost effective to apply it to 2 strike motorbikes (which really aren't going to pay off as a great investment) is another question,

We shouldn't forget that the first carburettors would have been nothing more than a manifold with a hole where fuel dribbled in.

The discussion here should be more about whether there is enough money and desire left in two strokes for anyone to bother financing such an endeavour (as there are obviously some real issues that need to be worked out) I really hope there is, as if not, we will likeley never get to see anywhere the potential that we could have of 2 strokes.

[2T Institute]

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.

A 4T engine has 360deg of extra crank rotation, which based on the previous cycles O2 reading 'guess' what the fueling requirement for the next time the valve opens does it not? A 2T engine has at least 2 phases of a cycle happening at any one time 4T's DO NOT. That makes applying electronics very easy.Pipe dynamics are not constant and change with pipe temp, rpm, throttle opening and ignition, that makes reading from pipes unreliable, unless you constantly operate the engine in phase or have a constant pipe temp like an outboard.

A carb is VERY intelligent device as on it's own it can meter fuel over a very wide range of conditions and if you like Lectrons can automaticaly compensate for altitude.Fixed gear kart engines with very simple Tillitson/Walbro carbs with a just a high/low speed tapered needle arrangement can meter fuel effectively from 0-22000 rpm, model plane engines, up to 36,000 rpm.Carbs don't need to compensate for anything other than changes in relative air density, the ignition on a 2T takes care of everything else.

If the ETEC is so good get one saw a cylinder off and stick it in a bike frame can't be to hard can it? In fact I would love to see someone hook up a mega/Microsquirt on a dirt bike,to prove me wrong, but alas nobody seems keen to take up the challenge.

Here is a few uote from a ex-GP engineer (a few people might recognise where it's from)

Fuel pressure is about 3 to 5 bar for indirect injection and about 20 times more for direct injection.
Injectors in the transfer ports do cool the charge - but not very effectively, because there is very little time available for mixing and evaporation of the fuel. If you want to cool the charge, injection in the intake duct is much more effective because the fuel is much longer on its way to the combustion chamber, and meanwhile the charge is intensely stirred by the crankshaft, especially by the conrod. And the big-end bearing needs that fuel.

This is one of the two big problems with direct fuel injection in a racing two-stroke: an Aprilia RSA125 at full throttle on the test bench consumes 1 drop of oil every 30 crankshaft revolutions. That may be enough for lubrication but it certainly is not enough to cool the bearing. Without fuel passing through the crankcase the engine will not live very long... 

The second big problem is creating a homogeneous air/fuel-mixture. With direct injection, even when you start injecting at BDC, there is only one half crankshaft revolution available for mixing and evaporation. In the RSA at 13000 rpm that would be 0,002 sec...

With indirect injection or carburation the situation is much, much better. Let us follow a droplet of fuel on its journey through the engine. The journey begins when the droplet exits the carburettor or injector. Four or five crankshaft revolutions later that same droplet appears in the combustion chamber (this is a mean value; some droplets travel quicker, some are slower).
And before you ask: "How do you trace a single droplet?" You label it - with radioactivity. Do not try this at home...

The last experiments with injection on anAprilia two-stroke racer were with the RS500 twin, ridden by Jeremy McWilliams. It had two injectors per cylinder: one in the intake tract and one in the crankcase. Throttle response was ....ehh .... sudden! Fortunately Jeremy was a very brave rider.

[factoryX]

http://bansheehq.com/forums/index.php?showtopic=139722&st=0

[TMKIWI]

I am not sure why you keep quoteing about problems from the late 90's 2T as the same issues were present with outboards.
As you have said it is easier with a constant temp exhaust, if the Outboard engineers had problems with an "easier" type engine it is no suprise that GP engines had trouble making it work as well. "With a far more complicated engine."
I have had to work through the issues with the first DI Ficht's from 98' and they were untuneable pieces of shit.
Rough running,failed injectors,fried EMM's,sensors not working etc. There was nothing you could do to fix them properly.
Optimax had melted pistons from too high combustion temps, oiling problems etc.
Fast forward 10 years and we have.................................Engines that work very well.
The next step was getting it to work on sleds that from memory do not have constant temp exhaust's.
You obviously have a wealth of experience in GP's ? but as Sachs mentioned in an earlier post it is amazing what can be acomplished when you put together people from different discipline's. Thinking outside the square.
I agree with Bioflex that the biggest stumbling block is engineers/manufactors making the financial investment to actually build a DI bike.
No one will spend money on something that will not sell.
It will not happen in MX because of the rules. But offroad ?.
Maybe.

[ford832]

I think you're beating a dead horse 2t institute.It reminds me of arguing all the reasons why an airplane will never fly.
BRP has already done it-the end.As bioflex says,it remains to be seen whether anyone will put it into production.Maybe BRP will do a dirt bike,under the Can Am name.That's certainly feasible if they see a market.
For all you who don't want to see it happen,you better hope it-or something else,does or I expect in a few short years you can kiss your 2t dirt bikes goodbye.

[ford832]

Ford,I wouldn't worry about being a "Dumb mechanic",most mechanical engineers are very good mathematically but lack mechanical intuition,the odd guy who has both skill sets is the one most companies are after.At one high tech company I worked for a "Greasy wrench" out of a garage in northern Alberta really did change the course of an industry.His ability to approach a problem from a new and unique perspective allowed the company to leapfrog ahead of the competition.

Werner Von Braun,the guy who put the Americans on the moon,not only had a doctorate in Physics but could also,with his hands,build the rockets.

I like the direction of this thread as well.History often repeats itself and I wouldn't be surprised if a bunch of Honda engineers are secretly tackling the problems of 2T DI.

Thanks Sachs but one of my redeeming qualities is that I understand my limitations.On the off chance I forget them,the wife never fails to remind me     

[factoryX]

Exactly, look at how far 4 stroke engines have gone in the last 30 years, and then look at the 2 stroke engine .  They've updated these formula one tech 4 stroke motors every year since they've come out, and now they're producing more power than ever. Its either get EFI/DI 2 strokes going, or slowly watch two strokes die out which is currently happening. This is why KTM, TM, and I guess "Honda" have all hinted at EFI/DI two strokes. Its had great success in the sled world and its currently working its way into GP racing, so whats the hold up?

[TMKIWI]

Here it is, The new Honda.

EFI 2 Stroke.

[VintageBlueSmoke]

You are evil. 

[miedosoracing]

Here it is, The new Honda.

EFI 2 Stroke.

What kind of bike is that? There are two different ones, because the one with red anodizing triples etc isn't too bad. I'd buy a bike like that to commute.     Italian?  Colors on number plates is why I ask.