ESE's works engine tuner

[TZ350]

Problem fixed.

So it is, many thanks. TeeZee

[teriks]

Frits is it possible to have to short of a inlet tract for a disc valve engine ?
If so would you explain the issues, complications & tell tail signs please.

Not Frits, not a disc (but still a rotary valve) and on a different scale from your normal bike engine but anyway:

Black line: Inlet tract as short as physically possible, timings optimized for this.
Red line: Longer inlet tract, same timings as above, inlet bell identical to above.



Now, this is with a rotary drum valve with potential for huge STA with moderate timing on an engine without throttle ans stuff that adds to the practical minimum length, but still, it seems possible to have a too short inlet tract.

EDIT: A bit surprising was that further tries to optimize the timings for the new (longer) inlet tract didn't result in any improvements at all.

[Frits Overmars]

Frits is it possible to have to short of a inlet tract for a disc valve engine ?
If so would you explain the issues, complications & tell tail signs please.

You'll need a bellmouth for any inlet system, so the air that is flowing in from the sides, is gently guided into the desired flow direction instead of crossing up the flow and causing a restriction. Compare it to a crowd of people trying to leave a hall. The people coming from the sides disturb the progress of the people that are moving towards the exit in a straigth line. It's the same with molecules.
So the bellmouth is necessary and it has to have some length in orfer to accommodate a decent radius. Apart from that, the shorter the inlet tract, the less inertia of the mixture in the tract, the better it will accelerate and the quicker it will fill the crankcase.
If the revs are too low, or the inlet timing too long, or the inlet diameter too big, or the tract too short, you will have backflow before the inlet closes.
But don't blame the short tract; blame the inlet timing, or blame the rider who fails to rev the engine.

[teriks]

So the bellmouth is necessary and it has to have some length in orfer to accommodate a decent radius. Apart from that, the shorter the inlet tract, the less inertia of the mixture in the tract, the better it will accelerate and the quicker it will fill the crankcase.

Thats my understanding as well, and the reason I put quite some effort into designing the inlet tract as short as possible on my (not yet finished) rear intake version of the MB LS.

It seems that EngMod dont agree that a shorter tract is better in every case though.
After finding the minimum length as per above, I did a shit load of simulations of different opening and closing timings before deciding on what seemed optimal.
After that I tried lengthening the tract, and ended up with the "more power everywhere" curve above. -I could not get anything near that with the short tract, no matter what timings I tested.
The bellmouth below was used as is on both the long and short version, only the length of cone after the short cylindrical section was changed.

Granted it might be a fluke in the simulation, but Ill try both versions eventually.

[wobbly]

Well I am back - sorry to say.
I was originally trying to make some snide comments about the Suter effort being a bloody expensive joke.
Why anyone would go to the IOM with an engine that obviously hasnt been dynoed to death, and for the engineer (s) to think that they
are suddenly the only ones in the world who are capable of making throttle body injection work on a racing two stroke at part throttle ( as NO ONE has been able to
make that work properly yet ) gives us an insight as to why Kalex have blown the Suter completely off the GP2 track.

They have the most expensive, and superbly built pipes ( done by Akrapovic ) who have never made 2T pipes before ( so you have to ask who designed them )
and the only comment we hear is that " its got a fueling issue " well no shit, they should have paid TeeZee to have a go at the computer as he would have more idea
about the problems than anyone at Suter.

And the last straw was we are told it fouled a plug in the race - when was the last time that happened in any form of 2T racing since 1960 something.
I suppose they were running those real expensive BR9ES lawnmower things.
Yes I am pissed off with them, and no I dont think I could have done any better, as I for sure wouldn't have even tried that dumb a stunt in public.

PS - Teriks, have you tried modelling the bell as 3 sections to increase the accuracy over a simple straight line ?

[F5 Dave]

Soooooo. . . What was the guts of Itoh's NSR500 that was reputedly tested with injection in the late 90s? Obviously it didn't work better than carbs so not progressed but not much info besides journalists guesses. Think I read it wasn't injected after all years later but it clocked the highest speed at the time. Do we know any more?

[1948rod]

hi wobbly if you have the time could you point out the developement areas that have evolved over the last few years in kz kart engines. you have been jonny on the spot to be well informed to show the masses what direction they have changed. these engines even with their constraints are still going ahead. thanks for sharing the knowledge.

[husaberg]

Soooooo. . . What was the guts of Itoh's NSR500 that was reputedly tested with injection in the late 90s? Obviously it didn't work better than carbs so not progressed but not much info besides journalists guesses. Think I read it wasn't injected after all years later but it clocked the highest speed at the time. Do we know any more?

Itoh did a full year on the injected bike in about 95 but his best result that year was using Doohans bike in one race when Doohan was injured or something
The injected bike did have the fastest speedtrap that year, but itoh could tuck in better than Mick anyway.
Mick tested it but refused to race it.... as he wanted to win the championship.
I will post the guff I have.
it was throttle body injection as far as I know.
As you see Honda was doing it for fuel consumption.
they had also trialled it earlier in both 250 and 500 form

[husaberg]

the rest..........
The fuel injection and carburated version of both the big bang and another version (that was never used) occurred in winter testing in Aussie 1992.
According to Yoichi Oguma they asked the riders to decide and they said there was at the time no point in changing over to fuel injection "as it gave no real advantage"
All the reports I have read had Itoh using the Fuel injected bike for most of 1993 season.
Cagiva according Goggi to them started testing fuel injection in 1988.

[wobbly]

Itohs injected Honda held the fastest speed trap number for quite a long time, but I have it from several people that this bike
was only used in practice - it was never actually raced.
Doohans reaction was reminiscent of Foggys about the injected Cagiva " its a piece of shit and I wouldnt ride it no matter how much you pay me ".
I have read the SAE papers on the system, and the Honda ECU ran on a bunch of lookup tables in closed loop that were sequenced to diagnose and then rectify any misfire.
Honda felt that the sensors of the time were not reliable enough to run in open loop, continuously changing a single base map for fueling and or ignition.

I will reply about KZ2 tomorrow.

[teriks]

PS - Teriks, have you tried modelling the bell as 3 sections to increase the accuracy over a simple straight line ?

Almost, in my current model the bell is divided in five sections + end correction.
Not very good for run-time, but the results differ slightly from the single straight line.

[Flettner]

This fuel injection debate/talk interests me, am I so wrong? Can you see why throttle body injection in a twostroke is doing things the hard way? It's all about homogeneous charge, can you see that at lower RPM's (using PULSED injection) there is just a small 'pocket' of fuel dispenced into the incoming air. The crank case is not 100% pump so not all of this fuel pocket will neccessarily go up into the cylinder each cycle. So you get inconsistent fueling up into the cylinder (at part throttles) = bad/gutless engine response, sharp power band as this problem starts to come right as the injection time gets longer. Having a small injector then onto a large injector is a patch up and has it's own problems. I can only say (again) that transfer port injection is a much better solution, with (timed right) ALL the fuel injected each cycle being transfered to the cylinder.
When I do my next injection system I'll be injecting across the inlets of the transfers in the crank case, from front to back. Not interested in fuel consumption just homogeneous charge (or best I can get), with timing being critical. This will be nessasary as there will be no throttle body at all, throttling will be done at the transfers.
I ride my shitty old Kawasaki around every evening just before dark, just to scare myself, perhaps I better tell it not to run so well, not being throttle body injected and all.

[wobbly]

KZ2 engines as far as factory development is concerned over the last few years is confined to a few detail areas.
The main one has been to tilt the cylinder back and at the same time straighten out the inlet tract, ending up with no
bend at all at the manifold and thus the carb pointing seriously downward.
This allows the reed block to point upward under the piston, and the straight manifold rubber has, at the same time been shortened as much as is physically possible.
Now the thin rubber flange sits hard against the reed block face, with just enough room to get a thin hose clamp onto the carb spigot.
This straight shot has made redundant all the years of hard work put into staggering the reed thickness, and backup tension, to try and redistribute the
flow more evenly thru all the petals.
Thus the reeds are now the same top and bottom in all the fastest engines I have dynoed.
As the inlet is straight, the flow is even in all directions, and power has increased by around 1.5 to 2 Hp from just this and the shortened tract length.
Most engines have also been progressively reduced in the Exh duct exit area, and some now have proper oval to round transitions in the slip joint
manifold with no steps at the face.

High inertia cranks are now the norm, but were "specials " a few years ago.
Pipe development has stalled for some time, as all are out at around 130 diameter, and the last TM homologation just made the TL around 6mm shorter
but very little variation in tapers.
Ports have also been pretty much locked in for years, all with normal stagger, just varying amounts of it.
I have concentrated on small areas of development, working on the cooling of the head and the Ex duct, along with the allowed fiddling with stingers/mufflers.
and the Ex spigot ( you can shorten the pipe legally on older engines simply by machining off the spigot mounting faces ).

There is still a huge amount of detail design work that hasnt even filtered down from the end of 2T GP racing years ago, and from the results of a large amount of
( currently illegal ) dyno work I have done, I have scored the best 2T tuning job in the world.
As after the World Finals in Vegas I am off to Pesaro to work at the TM factory with Franco Drudi on the next homologation design.

So ask me the same question next year.

[2T Institute]

This fuel injection debate/talk interests me, am I so wrong? Can you see why throttle body injection in a twostroke is doing things the hard way? It's all about homogeneous charge, can you see that at lower RPM's (using PULSED injection) there is just a small 'pocket' of fuel dispenced into the incoming air. The crank case is not 100% pump so not all of this fuel pocket will neccessarily go up into the cylinder each cycle. So you get inconsistent fueling up into the cylinder (at part throttles) = bad/gutless engine response, sharp power band as this problem starts to come right as the injection time gets longer. Having a small injector then onto a large injector is a patch up and has it's own problems. I can only say (again) that transfer port injection is a much better solution, with (timed right) ALL the fuel injected each cycle being transfered to the cylinder.
When I do my next injection system I'll be injecting across the inlets of the transfers in the crank case, from front to back. Not interested in fuel consumption just homogeneous charge (or best I can get), with timing being critical. This will be nessasary as there will be no throttle body at all, throttling will be done at the transfers.
I ride my shitty old Kawasaki around every evening just before dark, just to scare myself, perhaps I better tell it not to run so well, not being throttle body injected and all.

But when the best riders in the world jump on a bike and say "fueling is shit" then what is the engineer to do? Top flight professional riders have specific demands and not giving them what they ask for means the serious money factories pay them amounts to nought. An old Big Horn can only be ridden so fast by a bloke in shorts

[Flettner]

But when the best riders in the world jump on a bike and say "fueling is shit" then what is the engineer to do? Top flight professional riders have specific demands and not giving them what they ask for means the serious money factories pay them amounts to nought. An old Big Horn can only be ridden so fast by a bloke in shorts

No, even the shorts guy is too scared to hold it at full throttle. Probably more to do with the handling than anything else
I must say though, those shocks you recommended work real well (as best they can under the circumstances).