ESE's works engine tuner

[wobbly]

Try putting the venturi directly behind the slide like Lectron did - this will shorten up the divergent length with much slower angles out to the RV port area.
Easy to test the flow capability of the varying venturi positions and divergent angles on a flow bench before hitting a dyno.

[husaberg]

No doubt someone will "pipe up" with a couple of cliche's about the bike.
but Kevin Cameron says what i would describe as some interesting things in this article regarding the development path of this and other TZ Yamaha's.

Could someone more learned than myself ever confirm or more likely deny a few bits in here as it seems to go against some prevailing wisdom in regards to a few technical pieces.

I could be bothered highlight the relevant piece's as the highlighter always moves.

What kevin Cameron mention's he has also mentioned Mculloch engines doing it as well in regards to the Reeds.
I personally found the bits about the squish clearance and band width a bit confusing. But i might be more thick than i originally thought.

The reasoning for the flat slides was interesting as I had not seen it described like that before.

Also forgot incredibly ugly intakes what "up" with that.

[wobbly]

Nothing too much off the mark - except the old bullshit tale about the pipe pulling the reeds open.
How it goes is that the diffuser sucks like hell on the cylinder around BDC - this pulls gas out the transfers, they pull on the case, and this opens the reeds, allowing more mixture in.
Crap.
Here is a sim trace of a RGV100 at 13,000 making 40 odd crank Hp.
BDC is exactly between TPO and TPC, the reed lift down the bottom isnt showing the reeds much open till TPC - well after BDC, so the pipe action isnt affecting the reed lift at all, apart from
a delayed reaction due to petal stiffness and column inertia in the intake.

Re smaller case volume, I have measured one of those engines and its case com is exactly 1.3 on one side and 1.29 on the other with around 540cc from memory..
This is alot smaller than an Aprilia at 640cc.
But its case vol is relatively large in comparison to 2T technology at the time.
In a 125 project I have just finished, with a case reed, 1.3 gave the best result.
Going down to around 1.24 of the RSA spec lost around 2Hp with the reeds, no matter what I did with intake length and petal stiffness, pipe geometry or carb size.

Re the squish shape and chamber geometry.Yamaha always had odd ideas about what was correct, or best, and never really led the way at all until unleaded became mandatory.
Then the YZR was fast once Kennys boys got them on Asklands dyno.
And they kicked everyone's arses , even in 250 when they fitted the spool valved cylinders off the 500

[husaberg]

Re the squish shape and chamber geometry.Yamaha always had odd ideas about what was correct, or best, and never really led the way at all until unleaded became mandatory.
Then the YZR was fast once Kennys boys got them on Asklands dyno.
And they kicked everyone's arses , even in 250 when they fitted the spool valved cylinders off the 500

I guess you are meaning except for the 500 class cause the fuel came in mandatory in 98 i believe and Yams results aren't so special after that.
from what i understand the lower lead fuels introduced in 94 ish benefited Honda.

Just checked the 250cc and the 125cc results as well. There's bugger al Yamaha 2 stroke world champions after 1998 (IE one on a twostroke by the look of it). Why were they kickings arses softly?

[wobbly]

Yamahas basic technology took big strides forward after 98, the 500s were very fast but Doohan was faster.
Prior to that the engine tech was crap and Askland changed everything in sight to make Wayne a bike fast enough to win.
With the factory finally getting off the high horse and admitting Honda was right all along with 54 square, and then they added back the superior spool valve
that worked so well in the old RZ - then riders like Laconi, Abe , McCoy,Checa and Biaggi won races without having teams that changed everything inside to make them go.
Even Crafar had a chance to take the title in 1998, with fastest laps, fastest top speeds etc, Doohan was a genius of the first order but Simon had a bike that was capable of winning every time out.
All this was put together in 2000 for the 250 that was utter shit prior, in relation to the Aprilia or Honda.
Nakano and Jacque fought it out down to the last lap at PI.
Then they stopped development again,odd buggers to say the least.

[husaberg]

and then they added back the superior spool valve
that worked so well in the old RZ -
Then they stopped development again,odd buggers to say the least.

That's something i haven't seen on this thread yet. That is a comparison of the different power valves with the pro's and cons of each style.

Honda RC "Revolution Control" Valve


Good points

Simple, Easy to modify, Rugged, unlikely to snap and be swallowed by the engine, Easy to modify for a smaller bore engine. Electrically controlled servo motor so potentially reprogrammable in operation. Able to be shaped to the contour of the bore.

Bad Points
Has to be adjusted.
Has the potential to gum up.
Because it travels in an arc it may have a limited range of effective operation.

[2T Institute]

All this was put together in 2000 for the 250 that was utter shit prior, in relation to the Aprilia or Honda.
Nakano and Jacque fought it out down to the last lap at PI.
Then they stopped development again,odd buggers to say the least.

Time for my big note myself me at the GP spiel..........

I asked Herve Poncheral(see name dropping already) about the 2000 season with the 250's, he said in the years prior they did everything themselves and 1999 the factory started to do everything for them. Herve also said that Nakano took the defeat 'like a gentleman' and if Jacque had been on the receiving end there would have been "big fireworks" in the pit box afterwards.

[Frits Overmars]

... say two bucket racers, a low power/high torque bucket will only beat out high power/low torque bucket if the race is short (initial acceleration is higher for high torque) ...

I missed that original quote by Fooman (maybe it was in a different topic?), otherwise I would have wrung his neck corrected him.
Torque is something you distill from power with the help of a gearbox. You can have bulldozer torque, but if you have no revs, you cannot use a transmission ratio that multiplies this torque before it is put on the tarmac. On the other hand, if you have featherweight torque and a lot of revs, you can use a total transmission ratio that mutiplies that feeble torque tenfold before it gets to the rear tire.

Thats one very homely looking Brolly Dolly behind Av

You guys' creativity with the language of Shakespeare never ceases to amaze me.

Try putting the venturi directly behind the slide like Lectron did - this will shorten up the divergent length with much slower angles out to the RV port area. Easy to test the flow capability of the varying venturi positions and divergent angles on a flow bench before hitting a dyno.

I agree re the place of the venturi. But that flow bench test would give you zero information about the intertia of the inlet gas column, Wob. A normal flow bench operates with steady flow, but steady flow is something you will not find anywhere in an engine.

Re the articles by Kevin Cameron which, by and large, are excellent reading:
Cameron mentions large area reeds needing low stiffness which allows them to open almost as soon as the piston rises. But the opening of the reeds has nothing to do with piston motion; the reeds are opened by a pressure differential and that can occur even while the piston is on its way down (imagine pipe suction at really low revs).

Guillotine exhaust power valves in the Yamaha 250 cc V-twin caused a peculiar problem: oil collected in the sheath for the valve of the down-sloping cylinder, acting as a hydraulic block on the valve. We drilled a small leak hole to get rid of the problem.

In a piston-portdesign.. it is desirable to make the crankcase big so that the exhaust pipe's suction phase has plenty to draw upon for effective cylinder scavenging

True, true.

In a large-area reed design however the reed can reopen shortly after BDC....and can then supply as much extra mixture as the exhaust pipe is capable of hauling up through the cylinder. Such an engine no longer needs a large crankcase.

Wrong, wrong. The 'plug' of mixture in the intake duct strongly resists being accelerated towards the crankcase; the crankcase pressure has dropped quite a bit (slowing down the transfer flow in the process) before the intake flow starts attributing something useful to the crankcase contents. And the same goes for rotary inlet engines; they too need large crankcase volumes to make real power.
Wob, the pipe does suck like hell on the cylinder and hence on the crankcase. It just doesn't show at the reeds until a lot later because of, like you say, petal stiffness and column inertia.
By the way; the Aprilia RSW's crankcase volume at TDC (that means including the transfer ducts) is about 650 cc; the RSA's volume is about 675 cc. But they open their rotary inlets when they want to; they're not at the mercy of any stubborn reeds.

Several riders of the Cagiva 500-4 works racers experienced a painful demonstration of this stubbornness:
When closing the throttle for a corner (a 500-4 will need that from time to time) engine power dropped. But when they reopened at the corner exit.... nothing happened. The reeds had to be opened by the suction of the exhaust pipe, but when there is no combustion, there is no suction. So the riders opened up a little more. And a little more. And more.... And then, at some point, there was once more sufficient combustible mixture in the cylinder to be ignited. The pipe suction returned from its coffee break and the whole two-stroke resonance cycle was reinstated - with the four carbs wide open. That hurt....
The problem was solved by inserting thin strips under the reeds, so they never really closed completely. It messed up the carburation and cost over 10 HP, but it improved both the lap times and the mileage you could put on a rider.
Later, because of those carburation problems, Cagiva was one of the first to switch from carbs to injection.

[andrew a]

Well done Av you rode well. Very well indeed. Yes I got laped. I did a bit of off track grass work! Anyway there was no way I could get anywhere near her pace. Well done to Av and team ESE.

.
Av smokes em at Tokoroa.

Just had a race report.

Race 1 Av starts of the back of the grid, works her way through the field and takes the win.

Race 2 Av starts from row one and wins again.

Race 3 Av takes the win after lapping the entire field including the current F4 GP champion.



Attachment 256696
Av and Chambers at Taupo

Av's bike was prepaired and tuned by Chambers, from Team ESE.

[wobbly]

As always Frits your keen mind keeps us on the straight and narrow path.
I fully realise that the pipe sucks like hell at BDC,the sim pressure ratio trace shows that dramatically when the diffuser shape is correctly designed.
Pipe depression causes a big pressure ratio across the transfer duct/cylinder boundary, and it is this effect that causes the bulk flow around BDC.
But what I was alluding to, was that to then go on to say that the pipe opens the reeds, around BDC, just isnt true.

Re the carb venturi - having the smallest point within the carb up at the slide will reduce the divergent angle up to the RV area.
All I was suggesting was that the flow bench would establish if that "slow" divergent angle made any tangible difference to the ( steady state ) flow capability.
It may "look" right but I know enough about flow tests to know that what looks good sometimes ( often) isnt.
If bad turbulence created a flow loss capability, the bench would show this immediately, on the dyno it could be several things causing less power to be produced.

What i was saying re Yamaha and the bikes they built around 1998, was that prior, Rainey kicked arse due to his talent and the work put in by the team to fix the problems.
About that time they then changed alot of the basic elements, ran a CNC anemometric flow tester etc, and suddenly a heap of riders were on machines that could win, even the privateer WCM guys had a fighting chance.

Yamahas spool valve would seem to be the best system for a single or 3 port setup.
It is always close to the piston, no matter what leading edge height it has, and can also control the secondarys at the same time.
Aprilias multi section blade is a good patch up of a flawed design, but it doesnt control the secondarys - maybe not such a big issue in a full noise application.

For the T port, Hondas dropping gate works very well.Its design in the RS250 cylinder is much better than the ones Husaberg showed in that the pivot point is alot further
away from the piston.Thus the arc away from the piston is alot slower.
Suzukis twin multi section tubular valves are complex but clever as well, and like Hondas gate they conform well to the port roof when open.

[F5 Dave]

No doubt someone will "pipe up" with a couple of cliche's about the bike.
but Kevin Cameron says what i would describe as some interesting things in this article regarding the development path of this and other TZ Yamaha's.

Could someone more learned than myself ever confirm or more likely deny a few bits in here as it seems to go against some prevailing wisdom in regards to a few technical pieces.

I could be bothered highlight the relevant piece's as the highlighter always moves.

What kevin Cameron mention's he has also mentioned Mculloch engines doing it as well in regards to the Reeds.
I personally found the bits about the squish clearance and band width a bit confusing. But i might be more thick than i originally thought.

The reasoning for the flat slides was interesting as I had not seen it described like that before.

Also forgott incredibly ugly intakes what "up" with that.

Missing a page there?

[dinamik2t]

Wrong, wrong. The 'plug' of mixture in the intake duct strongly resists being accelerated towards the crankcase; the crankcase pressure has dropped quite a bit (slowing down the transfer flow in the process) before the intake flow starts attributing something useful to the crankcase contents. And the same goes for rotary inlet engines; they too need large crankcase volumes to make real power.
Wob, the pipe does suck like hell on the cylinder and hence on the crankcase. It just doesn't show at the reeds until a lot later because of, like you say, petal stiffness and column inertia.

Here is a sim trace of a RGV100 at 13,000 making 40 odd crank Hp.
BDC is exactly between TPO and TPC, the reed lift down the bottom isnt showing the reeds much open till TPC - well after BDC, so the pipe action isnt affecting the reed lift at all, apart from
a delayed reaction due to petal stiffness and column inertia in the intake.
Re smaller case volume, I have measured one of those engines and its case com is exactly 1.3 on one side and 1.29 on the other with around 540cc from memory..
This is alot smaller than an Aprilia at 640cc.
But its case vol is relatively large in comparison to 2T technology at the time.
In a 125 project I have just finished, with a case reed, 1.3 gave the best result.
Going down to around 1.24 of the RSA spec lost around 2Hp with the reeds, no matter what I did with intake length and petal stiffness, pipe geometry or carb size.

Frits, Wob, could you give us an insight, into how one can use the big volume of the crankcase effectively, in a high performance design? Would there be any rules connecting crank volume with ducts volume or pipe volume?

I simulated two different ratios in EngMod, and the higher comp/smaller volume was up by 1+hp. Both with the same tfr duct volumes (~78cc).
I did a hasty overlay of the pressure waves of the intake and exhaust:





The higher comp case caused the reeds to open less. Tfr pressure was higher from Ex open until just-before Tfr closed. Crankcase pressure was higher too.
On the exhaust part, difference was mainly betweet Tfr open and close, both for cylinder and exhaust pressure - higher comp produced the higher pressure.
Also, delivery ratio was much bigger in the high-comp, while TubMax was slighly less.

edit: I don't know whether I am missing something here, but EngMod kind of shows what you told us about 'pipe sucking from tfr ducts and that vol being important'.
I run the same as above, with 1.45 crank comp ratio, to see a number of 30.4kw. Then, with longer TFR passages (new vol about 100cc), with 1.3 CCR it showed 33.2kw, while with 1.45 it rised to 33.6kw.
I think it favorises a little the high primary comp ratios.

[speedpro]

A layman's (mine) view of the effect case volume has is that a larger volume has a smaller drop in pressure given any particular volume transfer up the transfer ducts. As it is the pressure differential between the cylinder and the case that causes the transfer flow having the largest possible pressure differential for as long as possible will result in the maximum volume flow possible. As with anything in pesky 2-strokes there is a trade-off and therefore an optimum value of crankcase volume given any particular application.

You could go for smaller volume, higher compression, crankcases but that would only benefit initial transfer flow before the crankcase pressure dropped. However there may be some advantage in this setup with smaller transfer ducts if the energy in the initially rapidly moving mass in the transfer ducts could be used.

Maybe.

[TZ350]

Try putting the venturi directly behind the slide like Lectron did - this will shorten up the divergent length with much slower angles out to the RV port area.



Easy to test the flow capability of the varying venturi positions and divergent angles on a flow bench before hitting a dyno.

This is what my ventori tube looks like, flow is from left to right, two ramps, leading ramp is 34 deg included and trailing ramp is 14 deg included angle.

Could the flow be improved by making the leading edge ramp into an aero foil shape like the leading edge of an aeroplane wing as in your picture.

It would certainly shorten up the tube and get the venturi point closer in behind the slide.

[husaberg]

Missing a page there?

Last one wouldn't fit but was not not real interesting but here it is.
If you are meaning the carb explanation it is on the bottom paragraph of the first page in the original post attached on the left column.Well bugger it if that is what you are after this highlighted bit