ESE's works engine tuner

[SS90]

SS I assume your rambling post a few pages back was done on a Friday night after the effects of some mind altering drugs that bring out a Jekyll & Hyde personality.

I work in the electronics industry & it irks me that some characters talk in ever increasing TLAs (three letter acronyms, it is of course a PT to give it an acronym). Sometimes it simplifies conversation & documentation, but it spirals out of control & the purpose ends up becoming to hinder communication & make those ‘in the know’ of these meanings feel special about themselves. QA & wanky management use TLAs for the same purpose.

So no; I’ve never heard the TLA CVF. So therefore I must be behind the times. Well, - behind the times in scooter design marketing speak. Whoopie.

Since the dawn of time people have been adding more transfer ports, often fed by the piston with holes near the top. This does smack of a compromised transfer arrangement. To put them in the main transfers more so.

I suspect this is borne of your typical scooter having a very compromised crankcase design affecting where you can place & feed transfers. Sometimes you really have to work with a compromise & go in that direction.

For instance my 50 has a dumb arrangement where the intact is primarily a piston port, but has a reedvalve passage to the crankcase. Also due to this the transfers also feed the rear ‘boost ports’ that would otherwise be fed from the reedblock, (often directly). This is a compromise & was popular on RMs (& some very early KTMs I think). But ultimately it has been discarded by mainstream. However it can work acceptably. My 50 still retains this feature, although I do appreciate its compromise. The fact that this engine has spanked Aprilias & Derbis in the past attests to this. . . and the odd aircooled 125, well, all of them at Taupo.

I suspect you are next going to be introducing collide stream porting as the big secret (Kevin Cameron did an article on this using 91 TZ250 as example, but had been used to some extent well before this).

But I am getting a bit tired of the attitude that is coming with all this. Some very condescending tones are super evident. Why come with attitude?

I’d say there is only one person on KB who I’d call a 2 stroke expert. And he frequents the suspension forum & never talks about 2 strokes.

I think I have already established alot of what you pointed out here F5....... My purpose was to, show that some guys where getting "lost in the woods", and where missing some fundementals.

Afterall, this isn't a "how a two stroke works" topic, but sometimes reverting back will remind us all that we don't know everything, and never will (even if it is unlikely that none of us will admit that this has made us all research topics, and become better off for it)....


Bronze heads indeed!

(No offence intended.)

[Chambers]

Afterall, this isn't a "how a two stroke works" topic, but sometimes reverting back will remind us all that we don't know everything, and never will (even if it is unlikely that none of us will admit that this has made us all research topics, and become better off for it)....


Bronze heads indeed!

(No offence intended.)

Like you say SS90 you don't know everything!

Bronze heads were a great idea in their day. Bronze is a better heat conductor than cast iron and the valve seats could be cut directly into the bronze. At the time aluminium alloy was not sufficiently developed for its hot strength to be able to reliable hold valve seat inserts. Later cast sculls for the valve seats and plug were used in alloy heads up to the 50's.

SS90 your well read but talk a lot without saying anything. and usually about things we have already been over in our own research.

A couple of quick sketches of where you think we are going wrong and a sketch or two on how we can improve it and your a hero otherwise your zero.

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[SS90]

Granted,
But, that was a long time ago (like a cast iron head)
The point I am/was trying to make is that aluminum is far better than Bronze, and that I failed too see the logic in that discussion, especially as it was also heading towards coating the Cylinder head in Gold..........

I see the point in discussing the Bronze head/coating options, but the way the thread was progressing, it seemed like all this guys hard work was being compromised by some steps in the wrong direction.

I don't want to be a hero in this, or any other situation, I am trying to assist and encourage.

While I am unfamilure with posting in a forum, and as such lack the literary skills needed, I feel that I have written in such a way that many people who read this thread, and have not done research, can follow and learn, as you are aware, the people who contribute can all write in such a way that very few would understand, even though the subject matter is more simple than most realise.

I hope this is the end of personal attacks, and we can continue back to the thread, and I hope TeeZee can show us a few dyno runs as the engine is now (ignoring the 17 runs theory, and just see what it has (in so far as curve shape etc), and after some attention to some things we have discussed, put it back on the dyno and compare the curves.)

That would be a good way to continue (and advance) some interesting discussion.

In the direction of TeeZee's engine, (and to change the current line of subject) I am thinking (after re-reading his earlier posts, in particular a race report) there is a big low R.P.M torque deficit (I make this statement after reading how he has to slip the clutch "all the way round the track").

After our discussion about the likely Primary compression deficit, can anyone offer a solution for that? Or at least some theories (researched or otherwise)
.....I am thinking one (a solution) that would also lower the cylinder head temperature......

[F5 Dave]

There is a surprising amount of cooling provided by moving & thus attached to a dyno the fan provided is comparatively puny despite feeling like you are being blown around. Watercooled bikes will start to over heat after several runs on the trot. However it is important to ignore the first few runs or they may well end up being the best of the session. I like to do a few runs & then let the top end cool a bit & then test in earnest. This gives the crankcase time to heat up to operating temperature.

Which brings me to the ‘slipping the clutch’ bit. The GP has a 5 speed gearbox so there will always be more of a gap esp on a very tight kart track like mt wgtn. Presumably you have geared down as low as required for here?

[TZ350]

Which brings me to the ‘slipping the clutch’ bit. The GP has a 5 speed gearbox so there will always be more of a gap esp on a very tight kart track like mt wgtn. Presumably you have geared down as low as required for here?

The GP's 5 speed gearbox is all ways a problem especialy 3rd.

In hind site I realise I was a bit over geared at Taupo but still would not have been shy about using the clutch.

I find gearing, is always a compromise between acceleration in some corners or smooth drivability through other corners at Mt Wellington where I find its easy to be under geared and over revey.

If I can set it up to avoid a gear change between corners like the infield and pull strongly out of another corner or two I recon I've got it about right and compromise by using the clutch to enter/exit others.

In difficult corners I often flick it down a gear, buzz the motor up on the throttle and slip the clutch entering the corner as well, I find slipping the clutch in this way before the apex, steadies the bike other wise it bounces around on the over run.

When diving for a gap a dab on the clutch helps there too.

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[saxet]

SS90 your well read but talk a lot without saying anything. and usually about things we have already been over in our own research.

A couple of quick sketches of where you think we are going wrong and a sketch or two on how we can improve it

.

Some more concise info would be very cool. I can see a few possibilties e.g. a tuned length tract to make use of preessure pulses but somehow I doubt it. Or maybe viewing the tranfer tract as the header of an expansion camber and shaping it accordingly to extract fuel/air from the crankcase into the combustion chamber.
I'm probably one of the least qualified,experienced posters on this thread so I've got little in the way of reputation to lose.But I'm really guessing in the dark cause like most people posting on this thread I've got little resources to put into any personal research.

[TZ350]

The GP has a 5 speed gearbox so there will always be more of a gap esp on a very tight kart track like mt wgtn.

I am looking at changing the primary gear ratio from the 3.2:1 (from memory) to something closer to 2.5:1 this should bring the ratios closer together.

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[koba]

Experience (and research) tells me what I will find already (smaller carb, hotter engine), but, I will attempt to obtain the data in a timely fashion.

I dont get this bit.

I'm not trying to be personal or anything either but I just don't understand it.

Small hole = high airspeed = cool inlet charge right?

My Volkswagen has a 28mm carb on a 1500cc four-stroke engine, the small hole and long inlet manifold lead to manifold icing! yeah, none of this cold air induction shit, it needs to be heated in winter so it doesn't freeze up!

While this is a totally different example I would have thought the theory would carry over at least in part.

Could you give us an idea of why? even without data to support it yet.

[diesel pig]

I am looking at changing the primary gear ratio from the 3.2:1 (from memory) to something closer to 2.5:1 this should bring the ratios closer together.

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Thats an interesting idea TZ, How do you think you will go about doing it?
Adapt the primary gear ratio off an other small motor, Suzuki small two strokes engines have very similar gearbox and crutch designs it might be possible. Or will you bite the bullet and get a set made? Kickaha had a look at doing this and got quotes along the lines of 5 to 4 hundred bucks.

[speedpro]

I've played with tuned length inlets on a disc valve 50. Very interesting results. When it was on resonance it was REAL good but an absolute pig everywhere else. The noise was pretty amazing as well. I tried the carb next to the disc valve and also at the end of the tuned length. Tried different diameters as well. End result was that you are better off without any resonance in the carb. From experimenting on a dyno the only resonance you need to worry about is reed valve petal resonance - it needs to be above the operating frequency or power tapers off. It's interesting watching the "stand-off" at the entry to the carb during dyno runs. Typically there is lots with the revs low down, then it disappears suddenly as the revs rise and then right at the top you can get a bit back again, probably due to reed valve issues. Though it did essentially the same thing on a piston port engine as well.

With another bike I built with a bit of bottom end power missing, I increased primary compression and definitely improved bottom end. That is the power off-pipe was better. No dyno runs back then so no actual numbers.

[speedpro]

I still think the copper head lining with some sort of shiny coating is worth trying. We all agree that heat is the killer in an air cooled 2-stroke and TZ350 has already explained the heat conduction properties of copper. Next time I'm making a copper head gasket its gonna be a biggy though won't be a part of the chamber.

[Yow Ling]

Going back a few hundred pages and after having tons of time to digest them, one idea that keeps me thinking was from the model aeroplane site. Making a diffuser to create high perssure low velocity cooling , as opposed to what we use low pressure High velocity, maybe this is the one scooter thing that is worth keeping, but try and do it without the fan, maybe it needs a full fairing and a couple of properly designed naca ductsand some shrouding around the engine. It sounds so wrong that it might be right

[TZ350]

I still think the copper head lining with some sort of shiny coating is worth trying. We all agree that heat is the killer in an air cooled 2-stroke and TZ350 has already explained the heat conduction properties of copper. Next time I'm making a copper head gasket its gonna be a biggy though won't be a part of the chamber.

I have my doubts about the durability of polishing the copper then using a modern car wax or gold or silver but we do know ceramic sticks and there might be a white reflective ceramic that can be appled thinly.

I haven’t given up on the copper head but until I can get it sorted. I am making another head and copper cooling fin. Following Speedpros suggestions it will be like a big head gasket and the combustion chamber itself will be alloy. It will be sealed both sides by "O" rings, one "O" ring groove in the head and the other in the barrel. Unlike Speedpro my copper fin will extend into the combustion chamber and form the squish land. I think these extra large copper head gaskets have potential.

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[TZ350]

Going back a few hundred pages and after having tons of time to digest them, one idea that keeps me thinking was from the model aeroplane site. Making a diffuser to create high perssure low velocity cooling , as opposed to what we use low pressure High velocity, maybe this is the one scooter thing that is worth keeping, but try and do it without the fan, maybe it needs a full fairing and a couple of properly designed naca ductsand some shrouding around the engine. It sounds so wrong that it might be right

This has got to have potential but I just don't know how to go about it. Did you see how small the opening to the ducting on the model and the aircraft is? and what is low speed and high pressure to an aircraft? travelling at 500mph and 30,000 feet, I just don't know. But its got to be worth a look.

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[TZ350]

I've played with tuned length inlets on a disc valve 50. Very interesting results. When it was on resonance it was REAL good but an absolute pig everywhere else. The noise was pretty amazing as well. I tried the carb next to the disc valve and also at the end of the tuned length. Tried different diameters as well. End result was that you are better off without any resonance in the carb.

Last year we had an Engineering student working with us who for his practical project at Uni had done a study on resonance in the inlet system and its effect on torque.

He and another student set up a motor with no tuned length effect in the exhaust so the point of peak torque would be at the point of inlet resonance only.

They made a device so they could adjust the inlet length. Then they ran the motor, changed the tuned length of the inlet and plotted the peak torque point. After step by step changes and plotting the results it was clear if you could have an automatically varying tuned length you could have a very long, Phat flat and high torque curve.

I can't help thinking about what could be done with an electric power valve actuator and a couple of pieces of pipe that slide inside each other.

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