ESE's works engine tuner

[TZ350]

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Reminds me very much of New Zealand Bucket racers. Great ideas, build a dyno in the garage to test things, clever engineering solutions and lots of enthusiasm. Many world beating ideas tried but not every idea worked out. I like watching him work.

[Frits Overmars]

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Reminds me very much of New Zealand Bucket racers. Great ideas, build a dyno in the garage to test things, clever engineering solutions and lots of enthusiasm. Many world beating ideas tried but not every idea worked out. I like watching him work.

I like to watch the Two-Stroke Stuffing-videos too. I even like to think that from time to time Alex comes up with ideas I put into his mind, so he may be excused for making all the mistakes that I used to make. He is also adding a few of his own. Never mind, it will all lead to KISS-awareness .

[Frits Overmars]

Frits, thank you for these gems.
I suspect your memory of their details might be hazy, but I'm going to ask anyway: In the squish program, what is the "number of crankshaft degrees"? Is it the exhaust open duration, or the EO point? Or something else?

It's the number of crankshaft degrees, and the number of calculation steps, from the start of the squish calculation until Top Dead Center. It should all become clear if you hit the L-key.

While we are on the subject, I prepared two List-screenshots. The first one looks like all the other Maximum Squish Velocity programs you can find on the internet.
I entered the Aprilia RSA-data of 0,7 mm squish clearance and 13000 rpm, but I ignored the dynamic stretch of about 1% of the stroke. The outcome is a maximum squish velocity of 64 m/s at 11° before TDC.
For the second screenshot I included the 1% dynamic stretch. Now the maximum squish velocity has skyrocketed to 144 m/s at 5° before TDC.

Some difference, isn't it? Need I say more about the usefulness of those other MSV-programs?


By the way: you cannot have too much squish velocity. You can have an ignition system that isn't up to it.

[F5 Dave]

My point was he needs a non experimental engine to set up his experimental dyno and see if it will actually give decent numbers over a reasonable range that replicates how the engine will be used.

[lodgernz]

It's the number of crankshaft degrees, and the number of calculation steps, from the start of the squish calculation until Top Dead Center. It should all become clear if you hit the L-key.

Thanks Frits.
I found that the program produces the same MSV no matter what crankshaft degrees I enter, so I'm still unsure how to use that parameter.

Also, one of the parameters is "squish centre gap". Is that the squish clearance at the inner edge of the squish band?

I'm surprised that the Exhaust timing is not a parameter. Wouldn't the starting point of the compression phase be important? What am I missing here?

[wobbly]

Frits is being clever , I think . The squish mid point gap allows for those deluded people who believe a tapered ( diverging ) squish is a good thing.
It isnt , but entering the average squish depth allows for this.
This deviates tho from something I think Neels wrote about that very point .From memory his logic was that with a taper , at the bore the velocity may be higher , but the lowest velocity is at the curtain area around the
bowl edge.
This is where it actually matters ie this is the point where the turbulence is created that increases the flame speed.

I was going to disagree with Frits statement that there is no such thing as too high MSV , as in many experements with squish width and depth it always seemed the best compromise
for MSV was around 40M/s - this being the number generated by the usuall programs that dont allow for rod stretch. Over that MSV level overev is always lost with a comensurate increase in mid power , but if you think about what the real world result is of high MSV is ie increased flame speed across the bowl , this equates directly to the same effect as an increase in spark advance ,
without the attending losses due to excess charge compression whilst its still starting to gain burn speed.

Thus its clear that increasing MSV , while retarding the spark advance where overev power loss begins , is a better power making compromise - very easy with a digital programmable ECU.
This must also overcome the downside of unburnt charge retention in a wide SAR , but if the piston is all but hitting the head , there is no charge retention to speak of.

Nowhere is this effect more evident than in KZ kart engines with a dumb , but easy to tech , straight line ignition.
Any less than 0.8mm squish depth , or any more than 35% SAR , and all the overev power dissapears ( past 14,000 ) - MSV 26.5 M/s
You can easily retard the static advance , to regain the lost power range , but then all the mid power is lost ( down at 10,000 )
As always , no free lunch.

[F5 Dave]

I came home for lunch today. I'm not sure if it was free, but the wife was very accommodating.

[Frits Overmars]

Thanks Frits.
I found that the program produces the same MSV no matter what crankshaft degrees I enter, so I'm still unsure how to use that parameter.
Also, one of the parameters is "squish centre gap". Is that the squish clearance at the inner edge of the squish band?
I'm surprised that the Exhaust timing is not a parameter. Wouldn't the starting point of the compression phase be important? What am I missing here?

The number of crankshaft degrees determines how long the list is going to be, in case you wish to print it. The default value is from 20° before TDC to TDC, because that is the only zone where squish effects are going to play a role. But if you wish to see piston position, velocity and acceleration over a bigger part of the stroke, you can enter your desired number of crank degrees.

You are right about the squish centre gap.

The starting point of the compression phase makes me think of those geniuses who insist on using 'effective' versus geometric compression ratios although they have no way of knowing the pressure in the cylinder at the point of exhaust port closure because that strongly depends on what the pipe has been doing.
The squish velocity is independent of the gas density in the combustion chamber. The kinetic energy with which the squish flow blows the ionized molecules between the spark plug electrodes aside, is dependent of the gas density, but that is another story.

Come to think of it: that story deserves to be told, and it would fit right in.

An ignition system, trying to set a combustible mixture on fire, has three enemies: electrode gap width, squish turbulence and compression pressure (actually there are also some secondary enemies, like mixture strength and mixture purity, but we will leave that out for now).
The voltage, required to jump an electrode gap, is proportional to the gap width, like 10.000 Volts per millimeter or something like that.
The voltage between the electrodes ionizes the molecules in between, and once there is a complete path of ionized molecules, a current starts flowing: it sparks.

The problem with squish is that it blows away the ionized molecules, so it takes more voltage to initiate a spark. As I said earlier, you cannot have too much squish, but you can have an ignition that isn't up to it.

Above I said something about the required 10.000 Volt per mm gap. But that is in still, ambient air. If the air pressure rises, so does the resistance of the air between the electrodes.
An engine with a good cylinder filling may have a pressure of 30 bar between the electrodes by the time a spark is due.
An ignition that is not up to the job, may start playing havoc as soon as the engine comes into the power band and the compression end pressure in the combustion chamber rises. Combustion will suffer and the next compression cycle will yield a lower end pressure, so the ignition will function again. The power curve will look like a sawtooth graph.
If you suspect that your engine may be suffering in this way, there is a really simple way to find out: reduce the electrode gap to about 0,2 mm. It that helps, get a better ignition.

Below are two power curves from experiments with a 125 cc KZ kart engine back in 2010: one curve with the ignition system prescribed by the regulations (yes Wob, it was the same brand that you are still compelled to use today) and one with exactly the same engine, nothing changed, except I fitted a better ignition.


PS: a dropping battery voltage in a battery ignition system makes itself noticed in the same way.
The engine will still run OK part-throttle, but when you give it full throttle, the compression pressure will rise and the engine will protest.

[lodgernz]

Thank you Frits and Wobbly. Great information as always.

[husaberg]

Attachment 257539

Attached to the float bowl is a large adjustable needle jet purchased from a Model Shop.

What was that adjustable needle valve from Rob?

[philou]

[TZ350]

What was that adjustable needle valve from Rob?

It was just an accessory something in a plastic bag with a lot of other things in bags on a rack at a model shop. No idea what make/model of engine it was for.

[Peter1962]

some more pictures of the Laszlo Peres Maico























In this article you can read about the second prototype that he made, in 1983
https://www.motorradonline.de/modern...r-qualitaeten/

[philou]

What was that adjustable needle valve from Rob?

dellorto offers one

[F5 Dave]

Oh good lord Peter, that looks like Heresy. Burn it.