ESE's works engine tuner

[TZ350]

A RV 2T running with no RV, that is truly epic --- --- very much looking forward to hearing if it's ridable.

Why Epic? A lot of people are riding with broken or missing reed petal -> Strange idle, weaker performance

Why Epic .... well intuitively I have always thought you needed some sort of inlet valve timing control to make a two stroke engine work properly. My guess is most people think so too. It would be truly Epic and rather funny if we have all been clinging to a myth.

Flat earth, center of the universe thinking and tuning myths abound, as an example, I have an old 500cc single cylinder motorcycle with an exhaust valve as large as the inlet and with the single exhaust port opening into two large exhaust pipes.

an example of an early 500cc JAP racing single cylinder 4T engine with Siamese exhaust.

It was an Epic step forward for 4T performance when the need for big exhaust valves and pipes proved to be a myth. Big exhausts must have intuitively seemed right at the time but as with so many intuitive faith based beliefs it was proved wrong and the change in understanding was Epic.

There have been valve less single speed industrial 2T stationary engines that relied on inlet resonance before.

My guess is that a no rotary valve or any sort of valve 2T engine could be made to work well if the inertia of the inlet stream could be varied to match the ramming effect required to keep the fresh mixture in the crankcase as the rpm varied. BrrmBrrrm.

Something like a variable length, or variable area inlet tract or both might make a variable speed valveless inlet 2T work well.

Variable area may not be that hard to do.

[oldjohnno]

Why Epic .... well intuitively I have always thought you needed some sort of inlet valve timing control to make a two stroke engine work properly. My guess is most people think so too. It would be truly Epic and rather funny if we have all been clinging to a myth...

I'd be willing to bet my entire personal fortune - and I own assets to the value of almost sixteen dollars - that it turns out the simplest way to make a two stroke easy to start and run well over a wide rpm range, both on and off the pipe is some sort of inlet valving...

[breezy]

How is this for a 'small leak' ? http://www.youtube.com/watch?v=utfzY...ure=grec_index

Frits is this explainable? there is obviously some way the cylinder is being filled with residual fuel to start combustion. angle of cylinder barrel? or is it on the pipe


come on agnes... im up early for your next experiment

[Frits Overmars]

Frits is this explainable? there is obviously some way the cylinder is being filled with residual fuel to start combustion. angle of cylinder barrel? or is it on the pipe

Anything is explainable (unless it's female) but for now I'll confine myself to guessable: I suppose there was a puddle of fuel in the crankcase, so an igniteable mixture could form. Compressing the cylinder contents and then releasing them through the exhaust port could create just enough mixture movement to get some of it in the vicinity of the spark plug...

[ken seeber]

OJ, you fibber, I would reckon that the left half of your Metralla head would be worth more than $16.

As to full inlet control over anything else, I’m not so sure. What about an unthrottled inlet, whether 24/7 or not? Total flow thru the engine is by the height, hence timing, of the transfers. If some bloke in WA didn’t get distracted with work, kart preparation and local karting politics, we might find out soon. Hopefully.

Agree with Frits, the only way it could have run is using residue fuel or unless there was some other hidden form of supply. Doubt it looking at the circumstances. Mind you, I wouldn’t be doing a “full Monty” ride without any undies on.

[TZ350]

I'd be willing to bet my entire personal fortune - and I own assets to the value of almost sixteen dollars - that it turns out the simplest way to make a two stroke easy to start and run well over a wide rpm range, both on and off the pipe is some sort of inlet valving...

I very much expect you are right.

Some time ago I was plagued by a bad resonance hole and blow back through the carb. I tried some experiments to see what could be done to eliminate it.

My first effort was to close the inlet valve earlier. I originally started with the inlet closing at 80 deg ATDC and closed it earlier and earlier. Eventually I got down to 25 deg ATDC. 25 reduced the symptoms but did not eliminate them and 25 is ridiculously short and badly hurts power so no use at all.



The next move was to try a longer inlet tract. Adding the extra length worked much better than closing the inlet at 25 deg ATDC and the longer tract basicaly eliminated the blow back issue. But the plenum idea had other problems like fuel dropout upsetting the mixture, hence the interest in EFI.



Later, with a carburetor I tried dividing the inlet tract in half with a butter fly at the carb end. The idea was to close half the tract off so as to keep the mixtures velocity up and use its inertia to ram the 6,500 rpm resonance hole and blow back out of existence. Then open the whole inlet area up for top end power.



The idea worked pretty well on the dyno. Blue line is the valve closed. Red line is the full inlet tract area. Unfortunately the arrangement made for an impractically wide engine with the carb sticking way out in the breeze.



But I could put an inlet divider (or two) behind the EFI Ball Valve throttle body with a servo powered automatic stop that prevents the valve opening more than required for the current RPM.

Two dividers would give three basic inlet areas. That way we may be able to have a series of inlet ramming resonant steps that more closely match the stuffing requirements of the crankcase over the full rev range.

Who knows, if we get it right we may not need the rotary valve disk at all.

[husaberg]

Why Epic .... well intuitively I have always thought you needed some sort of inlet valve timing control to make a two stroke engine work properly. My guess is most people think so too. It would be truly Epic and rather funny if we have all been clinging to a myth.
.

Running and starting whilst under little or no load is one thing, pulling itself into the powerband whilst under i would suggest is completely different.
In the case of Adgnes though he has a trick up his sleeve (so to speak) the CVT which might allow it to work as it might be able to stay withing its resonant sped.
Case in point, If the timing of the valve was not relevent then changing the timing of a disc valve would have little effect on the spread of power, yet we all know it clearly does.

It did get we thinking though a spring loaded flapper valve in the inlet. might be a simple work arround.
much like this. with the cable only operating at 3/4 revs or higher and the light spring at low revs....

[TZ350]

Now that looks interesting, thanks.

[husaberg]

...............

[Pursang]

Valveless pumps are not unusual in other applications.



Optimisation of inlet, outlet & pumping actions can only help.

Cheers, Daryl.

[adegnes]

Did anyone say blowback?



I will make up a bunch of different length carb spacers to see where that gets me.

[adegnes]

Frits, I assume you've done more research than most on the subject.
In theory could no valve be better than a properly tuned rotary valve for peak power and overrev?
On the fence here. Keep on without the valve or not? It's interesting, but so is further testing with the valve and methanol/nitro.

[SwePatrick]

I say buy a new valve and carry on hunting for power.
This valveless is just a wild goosechase.
That rejecting airmass you saw need you to get engine into tune before hitting throttle on dyno, in other words it will be really hard to get your roller start spinning.

And by that,, pre heat pipe and incoming air in carb to about 450degree to get the pulsjet going in pipe then start engine

Sounds to me it is a lot of work to be done just to get the moped rolling after been to the walmart for beers

[breezy]

I will make up a bunch of different length carb spacers to see where that gets me.[/QUOTE]

well you gave it a try, i dare say you could play around with spacers and get it to run half decent but maybe it wouldnt be an improvement over the rotary valve. i suppose at the end of the day its how much time you feel you can invest in carrying on, which will decide if you continue. good video again

[Haufen]

On the fence here. Keep on without the valve or not? It's interesting, but so is further testing with the valve and methanol/nitro.

Well, as you have come this far by now, why not try to do some dyno runs? You could use your starting aid to get the engine into the powerband on the roller and then remove it once you've reached a certain rpm. If this works, then proceed with some main jet changes. Do you have a solid baseline with the disc to compare your results to?

If it is not going to work then you could also approach from the other side, by constantly elongating the timing on the disc well beyond what's normally used.