ESE's works engine tuner

[TZ350]

If the volt drop across one diode is about 0.6V, then surely the drop through a bridge must be 1.2v? Maybe this is why you're not getting enough signal.

Edit: The more I think about it, a bridge rectifier will just turn the signal into a not very smooth DC output. Try just using a single diode in line.

Yes I think you are right. 1.2 1.4 volt drop and maybe the half wave may work better, I will try it.

[Frits Overmars]

Can you plate a laser sintered cylinder?

Yes, you can plate a laser sintered cylinder if you can plate the aluminium it is made of. From memory, the material which almost every company offering this service has on their portfolio can be plated.

If you want to make sure, check with the laser sintering company and with the plating company.
When I had my cylinders lasered, experience with the process was still limited, so I sent some test samples to the plater before going all the way.
We used AlSi12 powder.

[lohring]

Yes, you can plate a laser sintered cylinder if you can plate the aluminium it is made of. From memory, the material which almost every company offering this service has on their portfolio can be plated. For a 26cc cylinder this might have even become affordable in the meantime (what you have to pay is mostly linear to the weight of the part).

As I've never seen any real world dyno graph of a "symmetric 2-stroke", be it FST, FOS, Rotax, Ken or Neils engine or any other (please let me know if I missed something), would you show us the comparison from the simulation?

I'm working on the real designs now for a better comparison. Learning Fusion 360 so I can build a more exact model of the engines to simulate is taking a long time. My day job keeps getting in the way as well. I'll post a couple of designs as well as the simulations when I get them finished.

Lohring Miller

[tjbw]

Yes I think you are right. 1.2 1.4 volt drop and maybe the half wave may work better, I will try it.

Did you try a low pass filter?

It can be as simple as a resistor in series with a capacitor in parallel.

https://www.allaboutcircuits.com/tex...-pass-filters/

Also, you could encapsulate the complete assembly, to reduce any spurious accoustic coupling?

[Jannem]

Perhaps this in a noob question...

Normally the blowdown time area is a struggle, but say if you have an engine designed for lower rpm, with proper pipe and transfer STA, is there such a thing as too much blowdown assuming exhaust duration is also optimal? Or does ex duration move also down enough to keep blowdown always at the limit?
If there indeed can be too much blowdown, then what are the symptoms?

[Frits Overmars]

Normally the blowdown time area is a struggle, but say if you have an engine designed for lower rpm, with proper pipe and transfer STA, is there such a thing as too much blowdown assuming exhaust duration is also optimal? Or does ex duration move also down enough to keep blowdown always at the limit?
If there indeed can be too much blowdown, then what are the symptoms?

If you want a two-stroke with a four-stroke character (and four-stroke-like power) you can reduce the exhaust timing until the blowdown time.area is just sufficient.
If you want a serious two-stroke, you need to take advantage of exhaust pulse superposition and that more or less nails the optimum exhaust timing around 190°.
For a low rpm engine this means that you will only need a narrow single exhaust port. If the port is wider than necessary, you will suffer increased loss of fresh mixture,
resulting in power loss, high specific fuel consumption and dirty exhaust gases.

[Jannem]

And if you used 190* exhaust open, wide and low height port opening, you’d have less mixture loss, but also narrower tuned range, because of shorter pulse?

When the blowdown is “right “ for specific rpm, how much of the time area is sonic choked?

[wobbly]

No - due to the strong superposition effect the power band is way wider than normal with a port down at 190*.
When the blowdown is " correct " the outflow from the increasing piston port area is sonic until almost TPO.
Look at this outflow Mach trace of a KZ10C that has theoretical blowdown just sufficient for over 50Hp at 13500 ( crank )
It makes exactly that,in the sim and in reality.
The residual blowdown pressure above the transfers is what enables port stagger to influence the scavenging regime in the way it does.
With more pressure above the first opening transfer port, than there is below it from the case - there will be instantaneous backflow, until that pressure delta subsides.

[dutchpower]

What you think about this Wobbly

[Jannem]

Trying to comprehend what I'm seeing in the graph:

Blowdown angle is 30 degrees and goes subsonic 8 degrees before TPO, so that means ~27% of the blowdown angle just before TPO is subsonic and somewhat bigger % of time, as it happens after 90deg crank angle? Looks small in the graph, but seems bigger looking at the numbers.

Is that second 0.8 mach peak in ex.port velocity at 218 degrees from diffuser rarefication combined with intake side pressure pulse (+superposition from previous cycle)?

The quick change of direction to .6 mach right after is the end cone reflection (+superposition from previous cycle)?

[lucf]

Grumph, you are entitled to your opinion, but it seems to me that it is based solely on Lucs allegations. I wasn't going to honour his stories with a reaction, but I cannot allow him to put people on a false tract with his alternative facts. There are too many perversions of the facts, both historically and technically, to go into all of them.
I would have thought he already demonstrated his level of civilisation and credibility before on this forum. You don't need to take my word for it; you can check with respectable people like Jan Thiel, Wobbly Wayne Wright, Neil Hintz, Ken Seeber.

Reply after publishing the FST on Facebook April 19, 2013


Van mijn vader had ik gehoord dat hij dit systeem in 1969 uitgedacht had,
hij kon alleen geen goede gieterij vinden die een cilinder kon gieten zonder gietgallen.
Cilinders lekten constant water.
Hij is vanwege tijdsgebrek er weer mee gestopt en heeft het idee uitgelegd aan Frits Overmars.
Die zou er daarna, met modelbouwmotortjes succes mee gehad hebben.

William van Dongen

[flyonly]

Can someone tell me if its as simple as unplugging my alternator to have a total loss system for racing or are there other things I need to consider?

[jasonu]

Reply after publishing the FST on Facebook April 19, 2013


Van mijn vader had ik gehoord dat hij dit systeem in 1969 uitgedacht had,
hij kon alleen geen goede gieterij vinden die een cilinder kon gieten zonder gietgallen.
Cilinders lekten constant water.
Hij is vanwege tijdsgebrek er weer mee gestopt en heeft het idee uitgelegd aan Frits Overmars.
Die zou er daarna, met modelbouwmotortjes succes mee gehad hebben.

William van Dongen

From my father I had heard that he had invented this system in 1969,
he just could not find a good foundry that could pour a cylinder without casting holes.
Cylinders were constantly leaking water.
He stopped because of lack of time and explained the idea to Frits Overmars.
He would then have had success with model construction engines.

[wobbly]

Your graph Dutchpower is from the actual Exhaust port face.
It is much more enlightening to place the transducer at the duct exit, before the transition to the header.
If this hits 0.8 Mach then you know the exit area is correct.
The STA number for the port takes into account the effects of choked flow as the piston open area enlarges.
While you are at it look at the Mach at the stinger entry, again 0.8 Mach is a good place to be starting with that.

Re total loss - many times a CDI system like an Ignitech will perform alot better if the charging system is connected.
This is due to the voltage being around 14V and the DC DC converter transforms this increase from the lower 12V a battery produces , to
a much higher voltage at the plug.

[Pursang]

If you want a serious two-stroke, you need to take advantage of exhaust pulse superposition and that more or less nails the optimum exhaust timing around 190°.
For a low rpm engine this means that you will only need a narrow single exhaust port. If the port is wider than necessary, you will suffer increased loss of fresh mixture,
resulting in power loss, high specific fuel consumption and dirty exhaust gases.

So, a power valve system that brings in and out the auxiliary ports would/could/should be better than one that adjusts the port height and ex. duration.

cheers, Daryl.