ESE's works engine tuner

[diesel pig]

The beauty of the turbo rg50 is you can use all the power a lot and it can't get out of hand try to hurt you. Good for tuning driveability

Could not of said it better myself.

[Haufen]

transparent two-stroke cylinder

[OopsClunkThud]

That is the single most difficult thing to find! There used to be a special test bench at QUB to measure it but is has since been scrapped as QUB has moved away from engine development. They printed over a thousand cylinders to test but I have not been able to find the results anywhere. Honda built their own but according to Prof Blair they could never get it to function correctly. Today the characteristic is an output of unsteady moving piston CFD simulations which is another ball game altogether.

Assume you are you referring to the "QUB single-cycle gas scavenging apparatus".

A CFD simulation of this setup has been done and could be way more useful than the physical setup in speed of results as well as insight of what happens inside the ports throughout the cycle. Sadly it combines all the really hard and non-standard CFD corner cases of unsteady flow, moving geometry, and mixing gases. Each of these has some limited support in the CFD packages but are often mutually exclusive. The customization and setup of the software to do it seems almost harder than the physical test rig.

But to have that CFD process in hand with a somewhat efficient workflow for setting up the test cylinder mesh would be a dream.

[Vannik]

A nice video on the uses and explanation of WaveViewer2T:

https://www.youtube.com/watch?v=jaAE-Bq2lvo

[skako]

A nice video on the uses and explanation of WaveViewer2T:

https://www.youtube.com/watch?v=jaAE-Bq2lvo

Many years ago, at the very beginning of my work, in a company that made trucks in the north of our region, I found a book in the library by Prof. Jante and Dr. Hofmann "Uber Verbrennungsmotoren und Kraftfahrwesen" Band 2, edition from 1959.
In it, Dr. Hofmann in his Dissertation calculates and clearly shows the waves in the intake pipe of a 2T engine with a piston-controlled intake. Dr. Hofmann's presentation about waves in the intake pipe is accompanied by many graphs that show the size of the outgoing wave from the intake port and the size of the return reflected wave (which is delayed by some time delta_t depending on the length of the intake pipe and the sonic velocity of the atmosphere).
The graphs clearly show the superposition of those two waves and their effect on the intake port. Then I learned that the superposition wave is the only one that we can measure at a certain position with very fast electronic sensors, and also that it is composed of two waves that we cannot measure but can approximately calculate.
Based on that procedure, I made a suction Basic-program on my first home 8-bit computer (Schneider CPC 464) where I could see the first suction graphs. I was very happy about that, because I saved some costs about measurements.

[rgvbaz]

A nice video on the uses and explanation of WaveViewer2T:

https://www.youtube.com/watch?v=jaAE-Bq2lvo

Thanks Neels

I hope it can be of some use.

Edit - please read the pinned comment in the comments about my error in stating that the left and right waves are theoretical. They aren't, they can't be measured as they both merge and form the superposition pressure - they are real.

Cheers

Dave

[rgvbaz]

Many years ago, at the very beginning of my work, in a company that made trucks in the north of our region, I found a book in the library by Prof. Jante and Dr. Hofmann "Uber Verbrennungsmotoren und Kraftfahrwesen" Band 2, edition from 1959.
In it, Dr. Hofmann in his Dissertation calculates and clearly shows the waves in the intake pipe of a 2T engine with a piston-controlled intake. Dr. Hofmann's presentation about waves in the intake pipe is accompanied by many graphs that show the size of the outgoing wave from the intake port and the size of the return reflected wave (which is delayed by some time delta_t depending on the length of the intake pipe and the sonic velocity of the atmosphere).
The graphs clearly show the superposition of those two waves and their effect on the intake port. Then I learned that the superposition wave is the only one that we can measure at a certain position with very fast electronic sensors, and also that it is composed of two waves that we cannot measure but can approximately calculate.
Based on that procedure, I made a suction Basic-program on my first home 8-bit computer (Schneider CPC 464) where I could see the first suction graphs. I was very happy about that, because I saved some costs about measurements.

That sound like a really cool program - did you use it to develop intakes and exhausts?

This is an extract from a SAE paper, it's 4 stroke but seems to give reason to why Dr Blair was keen to be able to predict these waves despite not being able to actually measure them too.



Cheers,

Dave

[wobbly]

Also many years ago I had a long discussion by snailmail with Dr Fleck at QUB about the left/right waves and their superposition.
My assertion was that if you had a pair of sensors at a set distance apart , a fast processor could detect each wave and then display its direction / speed /amplitude from the time delta of the signal across this sensor pair.
He did arrange to have a student work this up as a part of a dissertation , but in the end it proved "too difficult " in reality , and the student went on to complete his Phd on a new code
methodology that ultimately was used in a commercial engine sim.

[skako]

That sound like a really cool program - did you use it to develop intakes and exhausts?

This is an extract from a SAE paper, it's 4 stroke but seems to give reason to why Dr Blair was keen to be able to predict these waves despite not being able to actually measure them too.



Cheers,

Dave

Dr. Hofmann gave a calculation procedure for a suction pipe with subsonic flow.
I wrote the Qbasic code according to that procedure, for intake into the engine crankcase. It looks can be seen in the appendix.
The procedure was applied to a straight pipe of constant section.
Exhaust pipes are much more complex and they were processed by Prof. Blair.

Also many years ago I had a long discussion by snailmail with Dr Fleck at QUB about the left/right waves and their superposition.
My assertion was that if you had a pair of sensors at a set distance apart , a fast processor could detect each wave and then display its direction / speed /amplitude from the time delta of the signal across this sensor pair.
He did arrange to have a student work this up as a part of a dissertation , but in the end it proved "too difficult " in reality , and the student went on to complete his Phd on a new code
methodology that ultimately was used in a commercial engine sim.

There would be no use in measuring the left outgoing wave because it is generated again as a right return wave.
With a certain delay, the right return wave is superimposed in front of the observed port and somewhat cancels the original (left wave).
This means that again you can only measure the superimposed magnitude of those two waves at that point at that time.
At any point on the exhaust pipe, the pressure sensor will measure some pressure value that is currently the sum of the value of the left wave with some of the pressure values of the right wave. These are the values that found themselves in that position at that moment.
When you look at the left outgoing wave, think of it as the composition of a train with many wagons. Each of the wagons has a certain size of load (pressure) that it transports.
The measured size is the sum of these two left and right wave sizes at that moment in that position. Let's imagine that the 76th wagon of the outgoing wave was in that position (as expansion pressure) and that it met the returning 13th wagon of the right wave (which carries a strong compression pressure during the blow down time).
Therefore, all measured quantities are always superimposed wave quantities.

I'm sorry I can't express myself better because I have to use a translator.

[Vannik]

Also many years ago I had a long discussion by snailmail with Dr Fleck at QUB about the left/right waves and their superposition.
My assertion was that if you had a pair of sensors at a set distance apart , a fast processor could detect each wave and then display its direction / speed /amplitude from the time delta of the signal across this sensor pair.
He did arrange to have a student work this up as a part of a dissertation , but in the end it proved "too difficult " in reality , and the student went on to complete his Phd on a new code methodology that ultimately was used in a commercial engine sim.

This was eventually done at a French university. They used 2 high frequency response transducers and fairly advanced mathematics to separate the left and right moving waves from the signal, but it only confirmed the theory and did not show anything new.

[rgvbaz]

Here's an open access paper - The application of PIV to the study of unsteady gas dynamic flow within pipes and at pipe discontinuities by VD Thornhill, R Fleck, H Li and J Woods

https://iopscience.iop.org/article/1...96/85/1/012002

The apparatus used produces discrete waves that were observed without being superposed.

Regards

Dave

[Gradella23]

hello everyone,
has someone ever tried a 3d printed reed valve? I found some fuel-resistant materials, but i don't know how to replace the viton coating (that needs a mold etc.).
Are there some sort of spray coatings or paints than can resemble that effect?

thanks so much for all the knowledge shared here!

[ken seeber]

hello everyone,
has someone ever tried a 3d printed reed valve? I found some fuel-resistant materials, but i don't know how to replace the viton coating (that needs a mold etc.).
Are there some sort of spray coatings or paints than can resemble that effect?

thanks so much for all the knowledge shared here!

Just get some raspberry juice, thongs and walk around for a bit....

https://www.youtube.com/watch?v=sKC2027ynMg

[husaberg]

hello everyone,
has someone ever tried a 3d printed reed valve? I found some fuel-resistant materials, but i don't know how to replace the viton coating (that needs a mold etc.).
Are there some sort of spray coatings or paints than can resemble that effect?

thanks so much for all the knowledge shared here!

google FKM liquid. you will come up with products. Like below.
https://www.thermodynglobal.com/prod...ting-thp-2000/
Vitons a trade name. Like Vaseline

[Gradella23]

Just get some raspberry juice, thongs and walk around for a bit....

https://www.youtube.com/watch?v=sKC2027ynMg

google FKM liquid. you will come up with products. Like below.
https://www.thermodynglobal.com/prod...ting-thp-2000/
Vitons a trade name. Like Vaseline

Thanks guys, i'll take a look.
This is what i'm working on: a 50cc Cagiva Prima racer.
This prototype reed valve is made to fit an Ibea 30mm carb on it, which has a 33,5mm exit diameter. It's a little bit large but i tried to arrange an acceptable internal duct.
This engine already has a nice inlet shape, and was born to also fit a 75cc so it has a 47mm large crankcase (bigger than a Minarelli or Derbi).
The cylinder base is with external studs so it's been possible to design a cylinder with proper transfer ducts.