ESE's works engine tuner

[wobbly]

Surely the only reason you have fuel frothing is the crank balance factor is wrong for that engine bolted into that frame.

[TZ350]

Surely the only reason you have fuel frothing is the crank balance factor is wrong for that engine bolted into that frame.

Yes, pretty much. I expect you are right about that.

The carbs are in different places on the engine too and look like they would experience different degrees of movement. The engine is mounted so it can pivot at the back and there are Hondas original RS125 NF4 rubber mounts at the front. Intuitively it looks like the rotary valve carb near the front of the engine would experience more rapid accelerations through a greater arc than the carb mounted behind the cylinder did. Although both would be vibrating at much the same frequency.

The NF4 front rubber mounts allow a lot of up/down movement as apposed to much less forward/aft movement. I don't know which way Honda intended them to be fitted. Might turn the bushes 90 deg to see what that does. I have a good rod kit coming and will look at the balance factor when I fit it.

[lohring]

Here is a different supercharger approach to Alex on a 2 stroke. https://youtu.be/u3UFuCxZ6zs


Sent from my iPhone using Tapatalk

At least he understands that you need to raise the exhaust back pressure along with the intake pressure. The problem is he is throwing away a lot of the exhaust energy. All the power to drive the supercharger comes from the engine. Turbochargers are a better solution. An even better solution is to run really high pressures and take power off the turbine. All this was investigated in the last big piston aircraft engines. Pure turbines were a better solution for aircraft, but not big ship engines.

Lohring Miller

[wobbly]

TeeZee , vertical vibes are the ones that cause rider and frame issues. This is why many race engines are overbalanced , like the TM kart at 58% and a Norton Manx at 80%.
This reduces the vertical balance residual component , at the expense of more horizontal vibration. The lesser of two unavoidable evils.

[TZ350]

... crank balance factor is wrong for that engine bolted into that frame.

A quick fix suggested by Speedpro. When he had problems with his Bucket's rubber mounted engine he found the solution was to rigidly mount it. With the mass of the frame added it changed the dynamics of the engine vibration.



The Nolathane bush is my interpretation of more rigidly mounting the engine. It may or may not work. As Wob says, it is crank balance factor, engine and frame in combination. I will just have to try things until I get a result that works.

Off to the dyno.

Update:- Yes, Speedpro's "more rigidly mounting the engine" idea worked, much better carburation now.

[crbbt]

So they wibbled on about the Lectron advantage and fitted one. Instant 3hp over quite a range.

Sounds great. But, um. . . So what if they'd thrown another jet in the old carb? . . .
But the dyno doesn't lie. Results and big cash prizes could be yours.

Sigh.

Maybe next year's issue (when i next buy one) will be better.

I am most likely wrong but doesn't the the lectron atomise the fuel better?

I've also wondered if we were to grind the flat into a keihin's needle (and prevent the needle from rotating)
Would it preform similarly

[husaberg]

Not in order sorry

Is there a repository (other than these threads themselves) on Kiwi Biker or anywhere that contains all of the write-ups you and others have put together? I have been trying to compile them for my two-stroke notes collection over the years. I would hate to be missing any.

you click on Neels name and hit view forum posts.

not sure if this link will work
https://www.kiwibiker.co.nz/forums/s...rchid=16464070

I know this is 4T stuff but too much info in there not to ignore. This was posted by a friend of mine on a 4T forum.

Pat Symonds presentation on current F1 engines: https://www.youtube.com/watch?v=mUq-K9jcaB8

Takeaways:

* Thermal Efficiency of 52%
* BSFC 167gms/kw-hr (0.27lbs/hp-hr), occurs at peak power
* 800bhp from 1.6L (then another ~200hp or so from the hybrid unit)
* Lambda 1.3-1.4. Compare that to the DI / spark plug Audi DTM engine which runs at Lambda 1.15-1.38
* Rules limited 18:1 geometric compression ratio. All are at max
* Spark assisted HCCI, which Honda pretty much showed (earlier in the thread)
* They are Miller Cycle engines, with IVC before BDC
* Separate oil circuit for piston oil jets that runs cooler than the other circuits
* Miller Cycle requires very aggressive intake valve opening / closing designs and a lot of boost
* Valve angles low (5-7*), obviously done for squish geometry
* "Omega" piston bowls. Illustration in video helps visualize that
* Modeling from the FIA shows around 5.5bar boost (~80psi or so) and 50% mass fraction burn by 8* ATDC. Lose 1-2% of MFB in the prechamber. Quick combustion from 2-80% MFB and a slowing combustion beyond that. This final 20% with slowing combustion speed is where knock can occur.

I try:

Attachment 350861

Probably needs updating. Any ideas?

https://deltahawk.com/

One of the lead designers is on this forum

I do not know. I only recently understood its workings, thanks to a very kind member that supplied me with pressure traces. The hole size, number and positions are prescribed for the karts in a homologated pipe. So you will have to experiment.

The number/size/position of the holes determine the ratio between the two tuned length pulses.

Have you thought of playing with a pipe that has a perforated rear cone as used by karts? It has two tuned lengths which might help, but it is at the expense of peak power?

It is not the mechanical efficiency I worry about but the thermal one. The manufacturer only characterize it to 1.8bar while Alex wants to run much higher. Just extrapolating the curves to 3bar will already heat the air to well over 300degC if it can reach that and absorb lots of power. Hopefully I am wrong...

I agree, the EngMod2T numbers will not change if the input is the same, the later version gives a lot more data. If the data is not right that was used as input I cannot help.

That is from a very old version of the EngMod2T preprocessor, Dat2T and is probably about 15 years old.

Frits, please feel free to share wherever you like.
I might later fix the grammar error but not now.
And yes, you know exactly who it is aimed at.

There are people in this world that uses an Excel spreadsheet and acoustic theory to create what they claim is a simulator that calculates what your exhaust pipe should look like. They publish this mostly on Farcebook so I thought it would be a good idea to add another installment on gasdynamics. Please give comments so I can improve this.

Attachment 350438

Interesting - I saw the inner radius of the transfer port as the radius on the sleeve side of the port?

He is now discovering why most development is incremental, and even then you can get very lost. Making a paradigm shift is sometimes very challenging.

We are all holding thumbs he finds his way!

Frits, for full clarity of thought Lambda is defined as the AFR/AFRstochiometric, and the "Lambda" measured by the "Lambda sensor" is not a Lambda sensor but a free oxygen sensor and the name "Lambda Sensor" is a misnomer except maybe for when you are measuring a 4T running lean.

Lambda as a concept is fine and should be used to compare mixture strengths. A lambda of 0.85 on avgas ~ AFR 12.46 while a lambda of 0.85 on Q16 ~ AFR 11.33 purely because the stochiometric values are way different, then we are not talking about alcohol fuels.

Or running a lower exhaust port.....

I know this video is on diesel engine emission testing but about a third of the way in they show the crankshaft speed fluctuation in one cycle (well maybe 4 cycles ) and it is what Wobbly and Frits have mentioned a number of times in that in a 2T engine it influences how long the ports stay open:

https://www.youtube.com/watch?v=Yjh_U9LLxY4

After watching the see through carb video something struck me - the unemulsified fuel traveled quite deep into the venturi and the emulsified and evaporated very good. A Lectron must do something similar but even better, the fuel also shoots up into the venturi and is aided by the adhesion to the rear of the needle and is partially protected by the same needle. So it penetrates quite far before being carried away by the air stream. This should give superior atomization and vaporization combined with a more homogeneous mixture distribution early on in the air stream. Should be especially superior in very short intakes.

Based on the dyno curves Frits posted:

1. At start of the powerband the stainless pipe is shifted 250rpm to the right
2. At max power the stainless pipe is shifted 500rpm to the right
3. At 1000rpm above max power rpm the stainless and mild steel pipes have same value.

I suggest you experiment with the prescribed temperatures to match this unless someone has a better idea or better data.

I assume this is with a reedvalve engine?

In what range did you experiment?

I have always wondered about the influence of where the mixture is "stored" in the crankcase. Are you planning tests of this?

Cool info, thanks for sharing.

Maybe:

1. Pipe and engine was not at the correct temperature when dyno run was started; or
2. Acceleration rate on dyno is too fast showing the effect of a longer pipe because the pipe temperature does not heat up fast enough: or
3. ???

A "normal" catalytic converter as on gasoline fueled passenger cars are "three way" catalytic converters requiring stochiometric AFR.

The oxidation catalytic converter is a different type that operates in an excess level of oxygen, typically found on diesel engines.

No extra info, sorry.

This work is done by Lennarth Zander, a Swedish engineer that works at Scania. Even though the video is old, I understand he has resurrected this project and is doing his PhD at Chalmers University of Technology. The interesting thing he does is between the tuned pipe and the turbine he fits an oxidation catalytic converter which reacts with the unburnt oxygen and the fuel and ups the temperature quite a bit to improve the turbine running. The converter works so well he has to control the amount of gas being converted to prevent temperature damage to the turbine.

One of the issues with a turbine after the tuned pipe is the loss of temperature, this reverses that for no extra penalty, the fuel and oxygen is already there.

This is partially how I would do the "Worlds strongest two-stroke".

Supercharging a 2T for performance is not easy and the Aisin AMR300 is a Roots type, not a screw type so very inefficient. Attached is the best map for it I could find. It does not have a high pressure or high rpm rating, and in the top right hand corner is already absorbing over 5kW.

Attachment 349082

I would not go this route, thermodynamics is against you.

He plans to use this:

Attachment 348929

My experience with supercharging a 2T is to NOT charge the crankcase but use external scavenging chamber. You end up doing a double amount of pumping work, first by driving the supercharger and then again by compressing it further in the crankcase, it does not make sense.

You will also need the early closing exhaust port otherwise it just pumps everything into the exhaust. And a tuned pipe does not work unless you only charge a few kPa.

We once shared a pit with an Aprillia factory supported team and it was the first time in my life where I saw them removing pistons after each session and checking the dome height in a special jig. Depending on the amount of collapse of the dome they would either bin it or use it with a different head in the next session. Factory support meant they could buy the special stuff, not getting them free.

Supersonic flow requires a different solving methodology as the waves move in one direction only, as the medium (gas) moves faster than the speed of sound the "rearwards" wave also moves forward because its speed rearwards is less than the gas flow speed. If the numerical method does not do this transition you can get wrong results.

There has been a number of PhD theses in the last few years on the Cd value during sonic flow, it is no longer assumed to be constant. This is very important to 2T engines as the blowdown phase is mostly sonic flow. This is a good area to focus on in my opinion.

This makes me doubt the software as there is nothing there that can cause supersonic flow, and sonic flow will form a shock and jump back to subsonic. The pressure ratio and duct shape required for supersonic flow does not exist in an engine.

"Expanding the Torque Curve of a Two-Stroke Motorcycle Race Engine by Water Injection, Robert Fleck, 931506" presented at the Small Engine Technology Conference in Pisa Italy December 1-3, 1993

Unfortunately I have to agree with this statement. I have wasted thousands of dollars over the last 45 years on papers that disappointed. The older ones were better, maybe because they took pier review seriously. There are some real gems there but buying 20 papers to find 1 good one is not a good return on investment.

Yes, the short circuiting is less than the residual fresh charge in a modern engine, plus a modern engine has a cooled exhaust port duct.

The aim on a modern engine is to plug back into the cylinder only the coldest and purest part of the fresh charge in the exhaust port duct. That way we can prevent detonation and gain power.

Gasdynamics - Issue 2

Please let me know if you disagree, want something explained better etc.

Attachment 348379

Nitro,

That is a truly amazing trace. More so on a 4T engine. I know you do not want to disclose how you achieve it but is there a way we can do an NDA so I can test to see if a sim can duplicate it?

It does seem that there are a number of steep wave fronts in there. Very interesting.

Flow through a pipe, especially unsteady compressible turbulent flow does not behave as we would think. The closest mind picture is that it forms two contra rotating cork screws going through the bend. The following pictures are a simplistic view of the process:

Attachment 348298 Attachment 348299

A better reference is:

https://macsphere.mcmaster.ca/handle/11375/21560

The download is free.

A bend does a very good job of mixing gas. Fuel droplets are not part of the gas and will probably accumulate on the outside of the bend.

One of the things I am not sure about, but suspect about contact discontinuities is that is the difference between a header where the first part is straight compared to one that starts curving immediately from the cylinder interface. It should be obvious that as the gas travels down the pipe the cold and hot gas will mix more and more as it travels down the pipe. A curved pipe where the length the gas has to travel along the inside of the curve is much shorter compared to how far it has to travel along the outside of the curve. This creates a smearing or mixing of the contact discontinuity and lowers its effect.

A strong well defined contact discontinuity formed close to or inside the exhaust port passage seems to be a major advantage. This might be one of the reasons for the Wobbly Exhaust Port. If an engine is not developed for it, it will cause detonation if it is applied to the engine. I think the purpose of Yamaha's "detto button" in their straight pipes on the 500cc GP bike was to smear the contact discontinuity.

Condyn,

Thanks for spotting that, I will fix it in issue 2

The more difficult part to explain is that there is both energy and inertia involved and sometimes amplitude is converted into inertia and sometimes the other way. The differential equations are: 1. conservation of mass, 2. conservation of energy and 3. conservation of momentum. All three must be satisfied at all times. So sometimes you can fool yourself if you just look at pressure amplitude as it is not the full picture. I do not know how to elegantly explain that.

Frits,

I can read that just fine thank you. Seems I follow you by about ten years, in the early 80's I was technical editor for a local magazine, Bike & Track and tried to do similar. I still have a handwritten copy of an article I wrote on blowdown specific time area!

Anyway, let us see what Nitro comments.

Nice discussion Wobbly and Nitro!

As promised, a first attempt at explaining some gasdynamic reflections without using differential equations. Please comment, ask questions etc so I can improve it.

Attachment 348284

Nitro, will do but it will take a few days. I have to put in words what is normally in differential equations in a way that is both still correct and understandable. But it is a good idea to do this.

1. From a wave going through a contact discontinuity - where the composition and or temperature changes
2. Reflection from a shock wave forming
3. A suction wave traveling down a diffuser will reflect a positive wave back
4. ?

Nitro, very good response as per usual.

Ignoring the effect of the closed cycle is not something the sims do though. Attached a pdf I distribute with my software.

Attachment 348178

Some first order results of comparing a Banshee sim with measured traces. Some comments:

1. The sim model is currently a very rough approximation of the real engine and even more so with the pipe, I have no idea what the Toomey T6 looks like.
2. The porting is mostly based on the RZ350 model, until somebody supplies better.
3. I digitized the traces Nitro posted and then used a small amount of smoothing, getting csv files will be better.
4. For some reason I had to shift the inlet trace by 45 degrees to get alignment between the sim and measurement.

Clint,

I am still here, a few times a day!

I do not have a Banshee model, if someone has one or a port map I can create one and run a few sims.

Neels

Biggest issue would be, I think, the piston cam being in the wrong direction, but I am not sure how big this is on small engines.

Ken,

Your calculations is spot on but conservative. A typical crankcase gas temperature for a watercooled but not crankcase cooled racing 2T 125cc making around 45hp is measured around 110degC to 120degC. Anyone that had to emergency strip one of these engines after a race will tell you the crank webs are above boiling point.

The flow through the transfers is highly turbulent and highly unsteady so no boundary layer worth anything has time to form. I find it strange that engine builders like to quote fully developed steady flow boundary layers derived for steady tube flow as being similar to what happens in an engine's ports. They are totally non similar.

https://physics.stackexchange.com/qu...ption-capacity

Boost Charging Duration?

Frits, you are giving me an idea, negative plugging duration will only work with some sort of blower, turbo or super, so what about "Charging duration"?

I use the exhaust piston crankshaft as the master. And a positive phase angle is by how much the exhaust piston crankshaft leads the transfer / inlet crankshaft.

Somewhere in between the TDC values for the two crankshafts is the smallest volume and the effective TDC. If both crankshafts have the same stroke this effective TDC is halfway between the two. The result of all this is you have to find a new optimum timing value, for now I just add half the phase angle to the timing value specified for zero phase angle.

The way the OP2T works is making for interesting findings. Mostly obvious but because I never had the opportunity to vary plugging duration independent from blowdown duration I never thought about it:

1. As we shorten the plugging duration the effect of the plugging pulse becomes less and less. So while on a conventional 2T the blowdown STA is critical, on an OP engine the plugging STA is also critical, depending on whether a tuned pipe or a blower is used.

2. When the plugging duration becomes negative (The duration that still needs a name) the better pipe becomes a megaphone, we only want to extract gas and not plug anything back as the transfers keep flowing and filling the cylinder after exhaust port closure.

Naming of porting events.

Since starting to look at opposed piston engines where the phasing of the crankshafts are possible I have run into a nomenclature problem. On a conventional two-stroke the blowdown duration is the same as the plugging duration. On a phased OP engine you have four options:

• Smaller blowdown than plugging duration,
• Same blowdown and plugging duration,
• Zero plugging duration, and
• Negative plugging duration where the exhaust port closes before the transfer ports.

So what do we call this "negative plugging duration"?
Attachment 347478

Yes, the calculation for the flow area in a T-port takes into account the side wall angles.

The "proposed" power possible or the "suggested" STA values are based on BMEP values. So even though power is shown the calculation is based on the BMEP value.

It assumes very good scavenging and very good delivery ratios and very good trapping efficiency. It is what is possible if everything works as expected.

How about two scavenging plenums around the cylinder, one above the other, each connected to a crankcase by one or two ducts, use the one chamber for swirl flow and the other for column flow?

Lohring, some thoughts:

1. One problem with OP engines is scavenging - swirl causes an unscavenged central column that can even move down towards the scavenging piston,
2. Using opposed transfer ports to clash the flows and causing an upward moving central column leaves and unscavenged outer region,
3. So how about using the one crankcase to feed transfers that causes swirl and the second crankcase to feed transfers that open slightly later to form the central column?

This swirl vs central column is also a problem for standard uniflow engines and is one of the regions where the ship engine builders are putting a lot of research into.

Why not use a toothed belt to connect the two cranks and have one end with a vernier pulley to adjust phase angle?

NASA's attempt:

https://www.techbriefs.com/component...machinery/3135

Lennarth Zander also wrote a nice book " Internal Combustion Engine: Gasexchange and Boosting"

Ceci, I bought that book when it was published, keep in mind it summarizes the research of the late 80's, more than 30 years ago!

Modern electronics, of the last 5 years or so has become a lot cheaper.

NASA's attempt:

https://www.techbriefs.com/component...machinery/3135

Lennarth Zander also wrote a nice book " Internal Combustion Engine: Gasexchange and Boosting"

Maybe on summer holiday - he is from that part of the globe.

Two things:
1. A loop scavenged engine is using tumble - the loop flow by its very nature is the tumble motion, the trick is to control the tumbling speed.
2. OP engine has a serious issue with scavenging, you pretty much have to choose between swirling flow and plug flow or come up with something new.

Swirling flow by its centrifugal motion displaces the fresh charge to the outside and can create a down flowing central column of burn gas, leading to low scavenging efficiencies. There are a large number of publications available on this topic.

Plug flow in an OP engine seems to be a neglected topic.

Neil,

Your YZ250 is mentioned in this video but they do not know what became of it - maybe somebody should put them straight on where TPI comes from?

https://www.youtube.com/watch?v=R1yLUF3aHxQ

NOxes are formed above a certain temperature which is what the squish is trying to avoid, to prevent detonation. This does lead to unburnt hydrocarbons.

With a modern controlled oiling system the low speed smoke can be almost eliminated by supplying the oil required by the load and not just a function of rpm.

NASA's attempt:

https://www.techbriefs.com/component...machinery/3135

Lennarth Zander also wrote a nice book " Internal Combustion Engine: Gasexchange and Boosting"

Maybe on summer holiday - he is from that part of the globe.

Two things:
1. A loop scavenged engine is using tumble - the loop flow by its very nature is the tumble motion, the trick is to control the tumbling speed.
2. OP engine has a serious issue with scavenging, you pretty much have to choose between swirling flow and plug flow or come up with something new.

Swirling flow by its centrifugal motion displaces the fresh charge to the outside and can create a down flowing central column of burn gas, leading to low scavenging efficiencies. There are a large number of publications available on this topic.

Plug flow in an OP engine seems to be a neglected topic.

Neil,

Your YZ250 is mentioned in this video but they do not know what became of it - maybe somebody should put them straight on where TPI comes from?

https://www.youtube.com/watch?v=R1yLUF3aHxQ

NOxes are formed above a certain temperature which is what the squish is trying to avoid, to prevent detonation. This does lead to unburnt hydrocarbons.

With a modern controlled oiling system the low speed smoke can be almost eliminated by supplying the oil required by the load and not just a function of rpm.

The "proposed" power possible or the "suggested" STA values are based on BMEP values. So even though power is shown the calculation is based on the BMEP value.

It assumes very good scavenging and very good delivery ratios and very good trapping efficiency. It is what is possible if everything works as expected.

I do not have a model of the KX65, closest I have is KX85.

Hi Condyn,

I try to make the Help files as descriptive as possible with guidance without being prescriptive. Plus there are extra documents available for specific topics, if you get stuck just ask.

The software is 1-dimensional so some aspects like in-cylinder flow is modeled using a quasi-dimensional approach and not full 3D. Full 3D will increase the price at least 10 times and the run duration a 100 times. So there are some limitations.

Neels

The ones in post #18 still works.

One of the things I am not sure about, but suspect about contact discontinuities is that is the difference between a header where the first part is straight compared to one that starts curving immediately from the cylinder interface. It should be obvious that as the gas travels down the pipe the cold and hot gas will mix more and more as it travels down the pipe. A curved pipe where the length the gas has to travel along the inside of the curve is much shorter compared to how far it has to travel along the outside of the curve. This creates a smearing or mixing of the contact discontinuity and lowers its effect.

A strong well defined contact discontinuity formed close to or inside the exhaust port passage seems to be a major advantage. This might be one of the reasons for the Wobbly Exhaust Port. If an engine is not developed for it, it will cause detonation if it is applied to the engine. I think the purpose of Yamaha's "detto button" in their straight pipes on the 500cc GP bike was to smear the contact discontinuity.

Condyn,

Thanks for spotting that, I will fix it in issue 2

The more difficult part to explain is that there is both energy and inertia involved and sometimes amplitude is converted into inertia and sometimes the other way. The differential equations are: 1. conservation of mass, 2. conservation of energy and 3. conservation of momentum. All three must be satisfied at all times. So sometimes you can fool yourself if you just look at pressure amplitude as it is not the full picture. I do not know how to elegantly explain that.

Frits,

I can read that just fine thank you. Seems I follow you by about ten years, in the early 80's I was technical editor for a local magazine, Bike & Track and tried to do similar. I still have a handwritten copy of an article I wrote on blowdown specific time area!

Anyway, let us see what Nitro comments.

Nice discussion Wobbly and Nitro!

As promised, a first attempt at explaining some gasdynamic reflections without using differential equations. Please comment, ask questions etc so I can improve it.

Attachment 348284

Nitro, will do but it will take a few days. I have to put in words what is normally in differential equations in a way that is both still correct and understandable. But it is a good idea to do this.

1. From a wave going through a contact discontinuity - where the composition and or temperature changes
2. Reflection from a shock wave forming
3. A suction wave traveling down a diffuser will reflect a positive wave back
4. ?

Nitro, very good response as per usual.

Ignoring the effect of the closed cycle is not something the sims do though. Attached a pdf I distribute with my software.

Attachment 348178

Some first order results of comparing a Banshee sim with measured traces. Some comments:

1. The sim model is currently a very rough approximation of the real engine and even more so with the pipe, I have no idea what the Toomey T6 looks like.
2. The porting is mostly based on the RZ350 model, until somebody supplies better.
3. I digitized the traces Nitro posted and then used a small amount of smoothing, getting csv files will be better.
4. For some reason I had to shift the inlet trace by 45 degrees to get alignment between the sim and measurement.

Clint,

I am still here, a few times a day!

I do not have a Banshee model, if someone has one or a port map I can create one and run a few sims.

Neels

Biggest issue would be, I think, the piston cam being in the wrong direction, but I am not sure how big this is on small engines.

Ken,

Your calculations is spot on but conservative. A typical crankcase gas temperature for a watercooled but not crankcase cooled racing 2T 125cc making around 45hp is measured around 110degC to 120degC. Anyone that had to emergency strip one of these engines after a race will tell you the crank webs are above boiling point.

The flow through the transfers is highly turbulent and highly unsteady so no boundary layer worth anything has time to form. I find it strange that engine builders like to quote fully developed steady flow boundary layers derived for steady tube flow as being similar to what happens in an engine's ports. They are totally non similar.

https://physics.stackexchange.com/qu...ption-capacity

Boost Charging Duration?

Frits, you are giving me an idea, negative plugging duration will only work with some sort of blower, turbo or super, so what about "Charging duration"?

I use the exhaust piston crankshaft as the master. And a positive phase angle is by how much the exhaust piston crankshaft leads the transfer / inlet crankshaft.

Somewhere in between the TDC values for the two crankshafts is the smallest volume and the effective TDC. If both crankshafts have the same stroke this effective TDC is halfway between the two. The result of all this is you have to find a new optimum timing value, for now I just add half the phase angle to the timing value specified for zero phase angle.

The way the OP2T works is making for interesting findings. Mostly obvious but because I never had the opportunity to vary plugging duration independent from blowdown duration I never thought about it:

1. As we shorten the plugging duration the effect of the plugging pulse becomes less and less. So while on a conventional 2T the blowdown STA is critical, on an OP engine the plugging STA is also critical, depending on whether a tuned pipe or a blower is used.

2. When the plugging duration becomes negative (The duration that still needs a name) the better pipe becomes a megaphone, we only want to extract gas and not plug anything back as the transfers keep flowing and filling the cylinder after exhaust port closure.

Naming of porting events.

Since starting to look at opposed piston engines where the phasing of the crankshafts are possible I have run into a nomenclature problem. On a conventional two-stroke the blowdown duration is the same as the plugging duration. On a phased OP engine you have four options:

• Smaller blowdown than plugging duration,
• Same blowdown and plugging duration,
• Zero plugging duration, and
• Negative plugging duration where the exhaust port closes before the transfer ports.

So what do we call this "negative plugging duration"?
Attachment 347478

Yes, the calculation for the flow area in a T-port takes into account the side wall angles.

I know a lot do not follow the 50cc pages on Pitlane but there are some very interesting threads, in English!

http://www.pit-lane.biz/t8449-dtt-gp50#442165

http://www.pit-lane.biz/t6610-50cc-p...d-ktm50-tuning

I must still work my way through the thesis, its name is in the name of the picture, do a search and download it.

I have no idea, I assume it is a shadow as it does not show up anywhere else in the thesis.

Frits, maybe this is of interest?

Attachment 346442

Hydrogen is not dead:

https://www.h2-view.com/story/hyunda...o-switzerland/

For those interested in turbocharging a 2T:

https://www.snowmobile.com/trails/po...e-engine-65385

It seems Polaris has filed for 9 patents.

The difference between the traditional stepped piston and the new generation versions is that they no longer use the crankcase but the "scavenging" chamber between the piston and the seal to the crankcase.

Here is his idea, just with the "mushroom" piston the other way round and loop scavenging in place of Uniflow scavenging:

http://www.ac-aero.com/technologies/

Yes, from the homologation papers it seems that its pumping chamber has only 55% of the engine displacement, so unless they discovered a way to more than double the suction of the pipe it was only good for mid 30s hp. Which seems to correspond to dyno figures Jan has heard. I think we will not hear any more from the Ryger crowd.

I asked him what is different from the Ryger concept but did not get a real answer.

https://deltahawk.com/content/deltahawk-dh180a4

WilDun, I disagree that we are too blind. We just do not post about it here. The engine in the attached link was originally developed with my software that can simulate it quite well. The last phase of development they are using GT/Power because it includes the mechanical design portion.

The work Neil is doing is also moving away from tuned pipes, and in his line of opposed piston engines with or without uniflow scavenging there are a lot of research and development happening, once again, just not posted here.

I would also like the comment explained. A high performance conventional 2T with or without a turbo must still follow the general "rules" of having enough blowdown and strong suction and plugging pulses, otherwise you just blow all the boost out during exhaust port closure.

Lohring, I have a number of photos of that sled but no info on it running. Do you know more?

Neels

The best way to look at a turbo is to consider it a device that increases atmospheric pressure. Then all the requirements at 1 atmosphere are still there at higher atmospheres.

It stays a 2T so you still need blowdown, and a plugging pulse. Because of the extra power you can go for a milder tune if power spread is required but the snowmobile drag sleds use very high levels of tune.

If you do not want to use a tuned pipe you have to go for a Uniflow engine.

You do know Suzuki used to do this on their triples in the early 70's?

https://www.autoevolution.com/news/t...85.html#agal_0

Hi Husa,

Thank you, but I am aware of the facility. It is one of my daily pleasures to come to KiwiBiker first thing in the morning and see what was posted while I was sleeping. My "gripe" was not with comming here but with finding nothing

And I will keep on doing it.

Good! I have been coming here and to the Speeduino blog almost daily to look for progress!!!

How about two scavenging plenums around the cylinder, one above the other, each connected to a crankcase by one or two ducts, use the one chamber for swirl flow and the other for column flow?

Lohring, some thoughts:

1. One problem with OP engines is scavenging - swirl causes an unscavenged central column that can even move down towards the scavenging piston,
2. Using opposed transfer ports to clash the flows and causing an upward moving central column leaves and unscavenged outer region,
3. So how about using the one crankcase to feed transfers that causes swirl and the second crankcase to feed transfers that open slightly later to form the central column?

This swirl vs central column is also a problem for standard uniflow engines and is one of the regions where the ship engine builders are putting a lot of research into.

Why not use a toothed belt to connect the two cranks and have one end with a vernier pulley to adjust phase angle?

Obsessive Compulsive Disorder (OCD) the "nice way of saying somebody is anal about detail

https://www.autoevolution.com/news/t...85.html#agal_0

Hi Husa,

Thank you, but I am aware of the facility. It is one of my daily pleasures to come to KiwiBiker first thing in the morning and see what was posted while I was sleeping. My "gripe" was not with comming here but with finding nothing

And I will keep on doing it.

Good! I have been coming here and to the Speeduino blog almost daily to look for progress!!!

It it wasn't for the impressive and neat things Rob is doing we would not be able to have this discussion.

The automotive engineering world use terminology that if you are unfamiliar with it you can miss important publications, maybe it is well known but was strange to me:

Throttle opening: Tipp-in
Throttle closing: Tipp-out

I am no expert on this but would expect both throttle position and later also rate of throttle change to be part of the control loop.

This is just so great!

I was wondering in your calculation of the MAP values (I think it was (Phigh-Plow)*3) whether you should not maybe add an atmospheric based Patm to your equation? Maybe you are planning it but for now it is not an issue.

I understand what you are trying to do but would have started with a full high performance super fast system and then worked at simplifying (less expensive) it rather than trying from the less complex side, adding more and more complexity and maybe missing something. But all in all a very worthwhile and noteworthy effort.

I have been following what you are doing here and on the Speeduino forum and are beginning to think you need to sample at a much higher rate, like two times per degree at max rpm and have a very fast processor to do some signal conditioning before using it. We often find the signal to noise ratio with pressure signals very bad where the noise has a 3 or more times bigger amplitude than the pressure amplitude. But not my area of expertice!

One of the things I am not sure about, but suspect about contact discontinuities is that is the difference between a header where the first part is straight compared to one that starts curving immediately from the cylinder interface. It should be obvious that as the gas travels down the pipe the cold and hot gas will mix more and more as it travels down the pipe. A curved pipe where the length the gas has to travel along the inside of the curve is much shorter compared to how far it has to travel along the outside of the curve. This creates a smearing or mixing of the contact discontinuity and lowers its effect.

A strong well defined contact discontinuity formed close to or inside the exhaust port passage seems to be a major advantage. This might be one of the reasons for the Wobbly Exhaust Port. If an engine is not developed for it, it will cause detonation if it is applied to the engine. I think the purpose of Yamaha's "detto button" in their straight pipes on the 500cc GP bike was to smear the contact discontinuity.

Condyn,

Thanks for spotting that, I will fix it in issue 2

The more difficult part to explain is that there is both energy and inertia involved and sometimes amplitude is converted into inertia and sometimes the other way. The differential equations are: 1. conservation of mass, 2. conservation of energy and 3. conservation of momentum. All three must be satisfied at all times. So sometimes you can fool yourself if you just look at pressure amplitude as it is not the full picture. I do not know how to elegantly explain that.

Frits,

I can read that just fine thank you. Seems I follow you by about ten years, in the early 80's I was technical editor for a local magazine, Bike & Track and tried to do similar. I still have a handwritten copy of an article I wrote on blowdown specific time area!

Anyway, let us see what Nitro comments.

Nice discussion Wobbly and Nitro!

As promised, a first attempt at explaining some gasdynamic reflections without using differential equations. Please comment, ask questions etc so I can improve it.

Attachment 348284

Nitro, will do but it will take a few days. I have to put in words what is normally in differential equations in a way that is both still correct and understandable. But it is a good idea to do this.

1. From a wave going through a contact discontinuity - where the composition and or temperature changes
2. Reflection from a shock wave forming
3. A suction wave traveling down a diffuser will reflect a positive wave back
4. ?

Nitro, very good response as per usual.

Ignoring the effect of the closed cycle is not something the sims do though. Attached a pdf I distribute with my software.

Attachment 348178

Some first order results of comparing a Banshee sim with measured traces. Some comments:

1. The sim model is currently a very rough approximation of the real engine and even more so with the pipe, I have no idea what the Toomey T6 looks like.
2. The porting is mostly based on the RZ350 model, until somebody supplies better.
3. I digitized the traces Nitro posted and then used a small amount of smoothing, getting csv files will be better.
4. For some reason I had to shift the inlet trace by 45 degrees to get alignment between the sim and measurement.

Clint,

I am still here, a few times a day!

I do not have a Banshee model, if someone has one or a port map I can create one and run a few sims.

Neels

Biggest issue would be, I think, the piston cam being in the wrong direction, but I am not sure how big this is on small engines.

Ken,

Your calculations is spot on but conservative. A typical crankcase gas temperature for a watercooled but not crankcase cooled racing 2T 125cc making around 45hp is measured around 110degC to 120degC. Anyone that had to emergency strip one of these engines after a race will tell you the crank webs are above boiling point.

The flow through the transfers is highly turbulent and highly unsteady so no boundary layer worth anything has time to form. I find it strange that engine builders like to quote fully developed steady flow boundary layers derived for steady tube flow as being similar to what happens in an engine's ports. They are totally non similar.

https://physics.stackexchange.com/qu...ption-capacity

Boost Charging Duration?

Frits, you are giving me an idea, negative plugging duration will only work with some sort of blower, turbo or super, so what about "Charging duration"?

I use the exhaust piston crankshaft as the master. And a positive phase angle is by how much the exhaust piston crankshaft leads the transfer / inlet crankshaft.

Somewhere in between the TDC values for the two crankshafts is the smallest volume and the effective TDC. If both crankshafts have the same stroke this effective TDC is halfway between the two. The result of all this is you have to find a new optimum timing value, for now I just add half the phase angle to the timing value specified for zero phase angle.

The way the OP2T works is making for interesting findings. Mostly obvious but because I never had the opportunity to vary plugging duration independent from blowdown duration I never thought about it:

1. As we shorten the plugging duration the effect of the plugging pulse becomes less and less. So while on a conventional 2T the blowdown STA is critical, on an OP engine the plugging STA is also critical, depending on whether a tuned pipe or a blower is used.

2. When the plugging duration becomes negative (The duration that still needs a name) the better pipe becomes a megaphone, we only want to extract gas and not plug anything back as the transfers keep flowing and filling the cylinder after exhaust port closure.

Naming of porting events.

Since starting to look at opposed piston engines where the phasing of the crankshafts are possible I have run into a nomenclature problem. On a conventional two-stroke the blowdown duration is the same as the plugging duration. On a phased OP engine you have four options:

• Smaller blowdown than plugging duration,
• Same blowdown and plugging duration,
• Zero plugging duration, and
• Negative plugging duration where the exhaust port closes before the transfer ports.

So what do we call this "negative plugging duration"?
Attachment 347478

Yes, the calculation for the flow area in a T-port takes into account the side wall angles.

I know a lot do not follow the 50cc pages on Pitlane but there are some very interesting threads, in English!

http://www.pit-lane.biz/t8449-dtt-gp50#442165

http://www.pit-lane.biz/t6610-50cc-p...d-ktm50-tuning

I must still work my way through the thesis, its name is in the name of the picture, do a search and download it.

I have no idea, I assume it is a shadow as it does not show up anywhere else in the thesis.

Frits, maybe this is of interest?

Attachment 346442

Hydrogen is not dead:

https://www.h2-view.com/story/hyunda...o-switzerland/

For those interested in turbocharging a 2T:

https://www.snowmobile.com/trails/po...e-engine-65385

It seems Polaris has filed for 9 patents.

The difference between the traditional stepped piston and the new generation versions is that they no longer use the crankcase but the "scavenging" chamber between the piston and the seal to the crankcase.

Here is his idea, just with the "mushroom" piston the other way round and loop scavenging in place of Uniflow scavenging:

http://www.ac-aero.com/technologies/

Yes, from the homologation papers it seems that its pumping chamber has only 55% of the engine displacement, so unless they discovered a way to more than double the suction of the pipe it was only good for mid 30s hp. Which seems to correspond to dyno figures Jan has heard. I think we will not hear any more from the Ryger crowd.

I asked him what is different from the Ryger concept but did not get a real answer.

https://deltahawk.com/content/deltahawk-dh180a4

WilDun, I disagree that we are too blind. We just do not post about it here. The engine in the attached link was originally developed with my software that can simulate it quite well. The last phase of development they are using GT/Power because it includes the mechanical design portion.

The work Neil is doing is also moving away from tuned pipes, and in his line of opposed piston engines with or without uniflow scavenging there are a lot of research and development happening, once again, just not posted here.

I would also like the comment explained. A high performance conventional 2T with or without a turbo must still follow the general "rules" of having enough blowdown and strong suction and plugging pulses, otherwise you just blow all the boost out during exhaust port closure.

Lohring, I have a number of photos of that sled but no info on it running. Do you know more?

Neels

The best way to look at a turbo is to consider it a device that increases atmospheric pressure. Then all the requirements at 1 atmosphere are still there at higher atmospheres.

It stays a 2T so you still need blowdown, and a plugging pulse. Because of the extra power you can go for a milder tune if power spread is required but the snowmobile drag sleds use very high levels of tune.

If you do not want to use a tuned pipe you have to go for a Uniflow engine.

You do know Suzuki used to do this on their triples in the early 70's?

I have to admit though that in 2000 he was not that far wrong - at that stage I still had to convince a certain Wobbly to stop using Dynomation2T and work with me, something I somehow got right.

And this Great Leader is now going to put Fantic straight:

https://www.motocrossplanet.nl/nieuw...-de-motorcross

Thank you!

Does anyone have the crankcase volume or primary compression ratio for a Maico 440? And is it inclusive or exclusive of the transfer port passage volumes?

TZ that seems a very difficult way - we take a top head, cut off the outlet, weld the hole closed and add the inlet to the side.

When the piston is moving upwards the space below it that it vacates is where the gas has to flow to. Most of it comes from the inlet so to minimize losses the inlet should be aimed at this space.

Secondary flow into this space also comes out of the crankcase and transfer passages. We want to minimize this last one and one way to do this is to lower the primary compression ratio - one often forgotten secondary effect of large case volumes. Often the side effect of the Boyesen ports is just that, rather than flow out of the transfer passages the flow is out of the inlet cavity which promotes reed opening.

No, it is something that is planned but it will have to follow making the software parallel processing, otherwise it will run for weeks.

That is like asking why the optimum is the optimum, I will try:

Our current understanding of the inlet, scavenging, exhaust duct shape and pumping optimums lead us to an engine with a certain type of port layout and size (mostly derived from Jan's work on the RSA125), and this layout requires specific suction and plugging pulses from the pipe with a specific phasing and strength to make it all work together. This basic exhaust layout gives you that.

For a less than optimum engine, for instance the TM KZ10C which has a fixed timing curve prescribed by the rules, we see some deviations from this "optimum" shape, to compensate for the less than optimum condition. I am sure that as scavenging, selective cooling, exhaust ducts etc develops further this optimum shape will drift to a new shape.

Does this answer your question?

DutchPower, I do not fully understand your question:

1. Do you ask why, after a number of simulation runs and development, the best pipe looks like the picture,
2. Or do you ask why Dat2T always gives the same starting pipe?

Michael,

Why do you not just make a closer ratio 5th gear? That is what we used to do years ago on another project.

If I remember correctly, Martin Wimmer on his TZ250N, back in '85 ran a transmission oilcooler in an effort to cool the crankcases. I think it was done by Helmut Fath.

Buongiorno Wobbly, come stai?

And the best for the new year to all.

Create a pack file, send it to me with an explanation of the error and I will fix it. It is part of the standard service when purchasing the software.

The "proposed" power possible or the "suggested" STA values are based on BMEP values. So even though power is shown the calculation is based on the BMEP value.

It assumes very good scavenging and very good delivery ratios and very good trapping efficiency. It is what is possible if everything works as expected.

I do not have a model of the KX65, closest I have is KX85.

Hi Condyn,

I try to make the Help files as descriptive as possible with guidance without being prescriptive. Plus there are extra documents available for specific topics, if you get stuck just ask.

The software is 1-dimensional so some aspects like in-cylinder flow is modeled using a quasi-dimensional approach and not full 3D. Full 3D will increase the price at least 10 times and the run duration a 100 times. So there are some limitations.

Neels

The trends are correct, with E85 creating more cooling which allows more compression. More cooling plus more compression will increase the power and move the whole curve to the left as is happening. While the trends are correct the magnitude is a bit suspect. I am suspecting the evaporation model and will investigate that further, it is not very sophisticated and might over predict the cooling.

Is there anyone with actual measured performance and temperature data for a high performance 2T that is willing to share?

Derek,

Absolutely - transfer port and crankcase cooling gives measurable gains.

I am adding the detonation feature for E0~E100 in EngMod2T, I will then have a better idea.

I have no experience with either clean ethanol or with it blended with gasoline. My experience is limited to methanol. But some pointers:

The biggest increase in power comes from the much bigger latent heat of evaporation (Gasoline~305kJ/kg, E85~836kJ/kg) and that causes two good things:

1. The incoming charge density is increased by cooling it down during evaporation
2. The temperature of the mixture in the cylinder at the start of compression is much less, leading to a lower maximum unburnt temperature during combustion and an effective anti-detonation result.

E85 is used extensively by the drifter crowd as a detonation combatant when running high boost pressures.
In a 2T engine we can increase the compression ratio quite a lot - clean ethanol has an effective octane number of 109.

Currently there is no detonation checking for Ethanol or E0 to E100 built into EngMod2T, it is being rectified. We should verify this before analyzing the results.

Released some small bug fixes today.

Released an update. If you did not receive notification let me know please. Spam filters are overactive sometimes.

Summary of Major Updates to 2T Suite
9 August 2019

There has been some major updates to the software since the last official release. Twice in the last 6 months a new release was just about ready before being interrupted by either refinements or additional functionality.

• Short Summary of Major Updates:
• Updated pipe junction model
• Updated turbocharger and supercharger model
• Adding an opposed piston two crankshaft option
• Adding a tandem twin engine
• New Uniflow scavenging model and dialog box
• First version of poppet exhaust valve to model a Uniflow engine
• Extra output in the power output file, this will automatically create a new power file
• More options in the compression ignition model
• An ignition curve generator was added, use with caution! It is only meant to get started
• General small bug fixes and improved robustness

Read the detailed description of the new pipe junction model in Dat2T Help first before using it. It is quite different. The old one will still work though. This is applicable for 3-pipe junctions as used in ATAC, boost bottles, wastegates, T-pipes and internal stingers.

The first time a full run is done on an existing model with the older version power output file the older version will be renamed and will still be available for opening in Post2T while a new one with the extra headers will be created.

The poppet valve addition is not yet complete so only the generated lift profile is active, VVT, imported lift profile and flow bench created Cd maps are not yet working. They will be added over the next few months.

It is no longer possible to test all available combinations or permutations so please report any issues!

Found an old one. Is this ok or do you need it updated?

Attachment 339286

I am no expert on this but would expect both throttle position and later also rate of throttle change to be part of the control loop.

I have just released an update. Make sure you received the update links.

Next I will see about creating a blank document for manual completion when measuring.

Are you asking for something similar to the 4T version?

Attachment 339193

I posted more small error fixes today, if you did not get the notification please email me.

It also adds a contra rotating crank engine layout option.

Yes, I have and plan to also add basic catalytic converters sometime in the future.

Currently I am working on a duct element that can simulate the increase in flow volume and the dropm in temperature as the result of NOX injection.

I am working on a utility to show a schematic of the transfer port passages as many still get it wrong. Below a picture of where I got to over the weekend. It must still be corrected to use the same horizontal and vertical scales. Anything I should add? Any other ideas?

Attachment 335784

Yes, but already halfway there, the PV graph has it by default.

Juergen,

Was that with prescribed or turbulent combustion? With both there were small error fixes in correcting mass preservation issues.

Neels

I posted small error fixes today, contact me please if you are a license holder and did not get the notification.

This bike had its engine designed by Wobbly using EngMod2T.

Attachment 335486

It is there - choose methanol as base fuel with the right nitro ratio - have used up to 94% on 4T simulations. Make sure you are much richer than stochiometric.

I have no idea what you are simulating or what you used before. Were you getting the same max unburnt air temperatures without detonation or has the max unburnt air temperatures increased?

Ief,

The moment EngMod2T hangs (holed a piston?) please pack the project and send me the pack file with a brief description to explain what happens.

The turbulent model is not an analytical model but a statistical model combined with some physics so it will not work for all engines in all cases (as it says in the help files) but as more engines are modeled with it and more results become available it improves. Problem is improving it breaks it for some cases. Sometimes hand editing of the file created by Post2T is required.

Vannik

Wallace,

I only found it about a year ago and are thinking along the same lines as you,to send a link to all the licensed users of EngMod2T.

Cheers
Neels

TZ350,

Could you please either measure or post a section through the export above the transfers so we can get the angle of the expassage similar to this one that is next to the transfer ports?

Attachment 339151

1.0 is 100% pure air,
0.0 is 100% burnt gas.

The software gives you the purity at the entrance and exit of each transfer passage as well as the purity in the crankcase and inlet port.

When you have faced it and taken a new pic - would there be a chance to use it in Dat2T Help files?

Can that be because the photo is not in line with the bore center line?

EngMod2T has no problem simulating it. It is a 2into1 with funny joint angles.

Attachment 336498

And area times distance is volume? I think the issue is to get the required length of small cross sectional area. Too much is maybe less damaging than too little?
Port volume is a very important parameter in the 4T world.

I was thinking along those same lines - are we equally wild?

There are a number of issues that come into play with the exhaust port window and passage shape and its interaction with the pipe:

1. To maximize outflow during blowdown we want the flow to stay attached to the roof and currently the best solution seems to be the Frits radius and Jan's 25° roof angle.
2. Then we want to minimize the mixing of the fresh gas that escapes with the burnt gas to have the purest fresh gas pushed back into the cylinder during the plugging phase. To do this we want to minimize the interface area between the two gasses which requires a small cross sectional area which leads to the small effective duct diameter (currently about 75% of the total window area for a tripple port) and we want to minimize the turbulence caused by separated flow, we already have the roof down at 25° so the other area is to add a hump in the floor to allow the flow to attach.
3. We do not just want the plugging pulse slug of gas to be as pure as possible, we also want to have the maximum mass pugged back in and to help that we need to maximize its density. To do this we want to cool the duct walls as much as possible but only for the required distance to keep the plug of gas cold and not more as that removes unnecessary energy from the pipe and add it to the cooling system.
4. Next we want to have the best flow into the cylinder from the plugging pulse so we are looking at attached flow to the roof and floor which our previous down angle roof and ski-jump floor gives us. The issue is the sides on a tripple port layout. The way is not clear yet although Jan has stated that shortening the divider improves the power and Wobbly is busy experimenting in this area.
5. A final issue on the gasdynamic side - the boundary between two gasses of different composition or of different temperature is known as a "contact discontinuity" and when a wave travels through it it changes shape. This is quite a dramatic effect that plays a major role in how a high performance pipe works. For those of you with Blair's two stroke or four stroke book there are experimental results shown in chapter 2 that is quite enlightening. If you simulate a pipe and ignore this issue the results are very different. Any empirical formulas ignore this effect which is why they get you close but never exact. There is no magic formula. To get back to the topic, the exaust port duct that is developed according the preceding points also increases the size and definition of the major contact discontinuity at the duct and through this greatly influences the working of the pipe. Fortunately it improves it.

Do not confuse the sterling work of Sietse and Gerard with Luc's calculation, if you have an issue with one do not also make the other off as the same. My reading Dutch is not so good but it seems in the first post on the topic they measured on a Tovami dyno 31.9hp at 13200rpm, it made more at higher rpm but starts wheel spinning.

The flow conditions are not the same - on the V8 inter-cylinder air stealing is a major issue and one of the reasons for the small radius.

It was removed on request - I can add it again.

Where I work a "simulant" is a block of TNT, the mass of which determines the size of the mine it simulates, so quite an explosive situation.

I am open to a better word that will work as a single and have a plural

Attachment 335037

How a sim handles blowdown and pretty much all porting:

1. A sim does not predict how much of anything you need, it tells you how well what you have will work,

2. It is not a design tool as such, although there is usually some guidance and design aids in the preprocessor that is used to construct the model,

3. A sim calculates all the flows, purities, temperatures, pressures and densities in all the ducts, boxes, plenums, cylinders and crankcases as the crank rotates. It cannot do this in one continuous calculation but it does it in small increments, typically less than 1 crank degree. At each increment it calculates all the open areas of all the ports and the flow through that port during that time step as a function of all the thermodynamic conditions at that time step. It also calculates the flow and pressure wave movement in all the ducts in that time step. Then it sums all the flows in and out of each plenum, cylinder and crankcase to determine the new states in each as the starting value for the next step.

4. At the end of each revolution it calculates the power, torque, delivery ratios etc for that revolution.

So the sim will not tell you if you have to little or too much time.area of anything, it will just predict less power than what you would get if it was correct and it is up to the simulatee to use his knowledge and all the outputs from the sim to figure out what next.

I did the same on a NSR250 used for racing but also built the valve halves up with brazing and filed them to get a much better fit with smaller pockets and hopefully better flow. Well, it seemed to work well, the bike dominated the championship.

Win XP and newer. I cannot test on older so do not know. 32bit and 64bit.

If you are talking about a non-tuned pipe it is possible to make a good common exhaust, also if you have just two quarter wave straight pipes terminating in a common box will work. But this will be for a specific speed and for an UAV type engine where mass and space is a big issue. The UAV engines I worked on (Zanzottera and Limbach) had either a stub exhaust which was very noisy or two quarter wave pipes with absorption silencer included which was less noisy. You have to decide what is best for your application.

https://www.kiwibiker.co.nz/forums/s...gMod2T-Q-amp-A

Jeff,
You need the latest version, I sent out update notification yesterday. If you did not get it let me know. The notification is via bulk email with links which gets blocked by some firewalls.
Vannik

I am constantly surprised to see how few people know about Google Advanced Search https://www.google.com/advanced_search which does it all for you.

sae 2004-01-3561

I thought it a good idea to investigate the size of the piston side thrust force (N) in a normal 125cc engine with different conrod lengths. The attached picture shows those forces for a conventional 125cc engine and in each case the power and combustion pressure was the same. I cannot do this for the Ryger as I do not know the pressure history in the combustion chamber:

Attachment 331856

How high is high? There is quite a large chamber at the bottom of the cylinder, almost all the way around that is part of the bottom compression chamber. At least that is how it looks in the homoligation papers and in the patent papers.

Luc I still hope it will come to something. And in this case I do not know what it is that I do not know.

Jan is correct, I did a simulation of what I think a Ryger engine looks like. In the simulation I assumed good scavenging and good normal combustion. The layout is a stepped piston with the step smaller than the main piston, unlike the traditional stepped pistons where it is bigger than the main piston. The rest is just gas-dynamics and plenums. If this is close to the Ryger in its current format I do not know.

Attachment 331683

Katinas,

In simulation of what I think the Ryger is it seems to need a much stiffer reed valve petal. Typically 0.20 to 0.25mm thicker than what is typical for a 125cc engine (0.40mm glass fiber), so use 0.60 to 0.65mm. Just a suggestion. And it does not seem sensitive to a tuned pipe.

Vannik

One part of the article.

Attachment 330586

The turbulence is caused by the breakdown of the main flow. Because of the viscosity (in effect the internal friction of the fluid) the main flow progressively break down into ever smaller eddies and if left long enough all the main flow and all the eddies will stop. The main flow is from the transfer port loop and a stronger better directed flow with more kinetic energy can generate a lot of turbulence before it stops. If you have weak flow by the time combustion happens you need the extra flow from the squish to generate extra turbulence to get good combustion. On the other side if you have strong flow and thus good turbulence the extra turbulence can speed up the combustion too much and you loose power but mostly overrev. This explains why engines do not always behave the same to squish changes. Good engines use squish to minimize end gas to stop detonation while poor engines use squish to add turbulence.

So to answer the question: Turbulence cannot reverse, it is a one way street after creation. The bulk flow with the squish opening will loop slower and slower, both because of the increase in volume and because it keeps generating turbulence until it completely stops.

I updated my software to simulate stepped pistons, both ways, the traditional bigger bottom step and the Ryger smaller step, and I have tried many ways without ever exceeding 30hp on the Ryger. Maybe I am missing something....

Ryger Question:

The displacement in the chamber below the piston is roughly half the cylinder displacement - thus the pumped volume is about 70cc in a 125cc engine. So relying on pumping only at theoretical best we can only get a delivery ratio of 50% (Aprillia RSA125 ~ 140%) so where does the rest of the charge come from?

You would need some super pipe to create this sort of suction to make up the difference and that is just to match the RSA125, but the Ryger is supposed to be relatively insensitive to pipe design so not this?

The inertia of the gas flowing through the ports can help a small amount but nowhere near this difference.

Please feel free to ask anything you like on this forum - there are enough experts to help you and it shows me where to improve!

Gentlemen,

Nitro2tfx is way too modest - he produces and sells some of the best and best value for money engine measuring equipment. Have a look at:

http://tfxengine.com/index.html

I thought it would make for interesting results doing a Wobbly exhaust port duct on a very high performance engine - something much better than the best HRC could do. So what better to use an Aprillia RSW125 as developed by Jan Thiel?

It makes for interesting results:

Attachment 318565

[F5 Dave]

Page 2461. Half of them husi.

[husaberg]

Page 2461. Half of them husi.

Pg 2461 should be all of them

[jonny quest]

KTM has abandoned the TPI. New models have injectors in reed cage or TB I believe.

Now the race models, not just Enduro models of 2 strokes will feature EFI.

They have a sensor in crankcase

[TZ350]

.
Two Stroke stuffings dyno looks more stable:- https://youtu.be/1IZSBuhn26A



20hp but no were near getting the best from the engine yet.

[husaberg]

KTM has abandoned the TPI. New models have injectors in reed cage or TB I believe.

Now the race models, not just Enduro models of 2 strokes will feature EFI.

They have a sensor in crankcase

Flettners injecting direct into the header pipe now and has been for ages, KTM will by co-incidence be there in a few years

[Orengo98]

Here is a different supercharger approach to Alex on a 2 stroke. https://youtu.be/u3UFuCxZ6zs

Hi all!

My name is Joan, I'm an engineering student from Barcelona. I've been reading the full thread and following it since the last year, and It's an amazing thread full of knowledge and ideas!

Talking about supercharging approaches for two strokes that use the crankcase to breath, Montesa in 1983, developed a system, that used a piston compressor, connected to the crankshaft. Articles of the era said that the device increased torque by a huge amount. This didn't reach production and was only used in a few prototypes, a trial version and an enduro version, both with expansion chambers.

I don't know how effective the system was, I think that the piston compressor is going the increase a lot the temperature of the air-fuel entering the cylinder. Another think is that looking at the diagram, the volume ratio seems to be 1:1. Both cylinders have the same common stroke, and by measuring the bore, the same bore. The only back pressure that helps to reduce short-circuiting is the expansion chamber pulses.

Also, looking at the diagram, seems that the compressor is at BDC while the piston it's at the middle of stroke. Would be interesting to see the effect that those two pistons at 90º have on the volume of the crankcase.

[Norman]

///
Would be interesting to see the effect that those two pistons at 90º have on the volume of the crankcase.

[/QUOTE]
///

Hi Joan,
In case you do not have it already, you can read about it in the below SAE paper. If you cannot get it through university, try and register on JSTOR portal and you might find it there to read online. BTW, Sometimes "PrtScn" button is useful.

1985-02-01
Two-Stroke Cycle Engine with Flow Induction Corrected at the Intake and Transfer Phases 850184
The implementation of a single-cylinder two-stroke engine equipped with an auxiliary cylinder is described. The purpose of such a cylinder is to modify the diagram of flow induction through the inlet and transfer ports in the main cylinder in order to make it asymmetrical relative to tdc.
Subsidiarily, the piston in the auxiliary cylinder is used to improve the balance of reciprocating forces.
This engine has been developed for specific use in trial motorcycles.

[lohring]

All these ideas have been worked on for a long time. My favorite summary is below. Look at the diagrams at the end of the paper. Today, the simple tuned pipe engine develops more power with minimum complexity.

Lohring Miller