ESE's works engine tuner

[Muhr]

I tested as well the expensive 3mm longer race plug , with the body machined back to put the gap close to the chamber center , again , no power at all.
Maybe the the new shallower chamber with the semi flat top piston makes the idea redundant.
Bugger.

Good test with the cooling!
Had the spark plug worked, one would have had to succeed in ducking below regulations, which would have been a difficult challenge.
However, a very interesting challenge!
I guess toroidal with a slot for volume measurement and a long spark plug would have been an option

"2.16.8 - Spark plug
In all categories except Superkart, the ignition spark plug must be mass-produced and remain strictly original. The spark plug barrel and the electrode insulation (electrodes not included) tightened on the cylinder head must not extend beyond the upper part of the combustion chamber dome (see Appendix No. 7)."

https://backend.fiakarting.com/sites/default/files/2020-01/Web_RT_Appendix%207.pdf

[nitro2tfx]

Well here we go again with me disagreeing and thinking in a completely differnt tangent to you Nitro.
What you have shown with the 4 stroke plot is simply what has been documented in many SAE papers describing what is needed , and comparing TFX data to simulation data to prove it.
Perfect example is SAE 2001 01 1797/4218.
This showed real time data against Optimum Power Technolgy's 4 stroke sim package ( I can use that as its free to Uni engineering depts )
Testing a straight pipe Vs a pipe/diffuser combination.
4Ts exhausts are simpler in that there are two effects that can contribute to power , pulling as wide and as deep a depression around TDC overlap as possible , and secondly a strengthening leftward
depression during the EVO period to reduce exhaust stroke pumping losses.

Achieving both together can accentuate peak power , spreading the two effects out favours powerband ( torque ) width.
Saying that achieving that plot could not be done just using a sim package is narrow minded rubbish - again it comes back to interpreting the data , and intellectual accuity in coming up with innovative
solutions to generate the desired end result.
Its easy to see on that plot that achieving even greater depression , sooner , between - 150 and -30 would reduce pumping losses during EVO. I dont need real data to see that trend at all.

The result certainly isnt limited by the sims ability to represent vey accurately the real time data - the big differnce being the time and work involved is exponentially less the harder the task at hand is.
Sadly for 4T tuning the exhaust plays second fiddle big time to the gains achievable with inlet tuning , the complete reverse of a 2T.
Variable length Exhaust = big 2T power , variable length Inlet = big 4T power.

EDIT - I could not resist adding a reply to this quote " I know we aren't here to talk 4 strokes, but for reference sake, this is basically what an exhaust trace looks using a typical exhaust header design (on a 4 stroke)."

That pressure trace result is NOT from a typical exhaust header , its a completely wrong example , there is virtually no help with exhaust stroke pumping losses , and there is virtually no depression around TDC overlap
ie that pipe setup is NOT tuned correctly to the chosen rpm.
The super secret setup IS tuned correctly so will obviously produce superior pressure trace shape and power as a result.


Well maybe you should resist lol.....The first trace is from the factory header. I showed the trace at the same engine speed as for the other pipe, simply for comparison sake. Yes this factory header (4-2-1) would be more effective (better trace) at a bit lower rpm, which I have not shown, but I think we all know what it will look like at a lower rpm and this is not a 4 stroke forum so I didn't bother taking up any more space with the discussion. The first trace is what it is, for that engine and that header at THAT rpm. I have seen and worked with real exhaust traces for an extremely wide range of customer engines, from all over the world, for 20 years.

The second trace with the deep depression is not a straight pipe, nor is it a straight pipe with a diffuser, it is a unique pipe, no one has one like it.

Lastly I take every SAE paper with a grain of salt, irregardless of topic. Here is why. 1) I can pick out bits of BS in the few papers for which I know as much or more about the topic than the authors, so I know BS must also exist in some other papers too on topics that I don't know as much about 2) I have been involved with some SAE papers being written and there is a degree of fudging as well as over simplification that happens, regularly. To be honest I would never reference an SAE paper, if the content mattered that much to me I'd do it myself and know what's what (and more), firsthand.

[jbiplane]

Anyone know how assembled boxer and inline twins in serial production? How they ensure relative position of components without truening?
I did some assembly jigs and making minor improvements, but may be somebody know good answer to not invent "bycycle".

[husaberg]

Still cant stop getting annoyed when 8 of 10 clever dick ideas turn out to be flops.
Today , of all days at 30* C you would think cooling the transfer duct outer walls would be worth a bunch of power - but no.
Complete waste of time , so I tested and retested, doing all gear runs , as well as 6th gear WOT pulls - no power to be had.
A huge dissapointment.
I tested as well the expensive 3mm longer race plug , with the body machined back to put the gap close to the chamber center , again , no power at all.
Maybe the the new shallower chamber with the semi flat top piston makes the idea redundant.
Bugger.

Have you tested the insulating paint on the case and transfers?

Also the temps of the Crankcase could it be it gave no power increase as it couldn't cool them lower then the crankcase temp was already?
did it already have between duct cooling?

[Vannik]

Lastly I take every SAE paper with a grain of salt, irregardless of topic.

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.

[husaberg]

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.

Hi Neels

Have you ever read the Sae papers on water injection, I have never been able to find any free versions i believe it was from Fleck.

[andreas]

[QUOTE=nitro2tfx;1131180584]Well maybe you should resist lol.....The first trace is from the factory header. I showed the trace at the same engine speed as for the other pipe, simply for comparison sake. Yes this factory header (4-2-1) would be more effective (better trace) at a bit lower rpm, which I have not shown, but I think we all know what it will look like at a lower rpm and this is not a 4 stroke forum so I didn't bother taking up any more space with the discussion. The first trace is what it is, for that engine and that header at THAT rpm. I have seen and worked with real exhaust traces for an extremely wide range of customer engines, from all over the world, for 20 years.

The second trace with the deep depression is not a straight pipe, nor is it a straight pipe with a diffuser, it is a unique pipe, no one has one like it.

Lastly I take every SAE paper with a grain of salt, irregardless of topic. Here is why. 1) I can pick out bits of BS in the few papers for which I know as much or more about the topic than the authors, so I know BS must also exist in some other papers too on topics that I don't know as much about 2) I have been involved with some SAE papers being written and there is a degree of fudging as well as over simplification that happens, regularly. To be honest I would never reference an SAE paper, if the content mattered that much to me I'd do it myself and know what's what (and more), firsthand.[/QUOTE



What is this drama queen prancing around crying; I know something y'all don't. Either tell the story (and I dont think there is one), or don't. S'il vous plait.

[katinas]

I tested as well the expensive 3mm longer race plug , with the body machined back to put the gap close to the chamber center , again , no power at all.
Maybe the the new shallower chamber with the semi flat top piston makes the idea redundant.
Bugger.

Wob, have you tried to retard ignition?

Very interesting results with trans cooling, thanks for testing.

[nitro2tfx]

What is this drama queen prancing around crying; I know something y'all don't. Either tell the story (and I dont think there is one), or don't. S'il vous plait.

The only story here, and it was meant to be a short story but got into diversions, is that it is possible to create a 2 stroke like pressure trace without using a 2 stroke like pipe. Basically a pressure pulse just after exhaust opening, followed by a deep depression, followed by another LARGE pressure pulse. An example real data trace was shown a few of pages back. I described how we arrived at it. The story has been told already. Drama came after that when buttons got pushed.

[Vannik]

Hi Neels

Have you ever read the Sae papers on water injection, I have never been able to find any free versions i believe it was from Fleck.

"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

[jbiplane]

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.
If someone give me doi of article which is usefull, I can get it for free and share using local univervity portal

Sample - https://doi.org/10.1115/1.4046711

[jfn2]

Hello Husaberg
I also have that paper and for some reason, and I don't remember why, I wrote another number on the paper. 93A083 They might have changed the orig number? A person by the name of Randy Norian tried this on a RG500 with good results. I think he lives in OZ but not sure. Also a man whose name is Mark Dent from UK. He is with Mark's Dynapro.co.uk knows something about Randy's bike. I have a write-up by Randy about his set-up if your interested. Jeff

[Muhr]

Got a package with some cast parts today. It will be fun to start with some actual fabrication!

[nitro2tfx]

A couple examples of incomplete knowledge.

First we "know" that a thin edge orifice plate has a coefficient of discharge of around 0.6 i.e. it flows terrible, and of course other unfavorable shapes have fairly poor coefficients as well.

Second we "know" that once a pressure ratio of about 0.528 is reached on the low pressure side of a non-diffused opening then decreasing the pressure on the low side further will not result in any additional mass flow.

This information is readily available, but it is incomplete. Both only apply to specific scenarios, and there are scenarios inside an engine where neither statement holds true. Some people know this, but I suspect it is not common knowledge ?

[gamma500]

Friend told me about this: https://en.m.wikipedia.org/wiki/Sci-Hub

No, never used it to download scientific papers 😉

[husaberg]

Hello Husaberg
I also have that paper and for some reason, and I don't remember why, I wrote another number on the paper. 93A083 They might have changed the orig number? A person by the name of Randy Norian tried this on a RG500 with good results. I think he lives in OZ but not sure. Also a man whose name is Mark Dent from UK. He is with Mark's Dynapro.co.uk knows something about Randy's bike. I have a write-up by Randy about his set-up if your interested. Jeff

cheers all on the RG500 stuff links are dead i posted them at the time but they had no SAE paper. edit it did have the number though lol
SAE paper 931506,
https://www.kiwibiker.co.nz/forums/showthread.php/155907-ESE-s-works-engine-tuner?p=1130479247&highlight=randy#post1130479247

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130173462&highlight=fleck#post1130173462

[wobbly]

Nitro , by slinging shit at SAE in general due to background " fudging " to make a papers revelations appear more substantiated is bit bit rich , when you then go ahead and do exactly that.
By presenting a " factory " pipe data log , that is clearly working nowhere near its optimum design parameters , then immediately comparing that to your design , that is obviously exactly on its
designed working parameters , smacks of SAEsque fudging of the first order.
But the paper I quoted , showed conclusively using equally both real and sim data , exactly why a pipe with a megaphone is superior to a single pipe.

You came on here with a mission to convince us that TFX is functionally capable , and is far superior to sim data as it can somehow enable off the wall new design techniques to be validated - that sims simply cannot achieve .
Well sorry buddy you have failed miserably in that particular goal so far.

I have no idea , nor the time to try without a paying customer , if I am clever enough to design and replicate the amazing achievment you have shown.
But Im still entirely conviced that it would come down to the degree of intellectual assesment of the data .

TFX or sim , to me is still completely irrelevant - as you have shown nothing at all that would enable me to revaluate that opinion.
Your 20 years of experience in pipe manufacture and design is also irrelevant , ive been doing it for twice that , and realise I still know jack shit.

[wobbly]

Katinas and Muhr , no I didnt try retarding the ignition as the cylinder I used had a new type of very shallow chamber to suit the semi flat top piston.
This setup uses very retarded ignition already , with high trapped compression in comparison to older designs on the same fuel.
Also , like the water test dyno runs , the egt was identical , if the flame speed was improved , it would react like more advance ie lower egt.
Real issue is that we run a fixed advance ( flat ) curve , and always there is a direct tradeoff between front side power and overev.
Also that particular cylinder had cooling inside the short turn duct radius ( but no I didnt tell you that ).

What I really wanted to prove was that the outer duct cooling was a step in the right direction , the real long term goal was to have water running across the top of the mains , cooling the transfer duct
entry in the case , then entering the cylinder next to the boost port.
Sadly that is going to be a real hard sell now.

[husaberg]

"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

Sorry i missed that response Neels, cheers

[Frits Overmars]

....What I really wanted to prove was that the outer duct cooling was a step in the right direction , the real long term goal was to have water running across the top of the mains , cooling the transfer duct entry in the case , then entering the cylinder next to the boost port.Cooling the insides of the transfer ducts certainly works, as Jan Thiel proved, so cooling their outsides would be the logical next step. But in my view the real long term goal would not be cooling the transfer ducts, but preventing heat from the ducts getting to the mixture.
I've considered inserts in the ducts, with an air gap between the duct walls and the inserts, like double glazing, but the simplest solution I think would be applying a thermal barrier coating to every surface in the engine that comes into contact with the mixture (except the piston crown and the exhaust duct, because there the combustion gases would drive the surface temperature of the coating to insane heights). Then the only thing that could still heat the mixture would be the big end bearing, wich needs to get rid of its heat anyway (a strong argument against direct fuel injection, unless we provide the big end with direct oil injection, as Neil Hintz will be doing).

[Condyn]

https://youtu.be/jo-r7LwI70Q

850cc etec engines utilize a direct big end lubrication scheme.
Unfortunately you will have to copy and paste the link as I had to edit.

[nitro2tfx]

Nitro , by slinging shit at SAE in general due to background " fudging " to make a papers revelations appear more substantiated is bit bit rich , when you then go ahead and do exactly that.
By presenting a " factory " pipe data log , that is clearly working nowhere near its optimum design parameters , then immediately comparing that to your design , that is obviously exactly on its
designed working parameters , smacks of SAEsque fudging of the first order.
But the paper I quoted , showed conclusively using equally both real and sim data , exactly why a pipe with a megaphone is superior to a single pipe.

You came on here with a mission to convince us that TFX is functionally capable , and is far superior to sim data as it can somehow enable off the wall new design techniques to be validated - that sims simply cannot achieve .
Well sorry buddy you have failed miserably in that particular goal so far.

I have no idea , nor the time to try without a paying customer , if I am clever enough to design and replicate the amazing achievment you have shown.
But Im still entirely conviced that it would come down to the degree of intellectual assesment of the data .

TFX or sim , to me is still completely irrelevant - as you have shown nothing at all that would enable me to revaluate that opinion.
Your 20 years of experience in pipe manufacture and design is also irrelevant , ive been doing it for twice that , and realise I still know jack shit.

Hmmm for a smart guy, and you are, and one who knows what happens when assumptions are made, you sure do make a LOT of assumptions. So lets get this straightened out once and for all.

I didn't just "come on here". I have been on here for about 8 years (roughly 4 years as a member and I guess about another 4 years before that), reading quietly. I have read almost every page in this thread, quietly. A few years ago I made a couple posts and promised to post some real data traces for a Banshee. Time went by and things came up and it didn't happen, about a month or two ago I finally got around to posting a couple traces from a Banshee ( I have more but whether they get posted or not is debatable at this juncture). Somebody, I won't mention any names lol, was all over me for doing that. How dare I post real data in a great big long thread that has only sims ? That person attacks everything I post, then I have to be on deck to defend it, again and again, apparently.

You are off on some kind of a tangent with the two 4 stroke traces I posted. I did not post the best 4 stroke trace ever generated by a pipe on planet earth vs the TFX pipe, so get off that notioin. What I posted were 2 traces, from the same engine at the same rpm, one with a 4-2-1 header and one with a TFX pipe, the POINT being that a 4 stroke conventional header does NOT generate exhaust traces that look like a 2 stroke exhaust stroke i.e. different shape but the TFX pipe DOES generate a trace that looks like a 2 stroke trace yet the TFX pipe itself does not look like a 2 stroke pipe. So what. I'm not selling the TFX pipe to anybody. It's interesting, or at least it was meant to be. I thought that perhaps some members might not know what a 4 stroke trace looked like (i.e. it looks a lot different than a 2 stroke trace), that's why I posted the (4-2-1) 4 stroke trace, NO OTHER REASON.

I came in here with NO MISSION AT ALL. As I mentioned I have been on here about 8 years reading quietly with almost no posts. I thought that since there was no real pressure data in the thread that it might be interesting for people to see real data, after all this is 2021 not the dark ages. Have you seen me posting the company phone number ? How about the company website ? How about the company email ? NO YOU HAVE NOT. In fact I was asked directly in the thread for that info, and I did not respond to it, if you bother to look back a few pages you will see that. Do I expect to make sales from posting on here ? Nope not even one.

What I do expect from this site, since it is more technical and less trashy than some other sites, is to be able to post technical 2 stroke info on here and have people ask legitimate technical questions which hopefully I can provide answers to. Being attacked everytime I post anything is ridiculous.

Further I don't think you have any idea what I do for a living by the sounds of it. I am not in competition with you in any way, shape, or form.

[wobbly]

Nitro - OK , I accept your critism of my now obviously triggered over reaction , but the underlying point of all the ranting was due to two factors.

I have a couple of " money no object " customers that have TFX available to them , but they use my sim experience as it gets results, fast , by using data that is so close to reality as to make the distinction irrelevant.
Secondly is the still unproven assertion that your real data somehow adds a new dimension to the analysis process , facilitating results that the sim data cannot enable.
I still have a real issue with this whole concept - maybe a more detailed explanation of this process is simply all that is needed.

Competition with you or anyone is completly irrelevant , as like you I dont want or need the work except for the odd technical challenge.
But one thing you should be aware of ( maybe you are , having read so much ) was a long drawn out shit fight we had on here from one self proclaimed genius , who continually told us about how many of us regularily
contributing here , were wrong.
But thru the whole discussion he gave us absolutely no useable technical input of any substance whatsoever.
His resultant banning from the site , added to the same result he suffered from a couple of other two stroke dedicated forums.
This is what would have triggered the somewhat rude reply you got ending with sil vous plait.

Simply put , please dont take anything I have said as a personal attack , we are all frustrated , and on the edge of our chairs wanting to know the process by which your amazing technical feat was achieved.

[lohring]

We ran water injection into the header on our 35 cc race engine. The goal was to boost acceleration into the speed traps. The first graph shows the dyno results. The purple line is with water. The power drops off at around 21,000 rpm. With water off we got good power to over 23,000 rpm. The second graph shows rpm vs time in the actual boat. You can see that the rpm plateaus at around 20,000 rpm but jumps up with the water off. Since the pipe was designed for high rpm, not maximum power, water injection gave us the best of both worlds. Of course, this system is easy in a boat.

Lohring Miller

348424348425

[Larry Wiechman]

Imagine a collaboration involving an engineer who codes 2-stroke simulation software, a clever
tuner skilled in the use of the software, and a real-time pressure instrumentation expert.
Now mix in a physicist and a number of crafty patternmakers, machinists, and welders.

[wobbly]

Haha , you are describing exactly what QUB used to be.

[Larry Wiechman]

It was just an observation, as I don't usually see that much talent in one room, at least not in my neighborhood.

[F5 Dave]

Imagine a collaboration involving an engineer who codes 2-stroke simulation software, a clever
tuner skilled in the use of the software, and a real-time pressure instrumentation expert.
Now mix in a physicist and a number of crafty patternmakers, machinists, and welders.

Add a chancer, a marketer looking for investments, and a CEO with a penchant for gambling and ladyboys. . .

What?


Send money to the usual address. :rolleyes:

[philou]

F5dave Are you talking about the government of my country ? :facepalm:

[Muhr]

Also that particular cylinder had cooling inside the short turn duct radius ( but no I didnt tell you that ).

Guess you did tests on just that too. What is your experience of it?

[andreas]

Yes, I retreat. Please do not refrain from elaborating this topic.

[philou]

Cylinder TM kz10c with epoxy transfert port for inner radius

348426348427

[F5 Dave]

That looks real nice but what point do you reduce the volume capacity of the ducts to less than you want delivered?

I did a similar thing with a more elevator shaft transfer duct. Big improvement for sure. Except the dyno didn't believe me. Never got round the excavation a little more of the outer wall which was no where as modern as your example.

[wobbly]

Muhr , the cylinder with extra cooling on the inside of the ducts was worth about 1/2 a Hp , same result as Jan's Aprilia test.
Smaller duct volume was tried for the R1 , it didnt work with the updated A port front wall angle and port shape change.

[Muhr]

A couple examples of incomplete knowledge.

First we "know" that a thin edge orifice plate has a coefficient of discharge of around 0.6 i.e. it flows terrible, and of course other unfavorable shapes have fairly poor coefficients as well.

Second we "know" that once a pressure ratio of about 0.528 is reached on the low pressure side of a non-diffused opening then decreasing the pressure on the low side further will not result in any additional mass flow.

This information is readily available, but it is incomplete. Both only apply to specific scenarios, and there are scenarios inside an engine where neither statement holds true. Some people know this, but I suspect it is not common knowledge ?

I had hoped for an interesting discussion on this topic as myself feel that I am missing a piece of the puzzle to understand the outcome in some simulations. Also adiabatic compression would be interesting to get a better understanding of!


Muhr , the cylinder with extra cooling on the inside of the ducts was worth about 1/2 a Hp , same result as Jan's Aprilia test.

Thanks

[SwePatrick]

Today , of all days at 30* C you would think cooling the transfer duct outer walls would be worth a bunch of power - but no.
Complete waste of time , so I tested and retested, doing all gear runs , as well as 6th gear WOT pulls - no power to be had.
A huge dissapointment.


I somewhat remember i was sceptical about cooling this area.
If any power should be had from this you still need to cool it way more than engines water is beeing able to.
Try instead weld fins on cylinder and blast them with a nitrous shot or similar during entire pull, just to verify there is any power to be had.
If no gains during this you can drop this and go look at some other ideas.


Rgds.

[wobbly]

The idea of cooling the outer walls of the transfers was an attempt at proof of concept - but was a fail , why , still eludes me .
Jan had already proven cooling the inner walls from bore heat was worthwhile , and the outer duct area runs at least twice as hot as the water.
It would have been easy to run cooling this way in a new cylinder design , for the next homologation , or any project from scratch.
I know having all the cold water enter the cylinder from the boost port , and running forward over the transfers first , makes 1 Hp , so that alone is
worth looking at directing flow to run forward from the gearbox insulation gallery, over the mains ( under the transfer feed area ) and up into each side of the boost port.
This makes sense , opposite to the old , usuall way of cooling the Exhaust duct first.

[ken seeber]

Wob,

Izerbeantinkin…

What about reverting to the standard cooling circuit, but leaving the A&B cooling covers on. Then, connecting a garden hose to these, presumably your tap water temp will be pretty cool over there, maybe 15 or so. This auxiliary circuit might affect the result.

Another thought is that possibly the CSA of the covers it too restrictive and that the overall flow rate was reduced.

[SwePatrick]

The idea of cooling the outer walls of the transfers was an attempt at proof of concept - but was a fail , why , still eludes me .
Jan had already proven cooling the inner walls from bore heat was worthwhile , and the outer duct area runs at least twice as hot as the water.
It would have been easy to run cooling this way in a new cylinder design , for the next homologation , or any project from scratch.
I know having all the cold water enter the cylinder from the boost port , and running forward over the transfers first , makes 1 Hp , so that alone is
worth looking at directing flow to run forward from the gearbox insulation gallery, over the mains ( under the transfer feed area ) and up into each side of the boost port.
This makes sense , opposite to the old , usuall way of cooling the Exhaust duct first.

Kawasaki runs on some of their twostroke dirtbikes like that, coldest water direct into above boostport, then flowing forward against exhaust and then up above the head and out to the radiator.
I exprimented with adding a water inlet at above the exhaustport, i couldn´t see any gains.
I just figured that it 'shortcircuited' flow so less flow above transfers was the result and thereby the gains from colder exhaustduct was eaten up by less cooling above transfers.

But when i tested with coolantflow direct from the tappet in the house instead of from the radiator it gained a lot(above 2hp).
This was a total loss system, heated water was just dumped into the well in the floor.

[F5 Dave]

You'd need a long hose . Don't pass that guy on the inside.:eek:

[Dutch Fisher]

Perfect example is SAE 2001 01 1797/4218.
This showed real time data against Optimum Power Technolgy's 4 stroke sim package ( I can use that as its free to Uni engineering depts )
.

If your local Uni upgraded to Automated Design, you could use the other editions

[Dutch Fisher]

The idea of cooling the outer walls of the transfers was an attempt at proof of concept - but was a fail , why , still eludes me .
Jan had already proven cooling the inner walls from bore heat was worthwhile , and the outer duct area runs at least twice as hot as the water.
It would have been easy to run cooling this way in a new cylinder design , for the next homologation , or any project from scratch.
I know having all the cold water enter the cylinder from the boost port , and running forward over the transfers first , makes 1 Hp , so that alone is
worth looking at directing flow to run forward from the gearbox insulation gallery, over the mains ( under the transfer feed area ) and up into each side of the boost port.
This makes sense , opposite to the old , usuall way of cooling the Exhaust duct first.

With the thinking cap on:

Are we wholly certain as to what cooling the inner transfers does. Yes 1 Hp gain, but why? There is a cause (the cooling of the surrounding metal), but are there more than 1 effect?

A thought: Does cooling the inner wall therefore produce a temp gradient in the transfer stream were-by the inner flow of the stream is cooled and energy is taken out reducing the molecule excitement.
The effect being a reduction in energized eddies and a (poss) thinning of the boundary layer in the inner wall so as to assist the "turning of the corner" as there has to be a pressure difference across the area of the stream, inner wall to outer. The lowering of the outer wall temp having no effect as the outer wall is the "wall of death" for the stream.

[andreas]

Some cap you got there, gives me the giggles by proxy.

[husaberg]

With the thinking cap on:



oddly enough the dutch caps here are to prevent the fishy's.

[Dutch Fisher]

Some cap you got there, gives me the giggles by proxy.

oddly enough the dutch caps here are to prevent the fishy's.


Welcone to the wonderful world of Northern English colloquial expressions
My thinking cap is modelled on the Fred Dibnah design (google him)



https://ichef.bbci.co.uk/images/ic/640x360/p01h0ntf.jpg

[TZ350]

.
More from "2 Stroke Stuffing".
.
<iframe width="560" height="315" src="https://www.youtube.com/embed/Yuj8rdZ83ac" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

[SwePatrick]

You'd need a long hose . Don't pass that guy on the inside.:eek:

There are a lot of wireless technology today, just invent hoseless ;)

[Muhr]

Have felt that the connecting rod that I initially chose for the project was a bit of a shortcut that did not feel really good. developed for an engine with a clearly more favorable environment than what I intend to expose it to.
This is now taken care of with a billet rod also got 1mm more that I wanted, to 89 mm.
So now I can nerd away with 48h in the tumbler and then DLC coting

[Frits Overmars]

Have felt that the connecting rod that I initially chose for the project was a bit of a shortcut that did not feel really good. developed for an engine with a clearly more favorable environment than what I intend to expose it to.
This is now taken care of with a billet rod also got 1mm more that I wanted, to 89 mm.
So now I can nerd away with 48h in the tumbler and then DLC cotingDLC coating a two-stroke rod? Last time I checked, DLC would not reliably stand more then 250°C, and I fear that things can get quite a bit hotter in a two-stroke big end bearing

[andreas]

I can't really grasp how the balancing works. A tandem counterrotating 0* firing delay has no vibration, 90v conterrotating 90*firing delay also good, boxer counterrotating 180* firing delay good yes? Parallell twin vibrates due to rocking, but why doesn't a same directon rotating 180* firing delay tandem work?

[Vortex]

Have felt that the connecting rod that I initially chose for the project was a bit of a shortcut that did not feel really good. developed for an engine with a clearly more favorable environment than what I intend to expose it to.
This is now taken care of with a billet rod also got 1mm more that I wanted, to 89 mm.
So now I can nerd away with 48h in the tumbler and then DLC coting

Hi there,
Just as an information, in the current OK engine from Vortex who makes easy 16.000 rpm a DLC treated connecting rod (104mm) performs without any problems, but the needle bearings are definitely NOT running on DLC coated surfaces.
According to the current status, DLC can be used up to max. 350 deg.C
Here it was only to be able to omit the silver shims, use a 5mm shorter crank pin and stiffen a lot more the crankshaft.
It's probably easier for the process to coat the whole conrod and then hone the bearing surfaces.

Cheers

[Muhr]

DLC coating a two-stroke rod? Last time I checked, DLC would not reliably stand more then 250°C, and I fear that things can get quite a bit hotter in a two-stroke big end bearing

Thanks Frits! I've been thinking about what you can expect in terms of temperature when setting clearances between surfaces if, for example, you were to try experimenting with Hydrodynamic bearings. Can't say I have any idea but usually don't see any major discolorations.

[Muhr]

Hi there,
Just as an information, in the current OK engine from Vortex who makes easy 16.000 rpm a DLC treated connecting rod (104mm) performs without any problems, but the needle bearings are definitely NOT running on DLC coated surfaces.
According to the current status, DLC can be used up to max. 350 deg.C
Here it was only to be able to omit the silver shims, use a 5mm shorter crank pin and stiffen a lot more the crankshaft.
It's probably easier for the process to coat the whole conrod and then hone the bearing surfaces.

Cheers

Here are a few more examples

[wobbly]

A 180* Tandem with same crank rotation would need an intermediate gear - just to make it work that way.
But balance wise , it would mean that when the crankwheel counterweights were at TDC/BDC they would form a rocking couple , just like a Parallel Twin @ 180.
Then when at 90* the two out of balance counterweights ( any number less than 100% BF ) would both be facing opposite each other ,forward or backwards - cancelling the horozontal resultant.
The intermedate gear needs to be the same size as each crank gear , making it too big to drive the clutch - and a balance shaft off that gear cant kill the rocking couple , as its in the same plane.
Thus another small gear is needed to drive the clutch - result is no advantage over a concurrent firing Tandem , but an extra power consuming gear/bearings , and less big bang tyre grip.

[SwePatrick]

What have i missed with dlc coating.
Diamond like coating, Why coat the whole rod?
Why even bother when not coating bearing surfaces?

Why not make an aluminiumrod with inserts for the needlebearings?
And no,, they won´t breake if using new tech, old alurods had a lifespan.
But new alloys make them way wey more reliable.
Watched a guy on youtube that had them in his engine for 9 years and none of them breaked.(1000+ Honda engine)

[andreas]

A 180* Tandem with same crank rotation would need an intermediate gear - just to make it work that way.
But balance wise , it would mean that when the crankwheel counterweights were at TDC/BDC they would form a rocking couple , just like a Parallel Twin @ 180.
Then when at 90* the two out of balance counterweights ( any number less than 100% BF ) would both be facing opposite each other ,forward or backwards - cancelling the horozontal resultant.
The intermedate gear needs to be the same size as each crank gear , making it too big to drive the clutch - and a balance shaft off that gear cant kill the rocking couple , as its in the same plane.
Thus another small gear is needed to drive the clutch - result is no advantage over a concurrent firing Tandem , but an extra power consuming gear/bearings , and less big bang tyre grip.

Ok, thanks Wobbly. I'll have to ponder this.

[teriks]

What have i missed with dlc coating.
Diamond like coating, Why coat the whole rod?

You specify where you need a functional coating, and if you need any surface masked.
The rest, well.. it gets the black stuff apart from where its supported.

Why not make an aluminiumrod with inserts for the needlebearings?
And no,, they won´t breake if using new tech, old alurods had a lifespan.
But new alloys make them way wey more reliable.
Watched a guy on youtube that had them in his engine for 9 years and none of them breaked.(1000+ Honda engine)
What alloys are those?
Asking for a friend that's changing aluminium rods every 30min runtime to hopefully avoid developing sudden new 360deg intakes..

[Condyn]

Going back to Vanniks write up including contact discontinuities. While developing pipes for vintage engines (1970s) I have often times drifted in a certain direction, even while raising the target rpm. The pipe gets longer than the factory configuration. I notice the HP going up. But being that the pipe is growing in length, is this a T-bone guarantee that my diffusers are too efficient, creating more short circuiting adding to the smearing effect and further eliminating the boundary between gas temps?

[andreas]

Going back to Vanniks write up including contact discontinuities. While developing pipes for vintage engines (1970s) I have often times drifted in a certain direction, even while raising the target rpm. The pipe gets longer than the factory configuration. I notice the HP going up. But being that the pipe is growing in length, is this a T-bone guarantee that my diffusers are too efficient, creating more short circuiting adding to the smearing effect and further eliminating the boundary between gas temps?

If I recall your last entry, it was somewhere along the lines of " how can the exhaust pulse that is responible for drawing a certain amount of fresh charge up and into the pipe be able to push the same amount back in again, when it has been weakened by friction and losses in the reflection".If this is how you intended the question, don't focus too much on the contact discontinuty, but look at how the original pulse branches into one decompression wave in the diffuser and the remnents of that pulse eventually becomes the compression wave.

Why the pipes are longer even though the engine speed is higher- more information needs to be presented, but I don't think stronger diffusers is the guaraneed cause of it.

[wobbly]

Condyn , I think there are two effects going on in your situation.
Firstly , yes , " overscavenging " as Mr K Kanemoto called it , by having overly fat mid , and therefore overly efficient diffuser sections causes increased shortcircuiting
and thus a smeared , longer , larger volume of mixed raw and burnt fuel.
But secondly in your older ( I am assuming ) single port exhausts , you cant use the huge effect a very restricted duct exit area can have on the efficacy of the discontinuity.

A single Ex port seems not to respond favourably to anything less than a 90% duct exit area.
Whereas a T or 3 port with a ton of Blowdown loves around a 75% restriction , to hit the magic Mach 0.8 number.

Edit - good example would be a LC 350 Yamaha racebike. Keeping the original scavenging system ( B ports up at 35* ) the best I could do was 66RWHP.
The next version had staggered timings ( A first ) and with modern radial and axial angles , 10mm fatter pipes - 20mm shorter , first dyno run was 77RWHP without adjusting anything.

[Flettner]

The most advanced twostroke in the world, well, perhaps just the most advanced TPI in the world. Anyway its been sitting outside under a cover for almost a year, bad me.
Finaly got excited about it enough today to sort the Ignitech out, found spark. Turned the LINK ecu off and fired it up using plastic bottle injection. Loud, but it runs, yay. Tomorrow get the LINK ecu working.

[TZ350]

.
Great work Flettner. Now for the EFI....... :niceone::niceone::niceone:

[F5 Dave]

Yeah love to see an update on this.

Although dirtbikes are evil. Well mine is.

[SwePatrick]

You specify where you need a functional coating, and if you need any surface masked.
The rest, well.. it gets the black stuff apart from where its supported.
What alloys are those?
Asking for a friend that's changing aluminium rods every 30min runtime to hopefully avoid developing sudden new 360deg intakes..

As i understood then hone it away when setting bearing clearances, if so, why coat the whole rod, design only or does it make some sort of strengthening on the whole rod?
to me it´s just a coating to make for example wristpins withstand more wear and tear, it doesnt strengthen more then a couple of my on the surface, if even that.

I dunno about the alloy, i just know of peoples experiances, best in rc racing would be to buy a alu rod from one of the top producers, and you´ll have material for several rc rods ;)

[Muhr]

If you add material to something that was not developed with the tolerances for this, you need to remove material either before or after, depending on what you intend with the application.
Do not think anyone has claimed that you apply and then remove on surfaces you want to apply on, however, in many cases masking is more expensive than just running the whole piece.

[Condyn]

Wobbly, have you always stuck with the ( many times ) sited percentages of header and diffuser lengths even while developing an older single port engine, or do these numbers no longer carry their importance?

I asked you several months ago if I should consider a TPO stagger due to the old school scavenging layout, and you advised me to test a few things as you were almost certain simultaneous opening was not ideal in my case. Unfortunately I have not had a chance to grind any cylinders for this project yet.

Even with the best possible efforts in grinding and welding, a vintage engine still poses the largest limiting factor, which is the overall casting. Realistically, I do not believe I will be able to stop all of the trapping efficiency issues with these old engines, that is why I am searching for logic as to what pipe characteristics should help the cause.

[Frits Overmars]

A 180* Tandem with same crank rotation would need an intermediate gear - just to make it work that way.
But balance wise , it would mean that when the crankwheel counterweights were at TDC/BDC they would form a rocking couple , just like a Parallel Twin @ 180.
Then when at 90* the two out of balance counterweights ( any number less than 100% BF ) would both be facing opposite each other ,forward or backwards - cancelling the horozontal resultant. The intermedate gear needs to be the same size as each crank gear , making it too big to drive the clutch - and a balance shaft off that gear cant kill the rocking couple , as its in the same plane. Thus another small gear is needed to drive the clutch - result is no advantage over a concurrent firing Tandem , but an extra power consuming gear/bearings , and less big bang tyre grip.Seems like somebody forgot to tell Neil Hintz :msn-wink:
348488 348487 348485 348486348489

[Frits Overmars]

If you add material to something that was not developed with the tolerances for this, you need to remove material either before or after, depending on what you intend with the application.
Do not think anyone has claimed that you apply and then remove on surfaces you want to apply on, however, in many cases masking is more expensive than just running the whole piece.Are we still talking DLC? The toughest honing stones I know are diamond. And what did the D in DLC stand for? So if there are places where you don't want the DLC, masking seems the only option.

[lohring]

Big end bearings have been a weak link in our small engines as well. My article, Big End Blues (http://namba.com/content/library/propwash/2012/April/#/11/), describes this. My favorite solution was from the late Jim Allen. He ran two rollers per retainer window. He used a very high strength heat treated maraging steel for his retainer. Pictures below.

Lohring Miller

348490348491

[Frits Overmars]

Big end bearings have been a weak link in our small engines as well. My article, Big End Blues (http://namba.com/content/library/propwash/2012/April/#/11/), describes this. Lohring,
I was looking forward to an afternoon of reading pleasure, but I am unable to download your Big End Blues. All I see is an encouragement to download Adobe Flash Player, the most virus-sensitive software of the past 300 years.

[Muhr]

Are we still talking DLC? The toughest honing stones I know are diamond. And what did the D in DLC stand for? So if there are places where you don't want the DLC, masking seems the only option.

Well, I was general in my statement. anyway i agree that honing a dlc surface will be a problem. Making a start and stop on the thickness of a DLC coating will be a challenge in itself regardless of the material, and nothing I would choose to try. however, to cut off eg 0.5mm from a dlc coated part, I can not say is impossible as the material behind will give way.

[Flettner]

Yeah love to see an update on this.

Although dirtbikes are evil. Well mine is.

Im suitably ashamed of myself.
It means nothing but it felt good just to hear it bark a few times.
The plan is to have a dirt bike that is not evil, just fun but I still want max top end, you know, because you can never have too much top end on a dirt bike, aye, especially a 360cc rotary valve.
Interesting, the short bursts it did do, the throttle mechanisim worked.
https://youtu.be/bhKrRlZxomc

[wobbly]

Well done Frits , but to me Flett configured his drive like that for a specific purpose.
The big gear keeps the two cranks in phase but its primary function in life is the speed reduction directly to a prop.
How or why would an engine designer do it that way when a clutch and gearbox is required .
You could put the clutch on the big gear , but then the gearbox primary shaft runs thru the cranks.
Or to get around that you could have the crank and big drive gears centers inline , with the output shaft stacked directly below , but then the cylinders become spaced well apart and the rocking couple is huge.
Then as you would say KISS , have the cylinders as close together as the components allow , and with small gears on the cranks you could drive the clutch input gear directly behind.
But then you still end up with a big , extra , connecting gear/bearings , churning oil and adding inertia.
I think the 360* Tandem is the best configuration in a Superkart ( or in a bike only if the cranks/cylinders are angled , and the gear cluster stacked underneath ) - unless there is another solution you have , I cant see.

[Frits Overmars]

Well done Frits , but to me Flett configured his drive like that for a specific purpose. The big gear keeps the two cranks in phase but its primary function in life is the speed reduction directly to a prop. How or why would an engine designer do it that way when a clutch and gearbox is required . You could put the clutch on the big gear , but then the gearbox primary shaft runs thru the cranks. Or to get around that you could have the crank and big drive gears centers inline , with the output shaft stacked directly below , but then the cylinders become spaced well apart and the rocking couple is huge. Then as you would say KISS , have the cylinders as close together as the components allow , and with small gears on the cranks you could drive the clutch input gear directly behind. But then you still end up with a big , extra , connecting gear/bearings , churning oil and adding inertia. I think the 360* Tandem is the best configuration in a Superkart ( or in a bike only if the cranks/cylinders are angled , and the gear cluster stacked underneath ) - unless there is another solution you have , I cant see.I agree with you all the way Wob; I just couldn't resist pulling your leg with those pictures of Neil's tandemtwin :devil2:

[wobbly]

You forgot Frits ( so did I for a moment ) that I cant feel my leg being pulled.

[Andreas Nilsson]

https://forumbilder.com/images/2021/02/08/300-ignition-curves.jpg


I am currently building a KTM 300 TPI for supermoto and trying to get my head around the ignition curves. The older carbed bikes had a very mellow timing with 15deg max advance(Blue+ýellow), so when tuning I tried the red curve with 22deg max advance, worked really well. The New TPI bikes got TPS so i guess they found room to add more advance in the 3000-6000RPM range.(green+darkgreen) What i find strange is however that the new TPI ignition curve pull out very little advance. The classic theory would be to decrease advance and aim for around 15 deg @ max power RPM and furher decrease the advance after that.

Any good explanation why this igition cuvre looks like it does? After my first dyno runs i notice the engine goes notably flat right after the 7800RPM peak power. Is it perhaps a way to discourage overrevving ?

[lohring]

Try this:
348493

Lohring Miller

[Frits Overmars]

Try this:
348493
Lohring MillerGot it now. Thanks Lohring :niceone:

[wobbly]

Two reasons I can imagine.
First is that as you pull out advance the pipe runs hotter , thus giving more overev power - this is not what the factory want happening, the engine is already unreliable under warranty.
Second , if the thing did naturally want to overev with a hot pipe scenario , they would then have to add more fuel to keep the egt down.
Maybe the single per side TPI injector , is not capable of actually flowing sufficient fuel at those stratospheric 300cc rpms , so adding fuel isnt an option.
Adding an extra pair of injectors , as in the Mk2 TPI , would solve that issue - but KTM would know already they cant patent that , as some bunch of bastards from down under
have done it already.

[Brett S]

I think you should spark up the 2 stroke whipper snipper before the bike, that's a fire hazard..


The most advanced twostroke in the world, well, perhaps just the most advanced TPI in the world. Anyway its been sitting outside under a cover for almost a year, bad me.
Finaly got excited about it enough today to sort the Ignitech out, found spark. Turned the LINK ecu off and fired it up using plastic bottle injection. Loud, but it runs, yay. Tomorrow get the LINK ecu working.

[Flettner]

I think you should spark up the 2 stroke whipper snipper before the bike, that's a fire hazard..
Dont you you just use a match to clear the long grass?

Actually just been clearing around the bike, got stung by some jolly wasps. Barstards got what was coming to them, their nest is somewhat flat now.

[Peter1962]

Two reasons I can imagine.
First is that as you pull out advance the pipe runs hotter , thus giving more overev power - this is not what the factory want happening, the engine is already unreliable under warranty.
Second , if the thing did naturally want to overev with a hot pipe scenario , they would then have to add more fuel to keep the egt down.
Maybe the single per side TPI injector , is not capable of actually flowing sufficient fuel at those stratospheric 300cc rpms , so adding fuel isnt an option.
Adding an extra pair of injectors , as in the Mk2 TPI , would solve that issue - but KTM would know already they cant patent that , as some bunch of bastards from down under
have done it already.

Beaten at their own game ? :laugh:

[SwePatrick]

Well, I was general in my statement. anyway i agree that honing a dlc surface will be a problem. Making a start and stop on the thickness of a DLC coating will be a challenge in itself regardless of the material, and nothing I would choose to try. however, to cut off eg 0.5mm from a dlc coated part, I can not say is impossible as the material behind will give way.


I would say it´s far more better process to hone rod to correct spec including coating, BEFORE coating it.
And aslo include the needlebearing cages and the wristpins.

[Frits Overmars]

I would say it´s far more better process to hone rod to correct spec including coating, BEFORE coating it.Quite right Patrick. DLC-coating an object that is not very smooth already, will in fact create a diamond file.

[Muhr]

I would say it´s far more better process to hone rod to correct spec including coating, BEFORE coating it.
And aslo include the needlebearing cages and the wristpins.

Hi Patrick sorry if you feel I have suggested any execution.:innocent:
To my knowledge, I have neither expressed which method is preferred nor that one should process bearing surfaces after dlc coating.
Dlc coating is in many cases thinner than the tolerance range of a roller bearing assembly, which means that you probably you can find a pin and a rod that you can run without machining, however, a very good Ra is needed. In the picture with tm rod you can see a pankl piston pin that has lost most of its coating due to slightly lower surface finish (that is at least my analysis). all parts have been used one World Cup round.

[SwePatrick]

Might have misunderstood, someone was talking about honing after coating.
But, is it really smart to have a really really fine Ra?
Oil won´t be transported as with crosshatch honing, and it maybe will make the rollers slide instead of rotate with disaster as result.

[Muhr]

”Rolling contact bearings have to be lubricated in addition to having exceedingly good surface
finishes.

The life of a rolling element bearing depends to a large extent on the smoothness of the
contacting surfaces – the balls, rollers, and races. Typical surface roughness dimensions for
production bearings are as follows:

Balls 2– 3 μin rms
Ball races 6–10 μin rms
Rollers 8–12 μin rms
Roller races 10–20 μin rms”

Here is a pretty good video on the subject, he has made many interesting videos.

https://www.youtube.com/watch?app=desktop&v=JCM2YHcd8kU

[Peljhan]

Did anyone saw video on FB?

https://www.facebook.com/jan.thiel.9400/videos/733939527326518

It's birth of Aprilia RSA :eek5:

I remember Jan comment about this. (see attachment). We can see they are inspecting oil leak mentioned.

Somewhere he also said, that bottle of champagne was opened, probably on facebook and I can't find it :D

Pure gold!

[Frits Overmars]

Did anyone saw video on FB?
https://www.facebook.com/jan.thiel.9400/videos/733939527326518
It's birth of Aprilia RSA :eek5:
I remember Jan comment about this. (see attachment). We can see they are inspecting oil leak mentioned.
Somewhere he also said, that bottle of champagne was opened, probably on facebook and I can't find it :DHere are two links you can try.

https://www.facebook.com/jan.thiel.9400/videos/733939527326518/
https://www.facebook.com/groups/265987933547445/permalink/2452311541581729/

The actual opening of the bottle is not in the video, but handing out the champagne (in plastic cups) is.

[Haufen]

Did anyone saw video on FB?

https://www.facebook.com/jan.thiel.9400/videos/733939527326518

It's birth of Aprilia RSA :eek5:

Thanks!
I am totally into that clutch lever for the dyno operator at 8:45min in the video!

[wobbly]

Muhr , one thing many dont realise is that the rod bores and the pin surfaces dont wear significantly at all.
I routinly replace the big end cage /rollers/washers 4 times in a crank using the same pin and rod.
Its the cage that eventually wears off the silver coating , allowing the rollers to skew , then skid then fail.
After 4 replacements you can just start to measure wear on the pin and rod bore - but hey , they are real smooth by that stage.

One other benefit is that by pressing out opposite sides each time , this helps to maintain the crankwheel press fit , as eventually after multiple pin replacements the pin hole bore relaxes
its interference value.
I noticed the Pankle silly money capped small end pin in your post , this is easy enough to do youself if you can do the cad drawing and have the caps CNC machined , then laser welded in.
The laser guy here has a standard charge , and will do one or 5 pins for the same money.

[jamathi]

Here are two links you can try.

https://www.facebook.com/jan.thiel.9400/videos/733939527326518/
https://www.facebook.com/groups/265987933547445/permalink/2452311541581729/

The actual opening of the bottle is not in the video, but handing out the champagne (in plastic cups) is.

It was 1 of the better days in my life....

[Frits Overmars]

It was 1 of the better days in my life....There have been ups and downs, but I like to remember the ups, even the small ones. Like when you discovered that I could bake the best fries you ever tasted?
And the invention of my clock-driven parking disc that allowed us to leave the car in a one-hour-spot in Bergamo all day long .
And how we found five horsepower just by bypassing a coolant pump (must be our only good memory of that scrap-metal tout) :D.

[Muhr]

Muhr , one thing many dont realise is that the rod bores and the pin surfaces dont wear significantly at all.
I routinly replace the big end cage /rollers/washers 4 times in a crank using the same pin and rod.
Its the cage that eventually wears off the silver coating , allowing the rollers to skew , then skid then fail.
After 4 replacements you can just start to measure wear on the pin and rod bore - but hey , they are real smooth by that stage.

Yes, I guess you can run a connecting rod bearing for quite a long time under the right conditions. myself, I have been in the habit of switching with fairly dense intervals. It has been a precautionary measure that dealt with if the connecting rod was subjected to something like e.g. fatigue cracking, ductile fracture
or yielding that could affect the breaking limit of the connecting rod.
Probably completely unfounded in many cases.
However, we have done some tests recently where we stretch these limits, to see what you can learn.





I noticed the Pankle silly money capped small end pin in your post , this is easy enough to do youself if you can do the cad drawing and have the caps CNC machined , then laser welded in.
The laser guy here has a standard charge , and will do one or 5 pins for the same money.

Nice! I can imagine that they (pankle) must have had a similar approach.

[breezy]

A couple examples of incomplete knowledge.

First we "know" that a thin edge orifice plate has a coefficient of discharge of around 0.6 i.e. it flows terrible, and of course other unfavorable shapes have fairly poor coefficients as well.

Second we "know" that once a pressure ratio of about 0.528 is reached on the low pressure side of a non-diffused opening then decreasing the pressure on the low side further will not result in any additional mass flow.

This information is readily available, but it is incomplete. Both only apply to specific scenarios, and there are scenarios inside an engine where neither statement holds true. Some people know this, but I suspect it is not common knowledge ?

so... your exhaust findings.. you have a graph showing a close comparison to a two stroke exhaust pressure wave...without it looking like a two stroke exhaust pipe..is that a header shape or complete system . are you able to show this shape in a picture or? does the 4 stroke system have a length which is similar to 2t tuned length?

[OopsClunkThud]

A couple examples of incomplete knowledge.

First we "know" that a thin edge orifice plate has a coefficient of discharge of around 0.6 i.e. it flows terrible, and of course other unfavorable shapes have fairly poor coefficients as well.

Second we "know" that once a pressure ratio of about 0.528 is reached on the low pressure side of a non-diffused opening then decreasing the pressure on the low side further will not result in any additional mass flow.

This information is readily available, but it is incomplete. Both only apply to specific scenarios, and there are scenarios inside an engine where neither statement holds true. Some people know this, but I suspect it is not common knowledge ?


Been trying to model and optimize the shape of a single exhaust port (I know...) to utilize all the tips, tricks, and concepts brought up here, and I think I know the limitations you are referring to (would still be better to just come out and say it, rather than hint and see if anyone can figure it out). disclaimer: I'm no expert in compressible flow.

1. The 0.6 value is valid for incompressible fluids, but for compressible sonic flow the Cd of a sharp edged orifice goes to 1 as the pressure difference goes higher. so the sharp edge flows better through most of the blowdown phase. discussion of this can be found here: https://www.eng-tips.com/viewthread.cfm?qid=51260

2. the 0.528 value applies when the low pressure side is 0 (a vacuum), there is no lowering it lower. in that limited case the mass flow rate is choked. in all other cases it's the velocity that is choked, but changes in pressure can still get more mass through at a higher density. discussion of this can be found here (think it was linked some time earlier too): http://www.therebreathersite.nl/04_Links/Downloads/Choked.pdf

Also of note is that a thin orifice is never really fully choked. The fact that unlike an intake bell where the radius is outside the bounds of the port diameter, a radius applied to an exhaust port has to fall mostly inside the area of the port opening or it will change the timing.

I've started a simulation project to characterize the flow at pressure ratios we see from exhaust port open to the end of blowdown, as well as fully open at BDC. Figure having a working and validated simulation of a standard configuration that matches our conditions would be a good starting point for simulating actual exhaust ports. https://www.simscale.com/projects/OopsClunkThud/sonic_compressible_flow_through_an_orifice_plate_-_cfd/

Here are images of three exhausts, with square edge, rounded port top, rounded port top and piston edge. this led me down this rabbit hole.
348525
348524
348523

[wobbly]

Patrick , one concept I have always wanted to try on a single port ( very rare , work wise nowdays ) is to add concave hooks on the sides of the duct above TPO.
The shape as is common on T port outer edges - that increases considerably that ports Cd value.

[OopsClunkThud]

concave as in adding a side wall angle to the port as pictured below?

348526

If so, I've been trying to model this in engmod as a bridged exhaust with a 0 width bridge. Actually started down this path trying to figure out how much side wall angle to add. Clearly the effective port area would be between 0° side wall as the min, and a radial angle with the area of the curved port face (adjusted for down angle of 25%) for the max. I think that will be the last and largest part of this study.

[jamathi]

There have been ups and downs, but I like to remember the ups, even the small ones. Like when you discovered that I could bake the best fries you ever tasted?
And the invention of my clock-driven parking disc that allowed us to leave the car in a one-hour-spot in Bergamo all day long .
And how we found five horsepower just by bypassing a coolant pump (must be our only good memory of that scrap-metal tout) :D.

Nice memories indeed.....
But how was I stupid enough to go work for a metal scrap fool?
Mainly to help Daniele Agrati sell his 'reparto corse'....
While MANY people were telling me to go to Aprilia. for years.....
When I finally went there my 'dreams came true'
Many people working there, money enough!
But the nicest place I ever worked was DERBI, only that it was too small.
But I am really proud of the engine we made there....

[wobbly]

Frits , it immediately comes to mind only a Dutchman would use his brain hard enough to invent a clock driven parking disc.
Maybe sell the idea to KTM to patent it while they have a go at MK2 TPI.

[wobbly]

Muhr , theoretically the hook angle passing thru bore center would seem logical but CFD would sort that in no time.

[Muhr]

I guess this statement was intended for Patrick. I think exactly as you say that the center bore will not be far from the truth, then the question is how long in the cycle this will be a supplement. I guess as soon as you get an established negative pressure on the exhaust side, these "hooks" will probably be a dead space.
So simulating this you probably needs a transient simulation with the exhaust side and piston movement

[andreas]

To maintain the arched cross area of the port (which becomes an issue only when the port is almost fully open), why put the divergence (hooks) in the side walls, and not in the floor preferably, as it will eventually be a circular path?

[Frits Overmars]

Patrick , one concept I have always wanted to try on a single port ( very rare , work wise nowdays ) is to add concave hooks on the sides of the duct above TPO. The shape as is common on T port outer edges - that increases considerably that ports Cd value.
concave as in adding a side wall angle to the port as pictured below? If so, I've been trying to model this in engmod as a bridged exhaust with a 0 width bridge. Actually started down this path trying to figure out how much side wall angle to add. Clearly the effective port area would be between 0° side wall as the min, and a radial angle with the area of the curved port face (adjusted for down angle of 25%) for the max. I think that will be the last and largest part of this study.
....Theoretically the hook angle passing thru bore center would seem logical but CFD would sort that in no time.
.... I think exactly as you say that the center bore will not be far from the truth, then the question is how long in the cycle this will be a supplement. I guess as soon as you get an established negative pressure on the exhaust side, these "hooks" will probably be a dead space. So simulating this you probably needs a transient simulation with the exhaust side and piston movement
To maintain the arched cross area of the port (which becomes an issue only when the port is almost fully open), why put the divergence (hooks) in the side walls, and not in the floor preferably, as it will eventually be a circular path?I started playing with CFD when I was still young and handsome (I had to write my own software, it's that long ago) and it did, and still does prove Wobbly, Patrick, Muhr and Andreas right.
The initial hook angle passes through the bore center and the sidewalls will start as a circular path, but this path will almost immediately tighten, as the difference between the exhaust duct roof angle and its floor angle will take care of maintaining a rather constant cross flow area ('rather' because of some CFD finesses that may be outside the scope of this post).
In English: as the floor drops, the sidewalls should close in.
Maintaining the circular path would lead to an undesirable increase of the duct volume. I have been distributing a couple of sketches which show the 20° difference angle that also appeared in Patricks drawing, instead of the initial radial angle, because that hopefully reduces the number of cylinders ruined by overzealous hookers tuners.
348550 348549

Below: an exhaust duct solid, modelled from the points cloud generated by my CFD, and a pair of cut-away pics showing the dropping floor and the closing-in sidewalls of the twin exhaust ducts in my cylinder.
348554 348553 348552 348551

[Muhr]

It's a bit hard core to code your own CFD. But what do you do if the only ones who have access to it are NASA :not:.I have tried to find info on how it went with that project, I think if I remember correctly I saw a picture of a cylinder. Also high interesting to hear more from a perspective on the raised exhaust port floor.

[OopsClunkThud]

Frits, in your CFD results did the radial alignment of the hook flow better than the 20°? I had assumed that the 20° came about as a balance of the initial radial outward expansion vs the developing flow velocity down the exhaust.

To make sure the port is maintaining a constant taper rate (from port area down to the ~90% or whatever value is settled on in engmod), I've placed sketches at the .25, and .5 bore distance along the path. These have a target area based on position and with the top and bottom shape of the port fixed, the needed width can then be found. From those widths a smooth path for the rails that form the hooks can be found and then the final lofted shape can be formed.

348555

I'll try and write these steps up like Lohring did with the "3D Engine Modeling.pdf"

Thanks for all the guidance from everyone!

[Frits Overmars]

Frits, in your CFD results did the radial alignment of the hook flow better than the 20°? I had assumed that the 20° came about as a balance of the initial radial outward expansion vs the developing flow velocity down the exhaust.It was fractionally better at outflow and definitely worse at reverse flow. Makes you think twice about transfer duct hooks....The 20° also helped to keep the exhaust duct volume small.


To make sure the port is maintaining a constant taper rate (from port area down to the ~90% or whatever value is settled on in engmod), I've placed sketches at the .25, and .5 bore distance along the path. These have a target area based on position and with the top and bottom shape of the port fixed, the needed width can then be found. From those widths a smooth path for the rails that form the hooks can be found and then the final lofted shape can be formed.The only 'taper' I used came from the radiused exhaust port top edge and the radiused piston timing edge; between them they gave a rather nice impersonation of a De Laval nozzle.
Downstream I used a 3° divergence. The tapering comes from Wobbly's experience in making the best use of a conventional exhaust duct. It certainly works in those circumstances, but mine were different, wich a much higher than conventional exhaust floor.

[wobbly]

The only caveat I have seen about lifting the port floor ( thus the reason I havnt been down that path as yet ) is that Jan mentioned to me lifting the floor only worked
as long as the Aux ports were fully optimised ( around to bore center ) to achieve the Blowdown needed for the power produced.
As a single port is always going to be inherently Blowdown limited , I would be carefull .

The other point I have kept in mind ( as the KZ engines I work mostly on are certainly not yet Blowdown optimised - maybe soon with my new Pankle pin copies ) is that Jans
actual documented floor lifting experiments ceased at + 3mm . So as yet there is no documented dyno proof I have seen , that going higher is beneficial.

[Frits Overmars]

The only caveat I have seen about lifting the port floor is that Jan mentioned to me lifting the floor only worked as long as the Aux ports were fully optimised ( around to bore center ) to achieve the Blowdown needed for the power produced.Wob, as you may have noticed in the above pics, my symmetrical scavenging cylinder has abundant total exhaust port width. At 190° exhaust timing and 130° transfer timing it has clearly more blowdown STA than the corresponding transfer STA, so the transfers set the optimum rpm, with a save blowdown reserve for overrev. The Aprilia RSA does not have such a reserve, and raising the exhaust floor to above the transfers, as I have done, would create serious problems. But I think that for the RSA an exhaust floor 10° below the top of the transfers should leave sufficient blowdown reserve for overrev.


The other point I have kept in mind is that Jans actual documented floor lifting experiments ceased at + 3mm . So as yet there is no documented dyno proof I have seen , that going higher is beneficial.That documented proof is not available because Jan went into retirement. He had planned to carry on experimenting with higher floors and the cylinders for those experiments had already been cast when Jan realised that he would be gone before he could test them, so he cut those floors down in order to prevent certain people from claiming future improvements as their own.

[TZ350]

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More from 2 Stroke Stuffing.
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<iframe width="560" height="315" src="https://www.youtube.com/embed/u4CImEwPt00" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[Muhr]

The only caveat I have seen about lifting the port floor ( thus the reason I havnt been down that path as yet ) is that Jan mentioned to me lifting the floor only worked
as long as the Aux ports were fully optimised ( around to bore center ) to achieve the Blowdown needed for the power produced.
As a single port is always going to be inherently Blowdown limited , I would be carefull .

The other point I have kept in mind ( as the KZ engines I work mostly on are certainly not yet Blowdown optimised - maybe soon with my new Pankle pin copies ) is that Jans
actual documented floor lifting experiments ceased at + 3mm . So as yet there is no documented dyno proof I have seen , that going higher is beneficial.


This with raised exhaust port floor keeps me awake in the evenings sometimes, I put exhaust 2.2mm over transfer floor on my little 50cc hobby project, I can only assume that you lose a lot of top if this would be a failed attempt?
Have also had some trouble with the weight of the crank assembly, have now ordered materials that I will pick up tomorrow to make the balance shaft and rotor shaft in titanium. Do not know if it was a particularly good idea but I guess I will get answers. have not dared to start macining the cast parts before I got control of all the small parts

[jamathi]

Wob, as you may have noticed in the above pics, my symmetrical scavenging cylinder has abundant total exhaust port width. At 190° exhaust timing and 130° transfer timing it has clearly more blowdown STA than the corresponding transfer STA, so the transfers set the optimum rpm, with a save blowdown reserve for overrev. The Aprilia RSA does not have such a reserve, and raising the exhaust floor to above the transfers, as I have done, would create serious problems. But I think that for the RSA an exhaust floor 10° below the top of the transfers should leave sufficient blowdown reserve for overrev.

That documented proof is not available because Jan went into retirement. He had planned to carry on experimenting with higher floors and the cylinders for those experiments had already been cast when Jan realised that he would be gone before he could test them, so he cut those floors down in order to prevent certain people from claiming future improvements as their own.


Now I regret very much not to have left those cylinders with raised exhaust port floor to my successors, at least the result would have been known now, 12 years later....
But I don't understand why nobody else had the same idea!
It just takes 1 day of testing...
If successful there would have been more room for the transfers..

By the way Frits, how did your cylinder run? Any test results?
Someone else had the same idea: it would not rev at all.....
Was yours any better?
Blowdown was certainly enough!
I liked the design very much when I first saw it!
But some people tried it without result...

[Frits Overmars]

By the way Frits, how did your cylinder run? Any test results?
Someone else had the same idea: it would not rev at all. Was yours any better?
Blowdown was certainly enough! I liked the design very much when I first saw it! But some people tried it without result...Wasn't that the same 'someone else' who claimed he was the only person who knew everything about the Ryger and who publicly wrote: "Jan Thiel doesn't understand how a two-stroke works" ? :msn-wink:

[dutchpower]

Why your cil.is stil on the shelf by Harm Frits :headbang:

[jamathi]

Wasn't that the same 'someone else' who claimed he was the only person who knew everything about the Ryger and who publicly wrote: "Jan Thiel doesn't understand how a two-stroke works" ? :msn-wink:

Yes, the same person, now the RYGER has died......
He sent me a video to show his 'system' worked.
Later it did not rev.
Was yours any better, or was it never tried at all....?
And what are your thoughts about the RYGER now, now that you can safely talk about it? You once tried it, on a kart, you were very enthusiastic.....
But it never achieved anything at all....!!!

[jamathi]

Why your cil.is stil on the shelf by Harm Frits :headbang:

Yes, why?? Is nobody interested in trying it?
I am very curious to see if it works or not....

[Frits Overmars]

Yes, why?? Is nobody interested in trying it?
I am very curious to see if it works or not....That is not the cylinder we are working with, Jan.

[dutchpower]

Still its on the shelf Frits Both !!!!!

[41juergen]

A friend of mine has built a NS500R with a tuning kit from DMR out of Japan. The bike is equipped with Jim Lomas pipes, has the stock CDI and the stock reeds / carbs / air boxes. During first tests on the dyno the exgas temps (200 mm behind piston face, measured with a 1,5mm type K thermocouple) raised up to 620°C at approx. 9000 rpm and an AFR of approx. 12,7. So he was afraid of too high exgas temps and went richer on the mains until reaching an AFR of approx. 11.2! BUT the exgas temps were not decreasing, not 10°C. So we checked the stinger diameter and found an inner diameter of 22 mm, that with a measured power of approx. 66 rWHP (measured on a Dynojet). I have put that project into EngMod and the prediction is approx. 36 crank HP per cylinder, (so only a mid bmep) ending up with approx. 108 HP.
So any idea why the exgas temps are not decreasing when going rich?

[Tim Ey]

Hi Jürgen,

with a 1.5mm thermocouple sitting 200mm behind piston face, 620°C is not alarmingly high for my gut feeling.

Where do you measure AFR?

As a first guess what might be wrong: I would check the ignition timing.

[41juergen]

Hi Jürgen,

with a 1.5mm thermocouple sitting 200mm behind piston face, 620°C is not alarmingly high for my gut feeling.

Where do you measure AFR?

As a first guess what might be wrong: I would check the ignition timing.

Hallo Tim, the problem is not the 620°C at 9000rpm, the problem is that the temperature rises further on until 11000 rpm up to 700 °C. And the strange thing is, that going bigger with the mains the temp does not go down (he started with one size bigger, than a next bigger until AFR reached 11.2). He is using Bosch wide band sensors , getting the exhasut being sucked through a copper pipe being inserted through the silencer and the stinger into the pipe. We did a back to back test with my data logger having the lambda sensor mounted approx. 300 mm behind the piston face showing very close results in lambda.
The igniton curve is the stock NS400R one, having 15°CA at 10000 rpm and 12°CA at 11000 rpm...

[Frits Overmars]

...The problem is that the temperature rises further on until 11000 rpm up to 700 °C. And the strange thing is, that going bigger with the mains the temp does not go down (he started with one size bigger, than a next bigger until AFR reached 11.2). He is using Bosch wide band sensors , getting the exhasut being sucked through a copper pipe being inserted through the silencer and the stinger into the pipe.Maybe that copper pipe creates too much of a restriction in the stinger.

[wobbly]

The issue sounds like a combination of factors.The probe is too far into the header for a start. 3X bore from the piston face is the rule of thumb , and the probe must be an exposed tip and sitting exactly on
the header centerline. Having a short probe down the header will absolutely read high.
Pulling more timing out past peak Hp makes the egt continue to rise , and you end up using fuel to cool the temp , rather tha make power.

The way to fix this is to retard only enough as is needed just past peak , then flat line , this stops the egt continually going up.
If it wont rev without a heap of retard the pipe is too long - and a better way to make it rev is a solenoic powerjet.

The only place that gives reliable Lambda readings without affecting the backpressure is at the beginning of the muffler .
I weld a fitting onto the muffler can , with an extended tube the OD of the perforated , and scallop the tube end to sit over the perf tube.
Then the Lanbda sits in this " pocket " fed continually thru the perf holes.
Going thru the stinger into the pipe makes a joke of the work done in EngMod tracking the Mach in the tube to optimise the area.

[41juergen]

Wob, to make sure I understand correctly: the temp measuring probe sits 200 mm behind piston face (with a bore of 66mm that should be ok, right?) and of course in the centerline (learned that at the company when doing some test 25 years ago ;) )
My friend did tests with and w/o the copper pipe in the stinger with no significant effect (in power and temps). However, my guess is still the stinger, even it has a 22 mm diameter.

But the most courius thing for me is: What else could be a reason that when going bigger with the mains no change in EGT can be seen?

Regarding the probe position for the AFR measurement, I did a test on my bike having one sensor approx. 250mm behind piston face (in the header), the other as you mentioned in front of the muffler in a short pipe with a slightly bigger diameter (to get the same free cross sectional area), unfortunately the battery had not enough power to heat both sensors, but up to where the heater stopped the signal were pretty much the same...

[katinas]

Hi, juergen

NS 400 stock ignition timing curve is too advanced for correct squish height ( 0.8 mm /1 mm). Std NS 400 squish from factory variate from 1.8 to 2 mm with aprox 15,5 cc head volume with plug hole.
I dont know exactly, but DMR cylinder heads volume looks like too small, with very wide squish band.
Some time ago, when I started endless testing with NS engine, first things was to correct squish height to 0,9 mm and 13.5 cc volume with std cylinders and heads. And gains in upper range, comes only after retarding std ignition with additional plate (add photo ). Very important too harmonized ignition and new 500 cc set up before goes deeper. But of course first thing after 500 cc kit, must be zeeltronic or ignitech ignition. They made nice special kits for NS 400.

Very interesting about head volume on 500 cc kit.

[Condyn]

Do you guys think this pipe would be worth a try? My target peak rpm is 10,000. This is a vintage piston port, single exhaust port, 450cc parallel two cylinder snowmobile engine with a CVT. Exhaust duration is 202° with 35° blowdown. I have physically built 6 sets of pipes for this particular engine thus far and they are all worthless. None look anything like this pipe. Some longer, some shorter, most fatter. Based on the minimal info I am providing, is there anything with the design that stands out and screams “you are wasting your time!” Normally I would just build them, and try them, 348575but my ego is already dwindling at this point.

[andreas]

I'll venture a suggestion. The pipe starts at 45, if this is because the duct ends ,and will always do so, at 45, fine. If the duct size can be altered, it seems to me that this 225 cc single port will work better with about 40 mm d0. The diffuser is nice and shallow, maybe the d max can be reduced even more, who knows. Variable transmission, consider a steeper baffle, perhaps a multi stage.

[Condyn]

You are right. The d0 is a screw up on my part and I will correct that. It is supposed to be 41mm. I did that on this pipe only because It uses slip over pipe flanges with spring mounts. The large 50mm OD of the flange makes it a little more time consuming to make the slip joint. So I was foolish and enlarged the d0. I understand that was improper. I will correct it and maintain the header angles. You think my diffuser proportions and angles are feasible, and in the right approximation? As for the rear cone, I could extend the dwell and make the baffle steeper. Something like 23°? Thanks for the suggestions.

[andreas]

Yes 23*, possibly up to 30*. It's easy to go back if it doesn't work, remember the reflection point "pivots" maybe 3/5 down the cone, not the absolute end.

[wobbly]

Condyn everything is wrong with the design - send me the pack file . PM me for email.

[jonny quest]

Do you guys think this pipe would be worth a try? My target peak rpm is 10,000. This is a vintage piston port, single exhaust port, 450cc parallel two cylinder snowmobile engine with a CVT. Exhaust duration is 202° with 35° blowdown. I have physically built 6 sets of pipes for this particular engine thus far and they are all worthless. None look anything like this pipe. Some longer, some shorter, most fatter. Based on the minimal info I am providing, is there anything with the design that stands out and screams “you are wasting your time!” Normally I would just build them, and try them, 348575but my ego is already dwindling at this point.

Run 32% hdr 3deg total. 66%total diffuser and a pretty short tailcone 30ish included angle.

Don't try an get fancy with sharp diffuser angles, somewhere around 7 first, 13 second, 15third. Adjust 3stage lengths to sort of end up close to those angles.

Probably a 4.5" to 4.7" center diameter

[Condyn]

Thanks, That results in a very different pipe than I am used to seeing with a very stubby baffle cone.
348579

[andreas]

Somehow the 7.2 taper is now incuded in the header, just go 3* for 32%. And also when the tuned length is measured at the end of baffle it have to be shorter when the cone is shortened, it can be converted by using to the center of cone length ,sort of. Or let Wobbly sprinkle som magic over it.

[Condyn]

The 7° angle is the first diffuser, not the header on the second pipe, and 1% shorter than the first pipe. I will be rolling cones until I am blue in the face at this rate. And yes, the magic is being sprinkled.

[41juergen]

Hi, juergen

NS 400 stock ignition timing curve is too advanced for correct squish height ( 0.8 mm /1 mm). Std NS 400 squish from factory variate from 1.8 to 2 mm with aprox 15,5 cc head volume with plug hole.
I dont know exactly, but DMR cylinder heads volume looks like too small, with very wide squish band.
Some time ago, when I started endless testing with NS engine, first things was to correct squish height to 0,9 mm and 13.5 cc volume with std cylinders and heads. And gains in upper range, comes only after retarding std ignition with additional plate (add photo ). Very important too harmonized ignition and new 500 cc set up before goes deeper. But of course first thing after 500 cc kit, must be zeeltronic or ignitech ignition. They made nice special kits for NS 400.

Very interesting about head volume on 500 cc kit.

Hi Katinas, the combustion volume of the DMR setup is approx. 10,7ccm with a squish band of 11.8 mm. With a squish of 0,9 mm that gives a MSV of 38,9 m/sec at 10.000 rpm (I know, a little bit high maybe).
Do you have detailed data of the stock ignition curve for the NC19?
Re the exgas temps not going down when going rich: I played a bit more with the sim and Wob might smile, I think the problem are the Jim Lomas pipes. They were designed for the stock NC19 with a belly diameter from only 102 mm. So for me it looks like that the pipe volume is too small. When using a 120 mm belly even a 22 mm stinger venturi brings the temps down to an expected level....

[SwePatrick]

Today the weather finally approved for some 'opengaragedoorthingstodo' ;)

Dyno!! =)

I have this winter setup a simple nitroussystem just to add some power if needed, today was the day to test it.
Graph below is a comparison between 'best curve no nitrous run' and a short burp nitrous run.
Result: 98.4Hp to the crank.

I run the system totally pump less, and by that i shoot the nitrous dry and have a couple of homemade powerjets activated by a solenoid fed directly from the tank above them, gravity and ejector pulls the fuel from the tank.
I setup the jets for the nitrous to add 15hp, it became 12.9hp running a tad rich, but i´m happy with how nice it worked without fuelpump, and i can always tune off a little bit of fuel at the track when having more at stake, so to speak ;)

I also don´t purge the nitrous, this to make a 'soft hit' as the fuel takes a little time for it to reach the carbs bore.
I figure this is easier on the engine also.

As the pipes were always tuned to give peak at 12000rpm with nitrous i´m happy that the seem to do just that, i chickened out and let off the throttle just at 11700rpm :eek: :nono: :weird:

I use ignitech to control it, no need for doing anything, it is activated above certain rpm and above certain throttle.

How much nitrous do you people think is possible to run?
20? 30? 40hp?
This was with the smallest jets i could find.

I have also updated the dyno software between the runs, this makes the 'before run' have a another smoothing setup.

348582

[palezu]

I'm designing a new 50cc cylinder to be cast. Currently working on the water jacket. Almost done, but I started to wonder around about the placement of the inlet nipple near the exhaust duct, or rather should it be the inlet or outlet nipple. Would it be beneficial to have the water flow in "reverse" direction, to have the water enter from the head above boost port, then flow around cylinder to the exhaust duct jacket and then exit upwards right before the pipe adapter? I have read about wobbly's trials of reversing the water flow, but I'm not sure if the routing was comparable to this. I think the KZ has the water entering from the case, but I don't have this option.

I think it would make sense, it would follow the natural thermal gradient of the cylinder that the exhaust is always hotter. If the cold water entered the exhaust first, it would shift the balance and more like move the heat from exhaust into the cooler side of the cylinder. Of course we want to keep the cylinder head portion the coolest. If this is a good idea, then I can make the exhaust water core have the outlet upwards above the exhaust duct and not sideways.

[F5 Dave]

Wob has explained this a few times if you search back. Put it in the back of the barrel first.

[katinas]

Hi Katinas, the combustion volume of the DMR setup is approx. 10,7ccm with a squish band of 11.8 mm. With a squish of 0,9 mm that gives a MSV of 38,9 m/sec at 10.000 rpm (I know, a little bit high maybe).
Do you have detailed data of the stock ignition curve for the NC19?
Re the exgas temps not going down when going rich: I played a bit more with the sim and Wob might smile, I think the problem are the Jim Lomas pipes. They were designed for the stock NC19 with a belly diameter from only 102 mm. So for me it looks like that the pipe volume is too small. When using a 120 mm belly even a 22 mm stinger venturi brings the temps down to an expected level....

It was long time ago when I measure ignition curve of std NS400 (NC19 ) and NS250 (MC11) and now can’t find these graphs.
From memory, both graphs started immediately at highest advance angle and holds steady until approx. 6000-6500 rpm (just before ATAC chamber closes) , then gradually retarding.
Difference between 400 and 250 cdi is that on 250, after 10500 rpm spark timing retarded drastically and drop of the operating range, this work like rev counter.
NS400 cdi didn’t have this restriction and holds some advance until 13000 or maybe more rpm. Other thing is, that NS 250 cdi generated weak spark, so engine is very sensitive to mix.
NS400 cdi is opposite, generate very strong spark that tolerate very rich mix.
Both generators flywheels are “criminally” heavy for such engines.

Very interesting about DMR head volume for 500 kit, thanks. DMR still made very nice things for NS/NSR street engines.
If its really 10.7 cc it is about 16.5 compression, looks too much for 166 cc, even on avgaz.
It looks like need to be very careful with this nice kit, as bore raised from 57 to 64.7 mm. Very interesting how your test goes.

I tried six different shape pipes for NS 250/400 engines ( single exhaust window) and every time the best was Honda RS125/250 copy, with 120 mm belly, just playing little with header length for lower rpm.

I still trying to adapt Honda RS125/250 cylinders to NS 400 engine with and 54 mm stroke crank with direct flow to transfers. Its not too much left, but small things usually needed time.

[RAW]

[QUOTE=wobbly
I noticed the Pankle silly money capped small end pin in your post , this is easy enough to do youself if you can do the cad drawing and have the caps CNC machined , then laser welded in.
The laser guy here has a standard charge , and will do one or 5 pins for the same money.[/QUOTE]

The Pankle pins are not laser welded, further the performance gain may not entirely be due to the capped ends.

[RAW]

Seems like somebody forgot to tell Neil Hintz :msn-wink:
348488 348487 348485 348486348489

Dolph has suggested to me that an in-line 250cc 256 type styled engine can be sufficiently balanced to be used upon a superkart.
What’s Your opinion Frits 🤷*♂️

[Frits Overmars]

Dolph has suggested to me that an in-line 250cc 256 type styled engine can be sufficiently balanced to be used upon a superkart.
What’s Your opinion Frits?As far as I know all 250 cc Superkart-twins use that type of inline engine. But those are all counter-rotating simultaneously-firing twins, perfectly balanced with 100% balance factor for each crankshaft. The discussion with Wobbly was about inline twins that were not counter-rotating and/or not simultaneously-firing.
Did Dolph say anything about those cases?

[RAW]

As far as I know all 250 cc Superkart-twins use that type of inline engine. But those are all counter-rotating simultaneously-firing twins, perfectly balanced with 100% balance factor for each crankshaft. The discussion with Wobbly was about inline twins that were not counter-rotating and/or not simultaneously-firing.
Did Dolph say anything about those cases?

Hello Frits, sorry, a lack of information on my part. Yes Dolph was referring to a counter rotating in-line twin with a 180* firing order

[TZ350]

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More from the genius of two stroke stuffing.
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[ken seeber]

The Pankle pins are not laser welded, further the performance gain may not entirely be due to the capped ends.

Rick,
I seem to remember someone, was it Jan, say they were laser welded and very expensive. Assuming they were hollow, then they must have been made in multiple parts which are then welded, pressed or bonded together. Maybe there is some other magic out there though. I think Wob’s design is utilising the standard pin, so some form of retention is required and, in his case, no distortion of the OD of the pin

If the circlip is to be accessed to allow pin removal, then one could assume there would need to be sufficient annular gap to achieve this. Despite its end having a spherical and tight clearance to the bore, close. It could never be as good as a form fitting pin or plug. I believe Wob is on the case to make a comparison.

Any form fitting pin or plug needs accurate indexing and axial location.

Can't think of any other way the pin could change the performance, other than less short circuiting, change of mass or sealing off the central volume of the pin.

https://www.mondokart.com/en/engine-accessories-mondokart/lke-lenzo-mondokart/pistons-lke-mondokart-karting/cap-for-piston-pin-60cc.html?search_query=piston+pin&results=147

348597348598

[RAW]

As far as I know all 250 cc Superkart-twins use that type of inline engine. But those are all counter-rotating simultaneously-firing twins, perfectly balanced with 100% balance factor for each crankshaft. The discussion with Wobbly was about inline twins that were not counter-rotating and/or not simultaneously-firing.
Did Dolph say anything about those cases?

Hello Frits, sorry I failed to provide adequate information
I was referring to taking an in-line engine such as the Rotax 256 or any of the modern variants such as the ( BRC, DEA, PVP, FPE & or VM ) counter rotating engines and phasing the crankshafts & firing to be 180* as opposed to the Big Bang configuration for use in a superkart.
My conversations with Dolph upon this concept & his subsequent crankshaft balance equations upon this with the crankshaft data I supplied him, he suggests that a reworking of the crankshafts counterweights would produce a satisfactory configuration by which performance in both power & component longevity would be not detrimental against the standard configuration.
I have touched upon this subject with yourself on the pit lane forum previously,
I like the idea of something different ( a screener engine ) however if there is to be a power & or reliability loss I do not see a point to it,
You have an elegant way of explaining thing as an integrated unit for itÂ’s intended use that a layman can envisage, would you enlighten me given your knowledge & intellect upon this concepts pros & cons etc.

[RAW]

[QUOTE=ken seeber;1131182602]Rick,
I seem to remember someone, was it Jan, say they were laser welded and very expensive. Assuming they were hollow, then they must have been made in multiple parts which are then welded, pressed or bonded together. Maybe there is some other magic out there though. I think Wob’s design is utilising the standard pin, so some form of retention is required and, in his case, no distortion of the OD of the pin

Hi Ken, I have several of the Pankle pins ( non stepped variant ) Inspection / reverse engineering informs me that laser welding was not used with the flat ended versions, perhaps the stepped ended variant was however I doubt it given what I have seen & understanding the cost of manufacturing a pin the way Pankle has Vs a laser process.
Subsequent usage & inspection at regular periods of the Pankle pin shows the superior performance of this pin over numerous other manufacturers pins. As I indicated there is more to the Pankle pin than the closed ends that is responsible to any performance gains in my opinion.

[Frits Overmars]

Hello Frits, sorry I failed to provide adequate information
I was referring to taking an in-line engine such as the Rotax 256 or any of the modern variants such as the ( BRC, DEA, PVP, FPE & or VM ) counter rotating engines and phasing the crankshafts & firing to be 180* as opposed to the Big Bang configuration for use in a superkart. My conversations with Dolph upon this concept & his subsequent crankshaft balance equations upon this with the crankshaft data I supplied him, he suggests that a reworking of the crankshafts counterweights would produce a satisfactory configuration by which performance in both power & component longevity would be not detrimental against the standard configuration. I have touched upon this subject with yourself on the pit lane forum previously, I like the idea of something different ( a screener engine ) however if there is to be a power & or reliability loss I do not see a point to it. You have an elegant way of explaining thing as an integrated unit for itÂ’s intended use that a layman can envisage, would you enlighten me given your knowledge & intellect upon this concepts pros & cons etc.
348599 348600

The left side of the left-hand picture shows the classic counter-rotating simultaneously-firing inline twin. When both pistons are in TDC or in BDC, their inertia forces V are 100% balanced by the forces B from the crank web masses. This requires a 100% balance factor per crankshaft, as the heavy-metal concentrations in the photograph demonstrate.
When both pistons are about halfway down, their inertia forces V are zero (no acceleration) and the big crankshaft forces B cancel each other out. That's great: no free forces and no vibration in any direction.

If you time these crankshafts at 180°-firing as in the right side of the left-hand picture, at the pistons-halfway position the forces B both act in the same direction; they reinforce each other, and the engine will vibrate strongly in the horizontal plane, though it will still be vibration-free in the vertical plane.

You can reduce the forces B and so reduce the horizontal vibrations, but then the vertical forces V will no longer be completely compensated by the forces B, like in a single-cylinder engine without a balance shaft, where you accept some horizontal vibration in order to reduce the vertical vibration, or vice versa.

The difference between a single and a twin is that the vertical forces V in this 180°-firing counter-rotating inline-twin counteract each other, no matter how big they are, so you could give this engine a zero % balance factor, thus completely eliminating the forces B and their horizontal vibration. This only leaves a torque, caused by the vertical forces V, multiplied by the horizontal center-to-center distance between the two cylinders, which is trying to rock the engine around its transverse axis.
In this respect, the situation is similar to a 180°-firing transverse twin without a balance shaft, where the unbalanced parts of the V-forces are rocking the engine around its longitudinal axis, while the B-forces are rocking it around its vertical axis.

Maybe the vibration of this resulting torque, rocking the 180°-firing inline engine around its transverse axis, is acceptable if the smoother engine torque of the 180°-firing permits the use of softer tire compounds. If we didn't have this damned Covid I'd go and have a cup of coffee with Dolph. It's always a joy to sharpen our minds together.

[Muhr]

Rick,
I seem to remember someone, was it Jan, say they were laser welded and very expensive. Assuming they were hollow, then they must have been made in multiple parts which are then welded, pressed or bonded together. Maybe there is some other magic out there though. I think Wob’s design is utilising the standard pin, so some form of retention is required and, in his case, no distortion of the OD of the pin

If the circlip is to be accessed to allow pin removal, then one could assume there would need to be sufficient annular gap to achieve this. Despite its end having a spherical and tight clearance to the bore, close. It could never be as good as a form fitting pin or plug. I believe Wob is on the case to make a comparison.

Any form fitting pin or plug needs accurate indexing and axial location.

Can't think of any other way the pin could change the performance, other than less short circuiting, change of mass or sealing off the central volume of the pin.

https://www.mondokart.com/en/engine-accessories-mondokart/lke-lenzo-mondokart/pistons-lke-mondokart-karting/cap-for-piston-pin-60cc.html?search_query=piston+pin&results=147

348597348598


I wonder where the first photo comes from?

I'll cut one to pieces when I get home to try to understand what's so special about a Pankel

[andreas]

Frits, I liked your pipe article series, maybe there can be a collectively done translation of it, but now I cant find it. It's gone?

[wobbly]

Answers to a few questions - the best way to route water , and this has been tested on a KZ kart engine , up to a TZ750 classic racer , is to pump the cold water in over the boost port.
This then flows forward over the transfers , then picks up the greatest heat load around the Exhaust duct , then passes up into the head.
The head is a catch 22 in that you want to cool the plug thread and squish area as much as possible , but keep the comustion chamber only , hot , to reduce throwing burn energy away via a big temp delta to the water.

I have dyno tested several versions of pin plugs in KZ engines , the latest being the laser welded tophat type , that allows stock pins and clips to be retained.
The first test was a full piston pin hole cover , with indexing , in plastic Torlon that utilised the clip for retention ( thanks Ken ).
This was worth about 1/2 Hp on a stock Aux port that had little port linking anyway.
But with very much enlarged Aux ports ( around to bore center ) the difference was closer to 2 Hp average.
But after two race meetings the lack of lubrication access from the transfer flow , into the piston /pin bearing area , caused the pin surface to turn blue.

Next test was a simple cap , laser welded slightly inside the pin end , this had maybe 0.25 Hp on a stock cylinder and 0.75 Hp down low on a big port cylinder ( they fell out as well ).
So caps operating just as a method of removing the pin interior volume from the system , worked , but achieved little.
Now I have just tested the top hat pins , beautifully laser welded , and these , with a new design big port cylinder were worth between 3.5 @ 10.000 and 1.5 Hp @ 14000 - no contest.
In the weekend just gone this traslated into 0.3 sec lap time reduction.

Re the Tandem twin balancing . Frits has detailed it all well as he would . Its impossible to run a Tandem at 180 , Kawasaki did it first here in NZ testing , the bike was absolutely impossible to ride , as Ballingtons/Mamola's
hands and balls went to sleep , and worse , it fell to bits.
A balance shaft is needed , but this adds inertia plus friction , and the 180 screamer firing achieves nothing.
The best layout ( for a bike ) I believe is a big parrallel twin ( KTM 250 GP ) but turn the cylinders around , and then add twin RV across the front driven by the balance shaft , needed anyway for 0-90 firing.
Using Flets RV gib system , then adds a huge bunch of power , and can then be used to delete the carb slide. Mk2 TPI will be designed into the castings , once TZ350 tells me how to control the ECU on a road race engine.
Dr Henise is CAD drawing this engine around my EngMod and sketch files as we speak.

[husaberg]

It would be intersting to find out why the Kawasaki designers used a 180 firing order for the KR250 tandem road bike.
Maybe they liked the sound better, but they must have had a reason?
https://cdn.thumpertalk.com/uploads/monthly_01_2014/post-304988-13900984576292.jpg
https://enoanderson.files.wordpress.com/2014/09/skema-tandem-twin.jpg

Long term with a big bang contra-rotating primary does that mean the primary gear wears faster?

[SwePatrick]

The best layout ( for a bike ) I believe is a big parrallel twin ( KTM 250 GP ) but turn the cylinders around , and then add twin RV across the front driven by the balance shaft , needed anyway for 0-90 firing.
Using Flets RV gib system , then adds a huge bunch of power , and can then be used to delete the carb slide. Mk2 TPI will be designed into the castings , once TZ350 tells me how to control the ECU on a road race engine.
Dr Henise is CAD drawing this engine around my EngMod and sketch files as we speak.

Yamaha 3ma engine is equipped with balanceshaft and have the cylinders turned 180 degrees, also an alternative?

[Frits Overmars]

... usage & inspection at regular periods of the Pankl pin shows the superior performance of this pin over numerous other manufacturers pins. As I indicated there is more to the Pankl pin than the closed ends that is responsible to any performance gains in my opinion.
I'll cut one to pieces when I get home to try to understand what's so special about a PanklFound this in my Aprilia documentation and I wouldn't be surprised if this drawing originated on a Pankl drawing board.
348605


Frits, I liked your pipe article series, maybe there can be a collectively done translation of it, but now I cant find it. It's gone?I'm glad you liked them Andreas, but those articles are from 1978 / 1979, so their value today may be historical rather than technical. Most of what I wrote back then is still true (that is the nice thing about the laws of physics as compared to politics) but with today's knowledge I feel that some important aspects were incomplete, so I would not bother translating it myself now. And as the perfectionist that I still am,
I probably wouldn't be satisfied with a translation by someone else. That is the downside of perfectionism: you think there is always room for improvement, which is a perfect recipe for a burnout.
Been there, and once is enough.

[andreas]

Right, got it.

[Muhr]

Found this in my Aprilia documentation and I wouldn't be surprised if this drawing originated on a Pankl drawing board.
348605


It turned out to be something like this. unfortunately no magic dust when it was opened. But appears to be welded in gas, such as a chamber or laser given the lack of signs of high temperature on the inside

[SwePatrick]

You probably need to weld it inside a gaschamber as when you trap air inside it might be hard to seal up, as air want´s to escape due to it gains volume when hot, and thereby became a problem getting the last dime done.

[katinas]

Another interesting pin with usual conical shape on the both sides, but with approx 1.5 mm steps at the ends. This pin from Yamaha 500 latest 2002 version OWK1 with Honda style exhaust. Marks on piston shows that sides of exhaust windows not overlapping with piston pin hole.

[Flettner]

My tandem engine, same direction, 180 firing, was smooth enough. BUT the torsional loads on the small drive gears were too high. Kept busting gears. So I gave up and just built a 180 degree, case reed, parallel twin with a balance shaft. Smooth, reliable and flyable.

But now I'm thinking V twin version of this, not for aviation though. https://youtu.be/mS0cyt7F9js,

[TZ350]

.
More Two Stroke Stuffing.
.
<iframe width="560" height="315" src="https://www.youtube.com/embed/c92CQuHdP1Q" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

[TZ350]

.
Ok, so its not a 2 stroke but at least it is not a 4 stroke.
.
<iframe width="560" height="315" src="https://www.youtube.com/embed/03Kb5r7MHXE" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[Frits Overmars]

Ok, so its not a 2 stroke but at least it is not a 4 stroke.Lovely video. And let me put your mind at ease: it's an external-combustion double-action TWO-stroke. You can tell even without looking inside the engine: everything that's moving, moves with the same frequency as the piston. No half-rpm camshafts or excentrics here. Double action means that the steam pressure acts alternately on the top and bottom of the piston. Maybe we should even call it a ONE-stroke: labor delivered at every stroke. Which is better than what we have (until Fletto comes up with yet another wonderful creation).

And don't you love it when after his ride he drops the external combustion on the street? If it were my bike, I would alter just one thing: the water and steam outlets as he takes the pressure off the kettle.
I would aim those outlets so that they would piss out the fire between the wheels :D.

[wobbly]

So here is a pipe optimised for a piston port cylinder drag racing with a CVT.
Most all piston port cylinders have crap transfer ducts that cannot be " fixed " except for introducing stagger and remedial work on the radial angles to help
chronic short circuiting that occurs with anything even approaching a modern diffuser design.

These old engines like a long header , much longer than we would even think of using today , as this helps to delay the depression formed around BDC , allowing the transfer streams to at
least make a start up the Leaning Tower before being overcome , and creating a big loss in Trapping Efficiency.
The mid section is as fat as I dare go , and its very long due to the steep rear cone.

The two stage rear cone is a compromise , that allows good front side power , giving hard acceleration against the gradually locking clutch , but also allowing some overev past a high peak that occurs
at the end of the run. A single steep cone would lack front side , and fall off a cliff immediately past peak.
The small stinger nozzle is just under Mach1 and pushes the engine to the verge of deto over a wide band , to quickly build heat over the short run duration, helped also by very high com allowed by 110 Octane rocketfuel.

Also the header nozzle is very small for a single port cylinder, this is due to the very low BMEP able to be produced by limited Blowdown , Intake and Transfer area.

[andreas]

Very pretty Wobbly

[ken seeber]

Very pretty Wobbly

I just thought he looked nice....:innocent::innocent:

[andreas]

I just thought he looked nice....:innocent::innocent:

I'm sure of it. But it's actually called Beat genre, you sacrifice punctuation for the free flowing jazz articulation.:shifty:

[wobbly]

Wheely good looking is the most accurate description.

[RAW]

But after two race meetings the lack of lubrication access from the transfer flow , into the piston /pin bearing area , caused the pin surface to turn blue.

Next test was a simple cap , laser welded slightly inside the pin end , this had maybe 0.25 Hp on a stock cylinder and 0.75 Hp down low on a big port cylinder ( they fell out as well ).

Wobbly how did the cylinder fair with the failed caps ?

[jamathi]

But after two race meetings the lack of lubrication access from the transfer flow , into the piston /pin bearing area , caused the pin surface to turn blue.

Next test was a simple cap , laser welded slightly inside the pin end , this had maybe 0.25 Hp on a stock cylinder and 0.75 Hp down low on a big port cylinder ( they fell out as well ).

Wobbly how did the cylinder fair with the failed caps ?

At Aprilia the end of the pins always turned blue after only 1 dyno test, no further problems....

[wobbly]

Not so good - I thought the extra flow area into the A port might have made more power - sadly it siezed at 14800 rpm
I have now done 23 dyno tests with the tophat laser welded pin.
The pornographic laser weld looks just fine so far , and no blue on the pin surface inside the piston.
I wonder what caused the Aprilia pin to do that Jan, any ideas , as the TM stock setup lasts as long as the piston does with no colouring.

[F5 Dave]

Ooh jeezuz that's not a pretty sight.

[Frits Overmars]

Not so good...
348667

Avoiding the above mess was one of the reasons to make my Torlon plugs. They do a better job at preventing aux-transfer short-circuiting than the Pankl pin on the left, they are a lot cheaper, and in the unlikely event that they should come loose, the engine can digest them without damage.
348665348666

[Vortex]

Not so good - I thought the extra flow area into the A port might have made more power - sadly it siezed at 14800 rpm
I have now done 23 dyno tests with the tophat laser welded pin.
The pornographic laser weld looks just fine so far , and no blue on the pin surface inside the piston.
I wonder what caused the Aprilia pin to do that Jan, any ideas , as the TM stock setup lasts as long as the piston does with no colouring.

Oh my dear,
That's a hugh seizure.

cheers

[Condyn]

Frits, is Torlon superior to a polyimide plastic like Vespel for the plugging application? I know it is more cost effective.

[Frits Overmars]

Frits, is Torlon superior to a polyimide plastic like Vespel for the plugging application? I know it is more cost effective.I don't know; I stopped searching when I found that Torlon proved usable.

[wobbly]

Thanks Frits , I have used your Torlon plugs in the KZ engine , and freaked out when the pins turned blue. Its hard enough to keep these engines together
without the worry of a small end lubrication failure.
Seems very strange that Jan says the Aprilia turned blue immediately , maybe with the Pankle stepped version , eventually the lube makes it thru into the piston load surface
and the pin doesnt suffer anymore.
As it stands , the laser welded caps I have made are working perfectly , not as cost effective as Torlons , but hell of a lot better than Pankle.

[TZ350]

.
Even more two stroke stuffing.......
.
<iframe width="560" height="315" src="https://www.youtube.com/embed/3ZnZDIMueN0" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[SwePatrick]

Is it possible to use some other exclusive material in the whole pin?
Like titanium or something, and run it solid.
Maybe some ceramic?

And is there an powerloss if having a boosthole in piston?
This to ventilate the gasses under the piston.

[ken seeber]

For piston pins to start going blue raises lots of questions. Look at a tempering colours for steel and, for blue, the temp is in the range of 250C plus. If the bluing is only in the ends and the central section and pin bearing are not discoloured, then the only logical conclusion is that the heat must be coming down thru the piston bosses. As Wob has pointed out, this occurs even with plugs which would prevent any hot gases being the culprit.

If it is the piston transferring the heat to the pin, then one can conclude that the piston would have to be above this temp. With a cast hypereutectic piston, the T6 heat treatment requires an aging temp of around 210C. Anything above this would create softening of the material, both permanent and also being considerably weakened during operation at the higher elevated temps, maybe to half its original aged strength.

Given this, one would think the pin boss bores would be flogged out, but this is not always the case. Perhaps there is so much distortion taking place there is no rotation of the pin, perhaps adding to thermal transfer to the pin.

Could the bluing be some form of stain ? Intriguing.

[flyincat]

So here is a pipe optimised for a piston port cylinder drag racing with a CVT.
Most all piston port cylinders have crap transfer ducts that cannot be " fixed " except for introducing stagger and remedial work on the radial angles to help
chronic short circuiting that occurs with anything even approaching a modern diffuser design.

These old engines like a long header , much longer than we would even think of using today , as this helps to delay the depression formed around BDC , allowing the transfer streams to at
least make a start up the Leaning Tower before being overcome , and creating a big loss in Trapping Efficiency.
The mid section is as fat as I dare go , and its very long due to the steep rear cone.


This is just for sharing and comparison.... here's an OEM pipe from a piston port (+tiny case reed) 530 parallel twin suzuki used in a snowmobile (CVT). This would nominally run about 8250rpm. DISCLAIMER: It's a stamped pipe so hard to differentiate inflection points. It could probably use better measurement resolution towards the end of the diffuser to capture more accurately.

348668

[flyincat]

Here's another oldy OEM pipe for a similar suzuki piston port (+ tiny case reed), this time 500cc. This is a 2 into 1 pipe, y-pipe not shown.

348669

[Frits Overmars]

Is it possible to use some other exclusive material in the whole pin? Like titanium or something, and run it solid. Maybe some ceramic?
And is there an powerloss if having a boosthole in piston? This to ventilate the gasses under the piston.Titanium is too elastic to serve as a needle bearing surface, and coating it with a hard layer such as TiN or DLC won't help because this layer would be much too thin; the needles would 'sink through the ice', so to speak. A solid ceramic pin might fill the bill. It can be hard, light and probably also tough enough.
However, a solid pin would help against gas flow through the pin, but that is not the problem. The problem is short-circuiting from the A-transfers to the exhaust and that can only be counteracted by 'closing' the piston skirt at the pin bores.

I cannot see a reason for power loss through a boost hole in the piston. On the contrary, I remember a strange experience with a Rotax-124 kart engine.
Its C-transfer port is fed in the now usual way via a duct from the crankcase; the cylinder has no provision for feeding the C-transfer through the piston.
One race weekend we needed a new piston but the only available piston had a C-boost window. I could see no harm, so we fitted that piston, and all went well. Very well, so after the weekend I put the engine on the dyno and it produced more power than it had done with a closed piston.
To this day I cannot explain what had happened. There could not be any gas flow through that piston window because the only time it opened, was when it ran over the C-transfer in the cylinder, and the pressures inside the piston and in the C-duct ought to be equal....

[wobbly]

Back when the Rotax 256 was first introduced to Superkarts I was factory manager at Zipkarts in England.
We were so excited I managed to get the boss Martin Hines to spend up large on a real Heenan Froude.
This was pretty basic - it had no data logging , the only way to record the power/rpm was to use a VHS video camera and play the digital readouts back in slomo , and
write down the numbers.

Anyway I spent all the time i could on the new engine , even staying back at night dyno thrashing endlessly.
With alot of hard pipe/port work I finally managed to get it over 13,000 where it promptly broke a rod and cut the front of the case completely in 1/2.
As it was so new , Rotax actually coughed up a complete replacement - with new much heavyer rods.

One of the best power advances was a 1/2 moon cutout in the boost port skirt , then I moved it up and it became a round hole about 16mm Dia with a corresponding hole near the bottom
of the boost port duct.
Later the factory , who refused to believe the power numbers we were getting ( until our world champ winning engine /pipes were sent to them ) changed the cylinder casting to our deep 1/2 moon cutaway at the boost port duct entry , just like the Aprilia got much later.
That setup with a 1/2 moon in the skirt was factory stock for many years after - finally the skirt cutout was deleted as the restriction to the boost port entry no longer existed.

[lodgernz]

One race weekend we needed a new piston but the only available piston had a C-boost window. I could see no harm, so we fitted that piston, and all went well. Very well, so after the weekend I put the engine on the dyno and it produced more power than it had done with a closed piston.
To this day I cannot explain what had happened. There could not be any gas flow through that piston window because the only time it opened, was when it ran over the C-transfer in the cylinder, and the pressures inside the piston and in the C-duct ought to be equal....

Is it possible that pressure in the boost port lagged a millisecond behind the pressure under the piston due to it's more torturous route, so that there was brief flow from under the piston into the port, thereby giving a tiny window of lubrication to the bearing?

[jfn2]

Wobbly
In your drawing of an optimized pipe for a singe exhaust port engine with cvt, would you explain why you added a 24.2 dia 20mm long section instead of just covering up the 24.2 dia end of the rear cone with the 28.6 dia silencer? By the way, thanks for the drawing. jfn2

[wobbly]

The 24.2 dia is a 20mm long insert inside the front of a 28.6 dia ID standard size stinger tube.
The insert effectively does all the restriction , and in effect negates most of the length and diameter effects of the stinger tube.
I have found that having a stinger length about the same as the rear cone length minimises the effects as well.

[jamathi]

Titanium is too elastic to serve as a needle bearing surface, and coating it with a hard layer such as TiN or DLC won't help because this layer would be much too thin; the needles would 'sink through the ice', so to speak. A solid ceramic pin might fill the bill. It can be hard, light and probably also tough enough.
However, a solid pin would help against gas flow through the pin, but that is not the problem. The problem is short-circuiting from the A-transfers to the exhaust and that can only be counteracted by 'closing' the piston skirt at the pin bores.

I cannot see a reason for power loss through a boost hole in the piston. On the contrary, I remember a strange experience with a Rotax-124 kart engine.
Its C-transfer port is fed in the now usual way via a duct from the crankcase; the cylinder has no provision for feeding the C-transfer through the piston.
One race weekend we needed a new piston but the only available piston had a C-boost window. I could see no harm, so we fitted that piston, and all went well. Very well, so after the weekend I put the engine on the dyno and it produced more power than it had done with a closed piston.
To this day I cannot explain what had happened. There could not be any gas flow through that piston window because the only time it opened, was when it ran over the C-transfer in the cylinder, and the pressures inside the piston and in the C-duct ought to be equal....

A solid ceramic pin was tried at Aprilia in 1995.
I think it was made by Mercedes, but I am not sure.
It broke at 10.000 in its first test....

[katinas]

For piston pins to start going blue raises lots of questions. Look at a tempering colours for steel and, for blue, the temp is in the range of 250C plus. If the bluing is only in the ends and the central section and pin bearing are not discoloured, then the only logical conclusion is that the heat must be coming down thru the piston bosses. As Wob has pointed out, this occurs even with plugs which would prevent any hot gases being the culprit.

If it is the piston transferring the heat to the pin, then one can conclude that the piston would have to be above this temp. With a cast hypereutectic piston, the T6 heat treatment requires an aging temp of around 210C. Anything above this would create softening of the material, both permanent and also being considerably weakened during operation at the higher elevated temps, maybe to half its original aged strength.

Given this, one would think the pin boss bores would be flogged out, but this is not always the case. Perhaps there is so much distortion taking place there is no rotation of the pin, perhaps adding to thermal transfer to the pin.

Could the bluing be some form of stain ? Intriguing.

Maybe it could be the reason why some pistons are not lightening at place between crown and pin boss bores, just left all material without any inside or outside lightening. (add photos of cast Prox KTM sx 125 and forged YZR 500 pistons)
Honda stick to outside cavity type shape for Rs 125/250, but pin boss bores are coated with some material. Is it thermal barrier or sliding coating or both?

[Muhr]

For piston pins to start going blue raises lots of questions. Look at a tempering colours for steel and, for blue, the temp is in the range of 250C plus. If the bluing is only in the ends and the central section and pin bearing are not discoloured, then the only logical conclusion is that the heat must be coming down thru the piston bosses. As Wob has pointed out, this occurs even with plugs which would prevent any hot gases being the culprit.

If it is the piston transferring the heat to the pin, then one can conclude that the piston would have to be above this temp. With a cast hypereutectic piston, the T6 heat treatment requires an aging temp of around 210C. Anything above this would create softening of the material, both permanent and also being considerably weakened during operation at the higher elevated temps, maybe to half its original aged strength.

Given this, one would think the pin boss bores would be flogged out, but this is not always the case. Perhaps there is so much distortion taking place there is no rotation of the pin, perhaps adding to thermal transfer to the pin.

Could the bluing be some form of stain ? Intriguing.

All the used pankl pins I have seen look like below. Maybe makes sense as the area for heat radiation decreases when closing the sides
However, this has not always been the scenario when they (the plugs) were made of a material with less thermal conductivity and mass.

Fritz is right as usual!:Oops:
I think there is something linguistically wrong on my part that makes me want to put in that E.
Sorry for my substandard spelling, I'll try to get better

[Frits Overmars]

Guys, in case you are having problems finding things with Google: there's no e in Pankl
https://pankl.com/en/

[jfn2]

Are the Pankl pins welded up in a vacuum?

Thank you woobly for your reply.
jfn

[wobbly]

My take would be the pins are welded in an Argon chamber as I have used in the past for Titanium pipes.
As there is such a tiny heat affected zone from the laser proces, its easy enough to press a cap onto one end , then flush the pin and press on the the other end,
then weld around the circumference .

[Peljhan]

I don't know if it was mentioned before but from what kind of steel it's good to make rotary disc? What is prefered thickness and case clearance? Thanks

[Flettner]

I don't know if it was mentioned before but from what kind of steel it's good to make rotary disc? What is prefered thickness and case clearance? Thanks

I make mine from spring steel sheet, laser cut out, Ill go and measure one but I think approx 0.7mm.

[OopsClunkThud]

to get around the short circuiting, couldn't you add another set of aux ports ~ over the B or C Ports? Unlikely to flow that much except when the pressure is high (blowdown)

[TZ350]

I don't know if it was mentioned before but from what kind of steel it's good to make rotary disc? What is prefered thickness and case clearance? Thanks


I make mine from spring steel sheet, laser cut out, Ill go and measure one but I think approx 0.7mm.

Mine are made out of 1.0mm thick laser cut stainless steel with 0.25mm (Suzuki) to 0.5mm (Kawasaki) side clearance. I would have preferred spring steel but the SS one's were free and when it's free you takes what you get.

I have run spring steel and stainless in both plain alloy Kawasaki outer covers and the Suzuki outer covers with the phenolic wearing surface. Both worked Ok.

[lodgernz]

I don't know if it was mentioned before but from what kind of steel it's good to make rotary disc? What is prefered thickness and case clearance? Thanks

I made mine out of 1.0mm carbon fibre sheet, running with 0.5mm clearance total. Disk floating of course. Still going after 2 years racing.

[wobbly]

OopsClunk - Aux ports around past bore center have been tested , and they loose power.
The issue is that looking in plan the Aux path length is way longer than the main ports distance from the diffuser entry.
This is also why when the Aux are made too high ( close in timing to the main ) there are two opposing factors at work.
The extra Blowdown STA can and will help with overev Hp , but the opposing factor is that the steep wave front created by the main port cracking open
is smeared in time and reduced in amplitude by the flow suddenly exiting thru the longer Aux ducts almost simultaneously.
This results in a loss in mid and peak power .
The badly affected amplitude downside issue in this case overcomes the technically greater Blowdown STA capability.
So moving the Aux entry point even further away from the header , would have way more downside than any gain from a reduction in port linking.

[Frits Overmars]

Fritz is right as usual....Sorry for my substandard spelling . . . . . . . .:rolleyes:

[Muhr]

. . . . . . . .:rolleyes:

:oSometimes I surpass myself!

[yatasaki]

I don't know if it was mentioned before but from what kind of steel it's good to make rotary disc? What is prefered thickness and case clearance? Thanks

Like Flettner said, spring steel 1000N/mm2+ or by our local grade Č2330, or simmilar.
If sheet not available this would fit perfect (just test with magnet to be sure if stainless or not)

[Peljhan]

Thank you for all the answers.
I will get some spring steel.

[katinas]

I think the problem are the Jim Lomas pipes. They were designed for the stock NC19 with a belly diameter from only 102 mm. So for me it looks like that the pipe volume is too small. When using a 120 mm belly even a 22 mm stinger venturi brings the temps down to an expected level....

For comparisons add Sugaya kit pipe dimensions, that specially developed for NS 250/400 vertical cylinder (without ATAC). Works in good way from 7000 to 10500 rpm. Tuned length 936 mm. Its not usable for 500 kit, but maybe helps for std, one exhaust cylinder, setup

[TZ350]

<iframe width="560" height="315" src="https://www.youtube.com/embed/WB3qTVg3hhs" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

Ok, so she is not riding a motorcycle but there you go.......

[TZ350]

.
Magic stuff. More two stroke stuffing ........
.
<iframe width="560" height="315" src="https://www.youtube.com/embed/d2QvBNpMllQ" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

[Flettner]

MMM, the smell of an E85 fueled injected twostroke with Micro T oil, on the dyno. O, and the noise, neighbor's love it:cool:
The 360 is running well but needs the extra fueling with temp graph sorted and the injection timing is ???? And a couple of sensors need calibrating.
Tempted to just put an air filter on it and run it around the yard. Probably getting a little ahead of myself, there will be more problems, there always are in the early days of development when you think you know what you are doing but really, you don't.
Its just exciting to have it running and being able to start and stop it at will. 350 Kawasaki program is in it now, a good base to start with.

[F5 Dave]

<iframe width="560" height="315" src="https://www.youtube.com/embed/WB3qTVg3hhs" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

Ok, so she is not riding a motorcycle but there you go.......
Well, I'm not seeing any right hand turns. Bit more practice and she'll get there I'm sure.

[41juergen]

For comparisons add Sugaya kit pipe dimensions, that specially developed for NS 250/400 vertical cylinder (without ATAC). Works in good way from 7000 to 10500 rpm. Tuned length 936 mm. Its not usable for 500 kit, but maybe helps for std, one exhaust cylinder, setup

Thank's a lot for that info, will see how I can use this as a starting point.
Do you have the ignition timing curve for the stock NS400R?

[Peljhan]

As I will make variable rotary valve, I wonder, what is correct way to look at wave action in EngMod? Do I need to look Pcrank behaviour?

I can shift complete disc forward and backward in total of 30°. For now i used fix timings 140°/85°.
Here is Pcrank plot for different rpm.
It's 50cc with max power at 16800rpm and usable range is from 12500rpm.

Picture of crankshaft. It still needs finishing.

[Frits Overmars]

As I will make variable rotary valve, I wonder, what is correct way to look at wave action in EngMod? Do I need to look Pcrank behaviour? I can shift complete disc forward and backward in total of 30°. For now i used fix timings 140°/85°. Here is Pcrank plot for different rpm.
It's 50cc with max power at 16800rpm and usable range is from 12500rpm. Picture of crankshaft. It still needs finishing.Max power at 16800 rpm seems pretty optimistic; most of today's 50cc racing engines run out of breath above 15000 rpm. But I must say that your cylinder ( https://www.kiwibiker.co.nz/forums/showthread.php/162399-The-Bucket-Foundry/page323 ) looks quite promising. And I like the way you are going to vary your rotary inlet disc position.

[katinas]

Thank's a lot for that info, will see how I can use this as a starting point.
Do you have the ignition timing curve for the stock NS400R?

Like I write in earlier post, can’t find ignition timing curve, looks like things lost with old comp.
Remember that after squish /compression correction to usable range from abnormal mass production, gains in upper range, comes only with AVGAZ. With RON 98, same effect comes only after timing curve was retarded 7 degrees, with adjustable lobe plate on main rotor.
But its better to start with RGV 250 ignition timing curve, that worked far better for NS 400 than std, in the whole range.

Add pipes effects for NS 250/400 one cylinder test engine ( with Honda RS 250 ND5 ignition ). Blue is Sugaya, red Honda RS 125 type. On the road, with RS type exhaust, bike goes much much faster.

If DMR 500 kit cylinder reed house adopted for stock reed cage, it is possible to gain more hp with KTM sx 85/ Husky TC 85 V force red cage. Mismatch between holes just 0.5 mm and no more any modifications needed.

[katinas]

Few pictures from GP racers. Honda NSR 500 under-engine position type 1987-1991 cooling pump and cranks from NSR 250 NV2 1992-1997 and 1993 RGV 500 xr79. Looks like NSR 250 con rod trusted at small end as big end without side washers, but roller cage no side washers too. Good lubrication from side of smaller crank web.
Indeed, things that maybe never became history.

[wobbly]

Peljhan , as you are varying the timing by moving the whole disc , forward and back - this means the duration is fixed . I would start with 90* closing
as it is proven that carburation is a nightmare past this with very little extra power.
Then run the sim in 1* retarded closing sequentially.
This will give an indication of what timing suits each rpm best.

But this gives odd sets of timing ie at 90* closing you have 135* opening , so radical closing , but average opening.
Back at 80* closing you have 145* opening , so very mild closing , but very radical opening.
Again , past 145* , tuning is a nightmare - and this will not show up as bad carburation issues in the sim , as in reality.
This is why I believe Fletts servo gib system is superior , especially when operating both sides independantly.

Many 4T cars had VVT on the inlet only , and this worked well , but VVT on both cams gave a huge increase in power range.

[Frits Overmars]

This is why I believe Fletts servo gib system is superior , especially when operating both sides independantly.Amen to that. I admired the simplicity of Peljhans approach rather than its efficacy.

[Peljhan]

Max power at 16800 rpm seems pretty optimistic; most of today's 50cc racing engines run out of breath above 15000 rpm. But I must say that your cylinder ( https://www.kiwibiker.co.nz/forums/showthread.php/162399-The-Bucket-Foundry/page323 ) looks quite promising. And I like the way you are going to vary your rotary inlet disc position.

Are you refering to Freetech bikes, or classic, like Kreidlers? I believe freetech guys usually keep rpm low to get engines more reliable?
But why do they run out of breath? Not enough blowdown? Bikes in the 80s ran to 18krpm.
I also made crankshaft with higher inertia, as low inertia seems to be problem for high rpm.

Case variation would probably be better, but when I designed this engine I did not think of that. If this desigh will not work, I will try double rotodisc plates, one being variable and other fixed on hub (if that works). If anything of that doesn't work, I will fix disc and make it old way.

Setting this bike will be a pain :sweatdrop

[Flettner]

https://youtu.be/977BWjCMC8E Crappy upside down video, but you get the picture.

[Muhr]

Are you refering to Freetech bikes, or classic, like Kreidlers? I believe freetech guys usually keep rpm low to get engines more reliable?
But why do they run out of breath? Not enough blowdown? Bikes in the 80s ran to 18krpm.
I also made crankshaft with higher inertia, as low inertia seems to be problem for high rpm.

Hi what a nice job you have done so far.
I have thought about this regarding my own engine in terms of rpm and stroke vs peak hp. Here you could take an RSA as a reference with a 42 mm carb and just do:
21 * 21 * π / 13000 * 16800/125 * 50 / π = √ * 2≈30mm
Then unfortunately you have this with acceleration. For every time the port opens, an acceleration time is needed and it is controlled by the pressure difference. which does not increase with RPM. That is where the theory falls and the reality is unfortunately different.
Then it depends much on what your goals are in terms of power, To rev 18k is not so much needed
That's my view on it, Interesting to hear others!

[wobbly]

The carb size dilema can be helped alot by using a Lectron HV style venturi carb.
They have a 4mm smaller radiused entry behind the slide , so at 1/2 throttle it appears to be a 26mm bore.
At WOT they actually flow more air on the bench than a PWM or Dellorto 30mm etc.

Second issue with going from 15000 rpm to 18000.
STA wise this is easily achievable , but you have to be aware of power range with respect to gear drops.
A gear drop of 5% @ 15000 = 750 rpm , 5% at 18000 = 900 rpm , using the same gearbox.

But in principal , as power has a direct relationship to rpm , as long as torque can be maintained , jumping from 15000 to 18000 means
an increase of 3000/15000 = 20% more theoretical power available.

As far as the reality of the available power at higher rpm is concerned there are two factors .
The first is inlet tuning - this will for sure have much higher amplitude wave inertia effects , but this effect is very much second fiddle to the pipe in a 2T.
With 20% more rpm , it will come down to one major factor - can the new pipe length generate significantly more superposition when working with the new port timing combination.
If so , this can and will generate big increases in scavenging and plugging wave action at the port.

[Frits Overmars]

Are you refering to Freetech bikes, or classic, like Kreidlers? I believe freetech guys usually keep rpm low to get engines more reliable?
But why do they run out of breath? Not enough blowdown? Bikes in the 80s ran to 18krpm.:sweatdropI know the stories about classic 50s revving to 18000 rpm, and those stories seem to grow at a rate of 500 rpm per year, depending on who is telling them, but the best classics, the Van Veen Kreidlers and Jan Thiels Bultaco and Garelli 50cc engines, produced maximum power below 16000 rpm.
The Freetech guys have discovered that with the cylinders they are using, maximum power is best found between 14000 and 15000 rpm, and this is not a reliability issue but a time.area issue, regarding both blowdown and transfer time.area. I have yet to see a 50cc cylinder with the same specific time.areas as the Aprilia RSA125, though your cylinder might come close, by the looks of it.

[Peljhan]

@Muhr, sorry I didn't understood your calculation, are you refering to carb size? I think that is not a bottleneck in engine like that.
But you got me thinking, maybe your theory that mixture mass doesn't have time to accelerate is more applicable to transfers and mixture escaping into exhaust port and shoving it back to cylinder.

I will be using smartcarb 28mm. I still need to drill holes in it to make power jet. And to get one in Europe, it took me 80 conversation emails and 18 months to get it, but they forgot to include two metering rods. No bill at purchase included either. Could write whole day about that but I will not drop on that level.
Anyway, I wouldn't go that path again. Next time would go with normal or Lectron 30mm-something carb or make my own as at Grobnik circuit where we race 80% of lap is WOT.

@Wobbly, I will try to sim it like you said.
I do not worry about gear drops that much. If i will ever be able to ride that bike I will be happy as we have a leg feature in common Wob ;) , so now i will focus more on R&D. Also there is exhaust valve on cylinder and I am thinking of trying Frits variable exhaust nozzle.
About variating disc only dyno test will show if it is for any use. I want to make some starting base in EngMod just to know where to go, as there is million combinations how to set it.
Max power rpm will also be set with testing, I just got to those numbers as couldn't produce decent power in lower revs in EngMod, but that could be misleading for me.

@Frits, in past 15 years, I allways saw 18k stated for those classics, but maybe this was more of a max rpm engine reached if one rev it to death, and I believe you, it could be more for wow effect in magazines. I think, first thing I should worry is BE bearing reliability. And this variating design is more complicated as it looks. Because of carb in it's way, mechanism is like swiss watch. I believe Flettners case vary would be easier to make.

Thank you Frits for having a faith in my moped :)
Here is picture of ports (it looks enormously big as it is wide lens mode to make decent pic). I know outer-lower aux exhaust edge is quite close to A port, should make more teardrop shape, but at casting this core moved down 1mm and that shape is all I could save out of it.
In addition, exhaust duct is very good cooled, even around power valve, duct has proper length and Wobbly design implemented. Would make water path over cylinder better but as I was stubborn with classic outside look design, I made best I could for now.
And for you Frits, picture of mechanism in cad. Engine is allmost made, I hope I will start testing in few months.

[Muhr]

@Muhr, sorry I didn't understood your calculation, are you refering to carb size? I think that is not a bottleneck in engine like that.
But you got me thinking, maybe your theory that mixture mass doesn't have time to accelerate is more applicable to transfers and mixture escaping into exhaust port and shoving it back to cylinder.

It was just as vague as usual when I write ...
21 * 21 * π / 13000 * 16800/125 * 50 / π = √ * 2≈30mm
21 * 21 * 3.14 / 13000 * 16800/125 * 50 / 3.14 square root * 2 = 30.196mm

I intended to refer to the opening area of the carburetor and rotor valve inlet, but it was as unclear as usual😁. What I was trying to say was that where you have pressure gradient force you will have an acceleration every time it opens. (Which is controlled by the pressure difference, turbulence and pressure waves but not RPM at least not for the better)
The only place where you will not have more favorable conditions for higher rpm due to lower piston speed is in the rotary valve rather the opposite. That's my view of it when I tore my hair in desperate attempts to improve the time area for 15500k on the latest 50cc engine I fiddled with. On the engine I am building now, I have the same hopeless hopes of peak rpm

[Frits Overmars]

For every time the port opens, an acceleration time is needed and it is controlled by the pressure difference. which does not increase with RPM. !The pressure difference acts upon each mm² of the cross flow area of the gas column in a duct, so the cross flow area has no effect on the inertia of the column; only the column length plays a role here.
And luckily higher revving engines tend to have shorter ducts, so we need not worry too much about engine rpm either. In fact I hardly occupy myself with rpm; I prefer to look at the mean piston speed.

[katinas]

Peljhan Muhr, amazing little engines, so nice to see this work. Thanks for pictures.

[Muhr]

The pressure difference acts upon each mm² of the cross flow area of the gas column in a duct, so the cross flow area has no effect on the inertia of the column; only the column length plays a role here.
And luckily higher revving engines tend to have shorter ducts, so we need not worry too much about engine rpm either. In fact I hardly occupy myself with rpm; I prefer to look at the mean piston speed.

Maybe it's something I do not understand here but my point is the shorter the opening time (higher rpm) the more percentage of time will consist of acceleration of the flow, the lower the efficiency per unit time. Is that time insignificantly small?

[Frits Overmars]

Maybe it's something I do not understand here but my point is the shorter the opening time (higher rpm) the more percentage of time will consist of acceleration of the flow, the lower the efficiency per unit time. Is that time insignificantly small?No, that time is anything but insignificantly small. But a given pressure difference will give a short gas column a higher rate of acceleration than a long gas column, that is what I was trying to say.
So in the shorter time that is available for accelerating the gas column in a high-revving engine, that column may still reach the same flow speed that it would reach in a lower-revving engine because of the shorter ducts that we are likely to find in the higher-revving engine.

[Muhr]

No, that time is anything but insignificantly small. But a given pressure difference will give a short gas column a higher rate of acceleration than a long gas column, that is what I was trying to say.
So in the shorter time that is available for accelerating the gas column in a high-revving engine, that column may still reach the same flow speed that it would reach in a lower-revving engine because of the shorter ducts that we are likely to find in the higher-revving engine.

Ok now I understand better (sometimes I'm a little slow) what you mean, you are referring to friction loss will decrease with a shorter intake on a high revving engine. I can only agree! Thank you Frits for the more detailed answer

[Peljhan]

So here is EngMod result.

Disclaimer: :)
I did not yet correct exhaust power valve action (that's why top is strange).
I took 140°/85° as baseline, as this was best so far.
Let's leave impossible carb setting with odd timings aside for this test...

First results 17.X: reducing opening time and kept 85° closing as constant.. At 115/85 power was best, and all gain was down low at 12000rpm.

Results with 18.X: reducing closing time and kept 140° opening as constant. At 140/65 power was best and again, all gain at 12000rpm (and probably lower).

If I went up over 145 or over 90, power remained the same.

Then I tried some combinations, but none of them gained nothing, so best result overall was 140/60 (no variating at all)


Now, as EngMod doesn't simulate influence of odd timings to carb being nigthmare to setup..

I am wondering, Wobbly, do you know where in rev range odd timings make carb impossible to setup? You said, if going over 145°/90° is nightmare.. Is it maybe one of those only hard to set at low rpm?
Only for example: at low rpm-you can't start a bike with 160/100 timing, but it works really good at high rpm. :scratch:

[teriks]

Ok now I understand better (sometimes I'm a little slow) what you mean, you are referring to friction loss will decrease with a shorter intake on a high revving engine. I can only agree! Thank you Frits for the more detailed answerI'm more inclined to think in terms of lower inertia of the shorter gas column though...

[Frits Overmars]

Ok now I understand better (sometimes I'm a little slow) what you mean, you are referring to friction loss will decrease with a shorter intake on a high revving engine. I can only agree!
Thank you Frits for the more detailed answerAnd thank you for the S, Muhr :msn-wink:.
As a matter of fact I was not refering to friction losses, but to the flow's resistance to acceleration. If you are an electronics man, you may find it helpful to compare friction losses to Ohm's resistance, and inertial resistance to impedance, where there is no resistance as long as the flow is constant.


I'm more inclined to think in terms of lower inertia of the shorter gas column though...While I was pondering about how to explain things without creating more confusion, you nailed it Teriks :niceone:

[Muhr]

And thank you for the S, Muhr :msn-wink:.
As a matter of fact I was not refering to friction losses, but to the flow's resistance to acceleration. If you are an electronics man, you may find it helpful to compare friction losses to Ohm's resistance, and inertial resistance to impedance, where there is no resistance as long as the flow is constant.

While I was pondering about how to explain things without creating more confusion, you nailed it Teriks :niceone:

I'm trying my best Frits! :innocent:I just feel stupider for every attempt to understand. I assumed you were referring to friction loss (or skin friction) when you mentioned length as a factor. I thought Newton's second law does not care about the length of the intake as the area towards the low pressure zone does not change?
I think inertia is a consequence of Friction loss in this context?:o

[Frits Overmars]

Wobbly, do you know where in rev range odd timings make carb impossible to setup? You said, if going over 145°/90° is nightmare.. Is it maybe one of those only hard to set at low rpm? Only for example: at low rpm-you can't start a bike with 160/100 timing, but it works really good at high rpm.There are practical limits at both sides of the inlet timing. You can open the inlet as soon as the pressure in the crankcase has dropped to the pressure level upstream of the inlet disc.
Open it any earlier and you will lose crankcase pressure to the outside world; open it any later and the crankcase pressure will drop more than it needs to, slowing down the transfer flow.
The Helmholtz resonance of the blowdown+scavenging cycle determines how many milliseconds after exhaust opening the pressures upstream and downstream of the inlet disc are equal.
This fixed amount of time means that at low revs you could open the inlet even before BDC. But this is impractical for two reasons (unless your name is Neil Hintz).
A: The inlet needs to open later as the revs increase.
B: Opening the inlet exactly when the pressures upstream and downstream of the inlet disc are equal means that there wil be a zero-pressure opening signal sent to the carburetor, and carburetors don't respond well to something they don't notice.

Summary: opening the inlet too early or too late will both cost power, but opening it too early will cause more problems than opening it too late.

When should we close the inlet? When the inlet flow is slowed down to zero by the ever-rising crankcase pressure. Close it any earlier and you will miss out on the last bit of crankcase filling; close it too late and you will lose mixture flowing back from the crankcase towards the outside world, passing the carburetor on its way out and taking some more fuel with it. This same amount of now overly-rich mixture will be sucked in again at the next inlet cycle, passing through the carburetor for the third time, taking some fuel with it for the third time and trying to drown the engine.

Summary: don't close the inlet too late. For a well-developed racing engine 85° after TDC will be about the limit. If you are really power-hungry, you can try a couple of degrees more, but it may harm your lap times.

If you do find more power past 85°, you may instead consider returning to the 85° closure timing and fitting a bigger carburetor.
By the way, 85° after TDC is also considered the maximum foolproof timing for a piston-ported inlet system.

In case you are interested in the Aprilia RSA125 inlet system: cylinder capacity=124,8 cc; crankcase volume @ TDC=675 cc; inlet timing= 142,5°/88°; carburetor diameter= 42 mm.

So this is it? Not quite yet, because closing the inlet too early can also give strange effects, as I discovered when I put an experimental distance piece between the carburetor and the inlet disc.
This increased the inertia of the inlet column, so this column came up to speed slower, and was subsequently cut off by the closing inlet disc while it was still flowing towards the crankcase at a respectable speed. The sudden closure caused a high collision pressure upstream of the inlet disc and the mixture column bounced back like you wouldn't believe. It filled the entire dyno room with a mixture mist within seconds, and the tiniest spark might have blown the roof off. Ever since this experience I distinguish between blow-back, which is a nuisance, and bounce-back, which is outright dangerous.

[Frits Overmars]

I just feel stupider for every attempt to understand. I assumed you were referring to friction loss (or skin friction) when you mentioned length as a factor. I thought Newton's second law does not care about the length of the intake as the area towards the low pressure zone does not change? I think inertia is a consequence of Friction loss in this context?Just forget all about friction for now; Newton won't mind.
And don't feel stupid. It took me a lifetime to get where I am now and I'm sure that I will have reasons to feel stupid if I look back on today in a couple of years.That's life.

.

[Muhr]

Just forget all about friction for now; Newton won't mind.
And don't feel stupid. It took me a lifetime to get where I am now and I'm sure that I will have reasons to feel stupid if I look back on today in a couple of years.That's life.

.

What should I say! Something that is affected by length but not by surface. I guess Isaac did not leave the building based on how you write. the only thing I can think of is sound but have a hard time applying it to something meaningful (could be something about Isaccs third). You have me by the balls on this one! What is the point of doing something if you do not understand why. Thanks for the thought exercise Frits.:scratch:

[wobbly]

I made a small error in my statement about the inlet timing.
140 opening is the practical limit , not 145 as I wrote , as is 90 on the closing.
I did a huge project on RV timing when at Zipkart dynoing the Rotax tanden twin.
The standard valve had staight edges and was timed at 135/85.This setup was easy to tune and gave a nice flat torque curve.

But to my ( evil ) mind it made way too much power , where we never used it on the track.
I quickly found that 140* was the limit on opening , as carburation became a real issue in the midrange area we were using on track - starting at around 9800.
Going in steps up from 85 closing , the engine made more and more peak and overev power , all the way to 90*.
Past this nothing was gained.

So the next mod was to make the cylinder port sides straight , instead of the slightly squashed oval.
With the same timings a bunch of power appeared in the overev.
So next was a bigger carb bore - I could go to 39.4 from 38 in the magnesium round slide Dellortos.
This also added to the peak and overev power.

Now the thing would rev , whereas before it dropped off a cliff at 12200 , now 13000 + was easy.
So I went back to 88* closing and this gave the best off corner power , but still allowed overev to 12800.

Much , much later with real good JL pipes , and better ( flatslide ) carbs and a servo PV etc the Superkart engine eventually gave 94 Hp at 12750 and would rev to 13400.
This was achieved with 41mm carbs and the 140/90 timing. - going back to 88* timing it simply would not rev past 13,000.

As we now know , the Aprilia RSW ended up with 42 carbs and virtually the same timings, the RSA worked best with slightly more opening and slightly less closing.
Learning from this I would say that to make high rpm power the closing is critical , and the limit is a crossover point where the carburation in the midrange becomes impossible Vs overev power capability.
Thus EngMod in this case is of limited value as the sim will still run , whereas the engine struggles to accelerate at all on the dyno with too much opening/closing timing.

EDIT - the other last point is that the RV engine loves a solenoid Power Jet , the very short inlet seems to respond way more than a reed setup to shuting off ( PWM is better ) a quite big PJ over the top.

[Flettner]

Bring on the sliding Gibs then.

[F5 Dave]

Disco is dead Neil.

Oh sorry. Not those Gibbs. :no:

[Frits Overmars]

What should I say! Something that is affected by length but not by surface. I guess Isaac did not leave the building based on how you write. the only thing I can think of is sound but have a hard time applying it to something meaningful (could be something about Isaccs third). You have me by the balls on this one! What is the point of doing something if you do not understand why. Thanks for the thought exercise Frits.Muhr, I have the utmost respect for the work of Sir Isaac Newton and I certainly do not deny the existance of friction, but inertia is a different animal and my point was that it may be easier to understand its effects if you leave friction out of the equasion for now.

[Muhr]

Muhr, I have the utmost respect for the work of Sir Isaac Newton and I certainly do not deny the existance of friction, but inertia is a different animal and my point was that it may be easier to understand its effects if you leave friction out of the equasion for now.

Teriks has also tried to make me understand this by pm, but the token has not fallen down yet.
That we have a mass to accelerate it is obvious.
That we have an area on the intake that the air must enter through that I also understand.
But that if we extend it 50mm with a piece of pipe and hence get a higher inertia in that acceleration without friction being the factor there, you have lost me.
In my head I think that atmospheric pressure does not care that it only has one way in or longer, as long as it is not exposed to an area change.
Thanks for trying!

[Peljhan]

Thank you all for nice lesson :)
Best way will be to install rotodisc and try some variations on dyno.

Flettner, I can't make Gibbs now as I have allready made engine casings. (actually my friend with his CNC skills). Here are some pics.

Frits, I am using 175° now with my pistonported Tomos D6, with 2 transfers and butterfly exhaust. It is making 14HP on back wheel and 142km/h at Rijeka-Grobnik racetrack.

Wobbly, as I have 2 outputs on my Zeeltronic for solenoid powerjet, I want to install one anyway. Some advice, where can I get appropriate-decent one? Thanks.

[andreas]

Now we don't leave a man behind. It is obvious that there is a mass, and the mass gets greater the longer the duct. Also the pressure difference is the same, then Newton just say: delta p= force/area, and acceleration=force/mass.

[Frits Overmars]

Now we don't leave a man behind. It is obvious that there is a mass, and the mass gets greater the longer the duct. Also the pressure difference is the same, then Newton just say: delta p= force/area, and acceleration=force/mass.I fully agree, Adreas; I'm just writing it down step by step.
Duct volume V = cross flow area A * duct length L
The mass m in our duct is proportional to the duct volume V
m ≈ V
m = A * L
The pressure differential p over this duct exerts a force F= p * A upon mass m
acceleration a is force / mass ;
a = F / m
a = (p * A) / (A * L)
a = p / L
In English: the acceleration of a mass in a duct is proportional to (pressure / length) . If you double the length, the rate of acceleration will be halved, and vice versa.


While we are at it, let us take a look at the amount of mass that is moved through the duct in a given amount of time.
First, let's make some assumptions in order to keep things simple (my hobbyhorse, as y'all may have noticed).
1: The pressure differential over our duct is constant (in reality it would drop because of mass moving from the high-pressure side to the low-pressure side of the duct).
2: The duct ends in a port which is fully opened during t seconds, after which it is suddenly closed.
The length of the gas column that passes through the port, is ½ * (acceleration a) * (time t)²
Now if we compare a duct with length L to a duct with a length 2L the acceleration in duct L will be twice as high as the acceleration in duct 2L, as we have seen above.
This means that with the same pressure differential and the same amount of open port time, the long duct will fill the cylinder only half as well as the short duct. It's a great reason for using a short inlet duct which allows us to use a short opening time.

[Muhr]

I fully agree, Adreas; I'm just writing it down step by step.
Duct volume V = cross flow area A * duct length L
The mass m in our duct is proportional to the duct volume V
m ≈ V
m = A * L
The pressure differential p over this duct exerts a force F= p * A upon mass m
acceleration a is force / mass ;
a = F / m
a = (p * A) / (A * L)
a = p / L
In English: the acceleration of a mass in a duct is proportional to (pressure / length) . If you double the length, the rate of acceleration will be halved, and vice versa.


While we are at it, let us take a look at the amount of mass that is moved through the duct in a given amount of time.
First, let's make some assumptions in order to keep things simple (my hobbyhorse, as y'all may have noticed).
1: The pressure differential over our duct is constant (in reality it would drop because of mass moving from the high-pressure side to the low-pressure side of the duct).
2: The duct ends in a port which is fully opened during t seconds, after which it is suddenly closed.
The length of the gas column that passes through the port, is ½ * (acceleration a) * (time t)²
Now if we compare a duct with length L to a duct with a length 2L the acceleration in duct L will be twice as high as the acceleration in duct 2L, as we have seen above.
This means that with the same pressure differential and the same amount of open port time, the long duct will fill the cylinder only half as well as the short duct. It's a great reason for using a short inlet duct which allows us to use a short opening time.


Thanks Frits now I understand where we went in different directions in this.
You write:
Duct volume V = cross flow area A * duct length L
The mass m in our duct is proportional to the duct volume V


As I understand the equation above, the air in the intake is a mass that is moved with the atmosphere outside. And if you move it twice the distance or need to do it half the time, double the force / time will be required.

This is what I have in my head when I think about it and calculate.
I see the air in the intake as part of the atmosphere with its restrictions that escalate with velosity to the maximum allowable flow is reached. which in this case unfortunately will not be linear
I reason like it's the same atmosphere in the box as outside until you put on a lid.

I have always thought like this:

R = ½ρCAv2
So I calculate with a velocity (v), the density (ρ) of air and area (A) on the intake and a coefficient of drag (C) (in this case friction)

[Flettner]

Thank you all for nice lesson :)


Flettner, I can't make Gibbs now as I have allready made engine casings. (actually my friend with his CNC skills). Here are some pics.

.

The sliding Gibs live in the valve cover, not the engine casing. Can be retro fitted to any rotary valve twostroke, just need the appropriate valve cover.

Nice machined case set by the way.

[wobbly]

The solenoid used on the later Dellorto magnesium race carbs was , I believe , a standard part used as an idle air bypass valve on a small Fiat Carburettor ( Weber )
The same thing turned up on Keihin carbs for MX bikes and aslo Honda RS125 98+ Keihin SPJ.
I have also used the Mikuni solenoid kit sold by Allensperformace .uk - very expensive.

[TZ350]

.
More from the genius of the Two Stroke Stuffing workshop.
.
<iframe width="560" height="315" src="https://www.youtube.com/embed/vQ_aJrpW80g" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[andreas]

If someone like a lower intermediate battle, I usually stay up late on Lichess.org as Lansandreas.

[lohring]

While we're on the topic of small, high power glow ignition engines, some of you may be interested in a series I wrote about the development and construction of high power model engines. It's an attempt to preserve the heritage of a dying breed. Glow plugs, a disposable item, are costing $15+ US dollars these days. I still have memories from the late 1950s of screaming control line speed engines fueled with shoe polish smelling nitrobenzene in exotic mixtures with names like Missile Mist. I hope there is enough information in these articles for an ambitious person to design and build these engines. Unfortunately, I doubt that they live in English speaking countries. I owe a lot of my understanding to several of the members of this forum. Thanks.

Links are below:


namba.com/content/library/propwash/2018/october/14/ History


namba.com/content/library/propwash/2019/april/24/ Modern Piston & Liner Construction


namba.com/content/library/propwash/2019/october/4 Cylinder Head Design


namba.com/content/library/propwash/2020/april/4/ Tuned Pipe Design


namba.com/content/library/propwash/2020/October/4/ Port Design & Scavenging


namba.com/content/library/propwash/2021/march/16/ Mechanical Design


Lohring Miller

[Frits Overmars]

While we're on the topic of small, high power glow ignition engines, some of you may be interested in a series I wrote about the development and construction of high power model engines. It's an attempt to preserve the heritage of a dying breed. Glow plugs, a disposable item, are costing $15+ US dollars these days. I still have memories from the late 1950s of screaming control line speed engines fueled with shoe polish smelling nitrobenzene in exotic mixtures with names like Missile Mist. I hope there is enough information in these articles for an ambitious person to design and build these engines. Unfortunately, I doubt that they live in English speaking countries. I owe a lot of my understanding to several of the members of this forum. Thanks.
Links are below:
namba.com/content/library/propwash/2018/october/14/ History
namba.com/content/library/propwash/2019/april/24/ Modern Piston & Liner Construction
namba.com/content/library/propwash/2019/october/4 Cylinder Head Design
namba.com/content/library/propwash/2020/april/4/ Tuned Pipe Design
namba.com/content/library/propwash/2020/October/4/ Port Design & Scavenging
namba.com/content/library/propwash/2021/march/16/ Mechanical Design
Thank you for this comprehensive overview Lohring.
It was a pleasant (and flattering) surprise to encounter the methanol-burning MB40 engine, although it's not even a boat engine :msn-wink:.

[Flettner]

If one was to be looking at a 24 / 7 intake system, 125, what length would the intake tube need to be???

[andreas]

If one was to be looking at a 24 / 7 intake system, 125, what length would the intake tube need to be???

I've written down a note from Wobbly, it says 125 mm including end correction, to the reeds approximated opening point, is in tune at 12000 rpm. Probably there is more science to it for a 24/7.
So, I forgot How many Reflections/inversions that is, and then the Helmholtz? Basically I ain't got a clue.