ESE's works engine tuner

[pete376403]

I worked on 2 stroke 16V149 Detroits Diesels that had 4 turbos, two bypass superchargers, intercooling, ceramic coated piston tops and chambers to produce just under 1 hp per cubic inch in the 1980s. The piston skirt and top were seperate and they used 4 exhaust valves per cylinder.

Used for industrial and military generators and marine propulsion. They were something to behold. Leaky, noisy and prone to fires caused by oil spray from turbo oil lines soaking lagging and catching fire. I had to rescue a coworker once using a firefighting oxygen unit when he was overcome by fumes from a fire.

The bypass kicking off could be heard through supposedly soundproof enclosures and felt as a pressure change.

I got to thinking about the role crankcase pressures played a part in two stroke operation with them because when all cylinder block leaks were sealed, a catastrophic failure was likely imminent.
Just googled that engine type - pretty cool.

[wobbly]

VRO , your press fit guess was close but the final number depends upon two main factors.
Solid pin or hollow pin , and crank material/heat treat.
For a hollow pin and or a case hardened only material ( 4140 ) the number is 0.08 to 0.1mm.
For a solid pin and or thru hardened tool steel ( EN36B ) the number is 0.05 to 0.06mm.
Pin diameter has a smaller effect , wherein a big ( 25mm ) pin needs less press fit than a smaller ( 20mm ) due to the circumferential interference area.

[Muhr]

Hi someone who has some good suggestions on rubber quality for the shock absorption to the clutch basket.

[husaberg]

Hi someone who has some good suggestions on rubber quality for the shock absorption to the clutch basket.

don't use rubber
use urethane instead
ask Grumph what or what Shore range.

[Muhr]

don't use rubber
use urethane instead
ask Grumph what or what Shore range.

Thank you Husa, I will do a little research into what I can get my hands on. Yes, then it is these shore values, for which there are several different measurement methods. I know very little, but may try to do a simulation and see if I can understand something

[husaberg]

paging Greg

Steve Ward told me the other day he uses genuine on his fleet - at $15 each...Pretty sure we'll be nowhere near that expensive.

The materal supplier cocked up the order and it's arriving today - approx a week late - so the test set will be off to Dave Monday - PM me a postal adress Dave please.

[peewee]

https://youtu.be/Q2uvgoUCh3g

[Flettner]

Urethane? I think thats what its called. I made a wee die and get these molded for me, special.

[wobbly]

I had a Hinson clutch cush drive destroy itself , due to having 100RWHp put thru it I suppose.
I had 70 shore urethane bar made up , has worked perfectly since.

[vro46i]

VRO , your press fit guess was close but the final number depends upon two main factors.
Solid pin or hollow pin , and crank material/heat treat.
For a hollow pin and or a case hardened only material ( 4140 ) the number is 0.08 to 0.1mm.
For a solid pin and or thru hardened tool steel ( EN36B ) the number is 0.05 to 0.06mm.
Pin diameter has a smaller effect , wherein a big ( 25mm ) pin needs less press fit than a smaller ( 20mm ) due to the circumferential interference area.

Thanks Wob, much appreciated,

It is a solid 24mm pin replacement, going into the original suzuki crank web. I can assume anything about the material without a proof test with a vickers hardness tester or equivalent.

[Muhr]

I hope I can find some options in the 8mm sheet that I can water cut.
wobbly, hope to be able to approach your loads in my 50cc. 75nm and about 300nm on the clutch and shock loads on significantly more:apumpin:

Vro

If it is not as hard on the side you are cutting more on, there is a risk that it will start rolling off material when you start pressing on the pin. Evidence of experience

[Muhr]

Found this, may be useful sometime


Before I show you the calculation, you should be aware that there is not a direct relationship between a Shore scale and Young’s Modulus! The calculation allows you to approximate ‘E’ based on a range of Shore-A (20 to 80) or Shore-D (30 to 85) durometers for simple static analysis.** If you routinely work with plastic and rubber materials, you should be using SOLIDWORKS Simulation Premium with the actual stress-strain curve for the material(s) you design with!

For a durometer given in Shore-A, multiply this value by 0.0235. Then subtract 0.6403 from this result. The next step is to find the inverse base-e logarithm of this new result. The answer is an approximation for Young’s Modulus in megapascals (MPa). To convert this to pounds per square inch (psi), simply multiply this number by 145.0377.

Shore-A to Young’s Modulus (in MPa):
=EXP((Shore-A Durometer)*0.0235-0.6403)

Shore-D to Young’s Modulus (in MPa):
=EXP((Shore-D Durometer + 50)*0.0235-0.6403)

[wobbly]

Most all Jap factory cranks are induction hardened around the pin bore and the bearing surfaces.
You are going bigger in diameter , but may well have bored thru all the hardened material when moving the hole.
My guess would be to replicate the original interference in this case - and use Loctite Bearing Fit as a sort of lube and to help with retention.

[vro46i]

Most all Jap factory cranks are induction hardened around the pin bore and the bearing surfaces.
You are going bigger in diameter , but may well have bored thru all the hardened material when moving the hole.
My guess would be to replicate the original interference in this case - and use Loctite Bearing Fit as a sort of lube and to help with retention.

Hi Wob, I was pondering that question, but thank you for confirming it for me.
I'll have another meeting with the machinist to ensure that we are replicating the factory interference fit.

[vro46i]

I hope I can find some options in the 8mm sheet that I can water cut.
wobbly, hope to be able to approach your loads in my 50cc. 75nm and about 300nm on the clutch and shock loads on significantly more:apumpin:

Vro

If it is not as hard on the side you are cutting more on, there is a risk that it will start rolling off material when you start pressing on the pin. Evidence of experience

Hi Muhr, I appreciate your advice.
Based on your comment, I will have to design a localised support press plate to minimise the anticipated deformation on the 'soft side' of the new pin hole.
I'll measure up the crank web dimensions and see what I can come with that is effective.

Cheers

[husaberg]

Hi Wobbly, I have arrived at the stage of destroking the engine from 125cc to 110. Using an oversized big end pin (24mm dia) where previously a 22mm dia. The machinist is going to offset bore it to fit the new big end pin to achieve the required stroke. Can you please tell me, how much of an interference fit does the big end pin to the new crank web hole is acceptable? 2 -3 thou? Thanks in advance.

Have you considered inserting sleeves into the 22mm bore and doing an offset bore to destroke using a 18mm or 20mm pin.

24mm pin is pretty big for 110cc
You can key the sleeve but i doubt it's required.

the opposite of this powroll
https://powrollpasthome.files.wordpress.com/2019/02/16017ra.jpg

The other other option just use a shorter stroke crank.
or get the crowd that built the pin for Speedpro to do you an offset pin.

My crankpin was made by heat treatments. machined, heat treated, and ground. Hasn't let go yet but still early days. 20mm ends with a 22mm centre, offset .75mm. Very helpful guys.

https://www.kiwibiker.co.nz/forums/showthread.php/155906-ESE-s-works-engine-tuner?p=1130471126#post1130471126

[porttiming124]

The groove will indeed constitute a bypass. Whether it will actually serve as a bypass, depends on the exhaust and transfer pressures.
As you say, the effect may be small. Just try it; you've got nothing to lose.

ok thanks i will try it

[porttiming124]

Over herein Oz around a century ago, there was an engine used in karting for little kids, it was called the Comer S80 or SW80.
It had a chrome bore and a 2 ring piston. The tuning trick of the day was to reduce friction from the second ring. The rules stated that both rings must be in place.
What the "gun" tuners did was to reshape the second ring such that it was tensioned into the ring groove, ie making no contact with the bore, but still there to prevent short circuiting and also satisfy the rules.
To achieve this, the ring was squeezed into an "undersize" ring, such that the ends must have overlapped, ie forming a helix. Then it was heated, presumably to some annealing temperature, maybe 800 - 900 C for cast iron, less for steel.

Then it was fitted to the groove such that it was tight to the bottom of the ring groove. Clever ??

So, if you have old rings to play with, maybe this is the go.

No guarantees though.

I will try to remove a ring and leave the groove open and if I see that I have a loss I will try that. thank you

[porttiming124]

I tried what Woobly and Frits have already discussed. Retaining the flow of the reed box which does not only want to come out in front but also in the side. I gained 2 hp on an 800cc 3 cylinder engine that makes 210hp.
thank you350852

[vro46i]

Have you considered inserting sleeves into the 22mm bore and doing an offset bore to destroke using a 18mm or 20mm pin.

24mm pin is pretty big for 110cc
You can key the sleeve but i doubt it's required.

the opposite of this powroll
https://powrollpasthome.files.wordpress.com/2019/02/16017ra.jpg

The other other option just use a shorter stroke crank.
or get the crowd that built the pin for Speedpro to do you an offset pin.


https://www.kiwibiker.co.nz/forums/showthread.php/155906-ESE-s-works-engine-tuner?p=1130471126#post1130471126

I have another RG bottom end to build up as the spare engine, so that will be the one to try other forms of destroking the engine. I think the cleanest but most expensive way is to machine up a shorter stroke crank.
Thanks for your advice and recommendation, lots to think about now....

[wobbly]

I have found the cheapest way to do restroking is to bore the hole offset and oversize.This makes the hole size irrelevant.
Then insert a sleeve that is size for size to this hole , and has the interference fit for the pin on its ID.
That way welding isnt needed , and as long as the two holes are bored exactly on the same centerline , its easy to align the assembly with no runout.

[Condyn]

I have a question about the exhaust port floor. I found this drawing, which appears to be from Frits. It shows a very high floor compared to what I am used to seeing. On our snowmobile engines with auxiliary exhaust ports we typically run 81° ATDC exhaust open timing and 115° transfer open timing, which equals 34° BD.

The exhaust port floors I see almost always are at the same level as the transfer port floors. Since we already do all kinds of welding on these cylinders before resleeving with aluminum sleeves, would it be wise to raise the floors like the drawing?

If anyone has any insight on this subject I would love to hear it.

[porttiming124]

I have a question about the exhaust port floor. I found this drawing, which appears to be from Frits. It shows a very high floor compared to what I am used to seeing. On our snowmobile engines with auxiliary exhaust ports we typically run 81° ATDC exhaust open timing and 115° transfer open timing, which equals 34° BD.

The exhaust port floors I see almost always are at the same level as the transfer port floors. Since we already do all kinds of welding on these cylinders before resleeving with aluminum sleeves, would it be wise to raise the floors like the drawing?

If anyone has any insight on this subject I would love to hear it.


I believe from the drawing that frits shows us it is to show the height of the blowdown.

[wobbly]

Lifting the Ex duct floor is only effective when the Blowdown STA has been fully optimized.
In a single Ex port scenario this is rarely achievable.
I have not seen any direct dyno data to prove how effective this technique is in a conventional 2T layout apart from Jans final experiment at Aprilia where it was lifted 3mm on a 54.5 stroke , so you are in unknown territory above that level.
But hey its easy enough to lift it higher and then drop it incrementally to find the optimum , apart from exposing the ring to alloy when re chamfering and probably ultimately needing a replate.
What is fully proven and documented is reducing the duct exit area to 75% effective ( chordal area x cosine of the down angle ) in a 3 port , and 90% in a single port.
Filling in the port bottom corners with large radi below TPO also is common proven SOTA technology to help reduce short circuiting from the A port front wall.

[Condyn]

I have used the “ wobbly duct “ with success. Surprised? No, but still not sure I understand the why.

Is the 75% number in itself a rule unbreakable, or is the associated Mach value the focal point?

The reason I ask is because if we find the exhaust port floor is too low ( on the dyno ) with optimized blowdown do we then have to shrink the duct exit even more because of the smaller port or do we target a specific mach number?

I realize this is somewhat speculation on my end and there might not be available answers. Just thinking out loud.

[wobbly]

The answer is all down to achieving Mach 0.8 at the duct exit before the tapered transition into the header.
Less than this always looses power , and after doing a huge number of projects with this number being used , I did an analysis of the results gained and that is where the " 0.75 area rule of thumb " came from.
Frits has always said I should be relating the Blowdown area with a factor for the duct exit , and I agree with him , but the current guideline works so well I honestly cant be bothered.
This is alot more relevant to single Ex port race engines , where getting anything like 0.8 would seem impossible as the gas flow regime is so low in comparison to a 3 port - but I hardly
even see single port engines these days , so again I cant be bothered putting in any unnecessary effort - especially as I make a living doing way more interesting stuff.

[Condyn]

Fair enough. I have seen the duct work first hand so thats proof enough for me.

[Muhr]

Hello finally done with the clutch! Then there is "rubber" left, did some simulations and 50 shore seems to be a good starting point for a small engine like this.

[TZ350]

<iframe width="560" height="315" src="https://www.youtube.com/embed/UtvBnpMll7g" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

Because Team ESE use the Suzuki RG50 and GP125 engines from the late 70's and early 80's I found the early racing R&D development years and comments from the original 60's development race team very interesting. A bit of bike action too.

[TZ350]

350859

Hello finally done with the clutch!

Beautiful work. ... :niceone:

[TZ350]

350860

Completed my Suzuki RG50 with what was originally a piston port/case reed inlet with its now new rotary valve conversion.

Next move is to put it all together with the cylinder from my current RG50 engine so that I can compare before and after conversion dyno runs.

[F5 Dave]

That will be interesting Rob. I never thought to try that.

That said, throttle response will be interesting on a kart track. I had mildish piston port component to mine but the change to derbi full reed was noticeable in certain corners, particularly at Kaitoke with its downhill section that promoted load up.

[Vannik]

Fair enough. I have seen the duct work first hand so that's proof enough for me.

I try:

350861

Probably needs updating. Any ideas?

[OopsClunkThud]

I did a series of 2D CFD runs looking at the port roof angle, piston angle, radius... as the piston moves from just opened to almost BDC. at low pressure ratios after blowdown was done large scale turbulent eddies would form. The image shows the piston at 130° ATDC, and the impact of the downward angle of the port from flat at the top and angled down in 5° increments. The eddies along the top of the port could be kept in check with a port angled down at 15° or more.

350862

Adding a radius I ran into competing priorities. The lower the pressure ratio, the larger the radius needs to be to prevent separation, but a large radius blocks the flow when the pressure ratio is high (during blowdown). In my single port case I was already limited on blowdown, so any radius seemed to harm the blowdown more than it helped reduce eddies.

I have not simulated it but raising the floor would likely reduce the eddies at the bottom. Also a very large radius could be applied to a raised floor with zero effect on time area.

Note: these were steady state 2D simulations and I'm no expert.

[wobbly]

Neels , the only comment I have to add is that I have done some back to back tests determining the optimum geometry for the interface of the Aux ducts and the main.
Jans general comment was the shorter the divider the better.
This fits in with the idea that a short divider ( or septum technically ) which isnt cooled directly by water would transfer less heat into the stored plugging charge.
So I tested this on a KZ cylinder , putting a radius on the joining edge and effectively 1/2 the divider length.
Result , average 1/2 - 3/4 Hp from peak torque all the way up over the top of the pipe.

[andreas]

I forget now, what is considered the optimal mean downward angle of the duct - 25*? But how much testing has been done with a larger angle? seems there could be some gain to be had in minimizing eddying, despite the loss of cross area.

[Pagi]

Frits, with your top raduis exhaust duct drawing i have seen somewhere ( raduis = 5 % of stroke ), what height of duct should be taken for the calculation of the time-area, with or without the radius ?..........

[Frits Overmars]

Frits, with your top radius exhaust duct drawing i have seen somewhere ( radius = 5 % of stroke ), what height of duct should be taken for the calculation of the time-area, with or without the radius ?..........The radius obviously has an influence so you cannot just neglect it.
Blowdown starts as soon as the first bit of light becomes visible between the piston and the top of the exhaust port. But calculating it is not going to be easy.
The elliptical shape of the port already makes it difficult to determine the open port area for each crank angle position and it certainly does not get any easier if the top edge of the port has a radius, and even more so if the piston timing edge also has a radius.
350869

[Pagi]

The radius obviously has an influence so you cannot just neglect it.
Blowdown starts as soon as the first bit of light becomes visible between the piston and the top of the exhaust port. But calculating it is not going to be easy.
The elliptical shape of the port already makes it difficult to determine the open port area for each crank angle position and it certainly does not get any easier if the top edge of the port has a radius, and even more so if the piston timing edge also has a radius.
350869

yes it seems logical ... hence my question !!!! so we can consider that taking your measuring system with a 45 ° rod as the correct basis .....:rolleyes:

[wobbly]

Please be aware that Jan applied the radius to the EX port on the Aprilia due to his boss "the great leader " haha, having designed a new " better " pipe that lost all the top end.
As it now transpires having an accurate analysis of the Aprilia porting , many years later , it turns out the Transfer STA is about 8% ahead in power capability over that of the calculated Blowdown - simply from the numbers.
By increasing the Cd of the Exhaust port with a radius to assist Blowdown flow it would appear that this dramatically increased the power capability , mimicking that of a port with 8% more STA.
To now go blindly adding Ex radi - just because it seems like a good idea , when it may not be needed if the STA numbers match correctly , is a mistake.

The down side of a timing edge radi , is much the same as having the much longer path length Aux ports , too high , ie the high amplitude initial blowdown wave front entering the header is smeared out in time by the gradually opening area.
Thus reducing the rarefaction return wave efficiency , and subsequentially this pulls out less plugging mixture around BDC.
In the Aprilia case the flow and increase timing upside , more than offset this downside - only needed due to a faulty pipe design, and Jan not having access to calculated sim or proven STA numbers at the time.
He could have had that data , but his boss told me in a job interview sims were a complete waste of time - which ironically is the same impression I had of him.

[Pagi]

Please be aware that Jan applied the radius to the EX port on the Aprilia due to his boss "the great leader " haha, having designed a new " better " pipe that lost all the top end.
As it now transpires having an accurate analysis of the Aprilia porting , many years later , it turns out the Transfer STA is about 8% ahead in power capability over that of the calculated Blowdown - simply from the numbers.
By increasing the Cd of the Exhaust port with a radius to assist Blowdown flow it would appear that this dramatically increased the power capability , mimicking that of a port with 8% more STA.
To now go blindly adding Ex radi - just because it seems like a good idea , when it may not be needed if the STA numbers match correctly , is a mistake.

The down side of a timing edge radi , is much the same as having the much longer path length Aux ports , too high , ie the high amplitude initial blowdown wave front entering the header is smeared out in time by the gradually opening area.
Thus reducing the rarefaction return wave efficiency , and subsequentially this pulls out less plugging mixture around BDC.
In the Aprilia case the flow and increase timing upside , more than offset this downside - only needed due to a faulty pipe design, and Jan not having access to calculated sim or proven STA numbers at the time.
He could have had that data , but his boss told me in a job interview sims were a complete waste of time - which ironically is the same impression I had of him.

thanks Wobbly......you answered my next question

[TZ350]

.
Keeping up with Alex's 2Stroke Stuffing adventures. https://youtu.be/y66bD2r8Bp8 looks like 30hp last time may not have been real. Or at least not real for the base tune but 21-22 hp looks consistent. 30hp showed up when the rotary valve slipped its timing. Now that the engine is becoming more reliable Alex is starting to look at tuning adjustments like boost, ignition and rotary valve timing. But any way you slice it, 20hp from 50cc at 10,000 rpm is certainly something.

[wobbly]

There have been a couple of questions re the Ex down angle and how this relates to flow and the duct exit area.
25* seems to be the best compromise here , and yes its been tested to death in the 125 KZ Kart class engine , the last bastion of real ( although severely restricted technically ) 2T outer limit performance.
Thus the idea of a 75% duct exit area is based on this proven tuning element.

On one side of the coin you have less flow separation from the roof with a steeper angle , but the immediate downside of this is that the chordal area X the down angle cosine , directly affects the Blowdown STA.
Less STA = less horsepower capability , thus you then have to generate more time and or area by increasing one or both of these.
At the outer limits of bmep , we are already up against the wall of what can physically be done.

With a 70% chordal width main duct and optimal roof radi , along with sufficiently lower Aux ports cut around to bore centerline , there is simply no more width/area to be gained to increase our Blowdown STA.
Timing wise as we approach 200* duration the power band shape becomes steeper and steeper each side of peak power , the worst effect is the power dropping almost vertically in the overev area.
I have seen , in an engine that had the Aux butchered upwards to equal the main port timing , the peak was 48Hp at 13800 , but by 14200 it had dropped to 20 - less than 1/2 in only 400 rpm.
A PV can ameliorate the front side power loss with high durations , but the only way to then help the overev is a shorter pipe , and that approach fucks the front side power even more.

The good old Catch 22 , with sadly , no free lunches either.

[porttiming124]

Neels , the only comment I have to add is that I have done some back to back tests determining the optimum geometry for the interface of the Aux ducts and the main.
Jans general comment was the shorter the divider the better.
This fits in with the idea that a short divider ( or septum technically ) which isnt cooled directly by water would transfer less heat into the stored plugging charge.
So I tested this on a KZ cylinder , putting a radius on the joining edge and effectively 1/2 the divider length.
Result , average 1/2 - 3/4 Hp from peak torque all the way up over the top of the pipe.

After cutting the length of the divider in half, do you know how long of the divider now?
I'm curious.

[wobbly]

55 to the radius - 67 to the bore = 12mm septum length.
And the new radiused end of the divider was tapered and thinned to almost a point by making the Aux duct wider.

[porttiming124]

ok thank you

[jfn2]

Hello Condyn
Sent you a PM. Thanks, jfn2

[TZ350]

.

350881

Ok I need some help. I am hoping for some ball park general advice from the Free Tec 50 guys. What sort of rotary valve timing do they use. 24mm carb, 14,000 peak rpm. Thanks.... :)

[wobbly]

Easy for you TeeZee , put in 140/90 into EngMod and work back till you loose power.

[TZ350]

Easy for you TeeZee , put in 140/90 into EngMod and work back till you loose power.

Thanks Wob. I was getting lost in the woods looking for a tree.

[Frits Overmars]

I am hoping for some ball park general advice from the Free Tec 50 guys. What sort of rotary valve timing do they use. 24mm carb, 14,000 peak rpm. Thanks.... :)You won't find many 24 mm carbs with the Freetech50 guys; 28 to 30 mm is common but I also know one or two good engines with 34s.
Wobbly's 140°/90° guideline may work well with a 24 mm carb, but closing the disc at 90° after TDC with a bigger carb can make your engine rather temperamental.

With EngMod2T you can of course work in either direction but on a real life engine working your way back from 90° would mean making a handful of discs. If you start with a closing timing of 75° aTDC you can modify one and the same disc till the lap times get worse (although engine power will still be increasing) and then you know the values for the optimum disc.

FYI: the Aprilia RSA had a 42 mm carb and 155°/89,5° disc timing and it produced maximum power at 13000 rpm; that's a mean piston speed of 23,6 meters per second.
I'm not sure if your 'peak rpm' means revs of maximum power or maximum revs but in any case 14000 rpm is rather modest. Most Freetech50 engines produce maximum power at around 14.500 rpm which equals a mean piston speed of 19,2 m/s, still a lot less than the RSA value, so I think it would be best to stay well within those RSA limits.

[porttiming124]

Hello. When I modify an engine I always rounded the corner between the reed valves in the direction of the transfers.
I saw a photo of a tm motor and had it leave the corner more square. Is that the purpose of improving the direction of flow to the transfers or just reducing the volume?
What do you think of it?350882350883

[Muhr]

You won't find many 24 mm carbs with the Freetech50 guys; 28 to 30 mm is common but I also know one or two good engines with 34s.
Wobbly's 140°/90° guideline may work well with a 24 mm carb, but closing the disc at 90° after TDC with a bigger carb can make your engine rather temperamental.

With EngMod2T you can of course work in either direction but on a real life engine working your way back from 90° would mean making a handful of discs. If you start with a closing timing of 75° aTDC you can modify one and the same disc till the lap times get worse (although engine power will still be increasing) and then you know the values for the optimum disc.

FYI: the Aprilia RSA had a 42 mm carb and 155°/89,5° disc timing and it produced maximum power at 13000 rpm; that's a mean piston speed of 23,6 meters per second.
I'm not sure if your 'peak rpm' means revs of maximum power or maximum revs but in any case 14000 rpm is rather modest. Most Freetech50 engines produce maximum power at around 14.500 rpm which equals a mean piston speed of 19,2 m/s, still a lot less than the RSA value, so I think it would be best to stay well within those RSA limits.

The rotary intake time area will be controlled by the RPM and diameter of the disc apart from the opening angles. What was / is the diameter of the RSA?

[wobbly]

Yo Frits/TeeZee - I suggested 90* as that is about as radical as I have ever seen/used on the Rotax 256 engines spinning to 14000 - usually using 88.
And the small 24mm carb would need plenty of timing to make power and revs. A 28mm HV Lectron would have a 24mm venturi but would flow hugely better than an OKI etc.
I know many FreeTech 50 guys use Lectron 30s - but remember the HV version of that has a 26mm venturi behind the slide to aid part throttle response.

The 140 opening I thought was about the limit as well, I have seen the Aprilia timing quoted up to 142 , and that caused more issues with tuning than it made Hp on the Rotax.
155 seems a completely crazy timing , and something I have never been aware of even having received several Aprilia EngMod files from people who have used thesis data from the Uni at Valencia for other
PhD projects.

Re relieving of the case in the TM is a long time mod. What is needed is to allow the side flow exiting the upper petals only to enter a slowly deepening channel as it heads for the transfer entry duct.
We attempt to bias the flow up under the piston with staggered reed stiffness , and this continues the idea.
There is a triangle shaped thin boss in the case on the reed box side walls, and the channel should start at nothing where the reed clamp is - then getting wider and deeper above this triangle that matches the reed block shape,
before radiusing around the corner into the transfer well above the crank.
TM engines are very finicky about case volume changes , especially going bigger , so dont get too excited.

[porttiming124]

With a v force would the channel really be just the top part of the reed box that would be pointing towards the transfer duct or the center as well? the 2nd image is what I tried earlier , thank you.
350885350886

[wobbly]

With a VeeForce your idea looks perfect , if you wanted to try biasing the flow you could make the top hollowed out area deeper and or even higher.
Unless you can get varying petal thickness for this model its a bit harder to change the flow regime thru the tips.
We use different thickness petals and much different petal backups top and bottom.
After literally hundreds of dyno runs this was worth average 1.5 Hp in 50 over stock which was a pretty trick setup to start with.

[TZ350]

350889

Blue line was with a 50 deg thermostat and the Red line was with a 42 deg thermostat. No other changes.

Put the RG50 up on the dyno tonight. Wanted to get a current base dyno run before putting this cylinder onto the rotary valve bottom end and doing a comparison run later in the week. Tests a week apart, not exactly back to back but you can only do what you can do.

[fpayart]

What was / is the diameter of the RSA?

Hello,

You will find hereafter pictures. The outside diamater of the valve is 126mm

350890350891

The timing is 93° / 146°

Regards, Francis.

[Muhr]

Hello,

You will find hereafter pictures. The outside diamater of the valve is 126mm

350890350891

The timing is 93° / 146°

Regards, Francis.

Thanks Good pictures!
Got this out of them.

Regards J

[wobbly]

Even allowing for scan errors , the 245 deg duration doesn't add up to 146/93 ?

[Muhr]

I agree with you! at 239 * it looks like this when I tried.:scratch:

[porttiming124]

With a VeeForce your idea looks perfect , if you wanted to try biasing the flow you could make the top hollowed out area deeper and or even higher.
Unless you can get varying petal thickness for this model its a bit harder to change the flow regime thru the tips.
We use different thickness petals and much different petal backups top and bottom.
After literally hundreds of dyno runs this was worth average 1.5 Hp in 50 over stock which was a pretty trick setup to start with.

ok thank you

[TZ350]

350909I agree with you! at 239 * it looks like this when I tried.:scratch:

Yep, that is the RV blade shape I would expect to see at 239 deg inlet port duration.

350910

Our Suzuki ones were about 210 deg duration.

[TZ350]

Easy for you TeeZee , put in 140/90 into EngMod and work back till you loose power.

140/85 turns out to be the best. I tried all sorts of combinations from 155 to 130 combined with 65 to 95. 140/85 is it.

[wobbly]

Im glad you came up with what I would have thought was perfectly reasonable.
Does that give you a Inlet STA that matches the Blowdown and Transfers.

[TZ350]

Im glad you came up with what I would have thought was perfectly reasonable.
Does that give you a Inlet STA that matches the Blowdown and Transfers.

Yes .........

350917

[Muhr]

It happens that if you make the disc straight on the opening side (if it is meant to be turned that way) it will be exactly 239 °. but as said, it may well be my mistake

[husaberg]

The black and white one might be an early Debri prototype?
350912350913

No where as cool as the RSW shapes
but i guess the RSA was ofsett.

[Frits Overmars]

The black and white one might be an early Debri prototype?
350913
Nothing to do with Derbi or Aprilia. It is the BBFT engine by Alfio Tosi.

[husaberg]

Nothing to do with Derbi or Aprilia. It is the BBFT engine by Alfio Tosi.

Cheers ....
it was saved under RSA with "moteur" in some froggy looking dialect.
Any idea what language this is
moteur%20rsa

Google is a baren wasteland under Alfio Tosi?
care to fill in the gaps

Anyway here are some other pics of the more intersting discs
350918350919350920350921

[andreas]

What is the black magic involved in shaping the disc's edges. When it would be more precise and area-efficient to have them rounded as in the drawing?

[Condyn]

What is the black magic involved in shaping the disc's edges. When it would be more precise and area-efficient to have them rounded as in the drawing?

I have been advised that the rounded corners will “ flutter “ and dig into the rotary housing on the case. Not sure if that was good advice or not.

[Peter1962]

Nothing to do with Derbi or Aprilia. It is the BBFT engine by Alfio Tosi.

In what year was that, Frits ?

[wobbly]

I spent months at ZipKart testing the new Rotax 256 for Hines 250 Superkart World Champ winning engine. With every disc shape known to man. Convex and concave radi on the closing edges , angled back , angled forward timing edges , everything.
At the same timings of 140/88 nothing made any more power anywhere.
The forward angle on the closing side was adopted as the outer leading edge gave support to the disc and reduced the bad wear occurring on the case face , due to the inlet column inertia pushing hard
on the disc as it closed. Even with trick coatings applied this problem never really went away.

[andreas]

No free lunch again

[fpayart]

Hello,

In order to avoid wear on the edge on the closing side of the crankcase, all our valves are designed with a "beak" on the outside diameter, which considerably improves the guiding of the valve when closing the hole.
Still in the spirit of completely removing this commitment, we have:
- Machined on both sides in contact with the valve, with APRILIA "style" grooves.
- Has a chemical nickel coating deposited, with quenching.
- Considerably lighten the hub and its nut, in steel.
- Use much stiffer carbon valves.
The problem is gone now.

350930350931350932350933

Francis.

[Muhr]

Hello,

In order to avoid wear on the edge on the closing side of the crankcase, all our valves are designed with a "beak" on the outside diameter, which considerably improves the guiding of the valve when closing the hole.
Still in the spirit of completely removing this commitment, we have:
- Machined on both sides in contact with the valve, with APRILIA "style" grooves.
- Has a chemical nickel coating deposited, with quenching.
- Considerably lighten the hub and its nut, in steel.
- Use much stiffer carbon valves.
The problem is gone now.


Francis.



Thanks for the helpful info Francis
I am working on a small 50cc, where I had the rotor cover cast, which was perhaps not so smart. Feels much easier to make disks for surface treatment (then you also get rid of the division between block halves). I bought materials for rotary valve a while ago, and then got the idea to make the cover in forged carbon fiber. So I bought material and we'll see how it goes.

[fpayart]

Pay attention to the quality of the carbon fiber to manufacture the valve.
This result is obtained by assembling several layers with very fine mesh Rowing.
The final thickness is about 1mm350935

[Flettner]

Pay attention to the quality of the carbon fiber to manufacture the valve.
This result is obtained by assembling several layers with very fine mesh Rowing.
The final thickness is about 1mm350935

Can it handle E85?

[husaberg]

Thanks for Posting Francis, i love your work, long may it continue.

[fpayart]

Can it handle E85?

I have never tried but the resin used is epoxy ???

[Muhr]

Pay attention to the quality of the carbon fiber to manufacture the valve.
This result is obtained by assembling several layers with very fine mesh Rowing.
The final thickness is about 1mm350935

Knows very little about what is good but the one I bought is made of: 2 Layers of XPREG XC130 210g 1 Layer of XPREG XC130 450g

[flyonly]

Anyone got or know where a little Myford lathe is in NZ. Would like something for my son to learn on.


Sent from my iPhone using Tapatalk

[Flettner]

I have never tried but the resin used is epoxy ???

V force say their reeds will fail on E85.

Thats why I use a steel disc valve. Would be nice to have a carbon disc that is ethanol compliant.

[Flettner]

Anyone got or know where a little Myford lathe is in NZ. Would like something for my son to learn on.


Sent from my iPhone using Tapatalk

Myford might be a little expensive these days, a Chinese lathe might be a cheaper option to learn on.

[Muhr]

V force say their reeds will fail on E85.

Thats why I use a steel disc valve. Would be nice to have a carbon disc that is ethanol compliant.


Found this when I searched before ..

”we wouldn’t suggest Epoxy Resins for lining a fuel tank. In general, epoxies have good resistance to petrol and many of the chemicals and additives found within pump fuel however the ethanol in fuel is known to cause problems over time and so specialist tank lining resins (often novalac vinylester based) should be used instead. One such product is GTS 1750 which is sold by Caswell Europe.”

https://www.masterbond.com/properties/alcohol-resistant-adhesives-sealants-and-coatings

[TZ350]

.
350938

Ok. Got the rotary valve Suzuki RG50 running tonight.

Blue line is the original piston port/reed setup. Red line is the exact same cylinder on the rotary valve bottom end, no other changes to ignition or jetting at this point.

I only managed one run before the ignition trigger fell off. Sort that tomorrow night.

350939

The RV seems to rev way past the old piston port setup. Looks like the RV setup needs different jetting and maybe timing compared to the old piston port/reed engine.

Looking forward to doing some tuning tomorrow night. Very excited now that it actually runs.

[F5 Dave]

Looking good Rob. Clearly jetting well off so excited to see what you end up with.

[philou]

Can it handle E85?

vinylster resin for e85

[Flettner]

vinylster resin for e85

As strong as epoxie?

[TZ350]

350942

I need some help with finding a High-Load & High-Rigidity 16x22x12 radial needle roller bearing cage assembly for the RG50.

As I am looking to push piston speed and rpm up I am not expecting my standard crank to last very long.

Most bearings are the old "W" cage design. I am looking for something better.

Any pointers to a proven good quality 16x22x12 big end bearing would be very welcome. Something that the Free Tec 50 developers have found to be reliable at 16,000 rpm.

[F5 Dave]

Bore it and use Yamaha parts Rob.

[oxracer]

350942

I need some help with finding a High-Load & High-Rigidity 16x22x12 radial needle roller bearing cage assembly for the RG50.

As I am looking to push piston speed and rpm up I am not expecting my standard crank to last very long.

Most bearings are the old "W" cage design. I am looking for something better.

Any pointers to a proven good quality 16x22x12 big end bearing would be very welcome. Something that the Free Tec 50 developers have found to be reliable at 16,000 rpm.
Hi TZ

You can get flat cage big end bearings here

http://www.emot.nl/products.php?section_id=25

Or here

https://www.tibenmotorsport.com/GB/Product-BARJG11-Conrod-bearing-big-end-16-22-12-silver-

[husaberg]

Samarin
I believe do two in silver one m other flat. this is the flat
http://www.samarin.net/?productos=&accion=buscar&idtipo=14&idmarca=&a=&c=&f=&jaula_piston=&b=&d=&l=&jaula_ciguenal=&Submit=BUSCAR&paginas=4&&id=13

http://www.pvlsverige.se/vrm/vevlager/JA-CI-62.jpg

Innerdiameter 16mm.
Ytterdiameter 22mm.
Bredd 11.75mm .
Rullmått 3 mm.

Beställningsnummer JA-CI-62.

Roffe the mad swede also has them
http://www.pvlsverige.se/vrm/index/index22.html

[andreas]

You want a KU style cage, with the loose rollers. There are other flat cages, but with self contained rollers, however they cant host as many of the rollers, of course silver plated. Usually the same size company competition bike eg. rm 50, is a good place to look.

[Francisco Erjavec]

[/QUOTE]FYI: the Aprilia RSA had a 42 mm carb and 155°/89,5° disc timing and it produced maximum power at 13000 rpm; that's a mean piston speed of 23,6 meters per second.
I'm not sure if your 'peak rpm' means revs of maximum power or maximum revs but in any case 14000 rpm is rather modest. Most Freetech50 engines produce maximum power at around 14.500 rpm which equals a mean piston speed of 19,2 m/s, still a lot less than the RSA value, so I think it would be best to stay well within those RSA limits.[/QUOTE]

Hi Frits,

I am confused about the RSA disc timing because you wrote at PIT-LANE forum that the RSA disc timing was 142,5°/88°. Please, could you clarify the difference with your recent post in this forum (155°/89,5°) ?

I highly appreciate all your shared information about RSA engine.
Greetings from Argentina.

[Muhr]

Has set a goal of 350 g including balancing weights for the entire rotor valve drive assembly. A first small piece

[Frits Overmars]

Hi Frits, I am confused about the RSA disc timing because you wrote at PIT-LANE forum that the RSA disc timing was 142,5°/88°. Please, could you clarify the difference with your recent post in this forum (155°/89,5°) ?Apparently I was confused as well Francisco; I seem to have mixed up several dyno test settings.
Here is what I could find back in chronological order after all those years (the DR-tests were done at Derbi; the AP-tests were done at Aprilia):

DRD243.PC:
2004-12-17; albero VHM 4034 V4C21;biella Yamaha C21; cuccinetti Rulli Apr C120+viggiu';
pistone Vertex n*149 965 C04; testa DB15 tr. 0.65-0.65 C34; Mappatura G44;
candela R7282A-110 gap 0,60mm; accensione microtec M127V2CAN;
carb. HRC mod VHM ovale max222; benzina Agip +3,5% ELF; alimentazione Lamellare(!) Daytona

DRVE3452.PC:
2006-10-25; N°curva 3452 moto DRVE n°03/06
Albero Drd 01/05 C004 raf.sp10.1bilan; biella Drd 120mm n°13 C004;
cuscinettiRulli Apr.giocco 0.057 C004; pistone 2544 (961) C04;
testa AC 56-G std TR0.75-0.76 C36; cilindro APE341 54.011;
valvola scarico/condotto sup.C004 Inf.C004 molle C004; tubo 69/03 moto Protti ferro;
Colettore/termin/silenz: 38.7 +0m+1gr.Sil.Dlr Hrc-std; mappatura GP184+0%A0
98B-V020B-P083B; candela Denso 35 usata C036; accensione Poker; Carburatore Vhta 41
Moto n°7 new valvolina; carburazione AU248T1.5P265Max218m48-4f-P120;
benzina ELF olio ELF 909 4%; alimentazione 155°/89.5° as20°r0sc25°r10C004

DRVE4734.PC:
2006-10-30; Gilera DRD 071030, LD 120, squish .74,
tubo G10/07 Sam.n°2.BN, tail 23, collettore 36, silenziatore 25,
Denso 34, accensione Poker, carb 42, AU286T2P264Max192m53-4f-P120,
benzina Agip +4% Elf 909, disco 152.5°/90°.

APC10768.PC:
2007-01-30; N°curva 10786;
Biella: L115 giocco 30/31; Pistone: 7 2544_03 974 seg_0.8mm;
Valvola scarico/condotto: 07/07 GV.<0.10mm
testa: 39 AC 56 TR.0.75; Rapp.Comp. 15.99; Cilindro APE Y 350 12/14 54.014;
tubo 102/06 n°1; collettore/terminale/silenz: (38.75+G_39_41) 23.25/24.5;
mappatura: P43P04P36 off. 0°; candela 46 Denso 34 lotto NH
carburatore: 42_pwmgetto 120 ug6 M030099b;
carburazione: 799+259+224+min46 corona 221;
benzina Agip GP6l +4% Elf HTX 909; alimentazione 142.5°/88°; diam 126mm

APC11684.PC:
2007-07-12; APC GP LD 115, seg_0.8, squish .76, tubo 102, bocca 38.75, terminale 23.25,
Denso 34, carb 42+PWM, getto 120, ug 6, 798+259+220+min46, corona 218,
benzina Agip GP6l +4% Elf HTX 909, disco 142.5°/88° diam 126mm

[Frits Overmars]

Has set a goal of 350 g including balancing weights for the entire rotor valve drive assembly. A first small pieceMuhr, do not copy the Aprilia RSA bevel gear drive from the balance shaft to the inlet disc; setting up those gears is a real nightmare.
There is a much better solution (that I did not discover until it was too late for the RSA): Kronenräder. The technique is well proven; Audi uses it for the transfer gears of their 4 wheel drive cars
https://www.google.com/search?client=firefox-b-d&q=kronenr%C3%A4der+hersteller
350958

[Muhr]

Muhr, do not copy the Aprilia RSA bevel gear drive from the balance shaft to the inlet disc; setting up those gears is a real nightmare.
There is a much better solution (that I did not discover until it was too late for the RSA): Kronenräder. The technique is well proven; Audi uses it for the transfer gears of their 4 wheel drive cars
https://www.google.com/search?client=firefox-b-d&q=kronenr%C3%A4der+hersteller
350958

Thanks Frits

You tipped about this before, I have looked for dealers and also emailed the supplier you tipped about but they were interested in how many 1000 I was going to order ... I will go past a supplier who works with bearings and gears in Sweden next week and see if they can solve it.
I already have angle gears and would be more than happy to change if I find a supplier.

[Frank S.]

Thanks Frits

You tipped about this before, I have looked for dealers and also emailed the supplier you tipped about but they were interested in how many 1000 I was going to order ... I will go past a supplier who works with bearings and gears in Sweden next week and see if they can solve it.
I already have angle gears and would be more than happy to change if I find a supplier.

Hi Muhr,
maybe you have a look at maedler.de
It is a german gear manufacturer where you can buy standard gears.
But they also make gears from your specs, even if it is only one piece.

[husaberg]

I know there were issues with the RSA and Frits posted gears are re ultimate answer, but instead of one off's and reinventing the wheel...
with the backlash couldn't you just use a spring much like hondas gears on the CBR VFR series only with miter gears.
350959
Pretty sure the Manx norton gear drive was a splined floating shaft in the end.
350960
https://trademe.tmcdn.co.nz/photoserver/plus/1287684307.jpg
https://trademe.tmcdn.co.nz/photoserver/plus/1287685091.jpg
https://www.trademe.co.nz/a/marketplace/toys-models/radio-control-robots/parts-accessories/other/listing/3550177919?gclid=EAIaIQobChMIt-Dxit6U9wIVN5NmAh1mrAApEAkYAiABEgJ07fD_BwE&gclsrc=aw.ds

https://www.norelem.com/us/en/Products/Product-overview/Systems-and-components-for-machine-and-plant-construction/22000-Drive-technology/Gears-Gear-Racks-Bevel-Gears/22430-Bevel-gears-in-steel-ratio-1-1-toothing-milled-straight-teeth-engagement-angle-20%C2%B0.html


https://sdp-si.com/PDFS/Bevel-Gears-and-Miter-Gears-Metric.pdf?__hstc=17737510.a66666d3732e7fef8343cd9 aebad1326.1650068985415.1650068985415.165006898541 5.1&__hssc=17737510.1.1650068985415&__hsfp=2586558486

[Francisco Erjavec]

Apparently I was confused as well Francisco; I seem to have mixed up several dyno test settings.


Frits,
Thank you very much for the clarification and the shared information.

[Flettner]

First actual dyno run up, light load. Just testing all is working and the computer is working. This is the 360 TPI with the rotary disc timing / throttle gibs setup.
https://youtube.com/shorts/uz2Q6o0YtaY?feature=share

[jonny quest]

Muhr, do not copy the Aprilia RSA bevel gear drive from the balance shaft to the inlet disc; setting up those gears is a real nightmare.
There is a much better solution (that I did not discover until it was too late for the RSA): Kronenräder. The technique is well proven; Audi uses it for the transfer gears of their 4 wheel drive cars
https://www.google.com/search?client=firefox-b-d&q=kronenr%C3%A4der+hersteller
350958

You will have backlash with this set up. It will also be very difficult to machine the shaft bores accurate for correct mesh. Unless... you can figured out eccentric bearings for the shafts for adjustment.

Bothe gear styles have drawbacks. As the famous phrase here... "no free lunch"

[TZ350]

350961

Managed to get some dyno time today.

Blue:- RG50 Piston-Port/Reed setup

Green:- RG50 Piston-Port/Reed cylinder and head swapped onto the Rotary Valve bottom end.
No other changes to the cylinder carb or ignition timing. Just plugged the inlet and swapped it all over.

Red:- The Rotary Valve setup after some carb and ignition tuning.

Very nearly there, more fiddling next week..... :violin:

[Francisco Erjavec]

Dear all,
I would like to share my RSA tech datasheet made with information shared by Jan and Frits.

[jonny quest]

TZ350, nice work!

Francisco... great data! Maybe include ex sta

[F5 Dave]

Hey Rob. Great increase. Now you need a decent pipe and that will start to look really impressive.

[TZ350]

Now you need a decent pipe and that will start to look really impressive.

Yes, most definitely need a proper purpose designed pipe. The current one is a Wobbly design for a 65cc engine peeking at 12,000 rpm.

I have plans developed using EngMod2T for a new RG50 cylinder with different port timing and a pipe designed to suit. And a crankshaft that can handle higher rpm.

[Vannik]

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

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

Takeaways:

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

[Peter1962]

This requires precision engineering, and is out of range for DIY projects...

The mechanical 2 stroke geniusses from the past, like Helmuth Fath, avoided those problems by using a simple toothet belt.

And it worked.

[Muhr]

Then we have something to test forget carbon fiber on. The reason I am interested in testing is that I also thought of trying to make connecting rods like Lamborghini does tests on.

[Frits Overmars]

I know this is 4T stuff but too much info in there not to ignore. This was posted by a friend of mine on a 4T forum.
Pat Symonds presentation on current F1 engines: https://www.youtube.com/watch?v=mUq-K9jcaB8Great stuff! Thank you Neels.

[41juergen]

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

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

Takeaways:

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

Thank's alot Neels! Some of that that stuff is now used by BMW for their new 6 cyl. engine....

[husaberg]

https://24htech.asia/throwback-thursday-bartol-250cc-gp-racer-s135555.html

[ken seeber]

[QUOTE=Vannik;1131200593]I know this is 4T stuff but too much info in there not to ignore. This was posted by a friend of mine on a 4T forum.

Pat Symonds presentation on current F1 engines:

* BSFC 167gms/kw-hr (0.27lbs/hp-hr), occurs at peak power

167 gms/kWhr....AMAZING.. Wonder what that'd relate to in an emission drive cycle....1-2 lit/100k ??

[Francisco Erjavec]

Combustion PRE-chamber concept is used in internal combustion engines for a long time and the JET ignition is the top evolution of this concept. See the JET ignition concept description in the link below:


https://www.youtube.com/watch?v=n6Eutw0WU3U

[sniemisto]

Hello gentlemen. I’m back on Derbi endurance moped build. Started preparing new Athena power valve for base line testing. I knew that there was small chip of plating missing on side of aux ex port, but I unluckily didn’t try it on warranty 3y back as I tough that its on area to be ported away.

It now appears that plating is re-chipping on and on as I proceed with stone bit on the port window, so I assume there has been something wrong in plating process. It’s same grade stone bit I’ve used on previous plated cylinders without any chipping. Now as I need to send it to re-plating, it’s tempting to get it near 55cc class limit.

That would mean max bore of 41.84mm. Only suitable piston I found was from IAME X30 water swift kart. I don’t really like it as ring ends are not centered in back and it has L-ring. Thinking of is it better to stay with 50cc than go extra 5cc with over square, limited B transfer width and more friction..?

Is there other 12mm pin piston someone can suggest?

If I go to 55cc, I would like to bore it by myself to be able port and check timings with piston before plating. Idea is to bolt thick plate on cylinder base, round the plate in lathe with cylinder attached on mandrel. Then attach cylinder to lathe from base plate and bore with boring bar.

Is it ok to bore cylinder until “before plating” dimension with this method and what is the spec for extra clearance before plating i.e. plating thickness with work allowance?

I have bottom end ready matched to this Athena and for Malossi MHR Team cylinder, plan was to have both stock baselined on dyno before trying to get best out off them. Shame that it’s not now possible with this “flaky” one.


Sent from my iPhone using Tapatalk

[Muhr]

Then we have something to test forget carbon fiber on. The reason I am interested in testing is that I also thought of trying to make connecting rods like Lamborghini does tests on.

Here is the result of the first attempt! I'm pretty happy with how it looks straight from the mold. Have just scraped off flashing with a knife

[teriks]

Here is the result of the first attempt! I'm pretty happy with how it looks straight from the mold. Have just scraped off flashing with a knife

Chopped tow and epoxi?
Looks like you nailed the process.

[wobbly]

Sniemisto - you will have to ask your plating company the process they use.
In the cylinders I do here my final bore size is 0.1mm oversize, but the plating company then does a super rough honed surface preparation after that to increase adhesion.
Other platers may be different - depending upon what they go for as the final plating thickness.

[Muhr]

Chopped tow and epoxi?
Looks like you nailed the process.

Yes exactly 60% carbon fiber and 40% epoxy by weight. (density 1.4) and 25% extra epoxy that you squeeze out. I can imagine that it is a little more difficult if you do not know the exact volume of the finished product

[Frits Overmars]

In the cylinders I do here my final bore size is 0.1mm oversize, but the plating company then does a super rough honed surface preparation after that to increase adhesion.I know what you mean Wob, but shouldn't that read 0,1 mm undersize? Anyway, most plating companies insist on preparing the bore themselves before plating. The problem arises when they also insist on doing the finishing touch after plating and honing. I know of more than one occasion where they turned perfect cylinders into bin-ready paperweights.
So I insist on them not chamfering anything and leaving the final honing to me.

[Muhr]

Coating Thickness of Nikasil®

In practical use the cylinder walls or sleeves are electroplated with a layer of Nikasil®, typically between 80 and 180 µm thick. Afterwards, the coating thickness is controlled using the custom-configured table-top FISCHERSCOPE® MMS® PC2, further outfitted with a NICKELSCOPE® module and the probe ENW3. Overall, this specialized instrument employs the magnetic measurement method (hall effect).

In the next step the cylinder barrels are milled and honed to improve their sliding characteristics. A final coating thickness somewhere in the range of 25 to 50 µm is aimed for, which requires extremely narrow tolerances to be met in the measurement procedure.

[wobbly]

Sorry Frits you have the wrong end of the stick.
For a 54mm bore they want me to finish to 54.1mm ie 0.1mm oversize , then they hone with what looks like 20 grit.
I dont know what that finished size is prior to plating , but I know Millenium say a coating thickness minimum of 0.05 , so that makes sense.
And yes ,I insist on removing flash in the ducts and doing the chamfers myself , they finally got the idea after I returned 4 cylinders to be replated due to complete shit huge 45* grinding on all the
transfers , when I had asked for none at all - as I just break the edges with a cotton mop.
That is a free lunch - 1/2 Hp repeatable,

Edit , someone always asks .I use Rexcut cotton fiber mounted points to do the finishing.

[DoldGuy]

350961

Managed to get some dyno time today.

Blue:- RG50 Piston-Port/Reed setup

Green:- RG50 Piston-Port/Reed cylinder and head swapped onto the Rotary Valve bottom end.
No other changes to the cylinder carb or ignition timing. Just plugged the inlet and swapped it all over.

Red:- The Rotary Valve setup after some carb and ignition tuning.

Very nearly there, more fiddling next week..... :violin:

TZ, great results from your efforts! Can you share your jetting/timing changes?

[F5 Dave]

TZ, great results from your efforts! Can you share your jetting/timing changes?

Indeed interesting questions, but I'd perhaps question if there were timing changes whether it was optimised on the previous setup. Jetting you would expect.

[TZ350]

TZ, great results from your efforts! Can you share your jetting/timing changes?

Timing, not sure about that as when setting up the Ignitec's base advance it is easy to be a few deg out and that then offsets the whole ignition curve. Jetting, well the main went from 145 to 155 and the needle dropped a clip as you would expect when going bigger on the main. As F5 Dave suggests, I also paid more attention to polishing the ignition curve this time.

But I would not pay any of this to much heed at the moment as the vibration froths the fuel up something wicked. I need to sort the carb mounting out to reduce the amount of fuel being flung out of every orifice at 8,000 rpm. Gets a bit better at higher rpm. Will post a setup rundown when it is all sorted out.

[wobbly]

TeeZee , dont you program in say 15* flat line into the ignition then strobe it on preset rotor/stator lines set mechanically at 15*.
This ensures the base timing is perfect every time.

[Frits Overmars]

Sorry Frits you have the wrong end of the stick. For a 54mm bore they want me to finish to 54.1mm ie 0.1mm oversize , then they hone with what looks like 20 grit.Then you're of course right about the oversize. My experience with more than one plating company is that they insist on removing some material from the bore themselves, the reason being that they want to make sure there are no oil residues in the material that would ruin their bath.

This is also the reason that it sometimes takes weeks before you get your stuff back: they collect all cylinders that have already run and treat them just before the bath has to be replaced anyway.

[TZ350]

TeeZee , dont you program in say 15* flat line into the ignition then strobe it on preset rotor/stator lines set mechanically at 15*. This ensures the base timing is perfect every time.

Yes I do, do that. I used to do it in a pretty haphazard way, of near enough is good enough using thick black marker pen lines. Made it plus or minus a few deg I guess. Although it got me in the ball park and was workable. The curve was then adjusted on the dyno. When the Ignitec said so many deg advance it may not have actually been that in reality. But the motor was happy which was all I was looking for at the time.

This time I took more care with the initial base timing using a properly setup degree wheel and strobe. It was much more accurately done this time. May explain why I had to adjust the old ignition map a bit to match the new motor.

[Condyn]

Are there any guidelines on how far the ring peg must stay from a B port? I have a 69.5 mm bore and the peg is 2-3 mm away from one of the B ports. If it makes any difference, I am using L-ring pistons.

[sniemisto]

For me 2mm sounds like being on the safety limit but I’m no expert.

IAME piston I was looking for is from 2 transfer port engine and might even overlap B port on 5 transfer cylinder. I was not able to get position degree of locating pin. Know that it can be relocated but not feeling comfortable on doing that.
https://uploads.tapatalk-cdn.com/20220420/8c352fbcce0c13cfb9e973869ee71d9a.jpg


TM Mini 60cc kart has locating pin center at back side according photos, but unluckily it is 41.89mm bore so just 0.05 over my limit. Also with L-ring.
Relating to my previous question, is there dyno data on friction loss effect with L-ring compared to plain ring somebody’s willing share?

Thanks for answers on plating. Need to try communicating with plating company. I’m dealing with local 3rd party who is sending big batch of cylinders to plating so don’t have straight contact.

Athena cylinder comes from factory with huge uneven port chamfers, luckily those will be mainly removed during porting.

[yatasaki]

Sniemisto, first find out for which kind of plating is your ring (mostly they are for cast iron liners) and there are two types of rings, steel and cast iron (all plated), steel ones withstand quite a lot percentage of exhaust width. For replacing peg there is no worry, there is material added for central peg or try to find iame, vortex, TM piston with central peg. If you are 0.05 in oversize machine it, they are conical for 0.07mm in 46 mm of lenght.
We are using these pistons in our races and are top offer. There are 5 and 7° conical and radius dome (as on your picture). Radius ones are much safer cause of ring groove being too thin on conical ones.

[TZ350]

.
2Stroke Stuffing's dyno can measure well enough to see actual changes in performance when trying new ideas.

Here is a megaphone exhaust:- https://youtu.be/fiL1FBT8DUs

[Brett S]

Meteor lists smaller sizes than what Mondokart sells online.

https://www.meteorpiston.com/shop/p2327-pistone-kart-mini-60-cc-racing-vers-meteor-o-42-26530?category=68#attr=

[sniemisto]

Yatasaki, thanks for detailed info.
Brett S, good link, there seems to be correct size available for my use. Need to find out ring suitability on plated cylinder.

[husaberg]

.
2Stroke Stuffing's dyno can measure well enough to see actual changes in performance when trying new ideas.

Here is a megaphone exhaust:- https://youtu.be/fiL1FBT8DUs

https://www.youtube.com/watch?v=OOSjs9r6Qpo

https://4.bp.blogspot.com/-Z5zSX9axQfA/UvmJYLQtRNI/AAAAAAAAEZk/5RZhGVgqFgw/s1600/1939+SS+350+DKW+Audi+Museum.jpg

[PVO]

I try:

350861

Probably needs updating. Any ideas?

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

[Frits Overmars]

you click on Neels name and hit view forum posts.
KBs multiquote diesnt like more than two pages it seems ......Husa, when I click on Neels name and hit 'view forum posts', I get no less than 8 pages, but in a format that is not as practical as what you've shown above (see screenshot).
What am I doing differently?
350991

[Hoebra]

@ wobbly,
can you please explain how to use the PS92N Cranecoil with DCCDIP2 Ignitech? You explained it before, but I couldnt find it anymore. I use the DCCDIP2, Software V76. I connected both Ignition Coil Outputs of the CDI (Pin1 and Pin 10) with the Coil, but I think because I use only 1 Pickup theres only 1 channel active. I tried to connect Pickup 2 Input (Pin 20) to Pickup 1 Input (Pin 9), but then theres massive missfire. Theres even only room für 1 Pickup. Could you please make some suggestions how to modify Hard and Software to increase Ignition Power?

[wobbly]

Here is a screen shot of a P2 Race with 1 trigger and two coils firing together. This page is the same setting for your software.
This is how you turn on and off the second channel , and what lobe it operates on in any Ignitech.
The Crane because of its very low primary resistance and very high secondary inductance , forces the ECU voltage converter to output higher Watts ( Joules for Frits ) , but
this is only possible as long as the power supply actually is capable of doing it.
On my test setup the P2 was pulling nearly 5Amps - and the spark at the plug gap was a huge fat blue discharge.
Ive got an MP4 of it but cant post it here.
On petrol this setup on a 250cc open class kart engine made no difference in power , but in a 125 on Methanol with 18.5:1 compression it added nearly 2 Hp at peak.

[Hoebra]

Thank you very much. Even with 1 Output firing I believe to mention cleaner firing under full throttle in low revs. I will post the results.

[husaberg]

Husa, when I click on Neels name and hit 'view forum posts', I get no less than 8 pages, but in a format that is not as practical as what you've shown above (see screenshot).
What am I doing differently?
350991

Hi Frits that how you go to his posts.
I also multiquoted each one individually which took a few extra minutes but i think i have kind of broke it.
you might see a different number of pages ,as I have 20 posts per page you might be set on 10 per page
i might have to clear my multi-quote list as i now have about 40 quotes in it.

[TZ350]

350996

More adventures with the Suzuki RG50

350995

Green line was the original piston port cylinder. Red line after it was converted to rotary valve and the Blue line is RV with a smaller 24mm carb.

The smaller carb Blue line has a strange dip in it. Not sure what that means but it looks like something that has become more pronounced as we have progressed.

The take away looks to be that the smaller carb and inlet tract better suit the rotary valve timing.

[wobbly]

My take is that you have a bunch of power down at 9000 , how often during 1 lap are you down there Vs every gearchange up at 13,000.
Intake length is critical as it affects the mixture curve alot more in a RV over a reed - I think that is where you need to start playing.

[flyonly]

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


Sent from my iPhone using Tapatalk

[F5 Dave]

Rob. To be a fair comparison, did you not have a vibration fuel frothing problem before? Did you cure that on the bigger carb?

As an aside I very occasionally buy a Dirtbike mag ADB. Mostly it is adverts and race reports that I could care less about. They had an article on Lectron carbs.
The Dyno doesn't lie.

The tuner writing the article had some poxy DR650 that only put out 33hp and was measuring very lean on his sensor as a result of after market pipe and filter from memory.

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

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

Sigh.

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

[TZ350]

350997


Rob. To be a fair comparison, did you not have a vibration fuel frothing problem before? Did you cure that on the bigger carb?

Yes you are right. Not a fair comparison. I never cured the fuel frothing problem with the RV at 8k rpm on the big carb. For the smaller carb I fitted a new manifold and wedged some extra rubber under the front engine mount. Less fuel frothing and what bad-ish patch there is has now moved to 10k rpm.

I guess the best comparison to see where we are. Is between the current low fuel frothing small carb RV Blue line and an early old Piston Port/Case-Reed big carb Red line.

I expect to be able to improve the Blue line a bit more.

350998

[wobbly]

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

[TZ350]

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

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

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

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

[lohring]

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


Sent from my iPhone using Tapatalk

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

Lohring Miller

[wobbly]

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

[TZ350]

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

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

351003

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

Off to the dyno.

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

[crbbt]

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

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

Sigh.

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

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

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

[husaberg]

Not in order sorry


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

you click on Neels name and hit view forum posts.

not sure if this link will work
https://www.kiwibiker.co.nz/forums/search.php?searchid=16464070



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

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

Takeaways:

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


I try:

350861

Probably needs updating. Any ideas?


https://deltahawk.com/

One of the lead designers is on this forum :drool:


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

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


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


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


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


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


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


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

350438


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


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

We are all holding thumbs he finds his way!


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

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


Or running a lower exhaust port.....


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

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


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


Based on the dyno curves Frits posted:

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

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


I assume this is with a reedvalve engine?

In what range did you experiment?

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

Cool info, thanks for sharing.


Maybe:

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


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

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


No extra info, sorry.


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

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

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


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

349082

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


He plans to use this:

348929


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

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


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


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

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


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


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


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


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

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


Gasdynamics - Issue 2

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

348379


Nitro,

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

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


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

348298 348299

A better reference is:

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

The download is free.

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


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

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


Condyn,

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

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

Frits,

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

Anyway, let us see what Nitro comments.


Nice discussion Wobbly and Nitro!

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

348284


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


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


Nitro, very good response as per usual.

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

348178


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

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


Clint,

I am still here, a few times a day!

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

Neels


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


Ken,

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

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


https://physics.stackexchange.com/questions/244989/water-vs-air-heat-absorption-capacity


Boost Charging Duration?


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


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

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


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

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

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


Naming of porting events.

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


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



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


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


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

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


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


Lohring, some thoughts:

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

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

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


NASA's attempt:

https://www.techbriefs.com/component/content/article/tb/pub/techbriefs/mechanics-and-machinery/3135


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


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

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


NASA's attempt:

https://www.techbriefs.com/component/content/article/tb/pub/techbriefs/mechanics-and-machinery/3135


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


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


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

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

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


Neil,

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

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


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

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


NASA's attempt:

https://www.techbriefs.com/component/content/article/tb/pub/techbriefs/mechanics-and-machinery/3135


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


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


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

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

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


Neil,

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

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


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

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


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

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


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


Hi Condyn,

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

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

Neels


The ones in post #18 still works.


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

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


Condyn,

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

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

Frits,

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

Anyway, let us see what Nitro comments.


Nice discussion Wobbly and Nitro!

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

348284


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


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


Nitro, very good response as per usual.

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

348178


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

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


Clint,

I am still here, a few times a day!

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

Neels


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


Ken,

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

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


https://physics.stackexchange.com/questions/244989/water-vs-air-heat-absorption-capacity


Boost Charging Duration?


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


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

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


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

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

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


Naming of porting events.

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


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



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


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


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

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

http://www.pit-lane.biz/t6610-50cc-peugeot-103-and-ktm50-tuning


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


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


Frits, maybe this is of interest?

346442


Hydrogen is not dead:

https://www.h2-view.com/story/hyundai-ships-first-hydrogen-trucks-to-switzerland/


For those interested in turbocharging a 2T:

https://www.snowmobile.com/trails/polaris-working-on-turbocharged-2-stroke-snowmobile-engine-65385

It seems Polaris has filed for 9 patents.


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


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

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


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


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


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

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

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


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


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

Neels


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

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

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


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


https://www.autoevolution.com/news/the-ice-shouldnt-die-says-worlds-most-polluting-company-143085.html#agal_0


Hi Husa,

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

And I will keep on doing it.


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


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


Lohring, some thoughts:

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

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

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


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

https://www.autoevolution.com/news/the-ice-shouldnt-die-says-worlds-most-polluting-company-143085.html#agal_0


Hi Husa,

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

And I will keep on doing it.


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


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

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

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


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


This is just so great!

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


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


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

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

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


Condyn,

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

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

Frits,

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

Anyway, let us see what Nitro comments.


Nice discussion Wobbly and Nitro!

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

348284


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


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


Nitro, very good response as per usual.

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

348178


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

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


Clint,

I am still here, a few times a day!

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

Neels


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


Ken,

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

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


https://physics.stackexchange.com/questions/244989/water-vs-air-heat-absorption-capacity


Boost Charging Duration?


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


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

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


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

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

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


Naming of porting events.

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


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



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


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


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

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

http://www.pit-lane.biz/t6610-50cc-peugeot-103-and-ktm50-tuning


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


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


Frits, maybe this is of interest?

346442


Hydrogen is not dead:

https://www.h2-view.com/story/hyundai-ships-first-hydrogen-trucks-to-switzerland/


For those interested in turbocharging a 2T:

https://www.snowmobile.com/trails/polaris-working-on-turbocharged-2-stroke-snowmobile-engine-65385

It seems Polaris has filed for 9 patents.


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


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

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


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


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


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

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

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


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


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

Neels


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

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

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


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


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


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

https://www.motocrossplanet.nl/nieuws-nat/74740/Jan-Witteveen-terug-in-de-motorcross


Thank you!


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


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


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

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


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


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

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

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

Does this answer your question?


DutchPower, I do not fully understand your question:


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



Michael,

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


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


Buongiorno Wobbly, come stai? :laugh:

And the best for the new year to all.


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


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

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


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


Hi Condyn,

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

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

Neels


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

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


Derek,

Absolutely - transfer port and crankcase cooling gives measurable gains.

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


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

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


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



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

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


Released some small bug fixes today.


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

Summary of Major Updates to 2T Suite
9 August 2019

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

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

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

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

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

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


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

339286


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


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

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


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

339193


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

It also adds a contra rotating crank engine layout option.


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

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


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

335784


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


Juergen,

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

Neels


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


This bike had its engine designed by Wobbly using EngMod2T.

335486


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


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


Ief,

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

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

Vannik


Wallace,

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

Cheers
Neels


TZ350,

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

339151


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


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


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


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


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

336498


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


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


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


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



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


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


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


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

I am open to a better word that will work as a single and have a plural :eek5:


335037

How a sim handles blowdown and pretty much all porting:

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

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

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

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

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


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


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


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


https://www.kiwibiker.co.nz/forums/showthread.php/143620-EngMod2T-Q-amp-A


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


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


sae 2004-01-3561


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

331856


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


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


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

331683


Katinas,

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

Vannik


One part of the article.

330586


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

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


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


Ryger Question:

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

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

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




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


Gentlemen,

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

http://tfxengine.com/index.html


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

It makes for interesting results:

318565

[F5 Dave]

Page 2461. Half of them husi.

[husaberg]

Page 2461. Half of them husi.

Pg 2461 should be all of them:niceone:

[jonny quest]

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

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

They have a sensor in crankcase

[TZ350]

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

351004

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

[husaberg]

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

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

They have a sensor in crankcase

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

[Orengo98]

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

Hi all!

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

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

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

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

351009351010351011351012

[Norman]

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

351009351010351011351012[/QUOTE]
///

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

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

[lohring]

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

Lohring Miller

351013

[Orengo98]

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

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

Thank you Norman!

Didn't know that there was a SAE paper on this engine! My university doesn't have access to SAE papers and this one seems that's not posted on JSTOR. But looking on JSTOR, I found another paper supervised by the same professor and Montesa consultant, about throttle body and transfer fuel injection for two strokes, in 1986! It's called: Low-Pressure Discontinuous Gasoline Injection in Two-Stroke Engines 860168, if someone wants to read it. Seems that the system was installed on the Montesa Crono 350 of the professor.

By the description of the paper on the motor with the additional cylinder, seems that it has nothing to do with a compressor or supercharger (at least an efficient one) as all the magazines of the era said. Also, that additional cylinder seems not to be connected in any way to the motor, so only the underside is working. So seems that my suspicions on the system were right. I decided to plot the crankcase volume of that motor, knowing the bore, stroke and crank length. As I don't know the minimum crankcase volume, I didn't use units on the graph. Also, once plotted I realized the conrod of the additional cylinder is a bit shorter than the standard one, so the graph is going to be a little bit off.

The graph shows two main differences, first the maximum volume of the crankcase is not reached at TDC, but around 45º earlier, and that the difference between maximum and minimum crankcase volume is a bit greater on that configuration.

351014

[PVO]

Not in order sorry



you click on Neels name and hit view forum posts.

not sure if this link will work
https://www.kiwibiker.co.nz/forums/search.php?searchid=16464070

How do you get the results to show the full Post? I’ve viewed user posts this way before but all I can see is the first couple sentences of the post without clicking on it?

[husaberg]

How do you get the results to show the full Post? I’ve viewed user posts this way before but all I can see is the first couple sentences of the post without clicking on it?

You will have to click onto the posts, i then multi quoted each post and then used the quoted one post in each thread then pasted them together
it took about 30 minutes though.

The first time i tried it I thought there was a limit on the number of posts but it was dropping posts from other threads.:Oops:

[Muhr]

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

351004

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

I think people mean that if you have a car with a trailer and a constant uphill. If you then load the trailer until the car maintains a constant speed of eg 30km / h with full throttle. If you then start applying the brake on the trailer alone, will the load on the tow hook increase then?

You have a rotating mass in and around an engine to be able to start measuring a power, you have to overcome that friction without being able to credit it as power.

If you then think of eg crank piston and connecting rod and clutch of eg 3kg and an inertia of eg dia 60mm and a braking force of 1000rpm / s (3m / s2) a gear ratio of say 1:10 from crank to drum.
becomes about 2.8 NM of gravy on top of the reading if you do not compensate.

I may be way off track but my first thought.

[wobbly]

To me it seems that Stuffings dyno is set up to allow a certain rpm , then it reads the torque required to slow the engine down.
I know technically this will read accurate numbers , but why do something no one else in the world is doing , just for the sake of it.
It means the engine is initially free reving with no load , the opposite of what every other Eddy Current software does.
Using Eddy Current means you could easily replicate what inertia dynos do , that is the engine does exactly what it does on a track , accelerate faster as it makes more power on WOT from lower rpm..
ie its real

[ken seeber]

I just wish Alex would just set the eddy current dyno to a series of set rpms, say 12, 14, 16, 18, 20k etc. Or even just one or two set rpms. The thing should be eminently capable of doing this. Takes away any doubt as to any dynamic or inertia effects.

However, it’s his project though and it is interesting.

[OopsClunkThud]

maybe his target load case is being towed up to top speed and then doing a hill climb with an ever increasing slope...

[Vannik]

What Stuffing is doing is known in the engine world (well, turbo diesel world) as a lug down curve. The diesel guys use this to better simulate a big truck hitting an uphill stretch. This way the turbo does not have to build boost as in an acceleration run. There is a substantial difference in the acceleration curve and lug down curve on these turbo diesel engines and their motivation is understandable. I would really like to see Stuffing do at least one set of acceleration curves compared with a set of lug down curves to prove that in his case they are the same. I have my doubts though.

[SwePatrick]

I actually think that if he did a regular upwards pull like IRL usage he would gain either more power or more rpm.
This due to during the pull engine is clearing its throat and build heat to condensate fuel better, allowing for cleaner and more complete burn at the end of the pull.

But, dynosoftware if written correctly and correct data is typed in, the power should be correct if doing either upwards or downwards pull if dynoing an electric motor that doesn´t have same problems as a rich running nitro/meth twostroke.

[TZ350]

351018 351017

Speedpro resurrected his old MB100 Bucket engine into a FZR250 frame. Makes a good 24rwhp. Speedpro took it to Hampton last Sunday but he elected to ride his fuel injected twin instead.

I rode my rotary valve Suzuki RG50. I had a very enjoyable day but the 50 was not so happy. Sure it lasted, but it had fits of stomach ache all day. I could not understand why it was un happy. It would start off sweet then become very bilious as the race progressed.

Before the race I had wondered about the ability of the RG50 water pump so I had fitted an electronic cylinder head temperature gauge but true to form it packed up out on the track. The temperature gauge worked OK in the pits, nothing on the track. Ok again back in the pits. It would run good again until it got out onto the track. Changed it for another new one, same issue. Vibration?

351019 351020

Also none to sure about my choice of total loss battery and the porcelain insulator cracked in the plug. There were a host of other clues, like the engine vibrating through the rev's but not every time and the engine going "pop" sometimes when revved out and it took a few moments to recover. Also the engine note changed noticeable when cornering to the left. Induction noise reflected off the road surface or fuel draining away to one side in the carb? Thought it may be fuel starvation under load. So I took to the float needle seat with a battery drill and opened up some other holes around the float needle for good measure. No real improvement.

Last race the gear lever broke. DNF, maybe should have kept going in 4th, the gear it was stuck in and clutched out of the corners for a finish.

Plenty to think about but one thing for sure, when it ran well it ran very well.

[wobbly]

But Neels , my assertion is that a race bike engine will never see that sort of " lug down " scenario in its life.
In the real world this engine will be accelerating almost constantly , with only aero load substantively increasing with velocity to reduce the rate.

[TZ350]

The graph shows two main differences, first the maximum volume of the crankcase is not reached at TDC, but around 45º earlier, and that the difference between maximum and minimum crankcase volume is a bit greater on that configuration.

351014

Good work graphing it out. My take on it is, that the green line showing the extra volume from the slave piston in the graph before TDC makes sense. As the point of lowest crankcase pressure in a standard two stroke engine is noticeably before TDC. The slave piston in the graph just increases the crankcase volume to take advantage of inhaling more mixture at that point. They could have achieved the same thing with a very sucky pipe and much more static crank case volume. But I guess at the time people did not understand the potential of sucky pipes and were focused on crankcase pumping efficiency.

351021

EngMod2T simulation of the crankcase pressure cycle for my 110cc engine. There is a significant low pressure area before TDC and the pressure at TDC is a bit higher. I guess the higher pressure at TDC is brought about by the ram effect of the moving column of gas in the inlet tract.

For performance two strokes. The old "Transfer Efficiency" thinking was pumping the mixture up through the transfers with a tight crankcase volume using crank stuffers etc., all to get a high pumping efficiency delta. I guess you could also use a slave piston to help with this high crankcase volume delta objective.

Current thinking is to not worry so much about crankcase pumping efficiency but to have a much bigger crankcase volume for the sucky pipe to suck the mixture up from and through well formed transfers for better "Transfer Efficiency".

Sucky pipes rely on good transfer flow control and port angles so the fresh mixture does no short circuit wastefully out of the exhaust port during the preliminary transfer phase. See "Transfer Port Theory" https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner/page2000 Transfer flow control is a big part of "Trapping Efficiency". Also the ramming return exhaust pulse plays a large part in "Trapping Efficiency" too.

[Vannik]

A very good presentation on using cylinder pressure data, and yes, it is for a 4T engine but they use the latest instrumentation and software from AVL. It will require you to register at SEMA but it is free.

https://www.sema.org/news-media/enews/2022/14/ettn-webinar-optimizing-cylinder-pressure-obtain-peak-engine-performance

[TZ350]

351023

I need help with this. I know that wind across the bell mouth causes issues. Does this windshield look Ok or does it look like it might be causing me problems? What would a good windshield look like?

Advice from anyone who has experience with a rotary valve carburetor running around naked out in the breeze would be very welcome.

[pete376403]

I need help with this. I know that wind across the bell mouth causes issues. Does this windshield look Ok or does it look like it might be causing me problems? What would a good windshield look like?

Advice from anyone who has experience with a rotary valve carburetor running around naked out in the breeze would be very welcome.

Have a look at Harry Klemms Bighorn racer (rotary valve.) Some good pics on the website including how he shields the carb http://www.klemmvintage.com/bighorntech.htm

[Muhr]

I need help with this. I know that wind across the bell mouth causes issues. Does this windshield look Ok or does it look like it might be causing me problems? What would a good windshield look like?

Advice from anyone who has experience with a rotary valve carburetor running around naked out in the breeze would be very welcome.

Thinks that a low pressure area can potentially build up behind the shield which in the worst case can start to fluctuate. Based on that, an opening in the direction of travel is a more stable environment.

[wobbly]

Having an extended length of carb bell mouth hugely affects the intake tuned wave response. You are way better to have a simple airbox with a forward facing intake that has the enclosures flat face no less than 20mm
from the carb bell end. This you can model in EngMod easily.
I have tested the effects on Hines World Champ winning 250 Superkart , when the engine was on the right and thus the carbs all but touched the seats flat side .
And at 20mm away it has no effect on the carbs fuel standoff and thus power , at full noise.

[Muhr]

Having an extended length of carb bell mouth hugely affects the intake tuned wave response. You are way better to have a simple airbox with a forward facing intake that has the enclosures flat face no less than 20mm
from the carb bell end. This you can model in EngMod easily.
I have tested the effects on Hines World Champ winning 250 Superkart , when the engine was on the right and thus the carbs all but touched the seats flat side .
And at 20mm away it has no effect on the carbs fuel standoff and thus power , at full noise.

Could not help but not include such an option!

[F5 Dave]

Has to have some benefit if you put it in the kitty litter too. Bolted to sidecover holes could have crash resistance plus the inlet out of the dirt. .

[pete376403]

The carb shield on Harry Klemms 350 Bighorn (R/V) racebike

[wobbly]

In EngMod you can vary the volume and the intake tube length/intrusion/size to explore Helmholtz effects.

[TZ350]

351042

After a lot of dyno time and a days abuse at Hampton Downs the piston looks remarkably good. None of the deto damage or seizure marks that I was expecting.

351040

At 80% bore width, the exhaust port looks Ok too.

351043

A fly in the ointment looks to be that the ring ends are gouging the cylinder as the exhaust port top edge pushes them back into the grove.

What I need is a single ring piston with the ring gap at 6 o clock. The piston I am using now has two rings with the gaps at 5 and 7 o clock.

351041

When I got the rotary valve going I just plugged the carb inlet rubber and transferred the original cylinder complete over from the piston port case reed engine.

Now in the interests of science I am going to remove the reed block and block up the inlet tract and inlet port with epoxy. It will be interesting to see what the extra case volume does.

[TZ350]

351044

20:1 compression ratio and supercharged, what could go wrong? nothing apparently. https://youtu.be/lyDOWiSprtE

[DoldGuy]

351042

After a lot of dyno time and a days abuse at Hampton Downs the piston looks remarkably good. None of the deto damage or seizure marks that I was expecting.

351040

At 80% bore width, the exhaust port looks Ok too.

351043

A fly in the ointment looks to be that the ring ends are gouging the cylinder as the exhaust port top edge pushes them back into the grove.

What I need is a single ring piston with the ring gap at 6 o clock. The piston I am using now has two rings with the gaps at 5 and 7 o clock.

351041

When I got the rotary valve going I just plugged the carb inlet rubber and transferred the original cylinder complete over from the piston port case reed engine.

Now in the interests of science I am going to remove the reed block and block up the inlet tract and inlet port with epoxy. It will be interesting to see what the extra case volume does.

TZ, from the pictures posted, how is the Intake Side / C Port being feed? I’m sure to be missing something as it appears to only use the A/B transfers.

[Condyn]

Tz, I am in the same boat as you. I use a 75% chordal exhaust port, and only have trauma on the rear wall at ring end gap at timing edge height. Oddly, I have found that switching to the cheaper cast version piston which also uses an L-ring, has almost entirely eliminated this issue.

[F5 Dave]

TZ, from the pictures posted, how is the Intake Side / C Port being feed? I’m sure to be missing something as it appears to only use the A/B transfers.
Have a look at an 80s RM or PE engine, it will become clear.

[DoldGuy]

Have a look at an 80s RM or PE engine, it will become clear.

F5, I’ve had the early RM’s & PE’s and fairly familiar with the Piston Port / Case Reed design, but I thought he was running a Rotary with Carb mounted at the Disc, is it a dual carb setup?

[andreas]

80% exhaust width, it will come at a cost. I had it working with a L-ring ( if this, or ring material helped, not known). Just changing the ring gap location , I don't think will do much, furthermore it will present a big risk of ring/cylinder havoc, as the C port divider, I think, is too small to support the gap.
The induction system on these suzukis I'm convinced is very good, the only drawback being that wonky C-port feed from the B-ducts. So if the rotary thing is permanent, then it would be a good idea to give it a proper C-duct.

[F5 Dave]

F5, I’ve had the early RM’s & PE’s and fairly familiar with the Piston Port / Case Reed design, but I thought he was running a Rotary with Carb mounted at the Disc, is it a dual carb setup?

Reread the very post you quoted for TZ350.

[DoldGuy]

The induction system on these suzukis I'm convinced is very good, the only drawback being that wonky C-port feed from the B-ducts. So if the rotary thing is permanent, then it would be a good idea to give it a proper C-duct.
Thanks for clarifying as this answered my question.

[F5 Dave]

Speaking for Rob, I think an important Part of the experiment was a direct comparison with the same barrel. Interesting swap of induction.

[wobbly]

Yea but all it confirmed was that the original crap reed assisted piston port was exactly that , crap , and that an EngMod optimized RV was exactly as it should be - far superior.
But as Rob said earlier on , all it needs now is an optimized pipe and then the real capabilities will be realized.

[husaberg]

Yea but all it confirmed was that the original crap reed assisted piston port was exactly that , crap , and that an EngMod optimized RV was exactly as it should be - far superior.
But as Rob said earlier on , all it needs now is an optimized pipe and then the real capabilities will be realized.

I am not totally sure but Honda were running case reed on the works CR's in thee mid 70's Marty Smith Era.
Suzuki went with their system as likely the best driveability compromise whilst avoiding whoever's patents had the Case reed.
Anyone know who had the case reed patent?
i remember old 50's two strokes with carbs feeding crankcase and mayb chainsaws i think some scooters, but on performance bikes?

I just dug up the honda one and i was Suzuki style.
351046

[andreas]

Yea but all it confirmed was that the original crap reed assisted piston port was exactly that , crap , and that an EngMod optimized RV was exactly as it should be - far superior.
But as Rob said earlier on , all it needs now is an optimized pipe and then the real capabilities will be realized.

I'm not saying it works as well as a rotary valve, it's a remarkable project from Rob, but look at the picture- it's completely standard, How can it be compared to a purpous built RV.

[Strokerhaus]

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

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

Ron Gardner who made the first carb that I know of with a flat on needle, which Lectron and other's copied, started in 1947 exactly that way with a standard carb. In his case it was an AMAL carb with a round needle and flat on . Yes the flat on the needle does atomise the fuel better as it forms a spray bar, and yes you do have to prevent the needle rotation.

I have a brace of Gardner's on my TZ and got down on a dyno to A/F ratios of 15:1 with no sign of det before I chickened out.

[Frits Overmars]

351046Just when I thought I was starting to understand two-strokes... :facepalm:
351047

[Muhr]

Ron Gardner who made the first carb that I know of with a flat on needle, which Lectron and other's copied, started in 1947 exactly that way with a standard carb. In his case it was an AMAL carb with a round needle and flat on . Yes the flat on the needle does atomise the fuel better as it forms a spray bar, and yes you do have to prevent the needle rotation.

I have a brace of Gardner's on my TZ and got down on a dyno to A/F ratios of 15:1 with no sign of det before I chickened out.

Here with a regular needle (round) note that the exhaust temp and lambda are on the same graph, see left / right

[husaberg]

Just when I thought I was starting to understand two-strokes... :facepalm:
351047

It was 1974 those were different times.....:msn-wink:So i am told.
They had Fuel injection at that time as well on some of the Honda MX bikes


Found some pics
351049351050
351051
351052351053

[wobbly]

He might be onto something Frits - I will have a go at putting the rear cone at the front of the pipe.

[Grumph]

He might be onto something Frits - I will have a go at putting the rear cone at the front of the pipe.

The article says they're "unique" i vote for them to stay that way.

[SwePatrick]

80% exhaust width, it will come at a cost. I had it working with a L-ring ( if this, or ring material helped, not known). Just changing the ring gap location , I don't think will do much, furthermore it will present a big risk of ring/cylinder havoc, as the C port divider, I think, is too small to support the gap.
The induction system on these suzukis I'm convinced is very good, the only drawback being that wonky C-port feed from the B-ducts. So if the rotary thing is permanent, then it would be a good idea to give it a proper C-duct.

You can run just fine with ring gap location 6 o´clock, straight above a unbridged c-port, nemas problemas. :headbang:

[andreas]

It doesn't look very unbridged.

[Larry Wiechman]

The technical writing found in the dirt bike comic books rivals the quality of the information found on Fakebook.

[TZ350]

351057

Reed block fills up quite a bit of the crankcase.

351055

For more crankcase volume I removed the reed block and filled up the inlet tract.

351056

Blue line is with reed block in place, Red line is extra crankcase volume with the reed block removed. No other changes at all.

I have some 10mm longer rods coming, it will be interesting to see if even more crankcase volume helps.

I probably can only get away with this on my rotary valve engine.

[SwePatrick]

It doesn't look very unbridged.

Yes,, and IF you can run it with no bridge, you can certanly run it with a small bridge also.

[SwePatrick]

Injectionguys!

I have had a though for a longer while.
I know when you got injection the demands of a carburetor disappears.(having to big causes function of carb to be disturbed)
The atomisation of fuel is held by the injectors and fuelpressure etc etc.

And, a supercharged 4stroke with throttleblade on atmospheric side cannot be to big.

So my thought:
REALLY oversize the reedcase(or slide if possible) and then run a huge inlettract, say 50mm on a 125cc engine, this to make sure there are no restrictions for air to travel into crankcase, well as little as a reed engine can provide that is ;)

Anyone thought the same?

[husaberg]

Injectionguys!

I have had a though for a longer while.
I know when you got injection the demands of a carburetor disappears.(having to big causes function of carb to be disturbed)
The atomisation of fuel is held by the injectors and fuelpressure etc etc.

And, a supercharged 4stroke with throttleblade on atmospheric side cannot be to big.

So my thought:
REALLY oversize the reedcase(or slide if possible) and then run a huge inlettract, say 50mm on a 125cc engine, this to make sure there are no restrictions for air to travel into crankcase, well as little as a reed engine can provide that is ;)

Anyone thought the same?

I thought differently until i figured out KTM might pay for it......:bleh:

[TZ350]

It doesn't look very unbridged.


Yes,, and IF you can run it with no bridge, you can certanly run it with a small bridge also.

351058

80% and I would very much like to go to 85% or 95% with a bridge if I have too. But I very much prefer the single exhaust port.

351059

I have just realized that the damage on the back of the cylinder opposite the exhaust port took some time to develop. The cylinder has seen several race meetings and a number of hours on the dyno.

So life expectancy at 85% may be acceptable.

[F5 Dave]

Nice work Rob. What are the ports at the barrel like? Did you flush them? Would have been interesting with those closed off first, and then with block removed.

[Grumph]

Injectionguys!

I have had a though for a longer while.
I know when you got injection the demands of a carburetor disappears.(having to big causes function of carb to be disturbed)
The atomisation of fuel is held by the injectors and fuelpressure etc etc.

And, a supercharged 4stroke with throttleblade on atmospheric side cannot be to big.

So my thought:
REALLY oversize the reedcase(or slide if possible) and then run a huge inlettract, say 50mm on a 125cc engine, this to make sure there are no restrictions for air to travel into crankcase, well as little as a reed engine can provide that is ;)

Anyone thought the same?

You're working along the lines I've observed in fourstrokes. I've ported heads for literally decades but the game changed when injection became common.
Previously you had to maximise flow without dropping gas speed to the point where a carb wouldn't be in it's effective gas speed band. Now it's huge ports and simply go for maximum flow at the required valve lift - because the injection atomises the fuel for you. Too easy.

So given that gas speed is no longer a factor in the choice of diameter or length of the inlet tract, do you then have to recalculate on the basis of resonance frequencies for the inlet tract and case volume ? Would a bigger inlet with less restriction mean a reduction in case volume ?

[TZ350]

What are the ports at the barrel like? Did you flush them? Would have been interesting with those closed off first, and then with block removed.

Inlet ports were filled flush with the bore. Yes it would have been interesting to do it more step wise but it all takes time and effort. EngMod tells me that there will be some power advantage if I can go extra wide on the exhaust port (85%) and reduce the duration from 200 to 194 deg.

[TZ350]

Injectionguys! I know when you got injection the demands of a carburetor disappears.(having to big causes function of carb to be disturbed) The atomisation of fuel is held by the injectors and fuelpressure etc etc.

So my thought: REALLY oversize the reedcase(or slide if possible) and then run a huge inlettract, say 50mm on a 125cc engine. Anyone thought the same?

Good idea. A lot of TPI fuel is in the transfers but a fair proportion finds itself in the crankcase too so you would have to allow for that.

I know its not exactly the same idea as yours but we tried this big inlet short inlet tract.

351060

Turns out, with the bigger inlet we needed the extra kinetic energy of a longer inlet tracts ramming effect to stop excessive blow back.

351061

We needed to go to the longer inlet tract to avoid fuel being ejected out nearly a meter.

On a two stroke you will definitely need to balance the inlet diameter with the inlet length, fuel injected or not.

More of the story can be found here:-
Every one knows there is a relation ship between Tuned-Length and RPM but there is also a relationship between Inlet-Tract-Length and Diameter and Inlet-Closing-Point, all three things have to work together with the crankcase volume.

[SwePatrick]

You're working along the lines I've observed in fourstrokes. I've ported heads for literally decades but the game changed when injection became common.
Previously you had to maximise flow without dropping gas speed to the point where a carb wouldn't be in it's effective gas speed band. Now it's huge ports and simply go for maximum flow at the required valve lift - because the injection atomises the fuel for you. Too easy.

So given that gas speed is no longer a factor in the choice of diameter or length of the inlet tract, do you then have to recalculate on the basis of resonance frequencies for the inlet tract and case volume ? Would a bigger inlet with less restriction mean a reduction in case volume ?

Yes, i´ve been tuning and porting a lot of faulstrokes earler in the years.
And i see similarities in a two stroke and a supercharged 4t engine.
Underside of the piston is the supercharger in the 2t case.

And yes, some sort of resonance tuning is probably a demand, as one need some sort of ram charging after piston is in TDC.
Basically a bigger inlet needs longer throat to maintain resonance.
Coming from speakerbuildin there is less restriction in bassports when going up in diam even though length is greater.(it minimizing blow sounds when going up in diam)

[JanBros]

Underside of the piston is the supercharger in the 2t case.



a lot of people will disagree including me. a 24/7 open intake wouldn't work if you were right.

[Frits Overmars]

Basically a bigger inlet needs longer throat to maintain resonance.Or a shorter inlet timing, which I prefer.

[wobbly]

The underside of the piston is only working as a supercharger in the case of a 2T lawnmower engine.
Around BDC in a race engine the pipe diffuser sucking on the transfers creates a huge depression in the case , and it is this that begins to open the reeds.
If the inlet length is tuned correctly for the rpm , it then produces a positive pressure ratio at the same time on the opposite side of the petals.
Near TPC , the reeds are open , and the piston rising has had almost nothing nothing to do with this state in the 2T cycle.
This scenario is the naturally occurring " supercharging " effect in a 2T race engine.

This gives the lie to some peoples idea that there is " flow " thru the intake , into the case , and out thru the transfer ports - doesn't happen.
The total amount of mixture stored in the transfer ducts is greater than the swept volume of the cylinder , so it is this that is drawn upon by the pipe action - even accounting for a Volumetric Efficiency above 100%
It is only the pressure differential across the ports, at the bore , that is transmitted to the case.

[F5 Dave]

So I'm home yesterday packing and stacking boxes for the dreaded carpet next week, when the old fella who does our lawns (my father in law) shows up.

To my shame of marrying into this family, I realise in horror that he is using a 4 stroke lawnmower. :oi-grr:

I'm going to have to have a word with him aren't I?

[OopsClunkThud]

I've been kicking this exhaust port shape around for months now and I'm finally going to give it a try.

Thinking is that by keeping the top of the main port width to ~50% of bore the roof can be flatter and the top corner radius smaller. This gives more blowdown area before the aux ports open and the width that is lost from the main is picked up by the aux ports so more blowdown after the aux are open as well. Should be nicer on the rings too.

70% follows FOS port shape concept:
351076

Guides at 0.5, 1.0, 1.5, and 2.0 of bore assure consistent taper
351075

Main port angled down 20° at cylinder wall, Aux ports are 0° for maximum flow in blowdown.
351074

[Vannik]

I've been kicking this exhaust port shape around for months now and I'm finally going to give it a try.

Thinking is that by keeping the top of the main port width to ~50% of bore the roof can be flatter and the top corner radius smaller. This gives more blowdown area before the aux ports open and the width that is lost from the main is picked up by the aux ports so more blowdown after the aux are open as well. Should be nicer on the rings too.

70% follows FOS port shape concept:
351076

This is what the RC guys run:

351077

[wobbly]

Two issues I can see with the concept.
1st - the smaller blowdown initial wave front exiting the main port will be dumping into a relatively greater duct volume , reducing its amplitude.
And thus the diffusers efficiency
This is the very reason the Aux need to have sufficient height stagger, to allow a steep wave front of high amplitude to initially exit down the duct.
The Aux simply allow greater blowdown flow to occur before TPO.

2nd - Constant taper is not what is needed. Best initial flow is gained with a 25* down angle that then turns into a convex radius, this "downward facing
hump ",is combined with a ski jump floor , where the initial exit is perp to the bore. This creates the smallest main duct area at the point where the Aux ducts enter from the side. Thus reducing a sudden huge total cross sectional area change.

I will run it thru the midnight 3D mind calculator , before dreams of Jennifer Annistons arse and Mick Doohans NSR take over.

[Frits Overmars]

I've been kicking this exhaust port shape around for months now and I'm finally going to give it a try. Thinking is that by keeping the top of the main port width to ~50% of bore the roof can be flatter and the top corner radius smaller. This gives more blowdown area before the aux ports open and the width that is lost from the main is picked up by the aux ports so more blowdown after the aux are open as well. Should be nicer on the rings too.
Main port angled down 20° at cylinder wall, Aux ports are 0° for maximum flow in blowdown.
Because of the necessary corner radii a port width of 70% of the bore is the optimum (not the maximum) value if there is just one single exhaust port.
But when auxiliary exhaust ports come into play, things change and narrowing the main port in favour of the auxiliaries makes sense.

Will your oblique bridges between the main and the auxiliaries be nicer to the ring? I need to think about that.

I wonder why you maintained the main port width below the blowdown area and why you put the port floor at BDC, by the looks of it.
It will induce more turbulence in the exhaust duct during the blowdown phase and it increases the risk of mixture short-circuiting from the A-transfers into the exhaust.
Raising the exhaust floor will also reduce the duct volume which helps concentrating the exhaust pipe energy at raising the cylinder pressure.
And finally a raised exhaust floor helps the return flow of washed-through mixture over the piston. Remember, as the transfer ports are about to close, the exhausts ports become transfer ports themselves.

A consistent 2,5° taper in the exhaust duct is fine, provided you use the blowdown area as the initial area.

A 0° downward port angle will give the maximum cross flow area but it won't give maximum flow. 25° is better.
Incidentally that's also the maximum angle you can give the auxiliary duct floors because of the A-transfer duct roofs directly underneath that also have a 25° axial angle.

[Frits Overmars]

This is what the RC guys run:
351079
Horrible main port shape, and it makes you wonder why the bridges are there at all; most RC engines do no even have a piston ring.
We use the exhaust duct below for our 6,5 cc MB40 engine. Over the past 25 years it collected more world titles than all its competitors put together so it can't be too bad.
351078

[philou]

for an engine with this configuration. on which side to place the opening of the segment.
opening on the up or down side of the piston?

351080351081

[Frits Overmars]

for an engine with this configuration. on which side to place the opening of the segment. opening on the up or down side of the piston?I must admit it took me some time to discover what you meant by 'an engine with this configuration' until I finally noticed the sideways exhaust port. But that shouldn't make any difference.
The best place for the ring gap is diametrically opposed to the exhaust port, also known as the six o'clock position. And that goes for all two-stroke engines, unless a very wide port at that position makes it undesirable.

[OopsClunkThud]

1st - the smaller blowdown initial wave front exiting the main port will be dumping into a relatively greater duct volume , reducing its amplitude.
And thus the diffusers efficiency
This is the very reason the Aux need to have sufficient height stagger, to allow a steep wave front of high amplitude to initially exit down the duct.
The Aux simply allow greater blowdown flow to occur before TPO.


On the first issue I think I'm missing your point. This concept has a larger initial blowdown area than the 70% port and it dumps into a smaller main port duct volume. This should then give better amplitude and diffuser efficiency, or at least that was my thinking.

Point taken on the second issue. I was including the aux and main port cross sections in my "taper" from port area down to 75% of port area at 1.5 bore distance, and the intent was to make sure there was not an abrupt change, but I need more work where they first come together. 25° down on the port roof will help with that.



I wonder why you maintained the main port width below the blowdown area and why you put the port floor at BDC, by the looks of it.
It will induce more turbulence in the exhaust duct during the blowdown phase and it increases the risk of mixture short-circuiting from the A-transfers into the exhaust.
Raising the exhaust floor will also reduce the duct volume which helps concentrating the exhaust pipe energy at raising the cylinder pressure.
And finally a raised exhaust floor helps the return flow of washed-through mixture over the piston. Remember, as the transfer ports are about to close, the exhausts ports become transfer ports themselves.


The bottom of the main port was widened to bring up the STA of the total exhaust (funny to stick to this convention while casting off others). It looks deceptively wide because the top of the port is only 50% of bore, but the bottom is 60% of bore. I'm working around some cylinder studs on this engine limiting how wide I can go with the aux but it also keeps the A ports well away from the main exhaust. I'll have to mess with raising the floor.



A 0° downward port angle will give the maximum cross flow area but it won't give maximum flow. 25° is better.
Incidentally that's also the maximum angle you can give the auxiliary duct floors because of the A-transfer duct roofs directly underneath that also have a 25° axial angle.


This is an intentional deviation. In my CFD work I found that 0° flowed better at high pressure ratio (blowdown) but 15° or more flowed better (and with less large scale eddies) once the flow fell below sonic. I'm choosing to optimize the aux for the blowdown conditions and letting it choke some later when fresh charge would be more likely to enter.


This is what the RC guys run:

351077

I somehow find it reassuring that no idea is new

[wobbly]

i was misinterpreting somewhat the 1st critic of your layout i think , as i would have thought the "new " aux ports should be the shape used with the old 70% configuration. Thus in the your new regime the huge side ducts would create a commensurately huge area increase, where they enter the main duct.
That was my concern.
But a word from the wise ( Jan , not me ) lifting the floor only works if the Aux area , and thus the Blowdown STA is fully optimized. I have not yet tried exceeding the 3mm lift that was tested with success at Aprilia ( nor seen any dyno evidence that higher is better ) so maybe this is your mission should you choose to accept.
Its something I need to convince a customer its worth putting in the effort/time/money. But something that has become a norm in recent years of Sim use is that the full Ex STA appears to be pretty irrelevant when compared to optimizing the Transfer and Blowdown STA numbers.

[TZ350]

351099 351100

On the piston port configuration I had to cut the piston skirt away to get enough inlet timing possible (180deg duration). I suspect the marks in the cylinder may be from the short skirt piston rocking and gouging the cylinder with the ring (maybe??). Now the engine is in rotary valve configuration (220deg duration) I am fitting a full skirt piston and new cylinder, hopefully this will eliminate the cylinder damage. Time will tell.

[F5 Dave]

Wow. I never saw that in 20 years of running those engines. But I never cut the Piston, just lowered the port. had heaps of area with 28mm carb.

[TZ350]

Wow. I never saw that in 20 years of running those engines. But I never cut the Piston, just lowered the port. had heaps of area with 28mm carb.

Lowering the port would work but is hard work. With a lowered port the piston has only just fully opened the port before starting to close it again. Cutting the piston got an easy 180 duration with the port fully open for a considerable time. I have not done a "time/area" analysis between them but your way may have been better. Certainly better mechanically.

[F5 Dave]

It doesn't take long with a air grinder. Especially as you've cut the crazy long inlet manifold off with a grinder so you can tack weld & Devcon an ally plate to fit a conventional rubber inlet manifold to rather than the tube type creating a short but well formed inlet (well as best can be with a hole in the bottom of it for the case reed, but there you go, compromise compromise).

[TZ350]

.
Dyno time ...... vrooom vrooom WOT maxed out in 6th ... back wheel stopped turning around. So much for my last new cylinder ....... :Oops:

[F5 Dave]

Geez, what kind of piston do you run. I never, like never seized an RG on std or KX piston.

[TZ350]

Geez, what kind of piston do you run. I never, like never seized an RG on std or KX piston.

Not sure, some 41mm after market piston. Lower crown height and radius compared to the original RG50. I need to take it apart first for a look. I might get away with boring it for the 43mm KX60 piston.

[peewee]

what kind of welder do you fellas use ? just barely i got this new tig and havent yet tried it. perhaps you know of fronius


https://i.ibb.co/d5ghvNh/20220519-215947.jpg

[philou]

Fronius :love:

for me it is one of the best brands

[sniemisto]

Did some testing today with 15l/minute electric water pump vs Derbi standard mechanical. Electric with reversed flow was almost identical with stock and with normal flow direction it was slightly worse.

https://uploads.tapatalk-cdn.com/20220521/724f09f7bfe04ec98d52a52fd5fe4a52.jpg

Solid: Derbi Mechanical
Dash: Bosch electric pump with reversed flow sucking water out around exhaust duct.

I see electric water pumps on almost every Freetech bikes and with both flow directions. What I’m missing out, is there some track condition gain I won’t see in short dyno runs..?

[philou]

Engine €2 or €3 ?

[sniemisto]

€3


Sent from my iPhone using Tapatalk

[peewee]

Fronius :love:

for me it is one of the best brands

so far i have three fronius machines for all welding types and theyre great. i even sold my miller :eek:

[philou]

so far i have three fronius machines for all welding types

I hate you :oi-grr:

[wobbly]

Having the cold water feeding in under the Exhaust duct is just as wrong as having all the cold water going into the head.
This change was made 2 homologations ago in KZ engines , where the simple but vey inelegant solution was to feed the cold water surrounding the crank , up thru a hose , and into the cylinder
above the top of the Exhaust duct from one side.
The best scenario is to have all the cold water enter the cylinder over the boost port , then run around the bore over the tops of all the transfers - cooling these first.
Then a portion of the return should be directed to a pair of small exit holes on each side under the Exhaust , the remining flow then exits up into the Exhaust side of the head , around the insert and back to the radiator.
This alone is an instant 1 to 1.5 Hp in 50.

Water flow and cooling in general is a very much ignored source of " free " power gains.
Having water flowing around the entire length of the Exhaust duct , where the plugging charge is retained , is super simple , but never done properly as far as I have seen.
These slots in the Exhaust exit surface ( done by hand many years ago in the pit with a battery drill and file ) cools the back of the spigot as well , and reduces the background deto level by around 20% - allowing alot leaner egt level at full power as a result.
This is much easier now with a small 75% exit area and a 6 axis CNC .

[Vannik]

Having the cold water feeding in under the Exhaust duct is just as wrong as having all the cold water going into the head.
This change was made 2 homologations ago in KZ engines , where the simple but vey inelegant solution was to feed the cold water surrounding the crank , up thru a hose , and into the cylinder
above the top of the Exhaust duct from one side.
The best scenario is to have all the cold water enter the cylinder over the boost port , then run around the bore over the tops of all the transfers - cooling these first.
Then a portion of the return should be directed to a pair of small exit holes on each side under the Exhaust , the remining flow then exits up into the Exhaust side of the head , around the insert and back to the radiator.
This alone is an instant 1 to 1.5 Hp in 50.

Water flow and cooling in general is a very much ignored source of " free " power gains.
Having water flowing around the entire length of the Exhaust duct , where the plugging charge is retained , is super simple , but never done properly as far as I have seen.
These slots in the Exhaust exit surface ( done by hand many years ago in the pit with a battery drill and file ) cools the back of the spigot as well , and reduces the background deto level by around 20% - allowing alot leaner egt level at full power as a result.
This is much easier now with a small 75% exit area and a 6 axis CNC .

Wob, if you include the crankcase flow, how would you do it?

[Muhr]

The best scenario is to have all the cold water enter the cylinder over the boost port , then run around the bore over the tops of all the transfers - cooling these first.
Then a portion of the return should be directed to a pair of small exit holes on each side under the Exhaust , the remining flow then exits up into the Exhaust side of the head , around the insert and back to the radiator.
This alone is an instant 1 to 1.5 Hp in 50.


Do not know if I really understand. Is there something like this you are thinking of?

[TZ350]

Dyno time ...... vrooom vrooom WOT maxed out in 6th ... back wheel stopped turning around. So much for my last new cylinder ....... :Oops:


Geez, what kind of piston do you run. I never, like never seized an RG on std or KX piston.

Took the cylinder off. It seems that I let the Kneed-It filler in the inlet get to close to the piston.

The piston rubbing on the epoxy must have melted it and the epoxy mess ripped things up. I guess the epoxy did not have good lubricating property's.

351117 351118 351119

Next time I wont try and bring the filler in the inlet port up flush with the cylinder. Cylinder looks salvageable, but not sure about the piston.

[wobbly]

Sorry I didnt word my fist description correctly.
If the water is fed initially into the crankcase ( from the front in the Aprilia or the middle as in the TM ) then the main flow from there should be directly up into the cylinder
with a pair of large holes each side of the boost port ( NOT underneath the hot Exhaust duct ) . Another pair of smaller holes should also feed up under the Exhaust port , thus aiding flow around this area separately.
The only exit flow from the cylinder is up into the head directly over the Exhaust port. Thus keeping the water heated up by the Exhaust duct flowing away from the transfers.

This is possible for example in the TM , if the water in the cavity between the case and the gearbox is then also fed forward over the top of the mains ( thus cooling the transfer entry area ) and up
into the cylinder each side of the boost port.

This idea has been applied to old designs , like TZ250/350/750 , where the original flow was completely wrong - but this needs some form of separation plate or gasket between the head and cylinder.
Again , in this case all the flow enters the cylinder thru a new spigot welded in opposite the Exhausts , and all the cold water flows forward across the transfer tops , then exits into the head thru a pair of holes
each side above the Exhausts.

The test was done on a TM by extending the existing water feed hole around to above the boost port. A real 1 Hp free lunch , but not shown in the homologation papers , so probably illegal.
Thus I did the almost as good change , and forced all the cold water away from the Exhaust duct with a hidden manifold inside the cylinder - legal.