ESE's works engine tuner

[TZ350]

Roost

https://www.facebook.com/pg/Roost-exhaust-systems-264059023656148/photos/?tab=album&album_id=1008873025841407 (https://www.facebook.com/pg/Roost-exhaust-systems-264059023656148/photos/?tab=album&album_id=1008873025841407)
(https://www.facebook.com/media/set/?set=ms.c.eJw1yNENgFAMAsCNDLRQ6v6LGaPvPo~%3BmWFqsE DsX~%3B4gRFU9M~_w3MfULLCKn~_ws1aYVJ~_ANPsEQI~-.bps.a.1516544791740892.1073741846.264059023656148&type=1)
Ok, I found their face book page. Interesting stuff.

https://www.facebook.com/media/set/?set=ms.c.eJw1yNENgFAMAsCNDLRQ6v6LGaPvPo~%3BmWFqsE DsX~%3B4gRFU9M~_w3MfULLCKn~_ws1aYVJ~_ANPsEQI~-.bps.a.1516544791740892.1073741846.264059023656148&type=1 (https://www.facebook.com/media/set/?set=ms.c.eJw1yNENgFAMAsCNDLRQ6v6LGaPvPo~%3BmWFqsE DsX~%3B4gRFU9M~_w3MfULLCKn~_ws1aYVJ~_ANPsEQI~-.bps.a.1516544791740892.1073741846.264059023656148&type=1)

Speed Factory

https://www.facebook.com/Speed.Factory.Shop?fref=nf

https://www.speed-factory.net/tuningkit-roost-havoc-98cc-fuer-piaggio-lc-4101

Kits, cylinders and pipes.

https://www.speed-factory.net/schnellauswahl/

The F4 Bucket class rules allow 100cc 2T water cooled (with 110cc max re bore allowance) or 70cc 2T with Turbo or Supercharging.

336157

A 70cc 24-28hp Roost cylinder fitted to my Suzuki GP100 motor with a special short stroke crank should leave lots of supercharged volume in the crankcase and with a turbo blowing through the original air cleaner inlet on the back of the motor we could have something very interesting. I am going to consult my credit card to see if the project is possible. Team ESE already has a suitable turbo. Could this be the makings of the first 40hp Bucket???

I was once accused of ruining Buckets by making it to hard for others to compete, because essentially, I studied two stroke tuning and did the work others wouldn't. But it turns out, all you need is a good credit card.

[timg]

I was once accused of ruining Buckets by making it to hard for others to compete, because essentially, I studied two stroke tuning and did the work others wouldn't. But it turns out, all you need is a good credit card. LOL :laugh: now you'll be accused of being a chequebook racer like me :bleh:

[TZ350]

With all the stuff we make, you and I and a few others couldn't be further from chequebook racing, if we tried...... :D

[SwePatrick]

Minarelli, Aprilia AM6 and Scooter aftermarket cylinders are not very common here in New Zealand so I don't know much about them.

I would love to know more about the Roost Havoc cylinder, its exhaust and transfer timings and the pipe that you used.

If I knew what to look for I guess it would be pretty easy to buy a cylinder or two and pipe over the net. I would love to try one on my rotary valve engine.

And if anyone knew of a current performance 50cc cylinder kit and pipe I would love to hear about those too.


We raised the cylinder a little bit to get a little bit more timing, i have to ask what timings it is std.

We were hunting for 38-38.5hp(e85), and will pick up this ball again soon.
It actually gave us more power with 32mm carb than a 34mm, 36.2hp is our current best yet.

If wanting to buy a roost cylinder, make sure you are patient enough to wait.
It´s a small company and he doesnt massproduce.
We waited ~8 months

He also makes a 100cc version with external studs, theese cylinders has been dynoed above 40hp(ported)

As we speak, tomorrow an another friend coming to visit me.
I´m helping him build a piaggio twin roost 100cc. (we are waiting for 2nd cylinder)
200cc in total.
It will be a beast =)

336160336161

[TZ350]

.
Thanks, I saw the external stud version and wondered what they may be like.

Please keep posting about your projects progress.

[koba]

Any recommendations for a decent degree wheel/protractor?
I thought I'd bought the 'last a lifetime' type and shelled out too much money for one that has had half of the graduations flake off.

Laser etched numbers would appear to be the way to go but everything I see it way pricey given what it costs to produce that kind of stuff today.
Might be easier to commission or make a batch.

Thoughts?

[richban]

Any recommendations for a decent degree wheel/protractor?
I thought I'd bought the 'last a lifetime' type and shelled out too much money for one that has had half of the graduations flake off.

Laser etched numbers would appear to be the way to go but everything I see it way pricey given what it costs to produce that kind of stuff today.
Might be easier to commission or make a batch.

Thoughts?


Nice and sturdy. Also its recycling.

[wobbly]

Here is what I use - simple to mount with a 6mm shaft.
Cheap as chips and accurate to 1/10*.
Easy angle measure from TDC or duration with a port stop.
Would never go back to a disc.

https://www.machine-dro.co.uk/rotary-angle-encoder-and-remote-display-with-a-6mm-diameter-shaft.html

And a coupling to mount it.

https://www.ebay.com/itm/5-6-6-35-8mm-Flexible-Shaft-Coupling-Rigid-For-CNC-Motor-Coupler-Connector/162264693060?hash=item25c7bab944:m:muZHNBvhflmXpb7 npROfsOA

[TZ350]

.
This is what Team ESE uses ....

336167 336168

Plastic protractor glued onto a metal disk. Cheap as chips from any stationary store.


Here is what I use - Would never go back to a disc.

https://www.machine-dro.co.uk/rotary-angle-encoder-and-remote-display-with-a-6mm-diameter-shaft.html

And a coupling to mount it.

https://www.ebay.com/itm/5-6-6-35-8mm-Flexible-Shaft-Coupling-Rigid-For-CNC-Motor-Coupler-Connector/162264693060?hash=item25c7bab944:m:muZHNBvhflmXpb7 npROfsOA

I love the look of that encoder..... :niceone:

[TZ350]

.
Another good reason to water cool the outside of the transfer ducts.

336169 336170

Interesting how far down the transfer ducts the staining stretches from combustion gases marking the transfer walls on this cylinder from a Honda NSR250. You can see why a cylinder overheats when there is insufficient blowdown time area for the reves being pulled.

I remember Speedpro talking about being able to look down the carburetor on one of his bikes being run up on the dyno and see fire dancing in the crankcase.

[TZ350]

Aircooled Suzuki GP125 cylinder.

336174 336178

Porting my aircooled GP125 cylinder.

336177 336176

The big gains were in opening up the rear transfer ports and setting the ex to open at 80 atdc and 72% width.

336175

30rwhp

[TZ350]

Standard Honda NSR250 cylinder.....

336172 336171

I had always been impressed by all this porting loverlyness and expecting great things I replaced the GP's air cooled cylinder with one of these NSR 250 cylinders. The cylinder was arranged so the Ex port opens 80 atdc. The same as the Suzuki GP air cooled cylinder.

336179

Touching 30rwhp.

So all that factory port loverlyness was no better than my home grown porting efforts on the Suzuki GP125 cylinder. Not what I was expecting.

[husaberg]

Standard Honda NSR250 cylinder.....
A solid 29rwhp.

So all that factory port loverlyness was no better than my home grown porting efforts on the Suzuki GP125 cylinder. Not what I was expecting.

Keep the dyno running and see just how much of those 30HP are still there a minute or two later with the Air cooled cylinder vs the water cooled STD NSR cylinder.
Also bear in mind that with a few less cc on the liquid cooled model you could have run an open carb size as well.
Were the RC valves operational on the Liquid cooled dyno run.

[TZ350]

Keep the dyno running and see just how much of those 30HP are still there a minute or two later with the Air cooled cylinder

336180

I cant remember what the experiment was but the power held up Ok on the dyno for several runs. But you are right, the ponies soon lost enthusiasm after a few laps on the track.


Also bear in mind that with a few less cc on the liquid cooled model you could have run an open carb size as well.

Like factory porting loverlyness I am not sure a bigger carb would be any improvement. But in a way I think you could be right, there could be more power if I destroked to 100 cc because the shorter stroke would naturally increase the blow down time area of the standard NSR cylinder.


Were the RC valves operational on the Liquid cooled dyno run.

Yes, and carefully adjusted on the dyno too.

I was surprised they were not more effective at plumping up the curve. But the std ones have large gaps at the sides. I expect they will be better when I get around to welding and reshaping a pair to fit better.

[husaberg]

Yes, and carefully adjusted on the dyno. I was surprised they were not more effective but the std ones have large gaps at the sides. I expect they will be better when I get around to welding and reshaping a pair to fit better.

The factory race RC valves have the pivot mounted further away from the bore thus during their arc the sealing edge follows the bore more closely.

[TZ350]

The factory race RC valves have the pivot mounted further away from the bore thus during their arc the sealing edge follows the bore more closely.

Yes, this is a definite problem with the standard valves. Especially if you level off the top edge of the exhaust port.

336183

My next trick is to flatten and radius the RC valve and fit it to a cylinder with the top of the exhaust port set at 78 atdc and use the flat valve to present a straight horizontal timing edge to the cylinder at 80 atdc. That way I get the benefit of a flattened port roof, closely sealing RV valve and the improved flow coefficient of a radiused leading edge on the valve. Basically it should then behave like the Aprilia radiused exhaust port. All without doing any porting work on the cylinder itself. So reliable and cheap.

336182

[SwePatrick]

Any recommendations for a decent degree wheel/protractor?
I thought I'd bought the 'last a lifetime' type and shelled out too much money for one that has had half of the graduations flake off.

Laser etched numbers would appear to be the way to go but everything I see it way pricey given what it costs to produce that kind of stuff today.
Might be easier to commission or make a batch.

Thoughts?

I use a simple digital caliper and this:
http://www.csgnetwork.com/timingportdurationcalc.html

[husaberg]

All without doing any porting work on the cylinder itself. So reliable and cheap.


Rob did you use the Same EX Honda Rs125 pipe for both test as I doubt it would be the ultimate design for the short stoke engine either?

[philou]

Here is what I use - simple to mount with a 6mm shaft.
Cheap as chips and accurate to 1/10*.
Easy angle measure from TDC or duration with a port stop.
Would never go back to a disc.

https://www.machine-dro.co.uk/rotary-angle-encoder-and-remote-display-with-a-6mm-diameter-shaft.html

And a coupling to mount it.

https://www.ebay.com/itm/5-6-6-35-8mm-Flexible-Shaft-Coupling-Rigid-For-CNC-Motor-Coupler-Connector/162264693060?hash=item25c7bab944:m:muZHNBvhflmXpb7 npROfsOA

works very well.

Sells ready to use. Easy to manufacture support ;)

http://srp-racingshop.com/shop/media/images/info/DegreeTec.jpg

http://srp-racingshop.com/shop/en/equipment/degree-tec-digital-degree-wheel

[TZ350]

Rob did you use the Same EX Honda Rs125 pipe for both test as I doubt it would be the ultimate design for the short stoke engine either?

Yes, and you may be right but it has proved to be a very effective pipe. Very tolerant of my different engines.

My motors started at 16hp at 8,000 rpm and now 30 at 12,250 rpm.

Its not too surprising the RS pipe has worked well on all of them. Because its a good shape and a suitable length for lower rpm, power and exhaust temperatures. A length that is much the same as required for higher rpm, power and consequently higher exhaust temperatures. So basically the RS pipe has been the right length pipe for all my engines as they have developed increased power and rpm.

It works like this:-

A) Lower rpm = longer pipe.
B) Lower exhaust gas temp = shorter pipe.
C) Higher rpm = shorter pipe.
D) Higher exhaust gas temp = longer pipe.

A+B = C+D

I have tried to simulate better designs in EngMod but could not develop anything that was superior.

[husaberg]

Yes, it has proved to be a very effective pipe. Very tolerant of my different engines.

My motors started at 16hp at 8,000 rpm and now 30 at 12,250 rpm.

Its not too surprising the RS pipe has worked well on all of them. Because its a good shape and a suitable length for lower rpm, power and exhaust temperature. A length that is much the same for higher rpm, power and consequently higher exhaust temperatures. So basically the RS pipe has been the right length pipe for all my engines as I have developed them for increased power and rpm.

I have tried to simulate better designs in EngMod but could not develop anything that was superior.
Did you try the Honda kit pipe as used by KTM as well? It could do with being a little shorter though given yours should be aiming a bit higher in the revs.
I will post pic as soon as I find it.
I believe this is the Last honda pipe as used by KTM as well.
336208


This is the production 95 RS125 honda pipe
336207

[TZ350]

.
Thanks, great info.

[Martin1981]

.
Another good reason to water cool the outside of the transfer ducts.

336169 336170

Interesting how far down the transfer ducts the staining stretches from combustion gases marking the transfer walls on this cylinder from a Honda NSR250. You can see why a cylinder overheats when there is insufficient blowdown time area for the reves being pulled.

I remember Speedpro talking about being able to look down the carburetor on one of his bikes being run up on the dyno and see fire dancing in the crankcase.

i once rebuilt a kx 500 engine...not only the transfer ports were black. the whole crankcase, the crankbearings, they looked terrible. and even the inlet was black!

for me this indicates the bike was either ridden the hell out of it and revved high the most time, the blowdown becomes insufficient at a certian engine speed as Jan, Wobbly and Frits explained .

Or it was ridden with respect :) and part throttle, wich makes the transferport entering exhaust gases issue worse.

i think this is more a blowdown than a transfer cooling issue. though cooling the transfer walls might help.

[TZ350]

.
Yes I think you are right, a blow down issue. I hadn't thought of part throttle blow down issues but that could easily be it.

[SwePatrick]

As said earlier.
A friend came to visit me.

I´m helping him with his twin Roost 100 (200cc)
Today we ported the block(not done yet) and made room for the Banshee V-force 4 reeds.
The reeds will be spaced out roughly 14-15mm

336210336211336212336213336214

[wobbly]

The Honda customer RS125 pipe has a Lt of around 824 ( including the front of the nozzle to point S )
This was matched to an EO of 82.5*.
That combination gave a good power spread and rpm capability near 13,000 in the overev.
Where as the so called "factory " specs " have an Lt closer to 800 ( same as an Aprilia ) and was developed to work with a EO at 80*.
That setup used PWM powerjets, and a completely different ignition curve suited to reving closer to 14,000 in the overev.
The A kit spec spec as used by KTM is nowhere near suited to the older customer Honda cylinder without all the other bits needed to all work together.
Here is a rear wheel dyno sheet showing a well tuned customer RS125, an A kitted engine and an A kit with powervalve.
Completely different tuning scenarios, so just bunging that pipe on an older engine simply wont work.
Using Engmod now it would be very easy to produce a pipe with way better power than either design, as long as the correct cylinder and ignition specs were followed.

[TZ350]

Completely different tuning scenarios, so just bunging that pipe on an older engine simply wont work.

It is certainly what has worked the best for me so far.


Using Engmod now it would be very easy to produce a pipe with way better power than either design, as long as the correct cylinder and ignition specs were followed.

Hi Wob, I have given it a serious go but haven't been able to do it myself.

But if it would be easy enough for you, I would be happy to post my engine specs in EngMod format if you were willing to give developing a better pipe go.

We could post the design reasoning behind the engine and pipe and the dyno results here. It would be a very interesting and educational example of using the EngMod2T software.

[husaberg]

The Honda customer RS125 pipe has a Lt of around 824 ( including the front of the nozzle to point S )
This was matched to an EO of 82.5*.
That combination gave a good power spread and rpm capability near 13,000 in the overev.
Where as the so called "factory " specs " have an Lt closer to 800 ( same as an Aprilia ) and was developed to work with a EO at 80*.
That setup used PWM powerjets, and a completely different ignition curve suited to reving closer to 14,000 in the overev.
The A kit spec spec as used by KTM is nowhere near suited to the older customer Honda cylinder without all the other bits needed to all work together.
Here is a rear wheel dyno sheet showing a well tuned customer RS125, an A kitted engine and an A kit with powervalve.
Completely different tuning scenarios, so just bunging that pipe on an older engine simply wont work.
Using Engmod now it would be very easy to produce a pipe with way better power than either design, as long as the correct cylinder and ignition specs were followed.
Wob think you have misunderstood the point I was trying to make, wasn't suggesting that blindly adding the works pipe was the answer, I was suggesting that I didn't believe the use of the Std pipe and rev perimeters with now de-stroked engine was the best combination. I simply suggested that Rob might be better served to follow the path of development that Honda had with the later models.

[TZ350]

I´m helping him with his twin Roost 100 (200cc)
Today we ported the block(not done yet) and made room for the Banshee V-force 4 reeds.

336211

Great, I love your work. Impressive engine building effort..... :not:

[wobbly]

I was saying that putting the short A kit pipe on an older RS125 engine simply wont work - plenty have tried, and failed.
Sure TeeZee, you post the pack, and i will do a pipe,with some insights into the process.

[TZ350]

Sure TeeZee, you post the pack, and i will do a pipe,with some insights into the process.

Great, I will carefully work through modeling my engine setup and post the pack.

[TZ350]

336216 my preliminary EngMod simulation, (crank hp). 336217 real life dyno run of the engine being modeled, (rw hp) .

The EngMod simulation is starting to look like the real thing. I will refine the model a bit more then Wob can work his magic and hopefully let us in on a trick or two.

[flyonly]

Yes, these ones:

https://www.treatland.tv/v/vspfiles/photos/vee-rubber-V266-65-fslash-75-17in-2.jpg

What size rim do you run them on? 1.4 or smaller?


Sent from my iPhone using Tapatalk

[SwePatrick]

I run the rear tire on a 1.6" rim
And the front tire on a 1.2" rim

=)

[dutchpower]

I was saying that putting the short A kit pipe on an older RS125 engine simply wont work - plenty have tried, and failed.
Sure TeeZee, you post the pack, and i will do a pipe,with some insights into the process.

Why Wobb everytime I make pipe in Engmod the pipe on de dyno is on the left !!!!

[koba]

Thanks for the tips on degree wheel etc.

[wobbly]

Simple Dutchpower - in the Temp page you have not simulated the pipe wall temp correctly.
The new rpm dependent inputs now also have the opportunity to enter the real ,as measured, surface temp data from the header,the mid, and in front of the stinger.
As the bmep reaches the outer limits, as in say a KZ2 engine, at 50Hp from a 125, the smallest changes in this type of data, make big effects on the result.
That is Bullshit in = Bullshit out.
For many tuned engines I have found that a global average temp of 325*C at the bottom of the powerband and 425*C at peak is a good start point,when the tuning gives low to mid 600*C inside the header.
The other issue is the correct modelling of say a step in the header flange.Just putting in the dimensions to correctly show the position of a step is not the same as defining
a step properly in the opening page of the pipe inputs.
The code has a very difficult time handling steps ,and not defining them correctly creates havoc in the results.

[dutchpower]

Thanks Wobbly

[chrisc]

I'm racing 50s here in Europe, it's pretty rad. I also got to meet Frits finally after reading so much of his advice online.

Check out what I'm up to here: www.grandprixmachine.com (http://www.grandprixmachine.com/)

https://static1.squarespace.com/static/54f417b0e4b0ba5e061bdebd/t/5ad31ef188251b90ed415739/1523785515430/IMG_0763.jpg?format=800w

[F5 Dave]

Chris how do you get in these situations? I would love to have been in those pits with all those 50s.
I guess they make our efforts look a little shaky.

[Bert]

I'm racing 50s here in Europe, it's pretty rad. I also got to meet Frits finally after reading so much of his advice online.

Check out what I'm up to here: www.grandprixmachine.com (http://www.grandprixmachine.com/)

https://static1.squarespace.com/static/54f417b0e4b0ba5e061bdebd/t/5ad31ef188251b90ed415739/1523785515430/IMG_0763.jpg?format=800w

Choice Chris.
Loving the pictures and the updates.

[TZ350]

I'm racing 50s here in Europe, Check out what I'm up to here: www.grandprixmachine.com (http://www.grandprixmachine.com/)

Really Really Great write up Chris, and super great to see Frits there with you.

[sb07]

works very well.

Sells ready to use. Easy to manufacture support ;)

http://srp-racingshop.com/shop/media/images/info/DegreeTec.jpg

http://srp-racingshop.com/shop/en/equipment/degree-tec-digital-degree-wheel

if you do not want to throw money ... :msn-wink:

https://www.ebay.com/itm/Remote-Display-Angle-Sensor-Encoder-with-Shaft-for-Rotary-Table-Dividing-Head/252761006720?epid=1305348143&hash=item3ad9bae280:g:pV4AAOSwlAZadJ1C

[philou]

That's where I bought it. And copy the idea of support kart shop

[mattology]

what tires are you using chris ?

[wax]

Im wondering if anyone has played with a reverse taper inlet on a two stroke intake.
Instead of having the taper get larger or stay parallel im talking about a 11 degree angle which would keep increase the inlet air speed.
11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block
Thoughts ?

[F5 Dave]

Where does this reed exit out to? I think that's probably your answer.

[EssexNick]

Inlet taper.
My initial thought was a really short inlet is required, so there may not be sufficient length to see any noticeable gains. It might help a lower reving motor. But i am just guessing here.

[husaberg]

Im wondering if anyone has played with a reverse taper inlet on a two stroke intake.
Instead of having the taper get larger or stay parallel im talking about a 11 degree angle which would keep increase the inlet air speed.
11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block
Thoughts ?

Reed valves are already an venturi.......
http://1.bp.blogspot.com/-LFtpWtfk_J0/VVcNRz024fI/AAAAAAAACqE/OFi6kADEwjw/s1600/valves-a12i2.jpg (http://www.google.co.nz/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwiY3rm_gMHaAhXGlpQKHYgCAocQjRx6BAgAEAU&url=http%3A%2F%2Fmechlover.blogspot.com%2F2015%2F0 5%2Freed-valve-induction-system-explained.html&psig=AOvVaw2NOjqXjD6luwORBow3B5zL&ust=1524043984438796)

[TZ350]

I'm wondering if anyone has played with a reverse taper inlet on a two stroke intake.Thoughts ?

Yes. It was something I played with briefly on my rotary valve engine but it did not show any benefits and made less power. Put it down to the fact a 2T is not a 4T and 4T ideas don't always translate to 2T's. Maybe I got something wrong, but anyway I wasn't impressed. Would love to hear if someone has had success with the idea.


Im talking about a 11 degree angle which would keep increase the inlet air speed. 11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block.

Higher pressure? or greater kinetic energy? I wanted kinetic energy (speed * mass) to ram and over fill the crankcase. Pressure recovery increases as you slow the moving air column down.

[SwePatrick]

Im wondering if anyone has played with a reverse taper inlet on a two stroke intake.
Instead of having the taper get larger or stay parallel im talking about a 11 degree angle which would keep increase the inlet air speed.
11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block
Thoughts ?

I have good experiances with having the carb taper drilled.
From big to smaller in the direction of flow.

First the velocity stack then inlet 46.5mm and outlet 43.5mm.
This is roughly 1.5degree on the radius.

This has proven for me to add torque and keeping the top end as a 45mm carb has.

[chrisc]

Chris how do you get in these situations? I would love to have been in those pits with all those 50s.
I guess they make our efforts look a little shaky.

Pure enthusiasm Dave! Plus I seem to have made quite of lot of friends recently when flew to the other side of the world to race 50s! The ~$3000 in insurance isn't cheap but the experiences and memories will always be worth it.

And yeah, our machines are uhhhh, quite primitive :rolleyes: MOST of these 50s are more developed and have better gear on them than any 125GP bike or 250GP bike in New Zealand. Which makes sense given our distance from European professional teams and racing. I've learnt a lot already. I truly think F5 should adopt Freetech rules. It's one hell of a class! I'd like to ride a Freetech level 50 against the 250 production bikes in New Zealand. I think I could beat most of them with this level of tech.


Choice Chris.
Loving the pictures and the updates.


Really Really Great write up Chris, and super great to see Frits there with you.

Thanks Brent, Rob! Glad you're enjoying them, I'm enjoying sharing the experience!


what tires are you using chris ?

Dunlop Moto3 slicks on factory NX4 wheels. Most of the field have PVM, Marchesini, Marvic or carbon wheels hahaha it's nuts! I have a new medium compound on the front and a new soft on the rear. Thankfully they're new and they were cheap but I'll see how this medium works for my light weight and smooth (read: not heavy on the brakes) riding style.

[wobbly]

I have tried increasing the velocity ( read decreasing the inlet area ) on several VF3 reed blocks.
By adding a vertical splitter ( they all have a horizontal one ) to the stuffer insert every one made better mid power with no loss in peak or overev.

And in the KZ2 kart engines that are limited to a 30mm carb, I spent hours CAD designing up a stuffer that created a venturi at the point where the cage ports begin.
This is 3mm smaller than the carb in area,and the smaller area is kept right up to the cage tip where the reed petals end ( the area measured with the petal closed ).
The 3D printed stuffer costs $15usd to have done in Taiwan, and is the cheapest, quickest 0.5 to 1.5 Hp I have ever seen.
I believe that if we were allowed to press in a tapered insert from the slide,to the end of the carb spigot, this reduced stuffer area would work even better.

But the reverse idea works really well on Lectron HV carbs.They have a venturi directly behind the slide that is 4mm smaller than the bellmouth entrance area.
This R2 venturi then tapers back out to the nominal carb size at the spigot end.
On the flow bench a 40mm Lectron will flow over 12% better at WOT than a 38mm PWM but has 18% more velocity under the slide at 1/2 throttle.
Thus way better throttle response as well as more top end power.
The very reason that many people ( EMOT )use huge 30mm Lectrons on the 50cc racers in Europe - note to Chris.

[lodgernz]

I truly think F5 should adopt Freetech rules. It's one hell of a class! I'd like to ride a Freetech level 50 against the 250 production bikes in New Zealand. I think I could beat most of them with this level of tech.


I just read the Freetech 50 rules online. What a joy of simplicity and clarity! Well done Frits. Then I look at the MNZ rules and cringe.

If we were to introduce those same rules here, I suspect it would force everyone who wanted to compete to move to nicasil-bore cylinders, since oversize cylinders are not allowed. Older cast iron cylinders and those with steel liners would be eliminated since most of them are already at least one oversize. Given the investment some of us have in this old stuff (pretty much mandated by our own bucket rules), a Freetech 50 class might be less attractive initially.
Obviously, these old engines would no longer be competitive in the face of MX 50 engines and Euro race engines, so would fall away anyway, but it would be nice to have an upgrade window. Possibly we could change the rules slightly to allow minimal overbore. Or we could run two classes of 50, Freetech and Vintage, but this is probably not feasible given the small number of people who race F5 now.

It's a fantastic class though, no argument.

[speedboy]

"On the flow bench a 40mm Lectron will flow over 12% better at WOT than a 38mm PWM but has 18% more velocity under the slide at 1/2 throttle."

40^2/38^2= 1.108
Lectron is 1 percent better (measurement error may be greater)

Half throttle is it may not be a half surface, but if so, then there is a little better. :)

[wobbly]

1.108 is 10% more area, and the lectron flows slightly better than 10% more air ( same pressure drop of 28" ).
At 1/2 throttle the area is also 10% different, but the lectron has a huge advantage in velocity across the fuel nozzle and thus the signal strength.
This allows a bigger carb size to be used without loosing throttle response - the old issue of " staggers " when opening a carb that is too big.
Why do you think Lectron call these things HV carbs.

[speedboy]

1.108 is 10% more area, and the lectron flows slightly better than 10% more air ( same pressure drop of 28" ).
At 1/2 throttle the area is also 10% different, but the lectron has a huge advantage in velocity across the fuel nozzle and thus the signal strength.
This allows a bigger carb size to be used without loosing throttle response - the old issue of " staggers " when opening a carb that is too big.
Why do you think Lectron call these things HV carbs.


At half throttle is ok, when lectron and pwm venturi shape is same. But shape is another, then half throttle area is different, incorrect measurement. I think lectron and keihin throttle body is not same.

336255

[wobbly]

The difference is that the 40mm Lectron has a 36mm venturi behind the slide.
Thus at 1/2 throttle it acts like a 36mm carb, at WOT it acts like a 40mm carb.
The area change is even greater in a 30mm body as they use in 50cc racing.
At 1/2 throttle it has a 26mm venturi,giving 33% more velocity /fuel signal than a parallel bored 30mm carb.

[Nath88]

Found something interesting while checking out the Athena GET aftermarket ECU for the KTM TPI system...
http://www.getdata.it/data/documentation/sito/Gestione_motore/ECULMB48M/Download/Documentazione/GD_MIP_0039_AA.pdf

336256

The 'injectors support kit' moves the injectors to a spacer plate between the reed block and crankcase, and plugs the existing transfer port bungs.
I also downloaded the map pack and included was a map for 'indirect injection'. Couldn't find any other info on it anywhere. Must be some performance improvement, is a lot of effort to go to to make something worse.

Update on my bike, I had the cylinder 'bored' by the other shop in Australia that does Nikasil. Got it back to adjust the ports before plating, the bore is offset 0.35mm toward the front at the top and 0.30mm toward the back at the bottom. Turns out he used a hone for the whole 2.1mm!! The guy says it 'should be ok', I'm really not impressed, not sure what to do with it from here. The difference in squish front to back would be 0.3mm so that limits what I can do there, if it was bored out to 72mm it would clean up, but I don't want to go there.

[Grumph]

Pure enthusiasm Dave! Plus I seem to have made quite of lot of friends recently when flew to the other side of the world to race 50s! The ~$3000 in insurance isn't cheap but the experiences and memories will always be worth it.

And yeah, our machines are uhhhh, quite primitive :rolleyes: MOST of these 50s are more developed and have better gear on them than any 125GP bike or 250GP bike in New Zealand. Which makes sense given our distance from European professional teams and racing. I've learnt a lot already. I truly think F5 should adopt Freetech rules. It's one hell of a class! I'd like to ride a Freetech level 50 against the 250 production bikes in New Zealand. I think I could beat most of them with this level of tech.


You most probably could - on Levels anyway, (cough)...

[F5 Dave]

I just read the Freetech 50 rules online. What a joy of simplicity and clarity! Well done Frits. Then I look at the MNZ rules and cringe.

If we were to introduce those same rules here, I suspect it would force everyone who wanted to compete to move to nicasil-bore cylinders, since oversize cylinders are not allowed. Older cast iron cylinders and those with steel liners would be eliminated since most of them are already at least one oversize. Given the investment some of us have in this old stuff (pretty much mandated by our own bucket rules), a Freetech 50 class might be less attractive initially.
Obviously, these old engines would no longer be competitive in the face of MX 50 engines and Euro race engines, so would fall away anyway, but it would be nice to have an upgrade window. Possibly we could change the rules slightly to allow minimal overbore. Or we could run two classes of 50, Freetech and Vintage, but this is probably not feasible given the small number of people who race F5 now.

It's a fantastic class though, no argument.

Its really a cruel twist of history that 50 and 100cc bikes were popular in the 70s and 80s. But for whatever reason we didn't get the kids all on Derbis and AM6 engined bikes and they all bought RGV250s instead due to our lax licencing laws of the time and perhaps disposable income. Or maybe jap import cars and the promise of carnal wagon action. Fools!

[jonny quest]

Found something interesting while checking out the Athena GET aftermarket ECU for the KTM TPI system...
http://www.getdata.it/data/documentation/sito/Gestione_motore/ECULMB48M/Download/Documentazione/GD_MIP_0039_AA.pdf

336256

The 'injectors support kit' moves the injectors to a spacer plate between the reed block and crankcase, and plugs the existing transfer port bungs.
I also downloaded the map pack and included was a map for 'indirect injection'. Couldn't find any other info on it anywhere. Must be some performance improvement, is a lot of effort to go to to make something worse.

Update on my bike, I had the cylinder 'bored' by the other shop in Australia that does Nikasil. Got it back to adjust the ports before plating, the bore is offset 0.35mm toward the front at the top and 0.30mm toward the back at the bottom. Turns out he used a hone for the whole 2.1mm!! The guy says it 'should be ok', I'm really not impressed, not sure what to do with it from here. The difference in squish front to back would be 0.3mm so that limits what I can do there, if it was bored out to 72mm it would clean up, but I don't want to go there.

How can you hone aluminum that much? YZ250 cyl, right? I'd make them biy me a new cylinder. That could cause crank and piston failures. Especially if it's not square side to side.

Interesting on GET. Are you going to buy that system and retrofit to YZ?

[Michael Moore]

I may have missed seeing it discussed, but would there be a benefit to having two separate cooling circuits on a 2T? That would be a high temp circuit that does the exhaust port/manifold/head and a low temp that does the crankcase/transfers. I'd think the case/transfers would tend to run cooler anyway, so why use the hotter water that has gone to the hot spots of the top end on them?

Electric pumps are easy to get and there'd be no need for a temperature control on the case circuit, just circulate the water non-stop through the heat exchanger. A controlled pump (like the Davies Craig) could circulate coolant on the hot circuit and control the temperature to whatever is desired.

I suppose there'd need to be enough power increase from lower case temperatures to offset the weight of an extra pump/heat exchanger.

Does that make any sense?

[koenich]

Pure enthusiasm Dave!
Massive effort, love it! And by the end of the season you hopefully have a Star Alliance Gold card :2thumbsup

I'm thinking about doing the Hockenheim round, as it is just around the corner from my hometown. Need some fairings though :laugh:

336257

[mattology]

that athena get seems like a major step backwards

[husaberg]

I may have missed seeing it discussed, but would there be a benefit to having two separate cooling circuits on a 2T? That would be a high temp circuit that does the exhaust port/manifold/head and a low temp that does the crankcase/transfers. I'd think the case/transfers would tend to run cooler anyway, so why use the hotter water that has gone to the hot spots of the top end on them?

Electric pumps are easy to get and there'd be no need for a temperature control on the case circuit, just circulate the water non-stop through the heat exchanger. A controlled pump (like the Davies Craig) could circulate coolant on the hot circuit and control the temperature to whatever is desired.

I suppose there'd need to be enough power increase from lower case temperatures to offset the weight of an extra pump/heat exchanger.

Does that make any sense?
I think I do Michael, use the radiator on the Crankcase side only with a heat exchanger for the top end. you would need to use a large surface area to get the appropriate area for cooling though but a small marine oil cooler would likely work.
336272

[Michael Moore]

I think I do Michael, use the radiator on the Crankcase side only with a heat exchanger for the top end. you would need to use a large surface area to get the appropriate area for cooling though but a small marine oil cooler would likely work.

We may have a small terminology misunderstanding since I was using "heat exchanger" to refer to a "radiator" (per Carroll Smith's "Prepare to Win" definition that they are water/air heat exchangers) but I hadn't considered using a liquid/liquid heat exchanger since I've never had occasion to use one in the past. I was envisioning a "radiator" for each circuit.

So would I be correct that you do think there would be some advantage to having two (a high temp and a low temp) separate cooling circuits so the low temp circuit can more easily stay "low" by not having to deal with the high temp coolant?

cheers,
Michael

[wobbly]

So here are the first results of going over Robs GP - NSR110 engine with the intent of fixing any glaring issues,then doing a trick pipe design.
By small alterations to the pipe temp file, and realizing that a RV engine at WOT,way off the pipe will carburate like shit due to intake wave interaction,then
the sim Vs the dyno is a pretty good match.
Then the first two things to look at are the Mach numbers in the Ex duct exit, and the stinger nozzle.
To do this you must first run the sim with the Ex transducer at the header start length ( and name that file ),then rerun it ( and rename the file ) with the transducer length
within the nozzle.
From these results you can see that both are miles off the 0.8 Mach rule of thumb.
Then we look at TuBMax,and this shows that the combination of bmep,ignition lead and stinger size is way down overall, but more so in the midrange where it never gets even
close to the 1000* deto limiting guideline.
More to come as I work thru any further shortcomings.

[TZ350]

.
Very interesting, great info, loving learning more about how to use EngMod professionaly, thanks Wob.

[wobbly]

So sticking with the original pipe initially,here is the result of welding or inserting the Ex duct and reducing it to 34mm outlet size.
Along with this making a new spigot to match the smaller cylinder exit to the stock pipe header.
Check the rise in the resultant exit Mach.
We are already seeing that the powervalve ramp is now becoming mismatched,with a big dip in the midrange.
Also the taper in the spigot is already getting very steep, as the RS125 pipe header size ( 41mm ) is way too big for an engine only making 30 Hp as the effective area
of the port ( even set a 200* duration ) is only 35.8mm diameter.

[Nath88]

How can you hone aluminum that much? YZ250 cyl, right? I'd make them biy me a new cylinder. That could cause crank and piston failures. Especially if it's not square side to side.

Interesting on GET. Are you going to buy that system and retrofit to YZ?

Yeah YZ250 cylinder, its definitely a lot of material to remove. Doesn't appear to be squif side to side, but it's a lot more difficult to measure.
I'll give them a call today and lay it down, then back it with a letter of demand. I can get another for $250 or so, but I'll give them the option to source me a used unmodified cylinder.

I was thinking about a retrofit... It wouldn't be too difficult. Not sure that I trust the oil delivery system on them though and premix is not an option.

[TZ350]

So sticking with the original pipe initially,here is the result of welding or inserting the Ex duct and reducing it to 34mm outlet size.
Along with this making a new spigot to match the smaller cylinder exit to the stock pipe header. Check the rise in the resultant exit Mach.
We are already seeing that the powervalve ramp is now becoming mismatched,with a big dip in the midrange.

Being walked through it, it makes so much more sense.

[wobbly]

So as a last sticky plaster fix for the existing pipe,we drop the cylinder exit size to 33mm,add 10mm to the spigot length ( you need a new one anyway ) as this reduces the abrupt taper
out to the header, and reduce the stinger from 23 to 22mm.
Then I adjusted the PV curve a bit to pull up the mid range dip.
All this fiddling with the existing components really only points to where to start with a full house effort.
The Mach is getting there,the PV is looking more effective,and it loves the smaller nozzle.
The TubMax is still way off,but as yet I havnt touched the ignition - will leave that till we start making serious power with real pipe/port synergy.

[tdc211]

Early today. I ran the rs125 pipe in the sim on my proven 34.5hp 104cc case reed. Just to see what that big header 125 pipe looked like on mine . Not saying robs engine is anything like mine.

But mine can make the power. With reliability. With a higher case comp than ideal and a small reed block. I use a 300 pipe temp in real life.
(I have not tried to make a pipe. To run at 400c yet)
This was all figured out ,by testing and watching the delivery ratios and everyrhing else in sim and measuring pipe temp in the belly on the dyno. And knowing when to much delivery short circuited and killed power dead. Even with as good as tranfer angles as you can put in that cylinder. After a while you get a feel for it. I am not a expert. I just kept at it. Make it work and knowing why was my goal I also had help along the way. Like many of us.

Long time ago wob said no 100cc engine has gone 34 or 35hp. Mine's 104cc . 32mm carb. Free blows for life? Lol.
Took forever to achieve. The single best thing I did. Was make a pipe. It was worth more than all the tranfer angle work.
But the pipe probably would never work without the tranfers radius/angles. Now i finially bumped up the midrange to 23 at 9000. And good peak. Matches sim really well.
I just saying. Wish more sim pipes where tested on this great thread. And by no means am I saying pipe below can not be made better . But here is rs125 at 300 and 400c vs my pipe at 300c in sim. On a 104cc engine. Plus I know my works in real life
You will notice.. 36mm header. Same as my ex effective area.
32mm outlet at flange that transitions to a 36.

[jonny quest]

TZ350, what Wobbly said about RV and pipe off throttle. Maybe a RV is next to impossible to EFI

[wobbly]

Long time ago ,if I remember correctly , I said free blowys for life to anyone making over 30Hp at 10500 in a bucket - cant remember if that was 100cc ( with 24mm carb ) or 125 aircooled.
No ones even come close, so I am safe, for now.

[husaberg]

We may have a small terminology misunderstanding since I was using "heat exchanger" to refer to a "radiator" (per Carroll Smith's "Prepare to Win" definition that they are water/air heat exchangers) but I hadn't considered using a liquid/liquid heat exchanger since I've never had occasion to use one in the past. I was envisioning a "radiator" for each circuit.
A water to air rad for each circuit was originally what I was thinking.
But I think it could be done with one and a Water to water heat exchanger. Which I thought you were saying I was looking at that last night.
Water to water heat exchangers can normally if given enough flow and surface area drop the heated water temp to within 3 -4 degrees of the cooler water temp.


So would I be correct that you do think there would be some advantage to having two (a high temp and a low temp) separate cooling circuits so the low temp circuit can more easily stay "low" by not having to deal with the high temp coolant?

cheers,
Michael
Yes,The question is, if it would be lighter to use a second radiator or if the gains in a cooler crankcase would be worth the effort. I think it would have to be suck and see ,IE do a trial.
Or in my case convince Rob to try it out.


Long time ago ,if I remember correctly , I said free blowys for life to anyone making over 30Hp at 10500 in a bucket - cant remember if that was 100cc ( with 24mm carb ) or 125 aircooled.
No ones even come close, so I am safe, for now.
I recall it as air cooled 125cc 24mm carb and 10500rpm.

[Haufen]

Long time ago ,if I remember correctly , I said free blowys for life to anyone making over 30Hp at 10500 in a bucket - cant remember if that was 100cc ( with 24mm carb ) or 125 aircooled.
No ones even come close, so I am safe, for now.

IIrc you did not mention if you were going to provide the service by yourself or have a dedicated serviceperson paid to do it when that question was asked at the time.

Does it only apply for 125cc, or would getting the same specific HP with a larger engine be okay, too?

[TZ350]

TZ350, what Wobbly said about RV and pipe off throttle.

You can time the injection squirt to happen when the pipe is sucking hard. That way most of the fuel is drawn up the transfers. When I get that right there is very little dribble on the dyno deck. As compared to the large puddle left by a carb.



Maybe a RV is next to impossible to EFI

In my dark moments I think so too.

But with EFI I find it very easy to get it to run wide open throttle and make power. Its the near closed throttle positions that are difficult.

And I am certainly finding it very difficult to get it to work properly below 20% throttle in the region where the motor should be on the pipe.

The current thinking is that there is a very large difference in air flow through the motor when the pipe is assisting flow and when its not. The trick is finding a way to see that.

I have found that measuring the pipe or crankcase pressure with a MAP sensor you only get to see the average pressure at that point. And the average pressure drops when the motor is on the pipe because the suck is stronger than the reflected pressure pulse. The magnitude of the average is pretty much the same throughout the power range.

My current thinking is to try and see the difference between high and low pressure in the crankcase. I expect this difference to be greater the harder the pipe sucks.

336295

[wobbly]

My response was simply to demonstrate the stupidity of someone who suggested " just reduce the rpm to 10500 and make the same power ".
It was, and still is ,complete idiocy, to suggest that the bmep required to make over 30hp at 10500 in a 125 bucket engine is even remotely possible with the SOTA we have now.
Luc has convinced himself, but not us,that the task has already been done with new technology.
But I retain the right to pass off the deed to a paid substitute if the need arises.

[F5 Dave]

You can time the injection squirt to happen when the pipe is sucking hard. That way most of the fuel is drawn up the transfers. When I get that right there is very little dribble on the dyno deck. As compared to the large puddle left by a carb.




With EFI I find it very easy to get it to run wide open throttle and make power. Its the near closed throttle positions that are difficult.

And I am certainly finding it very difficult to get it to work properly below 20% throttle in the region where the motor should be on the pipe.

The current thinking is that there is a very large difference in air flow through the motor when the pipe is assisting flow and when its not. The trick is finding a way to see that. Current thinking is to try and see the difference between high and low pressure in the crankcase. I expect the difference to be greater the harder the pipe sucks.

OK so to be a pervert. . . So how about a 24mm carb with a 80 size mainjet and injection to do the rest. You know? Just to get things going with most benefits.

[TZ350]

OK so to be a pervert. . . So how about a 24mm carb with a 80 size mainjet and injection to do the rest. You know? Just to get things going with most benefits.

Interestingly TwoTempe suggested much the same thing to me today. I am going to finish exploring the difference idea first but the carb idea looks like it has possibilities if I get really stuck and have to chose between that and poking my eyes out.

[Flettner]

no, you don't need a carb, pervert.
KTM are doing it, crank case pressure sampling. IE only at a given point in crank rotation, same point every time, build up a 'pressure average change map', I think you will find that's what KTM are doing, they appear to fuel extremely well lower in the throttle range. In fact right through their throttle range.
research what they do!

[philou]

Mota simulator comes with a new tool that automatically adjusts the exhaust pipe.

=> http://www.iwt.com.au/mota.htm

"The optimiser searches automatically for the expansion chamber dimensions that give the maximum power or torque for your engine over a speed range that you input. It runs the tried and tested MOTA simulator many times, altering the expansion chamber dimensions intelligently between simulations, to produce an optimal expansion chamber design. This expansion chamber is not the product of simple correlations as for other products that abound on the web, but an "automatic" design created by MOTA which is a full wave action 2-stroke engine simulator."

a similar tool could be interresting with engmodt

[shnaggs]

no, you don't need a carb, pervert.
KTM are doing it, crank case pressure sampling. IE only at a given point in crank rotation, same point every time, build up a 'pressure average change map', I think you will find that's what KTM are doing, they appear to fuel extremely well lower in the throttle range. In fact right through their throttle range.
research what they do!

Have you ridden a new TPI KTM? Not referring to your TPI YZ, but my brother road a new TPI KTM and says that its terrible down low, like the thing has been neutered, and lacks any kinda feel. IDK cause I havent ridden it yet.

[Flettner]

Have you ridden a new TPI KTM? Not referring to your TPI YZ, but my brother road a new TPI KTM and says that its terrible down low, like the thing has been neutered, and lacks any kinda feel. IDK cause I havent ridden it yet.

You have missed my point, they run clean throughout their range. KTM set the bikes as standard to meet emission constraints, lower to mid is where the fuel is traditionally lost mostly so yes probably a little neutered in feel they do.
But there are other maps that can be loaded that change this, ask Chris Birtch he has a reloaded 300 and loves it. One comment he specifically makes is how clean in runs throughout it's rev range.
with the link you can run a 3D map using revs, TPS and manifold pressure ( conditions). It needs to be feed a relatively smooth signal, thats were timed sampling is needed.
We can change or YZ to have 'sharp' power delivery but the fuel consumption suffers and it gets harder to ride, just like a normal YZ, why would you?

[wobbly]

So Rob, we have a start point for the project of a 32mm duct,and a 36mm header along with around a 22mm stinger nozzle.
The current setup with the RS125 pipe peaks at around 12,000, so the question is, do you want to modify a cylinder to get the correct pipe geometry
and although way more power is available at higher revs, do you want to go there.

[TALLIS]

Long time ago ,if I remember correctly , I said free blowys for life to anyone making over 30Hp at 10500 in a bucket - cant remember if that was 100cc ( with 24mm carb ) or 125 aircooled.
No ones even come close, so I am safe, for now.

It was 125cc aircooled with 24mm carb, and yes it has been achieved in a bucket. For nearly 2 years now running reliably. Seems weird for you to bring this up.... as this is not the type of bet I'd be willing to offer!

[wobbly]

Show me the corrected dyno sheet.

[TALLIS]

Show me the corrected dyno sheet.

It's not my bike and I don't walk around with a dyno sheets in my back pocket as it's not that important to me. The bike will be in Auckland for the two hour later this year, I'll get him to bring it around on the way up if you like. Maybe there's more horses hiding in there somewhere.

[seymour14]

Long time ago ,if I remember correctly , I said free blowys for life to anyone making over 30Hp at 10500 in a bucket - cant remember if that was 100cc ( with 24mm carb ) or 125 aircooled.
No ones even come close, so I am safe, for now.

Yes we did achieve it and have the figures to prove it. The bike runs really well and has won the North Island Championship this year.

The only reason I don't bring it up is I don't want your wrinkly mouth sucking on my knob. :lol:

[wobbly]

Really cool job,but we are still waiting to see over 30RWHp at 10500 from a 125 aircooled on a real dyno sheet.

[seymour14]

Really cool job,but we are still waiting to see over 30RWHp at 10500 from a 125 aircooled on a real dyno sheet.

It should be on our GPR page from a couple of years ago, old news.

I am an engineer and a noted historian. I don't lie.

Don't be so keen to suck my man popsicle, I am happy for you to let it go...:sweatdrop:eek5:

[seymour14]

By the way, I enjoy this thread as much as anyone, so just resume normal transmission!

Carry on the good work.

[husaberg]

Really cool job,but we are still waiting to see over 30RWHp at 10500 from a 125 aircooled on a real dyno sheet. I guess this is it? personally i would say it was 30 at 10501 rpm if only to protect seymours innocence.
https://www.kiwibiker.co.nz/forums/showthread.php/150352-Team-GPR?p=1130960800#post1130960800

[TZ350]

So Rob, we have a start point for the project of a 32mm duct,and a 36mm header along with around a 22mm stinger nozzle.
The current setup with the RS125 pipe peaks at around 12,000, so the question is, do you want to modify a cylinder to get the correct pipe geometry
and although way more power is available at higher revs, do you want to go there.

Hmmmm these are good questions .... :(

I had a plan in mind, that for simplicity and ease of being reproduced, of keeping the NSR cylinder un modified except for the 2mm trimmed off the top and radiusing the leading edge of the PV blades. Which is the setup that most of Team ESE want. All easy stuff. On the other hand, we have two running engines, one with a std NSR cylinder and the other one modified. We are making two more std NSR110's but I am a glutton for max engine development.

Wob could we have two pipe designs.

The one you have developed so far, sure the setup is compromised but it does allow someone using a std NSR cylinder to keep things simple.

And a full house no holds barred total hells death setup where the cylinder is modified in whatever way is required.

I have another two cylinders that may be more or less suitable where the exhaust port and duct has been modified to be more like a RS125 port. Flat(ish) across the top, 52mm wide with the sides bulging outwards like in the attached picture.

336297

Transfers open 115 ATDC and the Exhaust port opens at 80 ATDC on one cylinder and 78 ATDC on the other and the PV is flattened with the front edge radius-ed, the leading edge of the exhaust bridge is also radiused for improved flow coefficient.

336298

Suzuki GP100 bottom end with Kawasaki KE175 rotary valve cover, NSR110 cylinder modified Ex opens at 80ATDC Trans 115 and In 140/85, RS125 NX4 pipe. The same setup as before but with a modified exhaust port.

Wob lets go for the doctor and see what can be done. Modified exhaust duct, nozzle, head shape, crazy wild inlet timing and RPM. With EFI, inlet timing can be nuts and the injectors are good for 13,500 rpm or maybe a little more. The sky's the limit if we go with a carburetor.

[steamroller]

Come back wobb

[TZ350]

336300

Had a Yamaha150 on the dyno tonight. 24+ rwhp.

336299

Yam blue line, std NSR110 red line, looks like we have a bit of work to do to stay ahead of the big 4T's

[mr bucketracer]

Come back wobbblame tyger

[wobbly]

Its OK guys, im more than happy that it can be done, using well executed science and handwork.
But at the time it just appeared to me to be ridiculous with the old cylinders and small carb size.
But now I am getting right on 50 Hp from a 125 kart engine with a 30mm carb, so things change on here even within a short 2 year period.
As im in a wheelchair, im at the right height for girl ass bighting or even knob gobbling, at a push.
Shame all round.

[steamroller]

Its OK guys, im more than happy that it can be done, using well executed science and handwork.
But at the time it just appeared to me to be ridiculous with the old cylinders and small carb size.
But now I am getting right on 50 Hp from a 125 kart engine with a 30mm carb, so things change on here even within a short 2 year period.
As im in a wheelchair, im at the right height for girl ass bighting or even knob gobbling, at a push.
Shame all round.

Good to have you back' now maybe you can fix all the honda rs 125s as they only have 40hp.

[richban]

336300

Had a Yamaha150 on the dyno tonight. 24+ rwhp.

336299

Yam blue line, std NSR110 red line, looks like we have a bit of work to do to stay ahead of the big 4T's

Hey Rob. Do you still have the dyno run from my old FXR? I can't remember how it did. That blue line looks well messy. I wonder whats happening at the top end. 7k is always tricky with exhaust reversion. Do you no what size throttle body it runs?

[TZ350]

.
I think yours was much the same but a better curve. I will have a look for the graph, might take a while as there are 8,000 plus images attached to this thread.

Found It ... Here you go......


Just so us 2T boys know what we are up against.

332407332408

Some time ago Richban and the GPR boys dropped in for a dyno session. Richbans FXR150 pulled 23.9rwHp (red line) which was pretty impressive. The blue line is my air cooled 125 2T, being air cooled it would lose its edge after two or three laps.

332409

I think this is the 20th Team GPR bike and I expect they may have improved the power output a whole lot more, they are looking dangerous.

You have to admire those GPR bikes.

[shnaggs]

You have missed my point, they run clean throughout their range. KTM set the bikes as standard to meet emission constraints, lower to mid is where the fuel is traditionally lost mostly so yes probably a little neutered in feel they do.
But there are other maps that can be loaded that change this, ask Chris Birtch he has a reloaded 300 and loves it. One comment he specifically makes is how clean in runs throughout it's rev range.
with the link you can run a 3D map using revs, TPS and manifold pressure ( conditions). It needs to be feed a relatively smooth signal, thats were timed sampling is needed.
We can change or YZ to have 'sharp' power delivery but the fuel consumption suffers and it gets harder to ride, just like a normal YZ, why would you?

I guess I did miss your point. So where does one find these maps? I've seen a piggy back module that JD jetting is tinkering with, but that is only changing the 2D map. The only other thing is the GET ecu, but if you have other info, I would much like to know! Thanks

[F5 Dave]

Its OK guys, im more than happy that it can be done, using well executed science and handwork.
But at the time it just appeared to me to be ridiculous with the old cylinders and small carb size.
But now I am getting right on 50 Hp from a 125 kart engine with a 30mm carb, so things change on here even within a short 2 year period.
As im in a wheelchair, im at the right height for girl ass bighting or even knob gobbling, at a push.
Shame all round.
Yeah not exactly old cylinders, more like RS 125 committed to aircooled cnc barrel. Fantastic execution but not comparable to a TF125.

[Flettner]

I guess I did miss your point. So where does one find these maps? I've seen a piggy back module that JD jetting is tinkering with, but that is only changing the 2D map. The only other thing is the GET ecu, but if you have other info, I would much like to know! Thanks

Ask Chris B, he apparently had the ECU changed/upgraded by KTM themselves. I guess it's just a matter of money?
And yes how do you find out about the KTM system if not even the dealers know anything about how the system works?
I'm sure someone knows by now. I'm sure KTM HQ (NZ or AU) would be able to help.

[seymour14]

Good to have you back' now maybe you can fix all the honda rs 125s as they only have 40hp.

Top end RS125 at approx 43hp + 15% (difference in loss from running through gearbox compared with direct drive) and you almost have 50hp, so just the sort of figures you might expect from a 125 Kart. But still takes skill to attain.

[TZ350]

OK so to be a pervert. . . So how about a 24mm carb with a 80 size mainjet and injection to do the rest. You know? Just to get things going with most benefits.

Initially I was deeply affected by the suggestion and had to seek counseling to help me recover from the emotional shock. LOL

But actually I have thought about this some more, and you maybe on the money. Good expensive racing carbs have all sorts of trickery like TPS and PWM power jets and still can have a wonky fueling curve.

Looking at data from good EFI runs I see that the most fuel is required at peak torque as you would expect and then the fuel requirement drops away significantly after that. That is hard to do with a carb as carbs richen up with increasing rpm.

A solution maybe, is to have a cheap (OKO) carb set up to run as good as it can be.

Then like you suggest, replace the main jet with one half the size and make up the difference with EFI which can easily be adjusted for very precise fueling from idle to max over rev with a combined fueling result that is better and more accurate than even the most expensive carbs can manage.

With the EFI system precisely filling in the missing half of the main jets range while leaving the carb to do what it does better at low throttle settings. The beauty of this is that you would not need to worry about atmospheric changes as the EFI's MAP sensor takes care of that. I think that this could be very workable, but an admission of defeat so I won't be going there today but I have all the gear required and you never know about tomorrow.

A hybrid setup like this could be very very easily implemented software wise and got running by nearly anyone in an afternoon. And you could easily handle those tricky fuels like E85 that need enriching when the motor gets hotter. This type of hybrid would be a good setup for Methanol too.

I had been married to the idea that it was EFI or Carburetor. F5 Dave and Husaburg, thanks for the idea of combining the best bits from both.

[wobbly]

KTM used that idea Rob, but even less complicated, in their 250 GP engine
They recognized that the only real downfall of the carb was max revs with no throttle, so an injector was used to supply fuel during only this scenario.
Carbs going rich over the top is easily fixed with even a simple rpm switched power jet, PWM is way better of course,and this was used to control fueling at
points in the range where the carb was not so good by Aprilia.
Makes me wonder if EFI is actually worth the effort,expense, complication,when PWM control of a vacuum operated auxiliary fuel jet can easily be made to work perfectly.

A kit Honda's make close to 50 RWHp as you can see from the graph I posted, so this is only down a little from the mid 50s seen at the sprocket by Aprilia.
All kart testing is done at the sprocket as well, but remember those are restricted to a 30mm carb and a poxy straight line PVL ignition.
RS125 customer engines can quite easily go 48.8 Hp at the sprocket, as we used to use in 125 National racing in karts.
So this equates to around mid 40s at the rear wheel.
With the technology we have now I would opine that getting close to that 48 number at the rear wheel would be easy enough with a pipe,head and ignition change.

[TZ350]

Makes me wonder if EFI is actually worth the effort,expense, complication.

Yes me too, but I have got a bee in my bonnet about it and want to see it through if I can.

336313

[steamroller]

Top end RS125 at approx 43hp + 15% (difference in loss from running through gearbox compared with direct drive) and you almost have 50hp, so just the sort of figures you might expect from a 125 Kart. But still takes skill to attain.

Yes you are bang on. 1995 the nx4 was built so we really are behind the eight ball on here. Thanks seymour

[TZ350]

Yes you are bang on. 1995 the nx4 was built so we really are behind the eight ball on here. Thanks seymour

With Wobs guidance I am hoping to close the gap a bit with NX4's or at least catch up to you guys, but with a water cooled version.

[steamroller]

With Wobs guidance I am hoping to close the gap a bit with NX4's or at least catch up to you guys, but with a water cooled version.

With guidance from wobb it will be a walk in the park we are just some hill billies in a hay shed that love to drink.:beer:

[TZ350]

With guidance from wobb it will be a walk in the park we are just some hill billies in a hay shed that love to drink.:beer:

Been past your shed a couple of times lately but no body was home. I love your work and dropping in when I am down that way for a bit of a catch up.

[seymour14]

With guidance from wobb it will be a walk in the park we are just some hill billies in a hay shed that love to drink.:beer:

Speak for yourself.

I live in a woodshed.

[seymour14]

Been past your shed a couple of times lately but no body was home. I love your work and dropping in when I am down that way for a bit of a catch up.

Look forward to it, we'll all catch up.

[peewee]

wob im trying to figure how the aux passages will mesh into the main passage if I make it longer. its 66mm bore with 70mm main passage. I can easily make it 130mm but how will the new aux passages transition into the longer main passage is what im not sure. the dotted line is exactly how it looks now and the outer lines are what I think it should be once the main is 130mm. I can make atleast 110mm of it water cooled. the last 20mm will be a removable spigot but im not sure yet how I want to go about it

[katinas]

First race today with rounded piston on KTM SX 65, very positive. First place and the boy really like this engine new character.

Thanks

[TZ350]

From these results you can see that both are miles off the 0.8 Mach rule of thumb.

I have been playing with EngMod and the method of developing the header section as Wob describes, learning lots, thanks.

[Flettner]

Mark two version TPI engine (EFI) coming along slowly.
gears now hardened, ground and fitted. See the idler is also a counter balance gear. A second one is on the other side of the crank, tied in with the starting mechanism.
Plastic gear drives water pump and autolube pump.
Rotary Valve is yet to be trimmed to the required top end numbers, Gibs will take care of changing timings as revs and load drops.

[wobbly]

Here is some idea of the Aux duct layout.
Two things to note is that the main duct roof slopes down to form a hump,and the floor is horizontal ( making a ski slope hump ), to reduce the area where the Aux side ports intersect.
And the spigots floor should be parallel to the duct floor, and the roof has all the angle change to make the oval ( with ears ) to round transition.
Jan also let on that the shorter he made the septums between the main and Aux ducts, the more power appeared.
I dont know how short is too short, but in the TM kart cylinders I make the wall end shorter than stock by grinding it into a radius, instead of the square shape I have drawn.

[Pursang]

With guidance from wobb it will be a walk in the park we are just some hill billies in a hay shed that love to drink.:beer:

Oh Yeah! Ditto +++:drinknsin

Cheers, Daryl.

[Pursang]

Doing the basic fueling with a carby and supplementary injecting to address the hiccups is not bad, but only one way.

I saved this nearly 20 years ago. (Bob was (still is?) a pretty clever Guy)

bob@bobthecomputerguy.com (Robert Harris) fangle 10 Jan 1999

- Virtually all of the complication of the early mechanical fuel injection
systems involves changing the fuel flow to follow the air flow. This was
and continues to be a result of the carburetor induced mindset that to
respond to a power demand change, you must first change airflow to induce
the new fuel flow.

- The diesel fuel system has always been a model of simplicity, but it is
probably too much of a mind stretch to use as the model. But far closer to
home, racers have achieved excellent results with Hillborn derived constant
flow fuel injection systems. It consists of a pump, a throttle valve, and a
couple of bleeds. The fuel is volumetrically adjusted to the engine size.
During operation it is totally insensitive to air flow - a perfect Al Bundy
"Don't Know - Don't Care". It is still in the top of the heap for shear
power and reliability - its major fault is over rich part throttle, but
someone invented a dejection system and is putting it in somekind of beat up
old furren kar - that's supposed to take care of that.

- After coming over to the Dark Side, you realize that all the driver wants to
do is control the POWER by the throttle - not the air. Since power is first
order related to the amount of fuel burned and second order related to the
amount of air, its backasswards silly to control the air and let the fuel
catch up. Control the fuel and let the air catch up.

- This mind reversal now reduces the fuel control to RPM vs Throttle Position
-easily done by a "stolen" diesel system or simple injectors where the
firing rate is controlled by rpm and the pulse width by the throttle. The
rest is all air control.

- As an exercise for the student, go rethink the fuel air mixture tables vs
power stuff. BUT - keep in mind the tables are for Air Constant - Fuel
varying. Re plot them holding fuel constant - air varying. A very
different picture occurs. Suffice to say that thru reasonable regions,
power will remain approximately constant and directly proportional to fuel
with much less effect of air changes. Remember once more - the existing
table gives you power with the air held constant. Rethink them with the
fuel held constant.
https://s3.amazonaws.com/WEBPOSTS/KIWI+ESE/Air-Fuel+Vs+Fuel+Air.JPG

A 24/7 Reed flap with a servo override could make the subtle air mixture adjustments.

Cheers, Daryl

[SwePatrick]

Here is some idea of the Aux duct layout.
Two things to note is that the main duct roof slopes down to form a hump,and the floor is horizontal ( making a ski slope hump ), to reduce the area where the Aux side ports intersect.
And the spigots floor should be parallel to the duct floor, and the roof has all the angle change to make the oval ( with ears ) to round transition.
Jan also let on that the shorter he made the septums between the main and Aux ducts, the more power appeared.
I dont know how short is too short, but in the TM kart cylinders I make the wall end shorter than stock by grinding it into a radius, instead of the square shape I have drawn.

I figure with a hump/slope in the roof you don´t utilize the backpulse as good as it could be done?
As the pulse will mainly hit the piston.

If having whole ducts roof flat but with an angle of 25 degree, and the hump in the floor instead, how would it compare?

[Muhr]

Now the first prototype is being manufactured! It has not been easy to solve the increase in cooling of inside transfer. The prototype produced now has a 60% chance of success(survive the casting). Just keep my fingers crossed now …

[Frits Overmars]

The prototype produced now has a 60% chance of success(survive the casting).We all learn...336345

[Muhr]

We all learn...336345

mmm just hoping for the best! can not afford to fail:wait:

[philou]

molded air bubble or too much iron particle in the alloy that was attacked by the acid for nickasil plating ?

[Haufen]

Now the first prototype is being manufactured! It has not been easy to solve the increase in cooling of inside transfer. The prototype produced now has a 60% chance of success(survive the casting). Just keep my fingers crossed now …

Did you look into 3d printing also? Especially with small batches of small displacement cylinders 3d printing is quite competitive in regards of pricing. And that with a success rate of normally 100%.

[Muhr]

Did you look into 3d printing also? Especially with small batches of small displacement cylinders 3d printing is quite competitive in regards of pricing. And that with a success rate of normally 100%.

I have a lack of knowledge in 3D printing!
Read below and became a bit unsure if it would be so much easier and 3d print.
If this does not work, it's something I have to look at.


""Thermally Induced Stresses
Your model in Aluminum is 3D-printed using M3DP which is basically a layer-wise welding process. The layer-wise powder melting and its solidification leads to thermally induced stresses upon the cooling down of the melted powder. A design that is not suitable for M3DP can lead to build failures and/or part deformations due to large thermally induced stresses. It is therefore essential to consider the process-specific restriction while designing the part. We advise you to round off or fillet the edges in your design with a minimum radius of 3 mm. Also, avoid sharp edges for the same reason. Try to avoid large material accumulations and, in general, favor organic shapes over edged designs."

edited: because I didn't understand the context of what I wrote

[jonny quest]

I've always been confused with what a tapered bore carb is.

If you start with a 38mm carb, do you bore a taper from the bellmouth to nozzle only? 38mm then continues from nozzle forward? What angle is used?

If it's so good, why don't manufacturers do it?

[Muhr]

I've always been confused with what a tapered bore carb is.

If you start with a 38mm carb, do you bore a taper from the bellmouth to nozzle only? 38mm then continues from nozzle forward? What angle is used?

If it's so good, why don't manufacturers do it?

http://www.amsnow.com/how-to-tech/2005/02/carb-tricks-and-trends

[wobbly]

SwePatrick, as I said the hump in the roof is part of reducing the sudden area expansion within the duct where the Aux ports intersect.
And as far as flow is concerned the humps angle change is so gradual that the returning gas flow stays attached so it does not create any drastic
turbulence or reduction in stuffing efficiency.
In any case the very quickly reducing area above the piston is so small , if you draw a tangential line from the hump to the port face , that at that stage , any inward flow is practically nil.
Proof of the above assumptions on my part is that if you grind out the roof hump in a TM cylinder power is lost , if you add a hump to say a PVP superkart ( read Aprilia copy ) cylinder , power goes up.

Speaking of PVP cylinders, they are all 3D laser printed directly off the CAD file,and have no reliability issues as the raw casting is hipped and stress relieved prior to machining.

[Flettner]

mmm just hoping for the best! can not afford to fail:wait:

trapped gases trying to escape through the molten metal

cores not vented properly, gas needs to escape but via a path, usually through the core prints not the metal.
Or heavy shrinkage due to over heated metal and no feeders or risers in the right place.
What alloy?
Why 'can't afford to fail'? Just cast another one, I'm assuming you have the patterns.

[Muhr]

SwePatrick, as I said the hump in the roof is part of reducing the sudden area expansion within the duct where the Aux ports intersect.
And as far as flow is concerned the humps angle change is so gradual that the returning gas flow stays attached so it does not create any drastic
turbulence or reduction in stuffing efficiency.
In any case the very quickly reducing area above the piston is so small , if you draw a tangential line from the hump to the port face , that at that stage , any inward flow is practically nil.
Proof of the above assumptions on my part is that if you grind out the roof hump in a TM cylinder power is lost , if you add a hump to say a PVP superkart ( read Aprilia copy ) cylinder , power goes up.

Speaking of PVP cylinders, they are all 3D laser printed directly off the CAD file,and have no reliability issues as the raw casting is hipped and stress relieved prior to machining.

I use the same method as PVP done earlier at the same place. Have you got any more info where did they start 3D printing and why they stopped using plaster casting?


trapped gases trying to escape through the molten metal

cores not vented properly, got gas needs to escape but via a path, usually through the core prints not the metal.
Or heavy shrinkage due to over heated metal and no feeders or risers in the right place.
What alloy?
Why 'can't afford to fail'? Just cast another one, I'm assuming you have the patterns.


It's not my picture, it's Frits
I have not failed yet! :innocent:(I use 3d printed wax cores)

[wobbly]

Here are the initial results of mods to Robs GP-NSR110.
The cylinder porting I left alone,as this was capable of around 36Hp at the crank,the way Rob sat it on the case.
In the new sim the cylinder duct is changed,as is the pipe,the ignition, and the PV curve to suit the pipe.
This result is shown against the digitized dyno curve with +12.5 % to show crank power , and the sim as Rob delivered to me.

The new sim is run at .88 Combustion Efficiency , not the .92 as was needed to get the original sim to match.
This I believe is more realistic as it shows the crank power the transfers are capable of theoretically,running the new pipe at .92 shows closer to 40 Hp - I dont think so.
Later I will go thru the sim , page by page to show the general thinking behind the result.

The Mach in the header and the stinger are on the money,the TuBMax is close enough with no deto,so the combination of bmep , compression , ignition lead , and stinger size
are all working together.
Maybe by messing with the PV curve the small dip could be eradicated, but cant be arsed at this time as it doesnt show up in the power curve as an issue.
The pipe is very basic and I havnt even messed with 3 cone rear, as the current shape isnt too shabby.
At the last shot I added 30mm to the inlet,thinking that as it will be EFI the wave action wont affect the the jetting badly, this only added about 1 Hp @9000 but i left it in.

[husaberg]

Here are the initial results of mods to Robs GP-NSR110.
The cylinder porting I left alone,as this was capable of around 36Hp at the crank,the way Rob sat it on the case.
In the new sim the cylinder duct is changed,as is the pipe,the ignition, and the PV curve to suit the pipe.
This result is shown against the digitized dyno curve with +12.5 % to show crank power , and the sim as Rob delivered to me.

The new sim is run at .88 Combustion Efficiency , not the .92 as was needed to get the original sim to match.
This I believe is more realistic as it shows the crank power the transfers are capable of theoretically,running the new pipe at .92 shows closer to 40 Hp - I dont think so.
Later I will go thru the sim , page by page to show the general thinking behind the result.

The Mach in the header and the stinger are on the money,the TuBMax is close enough with no deto,so the combination of bmep , compression , ignition lead , and stinger size
are all working together.
Maybe by messing with the PV curve the small dip could be eradicated, but cant be arsed at this time as it doesnt show up in the power curve as an issue.
The pipe is very basic and I havnt even messed with 3 cone rear, as the current shape isnt too shabby.
At the last shot I added 30mm to the inlet,thinking that as it will be EFI the wave action wont affect the the jetting badly, this only added about 1 Hp @9000 but i left it in.
So what does the pipe look like?
Don't keep us in suspense....ya big tease:innocent:

[F5 Dave]

It's thin at one end. Then a bit of a bulge. Then even thinner at the other end than the first bit.

[Vannik]

SwePatrick, as I said the hump in the roof is part of reducing the sudden area expansion within the duct where the Aux ports intersect.
And as far as flow is concerned the humps angle change is so gradual that the returning gas flow stays attached so it does not create any drastic turbulence or reduction in stuffing efficiency.
In any case the very quickly reducing area above the piston is so small , if you draw a tangential line from the hump to the port face , that at that stage , any inward flow is practically nil.
Proof of the above assumptions on my part is that if you grind out the roof hump in a TM cylinder power is lost , if you add a hump to say a PVP superkart ( read Aprilia copy ) cylinder , power goes up.

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.

[SwePatrick]

Proof of the above assumptions on my part is that if you grind out the roof hump in a TM cylinder power is lost , if you add a hump to say a PVP superkart ( read Aprilia copy ) cylinder , power goes up.




When grinding out the roof, do you add the same area/volume at the floor or walls to maintain the speed?

[lodgernz]

It's thin at one end. Then a bit of a bulge. Then even thinner at the other end than the first bit.

...and this is my theory. And what it is too. Ahem ahem ahem...

[Frits Overmars]

molded air bubble or too much iron particle in the alloy that was attacked by the acid for nickasil plating ?That cylinder never got near an acid bath. Trying to nikasil it would have been throwing money away. Instead it is now on display as modern art
(you can present anything as modern art).


It's not my picture, it's FritsYeah, it was my picture, but not my cylinder. It was the first attempt of a couple of mates to cast a scaled-down RSA cylinder.
They learned a lot (like listening to me :devil2:). Flettner nailed all their mistakes (no surprise there).
On the other hand, I always say: 'Everybody's got to make their own mistakes'.
336371

[Frits Overmars]

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.Honesty compels me to admit that the 1968 Bultaco engine that I used as a basis for my 500-class race bike, originally had a generous exhaust top edge radius, which I enthusiastically removed, together with the inner curves of its transfer ducts (using a hammer and chisel, my special tools in those days). It's a miracle the result still produced about 55 hp from 372 cc. The conversion to rotary inlet, a home-built 40 mm carburetter instead of the 32 mm original, and a fat pipe may have helped a bit.
Boy, did I have a lot to learn...

[jbiplane]

We all learn...336345
Hi Fritz. We finally make (paramotor) engines with opposite exhaust, would intensively test.
https://paraplan.ru/forum/files/14258/lZC7x37u.jpg
https://paraplan.ru/forum/files/14258/M8OnFo60.jpg

The first impression works very well, though we have not correct assumptions how make best possible geometry.

[tdc211]

Even with water close to plug and close to sq.
And msv up at 40
I am still at. .88 to .89 combustion efficency in sim. For 39sim power. And even most small engines I do, end up around this combustion efficency

What's the trick for better combustion efficiency?
I have tried many times to improve on .89.
I can't.

I am guessing Neels post has alot to do wirh that

[wobbly]

I wasnt planning on showing the pipe dimensions till after explaining all the sim details,and the reality is that I chose the length,messed with the header
to get the % correct,and then went bigger on the stinger as the Mach was too high.
End of story.
I have been down the path of over 200 sim runs to get a pipe " right " but I was being paid to do that exercise.
Anyway here is the first guess result for those of you that cant wait.
The cylinder duct is extended 20mm,and this could ( should ) be cooled,then there is the 30mm slip on oval to round transition, as the first pipe element.
The 32mm exit size is a little bigger than the 75% rule, but the 36mm header is equal to the port effective area.
I would change the stinger tube to 1 1/8" by 1.2 wall so the ID would be 26.2 and make the nozzle 10mm long with only a 5mm expansion angle out to the stinger ID.

[wobbly]

Regarding the TM duct roof hump - sadly the rules allow removal of material, not adding any so I have not been allowed to make changes
like lifting the floor ski jump.
But my opinion would be that quite possibly a 25* straight roof would work better together with the floor lifted above BDC a few mm as Jan did
on his cylinder.
This would then make the ski jump higher on the floor and reduce the volume.
But remember that lifting the floor only works if full attention has been paid to matching the blowdown to the transfer STA numbers.
In a full out design, this then involves cutting the Aux around to bore center,and this leads onto adding small end plugs,nothing is simple at this level.

[jamathi]

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.


The roof angle of 25° (?)(I never measured it!) was completely STD ROTAX, I never changed it.
What I did first was enlarging the auxiliary ports, with good results.
But they were too high already.
When I could cast my own cylinders I made them lower and wider
And of course the 'ski jump' was introduced immediately after good results with other engines.
I saw that when a cylinder seized the divider between main and auxiliary frequently cracked.
So I tried to make an 'indestructible' cylinder, by making this divider bigger and longer.
With a nice round corner around it.
I lengthened the divider until almost the exhaust flange.
As I had seen on a Krauser 80cc cylinder.
The result was a very good central exhaust duct flow.
And also a really good separately measured auxiliary duct flow.
But the total exhaust flow diminished, and the engine did not rev.
By gradually shortening the divider wall I got over-rev and power back.
Until the best result was reached by coming back to original ROTAX dimensions.
I was very displeased, away went my dream of an 'indestructible' cylinder......
A pity, but I had to live with it.
It took years of work to reach the best auxiliary duct and ports dimensions.
The main port was made a little bit 'squarer' and narrower around 2001, and the auxiliaries widened to the inside.
The exhaust main port was unradiused until I tried a new exhaust pipe which gave very good low and midrange power,
but wouldn't rev.
Making a radius made it rev, but we lost most of the gained mid- and low range.
We decided to leave it like that....as it was good for the piston ring.
Later we started to raise the exhaust port floor, it looked quite good, but then I retired.
The goal was to reach a point at which the A-ports could have been made still wider.
I don't know if this was ever tried later.
I heard about a 'Honda' type exhaust duct being tried, it lost 1,5HP.....

[Muhr]

Now the first prototype is being manufactured! It has not been easy to solve the increase in cooling of inside transfer. The prototype produced now has a 60% chance of success(survive the casting). Just keep my fingers crossed now …

images from the caster!:2thumbsup

[Tim Ey]

images from the caster!:2thumbsup

Fingers crossed!
If I were you I would also chose to 3D printing in alloy - since 40% of failure would not satisfy me...

[SwePatrick]

images from the caster!:2thumbsup

Nice..
Is it lost wax/lost foam casting?

[Muhr]

Nice..
Is it lost wax/lost foam casting?

Yes, you can say that.

"printed PMMA model on a 3D printer system. Then the model is embedded into plaster and subsequently the model is burned out. Finally vacuum is applied to to the plaster mold and liquid metal is poured into the resulting cavity."

[SwePatrick]

Yes, you can say that.

"printed PMMA model on a 3D printer system. Then the model is embedded into plaster and subsequently the model is burned out. Finally vacuum is applied to to the plaster mold and liquid metal is poured into the resulting cavity."

Depending on skills in moldmaking lostfoam/wax can be very very precise castings.

[Haufen]

The roof angle of 25° (?)(I never measured it!) was completely STD ROTAX, I never changed it.
What I did first was enlarging the auxiliary ports, with good results.
But they were too high already.
When I could cast my own cylinders I made them lower and wider
And of course the 'ski jump' was introduced immediately after good results with other engines.
I saw that when a cylinder seized the divider between main and auxiliary frequently cracked.
So I tried to make an 'indestructible' cylinder, by making this divider bigger and longer.
With a nice round corner around it.
I lengthened the divider until almost the exhaust flange.
As I had seen on a Krauser 80cc cylinder.
The result was a very good central exhaust duct flow.
And also a really good separately measured auxiliary duct flow.
But the total exhaust flow diminished, and the engine did not rev.
By gradually shortening the divider wall I got over-rev and power back.
Until the best result was reached by coming back to original ROTAX dimensions.
I was very displeased, away went my dream of an 'indestructible' cylinder......
A pity, but I had to live with it.
It took years of work to reach the best auxiliary duct and ports dimensions.
The main port was made a little bit 'squarer' and narrower around 2001, and the auxiliaries widened to the inside.
The exhaust main port was unradiused until I tried a new exhaust pipe which gave very good low and midrange power,
but wouldn't rev.
Making a radius made it rev, but we lost most of the gained mid- and low range.
We decided to leave it like that....as it was good for the piston ring.
Later we started to raise the exhaust port floor, it looked quite good, but then I retired.
The goal was to reach a point at which the A-ports could have been made still wider.
I don't know if this was ever tried later.
I heard about a 'Honda' type exhaust duct being tried, it lost 1,5HP.....

Thanks for sharing, Jan. Would you be interested in playing around with a simulation model of the RSA to see if and where things could have been improved even further in the past? In my model, which is based on an APF cylinder from the 2011 season and a different inlet (as I only have the cylinder and not the whole engine), I broke into the 60ies some time ago (6+ hp over baseline calibration which I set to 54 hp. sim data predicted same or slightly better detonation behaviour (TuBmax)).

-------------------------

By the way, I'd be willing to trade detailed information about the 2011 cylinder in exchange for the same information of the last version of Jan's work (that would be 2007 correct?). Anyone interested please drop me a line.

Would be interesting to see if and what had been changed after Jan retired.

[wobbly]

There is nothing secret about the RSA125 cylinder, nor most of the engine dimensions,except for fine detail about the 3D ignition curve, the PV curve and the PWM operation of the
PJ.
Here is a RSA125 pack that has been added to and changed by several people over a long period.
This just adds to everyones data knolwedge on here so how about you publish what you have Haufen.
Its easy to go over 60 Hp with the Aprilia sim , just change the Ex duct to the guidelines I have published and adapt the pipe header to suit.

Bugger - I cant upload a .pack file on here, can Admin fix this please.

[Flettner]

ok, lost wax casting in plaster?
One of the reasons sand is still used in casting items with lots of core surface area is it's ability to 'breath' , let gas escape. Often even drilling holes into the core through the core prints (lugs that support the core in place) to facilitate easy gas exit. Plaster?
Also shrinkage, aluminium will shrink as it solidifies (obviously) but this means as the aluminium solidifies it will need extra material supplied to the cavity, or the metal will not fill the cavity accurately or worse still cavities will appear within the the metal itself, holes. What is required is a 'feeder' of molten metal above this solidifying cavity.
You really want what is termed a freeze line running up your casting as it cools, bottom first, with the 'feeder' solidifying last having feed all casting first.
This will need to be accounted for in your wax pattern. How much does the wax shrink? how does that affect accuracy? what wax used? bee wax has least shrinkage.
Seems a messy process, what not use your 3D model to print actual patterns and core boxes and cast in CO2 sand?

[husaberg]

ok, lost wax casting in plaster?
One of the reasons sand is still used in casting items with lots of core surface area is it's ability to 'breath' , let gas escape. Often even drilling holes into the core through the core prints (lugs that support the core in place) to facilitate easy gas exit. Plaster?
Also shrinkage, aluminium will shrink as it solidifies (obviously) but this means as the aluminium solidifies it will need extra material supplied to the cavity, or the metal will not fill the cavity accurately or worse still cavities will appear within the the metal itself, holes. What is required is a 'feeder' of molten metal above this solidifying cavity.
You really want what is termed a freeze line running up your casting as it cools, bottom first, with the 'feeder' solidifying last having feed all casting first.
This will need to be accounted for in your wax pattern. How much does the wax shrink? how does that affect accuracy? what wax used? bee wax has least shrinkage.
Seems a messy process, what not use your 3D model to print actual patterns and core boxes and cast in CO2 sand?
One thing in plaster and wax's Favor Flet, is that it allows very fine detail and given that the plaster is also an excellent insulator, maybe it should actually have less problems as it might not cool as quick as a sand mould does. I haven't tried it of course.... But it seems plausible.

[Flettner]

with my copy cast F9 cylinder head, in CO2 sand, it's even got Made in Japan copied in fine detail, done right sand has excellent finnish.

[husaberg]

with my copy cast F9 cylinder head, in CO2 sand, it's even got Made in Japan copied in fine detail, done right sand has excellent finnish.
Is Japan the Maori word for Waikato:msn-wink:

[Niels Abildgaard]

Hi Fritz. We finally make (paramotor) engines with opposite exhaust, would intensively test.
https://paraplan.ru/forum/files/14258/lZC7x37u.jpg


The first impression works very well, though we have not correct assumptions how make best possible geometry.

Looks interesting and a lot of air resistance.
Has Turbocharging been considered?
The job of an aircraft engine is to deliverl longtime,reliable power for less mass , air resistance and fuel.
Most people here tries to maximise power from a single 125 ccm cylinder.
Your engine as a V2 it will be much kinder to propeller and aircraft and turbocharging will minimize noise and infrared signature.
Fast throttle responce is not so important as on a kart or bike.

[Muhr]

ok, lost wax casting in plaster?
One of the reasons sand is still used in casting items with lots of core surface area is it's ability to 'breath' , let gas escape. Often even drilling holes into the core through the core prints (lugs that support the core in place) to facilitate easy gas exit. Plaster?
Also shrinkage, aluminium will shrink as it solidifies (obviously) but this means as the aluminium solidifies it will need extra material supplied to the cavity, or the metal will not fill the cavity accurately or worse still cavities will appear within the the metal itself, holes. What is required is a 'feeder' of molten metal above this solidifying cavity.
You really want what is termed a freeze line running up your casting as it cools, bottom first, with the 'feeder' solidifying last having feed all casting first.
This will need to be accounted for in your wax pattern. How much does the wax shrink? how does that affect accuracy? what wax used? bee wax has least shrinkage.
Seems a messy process, what not use your 3D model to print actual patterns and core boxes and cast in CO2 sand?

My knowledge of how this process is relative to others is quite limited. You can certainly find more info here https://www.formkon.com/prototypes-aluminium-magnesium/

[jbiplane]

Looks interesting and a lot of air resistance.
Has Turbocharging been considered?
The job of an aircraft engine is to deliverl longtime,reliable power for less mass , air resistance and fuel.
Most people here tries to maximise power from a single 125 ccm cylinder.
Your engine as a V2 it will be much kinder to propeller and aircraft and turbocharging will minimize noise and infrared signature.
Fast throttle responce is not so important as on a kart or bike.

Hi Niels

This is 294cc boxer with 2 cylinders 66bore 43stroke 10,5 compression ratio. It used for paramotoring with direct propeller
drive. We need max power on relatively slow rpm 6000...7000.
The set as on picture weight 9.5 kg, installed chinese copy of Mikuni 32mm. We got from this engine 21hp at 6800 rpm.
Hope with this "opposite" resonator will get a bit more.
If we get 27 then we will be completely happy. As nexts step will install fuel injection.
How install lighweight turbocharger on this with common crancase and shnurle transfers?

[Niels Abildgaard]

Hi Niels

This is 294cc boxer with 2 cylinders 66bore 43stroke 10,5 compression ratio. It used for paramotoring with direct propeller
drive. We need max power on relatively slow rpm 6000...7000.
The set as on picture weight 9.5 kg, installed chinese copy of Mikuni 32mm. We got from this engine 21hp at 6800 rpm.
Hope with this "opposite" resonator will get a bit more.
If we get 27 then we will be completely happy. As nexts step will install fuel injection.
How install lighweight turbocharger on this with common crancase and shnurle transfers?

Hello

I tried to delete my post when I discovered that it was a paramotor engine and not for a drone,but You were to fast answering.
What is prop diameter and with 28 kg per litre/5 bar mean effective pressure You are doing very fine I think.
The turbo shall probably be blowing into a volume before crankcase with reed valves.Without FI it will be very dangerous for the pilot.

[flyonly]

If a bike has a counterbalance shaft and you are only going to use it for racing so idling isn’t going to be an issue is it worth removing? 50cc bike so I am guessing every little bit helps?


Sent from my iPhone using Tapatalk

[husaberg]

If a bike has a counterbalance shaft and you are only going to use it for racing so idling isn’t going to be an issue is it worth removing? 50cc bike so I am guessing every little bit helps?


Sent from my iPhone using Tapatalk

Out of balance actually engines cost HP..
The rider finds it harder to maintain concentration when engines vibrate
Not only that but the chassis needs to be beefier.
Also less parts of the bike try to escape of it when you leave it in place.
Another advantage is that they lessen the gyro force from the crankshaft clearly important in a big bore bike.
The crankcases are generally designed around the engine having a balance shaft.

[F5 Dave]

Except that when you raise the peak revs 4000rpm any factory balance attempt - you've just negated.

[TZ350]

Hi Fritz. We finally make (paramotor) engines with opposite exhaust,

Very clever piece of work, I like it. Love that exhaust, brilliant idea.

[wobbly]

There are several factors at play with removing the balance shaft ( apart from the balance factor ).
First is that if the engine is re balanced correctly, there will be no discernible vibration,there are millions of single cylinder engines running around that dont make the rider loose
concentration due to bad vibes.
Then there is the issue of inertia.
The balance shaft runs at crank speed so in effect adds to the rotational inertia of the engine.
Loosing the balance shaft will change that inertia considerably.
There are two schools of thought on this.
Of course basic physics says a low inertia system will accelerate faster,but in a 2T it has been well documented that high inertia cranks make way more overev power.
Take a stock RS125 Honda and remove the flywheel, suddenly it wont rev at all.
That is why HRC and VHM offer high inertia option cranks for total loss use.
And take a look at the amount of Mallory on the periphery of an Aprilia or TM125 kart crank - they didnt add all that heavy metal,to make the engine slower at the rpm its used at most.

[lodgernz]

Here is some idea of the Aux duct layout.
Two things to note is that the main duct roof slopes down to form a hump,and the floor is horizontal ( making a ski slope hump ), to reduce the area where the Aux side ports intersect.
And the spigots floor should be parallel to the duct floor, and the roof has all the angle change to make the oval ( with ears ) to round transition.


Wobbly, I suspect that the dimensions of the exhaust duct as in your drawing are based on experience and experiment, rather than on empirical theory. In that case, I also suspect that the engines that have provided the data have mostly been "square" in bore x stroke. My Honda T-port engine is badly oversquare at 53 x 44. Do you think the same duct length dimensions still apply, based as they are, solely on the bore size?
Could the exaggerated bore/stroke ratio require remodelling the "1.5 x bore" and "2 x bore" data?

[wobbly]

Absolutely the use of " badly " oversquare dimensions will affect the duct geometry.
The end of the road effect of the big bore is that this will severely limit the achievable bmep.
You can see this going on in Robs GP-NSR110.It needs absolutely at the limit port timings to only achieve 12 Bar bmep.
When the bmep is limited like this,the end result is alot lower power capability - thus the bulk amount of cold mixture needed for sufficient plugging effect is reduced commensurately.
So using my simple guidelines ( as you say based on high efficiency square engines ) is applying a flawed rule of thumb to a flawed engine design.
Well spotted - never even remotely occurred to me.
Thus the reverse will apply to some extent with say 250cc road racing engines derived from the very undersquare MX bikes that run 66.4 X 72 stroke.
But as the best design would be that as used by Honda in its V twin 500 GP engine of close enough to 68 square,the difference in duct lengths in that case arent huge.

[lodgernz]

Absolutely the use of " badly " oversquare dimensions will affect the duct geometry.
The end of the road effect of the big bore is that this will severely limit the achievable bmep.
You can see this going on in Robs GP-NSR110.It needs absolutely at the limit port timings to only achieve 12 Bar bmep.
When the bmep is limited like this,the end result is alot lower power capability - thus the bulk amount of cold mixture needed for sufficient plugging effect is reduced commensurately.
So using my simple guidelines ( as you say based on high efficiency square engines ) is applying a flawed rule of thumb to a flawed engine design.
Well spotted - never even remotely occurred to me.
Thus the reverse will apply to some extent with say 250cc road racing engines derived from the very undersquare MX bikes that run 66.4 X 72 stroke.
But as the best design would be that as used by Honda in its V twin 500 GP engine of close enough to 68 square,the difference in duct lengths in that case arent huge.

Thanks Wobbly. I think you are saying that my duct needs to be shorter than your guidelines suggest for a nice square engine. Please correct me if I'm wrong.

[peewee]

Thanks Wobbly. I think you are saying that my duct needs to be shorter than your guidelines suggest for a nice square engine. Please correct me if I'm wrong.

maybe theres some way to test this in engmod. otherwise a real world test is the only way. my engines are mostly oversqaure like yours

[husaberg]

Except that when you raise the peak revs 4000rpm any factory balance attempt - you've just negated.
I don't agree, I say this as the counter balance shafts as I believe a general rule are just as effective at any revs.
What I think is occurring is that when the engine is modified for higher revs as you say.
When these modifications occur the primary balance is also changed ie different rod, rod length, crankpin and piston weights etc
If these changes were accounted for and the crankshaft was rebalanced back to its original factory balance factor (generally 50%) as it was originally designed at there should be no real change. Despite the higher revs.
I base this assumption on nearly all counterbalanced singles regardless of the revs they operate at have both their primary balance and secondary balance shafts factors set at 50%.
Removing the balance shaft in itself generally requires rebalancing the crankshafts primary balance factor anyway.
Yes of course you can do this and it will if done correctly to suit the engine speed and chassis as Wobbly says above,
But while this no doubt works it only works over a narrow rev range because it just moves the out of balance forces to another rev range rather than lessening them over the whole spread of engine revs as a balance shaft so effectively does.
Just my opinion of course I used to biff them out of course same as everyone else did.
But after reading the opinions of Frits, Jan and Ian Harrison I changed my mind.
I also think the contra rotating Balance shaft on a two stroke also has advantages with lessening the gyro force (I would like to try a CR500 with one and see if it really steers better)

[F5 Dave]

There are several factors at play with removing the balance shaft ( apart from the balance factor ).
First is that if the engine is re balanced correctly, there will be no discernible vibration,there are millions of single cylinder engines running around that dont make the rider loose
concentration due to bad vibes.
Then there is the issue of inertia.
The balance shaft runs at crank speed so in effect adds to the rotational inertia of the engine.
Loosing the balance shaft will change that inertia considerably.
There are two schools of thought on this.
Of course basic physics says a low inertia system will accelerate faster,but in a 2T it has been well documented that high inertia cranks make way more overev power.
Take a stock RS125 Honda and remove the flywheel, suddenly it wont rev at all.
That is why HRC and VHM offer high inertia option cranks for total loss use.
And take a look at the amount of Mallory on the periphery of an Aprilia or TM125 kart crank - they didnt add all that heavy metal,to make the engine slower at the rpm its used at most.

So. . . Why?
To an extent there is the stored energy which you have done work to accelerate. I can accept that a clutch start would benefit at least with roadbike gearbox for that potential energy release.
But overrev important in higher gears takes a while to expend. As the combustion efficiency fails and pipe cools surely the power collapsing with that much drag on it couldn't be compensated by the stored energy?
Or are you saying as I think you are, an engine capable of producing power after peak just can't with too light of a flywheel? (Or rather rotational mass) just can't think why that would be as I finish my piece of fudge. (Very nice, but a weakness that clearly didn't help my 50cc racing career)

Damn, this is going to bug me.

[jfn2]

wobbly.... For us poor hillbilly folk what is .. commensurately. Where do you guys pull these words from? Please explane.

[husaberg]

wobbly.... For us poor hillbilly folk what is .. commensurately. Where do you guys pull these words from? Please explane.

The poor hillbilly types that's auriferous.....:lol:


So. . . Why?
To an extent there is the stored energy which you have done work to accelerate. I can accept that a clutch start would benefit at least with roadbike gearbox for that potential energy release.
But overrev important in higher gears takes a while to expend. As the combustion efficiency fails and pipe cools surely the power collapsing with that much drag on it couldn't be compensated by the stored energy?
Or are you saying as I think you are, an engine capable of producing power after peak just can't with too light of a flywheel? (Or rather rotational mass) just can't think why that would be as I finish my piece of fudge. (Very nice, but a weakness that clearly didn't help my 50cc racing career)

Damn, this is going to bug me.
Wob and Frits can correct me if I am wrong but I believe the higher inertia keeps the crank turning at a more consistent speed ie less stop start at TDC and BDC.
I have a pic of a Aprilia crank with a heap of tungsten inserts added for increased inertia somewhere. they chose to do this rather than simply making the other areas lighter with alloy plugs.
Of course I could be said some of the reason for this was likely to avoid have cut outs in the crank wheels, but they sure put a heck of a lot of weight into that crank.

[wobbly]

As I scored 98% in Scholarship English I rarely suffer from anomia,so expanding commensurate ( yea that's in google ) by adding ly makes it a " doing " word for you hillbilly folk ie
the act of making something commensurate.

But getting back to important shit - Frits has always criticized my blatant uselessness in applying rules of thumb to the duct geometry based on the bore size and the port effective area.
He is of course annoyingly correct,the whole process should be tied to the Blowdown STA.
Thus we would have an exit geometry that is related to the power achievable , of a certain swept volume , at a certain rpm.

Once some clever fuck with more time and intellect than I , looks seriously into this , then the theory could easily be extended to a new relationship that ties the Blowdown capability to the volume of available
cool plugging charge needed, to support the bmep being produced.

That would be a cool Masters or PhD project , if 2T technology was even remotely interesting or relevant ,to engineering students focused on the future electric shitter everything - no " engines " involved.

[tdc211]

My duct outet on 104cc engine is a 32. But not far back It's a actually a 30.2mm. So I use 30.2mm in sim. And the roof is pretty close to flat. I literally copied the 13 up ktm85 roof.
As the older (pre 13) 105 cylinder was completly different here .

[Larry Wiechman]

Frits has always criticized my blatant uselessness in applying rules of thumb to the duct geometry based on the bore size and the port effective area.
He is of course annoyingly correct,the whole process should be tied to the Blowdown STA.
Thus we would have an exit geometry that is related to the power achievable , of a certain swept volume , at a certain rpm.



These rules of thumb for exhaust duct and pipe geometry work fine for well developed 125cc engines. Are they scalable to use on a 86 x 86 500cc engine?
The insight into the use of EngMod was fantastic, Thank You!

[philou]

Wob and Frits can correct me if I am wrong but I believe the higher inertia keeps the crank turning at a more consistent speed ie less stop start at TDC and BDC.


less speed variation on a rotation cycle leads to a less disturbed flow

difficult for me to explain in English :cry:

[teriks]

<snip>
Yes of course you can do this and it will if done correctly to suit the engine speed and chassis as Wobbly says above,
But while this no doubt works it only works over a narrow rev range because it just moves the out of balance forces to another rev range rather than lessening them over the whole spread of engine revs as a balance shaft so effectively does.
<snip>
I never understood this talk about balancing for a certain rpm. In my world, as long as we disregard everything around the crank there is one optimum balance factor to minimize the forces on the crank bearings.
The frequency and magnitude of the forces for sure varies with rpm, but how does the optimum balance factor for minimum vibrational forces vary?

For sure, in the real world you have to consider resonances in the full assembly, I guess mainly the frame in the case of bike, and as been stated previously in the thread in witch direction the vibrations have the least negative effect etc. I guess this is where the "balance for at certain rpm" comes into the picture, right?

[husaberg]

I never understood this talk about balancing for a certain rpm. In my world, as long as we disregard everything around the crank there is one optimum balance factor to minimize the forces on the crank bearings.
The frequency and magnitude of the forces for sure varies with rpm, but how does the optimum balance factor for minimum vibrational forces vary?

For sure, in the real world you have to consider resonances in the full assembly, I guess mainly the frame in the case of bike, and as been stated previously in the thread in witch direction the vibrations have the least negative effect etc. I guess this is where the "balance for at certain rpm" comes into the picture, right?

I am certainly no physicist and I have never questioned why, but my best guess would be combination of the different primary balance factor actually moves the rpm range so that the secondary forces won't coincide with the primary imbalance force felt at the rev range where the normal operating range occurs, plus also as you mention moving it out of the range where the frame resonates with the engine.
I based these assumptions on having noticed when engine manufactures have spec'd rev ranges, different frames and different engine inclinations for the same engines this resulted in different primary factors being recommended (old pommy shitboxs)
All I know for sure is when we talk about balance factor or oils it always ends in a disagreement on here. likely because the vibrations are generally not measured, so the end up being assessed by people which are subjective.


less speed variation on a rotation cycle leads to a less disturbed flow

difficult for me to explain in English :cry:
Less collapse of the flow established.
No idea but my own assumption was based on a even fire 4 cylinder bike that fires every 90 degress (early NSR) making less peak power as it is made to fire progressively more to that of a twin (in pair every 180 ie two up refered later to as a screamer) or more big a single (big bang) when each of these changes occurred the engines also lost over rev.

[Greg85]

There are several factors at play with removing the balance shaft ( apart from the balance factor ).
First is that if the engine is re balanced correctly, there will be no discernible vibration,there are millions of single cylinder engines running around that dont make the rider loose
concentration due to bad vibes.
Then there is the issue of inertia.
The balance shaft runs at crank speed so in effect adds to the rotational inertia of the engine.
Loosing the balance shaft will change that inertia considerably.
There are two schools of thought on this.
Of course basic physics says a low inertia system will accelerate faster,but in a 2T it has been well documented that high inertia cranks make way more overev power.
Take a stock RS125 Honda and remove the flywheel, suddenly it wont rev at all.
That is why HRC and VHM offer high inertia option cranks for total loss use.
And take a look at the amount of Mallory on the periphery of an Aprilia or TM125 kart crank - they didnt add all that heavy metal,to make the engine slower at the rpm its used at most.
hi336418336419336420 wobbly good job for tm and sharing your tests...we're talking about high inertia crankshaft and tm crankshaft ,I analyzed that of the tmkz10c maneton 22, weight of the two half cranks 2066g,weight of the complete connecting rod 260g,complete piston(original tm)176g,a total weight of 2502g.comparing that of the modena it makes 2760g complete without piston saying high inertia as much!!effectively it seeks much further the power compared to the tm ,I think the weight influence on the acceleration of the crankshaft? the balancing factor that depends or one wants the power...?a compromise for the use of the engine

[Frits Overmars]

Removing the balance shaft... moves the out of balance forces to another rev range.The proportion of horizontal to vertical balance forces won't change with the revs, but the vibration frequency will, and at a certain rpm it may coincide with the natural frequency of the handlebars or footrests, messing up feedback and causing rider fatigue, or with the natural frequency of the frame, causing it to crack, or with the natural frequency of the float system, messing up the carburation.
I would never remove the balance shaft from any engine. I would however make sure that it doesn't double as a cream whipper.
We once worked on a Cagiva engine, used for 125cc production racing in Italy. The rulebook said no touching of the 'thermal parts' but it didn't say anything about sliding a nice round tube over the half-round balance shaft that was immersed up to its neck in gearbox oil. Making it round was good for over 1 hp.


To an extent there is the stored energy which you have done work to accelerate... overrev important in higher gears takes a while to expend. As the combustion efficiency fails and pipe cools surely the power collapsing with that much drag on it couldn't be compensated by the stored energy?Any form of stored kinetic energy can only be made to work when you try to slow it down. For rotating energy in an engine this means that you turn it to use when you shift up. But if stored energy in a rotating mass would increase the rpm of that mass, it would mean augmenting the very amount of stored energy, something that is not going to happen in this universe. Try to imagine a motorcycle on an inertia dyno, putting a lot of rotating energy into the dyno drum. If the bike chain breaks during a test, do you think the drum rpm will increase because of the energy stored in it?


...talking about high inertia crankshaft and tm crankshaft ,I analyzed that of the tmkz10c maneton 22, weight of the two half cranks 2066g, weight of the complete connecting rod 260g, complete piston(original tm)176g,a total weight of 2502g. comparing that of the modena it makes 2760g complete without piston saying high inertia..So the Modena engine has more inertia than the TM engine? You may well be right Greg, but you cannot establish that through weighing.
Scales can determine mass, but they cannot determine how far from the center of rotation the bulk of that mass is concentrated.
Take a look at the Aprilia crankshafts below. There is a lot of tungsten concentrated near their outer diameter. Now think of a crankshaft with even more tungsten,
but concentrated on a smaller diameter. It will certainly be heavier than the pictured crankshafts, but it may well have less inertia.
336421


Frits has always criticized my blatant uselessness in applying rules of thumb to the duct geometry based on the bore size and the port effective area.
He is of course annoyingly correct, the whole process should be tied to the Blowdown STA.Don't be so hard on yourself Wob. I wrote that the blowdown STA approach may be theoretically correct, but that your method has practical value because STA cannot be measured; it has to be calculated, whereas your method only requires measuring, which is much easier to apply for those wo do not have access to a sim program.
By the way, your remark "He is of course annoyingly correct" makes me wonder: did you ever talk to my ex-wife?

[jbiplane]

Hello
Hi Niels
What is prop diameter ...
We tried it with 680mm propeller. Seems this exhaust have at least 2 resonance rpm. At a moment I have no idea how simulate Bi-resonator
in 1d... May be Engmod2t can be used by some trick?

Thanks TZ350 ;)

Very clever piece of work, I like it. Love that exhaust, brilliant idea.
My friend was inspired by this idea tried make the same shape on inline 500cc Rotax 503 and got good propeller trust from a first try.

[peewee]

As I scored 98% in Scholarship English I rarely suffer from anomia,so expanding commensurate ( yea that's in google ) by adding ly makes it a " doing " word for you hillbilly folk ie
the act of making something commensurate.

But getting back to important shit - Frits has always criticized my blatant uselessness in applying rules of thumb to the duct geometry based on the bore size and the port effective area.
He is of course annoyingly correct,the whole process should be tied to the Blowdown STA.
Thus we would have an exit geometry that is related to the power achievable , of a certain swept volume , at a certain rpm.

Once some clever fuck with more time and intellect than I , looks seriously into this , then the theory could easily be extended to a new relationship that ties the Blowdown capability to the volume of available
cool plugging charge needed, to support the bmep being produced.

That would be a cool Masters or PhD project , if 2T technology was even remotely interesting or relevant ,to engineering students focused on the future electric shitter everything - no " engines " involved.

maybe somebody, anybody, has a general idea how long the exh passage should be ,in relation to bore diam on our oversqaure shitboxes. even if theyre a mile off, a ballpark would be great. hell even a wild guess. its not like the consequence would be 10hp loss i wouldnt think. my peanut brain is telling me, alittle too long would be better than too short.

[Frits Overmars]

maybe somebody, anybody, has a general idea how long the exh passage should be ,in relation to bore diam on our oversqaure shitboxes. even if theyre a mile off, a ballpark would be great. hell even a wild guess... alittle too long would be better than too short.If the exhaust duct can contain a volume equal to the cylinder capacity of the engine, it will be long enough. Wild enough for you?

[Muhr]

We once worked on a Cagiva engine, used for 125cc production racing in Italy. The rulebook said no touching of the 'thermal parts' but it didn't say anything about sliding a nice round tube over the half-round balance shaft that was immersed up to its neck in gearbox oil. Making it round was good for over 1 hp.


That one I loved smart!:niceone: trying to figure out any engine that has the balance shaft down in the cream that i can add this to. have to think about it for a while

[Vannik]

If the exhaust duct can contain a volume equal to the cylinder capacity of the engine, it will be long enough. Wild enough for you?

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

[Frits Overmars]

That one I loved smart!:niceone: trying to figure out any engine that has the balance shaft down in the cream that i can add this to. have to think about it for a while336423
Like this one, Muhr? There are a lot of these around, and they're supposed to be competition engines :p.


I was thinking along those same lines - are we equally wild?It's either that, or equally crazy, Neels :D.

[Greg85]

The proportion of horizontal to vertical balance forces won't change with the revs, but the vibration frequency will, and at a certain rpm it may coincide with the natural frequency of the handlebars or footrests, messing up feedback and causing rider fatigue, or with the natural frequency of the frame, causing it to crack, or with the natural frequency of the float system, messing up the carburation.
I would never remove the balance shaft from any engine. I would however make sure that it doesn't double as a cream whipper.
We once worked on a Cagiva engine, used for 125cc production racing in Italy. The rulebook said no touching of the 'thermal parts' but it didn't say anything about sliding a nice round tube over the half-round balance shaft that was immersed up to its neck in gearbox oil. Making it round was good for over 1 hp.

Any form of stored kinetic energy can only be made to work when you try to slow it down. For rotating energy in an engine this means that you turn it to use when you shift up. But if stored energy in a rotating mass would increase the rpm of that mass, it would mean augmenting the very amount of stored energy, something that is not going to happen in this universe. Try to imagine a motorcycle on an inertia dyno, putting a lot of rotating energy into the dyno drum. If the bike chain breaks during a test, do you think the drum rpm will increase because of the energy stored in it?

So the Modena engine has more inertia than the TM engine? You may well be right Greg, but you cannot establish that through weighing.
Scales can determine mass, but they cannot determine how far from the center of rotation the bulk of that mass is concentrated.
Take a look at the Aprilia crankshafts below. There is a lot of tungsten concentrated near their outer diameter. Now think of a crankshaft with even more tungsten,
but concentrated on a smaller diameter. It will certainly be heavier than the pictured crankshafts, but it may well have less inertia.
336421

Don't be so hard on yourself Wob. I wrote that the blowdown STA approach may be theoretically correct, but that your method has practical value because STA cannot be measured; it has to be calculated, whereas your method only requires measuring, which is much easier to apply for those wo do not have access to a sim program.
By the way, your remark "He is of course annoyingly correct" makes me wonder: did you ever talk to my ex-wife?

hi frits thanks to answer ,yes then the modena has the heaviest crankshaft weighed 2760g without piston after the crankshaft tm without piston 2326g, the masses concentrated side opposite maneton 2 tungtstene 13mm, that of the middle17mm tungsten and the others alu, a total of 370g added weight,how should I go about calculating the tm balance factor? I would like to modify the one of the modena, the idea of aprilia was to concentrate the maximum of mass opposite to the throttle for a better acceleration interesting the photos thanks

[Frits Overmars]

how should I go about calculating the tm balance factor?Crankshaft balancing has been covered here some time ago. I'm sorry I can't point you to the exact page, but maybe you can find it by searching for the pictures I used:
336426 336425 336424

[Grumph]

I would never remove the balance shaft from any engine. I would however make sure that it doesn't double as a cream whipper.
We once worked on a Cagiva engine, used for 125cc production racing in Italy. The rulebook said no touching of the 'thermal parts' but it didn't say anything about sliding a nice round tube over the half-round balance shaft that was immersed up to its neck in gearbox oil. Making it round was good for over 1 hp.

Thanks Frits - for giving me something to think about. Not in relation to 2T's but the ever more common balance shafts in 4T's. Another way to consider reducing windage in the crankcase....

How'd you secure the overlay tube ? Shrink and spotweld ?

[F5 Dave]

. . .

Any form of stored kinetic energy can only be made to work when you try to slow it down. For rotating energy in an engine this means that you turn it to use when you shift up. But if stored energy in a rotating mass would increase the rpm of that mass, it would mean augmenting the very amount of stored energy, something that is not going to happen in this universe. Try to imagine a motorcycle on an inertia dyno, putting a lot of rotating energy into the dyno drum. If the bike chain breaks during a test, do you think the drum rpm will increase because of the energy stored in it?

. . .
Thanks the dyno analogy made that part real clear .
But it still leaves me in the dark why over rev is detrimentallly affected by too light of rotational mass.

[wobbly]

Ha,ha,yes Frits I keep in touch with your ex wife on Tinder.

In relation to the duct volume - I am about to receive a new casting from TM that I designed with the Wobbly duct exit configuration and ears of the Aprilia.
Once I have done the dyno work to optimize the exit and spigot etc,I will measure the volume.
At least that will show the ratio that a full noise square 125 likes,but still leaves the bmep out of the equation.
As I said before, the greater the bmep,the greater the volume of cold plugging mixture is required.
This makes wild guesses even less relevant when comparing say the near 15Bar of an RSA vs the 12Bar of Robs GP-NSR110.

[husaberg]

Thanks Frits - for giving me something to think about. Not in relation to 2T's but the ever more common balance shafts in 4T's. Another way to consider reducing windage in the crankcase....

How'd you secure the overlay tube ? Shrink and spotweld ?
You could always block of the shaft from the crankshaft totally and use sealed bearings.
When they were given the opportunity to design the balance shaft from scratch, they did this. no porkchops at all

336427Rather than below little oil covered oil beater
336428336429

Here are some random Aprilia cranks.
336433336435336439

Crankshaft balancing has been covered here some time ago. I'm sorry I can't point you to the exact page, but maybe you can find it by searching for the pictures I used:


https://www.kiwibiker.co.nz/forums/showthread.php/183350-Pete-s-TF125-build?p=1131053555#post1131053555
Has the links
But its all covered in tuning for speed.

[Michael Moore]

Thanks the dyno analogy made that part real clear .
But it still leaves me in the dark why over rev is detrimentallly affected by too light of rotational mass.

FWIW, I remember being told that at Daytona a higher rotational mass crank was preferred because at top speed on the banking a gust of head wind would slow the lighter mass crank bike down more and it would take longer to recover. I presume the stored energy in the rotating flywheel mass helps to make the engine less responsive to those momentary inputs (just as with a heavy flywheel weight on a classic trials bike).

cheers,
Michael

[F5 Dave]

So same thing as clutch start. Heavy resists slowing down.
Doesn't answer why it would help overrev which as Frits points out is speeding up, all while power is falling.

I've spent most of my 2 stroke tuning years working with "It just does" as it brought quick results, followed by lots of experiments to learn and gain more "it just doeses at least on this engine" junior explanations followed.

[TZ350]

how should I go about calculating the tm balance factor?
Crankshaft balancing has been covered here some time ago. I'm sorry I can't point you to the exact page, but maybe you can find it by searching for the pictures I used:

336426 336425 336424

Some of the earlier posts ......


BF=(A/B)*100

A is the flywheel counter balance weight and B is the reciprocating mass (weight).

238097

The lower half of the rod and big end can be considered rotating mass and disregarded and the upper half and little end reciprocating mass, along with the complete piston assembly.

Ballance Factor in % is A/B * 100 and is the amount of reciprocating mass counter balanced by the flywheel counter balance weight.

There is a lot more practical info in the original posts if you click through to them.


These Posts started 17th June on Page 70.

Looking at the connecting rod it is easy to see that the Big End goes round and round and is all rotating mass. And the little end goes up and down and is all reciprocating mass.



Pic-1 Thomas showing of the balancing jig he lashed up in about 10mins.

Pic-2 The tubes act like a knife edges and are a very friction-less surface for the crank to roll on. The tubes are the key to the whole thing.

Try this search :- crank ballancing site:https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner/

336452

[Muhr]

336423
Like this one, Muhr? There are a lot of these around, and they're supposed to be competition engines :p


Not so smart design with a smart solution! fun with easy-to-use solutions that are not easy to think of

One might suspect a photo editing:D

[wobbly]

F5 Dave - you are correct about the clutch.
When testing the BSL500 at Sepang we did a side by side test.One bike had a new AP Carbon/Carbon clutch that represented around a 40% reduction in inertia
over the normal Yamaha superbike sintered steel version.
It cost around $10,000 NZD so we were keen to prove its worth.
On the data and visually easy to see, was that from the apex of the last left hander onto the straight the AP bike pulled almost a bike length per gear change to the finish line.
The only issue was that it proved impossible for the riders to modulate the slip effectively to get consistent starts.

[philou]

336447336448336449

[Grumph]

F5 Dave - you are correct about the clutch.
When testing the BSL500 at Sepang we did a side by side test.One bike had a new AP Carbon/Carbon clutch that represented around a 40% reduction in inertia
over the normal Yamaha superbike sintered steel version.
It cost around $10,000 NZD so we were keen to prove its worth.
On the data and visually easy to see, was that from the apex of the last left hander onto the straight the AP bike pulled almost a bike length per gear change to the finish line.
The only issue was that it proved impossible for the riders to modulate the slip effectively to get consistent starts.

When the car hillclimb crowd started using carbon clutches they found the same thing. Solved by putting a front wheel up against a barrier and slipping the clutch until it was hot. Even doing this every run, wear over a season was not measurable.

[F5 Dave]

3364478336449
Great stuff, I hope. But I was born on a remote island in the Pacific and it never occurrd to me that there would be any benefit to learning another language being that Europe was 60 million miles away.
Or something like that. French class I only learnt how to ask the time. Not how to understand the answer.

[Peter1962]

Great stuff, I hope. But I was born on a remote island in the Pacific and it never occurrd to me that there would be any benefit to learning another language being that Europe was 60 million miles away.
Or something like that. French class I only learnt how to ask the time. Not how to understand the answer.

I don't think that your French class would be of any help in translating a text that was written in Italian. :msn-wink:

[husaberg]

I cant read French or Italian
but looking at the pic in the article I see they have still missed the point.
high inertia cranks are not all about it being heavy persay, its about concentrating the weight near the edge, so it maintains momentum, with a minimum of weight needed
but more importantly I believe it allows the inner part of the crankwheels and the conrod not to be shrouded.
Have a look at the Thiel era Aprilia pics and see there is no porkchoping no conrod cut outs.
Just narrow flat clean surfaces. Well that's what I think anyway.
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=336448&d=1524896042
Below Thiel era Aprilia no shielding of rod
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=336439&d=1438074106

I remember the first time I rode a B33 BSA whist they might not have accelerated that fast with their big heavy crankshafts, but what stuck with me was they didn't seem to slow down at all either when you rolled off the throttle.

[Muhr]

http://www.physicsclassroom.com/class/newtlaws/Lesson-1/Inertia-and-Mass

http://www.calctool.org/CALC/phys/newtonian/centrifugal

[Frits Overmars]

How'd you secure the overlay tube ? Shrink and spotweld ?Glued it. It was a carbon tube; it didn't like being spotwelded.

[Grumph]

Glued it. It was a carbon tube; it didn't like being spotwelded.

See, that's a degree of sophistication I wasn't expecting...My only experience with carbon as an engine compoment was a very short lived experiment with hand made carbon fiber pushrods....Epic fail.
Thanks Frits

[TZ350]

I believe it allows the inner part of the crankwheels and the conrod not to be shrouded.
Have a look at the Thiel era Aprilia pics and see there is no porkchoping no conrod cut outs.
Just narrow flat clean surfaces. Well that's what I think anyway.

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=336439&d=1438074106

Team ESE efforts to emulate the un shrouding of the big end like an Aprillia crank.

336455 336456

[philou]

The document speaks of a variable balancing crankshaft

In the different holes, it is possible to insert aluminum, steel, tungsten, ... to easily vary the balancing.

By the calculation have chosen a balancing factor, and by test of the motor, can change the factor by changing the inserts

[TZ350]

By the calculation have chosen a balancing factor, and by test of the motor, can change the factor by changing the inserts

Thanks Philou, calculate then test, it is the only practical way to arrive at a balance factor that works properly with any engine, frame, suspension combination. Great to see the crank.

[wobbly]

The pic that has been identified as one of Jans Aprilias,shows the lengths gone to to increase inertia dramatically.
Where I have marked X, these two inserts appear to be identical to the others, but contribute nothing to balance .
If anything they look to be above the centerline, so in effect are partially unbalancing the assembly,but as they are opposite each other all they
are doing is increasing mass and inertia.
My take on the effect is two fold.
Firstly,the high inertia would reduce the rotational speed drop off when speedshifting at WOT using ignition cut.
Secondly the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent.
No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational
speed = more open time with the same static timings.

[jbiplane]

Couple of videos of 294cc boxer engine with carburetor and new type of exhaust

https://www.youtube.com/watch?v=t5EHxyTq3WM

https://www.youtube.com/watch?v=-uSf-vut9KY

[husaberg]

The pic that has been identified as one of Jans Aprilias,shows the lengths gone to to increase inertia dramatically.
Where I have marked X, these two inserts appear to be identical to the others, but contribute nothing to balance .
If anything they look to be above the centerline, so in effect are partially unbalancing the assembly,but as they are opposite each other all they
are doing is increasing mass and inertia.
My take on the effect is two fold.
Firstly,the high inertia would reduce the rotational speed drop off when speedshifting at WOT using ignition cut.
Secondly the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent.
No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational
speed = more open time with the same static timings.

I only identified it as "Jans era" I have long forgotten where I found it. or if its from a twin or a single but I posted it for its clean inside profile. (Edit looking through the albulm it seems to be a single judging by the balance shaft drive gear)
336464336465

I think the twins would be balanced to a higher balance factor maybe even 100% this could be one of these. Okay its not but here are some anyway.
336466
I think the added weight allows the crank to be made cleaner on the insides whist maintaining the inertia that a porkchop design would have had.


Frits has posted and commented previously on later post Jan RSA cranks where they packed the insides to increase primary compression and noted they were never as fast.
This I think is one of them. I think it came from the frits file? Maybe Frits or Jan would like to comment seeing as they know the answers.;)
336467
I believe aprilia may have later also changed the balance shaft design back to a pork chop design.

I do know this is a RSA125 crankshaft. and if you look closely its porkchoped.
336462336463


Whats your take on my theory on the progressive loss of over rev as the Honda NSR500 went from four even spaced 90 degrees firing (first NSR500's spencer era)
To 180 like a twin(ie two up like a Yamaha yzr500 commonly referred to as the screamer)
To big bang firing all cylinders within 68 degrees more like a single.
Because it seems even if one accounts for engine spec difference, it seems anecdotally at least, that each time they made changes to make the firing less evenly and closer spaced, they actually lost over rev potential.

[jamathi]

The pic that has been identified as one of Jans Aprilias,shows the lengths gone to to increase inertia dramatically.
Where I have marked X, these two inserts appear to be identical to the others, but contribute nothing to balance .
If anything they look to be above the centerline, so in effect are partially unbalancing the assembly,but as they are opposite each other all they
are doing is increasing mass and inertia.
My take on the effect is two fold.
Firstly,the high inertia would reduce the rotational speed drop off when speedshifting at WOT using ignition cut.
Secondly the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent.
No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational
speed = more open time with the same static timings.

This kind of thing was tested on-track.
It seemed to give more traction.

[philou]

Great stuff, I hope. But I was born on a remote island in the Pacific and it never occurrd to me that there would be any benefit to learning another language being that Europe was 60 million miles away.
Or something like that. French class I only learnt how to ask the time. Not how to understand the answer.

for me the most difficult messages to translate are those of wobbly :eek:


Thanks Philou, calculate then test, it is the only practical way to arrive at a balance factor that works properly with any engine, frame, suspension combination. Great to see the crank.

The idea of the manufacturer and sell a crankshaft with holes and inserts with to do what we want

The manufacturer also indicates :

"These interchangeable inserts have the possibility of varying the balancing at will according to the available alternative mass; or depending on the type of return the preparer wants to get.

The system of these 3 holes allows in practice to have more settings on crankshafts to develop the engine with a so-called pre-established delivery or at least to obtain a certain supply.
For example, dropping the crankshaft forward as the direction of rotation of the engine tends to favor high rotational speeds, while dropping the shaft in the opposite direction of rotation, like most engine shafts. original series from scooters low-speed delivery is favored, improving the initial thrust."

[TZ350]

.
Looks to be very useful and a clever idea, top quality.

[TZ350]

Couple of videos of 294cc boxer engine with carburetor and new type of exhaust

:2thumbsup ..... great to hear it running, sounds very quiet.

[Greg85]

Thanks everyone for all the very interesting info about crankshaft balancing 👍👍

[husaberg]

Thanks everyone for all the very interesting info about crankshaft balancing ����

I found this below on the net and it saved me having to scan it again.
whilst most of this was written perhaps 60 plus years ago some of the tricks are still relevant in the book.

336469
the whole book is scanned here.
http://tuningforspeed.com/files/Tuning_for_Speed.pdf

[philou]

balancing factor 60% seems used for riders comfort

I find 45 to 50% on crankshaft "racing" (not balancing shaft) more vibration but less crankshaft stress ?

I am curious to anticipate or retard the balancing mass as proposed by the ialien

[Muhr]

two-wheeled vehicles tend to handle horizontal forces better then vertical. where off the cylinder position is crucial for seting up a balance factor.

[philou]

horizontal force less tiring for the pilot.

Vertical force = jackhammer

[Frits Overmars]

the high inertia would reduce the in cycle speed variation around BDC, where gas pressure above the piston is non existent. No force = no acceleration = less instantaneous rpm.
But this is counter intuitive , because if you allow the crank to slow down more , around BDC , then this in effect will increase the STA of the transfers as the lower rotational speed = more open time with the same static timings.No force = no acceleration; right. But as the piston is approaching BDC there is as lot of force, not from the non-existent gas pressure, but from all the reciprocating parts that try to keep moving towards the centre of the earth.
Before BDC that force is accelerating the crankshaft rpm; after BDC it is slowing down the crankshaft rpm. So what is the nett gain in transfer time.area?




I think the twins would be balanced to a higher balance factor maybe even 100%. this could be one of these.Are you referring to your first or your second picture Husa? Your first picture does not show an Aprilia V-twin (or W-twin if you like) crank; your second picture does.
The inserts give the twin-cranks a distinct asymmetrical appearance because the resultant of the inserts' forces must be at a 45° angle to the crankpin position.
336470336471



I think the added weight allows the crank to be made cleaner on the insides whist maintaining the inertia that a porkchop design would have had.Correct.
Frits has posted and commented previously on later post-Jan RSA cranks where they packed the insides to increase primary compression and noted they were never as fast.Yes, after Jan retired, some geniuses in the racing department seized the opportunity to 'correct Jan's mistakes'. They packed the insides and then wondered why a 2008-RSA was slower than a 2006-RSA...



I believe aprilia may have later also changed the balance shaft design back to a pork chop design.The original left-side balance mass was a full aluminium disk with mallory inserts. The geniuses changed it into a triangle, saving a tiny bit of weight and increasing its air windage losses (luckily the left-side balance mass did not run in oil).
336472 336473

[husaberg]

No force = no acceleration; right. But as the piston is approaching BDC there is as lot of force, not from the non-existent gas pressure, but from all the reciprocating parts that try to keep moving towards the centre of the earth.
Before BDC that force is accelerating the crankshaft rpm; after BDC it is slowing down the crankshaft rpm. So what is the nett gain in transfer time.area?


Are you referring to your first or your second picture Husa? Your first picture does not show an Aprilia V-twin (or W-twin if you like) crank; your second picture does.
The inserts give the twin-cranks a distinct asymmetrical appearance because the resultant of the inserts' forces must be at a 45° angle to the crankpin position.
336470336471


Correct.Yes, after Jan retired, some geniuses in the racing department seized the opportunity to 'correct Jan's mistakes'. They packed the insides and then wondered why a 2008-RSA was slower than a 2006-RSA...


The original left-side balance mass was a full aluminium disk with mallory inserts. The geniuses changed it into a triangle, saving a tiny bit of weight and increasing its air windage losses (luckily the left-side balance mass did not run in oil).
336472 336473
Yes I was referring to the first pic of the crankshaft with the original balancer next to it.
I identified that as being RSW125 by the balancer when I went back through my album
I have add some brackets to my original post to clarify it up a bit. Thanks for your response.
So all the pics I posted (below)with the non clean inside of the crankshaft are post Jan RSA modifications.


This I think is one of them (RSA125). I think it came from the frits file? Maybe Frits or Jan would like to comment seeing as they know the answers.;)
336467


I do know this is a RSA125 crankshaft. and if you look closely its porkchoped.
336462336463

[Frits Overmars]

So all the pics I posted (below)with the non clean inside of the crankshaft are post Jan RSA modifications.Yep .

[Muhr]

two-wheeled vehicles tend to handle horizontal forces better then vertical. where off the cylinder position is crucial for seting up a balance factor.

Somthing else that may be worth considering is Critical Speed that you want to avoid in your rpm range.(Critical speed occurs when the crankshaft begins to flex)

[lodgernz]

Thanks Wobbly, Frits, Neels and others for your comments regarding exhaust duct length.
The general feeling seems to be that, for oversquare engines, a duct volume about equal to the cylinder capacity would be a good starting point.

The established rule for nice triple port or T-port engines is "CSA reducing from port window to 75% of window CSA over 1.5 * bore, then transitioning out to 100% for another 0.5 * bore".

It seems clear from the discussion that the measurements based on the bore probably aren't valid for oversquare cylinders. So the questions are, for my POS oversquare engine:

A. Should I still aim for a 3:1 split for the lengths of the two sections of the duct?
and
B. Should I still aim for the 75% & 100% end CSA for those sections?

I realise nobody knows the answer to these, but I'd appreciate any intuitive opinions.

One of the problems with oversquare engines is that the exhaust window area is significantly less than that of a square engine, since vertical real estate is far more valuable than circumferential, and is even worse if the port is a single or T port. With a small port window area, a duct with the cylinder capacity as suggested, may result in an impossibly long duct.

For example, my 53 x 44 97cc T-port cylinder has a total window area of only 600mm2, allowing for radial and axial duct angles, and I can't make it much bigger without breaking through the water jacket.
If I follow the accepted rule of thumb, but not relating the duct lengths to the bore, the suggested duct for this engine would start with a CSA of 600mm2 and reduce to 75% of this (450mm2) over a length of 3x, then have a transition piece of length x, ending with a round outlet with a diameter of 27.6mm (CSA back to 100% or 600mm2). A total length of 4x.

For this construct to have a volume of 97cc, the total duct length of 4x would have to be around 183mm. Completely impractical of course, hence my questions.

[tdc211]

Thanks Wobbly, Frits, Neels and others for your comments regarding exhaust duct length.
The general feeling seems to be that, for oversquare engines, a duct volume about equal to the cylinder capacity would be a good starting point.

The established rule for nice triple port or T-port engines is "CSA reducing from port window to 75% of window CSA over 1.5 * bore, then transitioning out to 100% for another 0.5 * bore".

It seems clear from the discussion that the measurements based on the bore probably aren't valid for oversquare cylinders. So the questions are, for my POS oversquare engine:

A. Should I still aim for a 3:1 split for the lengths of the two sections of the duct?
and
B. Should I still aim for the 75% & 100% end CSA for those sections?

I realise nobody knows the answer to these, but I'd appreciate any intuitive opinions.

One of the problems with oversquare engines is that the exhaust window area is significantly less than that of a square engine, since vertical real estate is far more valuable than circumferential, and is even worse if the port is a single or T port. With a small port window area, a duct with the cylinder capacity as suggested, may result in an impossibly long duct.

For example, my 53 x 44 97cc T-port cylinder has a total window area of only 600mm2, allowing for radial and axial duct angles, and I can't make it much bigger without breaking through the water jacket.
If I follow the accepted rule of thumb, but not relating the duct lengths to the bore, the suggested duct for this engine would start with a CSA of 600mm2 and reduce to 75% of this (450mm2) over a length of 3x, then have a transition piece of length x, ending with a round outlet with a diameter of 27.6mm (CSA back to 100% or 600mm2). A total length of 4x.

For this construct to have a volume of 97cc, the total duct length of 4x would have to be around 183mm. Completely impractical of course, hence my questions.

If i where you. I would just put length at 50-60mm long
And 75%. At exit
Build a pipe and get delivery,traping,charging decent in sim and put it on the dyno and see.

[wobbly]

I would for sure use the 75% and 100% area guidelines.
But try this as a thought process.
The guideline lengths relied on 125cc square engines with really high bmep.
So modify the duct length total of 2X Bore by your actual numbers.
First the bmep.Say yours is 12Bar and the Aprlia is 15Bar,so we have 53X12/15 = 42.4.
Then we have the bore to stroke ratio 42.4 X45/53 = 36
So now assume your effective bore is 36
Times 1.5 = the 75% area position = 54 and the 100% position = 2X36 = 72
So this gives a slip on transition length of only 72-54= 18
Make this 22 long with the smallest CSA at say 50.
Seems reasonable to me,but the real proof is in the mach number at peak power of the 75% CSA = 0.8
Do the lengths come close to achievable ?

[SwePatrick]

Duct volume as a measiring tool must be very inexact?

To put it in extreme, if duct is 200mm long, do you still use the term?
I would say it is far more important to use area, and area at certain distances away from piston.

[Vannik]

I would say it is far more important to use area, and area at certain distances away from piston.

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.

[SwePatrick]

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.

Same problem there, if port in head is so long that it is the complete runner, still important?

If focusing on the 'correct' volume without having the areas correct one can end up with a really oddshaped runner if not knowing better.
One need to know where to put the smallest area in the runner, and one need to know how hard one can taper the runner.
One need to know how hard the runners turns in an another direction, and know how tho shape the runner to maintain the airspeed/flow.
Just giving a value of volume is leaving a lot of room for misunderstanding.

[Muhr]

images from the caster!:2thumbsup

For once, I have a little luck:lol:, the casting was successful.

[tdc211]

336491336492

I think a pic of header and flange is worth more than words,
I should say the end of the extunel, which is what you are looking at ,on ktms un boltable face

[wobbly]

But I have never seen a duct in a competition type engine that is too long.
Plenty that are way too short - especially those that have a female header plug in as part of the cylinder.
Having the really good guide of 75% smallest and 100% again at the header makes choosing the areas simple, and they work.
I would be interested to see the result of using both bmep and bore/stroke shortening multipliers in a severely oversquare project.
In the example I did ,the lengths seem quite usable , if the actual cylinder is a bit longer then I doubt it would have much negative effect.

[SwePatrick]

For once, I have a little luck:lol:, the casting was successful.

Nice!
Never had a doubt.

That company you chose to cast is one of the best.

[teriks]

For once, I have a little luck:lol:, the casting was successful.
Im impressed, would for sure love to see that in action once finished!

[Muhr]

Nice!
Never had a doubt.

That company you chose to cast is one of the best.

The problem was that they did! :)


Im impressed, would for sure love to see that in action once finished!

Much of what I've done with the cylinder has been inspired from this page, not least the huge number of pictures and drawings Frits has uploaded, and discussions about both exhaust port bottom hight and water channels inside transfers, which I applied both. So I feel it would be my duty to upload results if there is interest.

Right now I am working on the intake and crank so it's a bit left until I can test.

[Vannik]

Couple of videos of 294cc boxer engine with carburetor and new type of exhaust

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

336498

[jbiplane]

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

336498
Hi Vannik

Can you try to simulate my engine with this king of exhaust and compare with my experimental data?
I can provide any information for this.

[peewee]

But I have never seen a duct in a competition type engine that is too long.
Plenty that are way too short - especially those that have a female header plug in as part of the cylinder.
Having the really good guide of 75% smallest and 100% again at the header makes choosing the areas simple, and they work.
I would be interested to see the result of using both bmep and bore/stroke shortening multipliers in a severely oversquare project.
In the example I did ,the lengths seem quite usable , if the actual cylinder is a bit longer then I doubt it would have much negative effect.

maybe i dont understand your terminology. exh passage is bore face to exh spigot exit , measure through the center ? header is first section of exh pipe that slips over the exh spigot ? and what is the 100% you refering to ?

[wobbly]

Guide for EngMod users collated by Neels.

[Matt@TYGA]

Hi chaps.

Fiddling with some combustion chamber shapes, and will try a few once I've decided on what to try.

Just thought that I'd throw this out there for the blokes that know more than me (which is lots of you).

The pics attached have basically the same volume chamber. The differences being the height of the chamber (also spark position) relative to the top of the piston, and the size of the radius that comes off the squish.

On the left, the rad is tangent to a vertical line drawn. On the right, as you can see, it isn't tangent and the chamber more resembles a hemi than a bathtub.

Both have the same squish clearance (parallel to piston), and same squish area ratio

So given this, what do you guys think would be the difference, and more importantly, why?

Thanks,

Matt.

[Muhr]

For once, I have a little luck:lol:, the casting was successful.

Here are some more pictures on the cylinder. finish is okay, took some control measures and the deviation is basically non-existent.
would be fun if someone has 3d printed a cylinder so we can compare.

[dutchpower]

Looks promising Muhr

What about the cost

[Muhr]

Looks promising Muhr

What about the cost

It costed just under 900 euros, but one should know that the one I chose to do was considered to be very complicated piece to manufacture because of the many small channels I designed

[wobbly]

Jan tested both designs on the Aprilia and opted for the bathtub.
I have done direct back to back tests on TM kart engines and the bathtub is ( only slightly ) superior in that application as well.
That engine has a conical piston shape ( the squish angle continues to almost a point ) at 4* so dropping the plug has less effect.
If I was permitted by the regs I would use a toroid and bring the plug down even closer.
The logic I have for this is that if you draw a line parallel to the squish, this will be the direction that the turbulent flow exiting the closing gap will enter the expanding bubble
of burning combustion.
This turbulence is, in effect , creating a situation exactly the same as advancing the ignition - the advancing flame front is sped up by the eddies created thru its volume.
Thus if the center of the bubble ( the spark gap ) is closer to a line exiting the squish, we get the maximum effect of the increase in burn speed.
Dropping the plug even further with a toroid has made more power, and suppressed deto in every case I have used it.
It works best on flat top pistons - but my opinion is that the best piston shape is an angled edge,its width = the squish,then a flat top.
Will be testing that soon.

[Matt@TYGA]

Thanks Wobbly.
I'll do another design to drop the plug a bit further and compare. Thankfully I don't have any regulations I need to stick to.
Regarding the EGT sensors you've previously mentioned, do you mind sharing the link again... Or I guess I could search for it. Another question is how to log the EGT vs rpm. I have a dynojet dyno but not sure if it's possible to link up the sensors to log the output. It's a pain trying to watch several things at once and then the EGT is only a guess as I'm not logging it. Logging it independently of the dyno software is also OK. No problem hooking up another lap top if that's what it takes.

Cheers

Matt.