ESE's works engine tuner

[TZ350]

http://www.freepatentsonline.com/6691649.html

Free Patents Online is a bit of a gold mine of ideas, its worth a look at the Two Stroke stuff.

[Forgi]

It all depends upon the power you are wanting - or the power that the weakest link in the engine is capable of.
Yes, the best power bandwidth is to be had down at 190 Ex duration, but this is rarely used as no matter how you jig the ports, you are always looking for more blowdown when after good peak power.
But if the engine has shortcomings in other areas, and will never generate a bmep over say 150psi, then you dont need high timings with a 3 port, as its easy to
get the required blowdown STA.
Thus my comment about dropping the main port, and dropping the Aux even more.
With a radius on the A port top front corner, its then easy to get plenty of Aux blowdown STA.
But , if cutting the ports this way gives an excess of Blow STA, then simply drop the ports some more and get an even better powerband width.

When you drop the main port you get a wider rpm band of superposition wave reinforcement, and when you have plenty of separation between the main and aux timings,the mid power comes up even more.
Its the old story told 1000 times, low and wide is best, with the one caveat that the best combination with 3 ports is a 68% main, with the biggest Aux you can fit to get the blow STA needed.

Edit - the Pulse/SwissAoto design had two round magnets embedded at 180* in a crank wheel.
Each one had reverse polarity, ie one was S the other N facing out.
The trigger saw this as two distinct signals and the ECU was able to determine LH and RH cylinder pairs for correct ignition sequencing.

@ Frits: I'm sorry that you don't have the article in english! Pretty sure that the article is older than me! :-)

@ Wobbly: Of course the goal is to get the best power which is determined somehow by the gear ratio.

I suppose you know the original 70cc simson cylinder which isn't a tuning-friendly thing. :-)



12,5K rpm, 0,0175 ex TA (195 ex timing), also convenient (Blair suggests) Blowdown, Tr and Inlet Time Area. If I modernise everything I have to decrease the ex timing with max. 2-3 degrees to keep the suggested ex TA value.
But regretfully it is hard to make such a perfect job by hand, as the bore 45 is too small and every single decimal mm counts!

So according to you if I modernise everything and I resolve somehow that at 185 degrees the TA (and of course ex, blowdown, tr) will be the same as at 190 or at 195, then at 185 the system works better? I'm affraid Frits will not agree! :-)

If we have a small bore at 13K rpm, we can get a convenient TA if our exhaust port timing is low enough.
This way in case of 25 (suzuki rk67) or 50cc 180, max 190 degrees are enough. But of course in case of 125cc if we have 195-200 is still hard to make a big blowdown and STA.

[Muciek]

You should see what guys in Poland make with those cylinders http://bikepics.com/members/hopit/projekt2013/ http://bikepics.com/members/nightfire007/p5/ http://bikepics.com/members/chylo00/p7/ http://bikepics.com/members/chylo00/p13/ http://bikepics.com/members/chylo00/p45/ http://bikepics.com/members/przemas2...?i=2348005&s=0 70cc 77cc 83cc and other They use exhuast ports that are 23mm from TDC for 10000 to 11000 rpm.

[wobbly]

The real point I was making is that lower and wider is better - assuming you end up with the STAs matched to the required performance.
Case in point is 125cc TM kart race engines, that make 44Hp at the sprocket, on my dyno, with a 30mm carb.
The real factory tuned engines have around 196* Ex duration and as delivered will rev to around 14300.
The engine i built that has just won our National Champs, has 194* but the Aux are hugely deeper and wider, and the transfer stagger is reversed, to get extra room over the A port
This makes 46Hp and easily revs to 15,000, and in the process destroyed a real expensive,super secret, genuine factory World Cup winning engine.

BUT - I dont know that going from 190* down to 185 will be better, as any engine with only 190* in the first place could not make any serious power to begin with.

[RomeuPT]

Finally made it to the end.

Hi, I am Romeu, I am from Portugal, been reading this topic for the last three weaks, founded here a 2 stroke treasure, probably the most valuable one in the internet.

I have been on pit-lane and the information there is huge too, but this topic talks more about reed induction 125 race engines, many thanks to wobby.

While reading a great amount of questions surged in my mind. The more important is what follows:

Wobby when you talk about oval to round transition at the exhaust flange is using the aprilia exhaust duct exit shape type or it would be done on the oval Honda RS duct exit too?
I am confused, because using the oval duct exit of 41 lenght by 34 height from the honda RS to a 41 round exhaust flange and having to keep a kink on the roof and floor where is the space for the taper?
I hope you could understand my confusion, doesn't the taper exhaust flange from the aprilia goes from an oval 46,5 width duct exit to 41,5 exhaust flange, making it possible to be taper...?

TZ350, you have done a great job. One of the most interesting bucket projects I have seen.

Thanks everyone for this great great topic.

Regards
Romeu

[TZ350]

Finally made it to the end.

Hi RomeuPT, congratulations on reading the whole thread, marathon effort. I too have learned a lot from all the people who post on here.

[wobbly]

The most powerfull Honda type exhaust duct, for the T port, that I dyno developed for a customer in Belgium, was a 41 wide by 32 high oval at the flange face.
This went out to a 41mm header diameter via an oval to round transition.
The stepped transition, with simply a round 41mm spigot ID lost around 1.5 to 2 Hp comparred to the CNC lofted shape.
We have a slightly different situation with the 3 port Aprilia.
In this scenario we have the flow from the Aux ports, that we need to promote as much as possible - helping blowdown efficiency, and the Aprilia has the cutouts for these side ducts going all the way down to the header.
The Aprilia flange face still has steps, where the cylinder bolts up to the flange, and it is my gut feeling, that two things are in play here.
Firstly is that Jan Thiels philosophy was to reduce the duct volume as small as possible, consistent with the huge power being produced, and the result of this was high header entry velocity,along
with a higher Helmholtz resonance.
I simply dont know at this point if Aprilia R&D tried a CNC transition, with the flange matching the duct exit shape exactly, ie no steps,then exiting as a round shape into the header, as per the Honda example.
Frits or Jan, could elucidate on this idea, if they choose to, but my feeling is that more power could be had with the transition, BUT, I also believe that just maybe things change when you are up at 55Hp
from a 125.
If you believe the steps reduce reversion flow, more than they reduce exit flow, and thus make more power, maybe you are right - this for sure isnt the optimum case with a T port, but the Aprilia is SOTA and you simply cant argue with the results gained by Jan and the factory - even when a bunch of uninformed idiots changed things after he retired.

[cotswold]

I have been reading through this guys stuff and some of you may find it interesting (or most likely seen it already)

http://forums.everything2stroke.com/...ound-the-Shop?

[husaberg]

Hi Wax

Attachment 277120

I purchased some new GY6 125/150 CVT parts, because they are pretty cheap here and there are after market parts available for them. The parts come in plain brown box's without any of the naughty words that would define them as illegal for Moto4 (Bucket) racing.

I need an old crank half and reduction box input shaft for their splines. I plan on extending the shafts so they can be run in carrier brgs mounted in the engine plates.

As best as I can figure out the CVT has a range of 3.25:1 to 0.8:1 which is pretty much the same as the GP gear box. So all I would need is a 3:1 primary or final gear reduction ratio.

So the plan is to have on the right hand side of the engine, a 3:1 straight cut reduction gear set to a cross shaft to the front CVT sheave mounted on the left side (keeps the rotation direction correct that way).

And the front chain sprocket behind the rear CVT sheave. That should put the front chain sprocket in the right place relative to the swing arm. The front reduction gear set could be lubed between races with a squirt of chain grease, life expectance does not have to be great.

If you can find an old crank half and reduction box input shaft for a GY6 125-150 I would be very greatful.

http://www.ncy-motor.com.tw/product3...earch=&page=13
I doubt i came apon the right page (in this link)but pretty sure the shaft you want was there...no crankhalf but i guss Newmanz and co if you can't find SH


Thanks Frits does it sound plausible that the RSA could be bigger (I won't hold you too it you are most patient with me already)
I am not sure you have mentioned where you currently are working? if thats not to intrusive

Thanks Husa I remember it now, $8 USD each from memory.

Okay thanks to Yow i found a CVT it is for a 2 stroke 125 and i was thinking cool going from 10 wheels to 17 plus 4000rpm extra would make it still be ok.

Well er not so much....
Ii hadn't factored in my final drive reduction.
Using Berts gear spreadsheet it would only do about 100kph (don't worry about 2nd to 5th i just put some ratios in there to fill the gaps.

The standard scooter drive reduction is huge.(attached)
Like TZ something around 3.5 is what i need.
I are beginning to think maybe it is a bridge too far.
Once i get a look at the Lead engine i guess we will see if there is a simpler solution.
I really like the idea of a CVT with a custom disk crankcase and a Aprilia inspired 100cc.

[RomeuPT]

The most powerfull Honda type exhaust duct, for the T port, that I dyno developed for a customer in Belgium, was a 41 wide by 32 high oval at the flange face.
This went out to a 41mm header diameter via an oval to round transition.
The stepped transition, with simply a round 41mm spigot ID lost around 1.5 to 2 Hp comparred to the CNC lofted shape.
We have a slightly different situation with the 3 port Aprilia.
In this scenario we have the flow from the Aux ports, that we need to promote as much as possible - helping blowdown efficiency, and the Aprilia has the cutouts for these side ducts going all the way down to the header.
The Aprilia flange face still has steps, where the cylinder bolts up to the flange, and it is my gut feeling, that two things are in play here.
Firstly is that Jan Thiels philosophy was to reduce the duct volume as small as possible, consistent with the huge power being produced, and the result of this was high header entry velocity,along
with a higher Helmholtz resonance.
I simply dont know at this point if Aprilia R&D tried a CNC transition, with the flange matching the duct exit shape exactly, ie no steps,then exiting as a round shape into the header, as per the Honda example.
Frits or Jan, could elucidate on this idea, if they choose to, but my feeling is that more power could be had with the transition, BUT, I also believe that just maybe things change when you are up at 55Hp
from a 125.
If you believe the steps reduce reversion flow, more than they reduce exit flow, and thus make more power, maybe you are right - this for sure isnt the optimum case with a T port, but the Aprilia is SOTA and you simply cant argue with the results gained by Jan and the factory - even when a bunch of uninformed idiots changed things after he retired.

Now I understand. My confusion was about keeping the steeps, because aprilia's have them. Thanks.
Some years ago I have buyed one 89' Honda RS 125 cylinder, to fit in one NSR 125 engine. Before that it had one CRM 125 cylinder, actualy tuned it quite whell in area and timing (200º ex/ 133º transfer) and the exhaust duck exit was 37 round, I builded one 804mm lenght exhaust matching exacly the 37 duck exit, 118 belly, strong diffuser angles and 14º reflector cone with 193mm duration using Mota software. (I had the luck to do very good peak power not knowing half of what I know today).
Today with the honda RS cylinder slightly tuned, and having Honda Exhaust layouts from Honda and the one from frits I have now a more drivable bike, but the power after 12k is lower than with the CRM cylinder. Of course there are other variables, but

I notice certain Honda cylinders have different transfer rear angles, why is that?


Another small question I would really like to know, how much moment of inercia (kg·m²) would be needed for a dyno used to measure power from 80cc/100cc and 125's till 50 hp ?
Has I readed on this forum I think I will try a 40cm tube, filled with concrete.

Thanks

[Frits Overmars]

... how much moment of inercia (kg·m²) would be needed for a dyno used to measure power from 80cc/100cc and 125's till 50 hp ?

That is an unanswerable question, Romeu. It completely depends on the gearing.

I think I will try a 40cm tube, filled with concrete.

I think you are too young to kill yourself. Don't even think of filling a tube with whatever. You will need either a thick-walled steel tube filled with nothing, or a solid steel flywheel. Not even cast iron will be safe for this purpose.

[RomeuPT]

I think you are too young to kill yourself. Don't even think of filling a tube with whatever. You will need either a thick-walled steel tube filled with nothing, or a solid steel flywheel. Not even cast iron will be safe for this purpose.

I see what could happen.
A full steel rod is really expensive and hard to transport.
So I should use a steel tube, and have a flywhell inside some safe box in case of something went wrong?!

Thanks

[Flettner]

Fuel injection runs again, phone call today and all I could hear on the other end was the sound of a twostroke running. The YZ 250 EFI port injection lives, only took a couple of kicks! It is running on the F9 program so needs a little bit of tuning. Next trick is to hook up the power valve to the computer take control away from revs alone.

[Sketchy_Racer]

Another small question I would really like to know, how much moment of inercia (kg·m²) would be needed for a dyno used to measure power from 80cc/100cc and 125's till 50 hp ?
Has I readed on this forum I think I will try a 40cm tube, filled with concrete.

Thanks

You will need at a minimum 6kg-m^2 to have a reasonable run time with 50hp, but generally the more the better as the longer run lengths help show up weak spots in the motor. I have a small 2.2kg-m^2 dyno that is useful for up to 25hp but the run lengths get short (around 8 seconds)

As mentioned, you need either a solid bar of steel or a pipe with thick walls with end caps welded on. Just remember you are going to have to have the assembly dynamically balanced once finished.

http://wotid.com/dyno/content/view/16/35/

That is a good site for info.

[TZ350]

Fuel injection runs again, The YZ 250 EFI port injection lives.

Congratulations ... that makes it two, home brew, competition 2-Strokes running EFI that you have put together.