ESE's works engine tuner

[Flettner]

right click and go to open link

Thank you, somtimes I just wish I knew how to use a computer properly.

[F5 Dave]

Move to a tablet. I'm still wondering which finger to use to right click

[Haufen]

In my sketches the fingers may appear thin, but remember that they are curved in two planes, so they are quite stiff.
The actuators may be spring-loaded so that any unforeseen pressure peaks can push the fingers either up into their resesses, or all the way down, where they can rest on the transfer floors.
Think of it: a misfiring in the cylinder, for example because of a faulty ignition, may push the fingers down, so the misfiring will never reach the crankcase.

A friend and I once tried to use that principle to upgrade an old cylinder with an exhaust power valve. Unfortunately, it did not work out. Even the severely reinforced second version was destroyed within minutes. Of course, it took piston no2 and cylinder no2 with it. Fortunately, these cylinders were no special one off high BMEP racing parts but rather cheap and common. As the pressure in our application was about 4 to 5 times that of yours, I think there is a good chance for your fingers to work and last. But as your cylinder is a rare one off, a FEM simulation might be beneficial to get an idea about the safe side and the danger side.

[Lucas M]

Hello Guys (and maybe girls?),

At first, I want to say thank you for this epic thread. I spend the last few weeks reading this topic (short nights )
After reading this, there are not really big questions in my mind anymore. So I want to take the chance to show you some stuff out of my two stroke world. I´m 22 and I spend most of my free time with two stroke engines and racing. Here in Germany I take part in a 50ccm racing class. There are some restrictions like original main frame, air cooled and inlet port piston controlled.

At the moment I got 14 rwhp. Not too bad, but I think I know where I can gain maybe 1hp more. Datas are 26,5mm carburetor, bore 38mm stroke 44mm(like original for this engine), no programmable ignition timing, port timings for inlet 170°, transfer all 130° and main exhaust 190°.

There are just 2 questions left. Did someone already a test with filling the exhaust duct floor with a measurable result? This may be a good benefit for my engine. The one made by TZ350 was a little bit confusing?!
If you have a closer look in my diagram, you will see the small hump at the end of powerband. I took an already existing well working exhaust pipe from a scooter and lengthen the first part about 50mm, otherwise it would be too short. Unfortunately I think this wasn’t a good idea, where the small hump in the circle came from. What do you think guys? If I find the time, I will build a new pipe where I will lengthen all parts about the same amount and not only one part.

The other question is especially for Frits. Some earlier you wrote that you are also in a German speaking forum. Is this an open forum and I may can join to read some more stuff? Or did you wrote the most stuff already here?

Greetings, Lucas.

[mr bucketracer]

hi Lucas , thats a nice looking bike you have there , looks like it would go well to ..i like that seat

[136kg136ps]

I can't see any simple solution from the crankcase direction either.

Even with hydraulic or pneumatic direct actuation there would be lines to run not mention temp issues.Casting lines into the cylinder would be a real PITA too.How hard to seal the water jacket penetrations with bushing or grommet type seal,or are they unreachable?I don't imagine the actuator rod being over a mm or 2...more complicated I know.

[TZ350]

Did someone already a test with filling the exhaust duct floor with a measurable result? This may be a good benefit for my engine. The one made by TZ350 was a little bit confusing?!

Hi Lucas, your bike looks great, very professional.

The work on the exhaust port floor and the motor I tried it on was just all thrown together and in the end it proved to be not very suitable for proper long term testing.

But my impression from the initial results of the exhaust port floor experiment is good. And that it is a very beneficial thing to do. I will certainly be looking to use the concept in my future motors, I think there is power to be had there.

[senso]

I have the idea(or misconception) that directly bolting the carburettor to the cylinder will cause fuel frothing(foaming) in the fuel bowl that will tend to wreck havoc with the jetting, but its just a very random and fuzzy idea.

[wobbly]

Lucas - here are some guides that will let you see where to start.
The pipe lengths should be around 32% from piston to header end, and 66% from piston to diffuser end.
Having 50mm added to the header will for sure make the lengths all wrong.
The cylinder duct exit should be 75% of the total effective Ex port area, and the header start should be 100%, with an oval duct ( plus ears )
to promote Aux blowdown flow - with a smooth transition in the spigot from oval to round.
The rear wall of the Aux Ex is way too shallow, the exit radial angle should be to bore centre, with a pocket turn into the duct.
There is going to be a blowdown mismatch in the STA numbers at 190/130 , can you widen the B port without getting into the ring pins.
Also I can see that the B port is angled up sharply, this needs the roof ground flatter to say 10*, then epoxy the A port roof to 25*.
With no powervalve you should have the A port highest, then staggered down to B and C like a Honda RS.
Can you fit a programmable.
Having a 50cc make peak at 11500 means the pipe and ports are not matched, to use the rev potential of the little engines stroke.

[136kg136ps]

Lucas,starting at the beginning of this thread helped me to see how all the pieces come together,starting around page 250 Wobbly starts giving very detailed guides to inlet,port,timing and exhaust parameters.When Frits joined the party it became even more in depth and as people have joined in this has become the best 2 stroke build thread anywhere.I tried to cut and paste our esteemed teachers words only and it just doesn't give enough context.I would suggest starting early on and see if your questions have been addressed already not just by Frits and Wobbly but all the others who post their results using this new information.We are getting a free education.

Getting a direct answer is not nearly as good as understanding why that answer is correct.Welcome.

[Grumph]

At some point someone should sort and edit this thread into subsections - eg, Aprilia RSA, TZee's work, direct questions and answers from Wob..Where did I go wrong,Theoretical speculation...Just some of the sections it could use.
There would be a demand for it either in hard copy or on disc i'm sure. The search function is too limiting to leave it as is, even with Tzee's very useful 10 page summaries.

As has alredy been said, it's an education in current state of the art 2 stroke tuning....

[F5 Dave]

I'm just surprised you can get 14hp at just 11500, that's an achievement in itself.

[peewee]

could any of you experienced alloy welders offer some advice and let me know if its a good idea . what im thinking here is get a piece of solid round bar (copper, brass or something else ?) and basically use it as a plug so i can weld over the top of it and make the aux tunell . then pull the plug out and finish grinding the fine details of the tunell. i havent a clue about welding but i have 3 junk cylinders to practice on. was thinking to use a spool gun ( 4043 wire ??) since that might be easiest welding method for a novice. i meen how hard can it be to blob some weld on there . . aint like it has to look real good.

i have some alloy pipe on the way. i can cut in half horizontally for the outer bubble of the aux tunell and weld it in place

[Flettner]

could any of you experienced alloy welders offer some advice and let me know if its a good idea . what im thinking here is get a piece of solid round bar (copper, brass or something else ?) and basically use it as a plug so i can weld over the top of it and make the aux tunell . then pull the plug out and finish grinding the fine details of the tunell. i havent a clue about welding but i have 3 junk cylinders to practice on. was thinking to use a spool gun ( 4043 wire ??) since that might be easiest welding method for a novice. i meen how hard can it be to blob some weld on there . . aint like it has to look real good.

i have some alloy pipe on the way. i can cut in half horizontally for the outer bubble of the aux tunell and weld it in place

Out of interest in the past I've used CO2 core sand ( for casting ) to stuff up inside a trasfer port that did not cast properly ( a short ), set the sand, scrape it down to the depth required then weld over it. The result is a bit like casting alloy over the sand anyway, finish is the same as a casting would be. After welding the sand will be broken out of the port like normal.
May be of some use?

[wobbly]

Spool welding alloy is a real art in itself, alot harder than tig - I have been playing with using alloy repair stick welding to get inside Ex ducts.
So far it seems to work real well as the sticks are only 3mm diameter.
By holding the work at an angle so the flux runs away from the pool you can build up very easily but it needs
alot of heat and moving quickly to keep the weld free of porosity.
Having said that it is easy to grind the built up area, and if there is a hole, its just as easy to zap a blob over the top of it.

Re the 50cc power - Turning 14 RWHP into crank add 12% = 16 @ 11500.
BMEP = 12.4 Bar
To use the 50cc short stroke but still keep good powerband width, move the same BMEP up to 13500 and you get 18.7 crank Hp.
Nothing hard about doing that if all the STA numbers and components add up with some synergy.