ESE's works engine tuner

[andreas]

As I said i'm not excactly sure why that engine made more power. And also as I said, I think it had a shared pipe with a y- section to the cylinders, so there is no need to have ducts from one cylinder to the other. If your idea works with separate pipes, I don't know.

[ceci]

As I said i'm not excactly sure why that engine made more power. And also as I said, I think it had a shared pipe with a y- section to the cylinders, so there is no need to have ducts from one cylinder to the other. If your idea works with separate pipes, I don't know.

sorry, I did not say anything that it is for separate pipes, also it can be controlled with a valve that activates or deactivates it.
With a little imagination we can dream of a Yamaha TZ250 type engine, powered by the 24/7 valve system, in addition to cross-feed "supercharging" through the exhaust, with a considerable increase in power.

[TZ350]

This is the work I would like to have done myself in my own shed if I was clever enough.....

[andreas]

[OopsClunkThud]

started a new thread for geeking out on the CFD details:

https://www.kiwibiker.co.nz/forums/s...-(CFD)-Q-amp-A

Thinking this will make it easier to track and find the boring data like gas properties and how to generate good mesh boundary layers, and then we can just post the results and exciting stuff here.

[TZ350]

More intriguing stuff from the Shed of Two Stroke Stuffing ......

[TZ350]

[F5 Dave]

Thanks for posting that Rob. Held 6" from my face my heartrate was going. I love 50s, even on long tracks.

[TZ350]

I love 50s, even on long tracks.

Yes, I am enjoying mine. RG50 in NF4 chassis with a few mods to make it a bit more comfy to ride. I have ridden it at Hampton Downs club track and Tokoroa. Came last every time....

[sniemisto]

Hello everybody,

I've been reading these super interesting topics here and in pit-lane. Thanks everybody for this great knowledge that is shared in here!
I'd like to introduce myself before posting anything else. I'm 32 years old guy from Finland and been diving inside 2-stroke tuning "rabbit hole" since I started tuning Derbi engine for Finnish moped endurance class. I'v been working as motorcycle mechanic 15 years, but mainly with 4-stroke street bikes.

Our endurance team has Derbi Senda DRD Pro with modified Athena power valve cylinder, original pneumatic PV replaced with electronic Aprilia Rave controlled by Ignitech unit.
I'm now planning new engine version and got new fresh Athena cylinder to avoid mistakes I've done with first one..
Been practicing with EngMod2t and playing with different variations. We have just built inertial dyno and that is starting to be finally set up smooth enough to fine tune simulation model to correspond.

Question:
There has been a lot of discussion about piston pin plugs and how it's benefit varies depending on porting, plug style, ...
I have still missed following point. Is gaining blowdown specific time area by extending auxliary exhaust ports over piston pin until cylinder center line making more gains than what is given away with unplugged pin hole? Yes, depends on many thing, but can we have some rule of thump in case of modern high performance engine?

With best regards,
-Sami-

[jamathi]

Hello everybody,

I've been reading these super interesting topics here and in pit-lane. Thanks everybody for this great knowledge that is shared in here!
I'd like to introduce myself before posting anything else. I'm 32 years old guy from Finland and been diving inside 2-stroke tuning "rabbit hole" since I started tuning Derbi engine for Finnish moped endurance class. I'v been working as motorcycle mechanic 15 years, but mainly with 4-stroke street bikes.

Our endurance team has Derbi Senda DRD Pro with modified Athena power valve cylinder, original pneumatic PV replaced with electronic Aprilia Rave controlled by Ignitech unit.
I'm now planning new engine version and got new fresh Athena cylinder to avoid mistakes I've done with first one..
Been practicing with EngMod2t and playing with different variations. We have just built inertial dyno and that is starting to be finally set up smooth enough to fine tune simulation model to correspond.

Question:
There has been a lot of discussion about piston pin plugs and how it's benefit varies depending on porting, plug style, ...
I have still missed following point. Is gaining blowdown specific time area by extending auxliary exhaust ports over piston pin until cylinder center line making more gains than what is given away with unplugged pin hole? Yes, depends on many thing, but can we have some rule of thump in case of modern high performance engine?

With best regards,
-Sami-

My answer is a definite YES!
At Aprilia we mostly tested with unplugged piston pins, as the plugged pins were too expensive.
Widening the auxiliar ports was done numberous times, and always gave more power!!!

[TZ350]

[sniemisto]

My answer is a definite YES!
At Aprilia we mostly tested with unplugged piston pins, as the plugged pins were too expensive.
Widening the auxiliar ports was done numberous times, and always gave more power!!!

Thanks Jan for the info!
Now I can start widening auxiliar ports and think about buying torlon bar later

Many sources was telling to avoid relieving to pin bores but that must be now considered as old fashion. That was also reason why I abandoned Athena pistons with relief around pin bore.


Sent from my iPhone using Tapatalk

[TZ350]

Ok. So its drag racing, but a two stroke drag racer. Great two stroke sound at WOT. And also if you pay attention to the technical talk and trip around the work shop you will pickup that its fuel injected. So the fastest 2T drag bike in the world is fuel injected.

[wobbly]

Widening the Aux ports to bore center does two things , increases Blowdown STA and increases port linking to the A Transfer.
You can reduce the effect of linking by making the Aux duct very shallow in depth at its rear wall next to bore center , and also grinding the port shape with alot of taper upwards from front to back.
This gives alot of area just as the port opens , with the max pressure differential , but reduces the linking time.
With capped pins the duct can have much less of a tangential exit angle on the rear , top , corner wall , with a nice sweeping pocket that improves flow and power.

Be carefull with using Frits idea of using Torlon inserts , that effectively blanks off the pin bore in the piston.
In the TM kart engines this reduced the access of lubrication from transfer flow into the piston bearing surface , and the pin ends turned blue.
Jan said that the Aprilia did the same , but I never wanted to find out if the pin bore became unreliable.
Making tophat CNC steel plugs and having them laser welded into stock pins is cheap , and relaible and just as effective power wise.
Maybe drilling a hole upward in the bottom of the piston pin boss would fix the issue , again I wasnt keen on destroying a motor if this was unreliable.