ESE's works engine tuner

[wobbly]

Jan , it surprises me you said the Czech machine was not used at Aprilia. The Yamaha engineer who did the 2000 YZR250 winning bike ( named Suzan in ringlish ) said it was so good he could tell exactly what
power a cylinder would make without needing the dyno.
And Bud Askland when developing the KR3 cylinders said the Czech machine showed him how good the factory 250 cylinders were , but also he learned exactly what to change from viewing the in cylinder
scavenging patterns.
Ive only seen a couple of pictures of the thing , but not any results it produced.

[lodgernz]

I need to drill a couple of oil holes in my piston to lubricate the ex port divider.
Can someone please advise where vertically to drill them? Like just below the ring land or further down for the top one?

[wobbly]

15 and 35 down from timing edge on 54.5 stroke

[lodgernz]

15 and 35 down from timing edge on 54.5 stroke

Perfect. Thank you Wobbly.

[skako]

Comparison of simulations
In the simulation program that I put together according to the first book by Prof. Blair, I made hundreds of simulations presented in the form of graphs.
Despite all the limitations and shortcomings, the graphs gave me a relatively good and quick qualitative insight into the simulation results.
I was interested in settings that are not common in engine construction.
These simulations showed that the properties of the output result are affected to some extent by the length of the transfer.
For a more accurate result, I now use EngMod2. I set up an air-cooled model with a target BMEP of 15 bar, with the STA timings set accordingly.
Through several steps of Deto-Analysis, I set the ignition times so that there are no detonations. Thanks again Wobbly for the warning and helpful advice.
I have limited the model which in some dimensions resembles cylinders that already exist. I was interested in how two different scavenging models would behave.
In this simulated model, the RSW scavenging model gives approx. 1.2% more peak power compared to the LoopSaw model. In the other modes of operation, the results are almost the same.
Despite the targeted high BMEP and high STA, the BMEP result is approx. 20% lower than required.
I have shown part of the other data on the additionally edited EngMod2 output graph.
Maybe these graphs will help someone and lead them to additional thinking about engine construction.

[wobbly]

I have a hundred questions on the methodology for this.
Is this a Rotary valve engine , is the case ratio for the long or short duct , what was the fuel , what was the CE , was the Combustion file derived from a Turbulent model run that had been imported,
how clever is the pipe design etc etc.
The very best RSA sim I can construct is short of the actual crank power expected , as there is no way of modelling the correct Ex port timing that takes into account the actual large port Cd increase due to the
timing edge radius Jan added to enable any performance from the sub optimal pipe design given to him.
Thus that sim has a sub optimal Blowdown STA coupled to the sub optimal pipe , and as such cannot accurately replicate reality.
In short im struggling to gain any worthwhile insights from your data due to a severe lack of supporting info.

[skako]

I have a hundred questions on the methodology for this.
Is this a Rotary valve engine , is the case ratio for the long or short duct , what was the fuel , what was the CE , was the Combustion file derived from a Turbulent model run that had been imported,
how clever is the pipe design etc etc.
The very best RSA sim I can construct is short of the actual crank power expected , as there is no way of modelling the correct Ex port timing that takes into account the actual large port Cd increase due to the
timing edge radius Jan added to enable any performance from the sub optimal pipe design given to him.
Thus that sim has a sub optimal Blowdown STA coupled to the sub optimal pipe , and as such cannot accurately replicate reality.
In short im struggling to gain any worthwhile insights from your data due to a severe lack of supporting info.

The model is piston port inlet, transfers are for long channel type, fuel is Unleaded 95, Comb.Eff. 0.95, AFR 12, combustion file imported from turbulent model.
CE, DR, Purity, graph attached. Since I'm new to using this sim, I might be doing something wrong.
I appreciate your comments, please tell me which file you need and I will deliver it to you, no problem.

[wobbly]

DM sent with email for your .pack file , but just quickly having a CE of 0.95 is impossible with pump fuel as is running 12:1 A/F

[p12palof]

Good morning from Spain, friends!!! I have reading this forum from many years and today is the time to make many tuning questions. Thanks for all the knowledge sharing here

One of my bikes is a tuned Honda CR500 '94:
-Ported cylinder
-Billet Cool head from USA
-VForce 2 reed cage
-HPI programmable ignition.
-41 Keihin PWK from Sudco
-CPI sand pipe (measurements in the image below)

I want to share the basic data of this engine:


















With all this things the real rwhp curve and the EngMod2t simulation are shown below





You can see the extrange dip in the curve around 8200 rpm. The same effect can be observed in the 2:00 minute in this bike from Kaplan America with similar tuning... My question is about the general geometry in this "drag" pipe and how do you improve this engine? I am not discard build a new custom pipe but I am afraid about the harming effect in all the curves presents in a MX exhaust

[jonny quest]

P12, that diffuser is way too short.

[Wos]

P12paplof,

The stock cr 500 has a ridiculous head Design...squish gap nearly 3 mm...area 60 percent...

Thats what honda did to keep a 500 2 stroke rideable

In your dyno chart there is a powerdip short after 4000 where retard drops... in my opinion it drops to early...
Ignition timing at peak power is little to high...bad for max power and overev...better do 15 degree at peak and drop steeper after peak...



Change head to more modern values as you did...keep compression low and do your own ignition curve

Grüße Wolfgang

[wobbly]

Skako - way too much of your sim is completely wrong to take away any useable information from the results.
Here is a quick list of the issues.
First 15 Bar bmep @10800 = 18 Hp is basically impossible at that rpm in a 50cc piston port engine.
The 70% diffuser is way too long and a 2.1* header will never work.
A CE of 0.95 and a 12:1 A/F is impossible on 95 pump gas.
A 76% chordal Exhaust port with a flat timing edge is impossible = instant ring destruction.
The Intake is over 2X too long to get any useable tuning and has no end correction,
4* of ignition timing at peak power will never make any power.
Pipe wall temp is way too low.
MSV @ 28.7 M/s is way too low.

I could rework the whole thing but of course that is expensive and im already way too busy, even on holiday.

[flyonly]

Woobly

For max hp from a 50cc would it be reed or disc valve?


Sent from my iPhone using Tapatalk

[wobbly]

For a while there I thought the development of reeds was beginning to approach the power capability of a Rotary Valve,
But then Neil Hintz blew it all out of the water with is sliding Gibb concept.
This now makes the Rotary impossible to even get close to , without all the development needed to make 24/7 a reality.

[skako]

Wobbly, thanks for your comments. It will be a good guideline for me for changes in the new sim-model with bmep around 10 bar.