ESE's works engine tuner

[Drew]

Well, the shape is measured by is radius (or radii if it's plural ) but according to construction geometry the shape would be most accurately defined as a fillet.

A chamfer is a angled flat between two surfaces, as is a bevel.

So the edge these guys are talking about, is rounded? I thought they were just grinding and angle bit to teh top port edge. Why they do this is not exactly clear. But I might just have missed something, everyone else on here gets it all, so stuff gets only brief explanation for dumb builder types.

[Ocean1]

So the edge these guys are talking about, is rounded? I thought they were just grinding and angle bit to teh top port edge. Why they do this is not exactly clear. But I might just have missed something, everyone else on here gets it all, so stuff gets only brief explanation for dumb builder types.

Yes, a deliberately rounded edge to the top of the port at the cylinder wall.

Gas flows differently at different speeds, it'll follow the curve at some velocities, not at others. You can use this to effectively alter port timing over the rev range.

There's almost certainly more highly refined shapes that could match gas behaviour with that ideal timing even betterer, but I suspect you'd need a glass engine and high speed video to fine them without many thousands of build/test itterations.

[Drew]

Yes, a deliberately rounded edge to the top of the port at the cylinder wall.

Gas flows differently at different speeds, it'll follow the curve at some velocities, not at others. You can use this to effectively alter port timing over the rev range.

There's almost certainly more highly refined shapes that could match gas behaviour with that ideal timing even betterer, but I suspect you'd need a glass engine and high speed video to fine them without many thousands of build/test itterations.

Thanks mate. Much more clearerer.

[dinamik2t]

I have thought of it like so:



And here (I shot random photos and this 4.5 was better for explaining than the 3.5s)




The 3.5 number is the radius of the fillet applied.
What I haven't got clarified is whether at 196*/yellow-line there is already an on-bore-surface radius or it is horizontal.
In my pic at least, there are (exaggerated): the top corner radii ^ the top edge radius until 196* ^ the drawn red radius until 202*.

everyone else on here gets it all, so stuff gets only brief explanation for dumb builder types.

I think that it is out of respect for Frits' or Wob's or anybody's private life and free time, that we do not ask for further explanation when something is shared..
No need to be mean.

[cotswold]

Just a couple of photo's of the porting progress ( or lack of ) on my interim cylinder. A bit of a bomb site but I can usually find what I'm after.
There are some broken tooling bits that has slowed me down ( managed to break off a drill bit but got that out with a bit of help from the Dremel ) but I have a heavy duty replacement on it's way, hopefully get it early next week so I can get it finished.

[TZ350]

Looking good, I like the work bench for holding the cylinder, good idea ....

[dinamik2t]

I see a drill there! How that is working with the porting bits? I always though an electric drill would be too powerfull for hand use, but I am most curious to know your opinion ad experiences.


By the way, Wob.. an idea I had last night. Would it be possible to guide mr Neels of EngMod to create an Aprilia scavening pattern?? Since it's becoming quite popular these days.
Or (of cource) we should ask him ourselves, if it's something he can do without a specialist's help.

[Frits Overmars]

By the way, Wob.. an idea I had last night. Would it be possible to guide mr Neels of EngMod to create an Aprilia scavening pattern?? Since it's becoming quite popular these days. Or we should ask him ourselves, if it's something he can do without a specialist's help.

I know you're joking, but just in case: though Neels is a studied man, he also has plenty hands-on experience: "I am an engineer that does a bit of programming, not a programmer that does a bit of engineering." http://www.vannik.co.za/About.htm

[2T Institute]

The Aprilia scavenging is a case of the "whole is greater than the sum of the parts". Inputting the exact data from the drawings the outputs are nothing like the real thing.

[TZ350]

I see a drill there! How is that working out with the porting bits? I always thought an electric drill would be too powerfull for hand use, but I am most curious to know your opinion and experiences.

Yep, hand drills are good, you can do some quite good work with basic hand tools.

[dinamik2t]

I know you're joking

Then I shouldn't explain myself any further.
Actually that phrase was told to me via email in 2010. Wobbly already had his hands on his own aprilia-like cylinder, plus he knows the program, so he could inform Neels of dimensions, without (Neels) having to get an RSW/A cylinder himself. I would very much like to know(have?) the capabilities of an engineer of Neels' caliber, unfortunately I don't, so I asked politely. If I offended him, I can't do anything but apologize.

Yep, hand drills are good, you can do some quite good work with basic hand tools.

I tried once with emery paper rolls into the ex duct, but it was bumping all over the place!

[wobbly]

I think as Lozza alluded to, the issue with the Aprilia scavenging setup is that there are a huge number of details that collectively create a very synergistic whole.
Everything from the radius being discussed here of late to the just as important radius on the inner transfer duct /bore edge, all contribute.
The scavenging details are actual measurements,that usually are done in research labs, that is where the RS125 details came from.
I dont think that anyone has the measured data from an Aprilia cylinder - but maybe Neels could make an educated guess of the end result.
But in the overall scheme of us being able to predict the result of changes to a specific engine, I dont think many are capable of achieving anything like what resulted from 100 people working
for 10 years, as Frits has described the R&D dept at Aprilia.
Its seems to me that most simulations I do, overestimate the power achievable,thus indicating I am not able to meet the theoretical charging/scavenging efficiency numbers the sim is using.
Having an even better scavenging system would create even more unachievable power in the sim results.
The vast majority of my time is spent optimising the pipe and the intake geometry - the ports are easy, as the STA numbers direct you in the right direction all the time.
If you are short on blowdown the program tells you - you fix it, and get more power - simple,and you can be very sure that the mod you have just done would have worked on an engine , on the dyno, as well.

[dinamik2t]

Ok, that is more than understandable.

Wob, how do you usually handle the combustion efficiency factor?

[Brian d marge]

I think as Lozza alluded to, the issue with the Aprilia scavenging setup is that there are a huge number of details that collectively create a very synergistic whole.
Everything from the radius being discussed here of late to the just as important radius on the inner transfer duct /bore edge, all contribute.
The scavenging details are actual measurements,that usually are done in research labs, that is where the RS125 details came from.
I dont think that anyone has the measured data from an Aprilia cylinder - but maybe Neels could make an educated guess of the end result.
But in the overall scheme of us being able to predict the result of changes to a specific engine, I dont think many are capable of achieving anything like what resulted from 100 people working
for 10 years, as Frits has described the R&D dept at Aprilia.
Its seems to me that most simulations I do, overestimate the power achievable,thus indicating I am not able to meet the theoretical charging/scavenging efficiency numbers the sim is using.
Having an even better scavenging system would create even more unachievable power in the sim results.
The vast majority of my time is spent optimising the pipe and the intake geometry - the ports are easy, as the STA numbers direct you in the right direction all the time.
If you are short on blowdown the program tells you - you fix it, and get more power - simple,and you can be very sure that the mod you have just done would have worked on an engine , on the dyno, as well.

You can quantify experiment with real world data , , the software I use is a good guide thats all ( save a few hours and make feasabiliy studies easier ., what if !!) example I just completed a brake torque arm bracket , and just kept playing around with the shape untill I got it near what I wanted , if I get the new software working , the computer will do that part for me )

BUT it still needs to be buit and tested ,to back up , quantify the computer

Great tools ( the computer ) but ....

Stephen

[wobbly]

Comb Eff I vary depending upon the projected quality of the elements.
Running high com on Avgas with a toroid, in a square engine its up around 92%
Low com on pump with crap chamber shape and oversquare, its down around 82%.
Then lastly I move it around a bit if I have what seems to be too much power, but the curve shape is on the money.
It seems to be a fudge factor that can be used to move all the power up and down, it doesn't change the shape.

Re the computer sims believability factor, I have done so many trips to the dyno and got exactly what the sim said I would that its simply not an issue any more.
Only when reaching the outer limits, such as trying to model an RSA, that depends so much on alot of info we still havnt seen yet ( such as the PWM curve for the powerjets etc),then its a case of crap in = crap out.