ESE's works engine tuner

[TZ350]

Not there yet with the simulation but its starting to look similar to the real thing.

[dinamik2t]

Hey TZ, would you mind exchanging combustion files?
I am very interested in seeing what afr and comb.efficiency values do you guys use in your simulations.

I get akwardly good results from mine and I would like to compare my values.
Here's a couple of pics. It's an 118cc engine.




Also a short introduction and a few comments.. My name is Vagelis, I come from Greece and I am a student of Physics (more into electronics though than thermodynamics or mechanics)


I have been reading the topic at pitlane and now saw the TFR timings of the RSA mr. Frits gave away.
I have ended up in the same concusion through sim testing. If rear TFRs open earlier than the front ones, more power is gained than the opposite combination!
Yet, in a couple of Honda port maps I've seen, fronts open earlier than the rears.. Does the latter serve any particular cause? (eg a different power/torque delivery)
Or is it just a pattern in older Honda cylinders?


And about the books you discused in earlier posts: Has anyone read "The high performance two stroke engine", by John Dixon?
I found it online at a very low price and got it a while ago. It does (rather .. "he does") a great analysis of the physics throughout the engine and does not offer much "tuning tips". Actually, that's more preferable in my opinion. Intelligent people should learn "how stuff works" and decide their own modifications afterwards, instead of "do that, that and that".

Here's the front cover of the book:

[TZ350]

Hey TZ, would you mind exchanging combustion files?
I am very interested in seeing what afr and comb.efficiency values do you guys use in your simulations.

Hi dinamik2t thank you for letting us see your combustion file. I have only just learnt how to enter basic data like the engine file, transfers and pipe and have been using what other default files or copying stuff that looks close so my files wont be much use.

My posts are the journey of a newbee learning to use a simulation software package. Hopefully someone with more experience than me will post some interesting files and comments as I am keen to learn more about them too.

[koba]

Intelligent people should learn "how stuff works" and decide their own modifications afterwards, instead of "do that, that and that".

Most of us can only wish we were that intelligent!

[dinamik2t]

I don't have any problem letting people see what I "play" with. There isn't any commercial issue or profit, from my files at least.. Mr Frits and mr Jan gave away info freely, that many people used in commercial ways!

To be honest am not much into becoming a paid engine mechanic (an engineer, that we can discuss). I like learning and searching stuff and I occasionally port (as much as my abilities/knowledge permit me of cource -not much) some cylinders for engines similar to my own. Just for an extra income. Anyway..

Here is the whole file of the above pics: http://users.uoa.gr/~sph0800108/mode...15-11-2011.rar
I would be gratefull if people with more experience than my own checked these files and told me where I am wrong or suggest a couple of things!
I would have many things to say encore (gratitute, enthusiasm, questions, more enthusiasm, more questions), but it will be too much blah-blah!

As for the engmod file, I concentrate my attention for possible inaccuracies in combustion efficiency, temperature and AFR values. I have no idea what real-life values would be achievable.

[dinamik2t]

Most of us can only wish we were that intelligent!

Yes! To explain myself, I didn't want to imply that I am the intelligent one to do thus. I believe though, that an average clever person can achieve that quality through learning and that's what I aim for. Until (a) God appears in front of us, everything is a matter of science. Since something is already discovered, we can only learn it, not reinvent or rediscover it (unless it's wrong, but we still have to know the wrong to find the right).
The more you know, the more you can understand. And the more intelligent you are, the more innovations you can build into the 'understood'.

[Frits Overmars]

.... I have been reading the topic at pitlane and now saw the TFR timings of the RSA mr. Frits gave away. I have ended up in the same concusion through sim testing. If rear TFRs open earlier than the front ones, more power is gained than the opposite combination! Yet, in a couple of Honda port maps I've seen, fronts open earlier than the rears.. Does the latter serve any particular cause? (eg a different power/torque delivery) Or is it just a pattern in older Honda cylinders?

It is a pattern in all Honda cylinders, Vagelis. Even the cylinders of their last (2009) 250 cc works racer (and don't ask how I got my hands on it) had high A-ports, somewhat lower B-ports and an even lower C-port. We call this the Dalton Brothers-configuration. If you know the Lucky Luke strip albums, you will know what I mean.

[dinamik2t]

Yes, indeed! And Joe is also shorter by 2-3 degrees than the B-ports (even shorter than Averel!)

Mr Frits, I have noticed one more thing that looks strange to me.
Here are two photos of the stock port layout of my cylinder.




Encircled in green there is a sudden bent in the A port duct. I understand this must be to give the incoming mixture a backwards angle. It is very sudden though and I have noticed this in other cylinders also, even some older Honda RS cylinders. My guts tell me that this angle should be more gentle and the duct should follow that bent all the way from the cylinder base (like the red sprayed right duct).
Say, my cylinder has small ducts (for a certain mass production reason), they needed that size of port window and that angle, so it was designed that way. But other cylinders with decent port duct/window sizes have the same bent.
Is there a particular purpose of such a design?

[gamma500]

Frits,

I have used ''simple'' pipe calculations you posted on pit-lane.biz, and found out that those calculations give bigger expansion chamber diameters for lower exhaust port timings.

I have been wondering why engines with lower exhaust port timings need ''fatter'' pipes?

[Frits Overmars]

Yes, indeed! And Joe is also shorter by 2-3 degrees than the B-ports (even shorter than Averel!)
Mr Frits, I have noticed one more thing that looks strange to me. Here are two photos of the stock port layout of my cylinder.


Encircled in green there is a sudden bent in the A port duct. I understand this must be to give the incoming mixture a backwards angle. It is very sudden though and I have noticed this in other cylinders also, even some older Honda RS cylinders. My guts tell me that this angle should be more gentle and the duct should follow that bent all the way from the cylinder base (like the red sprayed right duct).
Say, my cylinder has small ducts (for a certain mass production reason), they needed that size of port window and that angle, so it was designed that way. But other cylinders with decent port duct/window sizes have the same bent.
Is there a particular purpose of such a design?

The backward angle of the port flank nearest the exhaust (the green line in your drawing) is important, but I agree that your duct is not a thing of beauty.
But the right-side duct, though it may look more attractive, is even worse. The backward angle of the green line may be somewhat exaggerated, but the blue line is not sufficiently angled backward, which will result in short-circuiting: fresh charge from the A-ports will make a U-turn and escape directly into the exhaust duct. And it will do so as soon as the transfer ports open, which means it will be too far down the exhaust pipe by the time the return pulse tries to shove escaped charge back into the cylinder.
I can only guess as to the purpose of such a design. Maybe it is not even a deliberate design but just the result of using existing casting cores for a new cylinder.
Or maybe the cylinder studs were in the way...

By the way, I appreciate you calling me Mr. Frits, but there is no need; just Frits will do fine .

I have used ''simple'' pipe calculations you posted on pit-lane.biz, and found out that those calculations give bigger expansion chamber diameters for lower exhaust port timings. I have been wondering why engines with lower exhaust port timings need ''fatter'' pipes?

Remember what I said about those simple calculations: they are only meant to help beginning tuners on their way and a lot of more or less important facors, like compression ratio, ignition timing, type of fuel, carburetter diameter, crankcase volume and angle*areas, are not taken into account.
In your example the important thing is that lower exhaust timings need bigger header diameters. But explaining why this is so, might be beyond the scope of this forum (and it would certainly be beyond the time I have at my disposal).
But come to think of it: the least I can do is post the same simple calculations here. Instead of all those factors I left out, I included one variable, the speed of sound. Starting with 550 m/s will get you in the right ballpark, after which you can vary this value according to your findings.
Final remark: the calculation of the tailpipe restrictor diameter is critical: you can only apply it to engines that are thermally sound. Air-cooled engines are not...

[gamma500]

Remember what I said about those simple calculations: they are only meant to help beginning tuners on their way and a lot of more or less important facors, like compression ratio, ignition timing, type of fuel, carburetter diameter, crankcase volume and angle*areas, are not taken into account.
In your example the important thing is that lower exhaust timings need bigger header diameters. But explaining why this is so, might be beyond the scope of this forum (and it would certainly be beyond the time I have at my disposal).
But come to think of it: the least I can do is post the same simple calculations here:[/QUOTE]

Thanks for the answer.

I have simulated some pipes designed with those calculations, and the results have been excellent.

[dmcca]

There should be no widening just before the port exit; the duct cross-section area should gradually move from entry area to exit area. And with the inner curvature of the duct fixed, this more or less lays down the shape of the outer curvature.

Thanks Frits. After looking at the CAD image of the RSA transfer ducts (attached) that has already been posted it appears that the B ducts (and im assuming the A ducts) widen sideways just before they exit into the cyllidner so I assumed that the cross sectional area was increasing here also... I had made the assumption it was something to do with controlling or slowing the flow just as it enters the cylinder

We call this the Dalton Brothers-configuration. If you know the Lucky Luke strip albums, you will know what I mean.

Re Ignitech starting issues, and base advance.
Post up a screen shot of the "Bike" page and advance curve, I may be able to help with that.

Thanks Wobbly... they are attached.
The bike is running very well now with this curve so im just trying to understand the need for such low base advance... whether its an ignitech issue or a mechanical characteristic of the engine.
Also the curve above 5k really needs to be tested on a dyno... its just a guess at the moment as i havent had much chance to ride it flat out, i tend to do slower, technical stuff at lower revs. It does currently rev out well though.

[wobbly]

Here is a comb file for a very fast RS125, where the sim is all but perfectly reflecting reality.
The difference between the sim and RWHp is around 10 to 12% as you would expect - despite what many say about the fudge factors in a Dynojet.
The comb file has afr as measured on the dyno - and shows the correction of the ratio naturally going rich over the pipe, by the powerjet switching at 12200.
Without the powerjet it would go very rich, and would not make any power past 12600 - as in reality.
But for most sims, you will be in the ballpark simply running 12:1 in all fields.
The comb efficiency is good for full house racing 2T at 0.92,less well tuned engines will be down between 0.87 and 0.9
And the combustion variables are as calculated by the program using the turbulent model - you use burnrate prescribed until the model is well refined,then run turbulent ( very slow)
and transfer the results from that run manually,to speed up later sims by using real burnrate numbers.
Re the question of cylinder temp.The important factor is TUbMax - the temp of the end gases trapped in the squish.Optimum is around 1000*, but if its too high, the sim will automatically
show a warning on the screen - "deto" as the run is progressing.
Too lean, and or too much timing or compression and this warning comes up, believe it and change something to fix it, or your computers piston will sieze.
PS - I need your .pjt file to make it easy to open the sim.
Neels is working on a "pack and go" button that will collect all files for a project and put them in one file to send out for review.

Re the A and B port stagger.
Honda have always run the A port higher approx 0.7mm giving timings of 132/130/129.
This works OK using the big T port,but in the Aprilia 3 port layout, when pushed to the extreme as Jan did, the A port is lower to allow more area for the huge Aux ports needed to give sufficient blowdown.
Then the B port is raised to get back the needed transfer TA.

Re the ignition problems at starting.
Two things, firstly reverse the wires from the trigger and delete the reverse polarity button in software.Many times the trigger wired backwards gives very odd results when strobed.
Secondly, look at the "number of programmings" no way have you done 33,000 changes - this means the ECU is being corrupted by RF noise, you need to check the resistor plug cap and plug, as well as
ensure that the hot wire to the coil is well away from the trigger wires etc.
Also the curve is very odd.
Any tuned engine will like 28* advance in the mid under the pipe, then where the bmep starts to rise as the pipe works, around 8000 in your engine, you start pulling out timing, heading for around 15* at peak torque.
Depending upon how its set up, then less advance may be needed at peak power and beyond to make it rev out.
Below is a curve for similar rpm as your example.

[TZ350]

Zschorlau 2005 by walkyrie49

A few interesting bikes here.

[TZ350]

An interesting look at a Kreidler transfer passage.



Supercharged DKW