Glitches aside, if using 1.3 gives 'normal' outcome and 1.6 gives better outcome but real world says 1.3 should be better something is a miss right?
Not that I know how and what, just saying, also not claiming that's an engmod issue!
Engmod seems glitchy here and there, hope the next update adresses those instead of new features. Ccv I calcuated by measuring the total volume including transfers, then measure the volume of transfers and see if these where the same as calculated in engmod.
All the 250s I have actually measured are mid to high 1.3 ratio.
When you are watching the Ex pressure trace ( measured at the port face ) you will see the pressure ratio varying in value where it crosses
the cursor at EPO.
You will have superposition when the crossing point is above 0.
The higher this value the higher the scavenging ratio at the port goes - a really good diffuser with the added superposition will go off the scale.
Here is an example of good superposition and a really good diffuser acting together.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
I have absolutely no idea how one can measure the case volume without the transfers - please educate me.
Engmod calculates the transfer volume from the port area, the inlet/exit ratio and the duct length, so this volume is
entirely dependent on the input accuracy, especially the correct length ( as this is also a large part of the case, if you read the help files ).
Running the code with a CCV of 1.6 is an insane input, so the result will be equally insane output - its not a sim issue at all.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
The MC21 is 45HP restricted by CDI timing curve. There is a well known wire splice mod, but it also has a gear position sensor.
From my understanding, 1st gear is most agressive timing curve, 2nd slightly less agressive, and 3rd gear a decent curve for pump gas street use.
My question, if you don't perform the wire splice mod, leave everything stock... are these bikes 60HP in 1st, 2nd, and 3rd gear.... but restricted to 45HP in 4th, 5th, and 6th?
The MC21 is 45HP restricted by CDI timing curve. There is a well known wire splice mod, but it also has a gear position sensor.
From my understanding, 1st gear is most agressive timing curve, 2nd slightly less agressive, and 3rd gear a decent curve for pump gas street use.
My question, if you don't perform the wire splice mod, leave everything stock... are these bikes 60HP in 1st, 2nd, and 3rd gear.... but restricted to 45HP in 4th, 5th, and 6th?
I had major problems with the wire splice method when I first got the NSR300 going. We messed around for ages and could only ever get 60hp. Plug in HRC bypass loom and 72 straight away. I run an ignitech now. We never did an all gears run so could not tell you about 1st to 3rd sorry.
Running the code with a CCV of 1.6 is an insane input, so the result will be equally insane output - its not a sim issue at all.
Oke, that will be true but then... I start at 1.3 and increase it and it keeps making more power. How do I know where the input starts being insane or, probably a better question, what am I not adjusting as well so the power doesn't go up anymore since that wouldn't be the case in real world?
ps; more of a hypothetical question btw although I to have encountered this 'issue' in the past, never went to 1.6 though. Would have to dive in again to see how my model fares now, maybe a none issue but perhaps for broather understanding of things/ engmod.
Thanks Wobbly again for the example above regarding the exhaust.
My question was, why does engmod default the crankcase volume to exclude transfer port volume from the ratio, when we are using the transfer volume to do the calculation?
I've just opened some of the other projects to verify. The radio button of, 'transfer volume excluded from ratio' is always selected. Should we be running the sim with, 'transfer volume included in ratio' instead?
The code will always have the transfer duct volume available to it, as I pointed out you have to input the areas and length.
But Neels must have been reading this thread and has just sent me an update to make the inputs clearer to everyone.
I will install this tonight and report to him and you.
Edit - OK Neels has changed the help file to make clear what is happening.
In most cases you will simply be using the default ie a volume measured a TDC thru a hole in the piston and this of course includes the transfer ducts.
He has made it clear now why we need other options, including the fact that if you change the transfers, this will then be updated automatically in the code as CCR ie Calculated Compression Ratio
Regarding useful values of case vol.
The Aprilia RV engine has it down at 1.24 or so ie a huge volume as would befit it huge power output.
I have found that 1.3 is about the optimum top limit for a full house reed engines ie KZ kart 125, as with a bigger case you have to keep on installing thinner reed petals and eventually they hit the stops and go spastic
or simply lift too far then flutter with no control.
This I have absolutely dynoed to death on the TM KZ10B kart engine, as a small change in case vol under 1.3 looses mid power, and a small change above 1.3 with a reed spacer looses
all the overev power - no matter what reed stiffness is used in each case..
Engines with crap transfer ducts need the ratio up closer to 1.4, and I have never seen anything go at all well with a case smaller than 1.4 ( by smaller I mean volume ie say 1.45 ).
But as always remember that the code can only recognize crap ducts in a limited fashion ie the input you have control over in specifying the shape.
Re MC21 and its ignition control.
There are two parts to the Honda ignition control.
First is the blanket retard function that is easily disabled with the wire splice method.
But secondly there is a function that limits the road speed to 180Km/Hr max in 4th,5th,6th.
This can be disabled by fooling the ECU into thinking it never goes past 3rd gear.
As to the curve in 1st gear being the most aggressive, this is a possibility, but I have never seen any evidence that the PGM software has the ability to store
more than 2 curves.
So it makes sense that 1, 2, 3 are the same and 4.5.6 are the same.
Reworking the gear detector so it never tells the ECU 4th is selected would keep the more aggressive curve active.
I only say more aggressive in that as the rpm rate of change is so much faster in the 3 lower gears, Honda would be logically happy to wind in alot more advance without
fear of meltdown on shit fuel and or long periods of WOT.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
All the 250s I have actually measured are mid to high 1.3 ratio.
When you are watching the Ex pressure trace ( measured at the port face ) you will see the pressure ratio varying in value where it crosses
the cursor at EPO.
You will have superposition when the crossing point is above 0.
The higher this value the higher the scavenging ratio at the port goes - a really good diffuser with the added superposition will go off the scale.
Here is an example of good superposition and a really good diffuser acting together.
Hey Wob, the minor pressure fluctuations (of around 40 to 45 deg) in the transfer port after TPC, are they real as a result of resonance within the passage or some reed tip frazzle OR some EngMod calculation perturbation? The pipe is doing a good job, well to me anyway.
Hey Ken, I have always thought that the sine wave fluctuations in the transfer ducts after TPC were a result of them being converted from an open pipe ( ie the duct open at both ends )
into a stopped organ resonator ie one end only open.
The pipe in the example I gave was well past its designed peak, as the max pipe/port depression is well past BDC, but the superposition of the scavenging effect is so strong it easily overcomes this
natural movement of the peak depression moving rightward ( too late ) with rpm.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
This is a neat site in that if you, say, go to MITAKA, click on road bike rod kits, then your bike & model and up comes the rod crs, widths, diameters etc. Ditto with pistons. Good if you're chasing bits to swap around between motors.
This is a neat site in that if you, say, go to MITAKA, click on road bike rod kits, then your bike & model and up comes the rod crs, widths, diameters etc. Ditto with pistons. Good if you're chasing bits to swap around between motors.
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Originally Posted by jonny quest
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