ESE's works engine tuner

[monkeyfumi]

So a long rod would give minutely more STA for blowdown?

Edit, no, hang on, I think I have that wrong...

[2T Institute]

Yeah, I know, I sound like a grumpy old man. It's the weather, you know. Cold wind, rain... Wish I were in NZ right now.

Have some 45 deg days and 35deg nights to swap

[senso]

I might have my numbers totally wrong, but lets just compare a 105mm rod and a 115mm one in a 54.5mm stroke engine, the maximum rod attack angle for the 105mm one is 31.2º and for the 115mm one its 28.2º.
Regarding rod angle here is an image(blue line is the 105mm rod, 115mm is the red one, the same for the second image):




For me seeing the values is more intuitive than looking at number, I think that calculating the derivative of the rod angle would also be nice to see, so the acceleration values can be "seen".

[peewee]

hondas way of thinking seems like old hat. i would rather learn from jan and frits

[wobbly]

Yea well Hondas thinking may be old hat but making those sort of statements leaves you open to plenty of informed derision.
Consider the final year of the 250GP championship.
Who won, Honda and Aoyama, a rider that by all standards since, has made it obvious he could not ride his way out of a brown paper bag - even his injuries not withstanding.
Sure - plenty of excuses from Aprilia about Jan retiring and the resident idiots at the factory "improving " backwards what he had done previously, plus the problem
of the RSA having a front pipe that upset the weight bias on the front wheel, but still, the factory supported Honda didnt lack top speed, acceleration. nor handling.
The Aprilia riders also stole points off each other, making things doubly difficult, but Honda did the job with a 105 rod on a 54.5 stroke, Showa forks, useless reed valves, a No Name team and and only 1 dickhead for a rider.
Explain that in succinct technical terms - not wild generalities.

[husaberg]

Yea well Hondas thinking may be old hat but making those sort of statements leaves you open to plenty of informed derision.
Consider the final year of the 250GP championship.
Who won, Honda and Aoyama, a rider that by all standards since, has made it obvious he could not ride his way out of a brown paper bag - even his injuries not withstanding.
Sure - plenty of excuses from Aprilia about Jan retiring and the resident idiots at the factory "improving " backwards what he had done previously, plus the problem
of the RSA having a front pipe that upset the weight bias on the front wheel, but still, the factory supported Honda didnt lack top speed, acceleration. nor handling.
The Aprilia riders also stole points off each other, making things doubly difficult, but Honda did the job with a 105 rod on a 54.5 stroke, Showa forks, useless reed valves, a No Name team and and only 1 dickhead for a rider.
Explain that in succinct technical terms - not wild generalities.

Hondas strength are also its weaknesses... Honda have huge resources but they have huge committees.
Honda can't be seen to be copying off others so they tend to carry on with what they have already.
Sometimes there corporate pride cost them, they have to use Showa forks even if Olhlin's would make them lap a second faster.
They have to use Keihin carbs.
They pretty much had to keep with the RC valve
On the NSR250 they had to keep with the ELF patented Proarm.......
Most other companies were not hamstrung by these things.
Later on they had to keep to a certain fuel consumption, prior to the fuel limits

[peewee]

the worst part is we probly would have something even better than rsa125 if jan had no boundaries to work from. starting from scratch i bet he could make one hell of a engine

[Frits Overmars]

That an interesting machine, if not asking much, could you(Frits) explain a bit what it does and how it does its work? There is a stepper attached to the crank probably to rotate the engine, the hose in the intake might be a positive air pressure, and then there is a sort of x-y table on where the head would go, is it used to scan the bore in steps while measuring pressure(like a pitot comb, but instead of a use array of sensors/pitot tubes it scans the entire bore), or I'm totally wrong about my assumptions?

You're totally right, Senso.

DEAs anemometric flow tester uses a single tube with 10 i think individual pitots inside. This detects flow vector as well as velocity passing the tubes end. The pitot is CNC controlled to develop an array of measurements all around the cylinder and this is then displayed on a screen with coloured areas of differing velocity showing how the scavenging streams interact.

Like so:

Consider the final year of the 250GP championship. Who won, Honda and Aoyama. Sure - plenty of excuses from Aprilia about Jan retiring and the resident idiots at the factory "improving " backwards what he had done previously, plus the problem of the RSA having a front pipe that upset the weight bias on the front wheel.

Would you care to indicate that front pipe Wob ? It was the RSA125 that suffered from an upset weight bias because of the front pipe, not the RSA250.

(make sure you watch these pictures in maximum magnification )

[Grumph]

The other factor to consider with a reed valved engine is that they dont respond favourably to big case volumes like a RV does, with around 1.3 being
the effective bottom limit on case size.

That statement crept in without much comment Wob...as Prof J S Miller used to say, "why is it so ?"

Does a too large volume act effectively as an air spring, delaying reaction from the reeds ? Not so with the mechanically driven valve I'd imagine.
You'd think that given equally good transfers and pipe, the reed motor would like equally large case volume, but apparently not so....

[Frits Overmars]

as Prof J S Miller used to say, "why is it so ?"

Or, as I like to say: "Is it so?"
My experience with reed valve engines is limited, but I've been led to believe that the crankcase volume of a Honda RS125R is about the same as that of the Aprilia RSA. Have you got any values handy Wob?

You'd think that given equally good transfers and pipe, the reed motor would like equally large case volume, but apparently not so....

I too would imagine that a reed engine would like an equally large case volume, so any pressure drop in the transfer ducts during scavenging is kept within limits without the need to instantly accelerate the contents of the inlet tract.

A difference that does come to mind: rotary valve engines like large carburettors; reed valve engines seem to care less. Apparently they compensate for smaller inlet duct cross-sectional areas by keeping the reeds open longer, something a basic rotary valve can't do.

[husaberg]

That statement crept in without much comment Wob...as Prof J S Miller used to say, "why is it so ?"

Does a too large volume act effectively as an air spring, delaying reaction from the reeds ? Not so with the mechanically driven valve I'd imagine.
You'd think that given equally good transfers and pipe, the reed motor would like equally large case volume, but apparently not so....

Both Frits has seemingly alluded to it maybe is the case,and Wob has mentioned it before the Wob one was in regards to a Honda RS250 speed record attempt Honda I think.
I will find the quotes later.

Again this is the old story of trying to put specifics onto a huge generality.
The reed cavity of course is connected to the case, and it depends entirely what the total volume is,as to the advisability of
filling in the so called dead areas.

I have found that unlike a full noise rotary valve engine there seems to be no power increase if the case volume is made bigger than a 1.3 ratio when using reeds
be they direct into the case or cylinder mounted.
And another generality seems to be that the crappyer the transfer ducts, the ratio should tend the other way toward a smaller 1.4 ratio.

If the case was too small to start with and you fill the reed cavity dead areas, this will make it worse, and vise versa, but as all the factories are now tending toward making the reed box
smaller and smaller it would seem that filling the cavities and also filling the volume in front of the reed ( to the point where you would think the flow would for sure be affected badly )
then I would say its a good thing AS LONG AS YOU ARE MEASURING AND CORRECTING THE TOTAL CASE VOLUME.

In my testing I have found no more power going to a bigger than 1.3 case on a reed engine.
This is a function I believe of the efficiency of the rotary valve intake system being able to better fill the case at high rpm,using the 1.24 as Frits has described , but having said that
I have only just crept over 50 Hp with a 125 reed, and the Aprilia RV made alot more than that, so maybe a huge case simply isnt needed at the lower bmep.

[wobbly]

Yea as you would say Frits "glad someone is awake " - the comment about the RSA front pipe upsetting the balance had nothing to do with the 250 issues - was just an example of
one of the many "excuses" from Aprilia land about a reduction in on track performance.
The Jan inspired new engine was obviously better, the 125 chassis wasnt ,but sadly the two arent mutually exclusive.

I have got into many heated discussions about Aoyama and the Honda winning the title that year but it always comes back to the same issues for me.
How the hell did it happen if the Showas are a second a lap slower.
Then worse - reed valves,short rods and flat tops are useless.
The rider has since proven to be of limited skill, pretty much a death blow.
And worst of all it was a very old design including the silly skinny pipes,as Honda had stopped serious development of the 250 several years previously.
The Scott 250GP team had one Honda technician, the rest were for sure not famous in pit lane but they collectively kicked Aprilias arse.
And yes the Aprilia boys did some dumb shit, and were continually stealing points off each other, etc etc, but the Honda was fast enough to win with all those
issues that many would have me believe should make being even top 10 impossible.

A Honda RS125 has a case com of exactly 1.32 with a VF2, measured it several times, the reeds glued shut and the case filled up to the top of the transfers.
Then the piston run to the top of the bore,and finally filled to the top thru a hole in the dome.
Thus ensuring the transfer ducts are completely full.
A stock reed will have a little more case vol but looses power everywhere.
Then I machined 5mm off the reed box face - lost overv power past 13,000 but gained alot of mid.
Then added a 10mm spacer, so + 5 over stock - lost power everywhere.

Here is another example, a YZ85 for Flat Track racing.
The big case has some more power well into overev, but its never used.
I have done dozens of sims on all manner of reed engines and have never seen one make better power under 1.3 case com.

Latest test - TM KZ10B, add a 5mm spacer to the reed box,loose 1.5 to 2 Hp up to peak, gain 0.5 at 14500,so my next test will be to
machine that case to take 5mm off the reed box when I rebuild the dyno engine.
Gaining mid is real hard in those engines, getting overev power is easy with timing and a shorter pipe/manifold and a smaller stinger insert.

[Grumph]

Or, as I like to say: "Is it so?"
My experience with reed valve engines is limited, but I've been led to believe that the crankcase volume of a Honda RS125R is about the same as that of the Aprilia RSA. Have you got any values handy Wob?

I too would imagine that a reed engine would like an equally large case volume, so any pressure drop in the transfer ducts during scavenging is kept within limits without the need to instantly accelerate the contents of the inlet tract.

A difference that does come to mind: rotary valve engines like large carburettors; reed valve engines seem to care less. Apparently they compensate for smaller inlet duct cross-sectional areas by keeping the reeds open longer, something a basic rotary valve can't do.

Ah, but do they keep the reeds open longer ? i remember Jennings writing up reeds in Cycle mag and quoting an SAE paper by the Yamaha guys who developed the DT/RD series. They found that yes, the opening period varied - as did the timing - but at peak RPM the reed timing was the same as the roadrace rotary valve timing they were familiar with. That was with the very basic steel reeds of the period, i have no idea if the modern composite reeds act differently.

[jonny quest]

While that info is great Wobbly, you're changing more than just case volume when you're changing reed box length. Is it inlet tract length that's doing more of the gains/loss? I'd hazard a guess and say so over cases volume

[wobbly]

Wrong - making the case shorter, or adding a spacer has NO effect on the intake tract length, that is defined as reed tip to bell end.
Here is the KZ10B intake - made as short as possible by recessing the manifold into the reed block.
The spacer is 5mm and will be added to the case after machining to be able to make the case volume back to stock, no effect whatever on the tuned length..

One reason I believe that a VF reed block makes more power, apart from the increased tip curtain area, is that the W configuration
will always reduce the case volume a little - and many engines have the case too big to start with due to the specific layout - like the YZ85.

When the case is bigger you have to make the reeds thinner to get them to open as much as previously.
With the case down at 1.24 the reeds need to be so soft they very quickly begin to go spastic from what may loosely be called " flutter ".
ie overbending and or smashing into the stops at higher rpms, due in part to their own natural vibration frequency coinciding with the harmonic frequency of the intakes tuned length..
When this happens, power drops dramatically as you can imagine.