ESE's works engine tuner

[adegnes]

Thanks Wobbly! I'll contact ignitech, maybe I can persuade them to add more map points to the pwm output.

[Wos]

Yes the processor interpolates between data points.

Is ignition table also interpolated?

Thanks a lot!! 😉

Grüße Wolfgang

[wobbly]

Yes. And a point to note is the PV seems to work better/faster with the least number of set points along the curve.

[palezu]

Update of my high power 50cc sewing machine MB40 transfer cylinder project. It seems I have finally cracked it and of course it was the simplest thing of all, exhaust porting. I went and hogged the auxiliary ports to double the size that they were before and thinned out the bridges. The thing got a huge boost and now the best number is 15.3 rear wheel hp at 13800 with no precise tuning. Probably has close to 10nm of crankshaft torque which is amazing. Exhaust timing is about 198 and aux ports are maybe only 3 degrees lower. I also tried the much discussed 1.3 case compression and found that it lost power significantly, about 1hp everywhere. When I removed case stuffing the power went directly back up where it was. Currently the engine has only a 1.19 case compression ratio (Minarelli AM6 cases).

It seems that Frits MB40 transfers, without the legendary B duct hook, can work just as well as a normal duct setup. I even have a huge 12mm adapter plate for the cylinder mounting which makes the transfers that much shorter so the transfer geometry is a lot different than normal. I am sure there is more in it because now there is some errors in the port heights, A port is lower than piston edge at BDC and I also have a stock-size AM6 vforce reed valve which I believe is restricting flow somewhat. Exhaust outlet area is roughly 28mm equivalent and the pipe starts with that diameter. I have not calculated outlet/cylinder port area ratio. Previously I said that the 75% rule probably doesn't work in a 50cc but now I see that if you make the cylinder ports freaking huge, then it starts to make more sense. I'm guessing the outlet area is somewhere between 85-90% now.

[wobbly]

Several points to make clear - any change in CCR will require a change in petal thickness to optimize it. Big cases will work fine with a reed as long as the 1st Mode frequency of the
petals matches the Helmholtz of the case. But it has been found that as a general rule a big case down at 1.2 needs reeds that are too thin , and they go spastic at high rpm.
The 1.3 general guide seems to need petals that give the desired power, and also retain control when pushing peak power rpm to the mechanical limit.
In a 50 cc - 13800 rpm is not even remotely close to the mechanical limit - go to 17,000 and things will be very , very different - as would the possible power potential.

The current 125 KZ engines make peak at that same rpm, and with say near 17 crank Hp at that 13800 rpm, the 50cc is only pushing 11.16 Bar bmep , so isnt even warmed up yet.
If you simply made a smaller case in isolation and didnt try changing the petals , then there is very likely unseen power left on the table.

The B hook cannot and does not " work " in isolation. If the radial and axial angles of the other transfers do not conform in general to the Frits/Aprilia scavenging pattern ie the staged
decreasing axial angle of A & B and the radial wall angles meeting at about 1/3 distance from the boost face to bore center ,the B hook wont be effective as it works in synergy with those
other elements to create the Leaning Tower column up the back wall, plus it clears out more Exhaust residuals in front of the boost port.

And if the duct exit, after making a big increase in Blowdown, is now approaching 85% , then it was miles too big to start with , and needs reducing even more to be anywhere near optimal.
Using the 75% guide with 100% at the header entry gives a steep ( 10* -14*) of diffuser slip joint transition right at the duct exit , and this instantly gives a huge boost in peak and overev power
when approaching 0.8 Mach at the restriction point.
You can choose to use that ,as is, or lengthen the pipe and get more power everywhere.

[Flettner]

What percentage exhaust on this one?
Treat it like two single port 65cc?

[wobbly]

Determine the chordal area of the port at the bore face x Cosine of the roof down angle x 0.75/2 = area of each of the two duct exits.
This assumes a T or 3 port setup with shit tons of Blowdown STA.
For a race single port the multiplier is around 0.9 but for those low bmep engines the bulk gas flow is slow compared to a " hot " engine so in this instance I have been down to around 0.8x
to get the exit up near 0.8 Mach .
Still cant believe you have recreated the first 2T that I ever played with - a Jawa twin Exhaust port.

[Flettner]

But with modern transfer arrangement, Nikasil bore and a far more modern pipe (pipes) design.
Next cylinder is water cooled ( even in under the A ports) and twin gate type powervalve.
I haven't seen that before, have you?
Should be intetesting.
170 odd degrees of port rotation around the cylinder with only one bridge. And no port 'wall' in the way at the port extremities.

[wobbly]

Not in any way a criticism of what you have done Neil , in fact the opposite really.
But as a young fella, me ( and everyone else I assume ) I always wondered what Jawa were trying to achieve, as to my knowledge its not been done again since.
You have very good logical reasoning behind the idea , best of luck with the development.

[Grumph]

Not in any way a criticism of what you have done Neil , in fact the opposite really.
But as a young fella, me ( and everyone else I assume ) I always wondered what Jawa were trying to achieve, as to my knowledge its not been done again since.
You have very good logical reasoning behind the idea , best of luck with the development.

According to Irving, it was to avoid a single concentration of heat source. But he also points out the badly cooled area between the ports.

I liked riding the twin-port motocrossers. A couple of friends had them and I'd borrow one for "visitors races". Which are now a thing of the past.

[pete376403]

According to Irving, it was to avoid a single concentration of heat source. But he also points out the badly cooled area between the ports.

I liked riding the twin-port motocrossers. A couple of friends had them and I'd borrow one for "visitors races". Which are now a thing of the past.

Could it be anything to do with exhaust volume, ie two slim expansion chambers giving more ground clearance (useful in MX) than one big fat pipe? I recall the CZ pipes were always underneath, while the Japanese bikes used a single high pipe

[Grumph]

Could it be anything to do with exhaust volume, ie two slim expansion chambers giving more ground clearance (useful in MX) than one big fat pipe? I recall the CZ pipes were always underneath, while the Japanese bikes used a single high pipe

The twin port pipes were always heavily dented. Memory says a mate blew the dents out twice a season.

[F5 Dave]

Could it be anything to do with exhaust volume, ie two slim expansion chambers giving more ground clearance (useful in MX) than one big fat pipe? I recall the CZ pipes were always underneath, while the Japanese bikes used a single high pipe

The TMs etc had low pipe., I bet someone got excited as the first high pipes were seen, and the collective race teams face palmed then fired up their welders, while the production factories were trying to hope the problem away for a few years.

[Flettner]

Who knows?
But at least I can give it a go, lets see what happens.

[husaberg]

Not in any way a criticism of what you have done Neil , in fact the opposite really.
But as a young fella, me ( and everyone else I assume ) I always wondered what Jawa were trying to achieve, as to my knowledge its not been done again since.
You have very good logical reasoning behind the idea , best of luck with the development.

According to Irving, it was to avoid a single concentration of heat source. But he also points out the badly cooled area between the ports.

I liked riding the twin-port motocrossers. A couple of friends had them and I'd borrow one for "visitors races". Which are now a thing of the past.

i assumed the same as Greg plus the ring tech plus the piston tech might not have allowed wide ports.

Geeves was also a twin port 360n and 380 they also like a single down tube which may have been a factor only the larger models had the twin ports.


1920's Villiers had twin ports (plus autolube) and water or air cooling
I think Blair of QUB might have had a hand in the design or maybe just its redesign of the large greeves and I think their large bore QUB500 air cooled single might have also been twin port (at least one model)