ESE's works engine tuner

[Sketchy_Racer]

Rethinking the aircooled cylinder with water cooled head - is it possible to cut a couple of side trenches in the cylinder top deck, between the studs and force some water
into the hottest area at the top of the bore.

Yep possible, only problem to overcome on my cylinder in particular is casting porosity. Im not sure about other MB100 cylinders but mine is swiss cheese. I'll look into it and see if it might just be a case of sealing it up with some epoxy after milling pockets.



On a side note, had another play on the dyno tonight, picked up a couple more HP up top and 3 right in the middle of the "two peaks"
Dynos are always interesting, turns out I fluked the ignition timing to spot on for best power, any way than where it was lost power. And taking off the boost bottle picked up the 3HP in the middle of the two peaks, so whilst still not good, the mean average through the spread of power now is much much better.

So comparing the best run from the RM85 cheater bike and this rooted old MB100 the MB wins the dyno war at the moment!

[senso]

I've just disabled balancer on a Derbi 50 as an experiment. Didn't notice an increased vib at racing speeds. Might leave it off. Unless can be convinced otherwise. Engine obviously spins somewhat faster than road bike it was designed for.

Did the same in my crm 50 engine, the engine was much more responsive, but vibrated a bit, some screws fall off, all the plastics(fairings?) have broken, the gas-tank supports have broken off, but it revs better, so I left it out.

[F5 Dave]

If its in the rev range you use it is vibrating you should consider some rebalancing of the crank itself. My MB100 has a couple of 10mm holes drilled either side of the pin & it is fine at race revs, if a little vibey at say 5000, but who cares?, only notice that warming it up.

[TZ350]

More progress with the EFI tonight. Sure the graphs look ugly but the interesting thing for me was that 75-80-85-90-95 and 100% throttle position gave pretty much the same curve and power, these curves are from 25% to 70 and the last one at 100%

A while back Frits pointed me to the EFI's equivalent of an accelerator pump. It has taken me a while to learn how to use it, there are two parts, the first is selecting how much change in throttle position there needs to be before the accelerator pump kicks in and then the second part is the delivery curve of the pump itself. It seems I had it coming on to soon and far to rich. Now the bike is starting to respond to the throttle much better after closing it at high rpm then opening it up again, its still messy but I am confident I am on the right track.

[Flettner]

On my Kawasaki I turned the accelerator pump to off, much easier to tune.

[senso]

If its in the rev range you use it is vibrating you should consider some rebalancing of the crank itself. My MB100 has a couple of 10mm holes drilled either side of the pin & it is fine at race revs, if a little vibey at say 5000, but who cares?, only notice that warming it up.

I will try to do that, now that Frits has explained in a way that I can understand.
There is still one thing that I don't understand, are the holes made symmetric in relation to the crankpin, or are they made with different angular positioning?

[SwePatrick]

When mapping electronic systems om 4 strokes,, you should never have any throttle enrichment active until you stumbles into problems with response that can´t be solved any other way.
Then it might help solve that problems, best is if you manage to run without.

I figure it´s the same on twostrokes.

Rgds.

[speedpro]

I don't see the reason 4Ts with port injection need enrichment at throttle position change happening in a case injected 2T

[TZ350]

There is still one thing that I don't understand, are the holes made symmetric in relation to the crankpin, or are they made with different angular positioning?

Some are some aren't, Suzuki's had different sized holes either side of the crank pin on a lot of their early off road bikes (farm, trail and MX) and road bikes were symmetrical. Depends on how you want the vibration to go I guess. The norm nowdays seems to be symmetrical, maybe asymmetrical was too clever to be useful.

[TZ350]

On my Kawasaki I turned the accelerator pump to off, much easier to tune.

When mapping electronic systems om 4 strokes,, you should never have any throttle enrichment active until you stumbles into problems with response that can´t be solved any other way.
Then it might help solve that problems, best is if you manage to run without.

I figure it´s the same on twostrokes.

Rgds.

I don't see the reason 4Ts with port injection need enrichment at throttle position change happening in a case injected 2T

Good points, thanks.

Its set on by default, I will turn it off, I was trapped for a long while thinking the engine was stalling because it appeared to go lean when I closed then opened the throttle but it now appears the fire is just getting blown out by the over rich mixture from the accelerator pump. Frits had also warned me about to rich to fire means excess oxygen in the exhaust fooling the O2 sensor into thinking its running lean.

Speedpro had earlier suggested turning the warm up fuel off because it can confuse things, a bit harder to start and warm up but much easier to tune.

[wobbly]

I have seen several cranks with the holes each side of the pin asymmetric as well a several with the balance weight not quite opposite
the pin.
Does anyone have a rational explanation of this,I can see it would generate a peak reaction force offset from the TDC force of the piston
but what effect does this have on the overall balance, ie why do it.

[Frits Overmars]

I have seen several cranks with the holes each side of the pin asymmetric.

They can't have been Aprilia racing cranks then, as these have no holes at all, just a lot of slugs. But some are tungsten, some are very light.
The color difference in the picture below shows the asymmetrical distribution of light and heavy slugs. This is a give-away that these are crankshafts from the 90°-twin engine; their balance mass center of gravity has a 45° offset whereas the crankshafts of the Aprilia singles have no balance mass offset.

You (not you, Wobbly) may also wonder why there are so many slugs; couldn't it have been done with a much smaller number? Yes, but the large number serves a second purpose, apart from balancing. Putting light slugs near the center and heavy slugs near the circumference of the crank webs increases the crankshaft inertia without increasing its weight.

[Frits Overmars]

You may have noticed that I did not call the Aprilia 90°-twin a V-twin. The Aprilia twin engine is sometimes called a W-twin because of its two counter-rotating cranks whereas a V-twin usually means: two cylinders on one common crankshaft. Both the V-twin and the W-twin can be balanced pretty good (they're only beaten by the boxer twin; balance-wise you can hardly do anything wrong with a boxer). Below you'll find the balance theory behind the common 90° V-twin (courtesy of Tony Foale).
Attachment 310032

[F5 Dave]

Look at those Beautiful rods.
My, what large eyes you have.

[senso]

No, not Aprilia cranks, but cranks made and/or designed by some portuguese tuners and also some from the internet, sometimes they are really just holes, some times they fill them with aluminium or lead(poor mans tungsten, also prone to becoming loose in the bore), there is also on crank that I know that has a 5-6mm thick ring of bronze on the outer diameter, in part to increase the weight of the crank and in part to be able to re-use a crank made for a nsr/crm 50 engine in an nsr/crm 75 engine that uses a larger crank from factory, so hey, slap some bronze, hammer some pins and call it ultra racing.

A long time ago(more than 7 years ago) I bought my first two stroke related book:
The High-Performance Two-Stroke Engine by John Dixon
http://www.amazon.com/High-Performan.../dp/1844250458

At the time it only costed 50€, and for me it was a great book, not because it has recipes that say grind here and there and gain lots of horse power, its a more mathematical/physical approach to an engine, and in half a page he talked(wrote?) about crank positivity, has being a crank that has more weight on one side of the crank(considering that the wrist-pin is the center of the parting line) than on the other, so that when the piston is at TDC there is a slight bit more inertia to rotate it down, and on BDC there is the tendency to go up, it was finally a real explanation of a mythical thing that was talked in portuguese forums, but those who didn't know just tried to understand, those who understood the concept keep it to them.

But still today, I have some doubts its really helpful given how real racing cranks are made, but now those Aprilia cranks in fact have more mass in one side than on the other, fascinating.