ESE's works engine tuner

[Greg85]

[QUOTE=Greg85;1130977145]hello,
i am new to the forum,this is very good forum for two stroke!
i am interseted in a lot of karting engine ,now i am interested in working with the cylinder jaros bench is anyone really knows this system for well optimized
cylinderworked in what sense?
THANK YOU http://imageshack.com/a/img921/937/VVRVTt.jpg

[peewee]

guys I have a new crankcases and all the surfaces are rough and bumpy from the casting. is there any reason not to smooth down all these surfaces ? atleast so maybe a crack doesn't form in the future

[wobbly]

The belly diameter as far as I can see has no relationship to the engine displacement.
Its all down to effective energy recovery within the pipe,and as the energy is finite you can decide where that energy is used.
As Frits says, the latest really fast 125 engines are a bit over 130mm, and use steep tapers to extract the maximum ( optimum ) depression
and reflection pressure ratios at the Ex port.
The bmep sets the available energy, and as you go up in displacement it becomes harder and harder to get anything like the bmep numbers of the square 125.
If you tune a MX250 to the highest possible level for road racing, then the long stroke limits what can be achieved and I found that when going thru the exercise
of developing a pipe for this class that a belly over around 140 ( with steeper angles ) makes no more power.
The square bore/stroke Gas Gas for example can go a somewhat harder, but it then topped out at about 145mm.

Re the Jante CNC driven scavenging vector visualizing machines.
These use a small tube with several pitot sensors linked to a computer that shows the velocity and the direction of transfer flow.
They take a huge amount of time and experiment to determine what the effect of these vectors have on scavenging.
But when finally understood, the Yamaha chief engineer that developed the cylinders for the 500GP machines that went on in 2000 to win the 250GP class, said to me it took him 3 years but he was now
able to predict the power curve with his Jante,without needing to use the dyno for confirmation.
Bartol had one for years but I dont think he ever really got a handle on what he was seeing on the screen, as most of his later work I have seen was basically a copy of Honda technology.
But the Roberts guys had one at Bud Asklands workshop, and he really knew what needed changing,and this helped Rainey and Yamaha immensely when Kenny was allowed to overule
the factory engineers with his own work.

[Frits Overmars]

i am interested in working with the cylinder jaros bench is anyone really knows this system for well optimized cylinderworked in what sense?

Here you go, Greg.

[oldjohnno]

The belly diameter as far as I can see has no relationship to the engine displacement.
Its all down to effective energy recovery within the pipe,and as the energy is finite you can decide where that energy is used.
As Frits says, the latest really fast 125 engines are a bit over 130mm, and use steep tapers to extract the maximum ( optimum ) depression
and reflection pressure ratios at the Ex port.
The bmep sets the available energy, and as you go up in displacement it becomes harder and harder to get anything like the bmep numbers of the square 125.
If you tune a MX250 to the highest possible level for road racing, then the long stroke limits what can be achieved and I found that when going thru the exercise
of developing a pipe for this class that a belly over around 140 ( with steeper angles ) makes no more power.
The square bore/stroke Gas Gas for example can go a somewhat harder, but it then topped out at about 145mm.

Thanks Wob. It seems that once the cylinder gets bigger a whole lot of practical considerations come into play. Accommodating a huge pipe on the bike is one, then there are the rpm limits set by piston speed and vibration levels. On top of this is the fact that the big single will most likely have only 5 gear ratios and I guess it takes longer to fully burn the contents of an 80mm diameter chamber than a 52mm one. There's less cooling surface area and the big pots seem more prone to knocking. Something else I've come across is the lack of cylinder wall area in which to cut holes - as the cylinder is made bigger (and especially if it's oversquare) the wall area to cylinder volume ratio decreases. Try as you might, you can't cut a hole in a hole...

[TZ350]

Spent an enjoyable day playing with the dyno and EFI system.

I took the time to carefully check the actual timing of the injection end point. I did it in much the same way you would check the ignition timing with a strobe light and found that where the software said it is and where it actually is, is pretty much spot on.

After a lot of careful work starting just before the transfers open and making 5 deg incremental adjustments until just after the transfers close. I found the best spot for my engine was to finish the injection cycle at 200 deg before TDC.

The Ectrons EFI system measures everything in deg BTDC, so my transfers open 245 deg BTDC and close 65 deg BTDC and by experiment the best injection end point is 200 deg BTDC, so a lot of the injection cycle into the transfers is happening before the transfers actually open.



Now that I have confirmed that the injection end point sweet spot is around 200 deg BTDC. The mass flow simulations make more sense. When you look at the Engmod2T simulation for my bike, of mass flow through the transfers. They all peak at about 200 deg BTDC. Or just before BBDC, and around BDC is where Wob says the pipe should be sucking the hardest.

The Ecotrons EFI software has an injection end map that allows for fine tuning of the injection end point over a range of RPM and Engine Load. So a bit of fine tuning to do but for now I am confident that we are in the ballpark. And that if the software says 200 deg BTDC then that is pretty much what it is, I was never sure before.

[jfn2]

Hello Frits;
I was not able to see the exhaust concept drawing you posted yesterday. I usually don't have any trouble. Would you please repost the pic? Thank you very much. Jeff

[Frits Overmars]

No problem Jeff. But if I do the same thing twice, chances are that so will your computer.
Maybe the picture format plays a role. The png-format that I use, doesn't normally give any problems but just in case here are a png- and a gif-format.

[Martin1981]

Wobbly, i have a Question regarding the 04 CR Cylinder you talked about not long ago.

I have one but I can not see the reverse Transferport Stagger. Is it only a couple of Tenths of a mm so one can`t see it? Also it has very high Transferports, about 15mm.

I know that there are 2 Types of Cylinders. Cylinder A 12110-KSR-A00 and Cylinder B 12120-KSR-A00.

So is it possible that Cylinder A does not have the Stagger and Cylinder B has it? Or are there other Differences between the Cylinders?

Thanks!

[jfn2]

Thank you very much Frits. The gif format worked but the png format did not. I am using windows 10.

[wobbly]

Here is the cylinder I have sitting on NSR20 MC21 cases.
The reverse stagger is obvious, I will check what casting this came from.

[Martin1981]

Yes indeed, more than 1mm Difference in Port height is obvious. But on my cylinder all Transfer Ports have the Same height (42,2) May be someone ground them. I have to Check.

[Greg85]

Here you go, Greg.

Thanks you Mr frits !! this very good documentation !

[Martin1981]

The first 2 pics show my Cylinder. No Stagger and as you can see nothing has been ground.

Wobbly, thanks for the drawing you posted but there must be something wrong. It says that At BDC piston is approx 0.0mm above bottom of transfer ports. With 54,5mm Stroke and 15mm high Transferports (B and C) the engine can not have 131,62° transferduration.

With 54,5mm Stroke and let us say a 110mm long rod, piston at BDC approx 0.0mm above bottom of transfer ports the Cylinder has to have about 13,3mm high b ports to have 131,62° Transferduration. But the ports are 15(!)mm high. And that makes 140° Transferduration.

[jonny quest]

The cr125 rods are 104mm