ESE's works engine tuner

[katinas]

Vale: One unhappy IAME RL kart engine piston after an apparent coolant loss.

Attachment 344483

Pistons damage evolution. From dome to skirt.

Add photos: without oil, together with too small clearance for 2618 alloy.

[Frits Overmars]

Drilled the original crankshaft and feed oil in from the drive end. Flettner made me a special big end pin with an oil passage in it.
Attachment 344488

I think I would have used spark-erosion rather than drilling. And I'd choose a somewhat simpler oil path.
But I'm sure that, as always, Neil had his reasons for doing it his way.

[Splatter]

Peewee's cylinder is a HUGE over bored DM from CPI to fit on a Banshee bottom end.Its only real use is for open class drag racing where in Merican terms " bigger is better "
and the cubes overcome all the technical flaws.
My experience with these things is limited to the smaller Cheetah that can have a powervalve fitted.
Its intake is a CR250 that is offset outwards from center line 6mm per side.That reed is way too big for anything less than 120 Hp on petrol so I have fitted a smaller CR125 back on bore center and
picked up a minimum of 4 Hp in a 100Hp setup.
The DM has several good points about it , but would be better with a smaller bore to get somewhere near equal transfer duct areas , and some shape to the inner walls.
it also has replaceable Ex duct outlets , so making them longer and better shaped would be an easy CNC project.

I have been a long time reader of this thread and appreciate the knowledge that people have shared here. The more I think I know about 2 strokes, the more I find out I don't and I have learned a lot here.

I have always pondered about reed cage size and it related somewhat to your post. Did you gain the 4 Hp because the smaller cage was on center line or because of the 250 cage was too large, or both? If you run a 40mm carb with a 125 cage on a 125cc engine, does a 500cc single really need a larger cage with the same size carb? Assuming a properly designed and stuffed 500 size cage, is the increase in the reed opening "curtain" on the bigger cage better or do the larger reeds negate the advantage?

[pete376403]

Does the oil pump have any way of stopping the flow? Centrifugal force is going to suck oil through that passage once the revs come up, whether the pump is running or not

[wobbly]

Splatter , both is the answer.I first tried the smaller cage centered in the reedbox ie off center on the bore, as EngMod analysis showed that the 250 size block had way too much port area for around 100Hp.
The CR125 cage setup was worth 2Hp nearly everywhere , way more in overev.
Then I made offset plates and glued a 6mm spacer down the side to put the small reed back on bore center , as Calvin from CPI had told me the offset reedbox was a mistake in his view.
Another 2 Hp , mainly frontside up to peak.
Win , win along with being able to easily use the RS125 late model straight carb manifold.

[husaberg]

Does the oil pump have any way of stopping the flow? Centrifugal force is going to suck oil through that passage once the revs come up, whether the pump is running or not

It can only deliver what is pumped through due to the way it works
it squeezes the fluid to move it. it has multiple squeezes this a vacuum would only be able to suck one squeeze at a time it basically has a built in non return valve.
Also you can monitor oil flow and slow down the speed of the motor to suit the required delivery, as you can control the speed of the pump precisely.

[Splatter]

Splatter , both is the answer.I first tried the smaller cage centered in the reedbox ie off center on the bore, as EngMod analysis showed that the 250 size block had way too much port area for around 100Hp.
The CR125 cage setup was worth 2Hp nearly everywhere , way more in overev.
Then I made offset plates and glued a 6mm spacer down the side to put the small reed back on bore center , as Calvin from CPI had told me the offset reedbox was a mistake in his view.
Another 2 Hp , mainly frontside up to peak.
Win , win along with being able to easily use the RS125 late model straight carb manifold.

That is interesting. I guess I need to try a CR125 cage on a CR500 and see what happens. Thanks for the reply!

[wobbly]

You have three main variables . The port effective area , the fully open petal curtain area , and the 1st mode natural harmonic of the petals in bending.
The 250 cage in the Cheetah ( VeeForce ) had huge port area , that would drop the intake velocity way too much if going for less than 120 Hp.And the big , long reeds simply could not be configured to get the harmonic correct
no matter what idiotic thickness was input.

[Splatter]

You have three main variables . The port effective area , the fully open petal curtain area , and the 1st mode natural harmonic of the petals in bending.
The 250 cage in the Cheetah ( VeeForce ) had huge port area , that would drop the intake velocity way too much if going for less than 120 Hp.And the big , long reeds simply could not be configured to get the harmonic correct
no matter what idiotic thickness was input.

Is it easier to get the harmonics right with a shorter reed? On a large engine like a CR500 would it be better to use a wide but short reed cage more like a 100cc kart cage since there is plenty of room to work with in the cylinder? Assuming you could get all port area and petal curtain area numbers correct.

[MotleyCrue]

Anyone know about how much power gain is typical when switching from gas to methanol ? 10-15% more power if the exhaust pipe is not changed, just fuel flow and timing ? 15-20% if the exhaust pipe is corrected too ?

[husaberg]

Anyone know about how much power gain is typical when switching from gas to methanol ? 10-15% more power if the exhaust pipe is not changed, just fuel flow and timing ? 15-20% if the exhaust pipe is corrected too ?

Bell says

An engine burning methanol will usually show a 6-8% power increase over one
running on Avgas 100/130 (i.e., Racing Fuel 100), without any change in compression
ratio. With the compression ratio increased to its maximum, power can rise as much as
15-17%.

I say if it has poor cooling ie air cooled it will keep a higher output for longer, IE it not does fade after a few minutes or seconds.

[F5 Dave]

My experience is limited to dynoing a Norton. With the pilots too big (removed) it was cooler than a big chunk of metal had any right to be. For a thermally unstable bike that has to be an advantage. It was also toxic and you couldn't stay in the stall for long. With drilled out pilots fitted it ran hotter but still worthwhile and far more pleasant to be around. I mean, apart from the horrible noise.

[wobbly]

We did the reverse of this years ago , having to change from Meth back to petrol ( Avgas ).
On Meth it was at 18:1 compression , no extra advance anywhere , and made 48.5 Hp ( 125 TM - MX engine )
Changing back to AvGas I dropped the com to 15.8 , lengthened the pipe 15mm in the header and 15mm in the mid ( then later built a better pipe ).
Best advance curve again was as it was previously.
This setup made 43 Hp but had nowhere near the mid power , and had lost alot of overev.
I wound in some mid avdance , but this had no effect , and the only way to get the overev back was to fit a solenoid powerjet that stopped the carb
going rich over the top of the pipe.
Obviously the Methanol didnt mind going rich and kept on reving hard.
Lengthening the pipe pulled up the mid , but lost even more overev.
So the final result was a loss of 5 Hp in 48.5 = 10.3% but the real penalty was the powerband width.

[Flettner]

I think I would have used spark-erosion rather than drilling. And I'd choose a somewhat simpler oil path.
But I'm sure that, as always, Neil had his reasons for doing it his way.

yes its simple,I dont have a spark eroder.

[Flettner]

Does the oil pump have any way of stopping the flow? Centrifugal force is going to suck oil through that passage once the revs come up, whether the pump is running or not

In my system, air is constantly being drawn through this hollow crankshaft, oil is delivered to this airflow at the crank intake. Air is supplied from the airfilter. TPI does not care if there is what would be effectively an air leak with a carburetor, makes for rapid oil delivery to the bigend bearing on load.