ESE's works engine tuner

[F5 Dave]

Helmet mounted gopro must be worth -0.78kph.

[Frits Overmars]

... if you gear for max safe RPM in top on the back straight at Willow Springs in the morning when the air is still, you may find yourself closing the throttle some in the afternoon to avoid floating the valves if (very likely when in the spring) a 20-35 mph tail wind comes along out of the west.

'Closing the throttle some' may weaken the mixture because the needle will take over from the main jet. Sit up, stick your knees and elbows out, feather the front brake (that's what the MotoGP-jockeys do in order to put some more heat in their front tire) but whatever you do, do not roll the throttle back.
Two-strokes simply run out of breath if revved too high. so unless the gearing is way off, they are self-protecting, unlike some other contraptions I could name.
By the way, what 'floating' valves were you talking about Michael?

[Frits Overmars]

I could remove fan and cowling but cylinder head fins are to small for this move.

Your last picture showed engines with normal, unblown cooling fins. Isn't that allowed? And what about fitting a Tomos A55 cylinder? I think it looks quite promising, maybe even better than a Kreidler cylinder.

[yatasaki]

Yep Frits, best aluminium tomos cylinder so far BUT, guy behind me (with the camera) has that cylinder and 50 cc, Slovenians claiming to extract 9 hp with dellorto sha14/12, and you can really see these 9hp on track. While I'm using a35 cast iron cylnder which is 60cc on my bike and can be bored to 46 bore (70+cc). Trick is to convert a35 cylinder (which is having to small Reeds)to piston induction.
More cc and square-easier power getting ..AND a lot of material and space for transfers and exhausts.
That a55 cylinder is on my bench right now as a 2nd engine, preparing for 4h endurance.

[guyhockley]

Laser honing

https://www.gehring-group.com/en-ww/laser-honing

It says: "the laser structuring of the cylinder is currently applied in the range of the upper piston reversal point." In the picture it looks like the right hand cylinder has been treated to a greater depth than the one next to it, where the pattern seems to stop without going full circle.

[F5 Dave]

Reduction in oil consumption
Improvement in emissions
Reduction in friction
Reduction in wear


Well the top one sounds useful. All my 2 strokes seem to use a lot of oil

[jamathi]

Plenty of work has already been done on this with no good results.
Firstly Jan filled in under the Ex duct to reduce the coolant flow - result deto city.
Secondly, I ceramic coated the duct inside surface , result lost power - deto city.
Third,Franco at TM tried the air gap shell idea, result - deto city.
Fourth,TM originally designed the KZ10 with all the coolant flow entering the cylinder under the duct.
This heats up ALL the water ,including that flowing over the transfer tops.
They later plugged the holes and directed all the water into the cylinder , from the side over the top of the duct.
This gave better power.
Lastly I bored a hole into the water jacket above the boost port , so all the cold water flowed over the transfers first.
Then added two 3mm holes thru the plugs under the Ex duct to help cool this area separately.
Result just over 1 Hp in 48 , with alot less deto level when under full power.
But the CIK and NZ techo guys would not allow this " additional " water circuit.
Moral of the ( long ) story is that cooling the duct first is bad , as is not cooling it at all , as you must keep the retained
mixture in front of the piston as cool as is possible to prevent the returning stuffing wave from pushing hot gas back into the cylinder.

Hello Wayne

Does the TM have a mechanical water pump, or is it rear axle driven?
And what do you use on your dyno?
There may be a big difference in the water circulation speed between TM and RSA.
On the RSA the pump from the 250 was used.
It caused some power loss, but the net result was still positive!
The circulation speed was very high

[Frits Overmars]

Wob, here are the dimensions of the Rotax-129 impeller as used on the Aprilia RSW125, and the Aprilia RSW250-impeller as used on the RSA125,
that circulated 60 litres per minute.

[husaberg]

Wob, here are the dimensions of the Rotax-129 impeller as used on the Aprilia RSW125, and the Aprilia RSW250-impeller as used on the RSA125,
that circulated 60 litres per minute.

Compared to the sound of a swarm of angry bees sound effect you get with the 65/85/125 MX classes here in NZ
The popping and Banging and farting the 250 and 450 Fours stroke MX make as the run on and off the limiter on the start line and over the jumps is hardly melodic

nice pump pics BTW

[wobbly]

Hello Jan, the karts use an axle driven pump , and we use a radiator area ( with an extra unit behind the seat ) sufficient to keep the engine at a max of 40* on the hottest day.
Going colder on the dyno has no effect on power - but does lower the background deto level a small amount.
The dyno has a programmed controller that heats the water to 30* , and then switches a big fan that keeps the water at 40* during a test.
The heat soak and then the temp rise time is sufficient to get the case/crank/gearbox/pipe up to working temp after about 6 all gear WOT runs.

[jamathi]

Hello Jan, the karts use an axle driven pump , and we use a radiator area ( with an extra unit behind the seat ) sufficient to keep the engine at a max of 40* on the hottest day.
Going colder on the dyno has no effect on power - but does lower the background deto level a small amount.
The dyno has a programmed controller that heats the water to 30* , and then switches a big fan that keeps the water at 40* during a test.
The heat soak and then the temp rise time is sufficient to get the case/crank/gearbox/pipe up to working temp after about 6 all gear WOT runs.

Very good system Wayne!
Testing at 40° gives 1-1,5 HP more than the 53° we used at Aprilia.
That is what we saw when testing from 90° to 40° with 5° intervals.
Why more than 50° on track was preferred by Mr Witteveen I don't know.....
I think he was afraid of 'cold seizures'
He considered a piston clearance of 0,04mm as VERY important.
But when I tried 0,06mm the engine gave more power!
I did this without telling anyone, as it was seen as pure heresy at Aprilia…..
Of course, after only one training session, piston clearance was 0,10-0,12mm.
So they kept changing pistons….

[jamathi]

Wob, here are the dimensions of the Rotax-129 impeller as used on the Aprilia RSW125, and the Aprilia RSW250-impeller as used on the RSA125,
that circulated 60 litres per minute.

Hello Frits,

I don't remember if the water circulation was 60 or 160 litres per minute....
As those tests were done at Aprilia while I was still working at DERBI
In any case an electric pump was FAR insufficient with 20 litres per minute!
For a 125cc single.
I have no idea of the water circulation of a rear axle driven water pump.
But you CAN have insufficient cooling with a 40° water temperature I think.
You have to measure the temperature when the water goes into, and comes out of the cylinder to be sure.
The difference should be minimal.

[TZ350]

it´s my two stroke bike with speeduino https://youtu.be/zk55HR6bgO0

Great fuel injection project, I like it..... .... looks like more and more people are trying their hand at 2S EFI.

[Frits Overmars]

Hello Frits, I don't remember if the water circulation was 60 or 160 litres per minute.... As those tests were done at Aprilia while I was still working at DERBI. In any case an electric pump was FAR insufficient with 20 litres per minute for a 125cc single. I have no idea of the water circulation of a rear axle driven water pump.

I hate rear axle driven water pumps. While you are on the starting grid, revving the engine, waiting for the flag to drop, there is no water circulation at all!
Kart engine manufacturers know that too, of course. They supply engines for amateur drivers with an engine-driven pump. So it is al the more surprising that their six-speed competition engines have no pump - with one exception: the DEA KZ125 from our friend Andrea degli Esposti. He's also the only one until now with a balance shaft in that type of engine.



Anyway, just look at the way many pumps are driven from the rear axle: with two O-rings. No way can you transmit enough power that way for sufficient pumping.

But you CAN have insufficient cooling with a 40° water temperature I think. You have to measure the temperature when the water goes into, and comes out of the cylinder to be sure.
The difference should be minimal.

Agreed. And even then things can go wrong.
I remember a Dutch tuner praising an aftermarket cylinder head set with insert and cover: "the water stays 6° cooler, so cooling must be much better".
I pointed out that the water stayed so much cooler because most of the insert's outer surface was shielded from the water by the head cover.
In other words: the head insert hardly got wet (a problem that still exists today with many of those aftermarket heads).
When he did not immediately get my drift, I pointed out that the water would stay even cooler if it was not pumped through the engine at all...

[katinas]

[QUOTE=Frits Overmars;1131123365] the DEA KZ125 from our friend Andrea degli Esposti. He's also the only one until now with a balance shaft in that type of engine.


Hi Frits, interesting whether the whole cooling liquid enters the cylinder from 'under exhaust' side on this engine. Very nice additional cylinder clamping bolts, but sometimes on multi cylinder engines there is no space to do this.

Looks, that Honda used small cooling hole through narrow EX divider on late Aoyama cylinders and maybe last NSR 500.