ESE's works engine tuner

[JanBros]

2Stroke Stuffing going from the very large rotary valve crankcase volume that a RV enjoys to a much reduced CC volume that a reed valve likes to have.

you can not dyno an engine with the variator opening in the powerband, as the speed of the dyno will rise but the rpm's of the engine do not. this means the final transmission-ratio is changing while dynoing and effects the powergraph. it is very difficult to read anything good out of the chart.

I do it with the variator blocked in a certain position that makes the dynorum long enough. so he should do just like that.
when the engine is setup properly, than I free the variator and adjust weights, clutch-springs etc so that I achieve the highest rpm of the dyno in the shortest amount of time, the ouput numbers don't mean shit at that moment, only the time matters.

solid line is the engine with blocked variator (about halfway), dashed line is after vario etc was properly setutp (don't read much in the numbers, it's a Honda Sky for moped-MX, max rpm about 9000-9500, HP I don't know, I only compare)



as you can see , the engine is suddenly capable a revving nearly 3.600 rpm higher, which of course is not possible. it's because the engine's rpm is calculated from the dyno's rpm.

[JanBros]

CR1000

[senso]

Thanks guys, i'll take a look.
This is what i'm working on: a 50cc Cagiva Prima racer.
This prototype reed valve is made to fit an Ibea 30mm carb on it, which has a 33,5mm exit diameter. It's a little bit large but i tried to arrange an acceptable internal duct.
This engine already has a nice inlet shape, and was born to also fit a 75cc so it has a 47mm large crankcase (bigger than a Minarelli or Derbi).
The cylinder base is with external studs so it's been possible to design a cylinder with proper transfer ducts.

Hi, this is most likely old news to you, but that cagiva engine seems pretty similar to the engine used in the Yamaha LCDE 50cc bikes, and if it is indeed an LCDE engine, then there are lots of parts for that engine, there is also a YZ80 big bore kit from Athena that also bolts on to the crankcase, and lots of long stroke cranks in Portugal for those engines.
You can also get a clutch basket from a DTR 125 and make it fit, or just turn the plate(most likely wrong name in english) and you can fit an extra clutch disk, DTR125cc metal clutch disks are around 0.5mm thicker, and thus give you a better cluch(a bit more clamping force, a little bit more wear resistance).

The 75cc version of that engine only lacked in the fact that the stock exhaust port was an oval, without much meat on the casting to do some exhaust aux ports..


Best regards, and sorry if I'm wrong.

[Gradella23]

Hi, this is most likely old news to you, but that cagiva engine seems pretty similar to the engine used in the Yamaha LCDE 50cc bikes, and if it is indeed an LCDE engine, then there are lots of parts for that engine, there is also a YZ80 big bore kit from Athena that also bolts on to the crankcase, and lots of long stroke cranks in Portugal for those engines.
You can also get a clutch basket from a DTR 125 and make it fit, or just turn the plate(most likely wrong name in english) and you can fit an extra clutch disk, DTR125cc metal clutch disks are around 0.5mm thicker, and thus give you a better cluch(a bit more clamping force, a little bit more wear resistance).

The 75cc version of that engine only lacked in the fact that the stock exhaust port was an oval, without much meat on the casting to do some exhaust aux ports..


Best regards, and sorry if I'm wrong.

hello senso,
i saw the yamaha lcde engine, it looks similar but it's not quite the same. Mine is a Cagiva made engine, and i don't think i can adapt much spare parts, except for maybe a derbi crankshaft (but it will need some lathe adjustments to fit on the clutch side.)
anyway i'll do everything by myself so problem solved!

the clutch from the 75cc version already has 5 discs so i think it will be enough.

[TZ350]

you can not dyno an engine with the variator opening in the powerband, as the speed of the dyno will rise but the rpm's of the engine do not. this means the final transmission-ratio is changing while dynoing and effects the powergraph. it is very difficult to read anything good out of the chart.

I do it with the variator blocked in a certain position that makes the dynorum long enough. so he should do just like that.
when the engine is setup properly, than I free the variator and adjust weights, clutch-springs etc so that I achieve the highest rpm of the dyno in the shortest amount of time, the ouput numbers don't mean shit at that moment, only the time matters.

solid line is the engine with blocked variator (about halfway), dashed line is after vario etc was properly setutp (don't read much in the numbers, it's a Honda Sky for moped-MX, max rpm about 9000-9500, HP I don't know, I only compare)



as you can see , the engine is suddenly capable a revving nearly 3.600 rpm higher, which of course is not possible. it's because the engine's rpm is calculated from the dyno's rpm.

We set our CVT engine up on a rolling road dyno (Dynojet) and graph power against road speed. This is a little four stroke engine in a sidecar for racing on Go Kart tracks. Springs, weights and rollers adjusted to get a flat power curve over the widest speed range possible.

[SwePatrick]

Simple easy question:

What was the average weight of 250gp bikes during the latest years?

Rgds
Patrick

[porttiming124]

Hello everyone. Do you think it's better if the end of the stinger is sharp or with a radius?
If I look at the exit of the yamaha motocross silencer there is a lip just a bit before the exit.

[Gradella23]

hello guys, little update, almost ready to melt some aluminium....

[katinas]

Simple easy question:

What was the average weight of 250gp bikes during the latest years?

Rgds
Patrick

Hi, Patrick

From 2002 to 2009 weigh for 250 GP class, min. 100kg.
From 1992 to 2001 - 95 kg. and before 1992 - 90 kg.

Re Stinger or silencer exit

Hi, yes interesting question.
After reflected wave from revers cone travels backwards to the cylinder, the step at the end of the silencer restrict reverse flow from atmosphere and maybe this could delay returning time and weaken puls in comparison with rounded silencer end. But with a such small step, maybe no difference at all.
Say, the most restricted revers step could be a reed valve at the end of the silencer, without possibility for revers flow from atmosphere. It would be more clear comparison.

[wobbly]

Regarding the muffler exit geometry.
Now we have reliable code that can show the effects of the waves bouncing up and down the stinger , it became obvious to me that when the exiting wave front hits atmosphere it changes sign.
This negative pressure ratio then arrives back at the rear cone exit and can have a destructive interaction with the high pressure positive ratio being produced by the reducing cone area.

Thus the idea was tried ( initially being invented by Helmut Fath ) of a smaller diameter nozzle ,at the rear cone exit , that stepped up to the main stinger tube ID - where instead of having a smooth nozzle exit
into the main tube we had a step.
This step helped reduce the return waves amplitude and thus its effect on the main wave action within the pipe.

The dyno says yes please, and thankyou Neels.
I have never tried it but I will put a multi angle radius simulation on a stinger end and see what happens in EngMod.

[porttiming124]

ok thank you Woobly

[skako]

hello guys, little update, almost ready to melt some aluminium....

That looks great. Is the core made in the CO2 process?

[Gradella23]

That looks great. Is the core made in the CO2 process?

the core is sand 3d printed by voxeljet. I've built the outer core boxes with 3d printed plastic models screwed to the wood box

[SwePatrick]

Hi, Patrick

From 2002 to 2009 weigh for 250 GP class, min. 100kg.
From 1992 to 2001 - 95 kg. and before 1992 - 90 kg.

Nice!
Thank you.
I managed to get my Tz/Tzr project to 78kg so far.(no front fairing)
I have been obsessed this winter with trying to shave weight off of everything.
I´m aiming at 75kg´s(it´s becoming hard now)
Already bought every bolt and nut in titanium and aluminum
Exchanged all steel available on chassis to aluminum.
Lighter wheels and tires
Cut away unused brackets etc etc.

78kg´s is a success so far =)

[katinas]

Nice!
Thank you.
I managed to get my Tz/Tzr project to 78kg so far.(no front fairing)
I have been obsessed this winter with trying to shave weight off of everything.
I´m aiming at 75kg´s(it´s becoming hard now)
Already bought every bolt and nut in titanium and aluminum
Exchanged all steel available on chassis to aluminum.
Lighter wheels and tires
Cut away unused brackets etc etc.

78kg´s is a success so far =)

78 kg weight with 250 cc two cylinder, impressive, it's completely on the edge.
With such a low weight, wheels/ tires/ brake discs, must be extra light, otherwise, softer springs in harmony with 78 kg will not be able to work with normal 250 wheels and tyres. Or if you leave the standard springs, the suspension will be very hard. The closest would be 125/moto3 wheels and tires.
Very light carbon brake discs can be made inexpensively from F1 brake discs from ebay (I bought few discs with pads for £50 per disc). After cutting one disc in half, you get two discs with a maximum thickness of 9 mm. Only needed to make the inner part of the brake disc from magnesium. Four lightweight carbon brake pads can be made from one F1 pad.