KTy

A piece of update, After some software and hardware modification, it seems to work pretty well, all the way ! No more mid-RPM problems ! The other (very) good news is that I (finally) found a dyno near where I live !! :plemplem: So I hope that in the next weeks I will be able to show you some comparative power curves As for the curve, I am currently driving with this one:

Does anyone know why this "Malossi Rosa" is so much powerfull ??? :plemplem: Is the full engine configuration known ? Cheers

:sabber:

Super Geil indeed !! We just need Olli ETS (or anyone) to add a new comparative dyno run !!

Sorry, Is this a cheapest alternative to the PM40 ?

Alloha I know that the charging coil (the green wire) of a PX engine has an impedance of about 110 Ohms. What interest me is the inductance of this coil in henry (H) or milli-Henry (mH). Does anyone have this kind of data ? KTy

@Maniac: I will write a little article ;) The number of point I'm using is unlimited :D (restricted only by memory size). But, that's not the reason because the pink curve is exactly what the vCDI box generates. For this test curve, I have "only" 10 points, but between each points I do a "linear interpolation". For instance, I have 1 point that gives 19° of retard @1500rpm and an another one that gives 22° @2000rpm. Then if the engine revs at ~1620rpm, you'll have ~20° of advance. I'll test tonight a fixed 19° ignition timing to investigate more...

Thanks to this schematic I have updated a little bit my output circuit. It seems a bit better at low rpm, idle is fine, mid and high rpm are smooth. Unfortunatly, the engine still has some "hesitation" from time to time when I'm driving at low-rev / high-load. For instance, when I'm slowing down around 1500-2000rpm in 4th gear, with the throttle almost closed, if I open the throttle little bit (10%) to re-accelerate smoothly, the engine doesn't like it too much... I don't know if it's because I have set too much retard at this rpm and/or because the engine is too lean... Maybe I need a throttle sensor... Here is the curve: EDIT: Now that I see again this curve I am thinking that the problem is maybe that between 1500 and 2000 rpm the advance increase fastly... that's maybe not very good for smooth riding for "street use"...

Sorry for the OF topic... Everytime I see this scooter, I can only dream of something similar... :sabber: This is such a beautiful piece of engineering :plemplem: Is there any picture of the exhaust ? Any dyno graph ? Is this the engine with a special clutch basket with 5 or 6 disks ? Anyway, fantastic :love:

Very interesting ! Just two quick questions; * From these data, would it be hard to compute on each excel sheet the resonant frequency of the pipe ? :wasntme: * Does someone knows how to use excel to draw the geometry of the pipe ? That would illustrate nicely the sheet... Thanks again to share !

Klingelkasper was almost right ! I think the correct schematic for the vespa electronic ignition CDI unit is this one: :sabber: KTy -

You're probably right.... But it's fun to try anyway

Alloha everyone Happy new year Back on topic, Lucifer told me that he gave the opened Ducati CDI discussed in this topic to one of you guys... I was wondering if this person is still online ? I also wanted to know if someone has a schematic of this CDI unit, what really interested me is the input circuit that trigger the thyristor... (Between the red and white wires)... And a little update from my vCDI project; it's still working :D BUT I'm not sure why it's not working perfectly at low RPM... That's why I have decided to finish to rebuild another PX 177 engine to try on this one, as my stock PX 125 engine has an air leak and some carburetor troubles... :puke:

That's the problem... I don't have that much time, working on my sleep hours !

I found why I had some trouble at low RPM... It is now fixed ! It seems even smoother than without ! :love: This is the test curve for tomorrow ! 27° at maximum torque (4000rpm) 16° at maximum power (6000rpm) ! KTy -

Update from this morning... :) When the engine was "cold", it was running great with the above timing curve. Then, after 5-10minutes of normal street driving, little by little, it became more and more difficult to drive at "low rpm", but still doing fine while idling and also at mid and high-rpm... In the end, I bypassed it as it was undrivable for street use. The timing curve I was using yesterday was better for low rpm... So I guess it was too much advance too soon (low rpm)... I will continue to experience ;) And if you're wondering, I have a Chamion L82C spark as it is pretty cold out there and also because I'm focusing on low and mid-rpm...

About MVT, you told me already... I'll try to get in touch with them in January (those French, always on vacations ) You're totally right about the shape of the curve, that's what I read in the literature... But for my old PX that can't peak higher than 7000rpm, I think you don't reach the rpm where you should start to increase once again the advance... And actually, I'm not sure to understand why 18° should be a good advance for "idling" ... and you think that advance can retarded as far as 32° on a stock engine ? Anyway, I'll see how the PX 125 engine (peak power at @6000rpm) feels with this: Thanks for the offer, that would be greatly appreciated (thus I'm pretty sure it will be a long trip to visit you), but right now I just want to make sure that the electronic is reliable... I will look for performance enhancement when I'm sure my circuit is working perfectly ;) Thanks ;) KTy

Out of curiosity, where is located precisely the exhaust temperature sensor ? No Lambda (02) sensor ?

Very very nice indeed :sabber:

By the way, does anyone know if the vespatronic curve is a "good" one ? Anyone want to suggest an ignition curve for a (fucked up) PX 125 ? :)

Well, 100% home made The hardware is quite simple, nothing really "magic" :) A part of the circuit does the detection of the thyristor signal a convert it to a usable 0-5V. There is a PIC microcontroller that computes everything, an RS232 transceiver for data input/output (ebug, curves and firmwareupdate) and a MAX6675 as a thermocouple interface for the cylinder head temperature (Not used yet). There is also a part of the circuit designed to use the AC voltage from the HTCoil and to convert it in a regulated 5V. Besides that, the "difficult" part was to code the firmware because the PIC generate an ignition pulse "one cycle" after the original pulse... This way I can retard or advance the ignition without changing the stator As it is kinda self-powered it was tricky to "start" the PIC, usually you have to kick start two time :D One to charge the coils and condenser, that is powering up the whole circuit and then waiting. And another one to really start the engine... :plemplem: I choose this way because: 1. it was fun to design and 2. I wanted to limit the number of wires to the strict minimum... Just 4 wires, plug'n play and voilà, you've got a vCDI :) Well, I still have to intensively test it, find a better ignition curve (Tomorow I'll try the vespatronic igniton curve) and check if there is some drawback or hidden bugs ;) Another pic ;) Cheers, KTy

Hi guys ;) I'm currently driving my PX with my variable ignition unit I just finished... :) I'm still in the process of "debugging" it, but it's very promising ;) It is fully programmable, you don't have to change the timing on your scooter (good to know if my unit blows off, I just have to unplug it !!), and you don't need 12V AC or any other DC supply... It also handle misfire and (very soon) "overheating" temperature. In the near future, I will add the support for multiple curves selection, and curves and firmware downloads from a user interface... I have also other nice ideas, but very few times... :( The accuracy is very good, maximum error about 1° at 15000rpm. Here are some pics... Here is an example for my PX (stock engine !)... It's a test curve, probably not perfect ! As soon as I have more time I will try to "GSF-dyno"-it (Real dynos are very hard to find here in France... ). Cheers ;)

Yeah, basicaly, with the 2 diodes, the output of the circuit will *never* be more than 600mV, that's a lot safer !! And the condensers are here to filter (along with the resistors) the input signals.

Yes, it's fine :) I was wondering why you did not do it earlier ! Just to mention that V5, V4, R4 (line-in version) and V50, V40 and R40 (microphone version), are only here for simulation purpose, dot not take into account these components ! And by the way, forget about that 1µF capacitor, it's not even on the schematic. I must add that I never tested these schematics, BUT it is very UNLIKELY that it can damage your recorder. If you ever tried Atom007 first circuit with success, this new schematic will work for you

Ok, thanks for all those advices, and you are absolutly right :) I try to find a compromise ! You'll probably smile, my tyres are 100/80-10 Raceman soft, and "it's enough" for me, I mean, I want to have fun both on track and doing some 1/4 miles with the same scooter, and that's the problem ! Of course the best option would be to have two scooters (or at least 2 engines), but for 3 or 4 runs/races per year (The french scene is slowly waking up and I don't have time (yet) to travel to visit you guys... :) ), I'll do with compromise !