[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked)

Nombre de messages : 28 Localisation : Slovenia Date d'inscription : 19/03/2012

What about too much ignition advance? What ignition do you have?

ignition is HPI ineerotor from stage 6, advance was set as was recomended in manual for ignition. but i´m thinking if is in manual ideal advance for 70ccm (47mm bore) in 40mm bore can be advance lower. Am I thinking good?

koenich a écrit:: this is for sure the best version. but it also raises the timings...which is not always good.

shure... you must implement this without change the diagrams Wink

Nombre de messages : 28 Localisation : Slovenia Date d'inscription : 19/03/2012

alcatelko a écrit:: ignition is HPI ineerotor from stage 6, advance was set as was recomended in manual for ignition. but i´m thinking if is in manual ideal advance for 70ccm (47mm bore) in 40mm bore can be advance lower. Am I thinking good?

Yes, probably that would be a bit better, but I don't think the required difference in ignition advance between a 47 and 40mm could cause such damage.
Looking again at the pics, I have an other idea, perhaps the head wasn't seating properly on the cylinder. I noticed a few times that the centering system from malossi is badly machined and prevents the head to be pressed properly against the cylinder.

roost a écrit:: Looking again at the pics, I have an other idea, perhaps the head wasn't seating properly on the cylinder. I noticed a few times that the centering system from malossi is badly machined and prevents the head to be pressed properly against the cylinder.

you're right

at first we will try align cylinder and head at the lathe, if it will not be good we try rebuild head.

Nombre de messages : 60 Localisation : australia Date d'inscription : 01/06/2012

I am running the exact same setup as you, except I have a roost exhaust and msd ignition system the bike run like this for 24 hours straight and didnt give an issue. Im thinking your a unwilling recipicant of mallosi bad casting.
I had to go through my malossi cylinder as well to fix there casting flaws

roost a écrit:: What about too much ignition advance? What ignition do you have?

And what fuel is used?
That can also cause these problems.

I think it is clear that the motor is detonating but the area of detonation damage on the sealing surface of the cylinder is a concern. It appears that the combustion chamber diameter might be larger than the bore size – is this the case?

Regards
Allan.

Nombre de messages : 44 Localisation : Portugal Date d'inscription : 08/11/2011

Holy mother of detonation!!
Are you sure that in the periphery of the combustion chamber the squish is really 0.5mm, is that with hot, or cold engine?

squish is measured on cold engine...same squish we use on all our engines. and only this one have problems...maybe is this one cylinder bad Very Happy

but the performance of this engine is very good Very Happy

HI Jan and Frits,
I have been looking at the Zeeltronics programmable Ignition and they have a feature on one of their units that reduces the spark energy just before peak torque to gain power. I am struggling to understand what this feature does as it seems to me that you need max energy at this point. Here is the details Borut from Zeeltronic was good enough to send me.
Can you shed any light on this phenomenon please?

Zeeletronics - We made programmable spark energy, because some customers told about possible power gain when spark energy is reduced at the top revs.
Spark energy should be high before top, but about 500rpm before top power rpm, spark energy should be decreased.
Spark energy is programmed same way as ignition curve. Spark energy changes linearly between programmed points.
Too weak spark is also not good. I think spark energy effect on burning speed.

Thanks and regards
Allan.

I expect that spark energy will effect the time delay between the spark occurence and the first appearance of noticeable combustion.
Once combustion has started, the burning speed will not be influenced by the spark energy, but the net effect may be that the end of combustion is moved further past TDC, so it may look like the burning speed was lower.
I imagine this effect will be comparable to a later ignition timing which can be beneficial at high rpm.
But even then I would prefer the strongest spark possible and find the optimum ignition timing to match.

Thank you for your thoughts on this situation Frits.

......but it works.

Institute of TwoStrokes a écrit:: ......but it works.

In which case I'd like to know all about it.
I've heard it mentioned before but nobody could or would come up with an explanation. Would you be so kind?

Hi Jan and Frits.

Now, before taking a cylinder off for inspection I pull hard to the third or fourth gear and then shutdown like I am going to make a plug check, so the piston and plug can be readed better. I also start to notice in my engine that the exhaust flange is wet..... Other engines, and previous versions of mine the flange is dry.

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What could it mean? Too strong diffuser for my setup is making a lot of short circuiting?

Thanks

Frits Overmars a écrit:

Institute of TwoStrokes a écrit:: ......but it works.

In which case I'd like to know all about it.
I've heard it mentioned before but nobody could or would come up with an explanation. Would you be so kind?

At this point nobody can explain it fully, your and Borut's theory seem to be close, but the effect can be measured. It was all discovered by accident where a German tuner noticed that he got a improvement in HP in the last run just before the battery went flat(running total loss), the figures with a fully charged battery could not be matched from that of the flat battery. A TZ250 owner in Holland was the first to try the new ignition and got a 4HP in increase with and extra 500 rpm over rev, all by decreasing the spark strength over 12,000 rpm. The TZ250 owner contacted Borut after he found it written in the TZ250 5KE manual that 'spark strength is decreased after 10,000 rpm'. Yamaha must have thought there was something to it. I'll ask the TZ250 owner if he doesn't mind me posting the dyno graph.

I am by no means an expert about ignition technology.
But what i have to say is this.
Electric energy produced by a coil is all a mater of watts going in.
P=UxI when u (volts) decrease I increases to maintain P. (R stays the Same)
I think contrary to the statement energy is reduced actualy it is increased.
Joules is the only way to determin the energy given from ignition power.

Just my two cents

Sander

May be, at high rpm the ignition have not enough energy, by reducing the ignition strength or length, there is perhaps more time to the capacitor to refilled ??? (a bit like modifying the dwell %age) ???

Institute of TwoStrokes a écrit:

Frits Overmars a écrit:

Institute of TwoStrokes a écrit:: ......but it works.

In which case I'd like to know all about it.
I've heard it mentioned before but nobody could or would come up with an explanation. Would you be so kind?

At this point nobody can explain it fully, your and Borut's theory seem to be close, but the effect can be measured. It was all discovered by accident where a German tuner noticed that he got a improvement in HP in the last run just before the battery went flat(running total loss), the figures with a fully charged battery could not be matched from that of the flat battery. A TZ250 owner in Holland was the first to try the new ignition and got a 4HP in increase with and extra 500 rpm over rev, all by decreasing the spark strength over 12,000 rpm. The TZ250 owner contacted Borut after he found it written in the TZ250 5KE manual that 'spark strength is decreased after 10,000 rpm'. Yamaha must have thought there was something to it. I'll ask the TZ250 owner if he doesn't mind me posting the dyno graph.

I asked Borut, I can post the dyno graph.
You mean this:
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Now Borut should add more features and has to work to make them usable on other bikes.
I asked to have one of these new CDI for my bike to try them.

Just a thought: could it be that the weakening of the spark is accompanied by a longer duration of the spark?

Frits Overmars a écrit:: Just a thought: could it be that the weakening of the spark is accompanied by a longer duration of the spark?

If this is the case how do you think this improves the power production?
Once ingnited the mixture starts to burn from origin towards the outer boundries in the cilinder.
Longer spark duration doesn't seem to be of use because the mixture near the plug is already dead mixture.

You have more data about the combustion proces from past testing is this true?
Or does the burning of the mixture initiate so much turbulence that there is still live mixture around the sparkplug?

Sander

My sketchy understanding of arc propagation is that once you reach the potential needed to ionize the gas between the electrodes, the resistance drops by a couple of orders of magnitude and the current is limited by the plug cap resistance and the coil secondary. So assuming you still have enough voltage to start the arc, less energy would mean a shorter duration.

Hi Guys

The "BLUE" curve is 100% spark power at all rpms
The "RED" curve is at 100% spark power to 12,000rpms and the 50% beyond that.

So why didn't the dyno operator maximise both the red and blue curves to give the best (and obviously equal) results up to 12,000 rpm?

I'm not saying there is nothing in this . . . . . .but

Perhaps I should point out that I am a big fan of the Zeeltronic ignition, that Borut has just supplied me with 10 ignitions with reduced features and smaller casing to suit our British Superkart regulations and that I too have asked for a "spark energy programmable box" once available to suit my requirements.

Best Regards

Ian Very Happy

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