Scooterotica

What I found when mapping my race stuff on dyno.
It may not be 100% but its what appeared to happen.
With an off-pipe motor the ignition would require more advance to burn the impure charge. As the motor gets into its stride, the charge becomes purer and will burn faster, hence less advance and one reason why you back off the ignition otherwise the pressure point is too soon and hits the piston and big hole appears as many of you have seen.
You can hold this 'backed off' setting for a while but as the motor revs to off pipe you can advance again as the charge is becoming impure and will need more time to burn. You can achieve 'over rev' this way as long as long as the back cone allows it.
Now there are many other factors involved with the ignition setting from port design,pipe dimensions,head,comp,fuel etc and all this should be taken into account when on dyno. Its no good mapping a bike without load device. Total waste of time. I found that out. Everything changes when the bike is under load rather than just turning a roller.
All these augusto, varitronics ,motoplats etc are ok but not tailored exactly for the application. Its a bit like buying an off shelf pipe and expecting it to be spot on for your bike-its not. its a compromise.

tony wrote:its a compromise.

So is my budget

But interesting info, thanks.

My new motor uses vespatronic which is basically the same as a varitronic. As long as its set to give best all round then great. Mappable stuff is nice but not necessary dan.
You can gain a little withy mapping and I'll look at this with Charlie i'm sure in the future. Charlie doesnt even have a mapped ignition. Just varitronic.

drunkmunkey6969 wrote:

J1MS wrote: TS 1 running at 16 degrees, center plug, Compression ratio at 12.2-1

TS 1 running at 19 degrees, Off set squish, Compression ratio at 9.1-1

Rapido 225 Classic at 18 degrees, Off set squish, Compression ratio at 8.9-1

all timings set using dead stop method, for TDC. Compression ratio's (Head volumes) measured using a burette (very accurate).

Cool, thanks.

And what prompted those particular choices of timing degrees?

prolonged hard fast riding caused pinking at timings in advance of these settings. Each engine was run and then set up according to the way it ran, advancing the timing till it pinked then retarding back till it stopped pinking, then for safety retarding back one more degree. the Rapido was set up on 95 octane and runs well, not fast but reliable, the std TS is my rally going scooter low compression for reliability using low octane fuels (when your riding in europe) as you dont always know what octane fuel will be available.

GT200 (early model)....centre squish....centre plug....CR 8.5 to 1....101 leaded octane....24`....or 1` above standard

No pinking ....no detonation....good fuel economy....good performance....no piston probs.

tony wrote:What I found when mapping my race stuff on dyno.
It may not be 100% but its what appeared to happen.
With an off-pipe motor the ignition would require more advance to burn the impure charge. As the motor gets into its stride, the charge becomes purer and will burn faster, hence less advance and one reason why you back off the ignition otherwise the pressure point is too soon and hits the piston and big hole appears as many of you have seen.
You can hold this 'backed off' setting for a while but as the motor revs to off pipe you can advance again as the charge is becoming impure and will need more time to burn. You can achieve 'over rev' this way as long as long as the back cone allows it.
Now there are many other factors involved with the ignition setting from port design,pipe dimensions,head,comp,fuel etc and all this should be taken into account when on dyno. Its no good mapping a bike without load device. Total waste of time. I found that out. Everything changes when the bike is under load rather than just turning a roller.
All these augusto, varitronics ,motoplats etc are ok but not tailored exactly for the application. Its a bit like buying an off shelf pipe and expecting it to be spot on for your bike-its not. its a compromise.

cracking description mate. just out of interest, what sort of value would the ignition advance back to after the pipe had peaked

My Road bike is a Mugello 225 with Charlie Edmonds 'Fast Road' Tune.

Timing is set at 16 degrees

Why?....... 'cos Charlie said so! And thats good enough for me!

Gnasher, depends on back cone. There isnt much to play with if baffle is steep. My old pipe was a krp5 that Graham made me. I must be honest I've not measured what it was but by cranking 4 degrees up over 500 rpm in it gave nearly 500 rpm overrev. So where the motor would die at 11,000 with say 15 degrees,, at 11,500 ignition is back up to 19 graduated from 11,000 to 11,500 if you get what i mean. So at 11,100 ign might be 16.. 11,200 17 and so on.
I've got all the various maps on this pc but i cant print em to show you- wont let me, poxy thing.

I get what you`re saying and having done a little bit of playing with rear cone angles I can see why igntion timing for overrev might be a better option. shallower cone= more revs but less of a hit in the power. steeper cone=more of a power hit but it can stop dead after peaking. But it seems ignition timing can change this a bit...be nice to have a mappabele ignition that can be changed on the pc, maybe the improvements wouldnt be great but the changes could be made quick and easy.

sorry dan I think this is hyjacking your post a bit

Dont worry about Dan, he loves all this tech stuff.
Yes you are exactly right. I think if the cone was too steep you wont extend rpm range much regardless of the ignition timing. But power is of course better. I would say the idea of the 'over rev' is there if a tail wind comes along when you are in top, you'll gain a few mph.
I think for the track gearing it correctly with the steeper baffle pipe would be the way to go personally. I cant make pipes (i dont even have a workshop anymore) so I've not delved into it too much.