SUGO CDI for Borut... (ignition curves)

[41juergen]

@ Warwick: yes the PJ's are electrical powerd up to when they open and later close again. I did some testing on my RZ some time ago by putting 140 PJ's in and reved it up at WOT. Somewere at 7500 rpm the engine started to bog because of too rich. Below the 7500 rpm the negative pressure was too low to suck fuel into the carb. So for the 3XV / 4DP /4TW and 5KE the point of were the fuel would be sucked in might be different (depending of the air flow and speed) but may be thats the reason the Yam engineers powered them up. At the SP / SPR with 32mm carbs it is not the case...
When you have the -70 than avalible just let me know, my pleasure to test it too. 
Juergen

[stroker3xv]

Jurgens can you explain what you mean by "At the SP / SPR with 32mm carbs it is not the case..."

[41juergen]

If you have a look into the excel file regarding the PJ switching it can be seen that only for the 36mm carbs of the -2 and -5 SP the PJ are closed between 7750 up to 9250 rpm, than opend and than closed again after 11400 rpm. The PJ's of the 32mm carbs (-7 and SPR bikes) are only closed after 11800 rpm (not in the lower RPM range like for the 36mm carbs).

[jools]

 I'll be interested to see if the -70 behaves that way.

Now it has be wondering if using my -9A with the 36mm carbs is a bit of a mismatch.......maybe it has something to do with the rotary type power valves........??

[stroker3xv]

Jools we can swap carbs as I have 32mm with the -80 CDI

[Yuri]

I have a set of 32mm and 36mm with sugo carb internals for both . When my 3xv is dum i will test it

[maccas]

What i find interesting about the powerjets being closed at that early rpm on the 36mm carbs and not on the 32's is that it is the opposite to what I would expect. The air velocity in the 32mm carb will be higher for a given rpm compared to the 36mm carb so it would be more likely that the powerjets start flowing in the 32's.

However, saying that, the bottom end drive on the 93-94 sp won't be as good, so the torque won't be as high. As torque is a product of airflow through the motor, the airflow may be lower in the 32mm carb compared to the 36 on the 91-92 sp.

Anyway i'm just rambling!

Warwick,

My ignition curve is actually very close to the sugo curve as it is (which is a big surprise to me) but certainly got some more options to try on the dyno next time around.

Dan

[Edd]

No dont stop rambling. I am still trying to get my head around this. I am running the 36mm carbs and plan on connecting the power jets. If you shut them off at those rpm's the bike will run leaner? Is the airflow reduced at those rpm's? So you shut the fuel off to prevent the bike from running too rich?

Edd

[zoomzoom]

No guys

Air velocity/ speed increases at the same RPM range if  the diameter is smaller , thats why its the opposite way around on the smaller carbs..If i understand the power jet theory correctly..

[Paul]

On the dyno with my 38 carbs it also surprised me that I had to close the PJ earlier than I would have believed. Else it wouldn't rev out.

[maccas]

Sorry i meant higher in the 32's, i've corrected my post.

Dan

[zoomzoom]

Yip thats correct Paul,

you only need a richer mixture for acceleration once the higher rpm is reached a leaner mixture is aimed for.
Hence the power jets shutting off at high RPM..
I found the same scenario on the dyno with my bike, a richer main jet made less hp on the top, the low to mid range didnt suffer that much
you also dont want to go lean on top either...

Wayne

[Edd]

Aaaaahh! I get it now you are fucked if you do and fuckefd if you dont.

On a more serious note they shut it down then open it again. Paul you only shut yours down at 11000 rpm. Why open it again? That bit is getting me to think there id another reason. What you guys are saying is st the top for over ref.

Edd

[Paul]

On the zeel on is off.

[ybk]

Small correction, the 7K in the original graph was actually the one with the TPS at 0%, whereas the all the others were at 100%. I have made an updated one showing the old 7K and the new one with TPS at 100%. It actually matches the -80 rather closely now which leads me to believe the -80 may be for unleaded actually?