redcesar

Hallo,

Have someone of you maybe experience with the new MVVS ICU-P ignition? You can set differend curves and 2 differend exhaust systems, hase somone experience in practice?

Cesar

Antique

My Feedback: (4)

Why is a curve necessary ?
99.9% of all engine users can't tell and/or don't care where the timing is set, as long as it starts and flies the plane...
C&H ignitions can be programmed for 4 different settings..20 or 26 degrees of total advance, full advance at either 4000 or 6000 rpm....Default is 26 and 4000 thousand...Pretty hard to tell any difference either way...
Ask TKG now many they make that are NOT set for 26 and 4000

rmh

Since you asked --
on a very light model - carbon fibre perhaps with a tuned silent system - the midrange can be a problem for a lot of the precision aerobatic sequence.
And even I can tell the difference -
for a lot of flyers tho - -it really is of no consequence.

pe reivers

An engine can run very well if fully advanced between 4000 and 6000 rpm. If it runs in excess of 7000 rpm, the ignition must be retarded again due to increased squish action (combustion turbulence) The engine will run much smoother if it has the appropriate advance curve. Powerwise it may not be noticed easily, but the engine will vibrate less.

Antique

My Feedback: (4)

I guess it's a compromise, when the spark is retarded from 28 at WOT the rpm goes down...
Your choice, max rpm or slower and smoother...Will have to try it some day....

rmh

On my high revving tuned pipes -on 50cc-I have to hold back timing a little -it INCREASES revs (over 8000)

pe reivers

In my 50cc Kreidler racer I also had to retard timing to 0.9mm btdc (stroke39.5mm, rod length ~60mm) Standard timing on the Kreidler was 1.2mm for 7000 rpm max. operation
After mods, usable rpm range was 9000-13000, Beyond power peak at ~12000 a steady power decline towards 16000 rpm.

redcesar

Okee, thank you for the answers, but has someone experience in practice with exactly this type of ignition MVVS ICU-P in combination with the MVVS116

How das it act with the automatic choke? And the choice you can make for a short silencer or a long silencer, is there a great difference in use?

Cesar.

pe reivers

MVVS obviously has tested their curves with in cowl mufflers (short) and canister mufflers (long) . They did not test with tuned pipes as far as I know, because when over at my place, their CO was very interested in my 58cc tuned pipe tests.

As for the choke servo, it is actuated below a treshold rpm, and has an rpm range from fully open to fully closed.
Object of this system is to allow leaner idle mixtures and still provide excellent starting. Should the engine sag when throttling up, there comes the choke to the rescue before the engine stops. At least that is the idea. Also, the engine will start right away without the "stopping rich and start again" procedure.
It remains to be seen how this functions with engine hot.

There are not many 116 users out there, so I think there will be but sparse response.

rmh

MVVS /Evolution really should define the uses of the new ignitions more clearly
naughty naughty-
The previous 4.8 setup works very well and on the factory cans
initial start new is a problem as the dry Walbro 27 carb will not pull hard enough to choke - because there are two large air leaks in the choke plate - once the carb is wet - all ist fine.
the best curve on the new ignitions - -- I bet you can count on one hand how many users figure that one out -
I am sure it works tho--. Maybe you can coax MVVS into releasing a very simple setup sheet for this device.

pe reivers

I think the timing curve is an academic problem. I am sure when put on a dyno, the power curves will show up differences, but I am not so sure a user will notice it. In the small 50cc cylinder sizes even a fixed ignition works excellent.
In my book, this is a no-worry issue.