Difference in between digital and analogic rotors..HELP
- Thread starter quicksand
- Start date
An analog ignition system will not have a compicated CDI unit typically it will just have a constant degree of advance
for example an Analog ignition system will fire the spark always when it receives the trigger from the stator
but with A Digital system it will calculate a suitable place to fire the spark according to the rpm that the engine is spinning at, so for example @ high rpm it will fire almost at the same time the trigger pulse is received( which means almost 30-40degrees before TDC)but @ low rpm it will wait a short time to fire the spark so as to have a spark at almost TDC
for example an Analog ignition system will fire the spark always when it receives the trigger from the stator
but with A Digital system it will calculate a suitable place to fire the spark according to the rpm that the engine is spinning at, so for example @ high rpm it will fire almost at the same time the trigger pulse is received( which means almost 30-40degrees before TDC)but @ low rpm it will wait a short time to fire the spark so as to have a spark at almost TDC
50cczip racer
Well-Known Member
thats a good explanation but the degree figures are incorrect
a good digital curve will provide up to 38 degrees through the midrange dropping to 16 degrees at peak power rpm then drop straight down to 3 degrees to provide good power past peak that wont fight against the compression and allow good overrev .
there is a particular pvl digital that has this curve that works really well and playing with the hpi programmable creates good results with a similar curve program.
a good digital curve will provide up to 38 degrees through the midrange dropping to 16 degrees at peak power rpm then drop straight down to 3 degrees to provide good power past peak that wont fight against the compression and allow good overrev .
there is a particular pvl digital that has this curve that works really well and playing with the hpi programmable creates good results with a similar curve program.
tiba_karotsu
OVERREV TUNING
i was looking for an ignition timing graph like that, i have this argument with a wise-ass back in our forum & he says for high revs more ignition advance is better & i said bull$hit, with higher rpms you need less advance & now i have proof.
50cczip racer
Well-Known Member
the hpi curve is a good one and is similar to my first post in that it holds 30 degrees through the midrange drops to 16 degrees at peak power revs (11600 std. static timing as graph) and falls off to 0 degrees
the curves work better when you drop instantly to 3 degrees after peak power rpm then gradually to 0 degrees
every curve will work good/bad to suit the application used for and will be subject to setting the static timing to slide the curve left or right along the rpm axis, on 50 and 70 motors between 15 and 17 degrees at peak power rpm is good to aim for dependant on compression ratio/fuel and carb/jetting settings etc
the curves work better when you drop instantly to 3 degrees after peak power rpm then gradually to 0 degrees
every curve will work good/bad to suit the application used for and will be subject to setting the static timing to slide the curve left or right along the rpm axis, on 50 and 70 motors between 15 and 17 degrees at peak power rpm is good to aim for dependant on compression ratio/fuel and carb/jetting settings etc
you explain this very poorly!50cczip racer said:
you make it sound very complicated
the 0 degree point in this graph means a spark @ 30-40 degrees before TDC depending on where you set your stator to
Literally it means a delay of 0 degrees after the trigger is received
and a delay of 30 degrees after the trigger point up to 7,000 rpm
To create maximum power the condition is to create peak cylinder pressure after combustion always at the same crank angle under all operating conditions typically this is 15-20 degrees after TDC.
Also because of the increasing piston velocity at each rpm you need to fire the spark a little earlier each time so that the above condition is met. The combustion process takes a finite amount of time and this is constant for every rpm. And therefore if you can calculate this length of time you can create the perfect ignition timing curve if you can measure this
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50cczip racer
Well-Known Member
???
0 degrees is tdc
the further away from tdc (advanced)you start the combustion process the greater/longer burn cycle
0.5mm btdc is retarded compared to 1.0mm btdc
the closer you fire to tdc the safer the set up
the furthest away the longer burn/more power/more dangerous the set up
eg. malossi ignition reccomended setting 2.25mm btdc as a starting point you would set it safe(retarded)1.5mm btdc and advance up until desired setting found.
0 degrees is tdc
the further away from tdc (advanced)you start the combustion process the greater/longer burn cycle
0.5mm btdc is retarded compared to 1.0mm btdc
the closer you fire to tdc the safer the set up
the furthest away the longer burn/more power/more dangerous the set up
eg. malossi ignition reccomended setting 2.25mm btdc as a starting point you would set it safe(retarded)1.5mm btdc and advance up until desired setting found.
nope that is wrong 
0 degrees is the reference point for the ignition its the trigger point.
with hpi its approx 4mm therfore 4/39.2 *360 = 36 degrees before TDC
and now the CDI knows this point always when it receives the trigger.
At high rpm the spark is very close to the trigger point compared to the spark at low RPM
believe it or not but at high RPm for example 15,000 rpm the explosion actually takes place about 36 degrees before TDC
0 degrees is the reference point for the ignition its the trigger point.
with hpi its approx 4mm therfore 4/39.2 *360 = 36 degrees before TDC
and now the CDI knows this point always when it receives the trigger.
At high rpm the spark is very close to the trigger point compared to the spark at low RPM
believe it or not but at high RPm for example 15,000 rpm the explosion actually takes place about 36 degrees before TDC
50cczip racer
Well-Known Member
thats not what my strobe tells me when i do a curve map with a degree disc mounted on my rotor it shows the ignition firing at tdc/0 degrees at 14,000 rpm and 30 degrees at4000rpm just the same as im reading the ignition curve on the map youve posted
although im maybe seeing it from a practical working point of view and not an electronic standpoint
im merely saying what i see ,iv,e no electrical or electronics knowledge so cant comment on its actual circuitry etc.so ill not argue ,this is just the way i see it working in reality.
although im maybe seeing it from a practical working point of view and not an electronic standpoint
im merely saying what i see ,iv,e no electrical or electronics knowledge so cant comment on its actual circuitry etc.so ill not argue ,this is just the way i see it working in reality.
50cczip racer
Well-Known Member
OK mr aerox
back to the original post
?? which one
on a scooter buy any of them,the cheapest or most reliable
when set up properly either analogue or digital your not going to see a gain big enough to notice
i race 1 scooter with analogue hpi and 1 with digital pvl ive also tried selletra analogue and hpi digital programmable and had very similar results from all 4 when optimised on my dyno.
like said previously
malossi is plug and play / has good availability and reliability and comes with good set up data specific to your engine
back to the original post
?? which one
on a scooter buy any of them,the cheapest or most reliable
when set up properly either analogue or digital your not going to see a gain big enough to notice
i race 1 scooter with analogue hpi and 1 with digital pvl ive also tried selletra analogue and hpi digital programmable and had very similar results from all 4 when optimised on my dyno.
like said previously
malossi is plug and play / has good availability and reliability and comes with good set up data specific to your engine
but think about it logically
why the hell would you fire at 30 degrees at 4,000 rpm?
@ 4,000 rpm one revolution takes 15milli seconds
if you fired @ 30 degrees before TDC @4,000 rpm thats 6.5mm before TDC
doesnt it sound a bit outrageous for such a low piston velocity of 5.24 m/s that means the piston has to travel for 34 milliseconds before it starts to go back downwards
i really doubt that it is the case
the piston would 100% turn around before it reaches TDC if your logic was correct
why the hell would you fire at 30 degrees at 4,000 rpm?
@ 4,000 rpm one revolution takes 15milli seconds
if you fired @ 30 degrees before TDC @4,000 rpm thats 6.5mm before TDC
doesnt it sound a bit outrageous for such a low piston velocity of 5.24 m/s that means the piston has to travel for 34 milliseconds before it starts to go back downwards
i really doubt that it is the case
the piston would 100% turn around before it reaches TDC if your logic was correct
50cczip racer
Well-Known Member
at low rpm the engine is operating completely out of its intended design range
so it requires a boost to improve its operation, providing a bigger explosion provides this at these lower inefficient design rpm levels
just had a quick look through some 2 stroke tuning books i have ,as im beginning to doubt myself now ,they confirm my previous posts as correct
see page 168 A.G.BELL 2 STROKE TUNING (IGNITION)
so it requires a boost to improve its operation, providing a bigger explosion provides this at these lower inefficient design rpm levels
just had a quick look through some 2 stroke tuning books i have ,as im beginning to doubt myself now ,they confirm my previous posts as correct
see page 168 A.G.BELL 2 STROKE TUNING (IGNITION)
