I've had countless arguments with people over this sort of stuff, the video is correct on all aspects of the combustion events that it happens to mention.. One 'professional' 2 stroke tuner on youtube even argued that he was working towards obtaining maximum cylinder pressure at TDC, what an idiot!
Plz tell me load inside the cylinder increases in low rpm or high i can't understand and why ignition should retarded...??? I only know that when the vehicle is in low rpm its normal and when its in high rpm it should advance the spark for to give air fuel mixture a complete time so that it can burn before when the right crank angel is want the power on the piston in high speed.. So what about 1:40 you say i can't understand plz reply...???
@ali qadri The word load or heavy load is the key here if the ignition is advanced at low RPM and heavy load, the overall weight of the vehicle vs the ability of the engine power to mobilize this huge weight, it will ignite before the engine has time to produce torque/HP and the engine will ping or detonate and this is bad for the mechanical components of the engine. If you drive a manual transmission in 3rd gear at 10 KPH and smash the throttle to the floor, you are not going anywhere fast so no need to burn the fuel fast, advanced. Load is part of spark timing and there is a MAP built into the software of modern vehicles to compensate for that. Even in older distributor vehicles, there was a flyweight to do this mechanically, if the RPMs are low the flyweight does not fly outward and does not advance the mechanical timing. Does this help?
@@duanedonaldson2262 That is a load of old waffle! The real reason for changing the timing with the engine load is as follows, when the engine is under heavy load it means that the throttle is wide open, or at least open a large amount, now there are two things (in simple terms) that determine when you need to fire the mixture, one is the engine RPM and the other is the initial cylinder pressure, that is the pressure in the cylinder BEFORE the plug fires, the higher the initial pressure the faster the mixture will burn. So when the throttle is just cracked open the engine can hardly breathe, it is literally being 'throttled', the VE (volumetric efficiency) of the engine is low, the initial cylinder pressure will be low so the timing needs to advance, that's what a vac advance system does, inlet manifold pressure (vacuum) is a good way of determining what load the engine is under, high vac means low load. When the throttle is wide open the engine can take in a full 'cylinders worth' of air/fuel on each induction stroke, the VE is high, the initial cylinder pressure is high therefore the vac system needs to back the timing off because the flame speed will be high, again the vac advance controls this, of course in modern engines the 'black box' controls all of this but for the same reasons that I have stated. 1:42 talks about cylinder pressure and how it affects the flame speed. All of this is to get peak cylinder pressure at the right time in the power stroke regardless of RPM or engine load.
I've had countless arguments with people over this sort of stuff, the video is correct on all aspects of the combustion events that it happens to mention.. One 'professional' 2 stroke tuner on youtube even argued that he was working towards obtaining maximum cylinder pressure at TDC, what an idiot!
Excellent video. Cleared all my doubts about why ignition angle is a function of load and engine speed.
Thank you, interesting graphs etc.
very useful video
Dananjaya Udara
Plz tell me load inside the cylinder increases in low rpm or high i can't understand and why ignition should retarded...??? I only know that when the vehicle is in low rpm its normal and when its in high rpm it should advance the spark for to give air fuel mixture a complete time so that it can burn before when the right crank angel is want the power on the piston in high speed.. So what about 1:40 you say i can't understand plz reply...???
@ali qadri The word load or heavy load is the key here if the ignition is advanced at low RPM and heavy load, the overall weight of the vehicle vs the ability of the engine power to mobilize this huge weight, it will ignite before the engine has time to produce torque/HP and the engine will ping or detonate and this is bad for the mechanical components of the engine. If you drive a manual transmission in 3rd gear at 10 KPH and smash the throttle to the floor, you are not going anywhere fast so no need to burn the fuel fast, advanced. Load is part of spark timing and there is a MAP built into the software of modern vehicles to compensate for that. Even in older distributor vehicles, there was a flyweight to do this mechanically, if the RPMs are low the flyweight does not fly outward and does not advance the mechanical timing. Does this help?
@@duanedonaldson2262 thank you very much .. Love you
@@duanedonaldson2262 That is a load of old waffle!
The real reason for changing the timing with the engine load is as follows, when the engine is under heavy load it means that the throttle is wide open, or at least open a large amount, now there are two things (in simple terms) that determine when you need to fire the mixture, one is the engine RPM and the other is the initial cylinder pressure, that is the pressure in the cylinder BEFORE the plug fires, the higher the initial pressure the faster the mixture will burn. So when the throttle is just cracked open the engine can hardly breathe, it is literally being 'throttled', the VE (volumetric efficiency) of the engine is low, the initial cylinder pressure will be low so the timing needs to advance, that's what a vac advance system does, inlet manifold pressure (vacuum) is a good way of determining what load the engine is under, high vac means low load. When the throttle is wide open the engine can take in a full 'cylinders worth' of air/fuel on each induction stroke, the VE is high, the initial cylinder pressure is high therefore the vac system needs to back the timing off because the flame speed will be high, again the vac advance controls this, of course in modern engines the 'black box' controls all of this but for the same reasons that I have stated. 1:42 talks about cylinder pressure and how it affects the flame speed. All of this is to get peak cylinder pressure at the right time in the power stroke regardless of RPM or engine load.
This blogspot is gone.