ivymike,
I apologize for misinterpreting the question of why CI has more torque then SI. Of course if you could have the same pressure under the curve and all other things are equal, they should be the same --- but in the real world they are not and that is why diesels have more torque. I...
ivymike,
“What, so cylinder volume varies independently of crankshaft position? Bull-oney.”
It’s not the cylinder volume per se, it’s the pressure from the combustion process that can be different i.e. CI verses Si. The same principal applies to why diesel have more low speed torque by...
Look the original post was about why CI engine have more torque then SI engines. I used the constant volume verses constant pressure PV charts as why this can happen. I am not selling instant torque; I used it in an attempt to depict the dynamic pressure changes laid over the dynamically...
SomptingGuy
Apparently there is some kind of semantics going on here regarding the word leverage. Whether you like it or not, the crankshaft is in fact a lever arm --- but you can pick the word.
Regarding rod/crank kinematics & BMEP being one size fits all, why do you think that instant...
Go into any tech book and look at the PV (pressure Volume) chart of a spark and compression engine. Spark engines are called constant volume because the combustion time and/or energy release time is quicker. Compression engines are called constant pressure because the combustion time is slower...
There is a finite equilibrium between air fuel ratio, ignition timing and combustion speed or mass factional burn/energy heat release. You can burn a piston in one engine with say 1.1 air fuel ratio but not burn it in another engine, the initial combustion timing, and the combustion speed being...
I know it is counterintuitive to think that more fuel efficiency can be had with higher RPM when all things are equal via increase fiction and aero. However, using two examples of 2,000 to 3,000 engine RPM at the same cruising speed, there are significant food for thought to be considered...
I read this post with great interest and my opinion on the possible cause is based on the following assumptions; the stroke is in the 375 to 400 MM range and the fuel injection on time is in the 8 to 12 millisecond time frame. The great photos show the injection pattern on the top of the piston...
I believe what you are looking for is how to calculate the higher altitude compression PSI from sea level. Because of the huge variables of things like heat lost and starting ambient air density etc. I recommend that you simply use a perfect gas and adiabatic approach, as they should apply to...
I’m sorry that when I said relatively constant, I didn’t mean from idle to full power. I meant at a fixed throttle position and fixed volumetric efficiency wherever you select to test it at. The point I was trying to make was that piston speed increase proportionality to RPM but the burn time...
There are so many, many variables in the combustion time or mass faction burn rates i.e. low load and/or low RPM that lacks efficient savaging included EGR dilution, lean or rich air/fuel mixtures, hot or cold operation conditions, high or low octane, early or late intake valve closing...
Like in most all things, too much turbulence is not good either, as high turbulence will centrifuge the fuel out --- a kind of reverse entrainment of the fuel and air. This is especially true in rich fuel mixtures and is one of the reasons why carbureted race engines need to run rich air/fuel...
Like in all things engineering wise, there are compromises to be made. I think it helps to think of the ignition as having available energy in wattage or volts X amps X real time in milliseconds. The spark duration in Milliseconds is apart of the equations and the less volts you need the more...
