...Contrary to popular belief I am not banned ...
Anyways...
Originally Posted by
CapnBoost
The longer trumpet is for low end torque because it increases the velocity of the air before the valve. The shorter trumpet is for horsepower because it is the shortest possible path from atmo to the cylinder.
The reason for having longer and shorter intake paths (or variable length manifolds) is to time the returning pressure pulse so that the intake valves open when the pressure wave is as close to the valves as possible.
So you need a longer intake trumpet at low RPM and a shorter trumpet at higher RPM.
The reason being that the speed of sound (thats how fast the pressure waves travel) is relatively constant, and the main variable is engine RPM. At low RPM there is a long time between when the intake valves close and when they need to open up again, and because the pressure waves travel at a relatively constant speed the way you time them is by controling how far they travel. The longer the intake trumpet the longer it is going to take the pressure pulse to get to the open end, reflect, and get back to the valves.
Originally Posted by
Kitdy
What causes the peaks and troughs mentioned earlier with turbos?
The peaks and troughs are caused by the timing of the pressure pulses in the intake manifold. This still happens even in turbocharged or supercharged engines.
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.