ever wonder why your engines torque curve gets higher with the engines rpm level untill about 4000rpm-5500rpm(DEPENDING ON YOUR COMBO) but fades above that rpm level?
well it depends on several factors, first as long as the cylinders can fill completely you get a good fuel/air burn so you get a good cylinder pressure curve against the piston each time the cylinder fires,THE ENGINES TORQUE CURVE INCREASES WITH THE NUMBER OF EFFECTIVE POWER STROKES PER SECOND, at very low speeds theres not enough air velocity to mix the fuel correctly or produce a effective ram tuneing effect but as the rpms increase the cylinders fill very efficiently untill the rpms reach a point where the cylinders just don,t have the time necessary to flow
enough air through the valves to fill the cylinders , remember a 5000rpm the intake valve out of 720 degs in each cycle opens for about 250degs of effective flow even with a hot roller cam, now thats only about 35% of the time and theres 41.6 intake strokes per second , thats only 1/60th of a second for air to flow into the cylinder, I found this graph that shows the relationship between V.E.(VOLUMETRIC EFFICIENCY) and AN ENGINEs torque CURVE http://www.n2performance.com/lectures/lect1/n2perf5.gif


WHAT THAT GRAPH SHOWS RATHER EFFECTIVELY is that its your engines ability to fill the cylinders that increases your power and the more efficiently you do that the higher the rpm level you can acomplish that at the more power your engine makes, remember the formula for hp is (torque x rpm/ 5252=hp)so moveing the torque curve higher in the rpm range increases hp



[This message has been edited by grumpyvette (edited 03-25-2002).]

so whats the trick to improve v/e. can 100% v/e be done fesable on a street engine.

yes ram tuned and rpm matched cam timeing for the effective use of the headers and intake system can get you to slightly over 100% V.E. at (1) rpm range where the tuneing is most effective, look here,
http://www.grapeaperacing.com/GrapeApeRacing/tech/intaketuned.cfm

heres how to find the correct tuneing lengths
http://www.engr.colostate.edu/~allan/fluids/page7/PipeLength/pipe.html

If you play with Desktop Dyno take a look at the VE numbers vs RPM for your particular combo. VE increases with RPM until you pass peak Torque - just like grumpyvette's graph shows.

I think that with increased exhaust scavenging and higher air intake velocity more RPM's help VE until you reach the point that the engine is "pumping" the max amount of air that it can.

Interesting subject.

[This message has been edited by Eric68 (edited 03-25-2002).]

read this it will help http://www.vettenet.org/torquehp.html http://ryanscarpage.50megs.com/street.html