[p4msi1]

Originally Posted by john marcella

Not nearly as simple as advancing or retarding a given Cam . Ivo depends on pressure in the manifold versus pressure in the cylinder left over from the exhaust cycle . Ivc depends on how close your cylinder pressure is to your Intake pressure.
Evo is dependent on how much residual pressure there will be in the cylinder when the Pistons coming up on the exhaust stroke after blowdown occurs ( pumping Loss). Evc will depend on the pressure in the combustion volume during overlap versus Inlet pressure versus exhaust back-pressure on the hot side of the turbo.
See complex.

How in the hell are you supposed to figure this out!!!! Does all this take into account velocities at different RPM points? I guess you would use probes to gather the info needed? Vaught and Wilkie I am not.

[john marcella]

Originally Posted by p4msi1

How in the hell are you supposed to figure this out!!!! Does all this take into account velocities at different RPM points? I guess you would use probes to gather the info needed? Vaught and Wilkie I am not.

You can't there is no math for it , that's kind of the point. Well I take some of that back there is math for it but it's so circumstantial on so many different things dynamically that it's almost impossible to come up with calculations.
You have to try stuff notice Trends and follow the data path. The problem is is you can't get fixated on one part of the system. It doesn't work because that part of the system is dependent on another part of the system and so on.
One of the biggest things that I see in this thread is people want to refer to a boosted motor as such a boosted motor. Shouldn't do that it's a turbo motor or a blower motor , 2very different approaches as well as requirements.

[Tom Vaught]

Originally Posted by john marcella

You can't there is no math for it , that's kind of the point. Well I take some of that back there is math for it but it's so circumstantial on so many different things dynamically that it's almost impossible to come up with calculations.
You have to try stuff notice Trends and follow the data path. The problem is is you can't get fixated on one part of the system. It doesn't work because that part of the system is dependent on another part of the system and so on.
One of the biggest things that I see in this thread is people want to refer to a boosted motor as such a boosted motor. Shouldn't do that it's a turbo motor or a blower motor , 2very different approaches as well as requirements.

Marcella is correct on this one.

The Math just gives your general concepts. You have to do a SYSTEMS approach on the specific engine and typically every system is different. So you look for what the engine is trying to tell you, not some math equation.

A boosted Engine just means that it has a pressure ratio higher than 1.0

There is a world of differences between how a belt driven supercharger and a Turbocharged engine operate and how fast they can make torque and horsepower.

But a guy who understands how the engine works can move between one system and the other because the physics does not change, the math changes but not the physics.

Just saying. Corky Bell wrote books on both Supercharging and on Turbocharging and they are very good because he understands the physics and can explain it very well in his books.

Tom V.