90rocz

Here's some stuff I dug up early in the book I'm reading"Supercharging,Turbocharging and Nitrous Performance Handbook".

**Positive Displacement(screw type)Superchargers can generate high levels of boost at low engine speeds.(1000-6500usually) Centrifugal superchargers generate a comparatively small amount of boost early in the rpm range. And is basically a belt driven turbo.
Typically the centrifugal blower will continue to increase gradually with engine speed , but is also limited by engine speed, or max rpm.
Heavier , underpowered autos tend benefit well from "screw" type blower, while light overpowered autos are better suited with a centrifugal set up.
Typically the lager the case of a "roots"(screw) blower, the greater its output potential. While pulley/gear changes will better increase the output of a centrifugal blower.
A "roots" blower capable of blowing 20lbs of boost into a 400ci motor would be both big and heavy compared to the same, capable centrifugal blower.
The speed and shape as well as size of the centrifugal's impeller/housing, determines its output.
**There are alot of formulas in here too, if you like theory.**
When properly sized a turbo will deliver outstanding performance with few concessions. A turbo is more efficient than a supercharger both; thermally and mechanically.
From a mechanical standpoint a turbo reacts to load rather than engine speed. Which means it does not impose a load penalty on the engine unless it's making boost. Turbo lag occurs b/c the compressor assembly can't react as quickly as the engine. By comparison the speed of a belt driven supercharger accelerates and decelerates at the same speed as the crankshaft having virtually no lag.
Since the impeller and compressor aren't phisically attached to the engine, "INERTIA" becomes a formidable force. B/c exhaust gasses drive it the gasses must reach a high enough volume to make the turbo react. The time it takes for this is called Turbo Lag .
Turbo Lag is unavoidable, but can be minimized to a large degree tho. As a general rule the larger the turbo, in relation to the size of the engine the greater the Lag. The reason is simple , more energy is required to accelerate(move)a larger mass. However a smaller turbo will be quick to react but be limited in overall output.

there's more but I'm tired...later.

stonedchihuahua

Someone who actually knows!!!

iroczinoz

In the other thread we had a discussion one Turbo or Supercharge what is better. Well we came to the conclusion that a SuperCharger puts more stress on the engine.

Well how much more stress does a supercharger put on the engine then say the A/C compressor and Smog Pump combined?

Does it put more stress or can we say running without A/C and Smog Pump will let you run a Blower without stressing the engine more then the A/C and Smog Pump already do?

I was just thinking on a long drive today, and thought I must not forget to post this and ask the fellas who know.

Chris Ja

That is a good question. It is the same as running the a/c when under boost. It puts a stress on the engine ie crankshaft and heat to pistons. Makes 4 or 5 runs back to back with a supercharger and see how long your piston rings last.
As was stated from the book"When properly sized a turbo will deliver outstanding performance with few concession. A turbo is more efficient than a supercharger both thermally and mechanically. From a mechanical standpoint a turbo is more efficient". That is the point we were trying to make before. You may be able to make more power with a supercharger but if the engine keeps breaking then which is better. I would say most guys on the board can't afford to replace there engine once a year or more depending on how much you race. Anyone here can build whatever they want. The fact is some of us will be driving while some will be walking.