i-speed

Here are the more major differences.

Turbo's are more efficient than Supercharges and therefore can create more boost and more easier. With that though Turbocharges have to spool up to become more efficient because they run of the exhuast of the engine.

Superchargers are less efficient but boost is there from a dead stop, though you cannot make as much boost with a supercharger as with a Turbo. No lag time to wait for the supercharger to spool because it does not spool off the engine exhaust. It runs off a belt connected to the crank pulley. Though this draw some power away from the engine to run the supercharger.

sb427f-car

This isn't entirely correct, no offense. Turbos are generally only mostly 85% efficent (on an average) and only realise, at best, a 90% or so efficency. Turbos are exhaust gas driven. Thus, it takes no true HP to run a turbo, except that a careful balance in terms of turbine housing and exhaust flow are important to prevent to much lag vs. choking the engine on the exhaust side. (Remember, you have to be able to flow as much air out as you do in). That's the other thing, because turbos are exhaust driven, you must match a turbo that will be able to support high engine rpm HP while still maintaing enough low speed response. Finally turbo systems are easily intercooled which is a big big big plus.

Roots and screw type blowers are less efficent than turbos and centrifugal blowers. Superchargers are underdriven off the crankshaft and take HP to run. With this said, and the different types, let's tackle them real quick. Roots and screw type blowers are what you might find on a big block chevy or that of a top fuel dragster. They are not easily intercooled, which means they loose out on the air charge density efficency. These two types of blowers will generate great off idel response as they build boost rapidly and almost linerally (if you looked at boost psi mapped over engine RPM). While efficeny for these have gotten better over the years, they are still only about 50-60% efficent. Now, as for the centrifugals, basicly a belt driven turbo compressor, they opporate much like a turbo. These blowers can be easily intercooled or aftercooled, and operate in an efficency range more like a turbo, about 70-85%. ATI Prochargers, Vortech, Powerdyne are some of the manufactures on these type of blowers. Their off idel response isn't as great as a roots blower but they generally do build boost a little more rapidly then that of a turbo.

Hope this helps. Have fun, be safe.

i-speed

No offense taken I am still learning more every day, thanks for the info.

sb427f-car

Cool, hey we are all there once in our lives. I actually found this forum from a link on another board about the tool that decided to run 18psi on his WRX and then try and get the dealer to replace it. Well, I don't want to start a big flame war again, as just having started posting here, so, we'll leave it at that.

Just to let yall know I am still not a car owner but I'm thinking that in a year, when I get done with college, I'm going to look into getting a WRX cause of their functionality, driveability, and fun factor. Of coures, the dream car is obviously my the same as my handle. Peace.

i-speed

Keep the flaming to a minimum and this is a great board to be on.

sb427f-car

I don't usually flame unless flamed upon. And usually that only happens from me on a political topic thread. And I rarely start those cause its eaiser that way.

neouser

Actually, you're being a little generous there with the figures for turbo efficiency. It's entirely possible to have those efficiency numbers with intercooling. However, on the most part, your average turbo will see about 73-78% efficiency. A centrifugal supercharger will see about 73% efficiency. An Eaton blower, the worst of the group, will see about 65% peak efficiency. And finally, a Lysolm twin-screw type supercharger can see up to 70-75% efficiency. Once you intercool any of the said devices, you'll see a rise in efficiency. (Then again, you may have been quoting numbers strictly with intercooling, in which case, I agree with your figures.)

Actually, it's in another thread in here, it was discussed that Rimmer made a kit for the 2.5 RS that used a twin screw supercharger and was intercooled. Those things are extremely efficient and can easily produce high boost from a low rpm to rev limit while maintaining an extremely low delta temperature. I believe it was in a recent Mustang magazine that I was shown a comparison of the OEM Eaton blower vs. the Autorotor on a Cobra. The difference was incredible. The twin-screw can easily compete with a turbo and I wouldn't hesitate to recommend one to anyone who wants to develop a forced induction system for their car.

As for the comparison of the turbo to the centrifugal supercharger. The turbo actually has a better boost curve than the centrifugal supercharger. Don't get me wrong, the centrifugal is definitely a solid and proven device. (Especially when paired up with the displacement of the 2.5 litre EJ motor!) But I would definitely give a properly matched turbo the advantage over the centrifugal supercharger when it comes to the boost curve.

Overall, I'm awed by your explanation detailing the importance of selecting the correct turbo to match a motor. Great job!