Island Flow—This is the flow rate at which the supercharger is most efficient. Note: This flow rate is not the peak flow of the supercharger. Typically, smaller superchargers have lower Island Flow, meaning that they perform most efficiently at lower flow rates. While high Island Flow is commonly a characteristic of larger superchargers, and ideal supercharger would have high Island Flow (be efficient at high flow rates) and have a small physical size (making it more efficient at low speeds and low-flow delivery rates).

thats what I got anyhow, any other inputs?

 

Would that be like a turbo map where you are shooting to be at the pressure ratio and air flow that is in the "island" on the center of the map?

 

exactly, yes

 

Right on. The only turbochargers that are close to ideal are the VGT (variable geometry turbochargers) turbos. These act as you describe (high island efficiency at high flow and efficient at low flow as well). They can be programmed to perform like a small or large turbo. Though most work in the lower rpm ranges of diesels, workable versions for performance applications should be available in the near future. Chevy and Ford diesels both use these and Gale Banks has introduced an aftermarket one (VGT turbo and electronic controler) for the new cummins that does not.

 

Aerocharger had VATN turbos years ago. The kicked ***, but they were tiny. They were even self contained too. I've looked ALL OVER for various comp. maps on them. It would be very interesting to see a VATN or VGT turbo vs. a similar regular turbo or SC. I bet its one big island!

 

I recall them making a kit for sleds(snowmobiles) and harleys, where did they go?

 

Why doesnt anyone put these little buggers on cars, according to Maximum Boost there the fastest spooling turbos out there.

one thing I have read about vgt at higher temperatures is that the fins get "slow" and dont move as fast.

 

I would probably say the tuning issues, if any, of an aftermarket vgt turbo might overwhelm most people. Oh yeah, and let us not forget about the price of an electronically controlled vgt. I seriously doubt these come cheap. I cannot even find a price for the 03-06 cummins version on Banks' site. I think the "user friendliness" of your average turbo is about all most people are intrested in at this point. That is unless you own a diesel without one or a low cube high rpm vehicle like an indy car. Great idea but a little too much quid for the small benefit in my application. IMO.

 

most blowers and turbo's have a compressor map to read. getting out of a blowers efficiency range is very common and will lead to big numbers on a dyno, but not so for track use. throwing around hot air just doesn't get the job done.

 

[QUOTE=natural1]When you up the turbo size you are not exactly increasing efficiency, a smaller turbo can be more efficient than a larger turbo, turbochargers are only so efficient anyway (70-77% at best). Efificiency ratings vary from turbo to turbo through the manufacturer(s), it is not determined by what engine the turbo is mated to as the manufacturer almost never knows exactly what their product will end up on. However, the manufacturer does supply an efficiency rating as well as a compressor map that tells you what the operating range of the turbo is. When you choose one, make sure that your engine can keep the turbo in that range. Matching a turbo to an engine is more than a guessing game, it takes careful consideration, there are many variables that should be addressed. A properly sized single turbo will orerate much the same as twins, if set up properly. With turbo size, often times it is better to copy what someone else has already done, this takes the guess work out of the whole matter if you are new to the turbo scene (don't use an STS setup as an example unless you plan to use a remote configuration). If you understand about volumetric efficiency, the air flow demands/characteristics of your engine at given rpm points, and can read compressor maps then you should be able to size your own turbo. As vanillagorilla just stated the 67mm should be a minimum. But, remember there are many variations of each turbo in the form of compressor and turbine a/r. We looked into running a Precision 76mm on a 5.0L mustang before switching to a seriously built 351 with a Precision 88mm. Either way the 67mm will be good but the 76mm would be better...IMO.QUOTE]

This was from the "single or twin turbo" post on 12-10-05. All I can say is word.