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Zeroclearance Zeroclearance is offline
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Join Date: Apr 2005
Posts: 24
Keith;


You wrote>

"7200, and to a bit lesser degree the 7006 choke's or governs the turbos speed."

The 7006 compressor wheel runs out of steam before the 7200 compressor wheel. Every compressor wheel has a "map" it will generate "X" lbs per minute>we all know this.. The 7006 compressor wheel is smaller and has "less output" vs the stock 7200 comp wheel.

The 7200 compressor wheel is more efficient, and does have more output. The 7006 comp wheel just runs out of "gas"..

Yes, you can build a hybrid 7006, one can take the compressor stage of the 7200 and mount it to the 7006 turbine and hot housing. The result would be a more output.. While this can be done, there are better compressor wheels that one can "use" More modern/better designs.

You also wrote,

"A larger compressor wheel can push more air at the same turbo shaft speed"

I like to read the results another way. The actual turbine wheel is turning slower, with the larger more efficient compressor wheel. If the target "1 bar" setpoint is maintained> the turbo will reach it running at slower speeds. However, where the smaller turbo ran out of gas, the newer hybrid will continue to deliver the "boost" to redline or greater. Turbine wheel speeds will creep up to meet these demands.

Porsche used this same turbine footprint on the 3.6 ltr engines. We have seen Ruf and many other German "race" teams use this flange for the K27/K29's that were built and run.

Pressure levels at the turbine housing will vary depending on your header design, ie are we comparing a modular header design like Bodarts new offering or the log style factory exhaust system. Designing the wastegate circuit also impacts this discussion. You can port and change the turbine housing A/R and make it more efficient. KKK has clipped the turbine wheels in many of it's Porsche "S" and GT2 cars over the years. You lose energy and free up the turbine wheel. The exhaust can exit the housing easier, thus lowering the static pressure. You can quickly change the A/R of either housing 7200 or 7006 by taking metal out at the throat and enlarging the area at the flange. By doing this you will shift the engine RPM to the right and more the power band. Installing a different A/R turbine housing vs making one/modifying the current one has been done many times.. Porsche will usually clip the turbine wheel before the start to grind the housing (less labor>easier to do).

In the end, most owners that drive the 930 on the street, want the turbo to spool quicker and deliver power to the ground sooner. The 7200 was designed for this purpose.
Old 02-23-2010, 10:59 AM
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