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Zeroclearance Zeroclearance is offline
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Join Date: Apr 2005
Posts: 24
The stock 7006 compressor wheel is 2mm smaller vs the 7200.

If you were to CC the 7200 and 7006 turbine housings you will find that they are very close. The 7006 is only slightly larger. However, it is the massive turbine wheel (7006) that "lowers" the exhaust pressure. This turbine wheel will typically shift the RPM curve 600 to 750 RPM's up the curve.

A 7006 will run out of "boost" similar to a 7200 within 150 to 200 RPM's of each other. This is due to the "smaller" compressor wheel. Years ago I took the 7006, but mated the 7200's compressor wheel. The results were "okay" Boost came on within 100 RPM's and was sustained longer.

Please note that whenever one installs a larger compressor wheel on any shaft, the net result is a lower shaft speeds. The compressor stage in more efficient, the turbocharger will meet the target boost setpoint at a lower speed, one direct benifit is being able to sustain boost longer in the engine RPM. If one increases the turbine wheel size we will shift the "output" up the RPM range. Porsche has done this over and over with it's various engines. You can look at the two 951 turbochargers, Both had turbine wheel changes and turbine wheel changes, again they did that with the 993TT/996TT similar K16 and K24's. A larger turbine wheel and A/R change occured. With the 951, 993/996TT the compressor wheels were changed. However, with the 930, the turbine wheels increased, but the A/R's stayed the same.

12 years ago I asked a KKK engineer why the compressor to turbine wheel ratio was so small on the 7006, his reply was that Porsche wanted to limit the boost/torque output. The smaller compressor wheel will run out of air at a certain RPM> call it a governor.

For most people that drive the 930 on the streets, they want a faster spooling turbo. Most stock engine with cams do very well with the 7200 based turbocharger. For that matter there are alot of 3.6 ltr 965's running 7200 based hybrids..
Old 02-22-2010, 06:35 PM
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