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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
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I beg to differ. First of all, there is nothing that says that you just have to use KKK turbochergers when building turbocharged Porsche engine. Yes, Porsche used them for a while (first turbos used Eberspächer turbochargers) but nowadays there are very good performance-turbochargers available and KKK seem to have fallen back when it comes to development of bigger turbochargers. There are very few compressor maps available to begin with...so many engines are built by using turbochargers modified according to mumbo-jumbo black magic w/o really knowing the exact characteristics of those pieces. Those (few) K27 maps I saw weren't too impressive.

I suggest looking towards Garrett's range of turbochargers. They are good, they are (relativly) cheap, they can be ordered with BB-assemblies and best of all, [b]there are reliable and comprehensive compressor and turbine-maps[/] available.

A GT40R-BB (or maybe GT35 version, if you need less headroom but more response) will cover all your needs and leave room to grow in.

Second:

The less backpressure the turbocharger represents (=the bigger the turbine, and thus the turbine flow), the smaller wastegate you need.

Exhaust gases going trough wastegate are surpluss that isn't allowed to go trough turbine, remember? So if your turbine is very small you'll need big wastegate that will route majority of those gases around.

Wastegates with diameter of 40mm and higher are quite enough most of the times, especially with bigger turbochargers. Attention must be instead payed to mating of wastegate-pipe and header collector. Exhaust gases that are required to make sharp turn to be able to flow trough wastegate will flow badly, leading to overboost-problems.

Regards,
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Thank you for your time,
Old 09-30-2004, 06:43 AM
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