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RarlyL8 RarlyL8 is offline
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 14,086
Porsche sized the K27-7200 almost perfictly to match the fueling of 930 CIS fuel head. What is happening with the C2T 3.3 is it dose start to run up against the limits of the turbo. Thus, it can not maintain full boost to red line.

The C2T 3.6 is alread at the limit for the 7200. Adding boost will mostly help in the mid range but there will be little gain up top.

The limit of the K27-7200 is in the 370-380hp range. Again this is about the limit of the fuel head. To deal with this Porsche changed the on boost control pressure that gets a little more fuel for the 3.6.

I would use that simple caluclation as the most just changing boost would get. In most cases losses in effecency will make the gain a percentage of this.

Changing the exaust increasses effecency with not change in boost. This can add HP. Changing the turbo to one with a larger more effecent compressor wheel will see increasses in effecency from not heating the air as much and allow the car to maintain boost higher into the upper RPM range.

The 3.6 if taken to 1 bar is potentally a 400hp motor. However severl things have to be addressed to do this. It needs a turbo cappable of supporting it, it needs a fueling strategy, it needs the restrictive cat to be removed, it may need the intake ports to be opened up a bit.

As to triggering the overboost switch. All WG's tend to overshoot there target at first and then stabilize at there target pressure. They also start to leak boost some before they hit there target level. Some of the electroic boost controlers go through a set up and learn how the WG responds. With this the can keep the WG clamped untill the desired boost level is reached. They also work on the other end to keep it from over shooting.
I have found all of this to be the case as well. You sure you're not an expert?

While adding boost is the cheapest HP it is not the smartest HP. The most efficient bang for the buck on the 965 is to replace the muffler system and then the turbo. These two changes alone transform the experience.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-27-2009, 08:00 AM
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