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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Cobalt,

I love dyno charts.

I hope you are right about the 3.6 fuel head. The only difference I could detect was at the WUR that has a lower control pressure on boost than the 3.3.

It is interesting but the factory limminted boost to .9 bar with its special C2T's because of the fuel heads limitations. The limit is not really the head, it is more with the cone profile that the metering plate rides in.

There is a lot more fuel hiding in the stock head. Using an Andial of similar approach to lower control pressure, a reprofiled metering plate to move farther with the higher air flows levels, or triggering the cold running function on the 91-94 turbos that changes the duty cycle on the factory lambda frequency valve at the fuel head are all ways to do so.

On the dyno chart for the 3.3, the AFMs are to lean after 5500rpm. It might be ok on the street. However, not for a track car. If he is short shifting he might get away with if for a while. If he spends much time above 5500, his time will come.

My thoughts and work with a guy back in Colorado (Brent) about five years ago resulted in what is basically the IA head. Mostly it is a head that has been adjusted to be out of adjustment. This can be good for about 10-20% more fuel but it comes at all air flow points. When we first started playing with this we found it made for way to much fuel on first boost. I then proposed using an RPM switch to delay triggering of the WUR enrichment until the point where we needed it. This hurts throttle response by keeping the CP high for longer and slowing down the metering plate but it dose help the fuel curve on first boost.

I ended up taking a different approach with my C2T 3.3. I stepped back to a K27-7200. This limited my top end some but it came in a lot harder and faster. To this I changed how the compressor bypass valve worked to a unit that flowed more an stayed open at steady state rpm and opened immediately with throttle. Lastly I plumped a frequency valve around the WUR and used it to dial in my AFM's at all points and to quickly open the metering plate with acceleration. I may not have had the HP of some but my power under the curve was solid and my throttle response was only matched by an EFI conversion.

Not an expert, must my thoughts.
Old 02-27-2009, 10:17 AM
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