CIS running lean at high RPM

[LakeCleElum]

Subscribed - Have the exact same setup in my 73.5 with the Max Moritz P/C's. Extra 90 RWP over the stock 2.4....Don Gilbert: Luv you set up, where did you source the gauges?

[930 ZZZ]

Hi LakeCleElum
pm sent

[turborat]

The ending my story is expensive. After a lot of money and time chasing timing, ignition and fuel flow, the problem was clogged iinjectors. This lean condition led to broken rings and piston do to all of the dyno testing.
Note that the entire fuel system in my car was changed for track. Fuel cell, pump in cell and relocation of accumulator and filter due to roll cage impediment on rear rail. This relocation of the filter was the problem. I relocated filter to the front of car near the fuel cell. The inside of the Aeroquip hose began to deteriorate after 5 years of trouble free service. We suspect due to ethonol. The particles or rubber were very small and made it past the screens in the WUR and the fuel distributer and clogged the injectors. While a simple explanation now, it was a tough and expensive diagnosis. The engine revved fine, no missing and adjusted properly. Had I kept the filter in the original location, I would have avoided any issues.

[schumicat]

glad you found problem. you said you cleaned injectors in the original post, that's why no one guessed injectors.

[turborat]

Perhaps, but I learned that these injectors cannot be effectively cleaned. I suspect that others on this forum know this also. I later found out that when the second CIS was fitted, my original injectors were used (Doh!). Had I known this, I would have immediately replaced the injectors. A set of injectors was borrowed from another Customer car and I made it 2 laps around Road Atlanta before they were clogged. I then moved the filter to its proper location, flushed the CIS and installed a new set of injectors (plus replaced the Customer's injectors). The car and engine ran flawlessly for three DE weekends until oil smoke presented itself on deceleration. All of the Dyno testing with lean AFM probably broke the rings. It took three weekends for the damage to manifest itself completely. Porsche engines are quite an amazing bit of kit. Even with broken rings, broken piston and a ruined head, the engine was making good power and sounding great. Most any other engine would be wheezing, coughing and complaining at every revolution.

[fred cook]

I used an innovate air fuel ratio gauge to adjust my 3.3SS twin plug so that at lower rpms it will run at around 14.5 a/f ratio. To get some enrichment on the top end, I added a spring loaded switch and wired +12v and a ground into the cold start valve.
It is only activated at wide open throttle (WOT) and pulls the a/f ratio down around
13.0 - 13.5 which I believe will be sufficient to keep from having detonation or lean issues on the top end. I currently have the ignition cut out set at just over 7,000 rpms. The CIS air box and runners are the large port ones from an early SC while the rest of the hardware came from a later (1980) model. So far, it starts and runs well, pulls strong and is holding around 190-200 degrees oil temps. The WUR is stock 1980 SC and seems to be doing it's job quite well.