CIS troubleshooting........
 

Get your fuel pressures set correctly and test your CIS components like FD, WUR, AAR, etc. And don’t forget to perform a smoke test to locate those hard to find air leaks. Lastly, the 7 fuel injectors must have nice mist-like spray patterns. Keep us posted.

Tony

What a crazy mixture this engine was. Hard to believe someone would swap in the late US SC intake runners - I'd expect you'd lose a fair amount of the benefit of the larger intake ports. But what the heck, my 2.7 was plenty fast enough to get me a bunch of speeding tickets until I got inco racing on tracks.

What really gets me is that Bosch silver box under the passenger seat. Absolutely nothing for it to do (unless it is part of some other Bosch system I'm not familiar with). What the heck is it hooked up to? There is a modest market for such things - I just paid about $40 US for a used one from a long ago Volvo (I just wanted the case). Of course, you probably don't know if it works, and learning how to test it wouldn't be a good use of your time unless you like to take things apart just to see how they work and otherwise tinker.

I wonder if Tony has a way of testing those electronic units. They are a whole lot simpler than modern ECUs - mostly passive components, one 14 pin IC, and a few transistors, all for pulse width modulation to run the FV. But a 931 part? I was somewhat surprised that I couldn't find this ECU listed in Porsche's parts catalogs.

Glad to hear the car is fairly functional, and you can deal with its quirks as needed until you get it all sorted.

I don't think they swapped the intakes. The motor is a US 1980 motor, so the intakes should be the smaller port no?

Also, I did google that part number for the Bosch ecu and it does come up with results for a 1980us 911sc, so I do believe it goes with this engine.

Everything appears to be correct for the 1980 US SC that must have been the donor for the engine.

But in eleminating the lamda control they added components from ROW SC to try to backdate the system. Just my guess.

It's what I would like to try to do in the meantime.

Testing an ECU..........
 

Walt,

My knowledge about electronic is minimal. Since I need ECU’s and CDI’s to do some of my troubleshooting work, I simply rely on my spare ECU’s/CDI’s that had been tested and ran in a motor. There are two (2) boxes of ECU’s/ CDI ‘s for SC’s (‘80~’83) that were last tested “January 2021” stored in the basement.

The problem with Silver’s engine is the use of mixed CIS components. Just getting the fuel pressure to spec has been a struggle for him. So how would you expect it to run well? The conversion of lambda CIS to non-lambda has been done many times successfully by numerous DIYers. As a matter of fact, the loaner CIS components were never returned back to me because they kept them.

Tony

That's the lambda control unit for the 80US 0280800006, same as in mine.