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A porsche engineer told me many years ago to keep rpms above 2800 minimum. Hope this helps |
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There are cases where a resulting lambda/AFR value oscillates back and forth with a too high amplitude. Normally, it moves between lambda 1.03 and 0.97, but if it goes beyond, for example, 1.05, you can notice such amplitude oscillations (around 1 Hz) as a “feels like pulling” effect. Quote:
Fun fact: I don’t know of a single test report from the years 1980–1983 that claimed the reputation of the Porsche and BOSCH engineers was ruined because the U.S. models with the K-Jetronic from those years had issues. Quote:
Regarding the Porsche part suggestion, ... a genuine BOSCH sensor, or a good-quality alternative from another manufacturer, will work just as well — it simply needs to match the BOSCH part number 0 258 986 501. However, when using a narrowband sensor, I strongly recommend switching to a 3-wire version with an integrated heater (BOSCH part number 0 258 986 502). Connect the black wire to the lambda connector, and the two white wires from the heater: one goes to ground (GND) and the other to switched 12 V — ideally via a relay controlled by the same signal as the WUR. This way, 12 V is only supplied when the engine is running. Quote:
The rule of thumb is: When a lambda-controlled K-Jet system is working properly, it delivers performance throughout the entire RPM range without any surging or similar. I can confirm this from my own experience and from others who have finally set up their systems correctly and, where necessary, replaced faulty components such as sensors, ECUs, switches, plugs, or wiring. |
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https://www.pelicanparts.com/More_Info/91160612300.htm?pn=911-606-123-00-M14&bc=c&SVSVSI=0574 |
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have gone through this for the past couple years, basically my near original 1975 911S has sat in the garage while my 914 and Alfa spider have gotten all the seat time.
In the process of ditching the CIS and fitting a set of Twin Webers From what I have heard, many of these 1974 - 1985 ish CIS cars were like this from the factory |
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Per Bentley, 35C temp switch provides cold enrichment off idle (2-3 degrees) and, here is the interesting part for you, again at 15 degrees throttle movement. I think I was not as clear as I should have been. Unplugging the the 35C sensor will make the car surge all the time, even in cruise. With it unplugged the car thinks it is always under 35C, so you get enrichment any time the throttle is moved even a bit like in cruise. You will see this happen on your AFR gauge. So you are trying to identify whether the 35C switch has failed open above 35C. If failed open, with it plugged in it will act the same as if its unplugged, enriching for 2 seconds every time throttle is cracked or hits 15 degrees in cruise, causing a surge. Two ways to test. Much easier to see if the car is set to run with O2 sensor unplugged as the lambda system will counter the effects somewhat. But you can still do it with O2 plugged in if thats how you are currently set up. Just have to look a little closer at the AFR gauge. Leave the 35C temp sensor plugged in, drive til engine above 35C then look at the AFR gauge in cruise. Push the throttle enough to open the off cruise 15 degree switch. Just a tiny bit should be enough. If the 35C sensor is working, there should be no 2 sec enrichment. If it has failed the AFR will drop instantly way down to 12 or so, you feel a slight surge, then after 2 seconds (per Bentley) AFR pop back up to wherever it was. It’s very obvious. Other way to test 35C temp switch is with temp based continuity while in the car or on the bench. Normally open (NO) below 35C, closed above 35C. Your comment about warm starting is unexpected. AFAIK this temp sensor works with the off idle and cruise 15 degree throttle switch. So it would never affect the start, either cold or warm or plugged in or unplugged because you don't on purpose open the throttle for start. Is your off idle switch adjusted correctly? You should feel a click just after sight throttle movement. Anyway none of this may be relevant but when you mentioned surging in cruise this came to mind as something that could induce that. Regards |
simple solution as mentioned by J.W.Get rid of the oxy sensor since you do not use the CAt..that is all you have to do
Ivan |
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- bad ECU - bad initial CO setup - false air - ... etc Quote:
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Check out this thread where MySocal911 shows how to check the ECU pins: https://forums.pelicanparts.com/porsche-911-technical-forum/1055502-high-dwell-911-sc-81-lambda-us-5.html |
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again ,no reason to have OXY sensor in the system if you are not using the CAT....
Ivan |
again ,no reason not to get things working the way they were engineered — especially since that’s what was clearly asked for above. Amen.
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