2.7 will not run well after CIS rebuild

[berndtj]

I just recently went through a year of trying to get my CIS running well. I bought the car a year ago and right off the bat the car ran like crap. I felt sad and quite frankly ripped off.

It wasn’t until recently that I finally got the last of the main gremlins sorted and it runs well for the first time. The two things that really helped me were an ARF gauge and help and encouragement from folks like Tony.

I’m not here to give you any advice, just to empathize. Good luck! The AFR gauge was super helpful…


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[Ginger77]

Originally Posted by berndtj

I’m not here to give you any advice, just to empathize. Good luck! The AFR gauge was super helpful…

Thanks! I have an AEM UEGO 30-0300 and it's great and super fast on startup. Actually the AFR gauge shows me I'm in the ballpark. Maybe that's even more frustrating in this case.

[jma0506]

Bringing this thread back to life as I am trying to wrap my head around the specs of my newly rebuilt 033 WUR on my '77 911S 2.7 Targa. Note that I am being told by the refurbisher that the WUR is within spec, though it seems that isn't truly the case.

Running all the various pressure tests to have baseline pressure measurements of the rebuilt WUR [results below] before starting up the car, everything I have come across in the workshop manual and in this forum tells me that my CCP numbers are lower than they should be. The additional point of confusion I have is what the source of truth is for CCP numbers for the 033 WUR - there seems to be two different CCP charts [see below].

Robert Bosch


Workshop Manual


There are 2 differences between these two charts: the ~0.5 Bar difference in each scale and the workshop manual seems to imply CCP is measured with vacuum.




My Pressure Readings:

1977 911S 2.7 - 033 WUR
System Pressure: 4.9 Bar
CCP (no Vac) @ 17C: 0.9 Bar [LOW]
CCP (with Vac) @ 17C: 1.5 Bar [LOW]
WCP (no Vac): 2.7 Bar
WCP (with Vac): 3.6 Bar


So based on all of this, I am hoping to answer the following questions:

1) Is the inherent difference between the Robert Bosch Graph and the 911 Workshop manual simply excluding vacuum (bosch) and including vacuum (workshop) in the CCP measurement? The delta between the two looks to be ~0.5 Bar on average which is the delta I measured between my CCP with and without vacuum.

2) Which chart is the source of truth for 033? And if it is the workshop manual, should we be testing CCP with vacuum applied or not?

3) With my WUR CCP numbers being low, in order to increase the CCP of the 033 do I need to raise or lower the pin located between the top vac port and electrical connector?

Thank you all for the always informative discussions!

[r_towle]

I am now invested in a positive outcome.
What happened?

Should we put a go fund me campaign and convince Tony to go to Amsterdam?

[boyt911sc]

Originally Posted by r_towle

I am now invested in a positive outcome.
What happened?

Should we put a go fund me campaign and convince Tony to go to Amsterdam?

All Diederick needs is a good working WUR. The WUR-033 is out of spec and needs work. The enrichment number is not good and could be unattainable.

I have provided hundreds of these WUR’s over the years to fellow Pelicanprts members and counting without a single return. You need a properly tested and calibrated WUR. To start and run a CIS motor, you don’t need to touch the gas pedal. If it requires help, you already have a big problem.

Diederick’s WUR-033 is not correctly rebuilt to produce the required control pressure readings. Spending $1K for the rebuild of a WUR & FD is no big joke. In my case, I allow people to use and test my WUR’s and FD’s with no obligation to purchase. If not fully satisfied, send them back to me, NO QUESTION ASKED. I know someday my streak will be broken and retire with a good record.

Tony

[PeteKz]

Diederick: I've been wondering what happened. Did you give up and take it to a shop? Did you just set it aside while taking care of the other stuff in your life? Did. you decide to go ITB? FYI, if you haven't gone to ITB yet, I would not do that for this engine. It won't give you any performance benefit unless you change cams, compression etc. The CIS works very well on the stock 2.7 engines, and can be modified to work even better.

Of course, you have to get yours working correctly first, which has been EXTREMELY frustrating for you. However, I feel like you are so close, that just a little bit more work will find it. And since you have already replaced almost all the components, it would be a loss to throw in the towel now. It has to be something simple you and the others here have overlooked, or can't see at the other end of a keyboard.

I don't have personal experience with ITB setups on 911 engines, although I do on American engines. For the American V8's and V-twins (Harleys) so many people have done this (millions?) that the combinations of after market systems, cams, compression, etc. are very well known and the initial setup and even advanced tuning can be done without a dyno. You go to the manufacturers web sites and download the files for the listed combinations of parts. Not so for Porsche engines (yet). So if you think you will save time, think again and read some of the threads here about setting up ITBs. If you still want to throw in the towel, you would be better off going to carburetors.

One other thought: I watched the videos of the engine stalling after being revved. AFR about 14.0 is about where it should be an idle. Have you very slowly increased the RPMs to see if it stalls, and especially what happens to the AFR as the revs increase? Is it going rich just before it stalls? Also make sure the engine has been completely warmed up by idling for at least 15 minutes before doing your testing. The AFR sensor must be at full operating temperature too to read accurately.