1981 SC CIS - low idle - wrong WUR?

[wreckah]

very happy, my very first cold start this morning (6°C) without touching the throttle pedal.

[Vereeken]

Originally Posted by wreckah

hiya,

no, everything was there: csv, aav, decel valve, aar, etc...including all the piping.

The only difference was the dark red part you see on the picture. That part (mounting flange) has an air port to which you attach all the mentioned components. On earlier CIS systems, that part is blocked offinternally because they had a fast idle lever and no need for AAR etc... On my car, it should have been open. (updated part) So the PO mounted the wrong part. It looks exactly the same from the outside.

here's a pic if you can see it:
https://scontent-amt2-1.xx.fbcdn.net/v/t31.0-8/17880159_10155244957682863_3508662787624301961_o.j pg?oh=ea7d919297d5cdf0ab356d8543358cb2&oe=5954F42B

i simply drilled a hole in there now, and it works.

Strange to block it off at that position.

The AAR from Nissan does work but if I remember correctly it is part plastic. I decided against it because of almost no heat transfer which would mean a high rpm even when already warm. But it was only 30 € or something.

If you can blow air through it , it is broken anyway. It usually is the pivot of the barn doorn that is worn out.

I will gladly take the junk off your hands. PM me so we can make a deal if you want to part with it.

My stock SC gives about 33° of total advance.

[wreckah]

exactly, i don't get why Porsche ever developed that part with a blocked port...you would think that they just make the flange without port...

[Vereeken]

Originally Posted by wreckah

exactly, i don't get why Porsche ever developed that part with a blocked port...you would think that they just make the flange without port...

You could order a 911 with a cold weather package. Maybe you could also have a desert package? No need for all that stuff.

[wreckah]

this mounting flange is part of the no-airleak-package, it is available voor 2000€.

[tito911s]

This is all great. Although, I'm sure a few guys -- including Tony -- will disagree on your statement about the CIS parts. Keep us updated on the use of the "updated" AAR and when you feel you have it mapped perfectly for your use.

[wreckah]

a brand new CIS system will work great, i'm not debating that but with most of the parts now NLA i don't know how you can keep these old systems going without breaking the bank. It's already expensive now, it'll be impossible soon. Especially the later US cars with their addons and addons and addons.
Now that i've had literally every single part in my hands, it feels like a miracle that these cars are running at all, let alone run nicely!

Anyway, i'm quite happy now, with this very simple system...a MS computer, a fuel pressure regulator, and a AAR, nothing much to go wrong. Very easy and cheap to replace.
And the throttle response is truly amazing, as is the low end torque. I've spent so little time at redline over the wintermonths that it is hard to compare with CIS, but it feels more than healthy there too.
The proper fueling is also important for the longevity of my fully rebuilt engine, i don't want to ruin it with a lean or suboptimal running engine. (when they did the rebuild, they did notice damage from lean running, i think i can see why now.)

[Jonny H]

Hi Jan,

Regarding the extra few degrees you are seeing at higher RPM...

On the Bosch CDI boxes, the trigger input circuit introduces a delay proportional to RPM. As the RPMs rise, the delay is greater, meaning that you lose a few degrees at the top end, compared to the published advance graph.

We noticed this during the design of CDI+ too but we can compensate for it in the software. On the GUI, it is labelled 'INPUT DELAY ADJ'. We have found by measurement that the delay is 170us through our input stage, so we use this value to dial it out.

The result is, you get the actual advance published by Porsche, not one with the advance tailing off. In other words, a few extra degrees at high RPM.



I made a video of the tailing off effect here:

http://youtu.be/jX0ZNijGjSs

[wreckah]

best drive since i bought the car...it's fast, it's smooth, throttle response is superb, phenomenal.

[wreckah]

so, to finalize this thread

- i went ahead and chucked the AAR out of the car, the last remnant of the CIS system. I am GLAD.

- i replaced cold start operation with a hand throttle from an earlier car. Sometimes the simplest solutions are the best. I didn't want to climb another learning curve with idle actuators and upgrading MS software, and putting new chip in, etc...so, simply replaced the hand brake assembly with one from an older car, with hand throttle and 1 heater lever. It's super fiddly (small hands!) but install went relatively straightforward. Cheap too.

- i went to the dyno 2 days ago, and had the operator tune the fuel maps for the megasquirt system, and more importantly, to check the O2 readings i'm getting from my innovate LC2 controller. It turns out i'm getting 1 point richer AFR on the innovate compared to a professional exhaust sniffer. This is very normal according to the operator (innovate sniffs the headers).
This of course is very important for the future finetuning of my car, because the 02 readings influence fuel maps and warm up routine!
I noticed that my car felt best at 11.5 AFR WOT, and that correlates to 12.5 AFR with professional equipment, so right in the ballpark for these engines.
- i installed a basic map from one of the members on the bitz board, a map that felt the best to drive. It was on the rich end of the spectrum, but i wanted to play safe until i saw a dyno.
- so the operator tuned WOT and also some part throttle and initial throttle opening, and he said the whole map was a little on the rich side, but nothing terrible.
- i gained 10hp and 10Nm, even more than 15Nm in low rpm, and the car is now running fabulous. Of course the SSI's play a role, but probably not massive gains because i run the stock quiet exhaust of a 1974 car. The horsepower tops out at 5800RPM, peak torque is at 4200RPM, perfectly following the book values for SC engines.
- cold start is literally a breeze now pull the lever, start the car, and drive off! No more stumbling, waiting, hesitating, etc...lower the lever as you warm up.

Driving the car is even better than before, supersmooth, and quick! The lowend torque is so useable. Throttle response is so crisp. It also feels great to drive a car and to know that the engine runs healthy and correctly. I don't have to include a manual to my girlfriend to get the car started

[wreckah]

[wreckah]

oww, and cruise control too

[Vereeken]

keep the AAR. I will be picking this up soon.

I love non-functional CIS stuff.

I am surprised on the LM. Is the 1 point richer also the case at idle? I sure hope note.

[wreckah]

still love the boring no-drama bitz kit! -2°C this morning, car started after 0,5 seconds of cranking and ran great immediately

i learned sometime ago that you cannot alter the 02 sensor wires (which is what i did on the original innovate sensor to get more length)...maybe that also explains some of the difference in readings with professional equipment. Swapped it out with a non-cut sensor now. Haven't really noticed any different readings though.

I'm toying now with some leaner cruising fueling without altering the throttle response and engine reactions...laptops in 911 SC are fun!