1981 SC CIS - low idle - wrong WUR?

[wreckah]

okay, received the 090 WUR, measured it at 25,3 ohms, just like the seller promised,
installed it, and got a start off the key, without touching the accelerator. It idles low still, around 600rpm, but at least it idles on its own, and it will accept throttle immediately without coughing or backfiring...so there's an improvement definately.

Now i have to drive it for around 20 minutes, and reset the mixture and idle speed, and see what those changes will do for the next cold start.

[boyt911sc]

Jan,

Take a baseline data for this new WUR-090 either with the engine running or just the FP. Measure the cold control fuel pressure @ start, 30 sec.,60 sec...........up until the control fuel pressure stabilizes to warm control fuel pressure (max. 5 mins. run). Keep us posted.

Tony

[wreckah]

okay, i will do that one of these days,

i went out today for a proper drive, and the difference is very noticeable...turn key, start engine, drive off, without hesitation, without waiting for the motor to catch its breath so to speak, so this already gives a lot of pleasure in day-to-day driving/stopping/starting.
Now i don't have to explain all these starting procedures to my gf anymore...just turn key and go!

i didn't have to alter the mixture settings at all when warm.

[Vereeken]

Post your pressures as follows -this will help a lot of folks-

Ambient temp /CCP/RPM


Most people forget to post ambient temp when posting pressure. The ambient is important when verifiying CCP.

[wreckah]

okay, it's about 15°C here

i measured fuel pressures again, this time with the correct 090 WUR with good resistance:

system pressure: 68psi, 4,65bar
cold control: 25psi, 1,6bar
first it rises slowly:
2 min: 30psi, 2 bar
3 min: 35psi, 2,4bar
then it goes quicker:
3m30: 40psi, 2,8bar
4m: 50psi, 3,45bar
4m30: 55 psi, 3,8 bar
it stays on 55 psi then.

i guess that doesn't look too bad.

[Vereeken]

No that looks normal.

Does a 090 have vac control or not?

[wreckah]

nope, no vac control, just a vent i suppose, same as 072.

[Vereeken]

I see that the CIS primer calls for 1.6 at 10 degrees. But I do not have the graph.

1.6 is probably in the middle of theb band so with 1.6 at 15 degrees you are likely at the rich side of start-up band but if it works I would not bother resetting it.

[wreckah]

outside is 11°C now, i'm at 1.45 bar cold control this morning
the graph specifically for my car is here:

[Vereeken]

Yup. at the rich side of the graph but within the bracket....

Good to go. The start-up should go very well.

What RPMs do you get at idle the first minute at these temps?

[wreckah]

Cold idle is still not good. The car runs only with a bit of throttle for the first 30 seconds or so. The car runs good though, no spluttering, good reaction to throttle input...so mixture seems good, just no elevated idle.

ok guys, some more interesting info:

i've installed SSI's and took the opportunity to mount a wideband innovate 02 sensor + controller + gauge. I use the analog output of the wideband controller the emulate a narrowband 02 signal for the lambda brain. Great piece of kit, nice to know the engine is running safe AFR's. The O2 signal works, i see the AFR's react to the input.

cold start i see around 11 AFR when the 02 sensor kicks in (half a minute or so), and i see it rise steadly towards 14.7 after couple of minutes.

Warm:

I set the mixture (without 02 input) at 14.2 AFR, which is around 0,6% CO, according to spec. When i plug in the 02 signal, the car responds nicely and dithers around 14.7.

Cruising, i get 14.7.

I noticed a somewhat flat bottom power (<3000rpm) so i pulled a little trick: i reprogrammed the analog output to 14.2 AFR (laptop programming in a 1981 SC ) , and so now i cruise around 14.2 AFR, and throttle response at low rpm's is greatly improved. I also notice much easier getting away at the lights, stalling is almost impossible. I know this doesn't give me more power, but throttle response is worth something too.

Then i noticed something else: when suddenly flooring the throttle, i see no immediate enrichening of the mixture. I go towards 4K, 5K, 6K and the AFR stays at 14.5ish. Only when i let off the throttle or when i punch in the clutch, i see immediate drops to 11 AFR for a split second before the mixture normalises back to it's default dithering.
I also feel a flattening torque after 3500 RPM, i'm sure there should be more power there.
I checked the 15°C temp sensor last year, OK, and i checked the throttle WOT switch (i have 000 resistance from the WOT switch wire to the temp sensor to ground when i go WOT).
Maybe somehow the ground through the temp sensor is not there? Can i ground that wire separately to test?
I'm sure i should see AFR's drop at least from 3K rpm onwards?

thanks for your input,
Jan

[wreckah]

idle around 500rpm at cold start.

[wreckah]

okay, some more testing, engine warm (20+ minutes of driving):

i'm cruising at 14.2. Floor the throttle, AFR immediately goes to 15.0 and basically stays there untill i let off the throttle or clutch in. 3rd gear, uphill, so at least 5 seconds full throttle...no enrichment...also i think i should have more power up top.
the only time i see lower AFR's is the moment i clutch in, then i see a split second 11's or 12's before returning to normal.

I connected the WOT switch to ground, AFR instantly goes to 13.5 at idle, indicating a higher duty cycle in open loop, so it seems to be working. But the moment i floor it, AFR goes to 15 again and stays there...

I tried running without 02 sensor, but then it's running even leaner.

Pulled the OXS relay, idle drops instantly, push in relay, idle perfect. So there's power to the OXS box.

Basically, everything works very nicely in closed loop...once in open loop, i'm running not rich enough. Is this normal behaviour? i would think not.

Could it be air flow meter related? Last time i took off the boot, it seemed to be sitting correctly.

[wreckah]

ok, more testing.

i did a very dirty trick: i disconnected the WOT switch, and set the closed loop at around 13.2 AFR. So now, the FV always tries to get to 13.2 AFR in all conditions.
well, the results are simply awesome: the car pulls straight from 2000 to redline, AFR's stay healthy, and no torque loss in upper regions. It's a canonball...this is what i expected from this engine with the SSI's. Good idle too. This is how the car should feel in open loop.
( I know i lose mpg this way, but i think i can get around that by using the WOT switch to switch between output 1 and output 2 of the wideband controller. output 1 = cruise mode, output 2 = WOT mode)

But of course i would like to get the original system running correctly.

I know now that something is wrong in open loop. The 65% FV pulsing in open loop is for some reason not enough to give the engine enough fuel at WOT.
I think i can exclude fuel pump and fuel distributor, as they can give plenty of fuel during my dirty test.
Maybe the lambda brain has a fault in open loop?

thanks for your insights,
Jan

[Vereeken]

I am hoping someone who know US systems is going to step in.

Actually what you have done is created the conditions of a 089 WUR with vacuum enrichment at WOT

But why the FV does not do the same thing is beyond me.

Following with intrest.

[wreckah]

yep, somehow, the combination of 65 FV pulse, and WOT behaviour (butterfly open, air flow meter opening up) is not giving correct mixture.

[tito911s]

Jan,

Would you be so kind as to review what changes were made to improve what condition? As I recall the initial condition was a hard to start, stumbling 81 SC with US CIS.

After reading the thread (engine rebuild aside) it seems that the FV relay, correct WUR, new plugs, and tuning AF mixture/idle w/4 cycle duty meter ultimately improved running condition.

I see above you are going beyond "fixing" by using more fancy tuning. That's cool, but just want to understand more definitively what improved how your car runs.


Sent from my iPhone using Tapatalk

[wreckah]

Well, yes and no. I did the things you described yes, and that improved running. Bur along the way something else broke and now i have no wot enrichment, which means no power unless i trick the system with the o2 sensor output.
I think lambda enrichment box is fried, but no way to tell. No info on that thing anywhere.
I am considering bitzracing efi now, because i am fed up with buying expensive secondhand cis parts that dont solve the issues. I dont care for originality, i just drive the car. A well tuned efi should be great for longevity of the engine as well as trouble free starting, good mpg, good power.

[tito911s]

Appreciate your final analysis. Many who go through CIS issues, me included, consider the EFI alternative.


Sent from my iPhone using Tapatalk

[boyt911sc]

Originally Posted by wreckah

idle around 500rpm at cold start.

Jan,

Have you inspected and confirmed that the AAR (auxiliary air regulator) is open during a cold start? Do a visual inspection of the AAR's slide valve when the engine is cold. Keep us posted. Thanks.

Tony