'80SC RoW, CIS and Timing

tyro · 08-23-2011, 07:03 AM

I thought I had my car running well, but now I'm not sure.

Should I follow the sticker when it comes to setting timing?

I have a Bosch distributor 0 237 301 007 with vac advance. Right now I have it set for 5 degrees BTDC at hot idle, with not much more than 30 degrees advance at higher RPMs.

Regarding mixture, the car runs pig rich at start. I have WUR -045 and I think that -069 would be correct for an '80 RoW? I should probably have a fuel pressure gauge, but I do not.

I have a wideband AFR gauge. While at cruise, AFR is 13.8:1, but at idle I see 15.5:1. With the car at a stop, a little more throttle gets me ~14.7:1. WOT is around 11.7:1 or slightly leaner depending on RPM.

I *think* I have the vacuum lines set right, but though I'd run it by someone who might know differently. I have the lines to the WUR and the decel valve set per the chart below, and I'm fairly sure that the vac advance connection is in the right place.

Thoughts?

Dr J · 08-23-2011, 09:04 AM

Are you having any particular problems? Rich at startup is normal. If your car was manufactured between Jan 79 and Aug 79, the WUR should be 069. The 045 is for 78-79. The 80 model year with o2 sensor should have the 072 WUR (per Bentley).

Timing is 5 deg BTDC with vacuum hose disconnected and capped at idle and 21 deg BTDC at 6000 rpm with vacuum disconnected and capped.

tyro · 08-23-2011, 02:55 PM

Yes, I get the wildly oscillating idle for a while until the components have warmed up a bit. Additional throttle will cure the problem, but it seems far too rich, as in my wideband will go off-scale: 10.0:1 or below.

Once the car has warmed, the idle will settle into normal.

Are you sure on that timing spec? It is my understanding that since it's advance only that it shouldn't matter. I do not have vacuum on the advance port at idle.

I'm mostly curious about vacuum hose routing, the '80 RoW is a little different than most it seems.

Peter Zimmermann · 08-23-2011, 03:42 PM

The Porsche book states ignition timing at 900 +/- 50 rpm should be 5 degrees BTDC vacuum detached.

Ignition timing at 6,000 rpm should be 23 - 29 degrees BTDC vacuum detached.

Cold start idle surge can be present, but shouldn't last more than 20-30 seconds. Someone may have set your WUR/pressure on the rich side to protect the airbox.

tyro · 08-23-2011, 06:19 PM

My 78 guide book shows 5 degrees BTDC at 950 +-50 with advance connected.

It also shows 26+-2 degrees at 6000 with vac disconnected. Sound right to you?

Daviboy · Daviboy's Garage

25° before TDC at 4000rpm max 25° T 6000rpm with vacuum hose disconnected and plugged as chart below for 81 - 82 SC

Vereeken · 08-24-2011, 01:55 AM

Tyro,

We have the same car and more or less the same problems. Indeed a 80's ROW is different then the rest in terms of routing and all bently , bosch and Haynes manuals have diagrams that do not correspond with reality.
I too have a Innovate LM1 AFM meter.

The timing should be indeed set at 4000RPM, being 25° vacuum disconnected and plugged idle at 900-950.
The timing at idle is irrelevant (it can be anything between 5° and 10°).
You can set your timing to 30° at 4000 if you are using 95 or 98 RON Octane.

The vacuum line to the dizzy should go to the back of the throttlebody. I believe to the connection just above the vac connection of the thermo time valve. (I believ thermo time valve is to the back of the TB below and vac advance is to back of TB above). I assume that you have no 02 sensor and no vacuum retard.
There is hadrly any vacuum noticable at IDLE. But it should "suck" major time once revved.

The last small vac line of importance is the VAC line on top of the WUR. This should go to the front of the TB where you only have atmospehric pressure (this is nothing more then a filtered air vent). There is another small vac line on the front of the TB but that is usually blocked. This goes to the diverter valve if you have it.

The "ideal" settings for mixture are 13.3/5 at IDLE 12.7/9 at WOT 13.7/8 at COAST perhaps even 14+.
This will apparently give you the best combination of performance/MPG.

What follows next is assuming you have the correct WUR (you need to search the board for all different sorts of WUR)
AT startup your AF ratio is too high (too much fuel). 10 is a rich situation. This is normal at startup to be rich but not that rich. You should be looking for Mid 12.
The hunting at cold is a sign of too rich. You can test that. If you put your long allen key in the fuel mixture control nut and press on it lightly the hunting will go away.

What I think has happend is that somebody has 'tuned' your mixture either for performance (hence the high 11 at WOT) or to solve another problem (usually a defunct decel valve).

In essence I think your car should run great and safe once warmed up but they have sacrificed a comfortable warm-up period for it. It probably runs like a pig for about 5 minutes, with even some occasional stalling when coming to a stop when not warmed up.

I am not sure you want to start fiddling with the fuel mixture. I started with it and it is a nightmare to get spot on.

tyro · 08-24-2011, 08:21 AM

Here's another point, disconnecting the thermotime switch makes startup much easier. Must be far too rich at start.

I think I'll locate a fuel pressure gauge and a proper WUR if necessary.

Checked timing this morning, 6 advanced at idle, 26 advanced at 4000+.

AFRs today:

Idle 15:1
Cruise 13.9:1
WOT 11.7:1
Overrun 17:1 to off-scale lean

When I acquired the car, there was a WUR for a lambda car in place(072). It ran badly. I installed the 045 WUR and has been much better. Of course I've tinkered with the car whenever I felt that it needed help. For the most part it's fine, just wondering if "better" is still on the table.

Vereeken · 08-24-2011, 08:40 AM

The correct WUR for a ROW SC no lambda is type 916
reference 0438140089 number 248 stamped into the body as well. I think it is the same as a VW bus of that era.
Two vacuum connections one on top one at side.

The thermotime holds off vacuum from WUR when warming up so as to not start leaning out the mixture to soon. The thermotime opens after about 45seconds.
SO what you did is immediately starting to lean out after start-up.

My guess is that your fuel mixture is cranked up a bit too rich too compensate for something else.

robs · 08-24-2011, 11:29 AM

tyro,

the factory equipped the 80 SC RoW (no lambda, no cat. converter) with WUR Bosch 0 438 140 045 until January 1980. Starting with February 1980, they used the WUR Bosch 0 438 140 089. This information is in the "Bosch Automotive eCAT online".

Dr J · 08-24-2011, 02:19 PM

Wow, each reference has a different spec on the timing! Interesting to note, and that is why it is good to have so many people in this board.

If you start the engine cold. Can you hold 1500 rpm by depressing and holding the accelerator? The CIS system should give you higher rpms when cold that are able to sustain a richer AFR. They should drop down as the car warms up. Item 36 in the drawing is responsible for making this happen.