Opinions on fueling issue and WUR pressures

[Dr J]

After a recent engine rebuild (800 miles) I put an LM2 in my car and was getting higher AFR's than I'd like. This is especially critical because I have a supercharger I want to mount but have not done so until I resolve the fuel issue.

Car now has a euro fueling system: fuel pump, FD, steel lines and WUR (O 438 140 089)
Injectors are new.

The WUR senses vacuum loss.
System pressure was 4.7 bar (in spec is 4.5-5.2 bar)
Warm control pressure was 3.5 bar (in spec is 3.2-3.6 bar)
Warm control pressure with vacuum hose removed was 2.7 (in spec is 2.7-3.1 bar)

So far everything in spec.
With the engine warm and CIS gages on, here are the AFRs with the car standing still while depressing the accelerator to different rpms:

RPM AFR
1000 13.0
2000 13.8
3000 15.5
4000 16.5

Note: I haven't posted LM-2 charts because I have not been able to get the rpm to register from the output of the Electromotive HPX system (even though the tach has no problem with it).

To determine whether I have a fuel starvation problem, I bypassed the WUR and connected just the gage as someone did in some other post. I used the valve to adjust the pressure. This is what I found:

Control P = 1.2 bar
RPM AFR
2000 10.3
3000 10.5
4000 10.7
5000 11.0

Control P = 2 bar
RPM AFR
2000 11.6
3000 12.2
4000 12.7
5000 13.2

Control P = 2.5 bar
RPM AFR
2000 12.3
3000 13.1
4000 14.0
5000 14.5

Control P = 3 bar
RPM AFR
2000 13.1
3000 14.0
4000 15.0
5000 15.5

Questions:

1) I am puzzled at being in spec yet having a lean mixture. Any ideas why?

2) Looks like I need to be as low as 1.5 bar control pressure to be on the rich side at high rpm. Does this seem right?

[Dr J]

What about a different type of WUR?

[Dr J]

Bump

[boyt911sc]

Originally Posted by Dr J

What about a different type of WUR?

Dr J,

That's a very neat set of data you just presented. But before you go switch to another WUR, I would suggest to check first the WUR's control pressure vs. time characteristics. This will give you a better perspective of how your WUR performs from cold to warm condition. Last not the least, is to verify you vacuum integrity!!!! This is the most over-looked or neglected part about unmetered air.

If you could be certain that there is no unmetered air going into the system that directly affects the 'lean condition', have the air-mixture set to spec @ idle using a calibrated gas analyzer. How does your AFR readings compared to another instrument? BTW, what system pressure are you getting? What's the resistance (Ohms) of the WUR's heater?

Keep us posted.

Tony

[Dr J]

Tony, thanks for the input. The WUR resistance is 31 ohms. The pressure vs time was Cold pressure to Warm pressure in about 6 min. Outside temp was 84 degrees F.

Your suggestion on the vacuum was a good one. I pressurized the system and found leaks in the brake booster at the air box, in the #3 injector, and in a temporary hose I put to bypass the supercharger. I think I'll mount the supercharger and check AFR's. We'll see what happens then.