Millhaus

I have a stock 1980 930 with CIS and no cat. What is the recomended air fuel mixture? Some one told me it should be around 11.

Any suggestions.

Thanks

nathanUK '81 930 G50

On full boost WOT 11.8 - 12.2 AFR would be good but you are unlikeley to be able to get it that accurate.

Millhaus

I used an innovate LM-1 this weekend and adjusted it so the average is 11.8 AFR

At idle it is 9.9 and max is 13.5

At idle it is so rich I can smell the fumes and there is black smoke out of the exhuast at warm up. If I go an richer it may be unbearable.

Is this normal?

Millhaus

I have another question.

Is the only way to adjust the AFR on a stock 930 by the fuel mixture screw near the fuel distributor?

The stock WUR is not adjustable correct?

If I am running rich at idle and lean under throttle does that mean that my WUR is bad?

Thanks

nathanUK '81 930 G50

The stock wur is not really adjustable. You would be best to get Brian Leask to rebuild it. You can tell him your exact setup and he will preset it for you. Of course you would be wise to check everything after resetting your idle AFR.

It would seem that maybe your wur is shot.

AFR at idle could be around 13. A long way off 9...

Mark Houghton

Yup, probably is the WUR. Although many of us try to compensate by running the idle AFR on the rich side, you shouldn't be as eye-watering rich as you seem to be, yet lean at full boost.

I just last week carried on an email discussion with Brian Leask. Here's some information and contact:

The process entails shipping me your WUR, so that it can be completely rebuilt and modified. The modification process adds 4 external adjustments -- one for each of the control pressures, cold, warm and enrichment. The remaining adjustment is for the enrichment threshold. This allows you to delay full enrichment until about 6 to 8 PSI of boost, rather than the stock setting of approximately 3 PSI of boost. The adjustment features use custom stainless steel hardware for longevity. If you can provide a list of engine modifications, I can preset the Adjustable WUR to get you close to the optimal settings for your engine. This will keep your tuning to a minimum. I can also preset the unit to exact factory specs, if you so desire. More information can be found on my website here:

http://members.***.net/930wur

Millhaus

So how do you know if your WUR is bad?

I did some quick checks with the LM1 last night and at idle I am 10AFR.

In 3rd gear:

2000 rpm 11.2

Millhaus

How do you know if the WUR is bad? I did some quick checks with the LM1 last night.

3rd gear:

2000 rpm = 11.2 - 12
3000 rpm = 11.7 - 12.5
4000 rpm = 12.6 - 13.2
5000 rpm = 13.2 - 13.3

It stayed constant under load (boost) but when I back off on the throttle it would spike up shortly then level back out.

I don't want to replace it if it is good.

Thanks

nathanUK '81 930 G50

Don't replace, get it modified so you can adjust it to your exact requirements.

To test a WUR you need a set of CIS gauges and compare the readings with official factory workshop manual. There is a chart to work it all out. Personally I wouldn't bother, just do the above.

JBL930

If you are rich at idle and cruise, and leaning steadily out on boost, then it could be a split/leak in the boost hose leading to your WUR, it's the one on the side of the WUR not on the top. If this hose is good then i would say there is something wrong with the boost enrichment part of the WUR, if the diaphragm had split it would be venting fuel through the small hose on the top of the WUR which should vent through a hose and into your airbox, check for fuel in the airbox.
If you run your engine any longer at 13.2afr at 5000rpm (or anywhere on boost) the next topic you will start will be "I need help rebuilding my engine"


Your fuel should be somewhere around 12.5afr at idle, then low 14's at cruise with no boost, something like 14.2afr, then as boost comes in should drop measurably and be around 12.0afr at WOT. A little over 12.0 isn't going to be bad but if it was me i'd aim for high 11's at WOT to be safe.
Your fueling is shot mate, don't drive that car on boost AT ALL until you get it sorted out, have you ensured that the sensor is calibrated in fresh air?


As has already been said, get the WUR off to Brian Leask, you will regret it if you don't. Besides, it's the ideal first modification which allows you to dial in a little more fuel as you go for more mods, and if you don't go for more mods at least you can get the right fueling for your engine and also save money on fuel economy, win win

Millhaus

JBL930,

Thanks for the reply. I'll check the hose that you mentioned on the side tonight. Where does the side hose run to?

I am not getting any fuel in the air box and I check that hose leading from the WUR to the air box. It is dry.

The sensor was calibrated in fresh air. The AFR reading at calibration is around 84.

JFairman

If the boost enrichment air pressure diaphram in the bottom part of the WUR ruptured you would not get fuel coming out of the vent hole in the top of the WUR because fuel never goes near that diaphram.
The air hose going to that port on the WUR comes from the throttle body and it's only a couple inches long on the late 80's cars. The WUR was mounted in slightly different positions on different year cars.
There is another diaphram in the top part of the WUR, right under the fuel fittings.
This is the diaphram with it's valve that are metering fuel and control the control pressure. If that one ruptures, than fuel will come out of the vent in the top of the WUR that origonally has a short hose going to the air cleaner housing.

You say your car is stock so I don't think you really "need" an adjustable WUR, but thats a matter of opinion. Also if your's is bad then having Brian put new parts in it and make it adjustable is way better than buying a new or good used stock one.
If you have modified the motor with more boost and a modified fuel head to deliver more fuel under boost then it is a really good idea to have the adjustable one to control the AFR's under all driving conditions alot better.

Idle AFR should be around 13.9-14.3:1 when fully warmed up.
My car's AFR is 12:1 on a cold start.
The cold start control pressure is now set at 2.5bar @ 78 degrees outside temperature, and the heating element starts steadily raising the control pressure to lean out the mixture after about 5 seconds.

14.4:1 or leaner and my car starts to get a less smooth idle when fully warmed up.
Anything richer than 13.9:1 is just wasting gas at warm idle, possibly diluting the oil on the cylinder walls with gas, and it smells bad too.
Steady cruise under 50mph should be around the same.
Under load it should get alot richer.
11.5:1-12:1 AFR at full boost from 4000rpm on up to redline is good. It will probably take an adjustable WUR with rpm switch and solenoid and alot of experimenting to get a nice flat AFR curve under boost though.
All engines are a little different.

With 1 bar boost I aim for 11.5:1 on the AFR gauge because you could have some cylinders that are actually around 12.5:1 while others are around 11:1 and it all mixes before the O2 sensor so you won't know it.

JBL930

Good advice above, I was quoting cold start AFR at idle, sorry! However, not sure leaner than 13.9 at idle (when warm) will wash out oil from your cylinders but I'm no expert. 13.5:1 AFR is 2.7%CO which is correct for UK emissions, and recommended by US tuners on this board!
Everything else would be pretty much in line with what i have been told time and again from different tuners. I've attached some Bosch WUR info for your perusal

I've learned something with regards to there being two diaphragms, my WUR started dumping fuel into the airbox and I was told the diaphragm had split, note to those that have changed their airbox, if there is no breather tube off the top of your WUR going somewhere safe then you run the risk of dumping fuel all over your engine if this diaphragm fails, the rest is up to your imagination!

JFairman

The diagram you posted is not a 930 WUR. It is probably for an SC.
There is a lower chamber with a diaphram for boost enrichment like this diagram of a 930 WUR shows.
The small boost pressure hose from the throttle body attaches at the bottom side opening about where the word "diaphram" is.

Boost pressure pushes the lower diaphram, and the spring upwards pushing on the valve diaphram closing off the valve under line "B". Fuel is coming in C, and line B is control pressure going back to the fuel head.
Closing off the fuel flow to B lowers control pressure which lets the control plunger in the fuel head raise exposing more of the metering slits and sending more fuel to the injectors.

...at least thats how i understand it.

I'm not sure where I saved this diagram from... I'll delete it if there's a problem

JBL930

Great diagram JF, i've seen it before but forgot to save it, it's now saved, cheers.
Is the other info on what I posted correct? Warm up control pressures and so on? If it isn't i may as well delete it as it'll just add confusion.