Author Topic: high altitude WUR upgrade?  (Read 251 times)


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  • Location: Salt Lake City, Utah
high altitude WUR upgrade?
« on: 21 August 2019, 07:50 PM »
I recently got a 1977 6.9 parts car that had a High Altitude WUR (HAWUR) installed by the dealer when new.  Apparently this was something that MB did at the time for emissions reasons among other things. It has the exact same fuel distributor as my car though it's a US car, not Euro. 

Would it make sense for me to run the HAWUR in my car?  If yes what improvements would be expected?  And what happens are lower altitudes?  My driving is overwhelmingly high altitude, say over 5000 or 6000 ft. Thanks!
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0


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Re: high altitude WUR upgrade?
« Reply #1 on: 24 August 2019, 03:23 AM »
I lived at 1600m for more than a decade and my C107 came as Johannesburg (South Africa) delivered car ("standard" M117).
WUR is standard type but there are no idle emission devices too.
I had to adjust idle CO to a bit lower value as absence of oxygen required less fuel.

I am not sure what the difference is between the HAWUR and WUR, I can only presume the slope of fuel delivery is a bit leaner thus perhaps starting pressure is a bit higher and its warm pressure is higher too.
If driving at high altitude is prevalent, I'd be keen to have it working correct.

What is the stamped pn on it?
Vitamin C for SL... the SLC