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Re: 88 MB Urq questions

I dont know if this has any bearing on the current thread, Not often getting
the chance to give my 82 urq it's head, I was on a really good Country Lane
(B road) the other day where I could open up fully without too much fuss.

I got the Impression that the car would not pull more than 5,000rpm in 5th
gear. Which was about 105 mph.

I suppose the question is ?, Was it me !!!!!!!!!!!!!!!!!!!! or was it the
Car !!!!!!!!!!!!!!!!!


-----Original Message-----
From: Lino M. Valadas <valadasl@osha.igs.net>
To: Orin Eman <orin@wolfenet.com>; Phil Payne
Cc: orin@wolfenet.com <orin@wolfenet.com>; quattro@coimbra.ans.net
<quattro@coimbra.ans.net>; john_robinson@
Date: 16 September 1998 18:36
Subject: Re: 88 MB Urq questions

>>> > As for the US MC engine, it forgets about the O2 sensor pretty much
>>> > as soon as you go on boost and uses one of two RPM based duty cycle
>>> > for the frequency valve... (one table for low boost, one for
>>> > not so low boost levels).  There is no carry forword of anything
>>> > by the O2 sensor to on-boost behavior.
>>> As you showed, the MAC12D is a cut-down MAC11.  I would not expect any
>>> carry-forward here.
>>I just remembered something else that may be of interest.  The MAC11 uses
>>a base duty cycle of 50% for controlling the mixture via the O2 sensor.
>>The MAC14 (some 89 MC engines and later) has an RPM/MAP based table
>>of base duty cycles!  So, the fuel metering needs compensation to
>>try to maintain a given A/F ratio.
>I have been following this thread with interest, and I would like to put
>some questions up for grabs regarding my Ur-Q.
>The previous owner appears to have replaced the engine with a MC, and
>definitely installed a MAC11b on my 83 Ur-Q.
>My car has a problem similar to the one reported by Phil on John's car.  In
>my case it accelerates rapidly until it gets to about 4500-5000 RPM and
>sits there surging taking forever to get to 6000 RPM.
>The MAC11 seems to be controlling some functions like timing, but how can
>control the fuel management if there is no duty cycle frequency valve.
>I'm thinking of installing one and observe the results any thoughts.
>There is a solenoid valve controlling vacuum at the warm-up valve,  I can't
>get any info on this system on Bentley's nor Haynes.  It turns vacuum on at
>the warm-up valve when the ignition is on, but that all I know.  Does
>anybody have more info on its function?  Any information would be
>86 5ktqw
>83 Ur_Q