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Re: More MB

In a message dated 98-09-18 06:43:51 EDT, you write:

<< The MAC12D seems to be a clone of the MAC11 with the single omission of
 lambda control.
 The WOT switch provides initial overboost, WGFV control and FFV valve
 control.  The effects are best seen with jumpers attached to the WOT
 input to the ECU - that way you can hold the throttle opening constant
 and see just what the switch does.  Using Orin's digital duty cycle
 display and a diode light on the wastegate frequency valve, it's
 easy to see it affects both - it increases the duty cycle on the fuel
 frequency valve, and it "switches on" wastegate frequency valve control.
As I suspected.  So basically, at WOT, they operate EXACTLY the same, since
the 11b/c ignores O2 sensor input at WOT.  The mods you described, Phil,
should be ok with the stock FVDC tables in the computer.  You have a problem
elsewhere in the system.  To get more fuel (if needed), you can reprogram the
FVDC tables, or reduce Control Pressure (not suggested if you are topping out
already).  If you are running stock boost levels, neither is necessary.  

The fact you are "topping out" the air flap at 4500rpm indicates to me that
your control pressure is off, which could be a system pressure problem (since
CP is a percentage of SP).  You may want to make sure that the "topping out"
isn't giving you a rich, not lean condition at 4500rpm (since WOT FVDC +
topping out usually happens at 5500-6000rpm).  If indeed the TO is happening
with all other systems intact (and truly lean), then adjust control pressure
up, and get the FV DC in the tables increased.  I find a slight increase in DC
makes for a LOT of extra fuel.  And there is certainly enough to handle ANY
mods with a stock boost level (even assuming 1.8bar for euro-spec cars)

The topping out at 4500 sounds like you have a problem in the fuel system.  If
your system and control pressure are OK,  I suggest a tire inner tube to the
turbo oulet hose, and put 15 psi into the system.  Your leak will become

Have you metered the DC while driving the car?  Could you have a bad FV?  Did
you try swapping the fuel head and/or FV?   Did you try swapping the ECU (bad

Yes to all?  Go after that coil.  Have you got a strong signal from your rpm


Scott Justusson
'87 5ktqwRS2
'84 Urq