Re: 4KTQ Conversion Questions

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <4.1.19991102093006.01900240@mail.teleport.com> Scott Mockry writes:

> The early (1/85-7/85) '86 model year 5000TQ with the MC engine used a fuel
> distributor with banjo type injector lines and according to the Bosch parts
> catalog, the replacement (rebuilt) fuel distributor "FD70X" for this early
> MC engine is also shown as the replacement part for the US 83-85 ur-quattro
> with the 2.144cc WX Turbo engine.
>
> This would seem to indicate the ur-quattro fuel distributor would work on
> the MC engine.

Simplistic, from my point of view.  The fuel metering head you refer
to is the -147 (Bosch numbering) unit - my ur-quattro already has the
-153 (Bosch again) fitted to the MC-2 engine.

> The Bosch parts book does list a different air flow metering assembly for
> these two vehicles, as well as different warm up regulators.

That's essentially just a different piece of plastic because of the
different air filter.

>  I have not compared the MC air flow meter assembly side by side with the
> ur-quattro air flow meter, but when the MC part is compared to the CIS-E
> air flow meter assembly (87 5000S, non turbo), the MC part has a
> larger/wider opening near the top of the inlet funnel (4.70 in diameter
> versus 4.47in dia.) which would indicate the CIS-E air flow meter would top
> out earlier with less air flow than the MC air flow meter.

True.  Although both are loosely referred to as '80mm' units by Bosch
literature.

> The control pressure on top of the fuel distributor plunger as set by the
> warm up regulator will also dictate how far the air flow plate will be
> pushed upward for a given air flow rate into the engine. The MC engine warm
> up regulator incorporates some altitude correction mixture control.
>
> The later dual knock sensor MC engine (89-90 200TQ) uses the same fuel
> distributor as the earlier 86-88 5000TQ MC engine, but uses an externally
> mounted system fuel pressure regulator instead of the one inside the fuel
> distributor. The dual knock MC also uses a different air flow meter
> assembly part number.

Sure?  The ur-quattro changes from -147 to -153.

> One nice feature found on the MC air flow meter, is the potentiometer
> (variable resistor) mounted on the pivot shaft, which can give you a
> relative indication of mass air flow into the engine, (i.e. how far up the
> air flow plate is moving upward) under full throttle near engine redline.
> You can connect a voltmeter on the 5kTQ potentiometer to measure this air
> flow plate travel as the 5kTQ uses this varying voltage signal for the trip
> computer MPG calculations.
>
> If you use the MC air flow meter assembly on the 4KTQ project, a ohm meter
> can be used to measure the travel to give you an idea if you are getting
> close to topping out the air flow meter for a given boost level.

Yup.  I've measured four units using a Fluke DVM and Audi's 1248(?)
calibration unit - accuracy is better than 1%, which is quite incredible
for an automotive component.  The resistor lands are laser-cut.

> As mentioned by others, the MC Engine control unit diddles with the freq
> valve duty cycle to change the differential pressure across the fuel
> distributor plunger slit opening, as the manifold boost pressure rises to
> richen up the mixture. Using the MC Engine/ECU/Fuel system components in
> the 4KTQ project would be my recommendation for best drive ability and
> operation at modest boost levels.

Have to agree, although I suspect the fuel duty cycle calculation at WOT
would need fine tuning to accomodate volumetric efficiency changes.

--
 Phil Payne
 UK Audi quattro Owners Club
 Phone: 07785 302803   Fax: 0870 0883933