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Vavle Clatter? Is it Knocking/Pinging?
Marty,
>From our previous discussions about your late high compression, dual knock
sensor MC engine (Normally uses the Mac14 ECU) installed in your 5000TQ
with the early MC Mac11 ECU. I don't think the clatter you are hearing is
coming from the valves. Without hearing the noise, it is tough to tell of
course :-)
I think you are hearing the engine ping/knock during acceleration and this
corresponds to the car feeling like it is briefly holding back, hesitating
as the ECU backs off the timing. The ECU can not adjust the timing
instantly, so I believe you will hear the knocking/pinging if you run the
Mac11 timing with the late MC engine. This assumes your fuel system is
working correctly and the idle mixture is set right.
I made up an ECU harness adapter to test the Mac11 ECU's in my late 89
200TQ (dual knock sensors, K24 turbo, different camshaft, higher
compression (8:4 to 1) MC engine, with Mac14) and every Mac11 ECU I have
tested will cause the late MC engine to knock/ping when I accelerate at
WOT. This is especially true if you are running higher boost levels greater
than 1.4 bar. As Orin and I have found, the stock Mac11 timing values will
cause knock (sometimes not heard) when the boost is run up to 1.8 bar with
the early MC engine with 7:8 to 1 compression. Running the Mac11 timing
maps with higher boost (1.8 bar) in the late MC engine is going to be way
too advanced.
I don't think you are ever going to get the car to run correctly without
pinging, using the Mac11 timing maps. Hopefully the single knock sensor
setup will work as well, but it should be "ok" as the MB engine in the UK
does have 8:6 to 1 compression and runs a single knock sensor with the
Mac12 ECU which functions the same as the Mac11 with the exception being
there is no O2 sensor control system.
The other issue that may be causing some of this problem, is the
difference in fuel mixture control between the air flow metering assembly
in the early MC and the late MC engine. The late MC engine uses the Bosch #
0 438 121 064, Audi # 034 133 353L air flow meter assembly, the early MC
uses the Bosch 0 438 121 053, Audi # 034 133 353D. The fuel distributors
used on both early and late MC engines are the same, the only difference is
the late MC uses an external fuel pressure regulator setup.
If it were my car, I would change out the air flow metering assembly with
the correct one for that late MC engine, and get a different EPROM
installed with timing maps (more timing retard) that correspond more
closely to the timing maps found in the Mac14. If I remember correctly, you
had the ECU modified by someone in the QLCC group and have a EPROM socket
installed. This would make changing out the EPROM to be a trivial exercise.
Here is a portion of the timing maps from the Mac14 and the Mac11 for
comparison.
First Column is Manifold Pressure (Absolute) the next 16
columns are the Mac14 Premium Timing values,
Before Top Dead Center (BTDC)
Horizontal X axis. The timing map uses the following RPM values
1000 1325 1675 2000 2325 2675 3000 3325 3675 4000 4325 4675 5000 5325
5500 6000
1.5 19 21 21 21 21 21 22 21 21 22 23 25 25 27 29 31
1.43 19 21 21 21 21 21 22 21 21 22 23 25 25 27 29 31
1.35 19 21 21 21 21 21 22 21 21 22 23 25 26 28 30 32
1.29 19 21 21 23 22 22 23 23 24 23 24 25 26 28 30 33
1.22 19 21 21 23 25 26 24 24 24 24 24 25 26 28 31 34
1.15 19 21 23 26 27 28 28 27 26 25 25 25 26 28 32 35
1.08 19 23 24 27 28 29 29 27 27 27 27 27 27 28 32 36
1.01 21 26 28 32 33 33 32 30 29 29 29 29 29 30 33 37
Mac11 Premium Timing values, Before Top Dead Center (BTDC)
1.5 22 24 24 24 24 25 25 23 23 22 23 24 25 31 30 30
1.43 22 24 24 24 24 25 25 23 23 22 23 24 25 31 30 30
1.35 22 24 24 24 24 25 25 23 23 23 24 25 26 32 32 32
1.29 22 24 24 24 24 25 26 24 25 25 26 28 26 33 34 34
1.22 22 24 24 24 22 25 26 25 27 26 27 28 27 33 34 34
1.15 22 24 24 23 22 26 26 25 28 27 28 28 28 33 34 34
1.08 22 24 22 23 24 28 27 29 29 29 29 29 29 33 35 35
1.01 24 25 24 25 27 30 28 30 32 32 32 32 32 36 38 38
HTH
Scott Mockry
1989 200TQ
SJM Auto-Technik
http://www.teleport.com/~scottmo