Porsche Mechanical Fuel Injection - Bosch MFI

Important data from CMA for 2.7 Carrera

The following data is extracted from the Porsche Check, Measure, Adjust Manual

Features

(From CMA Page 7)

Pump Designation :: Bosch 0408 126 019
Throttle valve casing with enlarged bypass bores for idling air; recognized by Solex part number on front surface

Spark Plugs

Bosch W 260 T or W 265 P21
Beru 260/14/3 or 265/14/3 P

Dwell Angle

Bosch distributor : 38 degrees, +/- 3 degrees
marelli distributor : 37 degrees, +/- 3 degrees

Ignition Timing

Set ignition timing at idling speed (900 ± 50 rpm) to TDC.
The vacuum hose must be attached during this operation.
At 6000 rpm, with the vacuum hose removed, the ignition timing must be between 32° and 38° before TDC.

Synchronizing Throttle Valves

Done at 3000rpm, engine at operating temperature

Fully close the air bypass screws, then open 3 half-turns (i.e. 1.5 turns) ** See note below ** Note:

2.4 and 2.7 litre engines, open 3/2 revolutions.
2.4 and 2.7 litre engines with 3.2 mm Ø bore for the bypass passage (without Solex part number on front of throttle valve casing) Open 6/2 - 8/2 turns
Engines with 4 mm Ø bores in the throttle valve casings (Solex number clearly visible) 3/2 - 4/2 turns basic setting.

When adjusting be sure that the air-correction screws are not opened more than 8 half turns.
If the air control screws are opened more than 8 half turns with little change on the synchrometer, the air channels are carboned up and the channels must be cleaned.

Measuring Exhaust Emission

2 Phases : Part Load, then Idling speed
Always perform part-load adjustment first as it has much more effect than idle speed Specifications

Intake Temperature : No Influence
Throttle valve Angle : 9 degrees
Engine RPM : 2400
Gear : 2nd
CO Value : 2.5% - 3.0%

Procedure

Attach a protractor with indicator to the left throttle-valve housing. Set the indicator at zero (hand throttle in zero position).
Bring the engine up to operating temperature (approx. 80 degrees Celcius/Centigrade)
Get the emission test instrument ready and connect according to the manufacturer’s data.
Attach the special tool to the MFI pump :
Using the hand throttle, set the throttle valves at an opening angle of 9 degrees.
Select 2nd gear, clutch in, start engine : (If throttle angle was set with hand throttle, dont touch accelerator)
Release clutch, use brakes to slow down the engine to the required 2400 rpm
drive this way for 30 to 60 seconds, and note the CO reading from the test equipment.
stop the car & switch off engine.

Adjustment of Part Load CO
IMPORTANT : ADJUST ONLY WHEN ENGINE IS NOT RUNNING !!
make adjustments as quickly as possible to avoid heating up the intake manifold.
The adjusting screw for part load is located at the end of the control behind an allen head bolt.

Remove the hex. socket-head bolt.
Using the special tool P 229 c, the adjusting screw on the control-rack head can now be turned. The adjustment screw “clicks” at each 1/12 of a turn.
Target %CO value is 2.5% to 3.0% (13.56 to 13.38 AFR)
For a leaner mixture, turn clockwise. For a richer mixture, turn counterclockwise. Check the CO after every two clicks.
Note: Never press in on the adjusting screw when turning. Any pressure may bend the sensor lever.
The sensor lever is then at the wrong point on the contoured cam and the whole spectrum of the injection pump is altered.
The performance of the engine will be severely impaired.
Re-install the plug on the access to the control rack.
Repeat the part load measurement.

Adjustment of Idling Speed CO
IMPORTANT : ADJUST IDLE CO ONLY AFTER ADJUSTING PART-LOAD CO
The procedure is as follows:

Set the hand throttle at zero.
Let the engine run at idling speed (900 ± 50 rpm).
After the end of a short waiting period, read and note the CO content.
Switch off the engine.
Decide which way to adjust, to achieve 2.5% +/-0.5% CO (From 13.77 to 13.38 AFR)
Using the special tool P 230 c, press in the spring-tensioned adjustment screw on the govenor housing of the injection pump and by turning lightly, let it catch in the slot of the adjusting screw : Remember Idle adjutsment is opposite direction to part load adjustment.
The idling-speed adjusting screw has 6 clicks for one turn. When adjusting turn only 1 to 2 clicks at a time, then measure CO.
Turn counterclockwise for lean, turn clockwise for rich.
Adjusting CO content will change the idle speed. You must correct the idle speed to 900 ± 50 rpm by evenly turning the 6 air-correction screws

Note : Conversion from CO Value to AFR value found here http://www.ratwell.com/technical/AFR.html