Mazda 2008 MazdaSpeed3 Wartungshandbuch PDF herunterladen (Seite 8)

The above graph is from the same datalog. Boost builds and holds steady at around 17psi

across the RPM range, but starting at 3000 RPM, the DIFP starts to drop off, then continues to drop

off severely enough that the ECU steps in and closes the throttle (lowering boost) to help limit

torque production...and thus fueling demand. Once boost drops a few psi, the CDFP is capable of

building enough pressure to achieve the DIFP targets and the ECU then allows the throttle to open

fully once again.

Using AccessTUNER Race, you have a two strategies that can be employed (individually or

combined) in order to work around this issue until an upgraded CDFP is installed.

1) You can incrementally lean our your WOT fueling targets to reduce fueling demands. This

may not be possible with some lower fuel qualities since it may cause to lean (hot) of a

combustion and Knock Retard values can increase when this happens.

2) You can incrementally decrease your WOT boost (or load) targets until you have the engine

producing less torque, reducing fueling demands.

Excessive carbon build up on your intake valves.

DISI engines are unique in that the fuel injector sprays directly into the combustion

chamber and not on top of the intake valve from the intake port/runner (as is done with a port-

injection engine). With a port-injection engine, the fuel injector actually keeps the intake valves

relatively clean by spraying fuel (a solvent) directly onto the intake valves. This constant spraying

constantly cleans carbon and other deposits from the valves.

Without fuel being sprayed directly onto the intake valves, excessive deposits are allowed

to form. These deposits can build to an inch or more in diameter near the head of the valve. This

excess build up can cause the following issues:

– Poor or erratic idle

– Cylinder or engine miss-fires

200

400

600

800

1000

1200

1400

1600

1800

2000

100

Stock CDFP Failure

Throttle Position (%)

DI Fuel Press. (PSI)

Boost (PSI)

RPM

DIFP

Throttle/Boost

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 27 28

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Mazda 2008 MazdaSpeed3 Wartungshandbuch Seite 8