Mazda 2008 MazdaSpeed3 Wartungshandbuch PDF herunterladen (Seite 12)

The above graph is from the same datalog. Boost builds and holds steady at around 17psi across the RPM range but, start-

ing at 3000 RPM, the DIFP starts to drop off. It continues to drop off severely enough that the ECU steps in and closes the

throttle, lowering boost to help limit torque production and fueling demand. Once boost drops a few psi, the CDFP is capable

of building enough pressure to achieve the DIFP targets and the ECU 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 reduce your WOT fueling targets to lower fuel demand. This may not be possible with some

lower quality fuels, since it may cause the combustion to be too lean (hot) which can increase Knock Retard values.

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

reducing fuel demand.

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 in-

take 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:

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Stock CDFP Failure

Throttle Position (%)

DI Fuel Press. (PSI)

Boost (PSI)

RPM

DIFP

Throttle/Boost

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Mazda 2008 MazdaSpeed3 Wartungshandbuch Seite 12