PAGE F7 MODIFY CARB.
In this page you can modify the gas carbureation to fine-tune the map created by the autocalibration.
This operation is not mandatory and we strongly suggest to check the carbureation before making any modification.
There are 2 columns in the MODIFY CARB section:
Idle: when the engine’s speed is below 1100
RPM;
Out of idle: when the speed is above 1100 RPM.
Both columns are divided up into 4 boxes showing the engine load.
The boxes are painted in red to show the actual working point of the engine.
EXTRAINJ. SENSITIVITY
The DREAM XXI N ECU converts the extrainjection pulses generated by the petrol ECU into gas injections. However, the petrol extrainjection timings are very short and under some conditions the gas injectors could not fully open, giving thus an inaccurate flow of gas. To avoid this problem you can change the
Extra-
injection sensitivity: when you set the extrainjection fader to the minimum value, the gas
ECU converts the petrol injection timings into gas injection timings without extra-injection
(thus the extra-offset time is 0).
When the fader is set to the maximum, the DREAM XXI N ECU converts the petrol injection timings into gas injection timings with the maximum extra-injection time (extra-offset time is 3.6 ms). The suggested settings for the fader are 0 for CNG systems and middle position for LPG systems.
WEAKENING ON MAZDA
We found out that some Mazda engines under certain conditions switch their injection strategies from sequential to full-group.
When this happens, the petrol injection timings decrease by a 50% and the dot on the map moves to a higher row, pointing at wrong figures. The engine then starts to shake and the car doesn’t run smoothly.
The Weakening on MAZDA lets you set a value that will be subtracted from the figures in the map, taking them back to the right value.
ENRICHMENT IN ACCELERATION
This feature is active only when the bar under the fader is painted in blue: this happens while you are accelerating or decelerating. In these conditions, you can enrich or lean the mixture to enhance the drivability. (You can use this only if you installed an AEB025 pressure sensor).
LEANING ENRICHING
17
18
PROCEDURE FOR VERIFYING CARBUREATION
PROCEDURE FOR VERIFYING
CARBUREATION
Before proceeding with any modifications, first verify that the vehicle runs fine while on petrol, because the Gas injection is based on the Petrol one.
- Start the vehicle on petrol and wait for the engine to reach its normal operating temperature (approximately 90°);
- select the box where you intend to verify carburetion and keep the position of the accelerator steady;
- verify the reading of the petrol fuel trims using an OBDII palm-top;
• if the fuel trim drifts up increasing its value, the petrol control unit has detected a lean carburetion. Therefore, a value that is more or less the same as the increase of the fuel trim should be entered in the corresponding box.
• If the fuel trim drifts down decreasing its value, the petrol control unit has detected rich carburetion, and a negative amount must therefore be entered.
- Verify that the fuel trim show has same reading while on Gas and on Petrol after each modification.
- Repeat this procedure for each single box.
Please note that on-road vehicle testing is necessary to select some boxes.
- switch to gas, trying to get back to the same number of engine revs and returning to the same box;
- verify the reading of the fuel trims;
- if, while on gas, the reading of the fuel trims changes more than 3-4 units from their original value (for example the trim changes from 8% to to 11-12%), correct the carburetion following these rules:
There is no need to modify the carburetion if the fuel trim shows the same reading during gas and petrol operations.
NOTE: it’s important that you perform any modification only while running on petrol.
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