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Diesel Chips - the Good & the Bad

Diesel Chip

Boost Tubes and Diesel Chips

The "boost tube" is actually a boost-bleed device. This is installed in the boost reference line to the wastegate actuator, and provides a controlled leak to atmosphere of the boost air signal going to the diaphragm portion of the actuator. Boost increases because the diaphragm does not "see" the full level of boost actually present in the intake manifold. But the real problem is that the actuator itself is a weak actuator, with only about 5 psi of pre-load, meaning that the wastegate will have the propensity to blow open under moderate exhaust backpressure. With a low wastegate-seat pressure, the wastegate will start to lift off of the seat prematurely. This kills the midrange torque potential of your engine. Ford uses a computer-regulated leak of their own to manage the boost at various rpms, sometimes as low as 5 psi and as high as 18 psi. The controlled leak that some diesel chip manufactures provide is in addition to the Ford valve, and will allow the turbo to achieve a higher level of boost, but it will be at a higher than optimum rpm. The Big Head Actuator resolves this by essentially doubling the diaphragm area of the actuator, doubling the spring rate and more than doubling the pre-load. This provides more holding force as exhaust backpressure increases and keeping boost optimal through the midrange of engine operation, which translates into more midrange torque with proper fuel management. Proper management of the boost curve requires a manipulation of the values in the calibration tables. A boost-leak device is an indication that a diesel chip manufacturer does not know how to manipulate these tables. This is further indicated by excessive smoke. If a programmer does not know how to access all of the necessary tables to adjust the boost curve, then the boost is not being optimally managed. Another side effect to a lack of proper boost control is the SES light that may occur with boost conditions that exceed a preset Ford value. Because this value is set in the Ford firmware, the only true way to manage it is by electronically clamping the value sent from the MAP sensor to the ECU.

Gasoline engines operate within a narrow air/fuel ratio range of approximately 12:1 to 15:1, although some modern "lean-burn" technology engines have been able to achieve significantly leaner air/fuel ratios. Diesels can operate with a broader range as rich as 15:1 or as lean as 60:1, however, going richer than about 22:1 to 25:l produces excessive temperature, soot, smoke, and poor fuel economy. Some aftermarket diesel chip manufactures simply dump in excessive fuel for power, causing the engine to operate in the undesirable rich range, as evidenced by plumes of black smoke. Thermal efficiency of diesels can be, and is, further enhanced with turbocharging to increase the available air (oxygen) to support combustion of more fuel. Gasoline engines cannot tolerate significantly higher cylinder pressure from turbocharging without creating preignition and/or detonation unless high-octane or ultra-high-octane gasoline is used.