Mass air flow - Revision history

Nyet: /* Bosch vs. Hitachi */

2020-10-11T19:24:15Z

Bosch vs. Hitachi

← Older revision		Revision as of 19:24, 11 October 2020
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	===Bosch vs. Hitachi===		===Bosch vs. Hitachi===

			B5 S4s and RS4s came with [[Generations \| several different types]] of MAF sensors
⚫	~~B5 S4s came with [[Generations \| two different types]] of MAF sensors - Bosch (078 906 461B) and Hitachi (06C 133 471A); both~~ are film-type MAFs. Each has totally different signal characteristics and are not compatible, even if properly rewired. [[A-Box]]/[[B-Box]] cars (MY2000) came with Bosch MAFs. [[H-Box]]/[[J-Box]] (MY2001), [[M-Box]]/[[L-Box]] (MY2001.5), and [[T-Box]]/[[AA-Box]] (MY2002) cars came with Hitachi MAFs.
			* Bosch 078 906 461B (S4)
			* Bosch 077 133 471K(X) (RS4)
			* Hitachi 06C 133 471A

		⚫	All are film-type MAFs. Each has totally different signal characteristics and are not compatible, even if properly rewired. [[A-Box]]/[[B-Box]] cars (MY2000) came with Bosch MAFs. [[H-Box]]/[[J-Box]] (MY2001), [[M-Box]]/[[L-Box]] (MY2001.5), and [[T-Box]]/[[AA-Box]] (MY2002) cars came with Hitachi MAFs.

	{\| class="wikitable"		{\| class="wikitable"

Nyet: /* Effect on Velocity */

2013-05-25T17:07:24Z

Effect on Velocity

← Older revision		Revision as of 17:07, 25 May 2013
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	* Sensor value absolute maximums are 364.08 on VAGCOM and 499 on ECUx.		* Sensor value absolute maximums are 364.08 on VAGCOM and 499 on ECUx.
	* S4 stock MLHFM ends at 1213.1 kg/hr, or 337 g/sec		* S4 stock MLHFM ends at 1213.1 kg/hr, or 337 g/sec
	* RS4 stock MLHFM ends at 1996.1 kg/hr, or ~~554~~.5 g/sec		* RS4 stock MLHFM ends at 1996.1 kg/hr. With MLOFS, that is 1796.1, or 498.9 g/sec
	* Note that some programs scale g/sec readings, so what ECUx/VAG-COM reports can't always be trusted.		* Note that some programs scale g/sec readings, so what ECUx/VAG-COM reports can't always be trusted.

Nyet: /* Effect on Velocity */

2013-05-25T00:44:41Z

Effect on Velocity

← Older revision		Revision as of 00:44, 25 May 2013
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	* VAGCOM limit seems to be 318ish on M/T-box, 335ish for M-box, high 320s for A box.		* VAGCOM limit seems to be 318ish on M/T-box, 335ish for M-box, high 320s for A box.
	* Sensor value absolute maximums are 364.08 on VAGCOM and 499 on ECUx.		* Sensor value absolute maximums are 364.08 on VAGCOM and 499 on ECUx.
	* ~~M-box~~ stock MLHFM ends at ~~1214~~.1 kg/hr, or 337 g/sec.		* S4 stock MLHFM ends at 1213.1 kg/hr, or 337 g/sec
			* RS4 stock MLHFM ends at 1996.1 kg/hr, or 554.5 g/sec
	* Note that some programs scale g/sec readings, so what ECUx/VAG-COM reports can't always be trusted.		* Note that some programs scale g/sec readings, so what ECUx/VAG-COM reports can't always be trusted.

Nyet: /* Effect on Velocity */

2011-08-07T02:22:25Z

Effect on Velocity

← Older revision		Revision as of 02:22, 7 August 2011
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	* VAGCOM limit seems to be 318ish on M/T-box, 335ish for M-box, high 320s for A box.		* VAGCOM limit seems to be 318ish on M/T-box, 335ish for M-box, high 320s for A box.
	* Sensor value absolute maximums are 364.08 on VAGCOM and 499 on ECUx.		* Sensor value absolute maximums are 364.08 on VAGCOM and 499 on ECUx.
			* M-box stock MLHFM ends at 1214.1 kg/hr, or 337 g/sec.
	* Note that some programs scale g/sec readings, so what ECUx/VAG-COM reports can't always be trusted.		* Note that some programs scale g/sec readings, so what ECUx/VAG-COM reports can't always be trusted.

Nyet: /* Effect on Velocity */

2011-08-07T02:21:37Z

Effect on Velocity

← Older revision		Revision as of 02:21, 7 August 2011
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	\|Stage 3- \|\|S4 \|\|73mm\|\|310 g/sec\|\| 135 mph		\|Stage 3- \|\|S4 \|\|73mm\|\|310 g/sec\|\| 135 mph
	\|-		\|-
	\|5V at sensor\|\|S4 \|\|73mm\|\|~~364?~~ g/sec\|\|~~159~~ mph		\|5V at sensor\|\|S4 \|\|73mm\|\|337 g/sec\|\|147 mph
	\|-		\|-
	\|5V at sensor\|\|RS4\|\|83mm\|\|499 g/sec\|\|168 mph		\|5V at sensor\|\|RS4\|\|83mm\|\|499 g/sec\|\|168 mph

Nyet: /* MAF and load */

2011-04-05T00:25:44Z

MAF and load

← Older revision		Revision as of 00:25, 5 April 2011
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	*AWE actual dimensions are 77mm (inlet) to 100mm at sensor. It reads roughly equivalent to an 84mm-86mm MAF, but the response isn't exactly equivalent at all velocities.		*AWE actual dimensions are 77mm (inlet) to 100mm at sensor. It reads roughly equivalent to an 84mm-86mm MAF, but the response isn't exactly equivalent at all velocities.

	===MAF and load===		===MAF and [[load]]===
	{{Load}}		{{Load}}

Nyet: /* MAF and fueling */

2011-04-05T00:22:34Z

MAF and fueling

← Older revision		Revision as of 00:22, 5 April 2011
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	*AWE actual dimensions are 77mm (inlet) to 100mm at sensor. It reads roughly equivalent to an 84mm-86mm MAF, but the response isn't exactly equivalent at all velocities.		*AWE actual dimensions are 77mm (inlet) to 100mm at sensor. It reads roughly equivalent to an 84mm-86mm MAF, but the response isn't exactly equivalent at all velocities.

			===MAF and load===
			{{Load}}

	===MAF and fueling===		===MAF and fueling===

Nyet at 01:06, 13 January 2011

2011-01-13T01:06:13Z

← Older revision		Revision as of 01:06, 13 January 2011
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	===Temperature (IAT) effect on MAF readings===		===Temperature (IAT) effect on MAF readings===

	Because of their design, both the Bosch and Hitachi MAF correct for ambient temperature, so the ECU does not use the IAT sensor in its load calculations.		Because of their design, both the Bosch and Hitachi MAF correct for ambient temperature, so the ECU does not use the IAT sensor in its load calculations.

Nyet: update $tag$

2011-01-13T01:01:02Z

update <math> tag

← Older revision		Revision as of 01:01, 13 January 2011
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	==General information==		==General information==

	A mass air flow (or MAF) sensor placed just before the intake manifold measures the instantaneous rate of air entering the combustion chamber. This is done using a thin wire or film suspended in the air stream.		A mass air flow (or MAF) sensor placed just before the intake manifold measures the instantaneous rate of air entering the combustion chamber. This is done using a thin wire or film suspended in the air stream.

Nyet: /* S4 specific information */

2010-02-18T19:36:07Z

S4 specific information

← Older revision		Revision as of 19:36, 18 February 2010
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	==S4 specific information==		==S4 specific information==
	The B5 S4's Bosch Motronic ME7.1 ECU uses a mass air flow based fuel injection system. During [[open loop]] (engine warm-up and wide open throttle) operation, the MAF tells the ECU how much fuel to deliver to keep the [[air fuel ratio]] at the desired level. Generally, [[open loop]] fuel ratios are not stoichiometric, so narrow band O2 sensors can not be used for this. Thus, for proper functioning, MAF readings are critical for proper [[open loop]] behavior; there is no way for ME7.1 to detect if the fueling is off.		The B5 S4's Bosch Motronic ME7.1 ECU uses a mass air flow based fuel injection system. During [[open loop]] (for example, during engine warm-up and wide open throttle) operation, the MAF tells the ECU how much fuel to deliver to keep the [[air fuel ratio]] at the desired level. Generally, [[open loop]] fuel ratios are not stoichiometric, so narrow band O2 sensors can not be used for this. Thus, for proper functioning, MAF readings are critical for proper [[open loop]] behavior; there is no way for ME7.1 to detect if the fueling is off.

	Unlike wideband O2 sensor equipped cars, the ME7.1's narrow band O2 readings are ignored during open loop operation. The [[O2 sensor]]s (along with MAF readings) are used to determine fueling only during [[closed loop]] operation (idle and partial throttle). Note that since MAF readings are also used during closed loop operation, [[long term fuel trim]]s (or LTFTs) may be affected by faulty or incorrectly tuned MAF setups, including the use of [[blow off valve]]s (or BOVs).		Unlike wideband O2 sensor equipped cars, the ME7.1's narrow band O2 readings are ignored during open loop operation. The [[O2 sensor]]s (along with MAF readings) are used to determine fueling only during [[closed loop]] operation (idle and partial throttle). Note that since MAF readings are also used during closed loop operation, [[long term fuel trim]]s (or LTFTs) may be affected by faulty or incorrectly tuned MAF setups, including the use of [[blow off valve]]s (or BOVs).

Mass air flow - Revision history

Nyet: /* Bosch vs. Hitachi */

Nyet: /* Effect on Velocity */

Nyet: /* Effect on Velocity */

Nyet: /* Effect on Velocity */

Nyet: /* Effect on Velocity */

Nyet: /* MAF and load */

Nyet: /* MAF and fueling */

Nyet at 01:06, 13 January 2011

Nyet: update tag

Nyet: /* S4 specific information */

Nyet: update $tag$