maffrequencylimits
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maffrequencylimits [2009/07/20 07:58] twdorris |
maffrequencylimits [2009/07/20 08:00] twdorris |
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| A stock, unhacked EVO8 MAS (effectively the same as the 3G Eclipse MAS) was designed to operate even higher! You'd expect overflow on EVO8 MAS around 3000hz (we think...I'm not sure I've actually seen an EVO8 MAS overrun). That frequency represents roughly 420 lps (about 890 cfm) of volumetric airflow. At standard temperature (around 77F) and sealevel pressure, that's about 500 gm/sec (66 lb/min) of mass airflow. | A stock, unhacked EVO8 MAS (effectively the same as the 3G Eclipse MAS) was designed to operate even higher! You'd expect overflow on EVO8 MAS around 3000hz (we think...I'm not sure I've actually seen an EVO8 MAS overrun). That frequency represents roughly 420 lps (about 890 cfm) of volumetric airflow. At standard temperature (around 77F) and sealevel pressure, that's about 500 gm/sec (66 lb/min) of mass airflow. | ||
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| ==== Summary ==== | ==== Summary ==== | ||
| - | ^MAF ^ Freq limit ^ Volumetric limit ^ Mass limit ^ | + | ^MAS ^ Freq limit ^ Volumetric limit ^ Mass limit ^ |
| |1G DSM | 2000hz|180 lps (380 cfm) |210 gm/sec (28 lb/min) | | |1G DSM | 2000hz|180 lps (380 cfm) |210 gm/sec (28 lb/min) | | ||
| |2G DSM | 2700hz|320 lps (680 cfm) |375 gm/sec (50 lb/min) | | |2G DSM | 2700hz|320 lps (680 cfm) |375 gm/sec (50 lb/min) | | ||
| |EVO8 | 3000hz|420 lps (890 cfm) |500 gm/sec (66 lb/min) | | |EVO8 | 3000hz|420 lps (890 cfm) |500 gm/sec (66 lb/min) | | ||
| - | When running one of these MAFs anywhere near these limits, use ECMLink's MAF Clamp function. Read the help files and forums for more information. By using this function properly, you can effectively remove the upper airflow limitation of these MAF sensors. Even so, it's highly recommended that the 1G DSM MAF not be used simply because its limit is too low to produce reliable MAF Clamp operation when running substantially more airflow than the sensor was designed to meter. | + | When running one of these MAF sensors anywhere near these limits, use ECMLink's MAFClamp function. Read the help files and forums for more information. By using this function properly, you can effectively remove the upper airflow limitation of these MAF sensors. Even so, it's highly recommended that the 1G DSM MAF not be used simply because its limit is too low to produce reliable MAFClamp operation when running substantially more airflow than the sensor was designed to meter. |
| - | ===== GM MAFs ===== | + | ===== GM MAF sensors ===== |
| - | The two most common GM MAFs used on our DSMs are the 3" and 3.5" MAFs, part numbers 25180303 and 25179711, respectively. These sensors operate fundamentally different than the Mitsubishi MAFs. The GM MAFs work by measuring mass airflow directly. They do not need temperature and baro data because they're not measuring volume. They are reporting air mass directly as a frequency. | + | The two most common GM MAF sensors used on our DSMs are the 3" and 3.5", part numbers 25180303 and 25179711, respectively. These sensors operate fundamentally different than the Mitsubishi MAF sensors. The GM MAF sensors work by measuring mass airflow directly. They do not need temperature and baro data because they're not measuring volume. They are reporting air mass directly as a frequency. |
| - | The biggest problem, IMO, with these MAFs is that this frequency to mass mapping is non-linear. So as airflow increases, it takes less and less change in frequency to present a larger and larger change in air mass. This makes the system very sensitive to fluctuations in frequency output from the sensor. | + | The biggest problem, IMO, with these MAF sensors is that this frequency to mass mapping is non-linear. So as airflow increases, it takes less and less change in frequency to present a larger and larger change in air mass. This makes the system very sensitive to fluctuations in frequency output from the sensor. |
| Neither a MAF Translator nor the ECMLink V3 GM MAF cable allow you to see the raw GM MAF sensor frequency directly. The MAF Translator provides a translation to stock DSM-like frequencies, while the ECMLink V3 GM MAF cable provides a simpler translation that produces raw frequencies that are quite different (but that the ECMLink V3 ECU code knows how to handle). So it's best to avoid talking about limiting-frequencies when discussing a GM MAF sensor when used on a DSM and rather just talk about air-mass metering capability. | Neither a MAF Translator nor the ECMLink V3 GM MAF cable allow you to see the raw GM MAF sensor frequency directly. The MAF Translator provides a translation to stock DSM-like frequencies, while the ECMLink V3 GM MAF cable provides a simpler translation that produces raw frequencies that are quite different (but that the ECMLink V3 ECU code knows how to handle). So it's best to avoid talking about limiting-frequencies when discussing a GM MAF sensor when used on a DSM and rather just talk about air-mass metering capability. | ||
maffrequencylimits.txt · Last modified: 2024/03/15 11:16 (external edit)
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