Changes by last author:
Changed:
| Newer cars with air conditioning compressor has 2 speed fans (low speed when A/C on, and for up to some temperature point, when high speed fans is powered up). Also A/C has MAP sensor for monitoring pressure inside the A/C system... |
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Newer cars with air conditioning compressor has 2 speed fans
* low speed when A/C on * above certain temp, high speed fans is powered up |
| Also, when A/C is turned on, idle rpm must rise for about 200rpm... And it must turn off A/C on higher engine loads and when rpm passes like 4000rpm so it wouldn't destroy A/C compressor... |
| Also A/C has MAP sensor for monitoring pressure inside the A/C system. |
| Has VEMS ability to control this? So you must have 2 stage cooling fan outputs like first stage on 94 degrees and second stage (fast speed) on 97 degres of CTS... Also first speed fans speed must be on when A/C is on and car is standing still...As a rule the fan is NOT on until the refrigerant PSI is over a set point. Most have a switch that will turn on the fan by them self and will also shut down the compressor if the refrigerant PSI is too low. (in case of a leak). but some very old systems are dumb and missing the PSI fan switch |
| MembersPage/MarcellGal/PowerAndTraction/AirConditioner has 3 fan speeds, wether which node of the 2 series power-resistors get +12V supply. |
| The reason for turning of A/C above 4000rpm is the power also... But the main reason is saving compressor... It could destroy something if the pressure in the A/C system rises to much on high RPMs... |
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* The high-speed is automatically (because relay is wired that way) turned on
** when refrigerant > 18 bar ** or coolant temp gets high. Activate by radiator CLT temp switch. The engine-head CLT sensor is pretty bad idea for this. Why would you turn on radiator fan when radiator is cold ? It does happen when you switch on ignition after engine had been stopped for 5-10 mins The low-speed gets on whenever the AC clutch is engaged. So the ECU need not be involved at all to achieve this multi-speed fancontrol. Maybe make some more detailed plan with exact ECU output functions. VEMS firmware ability for related control * when A/C is turned on, idle rpm must rise appr +200 RPM ** this would be sane. There is an experimental automagic "sense when idle struggles to maintain target andapply afterstart RPM to raise target" in 1.1.32 and above (the problem in the expetimental 1.1.28-1.1.32 was found so 1.1.33 should be fine, though still not labelled "production") ** explicit input => raised idleRPM can be achieved by the full table+config switch. Besides the RPM target, the reference positions can be changed as well, even the PID * turn off A/C on higher engine loads and when RPM > 4000 so it wouldn't destroy A/C compressor. Also, some more engine power ** it is quite trivial to enable a miscoutput from 500 .. 4400 RPM, but histeresys would be nice to avoid too many on-off-on transients during agressive driving session ---- Obsolete: Consider the above and drop or restructure this. Instead of a short-story, split to sections, relay outputs listed 1-by-1, as on MembersPage/MarcellGal/PowerAndTraction/AirConditioner Than list necessary ECU output functions. The ECU should not need more than * 1 miscoutput for AC-clutch enable * 1 input for full config+table switch So you must have 2 stage cooling fan outputs like first stage on 94 degrees and second stage (fast speed) on 97 degres of CTS... Also first speed fans speed must be on when A/C is on and car is standing still...As a rule the fan is NOT on until the refrigerant PSI is over a set point. Most have a switch that will turn on the fan by them self and will also shut down the compressor if the refrigerant PSI is too low. (in case of a leak). but some very old systems are dumb and missing the PSI fan switch ---- |