reinartdesign Posted June 13, 2023 Posted June 13, 2023 Some background on our setup 964 Classic Retrofit kit with Dual Condensers. 650-700g R134a (various R134a doesn't have effect on vent temp) 175A High Output Alternator running factory belt setup. We have tried it with both the DC Contactor Installed and without it installed. Current Settings MOD=0 BUT=1 BLO=12v BMD=12.6v BLV=<7v CTG=75A CFN=10A CFO=0A CTS=7C ETC=-2C TBG=30s TBM=50s CLO=10% CHI=90% KP=65 KI=0.01 KD=0.05 KBET=3950 At idle with compressor in highspeed, voltage will drop to around 12.0-12.1V and the compressor will automatically switch to low speed. On throttle (lets say 3000RPM), the alternator isn't able to sustain voltage output above 12.6V (often dipping to 12.4-12.5v) causing compressor to throttle down to CLO. We have tried manipulating CHI to 60-70% but it has no effect. This results in our compressor always running at CLO and the AC system isnt cold (blowing coldest 20 C). Ambient temperature now in Hong Kong is around 30 C with high humidity. Any insight on the cause of our poor performance? The settings we're using are based off some success we've had with the Gunther Werks cars using the Dual Condenser system with a 240A alternator. Quote
Jonny Retrofit Posted June 13, 2023 Posted June 13, 2023 You are losing some voltage somewhere. Review your earth straps, battery negative cable and all positive cable. The 175A unit should easily cover the load of the AC at 3000 RPM. Do you have any other high current loads in the car? Quote
reinartdesign Posted June 14, 2023 Author Posted June 14, 2023 All the earth straps and battery cables are new. Contact surfaces were all sanded before installation. The car has a DSP for the audio which we just unplugged. It also has an electronic suspension which runs a small LCD screen and controller but I imagine this uses minimal power. I was able to get better voltages with the audio removed(13.8-14v charge at idle with AC off). However at 3000RPM with the AC On and compressor running at highspeed, it still dips down to around 12.7-12.8v causing the compressor to throttle down to around 40. Will upgrading to the 240A alternator improve the situation? Also apologies if I posted in the wrong forum. Quote
Jonny Retrofit Posted June 30, 2023 Posted June 30, 2023 Should be ok. ‘Throttle down’ is below 12.6. You can lower the threshold by changing the value in the ECU. Try 12.4. Quote
reinartdesign Posted June 18 Author Posted June 18 Coming back to this we never got the charging issues resolved. Even with the 240A alternator and serpentine belt it still only produces 20A at idle of 800rpm. At idle the AC system drains the battery dropping battery voltage to as low as 11.8v. I've tried all sorts of settings in the AC system but when the compressor is on it just drains more than the alternator is capable of producing. I see everyone saying this alternator can produce 100a at idle but I'm just not seeing how. Quote
reinartdesign Posted June 18 Author Posted June 18 at 2500-3000RPM it produces around 60A max when measured at the alternator Quote
Jonny Retrofit Posted July 3 Posted July 3 This isn't an AC settings issue, it is definitely alternator / charging system. These alternators produce 75/80 amps at idle. Either the 'exciter' isn't working ( which is in the clock instrument) or there is wiring issue or perhaps a voltage regulator issue. Quote
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