Vincent Posted December 18, 2006 Report Share Posted December 18, 2006 Hi, I have a link plug in ecu in my 99 impreza GTT. The car runs great on the current mapping, but there is a little problem. When the two fans of the motor coolant cooler turned on by 92 C and I lift my foot of the gas or kick in the clutch the motor rpm drops to 480 and the volts on my volt meter drops from 14,3 to 9,7. and the motor turns off. I drive with a race coolant cooler, this is bigger than the OEM. What seems to be the problem is that the fans are taking away the volts from the injectors. I have raised the Volt correction to 21 but this doesn't work. I don't know what to do? Greetings, Vincent the Netherlands Quote Link to comment Share on other sites More sharing options...
ashesman Posted December 20, 2006 Report Share Posted December 20, 2006 The problem here is an idle speed control issue. The idle speed needs to be increased when the fans turn on to allow for the increased electrical load. You may also need to look at the amount of current the fans are drawing to determine why the battery voltage is getting low. Is the battery good? It should be able to maintain more than 9.7 volts with reasonable electrical load even if the alternator is not charging. Is the ECU shutting down, is the engine leaning out and stopping, or is it stalling due to not enough air for the amount of load? Quote Link to comment Share on other sites More sharing options...
Vincent Posted December 20, 2006 Author Report Share Posted December 20, 2006 Hi Ashley, I have my idle speed rpm set on 850 rpm. The battery is good, I have replaced the old one because that was my first thought to. What happens is that the moment the fans are on and I hit the clutch or put my foot of the gas the rpm drops to 470 and the engine runs to lean 16,2 - 17,1 on the AEM wideband. The voltage drops to 9,7 on the voltmeter. I have driven with this set up for almost a year with the OEM ecu, no problems accured. Thanks, Vincent Quote Link to comment Share on other sites More sharing options...
ashesman Posted December 21, 2006 Report Share Posted December 21, 2006 OK, the OEM ECU cant be compared here... they have spent millions tuning it to suit your exact engine!  You can try tuning the lower RPM and vacuum zones to try and correct that mixture going lean. Also adding some advance in the lower areas may improve this. Make sure you have the volt correction set correctly. The way to do this is to make sure that your mixture stays reasonably constant as voltage decreases, but load may also remain constant (ie fans must not come on). What you need is more air bled into the engine. This is usually acheived by stepping up idle when the fan comes on. All factory ECU's step idle up when the fan is turned on. The adjustment is called 'Fan Step' I think. Quote Link to comment Share on other sites More sharing options...
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