MBW Posted July 8, 2023 Report Share Posted July 8, 2023 I’m a newbie here but I’ve been a long time user of MoTeC, so I know something about ECU. Recently I started messing with a friend’s car which has a G4X. It’s Miata 1st. gen with a 1.6 motor that is normal aspiration with ITBs. When I looked at a log, I found the idle target rpm fluctuates downward a bit and I can’t figure out why. First I thought the radiator fan was running, but it wasn’t. Besides, since the target rpm goes down, so it wouldn’t make sense even if the fan was running. Also It doesn’t have a powered steering nor an air conditioner, so the relevant settings are all set to off. I figured the ignition PID setting was wrong, but I don't think it caused the problem. The data ia attached. If anyone gives me a clue, it’d be deeply appreciated. Thanks. 0706.pclx Mazda MX5 1.6 G4X Xtreme Plugin改.pclx Quote Link to comment Share on other sites More sharing options...
DerekAE86 Posted July 8, 2023 Report Share Posted July 8, 2023 The "Idle Base Position Table" is strange. It's got RPM as one axis and ECT as the other. (Typically this Table just has ECT as a single axis.) So currently when Idle RPM increases the ISCV closes more, which causes the Idle RPM to drop. Which causes the ISCV to open more, which causes the Idle RPM to increase. It will just gently hunt higher and lower because of that. Is there any reason Idle Control has been set to Open Loop? Closed Loop control would be better. The "Idle Target RPM" table is set so 70deg is 1083rpm and 80deg is 1000rpm. Without seeing the log its hard to say, but maybe the engine is around this tempurature too? Quote Link to comment Share on other sites More sharing options...
MBW Posted July 8, 2023 Author Report Share Posted July 8, 2023 Thank you for the reply. >It will just gently hunt higher and lower because of that. I get that. It was just a trial. I will start using air temp and engine temp as axises which have the biggest impacts on idle control. >Is there any reason Idle Control has been set to Open Loop? Closed Loop control would be better. I though I had set it to closed roop. I'll recheck it. >The "Idle Target RPM" table is set so 70deg is 1083rpm and 80deg is 1000rpm. >Without seeing the log its hard to say, but maybe the engine is around this tempurature too? Sorry, the log file is too large to attach. But, nah, the motor was totally warmed up, around 90deg. So, the rpm target should have stayed 1000, instead of going back and forth between 963 and 1010. Quote Link to comment Share on other sites More sharing options...
DerekAE86 Posted July 8, 2023 Report Share Posted July 8, 2023 Are you sure it's not the engine fans? The tune shows there is a fan on Ign4 output and second fan on Aux2 output. Fan 1 comes on at 91deg and goes off at 88deg Fan 2 comes on at 92deg and goes off at 88deg Can you check the log for Ign4 and Aux2 outputs and see if they are switching and if it lines up to the Idle Target change? Quote Link to comment Share on other sites More sharing options...
MBW Posted July 9, 2023 Author Report Share Posted July 9, 2023 I didn’t know it had a weird configuration of fans. It was done by the owner, my friend. The car has only one fan, so obviously it’s erratic. And, you guessed perfectly correctly!! The fan 1, which doesn’t exist, turns out to be messing up the target rpm. Big thanks to you!!! Quote Link to comment Share on other sites More sharing options...
DerekAE86 Posted July 9, 2023 Report Share Posted July 9, 2023 You're welcome. Quote Link to comment Share on other sites More sharing options...
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