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Discussion in 'Car Talk' started by Izso, Jul 12, 2017.
ECU does not compensate?
So the cooling fan turn on, causing the alternator load to increase, which pulls the engine RPM down, causing the voltage to drop, or do you suspect the voltage drop from the fan turning on is causing the engine RPM to drop?
Your engine running on stock ecu right. And the idle control valve working?
ECU only controls the idle valve when the fan turns on to compensate for the increase alternator load
When there is high draw of current, idling speed do drop. Just like when we switch on the head lights, idling speed dips a little.....
Yup idle control valve works perfectly fine, the RPM drop is enough till the level of stalling the engine though.
That is exactly what happened. Latest experiment, i drove the car without A/C for full trip, the RPM is very stable and alive, except when the cooling fan kicked in again and the RPM dips lower, causing the voltage to drop. Would really like to try the pulley first and feedback here.
Some other 1JZ converted E46 uses aftermarket fan instead of original fan, they do not face this kind of issues.
Is your cooling fan controlled by ECU or is it a seperate switch? Maybe you can try pasang an FICD which turns on following the fan, to prevent your engine RPM from stalling due to the increased load placed by the alternator. If you were to undersize the alternator pulley, the load on the engine placed by the alternator will be EVEN greater. You are using E46 original fan or 1jz fan?
Wow! then need one FICD for air con and another for the fan......
Yeah that's what I'm thinking. I am not sure, but it is quite common for these euro cars to have a damn powerful radiator fan, but with a variable speed controller as well, which is controlled directly by the ECU. On idle they rarely go up to high speed, and usually they turn on for awhile then shut off. Once you swapped out the engine and ECU, I suspect they might be running the fan direct power, meaning max speed at all times, and those fans really are quite huge and eats up loads of amps, which might be what is causing the alternator load to be so high until the engine at idle is not producing enough power to actually run the alternator at that load.
Using E46 original fan, which has high and low speed fan mode. My problem is not with idling, the car's voltage is normal with A/C off and fan is not kicked in. If i turn both on (fan and A/C), both accessories drain a lots of juice from the alternator, especially when i am in D gear and waiting by the traffic. Driving without both A/C has no signs of voltage drop or what so ever, in fact, voltage is at optimum level, 13.7.
How does the FICD helps with my situation, from what i know so far, it supposed to bypass the throttle or operates the throttle butterfly directly. My issue right now is not engine stalled at idle with all accessories turned on, its actually the RPM cluster kill itself when voltage drops near 12v. As per experimented, driving without accessories on shown the RPM cluster works perfectly.
Ah! reminds me of my ex colleagues Citreon ZX, twin fans, twin speed. Hot time really wheeeeee sound when both fans at high speed.....
yeah..agree on this
maybe u can ask your wireman to swap fan wiring... low speed for ac control, then high speed for water temp control...
Yes, when the radiator fan kicks in, it draws Alot of current, which the alternator tries to compensate by increasing the actual mechanical load placed on he engine. Your alternator have a regulator which also affects the alternator 'load' on the engine. And it seems like there are 2 things that are happening now.
1. When your fan kicks in, it draws damn alot of current, creates a voltage drop which the alternator tries to compensate by increasing the mechanical loads placed on the engine
2. When the mechanical load from the alternator increase, your engine itself is not ready for it, the ecu does not expects a sudden increase in load and thus your idle drops as it cannot sustain the excess load from the alternator. The drop in rpm, causes the voltage to drop EVEN lower, below the threshold of what your meter requires to operate at probably.
When you are driving this is a non issue as the engine is already at a higher rpm and relatively high load from actually powering your car, but at idle, the power the engine is producing is only just enough to sustain the idle and any change in mechanical loads will affect the idle, unless the ecu is able to compensate for it, either by opening the TB more if it is an ETB or opening the idle valve more, but this requires an input to the ecu.
The ficd helps by allowing more air to go past the tb, it's like opening the throttle slightly in a way, to compensate for the increased mechanical loads placed by the alternator when the fan kicks in. Just like how it compensates when you turn on your aircond because the compressor places additik al mechanical loads on the engine. Same goes to the alternator when there is an increase of electrical loads
My car now with 2 SPAL fans sounds like a jet taking off whenever the aircond turns on or the fan turns on due to temp
The speed control of fan, can i bypass the ECU and use an after market fan controller instead? I just noticed the car's fan only got 1 speed, HIGH at all range. LOL.
I will explore on FICD part. May be that will stabilize my rev even more when in traffic. I will do the pulley or diode mod first to the alternator.
My mechanic that did the swap said i should not use SPAL fans, very problematic for this kinda swap. I would like to hear the fan sound though.
Not too sure how is the wiring for your fan. Like I said usually there is a fan speed controller controlled by the ecu which is completely variable, though I could be wrong. Or maybe it is like the evo fan where there is 3 wires to power the high and low speed mode. If it is the variable type, don't think you got any method of controlling the speed lol.
The ficd mod will be the cheapest and easiest mod to do. I would suggest you try the ficd method first or you try to press your throttle slightly, raising the rpm to 1500rpm or so then turn on the ac and adjust your throttle until it stabilizes at 1000rpm see if the issue appears and also your voltage.
Also if what I suspect is true where the voltage drop is due to the rpm dropping due to high load placed by the alternator, downsizing the pulley will apply even more load on the engine.
Stepping on the throttle is what i have been doing when the fan comes on, to keep the voltage high. The rational behind downsizing the pulley is to allow it to spin at faster rate at low RPM to generate high electricity at low rev range, i don't see how that will add more load to engine ?
Its like a bicycle with gears.
The bigger gears is easier to cycle compared to smaller gears which require more force to cycle.
The bigger gears/pulley which is easier to turn but will require more engine rev to spins faster in order to produce more juice.
The smaller gears/pulley will require lesser engine rev but more engine power to spins at the same speed as the bigger pulley/gears
If i recalled the physics correctly, its inertia?
check at the fan motor for the socket..how many wire going into the fan?
if 5 wire..its multi speed fan..
if just 2 wire then its single speed fan...
if just 2 wire, then probably u can look for fan speed controller (from computer fan speed controller maybe?)
If stepping on the throttle solves your problem, then installing an FICD should also solve your problem. Wired to activate when the fan kicks in.
In theory if you think like that yes it will spin at higher RPM if your engine can sustain the load, but like I said, the alternator is not a free spinning device with 0 resistance. There is resistance placed on the engine by the alternator which varies depending on electrical load. When the electrical load is high, like when your fan kicks in, the alternator resistance increases, causing your engine rpm to drop as the engine is not ready to compensate for the increase in load. If you reduce the pulley size, like Gunnerzz said, it's like trying to ride a bicycle with a higher gear. If the wheel is above the ground free spinning, yes you can spin the rear wheels faster at a higher gear with the same input RPM, but once you go on the road with actual load, on the higher gear you'd need to push alot harder to maintain that RPM.
Yes you got it right. It's not inertia, it's just torque multiplication and is basically the principle of how your car gearbox works as well
Siao eh, motor speed controller that can handle 50+Amps is expensive man, those computer fan speed controller also is brushless and not for brushed motors. Speed controllers for brushed and brushless motors are very different. Brushed motors are 2 wires and can be controlled with a brushless fan speed controller. Even if you can get an electronic speed controllers, what will control it? On stock cars the ECU itself controls the fan speed directly.