Car Alternator or Battery Issue

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I am using BMW fan from M43B19, its supposed to be high speed fan. The voltage dropped to 12.7 when the fan is spinning very fast for few seconds, and voltage recover back to 13.3 - 13.4 v after it slow down.

Thanks,
Ken

i see... from the way you describe it...


my suspect would be the alternator amperage not enough for your bimmer electrical...changing into bigger amperage alternator would help in solving this issue...
 

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Izso

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the voltage should be sufficient... but the amperage problably fell below than what the car body electrical demands... (load too much supply too little)
I'm still debating whether that tiny little booster wire is going to help you. Looking at the thing itself, it looks like it'll probably have some diode to upscale the V, but this will reduce the amperage I suspect and something else is going to suffer
 

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I'm still debating whether that tiny little booster wire is going to help you. Looking at the thing itself, it looks like it'll probably have some diode to upscale the V, but this will reduce the amperage I suspect and something else is going to suffer

i'm more afraid that when this device increase the voltage during load,

it will over-volt the system when the load is taken off from the system (like when fan turns off and ac turns off)

unless if the system auto compensate when the load if lower and keep true to 14v limit
 

gunnerzz

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i see... from the way you describe it...


my suspect would be the alternator amperage not enough for your bimmer electrical...changing into bigger amperage alternator would help in solving this issue...
I just finished reading an experiment paper by Utem student on car alternator.

Lots of interesting info abt alternator such as;
-normally alternator rating is the output it produce when its (the alternator) spinning at 6k rpm. With 1:2 ratio, thats 3k rpm engine speed.
-alternator will produce >12v to overcome the battery internal resistance in order to be able to charge it.

Apart from the basic higher speed will produce more current i also learnt one interesting thing;

In the paper they mentioned about crankshaft-alternator speed ratio. Normal car is 1:2 which means 1k rpm on crank is 2k rpm on alternator. This means to make the alternator produce more output during engine idle we can play with this ratio by changing the pulley size so it spins faster right?
 

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Apart from the basic higher speed will produce more current i also learnt one interesting thing;

In the paper they mentioned about crankshaft-alternator speed ratio. Normal car is 1:2 which means 1k rpm on crank is 2k rpm on alternator. This means to make the alternator produce more output during engine idle we can play with this ratio by changing the pulley size so it spins faster right?

they got it wrong.. (although i'm from utem myself :rofl: )

car alternator doesnt operate on 2:1 pulley ratio...its more than that.. probably atleast 3:1 or 4:1 (see the alternator pulley size vs crank pulley size to get the idea)

2:1 is crankshaft to camshaft ratio....



yes u can change the alternator pulley into smaller one (or bigger crankpulley) to increase the rpm ratio between those 2...

problem is on the market, most is people selling under-drive pulley (which lower the ratio and effective rpm of alternator) for race purpose and use it on the street (wrong concept)....

the reason of under-drive pulley invented for racing purpose, race engine never saw rpm lower than 4.5k rpm...it will spend most of the time at high rpm range..so to reduce alternator speed damage (as well as power steering pump)...race car build install the under-drive pulley....

installing under-drive pulley will make alternator (and power steering pump and ac compressor) working under its designated speed make it worst in slow moving traffic or on idle during traffic jam...

what people on the street is over-drive pulley...

in this jz bimmer case, is ideal solution (if not changing bigger amperage alternator)....but since sourcing the over-drive pulley which definately need to be custom made is freakin expensive, then bigger alternator is the simplest route to follow... because bigger alternator is more common mod especially in car audio shop...
 

gunnerzz

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they got it wrong.. (although i'm from utem myself :rofl: )

car alternator doesnt operate on 2:1 pulley ratio...its more than that.. probably atleast 3:1 or 4:1 (see the alternator pulley size vs crank pulley size to get the idea)

2:1 is crankshaft to camshaft ratio....



yes u can change the alternator pulley into smaller one (or bigger crankpulley) to increase the rpm ratio between those 2...

problem is on the market, most is people selling under-drive pulley (which lower the ratio and effective rpm of alternator) for race purpose and use it on the street (wrong concept)....

the reason of under-drive pulley invented for racing purpose, race engine never saw rpm lower than 4.5k rpm...it will spend most of the time at high rpm range..so to reduce alternator speed damage (as well as power steering pump)...race car build install the under-drive pulley....

installing under-drive pulley will make alternator (and power steering pump and ac compressor) working under its designated speed make it worst in slow moving traffic or on idle during traffic jam...

what people on the street is over-drive pulley...

in this jz bimmer case, is ideal solution (if not changing bigger amperage alternator)....but since sourcing the over-drive pulley which definately need to be custom made is freakin expensive, then bigger alternator is the simplest route to follow... because bigger alternator is more common mod especially in car audio shop...
Good additional info...
 

parakey

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in this jz bimmer case, is ideal solution (if not changing bigger amperage alternator)....but since sourcing the over-drive pulley which definately need to be custom made is freakin expensive, then bigger alternator is the simplest route to follow... because bigger alternator is more common mod especially in car audio shop...
You may change to a smaller alternator pulley to increase the rpm but wont that place a larger idle load on the engine? He's already complaining it's not idling well
 

Mitevo7

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they got it wrong.. (although i'm from utem myself :rofl: )

car alternator doesnt operate on 2:1 pulley ratio...its more than that.. probably atleast 3:1 or 4:1 (see the alternator pulley size vs crank pulley size to get the idea)

2:1 is crankshaft to camshaft ratio....



yes u can change the alternator pulley into smaller one (or bigger crankpulley) to increase the rpm ratio between those 2...

problem is on the market, most is people selling under-drive pulley (which lower the ratio and effective rpm of alternator) for race purpose and use it on the street (wrong concept)....

the reason of under-drive pulley invented for racing purpose, race engine never saw rpm lower than 4.5k rpm...it will spend most of the time at high rpm range..so to reduce alternator speed damage (as well as power steering pump)...race car build install the under-drive pulley....

installing under-drive pulley will make alternator (and power steering pump and ac compressor) working under its designated speed make it worst in slow moving traffic or on idle during traffic jam...

what people on the street is over-drive pulley...

in this jz bimmer case, is ideal solution (if not changing bigger amperage alternator)....but since sourcing the over-drive pulley which definately need to be custom made is freakin expensive, then bigger alternator is the simplest route to follow... because bigger alternator is more common mod especially in car audio shop...
I would agree to changing higher amp alternator, the stock 1jz alternator possibly isn't big enough to supply to all those gizmos in the beemer.

I am thinking of 2JZ alternator instead as it is still affordable. What's your opinion?

Thanks,
Ken
 

Mitevo7

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You may change to a smaller alternator pulley to increase the rpm but wont that place a larger idle load on the engine? He's already complaining it's not idling well
I am very aganist under drive pulleys, drove one car with under drive pulleys before and it felt like shite.

Thanks,
Ken
 

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You may change to a smaller alternator pulley to increase the rpm but wont that place a larger idle load on the engine? He's already complaining it's not idling well
with properly charging system set, idle can be tuned further to smoothen it out...
 

vr2turbo

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I'm still debating whether that tiny little booster wire is going to help you. Looking at the thing itself, it looks like it'll probably have some diode to upscale the V, but this will reduce the amperage I suspect and something else is going to suffer
That booster thing, seems it cheats the alternator to pump extra 0.6v only as in "This product simply tricks the alternator into putting out an additional .6 volts."
 

gunnerzz

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I am more afraid it over runs the alternator at high speed.......lol
in theory it should not be an issue as the output graph is just like engine hp graph.its output will becomes flat at its peak rpm and above.

minor concern is on the mechanical aspect which are the bearing lifespan, carbon lifespan as its spinning higher that usual.
 

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