blakep82
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| posted on 5/4/09 at 03:12 PM |
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what current alternator can i get away with?
I'm after a tiny tiny alternator for my x20xev engine.
since our cars have very few electric items, could i get away a 30amp alternator?
the original one off my engine is 70amp. but since i don't have wipers, washers, heater, ECU computers, radios etc, i'm thinking i could
use one much smaller. the only electrics i've got is the lights, rad fan and megajolt.
i need one with a very short body, preferably a straight swap the original bosch one i've already got. pulley should be a multi V belt (5
grooves i think)
any ideas?
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C10CoryM
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| posted on 5/4/09 at 03:24 PM |
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It will probably run off a 30A alternator, but any time your fans come on it will be maxed out and drawing from the battery.
Most fans are 50A or more which means you will need a larger battery than if you had an alternator that can support the load.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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blakep82
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| posted on 5/4/09 at 03:30 PM |
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50A for the fan? 
never knew it was as much as that.
how often do electric fans come on during normal running? ie not stuck in traffic etc.
or what if i had a bigger radiator so the fan wouldn't be on as much? blank bits off it cools too much
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clairetoo
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| posted on 5/4/09 at 03:44 PM |
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I'm using one of those small fork truck alternator's off ebay - I think it's about 35 amp - and I've had no problems at all
(although it does pull the rev's down a little running the fan at tickover )
Its cuz I is blond , innit
Claire xx
Will weld for food......
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blakep82
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| posted on 5/4/09 at 03:51 PM |
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ooh what one? have you got any measurments?
how much was it?
or how about motorbike ones?would any of them be suitable?
[Edited on 5/4/09 by blakep82]
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C10CoryM
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| posted on 5/4/09 at 04:03 PM |
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In theory the fans should never come on as long as the vehicle is moving. It's only for when the vehicle has no air flow through the
radiator.
Most production cars have low and high speed fans. Low speed requires less current, and is less noticable to the driver.
You probably can run the 30A alternator just fine (depending on what headlamps you have). It just means that when the fan comes on (usually for 10-40
seconds if your cooling system is good) the alternator will be putting out max current and the extra current required will be drawing out of the
battery. ONce the fans turn off, your alternator will continue to re-charge the battery. Not the best design as it's hard on the alternator to
work it nuts off, but it will work.
30A is pretty minimal though.
You have 2 headlamps (10A), then at least 8 other marker/brake bulbs at about 1A each. So 18A or more in lights alone.
Add ignition, guages, ECU, fuel pump and last but not least....... recharging the battery. 30A starts to look like race usage only.
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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blakep82
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| posted on 5/4/09 at 04:09 PM |
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thanks for the info cory, all worth bearing in mind when choosing. the car will rarely be used at nite i guess, maybe sometimes, but not often.
30A will def be considered the absolute minimum, i'll go bigger if i can find a good one. 40A perhaps?
not much traffic round here thankfully, so fans will do minimal work i think
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clairetoo
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| posted on 5/4/09 at 04:14 PM |
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It's
this one here - about 110mm diameter , I just made a multi-v pully to suit 
Its cuz I is blond , innit
Claire xx
Will weld for food......
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blakep82
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| posted on 5/4/09 at 04:35 PM |
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how deep is the body? like from the front of the pully to the back of the alternator?
110mm is tiny! sounds perfect. how likely is it my pulley on the bosch one will fit?
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clairetoo
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| posted on 5/4/09 at 04:39 PM |
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From front to back (not including the pully) it's 125mm . I think the shaft is 16mm - but if you are stuck for a pully , I can soon knock you
one up 
Its cuz I is blond , innit
Claire xx
Will weld for food......
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craig1410
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| posted on 5/4/09 at 04:55 PM |
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Hi,
I would have thought a 45A alternator would be sufficient.
Regarding the cooling fans, mine is from a VW Golf and runs from a 15A fuse so it certainly doesn't pull 50A!! I think I measured it at around
8A which might be 10A with the extra voltage produced when the engine is running. Lights are about 12A and my coil pulls about 5A.
As long as you keep your battery charged up and don't very often go out at night and don't have stuff like heater fans and wipers then 45A
is plenty and 30A might even be enough. If your battery is charged before you leave then you only need enough reserve alternator capacity to recover
the battery from the energy used by the starter at startup. For a 5 second start at 300A this would take 150 seconds to recover at 10A charge rate
according to my calcs. I would hope 5 seconds is more than enough to start most engines.
Hope this helps,
Craig.
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t16turbotone
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| posted on 5/4/09 at 05:12 PM |
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^ yes your right.....cooling fans do not draw 50A!!! ....50A cable would be 10mm! 15A is more than enough to allow for cooling...try the diahatsu
alternator
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BenB
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| posted on 5/4/09 at 05:14 PM |
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If fans draw 50A my alternator is screwed because my alternator only gives out 28A.... Strange the 15A fuse to my fan never goes pop.......
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C10CoryM
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| posted on 5/4/09 at 05:27 PM |
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Sorry, I'm used to large engines with small radiators that require larger cooling fans (often dual fans). Looking online at some of the
aftermarket ones it looks like you can get single fans that run at >20A which should cool most locost engines.
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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mediabloke
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| posted on 5/4/09 at 09:39 PM |
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quote:
Originally posted by blakep82
I'm after a tiny tiny alternator for my x20xev engine.
Guess your alternator is interfering with the steering column too? I was looking at the Daihatsu one on SBD's site but didn't fancy
paying £200 for it with the bracket...
You mounting it on the carb or exhaust side?
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blakep82
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| posted on 6/4/09 at 12:49 AM |
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quote:
Originally posted by mediabloke
quote:
Originally posted by blakep82
I'm after a tiny tiny alternator for my x20xev engine.
Guess your alternator is interfering with the steering column too? I was looking at the Daihatsu one on SBD's site but didn't fancy
paying £200 for it with the bracket...
You mounting it on the carb or exhaust side?
yep. only just though. the alloy bracket is really thick though, i think i'll have a go at grinding a big chunk off it. its about an inch thick
where it bolts to the block, which is where the collumn is, so reckon i'll get away with it
alternator's going standard carb side. but the carbs interfere with it too...
thanks guys (and gal ) i'll perhaps have a look at dihatsu first since i'm more likely to find one in a scrappy than i am a mitsubishi
fork lift.
________________________
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mediabloke
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| posted on 6/4/09 at 11:59 AM |
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quote:
Originally posted by blakep82
yep. only just though. the alloy bracket is really thick though, i think i'll have a go at grinding a big chunk off it. its about an inch thick
where it bolts to the block, which is where the collumn is, so reckon i'll get away with it
Keep an eye on the welds if you have to cut & shut the bracket. The welds split on mine, right underneath the boss through which the bottom mount
bolts. 
I'm thinking of using some 25mm box section that I've got lying around for mine... 
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