rigtec
New member
Hi A team,
Just the other day, one of our community members had a question and it was an EXCELLENT ONE! He was trying to determine if one of his new accessories was defective or if his new 4Runner was having trouble supplying enough voltage/amperage to feed it properly. Well, as far as I know the jury is still out on that conclusion. But my position is that sometimes the problem isn't that our 130A Denso (small case) hairpin alternator isn't capable of supplying enough current to your accessories. Sometimes the trouble exists because our alternators are not able to supply enough current... 'at curbside idle!
"Well rigtec, what are we supposed to do... go out and spend $800 bucks and buy a Huge output alternator like you did; money don't grow on trees you know..." lol! No, not at all tech-team! What you can do about not having enough current to run certain accessories when idling is simply change the alternator's idle speed by manipulating the Crankshaft to alternator pulley ratio. Here's how that works: Your 5'th gen 4Runner employs a 6 inch crankshaft pulley (w/6 or 7 grooves) which turns everything from your water pump to your power steering pump...etc! Now your alt pulley IIRC is about three inches +/- .5 inches.
That gives a 2 to 1 alt ratio e.g., so if your engine/crankshaft turns at say: 800 RPM, then your alternator pulley is turning at 1600 RPM; which gives a 2 to 1 ratio. But that can be changed within a nominally margined upgrade. If you install a 2 inch +/- alt pulley and the crank spins at 800 RPM then the alt pulley will turn at 2400 RPM at idle; which yields a 3 to 1 spin ratio. It's not a matter of needing more alternator output; 130A may be plenty for your basic needs. It's just a matter of when you need to use it, which in this case, you need to be there while at idle, like for sitting still with the engine running and watching the tv or trying to chill a six-pack!
The only caution I guess would be a marginal amount of extra wear and tear when revving the engine at high rpms, like when doing 65-70 mph, the rpm may be up to 4,000 rpm; which means the alt will turn at 12,000 rpm, so the bearings and brushes life span will suffer, but like they say: "There's no free lunch"! Here are a few articles that I pulled from my library for your reference; they're very good reading info; especially in the bathroom!:
Here's another article to hold on to just FYI!
Listen folks, I realize that I put a lot of information here, but I tend to post threads here that no one else has posted about with any intensive, peripheral, theoretical detail and my threads address issues that are highly relevant to your subjects of concern on these forums! I never intended for you to read all of this stuff at one time (lol), just print the ones you are interested in and put them aside for another time. I say it's relevant because this is a truck modification advisory forum and does involve about 55-60% of electrical T/S that we provide here, so I just want you to be somewhat informed about the mods that you're interested in 'BEFORE' your desperate cry for help, hahaha!
Oh... Here's a documented video of an alternator that's dishing out 75% of it's full load capacity; it really doesn't matter how many amperes that it's capable of, but it's pulley size/ratio is determining it's curbside idle percentage output... your's will do the same thing (just not the same amount of current) wrt it's ratio! Hope you enjoy the read An alternator putting out 75% of it's full load at idle
rig
Just the other day, one of our community members had a question and it was an EXCELLENT ONE! He was trying to determine if one of his new accessories was defective or if his new 4Runner was having trouble supplying enough voltage/amperage to feed it properly. Well, as far as I know the jury is still out on that conclusion. But my position is that sometimes the problem isn't that our 130A Denso (small case) hairpin alternator isn't capable of supplying enough current to your accessories. Sometimes the trouble exists because our alternators are not able to supply enough current... 'at curbside idle!
"Well rigtec, what are we supposed to do... go out and spend $800 bucks and buy a Huge output alternator like you did; money don't grow on trees you know..." lol! No, not at all tech-team! What you can do about not having enough current to run certain accessories when idling is simply change the alternator's idle speed by manipulating the Crankshaft to alternator pulley ratio. Here's how that works: Your 5'th gen 4Runner employs a 6 inch crankshaft pulley (w/6 or 7 grooves) which turns everything from your water pump to your power steering pump...etc! Now your alt pulley IIRC is about three inches +/- .5 inches.
That gives a 2 to 1 alt ratio e.g., so if your engine/crankshaft turns at say: 800 RPM, then your alternator pulley is turning at 1600 RPM; which gives a 2 to 1 ratio. But that can be changed within a nominally margined upgrade. If you install a 2 inch +/- alt pulley and the crank spins at 800 RPM then the alt pulley will turn at 2400 RPM at idle; which yields a 3 to 1 spin ratio. It's not a matter of needing more alternator output; 130A may be plenty for your basic needs. It's just a matter of when you need to use it, which in this case, you need to be there while at idle, like for sitting still with the engine running and watching the tv or trying to chill a six-pack!
The only caution I guess would be a marginal amount of extra wear and tear when revving the engine at high rpms, like when doing 65-70 mph, the rpm may be up to 4,000 rpm; which means the alt will turn at 12,000 rpm, so the bearings and brushes life span will suffer, but like they say: "There's no free lunch"! Here are a few articles that I pulled from my library for your reference; they're very good reading info; especially in the bathroom!:
Here's another article to hold on to just FYI!
Listen folks, I realize that I put a lot of information here, but I tend to post threads here that no one else has posted about with any intensive, peripheral, theoretical detail and my threads address issues that are highly relevant to your subjects of concern on these forums! I never intended for you to read all of this stuff at one time (lol), just print the ones you are interested in and put them aside for another time. I say it's relevant because this is a truck modification advisory forum and does involve about 55-60% of electrical T/S that we provide here, so I just want you to be somewhat informed about the mods that you're interested in 'BEFORE' your desperate cry for help, hahaha!
Oh... Here's a documented video of an alternator that's dishing out 75% of it's full load capacity; it really doesn't matter how many amperes that it's capable of, but it's pulley size/ratio is determining it's curbside idle percentage output... your's will do the same thing (just not the same amount of current) wrt it's ratio! Hope you enjoy the read An alternator putting out 75% of it's full load at idle
rig
Last edited:
op2: Best to you!
