garage wants to install my alternator this way.....should i or should i not

[stingray72]

I have a 2019 nissan versa sv 1.6 liter and a 350 amp high output alternator.  My problem is that my factory serpentine belt is a 7 rib and i need a size that it does not come in.  And the shop wants to place a 6 rib on because they can find one that fits.  This seems like a risky approach.  Should i or shouldnt i?

[audiofanaticz]

Search for a belt in the correct length with more ribs, like 8, 9, 10 ribs.
Then what you do is take a sharp utility knife and you cut the additional ribs off the belt down to the correct rib size you need. People with 3-7+ alt setups have been doing this for decades without issue.

 

Usually Gates Industrial belts (green in color) will have the larger lengths and higher rib count.
Going with a narrower belt than what you need (ie; 6 ribs instead of 7) will be less surface contact on the pullies and could cause your belt to slip around the alternator pully when the alt gets loaded down.

Also that is a lot of alt for such a small motor, hopefully your idle is high enough or you may have no output from the alt when the engine idles because the alt isn't spinning fast enough, or if it does turn on it will have rather low output.

[stingray72]

its a smaller pulley so it will spin faster im told so hopefully i dont have an issue with output.  Thanks so much for your help.

[Kyblack76]

Yep, id be a little concerned about it turning on (the alt) at stop lights, and or idle. Many use a smaller pulley for lower turn on (low rpms) but then, can see issues at rev. And it is usually smaller 4 banger type rigs that have the struggle. 

 Also, use the shortest belt you can. Or, a proper slightly longer one, and find some where to add a idler pulley to keep it TIGHT. 350 amps, at full pull, is going to want a LOT of belt pulley wrap (another reason a smaller pulley isnt ideal), because that will wanna bog down at full rip. Hopefully it all works, and goes smooth. Nature of tbe beast when we got what we have and try to improve with no drop in super wonder stuff to go in. Just stay at it,.. and figure out the issues in a smart, logical way... and there isnt anything you cant make work, and work great. 

[audiofanaticz]

Almost all high output alts will have an underdrive pulley, thats where they get some of their additional power from due to it spinning faster, which that in itself can some times cause another issue in higher revving vehicles. Typically the smaller underdrive pulley will be a 3 to 1 ratio, for every 1 revolution of your engine your alt will spin 3 times. Typically an alt won't turn on until the alt pulley is spinning at 1800-2400 rpms (again this will vary a lot from vehicle to vehicle alt to alt), but if your vehicle idles at 600rpm that means the alt is only seeing about 1800rpm and may not turn on until 2000rpm.
This is rarely an issue though except when you put big monsters on small fuel friendly cars.
Also once that alt is under full load be prepared for it to rob a good 20hp from your engine!

If your car has a/c I think the stock belt length is 44.3 inches (typically the last 3-4 numbers of the belt model number is its length), so if you could find a 43.75 to 44 inch belt you should be in decent shape. Typically you want to go .5 to 1 inch shorter on belt length to accommodate for that smaller pulley which will keep your belt tensioner in the ideal position. Granted if your able to add an additional idler pulley close to the alt for a tighter belt wrap your factory length belt maybe just fine to use still.

Its a pain in the ass but a easy method for finding ideal belt length is to use a piece of string and wrap it around all the pulleys as if it was your belt, and then with a second pair of hands have someone hold the belt tensioner in its normal position (how it rests with the factory belt) and when they are holding it there mark the string with a marker where the 2 pieces come together and then measure the length of the string. That is your needed belt length with no guessing. Kind of hard to explain it, but its simple to do.

[stingray72]

I think after taking all this in im going to not put the ho alternator in and not mess with the voltage control either and just keep this install sq with my phoenix gold 400.1 (my current amplifier) on one of my stereo integrity sql 12's.  Now on top of the ho alternator i also have 40 ah of lithium battery that will be sitting around.

[audiofanaticz]

If it was me I would still go ahead and put it in, after all you already bought it so you might as well use it, it its typically easy to install.

All the potential issues are rather simple to get around and come up with solutions for fairly easily and cheap to do if any of them do arise.