Alternator Shootout at Idle (136 vs 160 vs 250 amp)

I take 3 alternators, head to head at idle to show which one will perform better than the other at idle, and will also a 49mm alternator pulley on all 3 to see how much that helps to increase the voltage. I have been experiencing a lower than desirable voltage at idle ever since I installed the electric cooling fan for the radiator and the ATI super Damper with a 25% underdrive pulley.

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[chrclmnky]

This video demo is absolutely genius. Gives me the courage to swap out my crappy mini van's alt and slap a higher amperage to keep up with the car audio demands.

[TheRealMikeWilly]

One thing I learned while working in auto parts, an alternator's amperage rating is given @ 2000 rpm. So when it comes to idle speed power production, all goes out the window, 160 amp alternator A will more than likely produce something different than 160 amp alternator B. Currently running the durango 160 amp alternator in my XJ and my volt meter hardly moves down off 14v even with my sub thumpin and my stereo blasting.

[blasekaauamo]

Nice video. You could also upgrade your charging and ground wires to help with the load. I am into car audio and upgrading the charging and ground wires make a huge difference as well.

[adambatchelder]

Good comparison. Your under drive crank is really hurting the output. Keep in mind that the alternators cooling fans are also turning slower, more heat

[BigvthG]

U are a life saver
Been trying to find info on this but nobody did a video like this keep up the great work brother

[stoichiometry]

Martin: Thanks for these videos, you've saved me a lot of time in R&D on my 4.7's.

I'm glad my 49mm pulley calculations were correct. Seems the 160 has much better windings. I'll be employing your combo (AIRRAM/ATI, 49MM and 160).

Keep these coming

[kanepua]

Good info. Some things need to perform at idle, like A/C when stuck in traffic.

[pallskrewee]

Great video. As noted by another viewer, the slower rpm speed will have a dramatic effect on the alternator. Of course you proved that by installing a smaller diameter pulley. Also, the vehicles computer may also have an effect, the type of battery, & the age of the battery itself may have an effect. I had a 2015 Chevy cargo van that would cause voltage drops from the stock alternator. I called the dealership, asking if this was normal, & they said yes. I further inquired as to why, and it was explained to me that it was part of the fuel economy system. Certain times when I was going up a incline/ hill, the computer would cut off the alternator in order to reduce HP drawn on the engine, which helps with fuel economy. This would also happen with the air conditioner in the summer time. Also noted by another viewer was to perform the big three upgrade. Especially if you are installing a higher current output alternator. Your stock electrical wiring is generally rated for the current demands from the electrical system. Car manufacturers only give you what you need. Nothing more.

[JohnAdams-lgmh]

Great work Martin, I was certain the 250 amp would be more than enough to level out the voltage, Glad you posted the video. Keep’em coming!

[jthleb]

Thanks. I need to get a new alternator. Now I know to get the 160amp and the smaller pulley. Great video

[ghssanalkhwyter]

Many thanks for your simple and very good explanation and alternators tests

[ftintheflames]

You may also try this with a multimeter on the alternator post. Ive found that any digital guages plugged into the obd2 port usually display lower than what the actual voltage output of the alternator is. Id check at the alt post, battery post and the input post of the junction box. Scan tools also display lower than actual voltage. Also anytime ive done a h.o. alternator i replace the lead from the alt to battery and to the junction box with heavier guage ofc wire like 2 gauge. That always seems to improve things. 8 and 10 gauge with fusible links can only allow so much current at a time. Great vid keep em comin.

[SouthernKillafornia]

Great video and Mopar to boot. I killed my battery this past weekend running headlights, fuel pump and fans at idle waiting to get into a car show. You gave me plenty of great info.

[bitzombie]

This video addresses the questions in my mind as far as aftermarket alternators and pulley size effect at different RPM ranges. Informative video without a ton of extra gibberish.

[oscarcrespo]

This is completely new in my knowledge. Thank you Sr. You are the man Sr.

[JUKEr]

Thanks for this video. I've got a 2001 Land Rover Discovery 2 (L318) with a 4.0L Thor engine and a stock 120A alternator. A 2001 Land Rover Range Rover (P38) with a slightly bigger 4.6L Thor engine with a stock 150A alternator. 
Many Discovery 2 owners have stated that the Range Rover 150A alternator is adaptable to our Discovery 2s. 
Thanks for your experiments showing the differences. Cheers from a 'Murican in the UK!

[letitrest]

Thanks Martin. This is actually something I've been curious about, because I'm considering doing a cargo van conversion, with electrical system.

[dizzydezel]

You should do a big 3 upgrade on you charging system wiring! With a larger alternator your bottle necking the power flow of the high out alternator!

[randyrawdingii]

Interesting about the idle speed... Getting ready to put an '04 Sequoia alternator in my '06 IS250. Thanks for the great vid! God bless...

[aggeekuipo]

Great video, man. It really helped me make the right choice on my Crysler 300.