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.

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.

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

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.

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

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

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.

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

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

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!

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.

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

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!

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

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

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.

Glad I ran into this video. Had the same issue when upgrading to a higher amp alternator. The idle performance was just horrible. With a full load it started to dip in the 10s with voltage. Accessories would sound slower and the all the lights on dash would flicker a bit if already illuminated (but was fine higher RPM). This was after I have done my big 3 upgrade. Luckily I still had my previous alternator and decided to slap that back in. 14 Volts across the board sometimes hitting 13. Returned the High amp alt and got my funds back. Not sure what my current alternator puts out as I had a shop replace my older one but just wanted a bit more amp headroom for the equipment I am running.

Thank you for that, I’ve been upgrading these on different vehicles for years and never knew a 160 would ever outperform a 250 all things being equal (idle rpm). Never do the builders mention any of that useful info.

Thanks for the video I was just thinking about changing my alternator

Hey Martin thanks for your help earlier. I fixed my AC in an old jeep I bought. 2002 Overland. The compressor works fine! Just needed 134 a. Did the dye no leaks. Might be a small one at schrader valve. That all I saw. I was trying to find the low pressure sensor to jump it over but after recharge it works fine. Hubs and brakes r next! I will catch some more of your videos for that. Boy you r such a huge help. I have air tools too. Glad you are here!!

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

I swear I am not some shill for the company, but you have to check out Mechman alternators. I have a 6.0 Powestroke (with fully upgraded wiring for + and -) truck that absolutely eats alternators due to the plowing and really low idle / 3.5k maximum RPMs. Those things actually deliver real idle output and they even come rated and pretested at Idle and running speeds. I've installed them on every truck I own barring one junker van. Your video absolutely made me feel better about spending $500 on a 320 amp alt from them. Plus no need to run a smaller pully unless you wanted to.

video very helpful. I now realize i fried my alternator driving city speeds with all accesories on plus a 1500w amp.

what you need my good sir is a big v3/v4 kit its a bigger AWG depending on what accessories you have like for an example i have aftermarket accessories like 2 mini light bars 2 600w amps 1200w alpine subs wheel well multi color led lights upgraded msd coil pack for wider spark plug gaps (.035) the vehicle manufacturers are the cheapest bastards and with that being said they run thin gauge wires from your alternator to battery and even battery ground as well as engine ground so simple solution is before you replace your alternator buy a big v3 kit for YOUR TYPE of vehicle install the kit DONT replace factory wire just put your new kit wire typically 0-4 AWG over your existing factory wire this will save you time and money by not having to buy another alternator because more then likely the factory AWG isnt letting the alternator produce the electric capacity its really capable of 🤟🏼🤟🏼👌

I saw elsewhere on YT that high amp (aftermarket) alternators get their amperage from rewiring the windings in the stator from series to parallel (or vice versa). High rpm performance is improved at the cost of low rpm performance.

Oh Brother...thank you so much for this video! You just saved me a lot of money. I'm not a mechanic in the least, but I find myself in the market for a new alternator, knowing absolutely zilch about them. The video I watched here on youtube just before watching yours told me outright to buy the biggest alternator I can afford and not to worry about it, that it has no ill affect on my vehicle whatsoever. And, that way I would be prepared for any added electrical add ons in the future. I was shocked to see these results of your. It was like watching Goldilocks' Garage....not too cold, not too hot, but just right! Liked and subscribed...

Great video. I just put a chrysler 320 Amp 200 at idle JS Alternator on my 2.4L 2016 Jeep Renegade Trailhawk. I had a 160A stock but now my MPG has gone up from 32highway to 38 to 41 and my voltage is 14.3 at my cigar outlet with AC on max and fan running.

Huh, that's interesting. I thought for sure the 250 would have given you the best results. Great vid as always 👍

Nice video Martin. This is Scott’s brother from Louisiana. I hear all kinds of martinbuilt stories. 👍👍

Good information! I wouldn't have thought the 160 would out preform the 250

I had the same problems with my blend doors !!! Changed everything out and still had the same issues !! I thought I knew what that sound was... Had to laugh when you confirmed it. 😂🤣

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!

tech tip I have learnt it's not just voltage you look at but also amperage as well

Alot of things need to be considered here. The 160a with small puller may keep higher voltage under load but the 250a will supply more amperage under load(depending what rpm that 250a is specified). If you're wanting more voltage depending if your alt is internally regulated then a couple diodes will fix that(15v+) or if you're externally regulated then you may have to look at an external regulator with the 250a alt.

Very scientifically done. Great job and very helpful information. Thank you for the work you put into your videos.

I just rebuilt my 100 amp OEM Toyota hairpin, with better OEM parts from a Dodge Durango to better cope with the 800+ amp draw it receives in my car. Larger 12 - 50 amp diode rectifier plate vs 6- 35 amp, 1.8 ohm rotor, and re- configured the stator to do 240 Amps. It is an improvement from the 2.2 ohm rotor, and 6 diode plates factory. Still not happy with idle output, I bought another new denso 160a stator, tore it down again(solder joints @ the rectifier plates were a bitch) and after the new stock stator, I have a very stable 155+ amps at cold dead idle with a small pulley. Actually pretty good for a small case. I'll upload a video later this next week, I have a genuine denso regulator that has a higher base voltage setpoint(14.5 vs 13.6v) with temperature compensation on the way. When that's installed, I'll make a video of it clamped at full temp. I plan on a large case DC power unit(XP270 - 220a hot idle 270+ at speed. It'll take a while to get here. For now, and playing with this small case, learning about the difference in parts, and how easy it is to make an OEM home built - high output alternator yourself, its actually incredibly easy. I even devised a way to have variable voltage control on the fly from inside with a variable 6k ohm resistor. I really should make a tutorial on the next build. It's fun doing it yourself, I even painted the case when it was apart, even looks like a professional aftermarket unit. I'll get something real good posted here soon. No reason why others can't build a very high quality unit of their own as well. Thanks for posting, it confirms my exact experience, and upon research and finding this video, I know after all the work again tearing it apart, it was ultimately the right choice for down low power. You da man!

Lower voltage means more amps, that's why alt was so hot. putting out amps to get back to voltage set point

I guess I think 4 things (great video BTW): your belt drive system is underdrive to start, none of the alternators perform well at 600RPM (luckily I don't drive at 600 RPM), and the 136 AMP was working hard under any circumstance, and I agree, the 160amp was best balance between $ and performance, although I am curious about reliability and life.

From my understanding, alternator output is stated at 3600rpm. Idle will be dramatically lower hence the need for a battery. A battery is your fuel tank. Your alternator will replenish your battery while driving and do what it can at idle. A 160 alternator will output only 65-70 amps at idle with the stock pulley. Electric cooling fans can pull 30-40 amps alone. Really need that battery capacity to be available as much as an alternator ready to replenish it.

Great video Martin! I’d love to see a repair video on the blend doors, or one on how to repair the heated seats🤙🏼

Thanks Martin that was very interesting as are all your videos I don't own a jeep but applicable to others. Keep up the good work and Hi from Australia.

Thanks for fine detail explanation & chill attitude. I had watched twice your post

I think that underdrive pulley really hurts your charging from your alternators wonder if the 250 amp would do allot better with correct speed compared to the 160amp

Lots of efforts in this video

Wow that was really cool bro. Hell that's a lot of time for us.

Awesome demo and general info on those alternator tests. Thanks 😊

Excellent comparison, Ive got an older Chevy with a 5.7, my alt output with my a/c and electric fan on it pulls it down to 11.9 volts. Now I just gotta find at minimum a 130 amp alt, ive found a 200 amp, but have always thought that was to much anyways,

Thanks for the video. According a few wj owners the pcm quits regulating the voltage at some point...some of them even junked their wj's for not knowing what to do...but the few that kept the wj just installed a voltage regulator fixed at 14.3...but it has an adjustment screw on the back to increase or decrease...i bougth one from alternatormen...end of problem..cheers!

Voltage is not what you want to be checking as long as your in an acceptable charging range. You need to have an amp meter to see the real winner.

thanks uncle..so that means im going to small pulley to my 120a upgradble altenator..done subcribed

Doing the Lord's work.

Check the idle solnoid activity, check battery cells, clean all ground n earth sockets n contactors upgrade all grounds to higher gage wire , finally check or replace voltage regulator n the belt

Ya, my ZJ has electric fan, stereo and the stock alternator can't handle it when I have accessories on. Thanks for the video. I'll think about a 160 and a 49mm for sure

The YT gods threw me your video. I like a lot of it. I think you could really improve your value to viewers if you summarized all your hard work and data collection into a summary spread sheet (similar to YT'r Project Farm).

I Noticed that as You put items on, your RPM also kicked Down!!

Where was the AMPERAGE reading? Did I miss the critical unit of measurement ( as in the video title)?

FYI 13.5v is normal float voltage for a fully charged lead battery. Charging voltage is generally 14.4-14.8v. There's frequently a voltage drop in all that electrical equipment. Check it at the battery or alternator. I can almost guarantee it's a higher voltage. Normally minimal driving is at idle...while it's interesting useful info...it's not a very realistic factor for most.

Great video! It would be useful to make a table at the end with comparing avg. results for all 3 alternators on different loads :) Style Project Farm Thanks!

I use your videos for my 99 Jeep GC Limited 4x4. These are great!

Some alternators dont seems to charge untill a certain rpm. Say 1200 rpm, glad you tried the smaller pulley

The voltage depends on few factors not just pulley size and alternator size. The alternator amperage, the battery size, the battery quality class, and the load, the resistance of the circuit. These 3-5 factors. I remember that for a 3.2-4.3 liter mercedes ML, 1998, a battery size of 100amp hours or 725CCA and an alternator sized 115 AMP, was factory reccomended back then. Of course now the alternator sizes put by manufacturers are greater. Say a 540CCA stock battery in GM cars with 1.6 liter engines is matched with a 100 to 120 AMP or 150 AMP alternators with the option for the buyer to put a max size of 680CCA battery. Also the outside temperature affects the batteries ability to hold energy, whcih is less during winter and better during summer. Thus a battery might need a warming cover. With an AC fan running at max speed-3rd or 4th speed in GM cars, during hot summer the battery voltage in european Opel Zafira 1.6 can go down to 12.7 volts with stock alternator of 120AMPS and 680 CCA battery.

I have been working for long time on alternator the hair pins has double stator plus very small pulley you can have good results

Great vid, just what I needed to know...

great video man thank you for the feed back. i am a subscriber now

Awesome video, Thanks for the shoot out!

Thank you so much for making this video so informative

id say the 160 with the 49mm pully outperformed the 250apm alternator, regardless of how they built the 250amp alt i think they shoulda made it to hold 13 v at all engine rpms, i was shocked it didnt even perform good with a 49mm at idle. i mean lets say im trying to show off my big sub to a friend, im not gonna rev my engine to 4000rpm for that 250 amp alt to work, just doesnt make sense, i hope the manufacturer change their way of thinking and make their alt put out 13-14v and 250amp around 700rpm, that would be perfect

Great video… I accidentally came across your channel and I have subscribed… Good stuff…Very informative

Thanks for all of your videos! I am soon to do the heads on my 02 dodge ram 1500 with a 4.7. I was just wondering the other day if I could upgrade the stock 136 amp alternator to a 160 amp with no problems. I think this answers my question. The reason for the upgrade would be because I have a warn M-8000 winch & it bogs down real bad when I use it. I have been binge-watching your videos so I can learn more about what is in store for me ahead. Hey, thanks a lot for the wealth of knowledge, you have made this back yard mechanic a lot more confidant. Just subbed.

Very interesting, thanks for the education Martin !

Man I wish you lived in South Florida. Gotta change out one of my lifters, got a slight tick going on. Just changed the valve covers last weekend.

No vid.i like the approach not much not to lil...and great knowledge. Well laid out video...nice and smooth!!! Keep it up!!!

But amperage output at idle is actually the best test when just looking at the alternator. Volts is a SYSTEM test which includes battery, battery state of charge, battery age, battery reserve capacity (rated in amp hours) and integrity of vehicle grounds and positive circuit. In other words, if you had 2fully charged heavy duty lead acid batteries, the results would be totally different in volts. The results are accurate, but only for YOUR vehicle at that point in time. Solving all vehicle voltage problems with the alternator is like getting the buggy ahead of the horse.

Yup Even Diesels need great performance at idle.

4:13 Nice Fart Martin, oh yes the “blend” doors I will start using that one as well

You can start by upgrading all your battery cables to 1/0 OFC will allow you to pull a little more amperage out of your stock alternator. If it still can't maintain 13 volts then I would give mechman a call and have them build you one that will easily handle what you're looking to do.

Their denso alternators are excellent, mine went 260,000 miles no problems. 160 amp.

Thanks. I have both a 130 amp and a 200 amp alternator for my Ford.....and neither put out enough at idle....in drive at a stoplight, to maintain the battery with 'winter' stuff on, like heater blower, headlights and defogger..... Will try the smaller pully.

Saved me from swapping a 220 on my 03 5.9 cummins, came stock with a 136, I'll swap the 6.7s 180.

Very useful testing.

the same spec can be found in an alternative alternator if you can find the model you want from mechman guys "its a VELEO 11358" unit that comes stock in bmw e70 e.t.c or the bigger unit that comes in the M50d the small unit does 230amp idle and 370 at rev haven't tested the big unit's peak new equipment need to be built for that seems like over 400 amps (make my load catch fire) these unit are used in other German cars to with all different types of mounts keep in mind the oem BMW version uses LIN bus for control (BMW x5 alternators are cheap & everywhere !) not E53 versions ! must be newer e70 & onwards

I replaced my the one in my 04 when it went bad with one from a Durango, I believe it is a 160.

Definitely add some 4 AWG wire from the battery to the generator, from the batt. to the starter and a couple of grounds from batt. to chassis and batt. to the generator's body ensuring they both go through the factory hall shunt.

Excellent research my friend !!

'Blend Doors' ..... gotta remember that one

Your Factory Alternator is fine you should upgrade your battery size That is your energy source. If you replacing your alternator with Bigger alternator You need to upgrade your wiring size to. Alternator is designed to deliver more energy on high rpm. Any time when you add high-power output device like stereo with hi output or fan, heater, lightings,… on your car you should considering installed the second battery, Maybe lithium battery with combiner battery, never charge lithium battery directly with alternator. Voltage sagging is usually because you wire is to small, batteries don’t have enough energy or both.

This was just the video I needed to determine if my alternator was right for my van conversion. Thanks for that... I had a 30 amp bc/dc charger to charge my 220 amp lithium house batteries, I recently upgraded by connection in parallel an additional 40 amp bc/dc charger (both RedArc). Before turning on the chargers the at idle output was 13.8 v. With just the 30 amp bc/dc on the volts when to 13.6. With both chargers on volts when to 13.4 & is charging at 72.4 amps. I am assuming the alternator is sized appropriately? Right???

I bypassed the pcm voltage regulator with one from a early 80's dodge. It is adjustable voltage on the back, I set mine to 14.5 and it only dipped a couple of tenths here and there. You have to put a resistor on the pcm wire to fool the pcm so you won't get a code p044. I also have the 136 amp alt. Just an idea.

I want to upgrade because I need to the car is under-engineered and only one acessory hurts engine preformance at idle. It seems like you are indicating that the voltage is more critical than the amps when you have enough amps as in the situation of(?) 160 amps and 250 amps. Are you concerned about the voltage with regard to the ignition system because the accesories are running and the voltage holds at or over battery voltage with the accesories on. Or, does this start that suggested process of too much draw on the system, the battery kicks in to give out power, but then a low voltage never allows the battery to get fully recharged and creates a draw for power perhaps greater if the plate material starts to degrade. Or will some components not function at 12v or less especially considering that was at idle.

Great video, thanks for making it

very well done test thanks

The temperature of the alternators should have been measured at idle. Running high amps at idle has burned up a lot of alternators or caused vehicle fires. Victron charging systems has a video on their channel showing the excessive heat at idle on the alternators at idle.

Do different vehicles have different voltages every car I checked was at or around 14.7 while running.and if your going with bigger alternator do the big 3 upgrade

I also have done car audio for years! Your voltage was to low to begin with. ( that's why driving it around for a couple days brought it up to the 14 range. Watching video i can tell you. First you battery was week, second your connections where needing cleaned, lastly you should clean the big 3 connections as well as add the 0 gage wires for a complete big 3 upgrade ( cheaper than the alternator) and if you where still worried about it your battery needed replaced anyway get the yellow top light gray optima battery ( charge and discharge at faster rates ). The battery included might put you up to or more than the alternator depending on time of doing it. Fyi as i have said for years now doing car audio if you're dealing with voltage problems with out a system in it you need to redo the electrical. All of it. A good electrical system wouldn't drop voltage accept turn on on!!!!! Meaning at first power on it will drop but the regulator kicks in and brings it up to a steady voltage. Very last thing. I personally consider any alternator that is running at idle below 14 volts with nothing else on to low and a problem in the system. ( factory or not you should be at 14 give or take no more than. 2 )

Мужик молодец, полезный контент пишет!

The thing is that the current is high but the voltage is too too low because they use thicker wire in the 200+ amps so that reduces the amount of turn on the stator winding

Great video. Thanks for sharing.

Also, is there a link for the 49mm pulley? Or any details on groves, bore size etc?

great video

Greatly Informative and Soo Helpful! Thank You!🇺🇸👍