Alternator Question

[DzNuttzOnYaChin]

So I'm gathering information on my setup and am getting mixed answers when it comes to alternators and the basics.

Questions:

1. Max Rpm ? I read on various webpages and get results from 16,000 rpm to 20,000 rpm.

  - Are we talking do not go over 16000 - 20000 continuous ? 

  - What about short burst/spikes that go up to 16000 20000 (like say jumping on interstate and rpms rev up short period) ?

 

I'm looking at the 370 amp E series but it seems the small 1.75 " pulley mixed with my 6.34" crank pulley will give me 23,500+ rpms if I hit 6500 engine rpm. 

That seems excessive for the alternator to spin at even at short periods. And the second option is the 240 amp with a 2.33" pulley which would still put me at 17,700 rpm..

Sounds like ill be damaging the unit according to specs. 

 

Guess ill start here for now and see what you guys think. I know heat is another huge factor but id soley like to focus on Rpm's and what damage I should expect. I don't want to be pulling out an alternator a year from now. let alone pay anyone to tow me home and wait a month for turn around time on repair. 

 

[8ten8]

Motor rpm vs alt rpm...I think you were handed incorrect info. Check the link below...read What's just below the alternator pics

http://www.usalternators.com/high-output-alternators/

[DzNuttzOnYaChin]

Quote

what makes you think i have incorrect info ? 

Take a look at these two links to see what I'm seeing. 

http://www.paperformance.com/rpm-calculator/

That one says 16,000 Alternator Rpm 

 

 

http://www.mechman.com/application-guide-pdf/

page 23 of Mechmans application guides states the 20,000 Alternator rpm  (recommends 5500 max Engine rpm)

[8ten8]

Thoes numbers look deceiving to me. Every manufacturer has there own specs i guess. After reading your link I ask myself, What exactly is "max engine speed"? If I were to touch 4k motor rpm in my vehicle, I'd be concerned. I cruz the freeway at 2-2.5k rpm and idle round 500rpm. For my US alt, That equates to rufley 6000 alternator rpm and 1800 alternator rpm and I have full output on ether end of that scale. Just saying. 

[DzNuttzOnYaChin]

9 hours ago, 8ten8 said:

Thoes numbers look deceiving to me. Every manufacturer has there own specs i guess. After reading your link I ask myself, What exactly is "max engine speed"? If I were to touch 4k motor rpm in my vehicle, I'd be concerned. I cruz the freeway at 2-2.5k rpm and idle round 500rpm. For my US alt, That equates to rufley 6000 alternator rpm and 1800 alternator rpm and I have full output on ether end of that I scale. Just saying. 

max engine speed = the maximum rpm your engine will reach while driving. 

some people have fatter feet .. And they may have a max engine speed of 7000 rpm when running it on the freeway.. 

your max speed seems to be 3500 rpm.. 

either way I'm guessing these numbers of 16,000 & 20,000 alternator rpm aren't misleading. 

 

this raises concern for warranty and it also raises concern how long these will actually last.

your US alternator doesn't give specs anywhere i see except some engine rpm stuff which is really irrelevant when you take into consideration every car had different size pulley .. 

 

lots of reviews praising the alternators buy then have disappointment only 14 months later and another expensive bill. 

what's your crankshaft\harmonic pulley size ? And what's your alternator pulley size ? 

[WalledSonic]

Depending on the bearing brand and style used, alternator max RPM is usually 16000 to 20000 RPM.  Yes, if you rev your engine high, then you need an alt with a pulley larger than 1.75".

A lot of people running large systems dont worry about it because when youre towing a metric fuckton of equipment, you dont drive around fast.  I dont rev over 5000 rpm specifically bc my car is cheap and is already over the GVWR.

Your comment about US Alts is misguided.  He actually explains the alternator RPM/pulley ratio in the side bar so you can calculate everything.  Some of the loudest systems out there use his equipment (alphablazer and alphaX, for example).  If you knew more about the manufacture of their alternators, you'd understand that laser welded connections are superior to the bulk of the competition, who tend to use solder, crimps, and aftermarket chinese components.  What are you saying about 14months?  English is poor so didnt quite understand you.

Any alternator manufacturer will put ANY pulley on your vehicle alternator.  Contact one and talk to them.  I've used Singer, US Alts, and Mechman.  All of them put out good power.  Theres tradeoffs with all of them, but you probably wont care about those minor details til you run one for a while and then try another one for comparison.

[DzNuttzOnYaChin]

9 hours ago, WalledSonic said:

Depending on the bearing brand and style used, alternator max RPM is usually 16000 to 20000 RPM.  Yes, if you rev your engine high, then you need an alt with a pulley larger than 1.75".

A lot of people running large systems dont worry about it because when youre towing a metric fuckton of equipment, you dont drive around fast.  I dont rev over 5000 rpm specifically bc my car is cheap and is already over the GVWR.

Your comment about US Alts is misguided.  He actually explains the alternator RPM/pulley ratio in the side bar so you can calculate everything.  Some of the loudest systems out there use his equipment (alphablazer and alphaX, for example).  If you knew more about the manufacture of their alternators, you'd understand that laser welded connections are superior to the bulk of the competition, who tend to use solder, crimps, and aftermarket chinese components.  What are you saying about 14months?  English is poor so didnt quite understand you.

Any alternator manufacturer will put ANY pulley on your vehicle alternator.  Contact one and talk to them.  I've used Singer, US Alts, and Mechman.  All of them put out good power.  Theres tradeoffs with all of them, but you probably wont care about those minor details til you run one for a while and then try another one for comparison.

I just have a feeling ill hit 6000 rpm .. I don't have a "fuckton" as you say .. 2 15 spl's , 5000.1d, and  3 yellow tops .. My goal is to drop the load and see what this amp can really do.. so the most amps i can get of course etc... 

 

Sorry about the comment on US Alternators. I was just getting at they don't list alternator rpm specs on the site that i seen. I did see however the ratio etc..

And unfortunately to your last point that's kinda what i wanna avoid (trying different ones or having to swap out at all for a long time). I don't feel that is justified if you spend 600+ on an alternator to only have it go out 14 months down the road. It cost about 300 for my dealer to do the work in labor. Plus if you don't have a back up your kinda screwed cause you have to wait on turn around time for repair. So making sure i understand rpms and alternator rpms seems very important and you really don't see them advertising about alternator speeds and limits. Seems like a catch where you buy one thinking it can operate like a normal one but in fact it cannot exceed 5500 rpm. Most people don't know that and they get responses from these guys like " yeah you should be ok". Or " don't worry about that. Its heat that kills them not rpms" .. 

 

 

Thanks for your time homes