Alternator Pulley Size

[Gear grabber]

I just went 3G on my fox. The pulley on the new alt. is about 2.75'' vs 2.5'' on the 2G. I found a deal on a 2.5'' and should have it in a few days. After doing some math,maybe i better stick with the 2.75''.
6'' crank pulley,6500 shift point,rev limiter at 7k.

2.75'' at 7k = 15,272
2.5'' at 7k = 16,800
2.5'' at 6500 = 15,600

 

[mikestang63]

I would swap to the 2g pulley as that is the same size as what was on the car before. The larger pulley will not charge as well.

 

[Mustang5L5]

What's the MAX rpm your motor will see?

You start getting up into Alt failing territory around 16K RPM. based on that alone, I'd prob stick with the 2.75" pulley.


At idle, that would give you 1745 RPM based on an 800 RPM idle with the 2.75" pulley. That's pretty damn close to making full power out of the alternator.

I do ~1600RPM at idle with my 3G setup and have no charging issues.

 

[mikestang63]

What's the MAX rpm your motor will see?

You start getting up into Alt failing territory around 16K RPM. based on that alone, I'd prob stick with the 2.75" pulley.


At idle, that would give you 1745 RPM based on an 800 RPM idle with the 2.75" pulley. That's pretty damn close to making full power out of the alternator.

I do ~1600RPM at idle with my 3G setup and have no charging issues.

MIke, how much time do you spend at 7k rpm with your motor? The majority of the time is spend from 1-4k. For the 2 seconds the car is at 6k and above while shifting, I think he'll be fine with the smaller pulley.

 

[Gear grabber]

The car idles at 1k.
With the low beams on,msd 6,340 lph pump,flex-a-lite 185 fan. 14 v with the 2.75'' pulley,at idle

 

[Gear grabber]

A little easier on the eye,the old 2g showed every bit of it's age.

 

[Gear grabber]

Broken,very broken. Just installed this last weekend,drove the car about 200 miles,but did not hammer it much (holiday weekend) all was fine. Was not finding much grip today. Stopped and lowered t/p on the hoosier QTP's Dropped the hammer at 40 in 2nd (4k) tires churned a little but did not blow them off. Shifted at 6600 let off,went to 4th,5th. Cruised a few miles and was pulling over to check something,when i see the temp gauge at 220 ! This is what i found. Alternator case cracked in 2 places,belt off. 130 dollar tow.

 

[mikestang63]

First time I seen that one. Was the belt too tight.

 

[Mustang5L5]

That's a new one to me. How is belt tension set on that setup? Possibly was too tight?


Sent from my big ass iPhone 6 using Tapatalk

 

[90sickfox]

First time seeing that, too. That sucks.

 

[Gear grabber]

Belt tension was fine. Yesterday i was mad,and not seeing what happened clearly.
Today with 20/20 hindsight the signs were there,i just did not pick up on them. Last weekend the the rear interior plastic panels were making some noise. This did not set off any alarm bells,they loosen and make noise regularly. (the tone did seem different...in hindsight) coincidentally i noticed the vibration after dropping the hammer hard in 2nd (more hindsight) perhaps the start of the crack ? Went through and tightened the panels up this past sat.
When i started the car on Sunday,the steering wheel was vibrating (never did that before) By the time i got to the gas station,things seemed normal. Over the next 20 miles i had stomped on it hard 3 separate times and the car was running very strong. At a slow cruise,40 4th i was feeling a dull vibe. Thought maybe the exhaust had loosed up. Climbed under there did some pushing pulling,all seemed ok,checked the lug nuts,all tight. A few miles later the wot blast that caused the failure. The signs were all there...i just failed to put it all together,until after the fact. Now i am angry with myself. A coworker said,look at the bright side,it did not catch on fire or toss the alternator through the glass hood or new radiator.True that !