NewCelica.org Forum banner

1 - 20 of 34 Posts

·
Registered
Joined
·
8,253 Posts
Discussion Starter #1
Does anyone know the shaft and thread dimensions (length and diameter) for a GTS alternator? Letting the alternator freewheel when it's not driven is very beneficial to belt and tensioner life, it's also a small boost to engine efficiency, and best yet reduces spinning mass on engine deceleration. The alternator rotor and shaft is typically about 90% of the weight of the alternator, so for ours it would be about 8-10 lbs of mass spinning at roughly 3x crank speed due to pulley ratio! That's a lot of energy to slow down each time you want to change gear. I'm a little light on math to figure the moment of inertia and how many lb/ft of stored energy that is,but if you've ever spun an alternator by hand and then stopped it by hand you can feel it's got some serious heft just at 100rpm, now imagine at 20,000 RPM!

I'm trying to figure out if there's a cross from a commonly available pulley to fit our alternator, I'm hoping maybe a later model Camry/Corolla uses the same alternator innards and shaft size so it's just a direct swap over. The pulleys for a 2010 Corolla are about $50. I have no idea if it would make any appreciable difference however EVERY new car is using them so there must be some benefit to offset the cost and enough for the bean counters across the industry.

From the rebuild procedure outlined in Alldata the shaft of a 2010 Corolla alternator looks like it's externally threaded and tapered like a standard alternator shaft. If anyone knows the dimensions of ours I can get the dimensions of the 2010 Corolla or other models from one of my suppliers at work as they'll be likely to have that stock on hand, but unlikely to have on hand the stock for a 10yr old sporty coupe/rare corolla model.
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #3
If I get anywhere with it I'll keep this thread updated.
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #4
RockAuto has a pulley on closeout listed that I'm going to purchase and attempt to install.
DAYCO 892003
It's both over running and decoupling so it'll dampen the alternator from the engine on both acceleration and deceleration which in theory should reduce wear on the belt (not that I drive it enough to worry) and reduce the spinning mass of the engine under those conditions. The only worry here is that the other pulleys are listed for JUST the GT model but I can't imagine the alternator pulley shaft is different between the GT and GTS alternator but there could be some clearance issue or it's just a weird catalog listing problem which is more likely and annoyingly common in the world of car parts.
 

·
Registered
Joined
·
4,466 Posts
Good luck!
 

·
Registered
Joined
·
17 Posts
RockAuto has a pulley on closeout listed that I'm going to purchase and attempt to install.
DAYCO 892003
It's both over running and decoupling so it'll dampen the alternator from the engine on both acceleration and deceleration which in theory should reduce wear on the belt (not that I drive it enough to worry) and reduce the spinning mass of the engine under those conditions. The only worry here is that the other pulleys are listed for JUST the GT model but I can't imagine the alternator pulley shaft is different between the GT and GTS alternator but there could be some clearance issue or it's just a weird catalog listing problem which is more likely and annoyingly common in the world of car parts.
Very interested in what you learn here.
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #7
The pulley came today, it looks like there's plenty of room to fit it and it may be the same or just a blonde hair larger diameter than the stock pulley. I'm hoping to get the alt pulled off the car and pulley swapped in the next couple months, I'll keep this updated.
 

·
Registered
Joined
·
4,466 Posts
*red

And good luck!
 

·
Registered
Joined
·
4,466 Posts
Lol
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #11
After much creaking and groaning (mostly from myself) I got the alternator off with my crappy tools here at home to take it to work and swap on the over running pulley. I may not reinstall it to drive until after I swap the DD IM since having the alt out frees up some space to work for sure.
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #12
It's on the alternator, alternator going on this weekend. Seems to fit on the alternator just fine,put some blue loctite on the threads just to be sure cause I had no way to hold the shaft still. Going to rely on the smack from the impact gun being enough
 

·
Registered
Joined
·
4,466 Posts
Progress!
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #14
Hey it's on the car now, installation went easier with more correct tools from work. I have a sinus headache and cold that's kicking my ass some I'm going to eat, take a rest, then start it up and maybe drive it some. First drive of the year too. The DDIM is not going on this weekend, I don't have enough focus and concentration to tackle a bigger task like that and I'm missing some tools I meant to take home to tackle that job anyway.
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #15
It *feels* much smoother when shifting at high RPM, either up or down shift, much less "kick" when up shifting at high RPM. All the time I've had the car when up shifting from 1st to 2nd or 2nd to 3rd at fuel cut there would be a fairly noticeable "kick" from the drive train because the engine is being stuffed back down several thousand RPM by the trans, most of that kick is gone now and honestly I like how that feels because it feels faster because it feels smoother. Whether it actually is any faster who knows, I really doubt it but this was only one drive to run the rust off the brakes with limited high RPM time.

I guess the conclusion is that it works, probably a better effect with a manual trans, and I'll update when/if it breaks or something changes or I have news.
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #17
Yes, it is a direct swap. That Dayco part number fits perfectly fine and has the same belt dimensions as the original pulley. You'll need a 17mm hex adapter or hex socket and an impact to install it, use loctite on the threads.
 

·
Registered
Joined
·
4,466 Posts
Pro tip: it's an automatic. It's not faster.
 

·
Registered
Joined
·
8,253 Posts
Discussion Starter #19
It probably isn't, but there is certainly less drive line shock felt through the solid front mount insert now than there was before. Significantly less too, I drove it again tonight and it wasn't my imagination at all.
 
1 - 20 of 34 Posts
Top