OAD alternator pulley.

[Dev]

 Im placing this topic in the general section since it might not exactly be a performance benefit.

What is a OAD pulley? it's an overrun pulley that has a torsion clutch damper  that has been around 15 years and after 2006 Toyota has been using them in some of their applications as they have many benefits.   

 Here is a good overview of what it does.

http://www.extend-racing.com/productb.php?no=172
 There are some other benefits like smoother shifting and smoother overall engine that has been reported by two people that have adapted them for the 2ZZ. This part should also work for the 1ZZ and it is theorized it might help with SMT shifting.
 
 On our forum we are still investigating and its preliminary but it makes for a interesting topic of discussion as a backwards compatible part that could work towards our benefit of improving our engines. It appears that one of the manufactures is listing backwards compatibility with 1ZZ and 2ZZ engines. I should receive my pulley for testing tomorrow and I will report my findings. 
  I just wanted to bring this to your attention as there is now a possible Toyota part number that has cross compatibility that could work making it easier for you guys to obtain it for your own testing.
  It is rare to have something that might improve our engines operations and I hope my findings yield good results this week.  Much of the credit does to Marsrock7 from MR2-spyder.com and Bitter from Newcelica.org for discovery.

[shnazzle]

That's interesting. Aaaaggess ago I was looking at alternator replacements in the Demon Tweeks catalogue that offered this. Never figured out what kind of amps etc the alternator needed and too lazy to figure it out so I left it. But, it's pretty cool that the pulley can be changed to one of these.

[Dev]

The only issue with this part is that it's a point of failure which is estimated to be 100k miles. It will make noise from the bearing and it will just need to be replaced however the benefits are there for prolonging your other accessories, belt and belt tensioner.  It is suppose to make the engine run quieter and smoother and shifting is improved.

Here is the quotes from the two people that have tried it.

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.

My first impressions as of a couple days ago (having not re-read the thread first):

Hard off and on throttle is smoother, deceleration out of gear is a bit slower. High RPM shifting is WAY smoother. The best way to describe it is... Smoother. I'm positive this is much more effective for decreasing engine load than a lightweight alternator pulley, or even underdriving. The rotational mass of the alternator itself being decoupled from the pulley system is a respectable gain. There may even be a touch more power, I can't judge that yet... ECU needs to relearn it's fueling still.
My usb charger is also my voltmeter.... So far voltage is consistently 14.2+. No noticable difference in voltage output.

Update: nearly every shift feels perfect. It's very difficult to make a jarring shift now.

TL;DR:

Bitter and I have come to the same conclusion on the effects. This pulley reduces drivetrain shock and just makes everything feel so much smoother. The drivetrain feels lighter and more responsive to throttle input. I  love how it feels and don't plan to ever go back to a regular pulley.

This is a direct bolt-on, pulley is same diameter and works with original belt. Both test cars are 2ZZ but if I recall correctly the pulley size on 1ZZ is the same so this mod could also be able to be done on a 1ZZ.

[Petrus]

I´s say this is the ideal thing for 105:
It will make the standard car more pleasant still, does not upset anything and is quite affordable.
As it uncouples the alternator rotor whenever the crank pulley would slow it down, it reduces torque reactions on load changes.

It is not a performance enhancing mod. because it is a bit héavier and as such does not speed things up easier, although it will make re-speeding up easier.
It máy improve life expectancy of the alternator but if that is the goal an underdrive pulley remains the more effective way.

It works, can be called an OEM retro-fit (Jason!!) and is a doodle to mount. When I looked at the underdrive pulley and found this one too and thought it genius; something worthwhile for almost nothing. I opted for the lightweight underdrive pulley but then I also took the speakers and carpet out p.e. so...

p.s. it does not affect the power generated by the engine ofcourse.
Accellerating in the same gear it wil cóst a minute bit extra because the rotor still accellerates and the pulley is a wee bit heavier; on the drag strip it will gain an immeasurable fraction of time because the rotor needs nor re-accelerate.
As it does not affect the speed of the rotor when coupled, it will not affect the voltage.
With a lot of electrical users switched on, the stator will still slow down and the freewheeling effect will be less.

[Alex Knight]

Interested in your findings @Dev (and 2ZZ part number also!).

[Dev]

Interested in your findings @Dev (and 2ZZ part number also!).

Absolutely. I will hold off on the part numbers as we are sorting though it. For the 1ZZ it might need a little larger belt but its still murky because no one has fit one yet it they have kits available that has the belt and tensioner included.
 For the 2ZZ we do know for sure one of the parts works but having you order a cross reference part on your end may or may not work but its most likely that it will so if you are up for a little experimentation for fitment to confirm it would be a benefit to the community.

[Dev]

 I just wanted to update this.  At the time of adding the pulley I also changed my passenger side mount back to OEM from poly because it was unbearable. The mount made a significant change that it overshadowed the pulley. I was looking for a performance shifting benefit and did not notice much if anything at all. it felt a little smoother but it was a wash. At that point in time I put my car away and let it sit for three months during the summer.

 Fast forward to last month and I decided to drive it again forgetting that I added this OAD pulley. I noticed that the shifting of the car has improved quiet a bit as if the gear shifts were smoother.  It actually feels like my friends MX-5 which has a very nice gates. What I was focusing on before was high speed shifting but it wasn't that much of a difference however driving normally there is a difference.

 I believe  eliminating the shock of the alternator drag when letting off the gas by way of the OAD makes matching the gear speeds better.
  Even though I feel it has little effect driving at high speeds I like the change because 90% of driving is at normal speeds and you can feel the improvement it makes all the time which is satisfying. 

[Petrus]

Glad it works out satisfactory Dev!

[Dev]

Glad it works out satisfactory Dev!

 I like it and it is very different than how I thought it would be. If it was difficult to do I wouldn't suggest it but since its relatively easy to install I think its worth the trouble just for the shifter feel which is smooth and crisp.   

[Petrus]

I like it and it is very different than how I thought it would be. If it was difficult to do I wouldn't suggest it but since its relatively easy to install I think its worth the trouble just for the shifter feel which is smooth and crisp.   

Same thing I conclude abouth the lightweight underdrive pulley.
I think it übercool that two opposing tracks still both lead to ´Rome´.

[Nvy]

@Dev Can you give us another link because the above doesnt work anymore? Id be tempted to try it

[Dev]

I like it and it is very different than how I thought it would be. If it was difficult to do I wouldn't suggest it but since its relatively easy to install I think its worth the trouble just for the shifter feel which is smooth and crisp.   

Same thing I conclude abouth the lightweight underdrive pulley.
I think it übercool that two opposing tracks still both lead to ´Rome´.

 I do not think they are exactly the same thing but there might be some slight overlap. The lightweight under drive pulley is still connected to the alternator. It will have a slight if any performance benefit when accelerating where the OAD trades that for decoupling the shock of abruptly decelerating the engine through its torsional clutch which mitigates the rpm drop when you let off the gas and engage the clutch.     
 This lack of abruptness in the rev drop with the timing of the gear shift makes engagement of the gears feel smooth. Its a milder form of the effect of rev matching but all the time which can be appreciated. For others that have done the mod they have noticed it everywhere but I found the greatest effect when shifting from 1-2 and the maximum effect from 2nd-3rd but mostly at lower revs probably because I have a kevlar clutch which is very grabby and now that the rpms are higher when engaging it feels smoother.
   
   I had to re envision this because it initially did not make sense to me why its mostly felt in the shifter like something has improved with the gear box but that is not the case.

[Dev]

@Dev Can you give us another link because the above doesnt work anymore? Id be tempted to try it

Here is the link to the entire discussion. It includes various part numbers and documented impressions. 
 https://www.mr2-spyder.com/community/power/overrunning-alternator-pulley/

[Petrus]

OBVIOUSLY not the same; more the OPPOSITE.

Yet they both, in different ways, lighten the load by the alternator on the engine.
The one by freewheeling on the overrun, the other by reducing mass/kinetic energy so both accellarating and decellerating.

Thus arriving at Rome from opposite sides 

[Dev]

OBVIOUSLY not the same; more the OPPOSITE.

Yet they both, in different ways, lighten the load by the alternator on the engine.
The one by freewheeling on the overrun, the other by reducing mass/kinetic energy so both accellarating and decellerating.

Thus arriving at Rome from opposite sides 

 I do not think they translate to the same effect. The goals of both are very different.
 I would say the lightened pulley is more of a performance modification where the OAD is not and it makes it worse by being more weight.

 This would in theory make the OAD pulley a stupid idea but its not because the performance of the lightened pulley is negligible and any performance downgrade of the OAD pulley is also negligible so its doesn't really translate into anything that is appreciable as a downgrade.   
 The OAD pulley on the other hand is for feel in smoothness which is not the main feature of the lightened pulley although one can make the argument that there is but I doubt that it can be as appreciated compared to the OAD which completely decouples the pulley from the alternator eliminating the shock enough to make a difference.
 I would say one is going to Rome and the other to Japan. For a street car that is driven most of the time in actual traffic with lots of shifting at lower RPMs the OAD is a real joy especially if you have a grabby engaging clutch.

[Petrus]

For a street car that is driven most of the time in actual traffic with lots of shifting at lower RPMs the OAD is a real joy especially if you have a grabby engaging clutch.

... and I´d say the same for an overdrive pulley even with a smooth clutch :-)

Enjoy!!!