Overrunning Alternator Decoupler (OAD) Pulley Mod

@haloruler64

I think it was the Dayco 892003 but you should probably hear it from him. I was going to purchase that one for my 05 but decided to wait and let the idea brew a bit since i consider this car my out of town car and want it to be as reliable as possible to avoid breaking down away from home. It might be an option for my wife’s 03 but it already has the lightweight flywheel and 2zz clutch and was mainly considering the OAD pulley for quicker shifts on the SMT. 

55mm pulley (2ZZ, 1ZZ with 55mm stock pulley) is one that fits 2001 Chrysler Town and Country. Dayco 892003 or equivalent. 

52mm (replaces 52.5mm for 1ZZ) fits 2015 Chrysler 200 C. Litens #920032A or equivalent. This fitment has not been confirmed firsthand but all the numbers match.

It turns out I have two 1ZZ alternators laying around, one had a 55mm pulley on it, the other a 52.5mm. I doubt it really makes much of a difference, as there would be less than a 5% under or overdrive. If you want to replace your pulley with the same exact diameter it is recommended to measure your stock pulley before purchasing an OAD pulley.

I'm really curious how this would interact with an SMT. I've never driven one so I don't know how they shift normally. If it makes manual shifting smoother without a change in footwork, I imagine it would do the same for an SMT.

@haloruler64

I think it's the Dayco 892003

I don't understand how a few mm in a pulley can make such a difference. Anyone?

@hello

With the sizes of our pulleys 2-3mm can change the drive roughly 4-6%. The only times this should really be relavant are at the top and bottom of the full rpm range. Going larger (underdriving) may result in lower voltage output at idle. Going smaller (overdriving) could improve voltage output at idle (helpful to those with power hungry audio) but also there an increased risk of overspinning it at high RPM. Math can be done to figure out if there is potential for overspinning, but we would also have to find out what the max safe rpm for our alternators is. Personally I don't think overdriving by ~5% would kill an alternator, as I expect manufacturers have a higher safety factor than that. I'd be more concerned about underdriving and having poor voltage output at idle.

So it's related to the electrical power it produces. That makes sense given that's what alternators do. I guess 5% is not insignificant. Thanks!

Posted by: @hello

I don't understand how a few mm in a pulley can make such a difference. Anyone?

The size isn't making the difference, it's the fact that it has a one way clutch. 

Posted by: @haloruler64

Posted by: @hello

I don't understand how a few mm in a pulley can make such a difference. Anyone?

The size isn't making the difference, it's the fact that it has a one way clutch. 

Correct, the decoupler clutch and torsion spring are what make this thing magic. You can learn how they work and even see a video demonstration of the three different types of pulleys available at this site:

http://www.decouplerpulley.com/basics.cfm

Just wanted to update, this is still functioning flawlessly.

I'm currently trying to find one that fits my TSX...

I’m on board. I will see if my impact guns will fit. If they do I will be doing this modification. 

@dev 

Hopefully one of your impacts fits.

I'm looking forward to feedback from others. 

I installed a newer 7 rib Toyota pulley in my TSX a couple weeks back. Stock pulley was 60mm, ended up with a 55mm on it thou. I thought I had found one that was 57.5mm 7 rib but I am now unable to dig up the part number I forgot to save. Nonetheless... The results are quite similar. I will say I can't feel it quite as much, but the car is 1000lbs heavier than the Spyder, and a 2.4l long stroke engine, so more rotating mass as well. In the TSX I notice it most in very low rpms. A common complaint about the car (especially with MT) is harsh jerking with on/off throttle inputs at low rpm. This has subdued that annoyance more than anything else I've done to the car. Shifting quickly is also smoother. Imperfect rev matches on higher rpm shifts don't make for such a harsh transition. Worth the $40 in my eyes.

The one in my Spyder is still doing its job as well. 

I have a m12 Milwaukee that should fit but it’s only 120ftlb reverse torque. It’s probably not enough and I may need to bust out the IR which should do it if it fits.   
I have two question after seeing many videos. When you tighten the new pulley using the 17mm hex where you apply the thread locker? And when tightening wouldn’t the coupler spin without any resistance to tighten it down with no resistance since it’s decoupled. 

120ftlbs should be enough. I have a crappy impact that barely takes the lug nuts off of my cars (80ftlbs) and it still did the job. I guess it depends on how tight the original nut is on your current pulley. Mine was pretty tight, I probably had to smack it with the impact for about 10 seconds before it broke loose but it got the job done nonetheless. 

I applied a small amount of locktite blue directly to the threads on the alternator shaft. You could also put them on the threads inside the new pulley since that's easier to reach. Same results.Our pulley system runs clockwise so the frewheeling would happen when counterclockwise. Either way, I've put the new pulley on an alternator, then had to replace the alternator and swap my pulley over. Both on and off with locktite blue with no issues. When installing I impact until the alternator is spinning with it. Then stop and hit it with a couple more short bursts. 

Im all in now.  I have plenty of room to spare and it can be done on the car.  Im willing to bet that although we have a hard time changing the alternator because of location it has the benefit of easy access to the pulley with an impact. I do have to buy a 22mm socket and a 17mm hex. Good thing is it doesn't have to be low profile. If this work out it will be mod of the year just based on how easy it will be to replace. 

I did some research into this. Spent literally hours and it is a fascinating bit of technology. I would say its close to a free lunch which is rare.  

Its been use in the industry for over 20 years but not all manufactures got around to it. Toyota has them on most of the cars after 2005 so I probably have it on the Lexus. Its not just an overrun its also a decoupling device that is always working to limit the torque in the system which places strain on the many of the serpentine components. It also acts as a damper for the jerky operation of a combustion engine firing cycle that is transmitted thought he crank pulley. It reduces noise  during operation including start up and shut down, and will increase the service life of the bearings of the various other pulleys including the tensioner. 

 The reason why the industry is using it is for a verity of reasons as it can reduce the cost of the manufacture of components like the tensioner, pulleys and belts because they do not have to be built as strong and you no longer need as high of a tension on the belt to resist the violent forces that could derail the belt.  It also increases service life of the engine components.  Surprisingly it increases efficiency of 1% which doesn't seem like much but its the difference between using synthetic oil or using a lighter viscosity oil which is what the industry strives for to increase CAFE ratings.  

As far as using it in our cars its 100% safe and its 100% backwards compatible as the DAYCO 892003 is listed for most all 1zz and 2zz applications like the older Celica and Matrix. This means its the right part, not a adaptable mod from a different application that might have consequences. Because they are manufactured to very high standards it will be like OEM.  

 There is one downside and that is the part does eventually wear out somewhere above 100k miles. The mechanisms failure is generally in the locked position so it will no longer decouple and behave like fixed pulley that makes noises to let you know its done.

 I found one up the street for $55.  This is too good to be true as far as ease of installation and the benefits that come with this device that is close to OEM as one could get.