Overrunning Alternator Decoupler (OAD) Pulley Mod

 Im not looking or any gains but if motor runs smoother and the shifting improves I would be happy. I wouldn't have done this if the alternator has to come out but since it looks too easy to access why not. I also wouldn't have done this if it was a "aftermarket part" because I wouldn't trust the technology unless it was proven

Everything is ordered and I added a little PB blaster on shaft  so it might creep in and make removal easier. 

Dayco 892003.   Rock auto recommends the installation tool.  Does it need H10, or H17-H19, or H21-H28?

@cyclehead

You need a 17mm hex bit. I have this one: 

https://www.amazon.com/dp/B004W81LPY/

It's 1/2in drive, if you are using a 3/8in impact make sure you have some extra space for an adapter. If I remember, tomorrow I will measure the total length of the bit itself. 

Posted by: @dev

 Im not looking or any gains but if motor runs smoother and the shifting improves I would be happy. I wouldn't have done this if the alternator has to come out but since it looks too easy to access why not. I also wouldn't have done this if it was a "aftermarket part" because I wouldn't trust the technology unless it was proven

Everything is ordered and I added a little PB blaster on shaft  so it might creep in and make removal easier. 

 

 

It will work and imo will suit your purpose. It is a perfect example of different goals; adding a minimal bit of weight yet improving the ride. Much like a/c: taking it out is an easy gain of 10 kilos, say 1% weight, but more than a 1% loss in comfort.

The installation of the underdrive pulley on mine was a doddle.

Posted by: @marsrock7

@cyclehead

You need a 17mm hex bit. I have this one: 

https://www.amazon.com/dp/B004W81LPY/

It's 1/2in drive, if you are using a 3/8in impact make sure you have some extra space for an adapter. If I remember, tomorrow I will measure the total length of the bit itself. 

Thanks.  I plan to pop one on my SMT and see if I can tell any difference with shift speed.

Posted by: @petrus

Posted by: @dev

 Im not looking or any gains but if motor runs smoother and the shifting improves I would be happy. I wouldn't have done this if the alternator has to come out but since it looks too easy to access why not. I also wouldn't have done this if it was a "aftermarket part" because I wouldn't trust the technology unless it was proven

Everything is ordered and I added a little PB blaster on shaft  so it might creep in and make removal easier. 

 

 

It will work and imo will suit your purpose. It is a perfect example of different goals; adding a minimal bit of weight yet improving the ride. Much like a/c: taking it out is an easy gain of 10 kilos, say 1% weight, but more than a 1% loss in comfort.

The installation of the underdrive pulley on mine was a doddle.

 Thats the thing I do not know if it will work or be any benefit.  The way the belt system is designed for these engines are just fine and not really problematic.  

 I had to do some hard research before I would trust it and at this time I believe its a wash as far as any power gains or loss. Even if it weighs a little more I doubt it will translate into something you could feel as a loss. As it is I think the under drive alternator pulley is not really worth the trouble and is overrated.  I also think light weight aluminum flywheels are not worth the trouble either as they do carry a risks and tradeoffs going up hills. I never felt these little bolt ons  amounted to much having driven the same cars with and without them. I would say the only bolt on modification that actually made all the difference in the world is the downpipe.  That one modification alone was a night and day experience and it only makes 10hp but for a small car like ours thats like 50hp in large heavy hp cars.  When I think about it now the crank scraper made almost as much as a light weight flywheel which you could actually feel but it was just a little something but thats not what I bought it for. There is way too much consumerism for such little gains or in some cases no gains. 

Here is a good example of how the aftermarket gets it wrong. This is why people fail because they try to find yes people to justify their bad choice in modifications. 

https://alternatorparts.com/clutch-to-solid-pulley-conversion.html

 This guy really doesn't understand that you cannot use a solid pulley in an application where a OAD pulley is used. If a system as a whole incorporated it in their design then you cannot use a solid pulley because the belt tensioner and the tension on the belt is weaker. I found this out when I read the literature from Gates and other manufactures that make them for the OEM.  

 Interestingly enough I also found out that the reason for this technology is because car manufactures are cramming so much electrical nonsense in modern cars they need higher output alternators which creates a problem because of drag which leads to belt slippage and other issues which you will need to beef up the tensioner.  These OAD pulleys solve this issue and at the same time increase efficiency and wear of other components. 

 The trade off is they can fail but the failure rate is overblown as most of them last well past 100k miles. It is a good tradeoff for what they do.  For our cars we can gain some of the benefits with backwards compatibility.  It is possible  that these  pulleys probably prolong the regulator diodes  life by filtering out voltage spikes as the rotation of the alternator is steady with the least amount of fluctuation. 

Posted by: @dev

 

 Thats the thing I do not know if it will work or be any benefit.  The way the belt system is designed for these engines are just fine and not really problematic.  

 

There does not have to be a problem for a mod to effect in a gain and the gain does obviously not have to be a performance one.

@dev

I did not feel anything I would call an obvious gain in rotational weight.... Then again, when I swapped wheels and tires around and gained 2lbs per corner I barely felt that. 

As far as lightweight flywheels I stay away from aluminium and will only go for chromoly steel. I like my lightweight flywheels but I do recall the gains on these particular engines being fairly minimal due to the OEM flywheels being relatively light compared to most OEMs. I think on my 2ZZ switching to chromoly lost me only 3-4lbs. In my experiences in the Honda world, usually a "modest" lightweight flywheel choice will drop you 6-10lbs, and the lightest available are usually a couple lbs lighter than that. IIRC my TSX had an OEM flywheel weight of ~18lbs, my chromoly weighs 11.5lbs, and there are options available down into the 8lb range. Dropping flywheel weight does mean more throttle modulation on steep grades, but nothing I would call problematic. The cruise control in my TSX has no problem adjusting so neither should any human being 😛

I agree the gain from the crank scraper was very similar to the gain from the lightweight flywheel. Both were modest, but present nonetheless.

Back to the OAD pulley, I don't believe it gains you any dyno measurable power. The gains are felt on the street. Quicker throttle response and smoother shifting make for a faster car. We all know the difference between a perfect upshift and a poor one. The perfect shift keeps power delivery smooth and increasing, and the poor shift is jarring and bogs the engine momentarily before power delivery resumes. This doesn't make all your shifts perfect for you (that's still on you) but it does make imperfect shifts... less imperfect.  

The original clutch hydraulic system in my TSX had check valves and dampers in it to slow and smooth the flow of fluid and make for a smoother shift. I like to think this pulley swap creates a similar effect, but without the negative effect of slowing the process down.

Do you feel like the rpms ramp down slower and not as abruptly so when you make a gear shift the clutch engagement is smoother?  

Posted by: @dev

Do you feel like the rpms ramp down slower and not as abruptly so when you make a gear shift the clutch engagement is smoother?  

 

They should ramp down quicker...

@dev

I am not entirely sure if the RPMs are dropping slower or faster than with the fixed pulley, there definitely isn't anything I would call "rev hang" like I experience in DBW cars. It isn't something I took note of when I swapped. Given the way the tach acts in this car, one would have to gauge this by ear and feel. Or.... Log RPM data with third party hardware. Maybe if I get really bored I'll swap pullies and go log some accel/decel RPMs with both. 

What I do know is decel is less abrupt, the jolt from WOT to closed throttle is not as harsh, the alternator immediately goes into freewheel while the engine revs drop. So initially, rpms probably are dropping slower, after that first half second, who knows. And after that first half second, it may not matter because the shift should be complete soon anyway.

Now the more I think of it, the more I'd like to see what RPM and Throttle Positions graphs would look like between the two pullies.

Maybe its eliminating the shock to the system soon as the clutch is re-engaged. That jerk is probably taken out of the engine by both the free wheel event and torsional spring at other times. With a fixed pulley once you re-engaged the clutch the alternator  has to slow down abruptly which probably causes that energy to be transferred to the driveline. That is pure speculation on my part.  

Posted by: @dev

Maybe its eliminating the shock to the system soon as the clutch is re-engaged. That jerk is probably taken out of the engine by both the free wheel event and torsional spring at other times. With a fixed pulley once you re-engaged the clutch the alternator  has to slow down abruptly which probably causes that energy to be transferred to the driveline. That is pure speculation on my part.  

 

With a fixed pulley it slows down/speed up with the crank. Shifting could be quicker and smoother because of the rotational weight decoupled. Also there will be less torque reaction.

The kinetic energy of the spinning alternator rotor is quite considerable because of its high revs. Decoupling that makes rev changes easier. Gear changing involves rev changes. Thus goes with less forces involved. Simples. Should be noticable. By the smt too; should be a bit quicker.

@marsrock7

 When the time comes I will take pictures to document a DIY. I will then give them to you so you can do a write up for others so it can be placed in the DIY section here. You should get due credit for this for the community at large. We can then go on adchat  and link it here.  This is where a free board can make things happen for our platform. 

 I read another user review for a person who adapted it to a police interceptor and noticed the same thing of being smoother shifting. It wasting something small it was quiet noticeable.