Overrunning Alternator Decoupler (OAD) Pulley Mod

@marsrock7

The idea is genius. Strikingly affordable too.

Despite it being an extra complication, it redúces failure incidence.

The only downside is some extra weight.

I would have poúnced on it had I not been after a different goal. 

Btw on a 2ZZ a reduction of the alternator revs would do it a power of good. Better go for an oversize if you have that option.

 I was trying to find a marketing benefit as to why this is not more popular in the aftermarket world for older cars like ours and I found this. 

Solid Alternator pulley analysis: fastened with a nut and no protective cap
When the car is in operation with a solid alternator pulley, the engine and alternator RPM ratio is 1:1. Therefore, when the engine speed is at 4000 rpm, the alternator will be running at the same speed of 4000 rpm. In addition, when the driver decelerates and the engine is now running at 2000 rpm, the alternator will also be running at 2000 rpm, and if the driver wants to increase the engine speed to 4000 rpm again, you will need more gas to offset the resistance of the alternator. However, when using the X-Power alternator pulley, there will be an increased presence in power because there is an internal clutch with X-Power that has a delayed stop which allows the alternator to maintain high speeds. Therefore with a decrease in engine speed, the alternator pulley will not be brought down to the same rpm, rather it stays running at a higher speed and allows the vehicle to pull up to the high rpm much faster. Moreover, using X-Power you will experience an increase in acceleration speed, engine HP, and decrease in resistance from the alternator.

http://www.extend-racing.com/productb.php?no=172

  This thing is behaving like a mini intermittent flywheel. If you had a fixed gear car and was only accelerating in one direction there is no benefit.  For cars like ours you can offset some parasitic losses when you are accelerating and decelerating constantly where it would be beneficial in cornering. I think this is very minimal and probably not felt but the smoothness of the engines power delivery is probably going to be the most apparent difference.  

 I have urethane engine mounts and it vibrates the car. If this does what its suppose to do I have a feeling I will have a reduction in some of the vibrations that gets transmitted though the body of the car. 

@petrus

Yes it does increase rotational mass slightly but given in certain circumstances the entire rotating mass of the alternator is decoupled from the engine I see it as a win.

@dev

I like the mini flywheel analogy.... Never thought of it like that, the inertia of the alternator on decoupling helping to increase engine revs slightly faster. This is why hard on/off throtte isn't as harsh feeling, and why high rpm shifting is so much smoother.

Couldn't tell you if it decreases vibrations but hopefully it does. Been too long since I put it in and I only have one trans mount with inserts. The rest are OEM. Can't wait for your review!

If you have a 3/8 or small 1/2 inch impact driver this can be done in the car. Mine is a hex type so I have to add in a ~2" long adapter bit to use it with sockets. I actually chopped one of my hex-1/2" adapters down by about an inch and can now get the pulley on and off the alternator in the car.

Posted by: @marsrock7

If you have a 3/8 or small 1/2 inch impact driver this can be done in the car. Mine is a he's type so I have to add in a ~2" long adapter bit to use it with sockets. I actually chopped one of my hex-1/2" adapters down by about an inch and can now get the pulley on and off the alternator in the car.

    Originally I thought it was going to be a tight squeeze where I would have to get some sort of low profile socket and hex but it appears its not needed for most standard pneumatic 1/2 impacts or even the larger cordless, plenty of room.  I can see someone just buying a cheap electric from HF and just getting it done. 

 That pulley is basically stored energy that is used to offset parasitic loses from having to spin up again. I wonder if this technology is beneficial for the other accessories or even the crank pulley. The best part I like is that its always working to dissipate the shock from the engine. 

Posted by: @dev

 

 That pulley is basically stored energy that is used to offset parasitic loses from having to spin up again. I wonder if this technology is beneficial for the other accessories or even the crank pulley. The best part I like is that its always working to dissipate the shock from the engine. 

 

The airco and water pump are the two left. 

On the crank it would work for the whole lot but eliminate the harmonic damper.  I think I´d go for a crank pulley one.

The new hellcat and other modern superchargers also use this technology in their pullies. I'm sure it's hugely beneficial there, but those pullies also have a much, much harder load to carry than what the alternator does. The pullies cost several hundred dollars.

I'd go for a crank type too, if cost allowed. Not sure how that would affect things like AC thou.

I am extremely curious how this would interact with an SMT. I imagine a TCU relearn might be needed to get the best benefit in regards to shifting. If anyone with an SMT decided to try it, please share the results!

@marsrock7

The airco would work unaffected.

Ditto smt. The parameters revolutions and delta will change a bit but the cpu will keep following instructions based on the values. The underdrive pulley on the alternator had no other effect than a véry marginally smarter blip on downshifting.

Still want to try this on the SMT but currently have too many projects going on. It definitely has the potential to speed up the shifts with the SMT, so I’m anxious to try it. I’m surprised more people haven’t put one of these on but I should talk, right? Will eventually get around to it. Where’s the best price for one and what size pulley did people use?

@suoiruc

Pulley size depends on what your stock size is, and whether you want to under/over drive your alternator. The 2ZZ uses a 55mm pulley which is what the part number listed in the first post is. A few pages back I believe I and another member had found both 52.5mm and 55mm pullies to be used in 1ZZ alternators, so it may be best to measure your own before making a decision. Using a 55mm in place of a 52.5 yields a slight underdrive which could be desirable as long as you don't have a huge audio system to feed. I don't think there are many options larger than 55mm, maybe 57.5mm.

Like all new ideas, this one just needs inertia before lots of folk start doing it. Anecdotes from two people don't weigh much, but as a few become interested and brave, the evidence will pile up and more will start doing it 😛

Posted by: @marsrock7

@suoiruc

 as long as you don't have a huge audio system to feed. I don't think there are many options larger than 55mm, maybe 57.5mm.

The only audio I have is the exhaust note...

To keep an eye on things I mounted a volt meter when I swapped the 800 gram LiFe battery in. 

Again, going for a one way clutch on the crank would delete the harmonic damper. As does a lightweight pulley.

Again2 it is all about what you want to achieve/ need. 

The one way pulley is a genius idea; for a daily, not neccessarily for the just fun car.

As I wrote in a different thread the 1ZZ is a generic workhorse engine in hundreds of thousands, probably over a million cars. For a sports hobby application there are about 2 kilos to be gained on the pulleys. For economic application there is some 2%+ to be gained with a one way crank pulley. Etcetera.

@Petrus

In this instance I don't feel weight loss from steel pulley to aluminum pulley gains you near as much as being able to decoupled the entire rotating mass of the alternator from the engine in certain conditions. The point I am trying to get across is: this mod does increase the FUN factor. 

An improvement in effeciency from a mechanical part also directly translates into an improvement in power. 

If this pulley helps the SMT shift neater/faster like suoiruc and I hypothesize, you could have much to gain from this mod.

Reducing driveline shock from throttle inputs means faster engine response, and more stability while cornering.

I'm not trying to be pushy, just trying to get folk to understand this mod is about the Permagrin, at least for me. It may improve effeciency slightly but that's not what I'm after. 

Edit: For science I decided to weigh some stuff I have laying around. For pullies I have a small digital scale. For the alternators themselves I have a crappy analog scale. I have 2 1ZZ alternators laying around and I weighed them both, separately, and with me holding them, and got fairly consistent results. 

1ZZ alternator without any pulley ~12lbs (~5.44 kilos). What does the rotating mass weigh? I don't know but I think it is safe to assume at least 2/3 of the weight is rotating mass. So let's assume ~3.6 kilos.

6 rib 52.5mm steel pulley: 243.4g

6 rib 55mm steel pulley: (can't find it this morning, will update later)

6 rib 55mm OAD pulley: 467.1g (my spare)

Honda stuff...

7 rib 60mm steel pulley: 271.9g

7 rib 58.5mm aluminium pulley: 98.1g

7 rib 57.5mm OAD pulley: 505.5g ($35 paperweight, wrong threads for application)

Extrapolating this hodgepodge data, it appears an OAD pulley is ~1.9x the weight of a fixed steel pulley of the same size. Steel pullies weigh ~2.75x more than aluminium of the same size, and OAD's weigh ~5x as much as an aluminium pulley. 

So the question is.... Do you shave a static rotating mass of <200g?

Or gain 200-250g of rotating mass that allows you to decouple as much as 4kilos of weight (alternator+part pulley) from the drivetrain under certain conditions?

I hate adding weight to this car too, it's supposed to be light. But in the right scenario a part will supercede it's weight penalty with it's performance enhancements. I have 6 aftermarket braces on my car. Some replaced stock parts, some are outright additions. Is the car heavier than it was with the stock parts? Yes. Is the extra weight worth the improvement in handling? Hell yes! If I can I try to offset the additional weight elsewhere. But if gaining a few pounds or kilos increases the performance of the vehicle it's a worthwhile trade-off. I believe the OAD pulley weight is a worthwhile trade-off.

I purposefully left out anything regarding underdriving. I know this plays a huge factor too given the alternator spins 2.5 to 3x engine speed, but haven't had enough caffeine yet today to delve into that. Regardless, I believe a slight underdrive scenario could be accomplished with both fixed aluminium and OAD pullies.

@marsrock7

Dear Sir Marsrock, you róck. Totally my kind of thing.  Need no caffeine for it; live on an old farm and try do things eco meaning weeds galore. The horses lóve me weeding weeds as they get to eat the produce, me not so much but is does give me 98% of brain power to spare so do this stuff in my head daily 😀 

No beef nor difference of opinion on or from my side. No need convincing. Think the spinner genius.

NOT taking anything away from the latter observation:

Less rotational mass does not give or ´free up´ any hp the engune is producing. Yet on a sprint strip and all but a braked dyno, more power is measured. Sprinting and most dynos are accelerometers. Now, less rotational mass does mean things spee up quicker = accellerate better = more hp ´measured´.

This is why I think reducing rotational mass só cool: You are not tuning the engine, not increasing thermal load yet the car doés go quicker in all but top speed. 

This too explains my ´different goals´. The spinner pulley is genius towards something else.

Posted by: @marsrock7

... I'm not trying to be pushy...

Im trying to be pulley!

Hah.... Haha.... Hah. 

What am I turning into? 😒

@marsrock7

a bit of lighthearted relativity. Love that too 😊