Does it make anymore power by changing the under drive pulleys?

I've never experienced any issues when using the A/C.

And I would definitely swear by them. One of the most noticeable gains you will feel, thermo fan conversion and underdrives.



Yes. I'm not sure how much but some people have claimed 10-14hp.

are there sets availible for au xr8?

nope. the au v8 motor is already underdriven from factory

AU's are not really underdriven like a set of aftermarket underdives. In fact after measurements it's barely any different to E-series. Unfortunately the AU's integrated crank pulley makes for difficulty in making as set.

ahh. i thought it was already done..
well that answers why there are none available.. was just put in the too hard basket.

Does this mean that there is none available for Series 2 EL's either?

"Series 2" EL uses underdrives the same as any other E series. It's not an AU engine.

EB-L are all the same, no matter what series.
I believe Kenny Brown and/or Steeda used to make a set for Explorers but the details are sketchy.
Here's an AU Balancer(left) compared to the E-series modded one we did. As you can see, we could do a reverse offset pulley to allow it to line up. Then we'd be getting somewhere for AU.

Good to know, thanks

Under drive pullies are unnecessary for AU V8 as the factory already thought of it. The AU crank pulley is a full inch smaller in diameter than an e-series crank pulley so the accessories are spun more slowly, just the same as installing underdrive pullies on e-series

Ok Lads,
After measuring(reasonably accurately so, correct me if it's out a bit) all of the pulleys, I've worked out the approximate drive ratios to each of the accessories. I've left out the A/C deliberately because it gets turned off when you boot it so it's effectively an idler. I also have to confirm the Underdrive set Alternator pulley diameter which is actually slightly smaller than stock to speed it back up a little to reduce chances of charging problems.

On E-series
we have;
Alternator 2.827:1
Water pump 1.355:1
Pwr steer 1.12:1

For AU it's;
Alternator 2.9:1
Water pump 1.272:1
Pwr Steer 1.19:1

That means;
AU alternator is overdriven approx 7% compared to E-series.
AU Water pump is underrdriven approx 8% compared to E-series.
AU Pwr Steer is overdriven approx 7.5% compared to E-series.
Average 3.3% underdriven compared to E-series(or in technical terms f**k ALL!)

Now E-series underdrives;
Alternator 2.27:1 = 55% underdriven compared to stock E-series
Water pump 0.778:1 = 57% underdriven compared to stock E-series
Pwr Steer 0.842:1 = 28% underdriven compared to stock E-series
Average 46.6% underdriven compared to stock E-series

So you can see there would be substantial advantages to underdrives for AU as there is for E-series.
Anyway I'm cooking up a little excell sheet so you can punch in whatever pulleys you have on any engine and it'll spit out your drive specs.

For "power you can feel", the only pullies that really matter are crank & waterpump. As you correctly say, a/c is user selected and ecu controlled. The alternator is similar, drag is 99% related to battery charge status and controlled by the regulator rather than armature speed except at very low RPM. In a correctly operating vehicle the alternator is only recharging the battery for maybe 1-2 minutes after a start-up. Then it is just maintenance output, but still controlled by the regulator & virtually independant of shaft speed with the tiny exception of the internal cooling fan. The PS pump regulates fluid flow, so is again virtually RPM independant except at very low flow rates (RPM).

The waterpump & mechanical fan are the only belt driven accessories that have an almost direct power input relationship to the RPM at which they are rotating. This is caused by internal friction of the water moving through the radiator tubes, the thermostat & the rest of the cooling system. Pump impellor speed increases as engine RPM increases, which attempts to force more water through the same size restrictions. ie. the cooling system volume flow is regulated by restriction rather than energy input. And of course by the fan (if fitted) trying to pull more air through the radiator.

This is why the AU has a lower parasitic drag than the stock E-series, the waterpump is spinning considerably slower. It is also why some underdrive pully sets only have crank & waterpump pullies, the others are of no real benefit besides perhaps looking pretty.

For those that don't understand, just for the waterpump...

8% is NOT considerably slower.
57% IS considerably slower.

My biggest problem with underdrives is if the water pump is running slower on a fragile alloy head (i6), is that not a bad thing????? I was looking at getting underdrives for my Ef i6, but if the water pump is running under its normal flow potential wouldnt any power gains be useless seeing the head will be running hotter and degrade faster?