has anyone tried or know of someone with an fg with underdrives? ive found some good priced ones, but when ive enquired at 2 performance shops here in perth about them, one has said they cause issues with the crank on the fg, and the other said the power increase is that negligible on an fg 6 cylinder as to make it not worth the hassles. any inputs?

yea iv heard they cause issues aswell for the gains im not really willing to risk it... but if you had a good tuner that could work out the issues with it, im sure it'd be worth lookin at... but for what it cost for the kits, ur better of getting a set of extractors...

already have extractors, cat, and twin 2.5 stainless exhaust
only ask as i was offered a set on the cheap, but got told they cause issues which i hadnt heard before. thought id look for some one with any experience or similar issues on here first

You will lose a little bit of charging power from your alternator while idling, and that's about it. You free up about 10kw, so it's really up to you whether you would rather have a little bit more power, and sacrifice some charge (it's fine if you're cruising etc..).

yea the loss in charging i can cope with, wondering if theres any substance to the claims of crank issues in a fg?

This is what someone told me, on a NZ forum, regarding the BF (pretty much the same motor, less 5kw). I dunno what to think, but this what he said:

"I fail to see the overall benefit, all the underdrive pulley does is reduce the initial inertia of getting the othe pulleys to rotate on acceleration, and also reduce the rpm of the waterpump, alternator, Air conditioner and Power steering.
The thing is to reduce diameter of the crankshaft pulley can have a negative impact on the drivability of the car at low speed, it can also lower the voltage output of the alternator, slow the cooling of the engine. Turning the power steering pump slower so it is less effective at low speed (just the rpm when you need it).
If the harmonic balancer is removed to achieve the smaller bottom pulley size it could even have a negative effect on the crankshaft vibration dampening and cause early crankshaft failure.
On a race car doing 9000 rpm all day yeah go for it, they get rebuilt every other week, on a big lazy 6 cylinder that does 2000 rpm for most of it's life. I can't see the point apart from making the car drive like a pig at idle.
Sure it'll give you more horsepower , but you'll probably have to turn the idle up a few hundred rpm just so you dont stall when turning the steering wheel at idle, and then altering the valving in the auto so the car doesnt creep too much at the new idle speed (if you run auto)
And that is probably why it has to go for a tune...

If you want free horsepower get rid of the Air Conditioning belt (or leave it turned off) good for 10 to 15+ hp and you'll get almost another litre/100km too.
Spend the money on getting a set of nice camshafts to release some of the additonal grunt the six can give.
Failing that just bolt a turbo or supercharger on and leave everyone else for dead..."

Well it turns out that old advice ^^^ above, was a load of crap.
They have little (not even noticeable) effect on your aircon, cooling, charging, and people report much better throttle response; dyno results have shown around 10rwkw gain on I6's.
The kits include the harmonic balancer so they won't hurt your motor.
So Im getting mine fitted on Monday