Can anyone tell me definitively what the effect of replacing OEM pulleys with an underbody crank pulley would do to my engine? Who has it on their G-35 and what results have they obtained while using it so far. I am close to installing a lot of mods on my car, and I have been given the opportunity to install a complete set of accessory and crank under body pulleyts for just $75 with zero labor charge.

After speaking with a few experts on underbody crank pulleys, I was told that if installed correctly, it had little or no effect on the engine. However, they said it does not generate any horse power but frees horse power being robbed by the heavier OEM pulleys. I was adviced to replace all the crank and accessory pulleys at once, if I had to do so. I was told not to replace just the crank pulley alone as this would cause uneven load on the accory pulleys.

I was also told that if I ever decided to install a supercharger in the future, I would have to re-install the OEM pulleys back, as they are able to handle the additional loads of the supercharger.

I was also told that installing the under body crank pulley would actually allow the what the pulley lacks on weight, which is used to power accessories, it would make up in speed, since it spins faster than the OEM part. I also worried that at idle, my accessories may not be working up to manufacturers specification, and thus could harm my accessories. So, traffic jams could be a nightmare for my car, but mvoing above 2,000 RPM works just as fine with the OEM and after- market underbody crank pulleys.

Does anyone have a sound advice on this issue, as I have only a few days to make the decision to install the underbody crank pulley at a decent price.

Of course, I am going to install Stillen single tip Cat-back exhaust, 5/16" Plenum spacer, Mrevv2, JWT pop charger with z-tube, all at the same time. Approximate costs of parts labor would be about $2,450. My car is a 2007 G-35 6MT RAS(Rear Active Steer) NAV VLSD 19". I am happy with the suspension as is because of the Rear Active Steer. So, i think I might just replace the coils for Eibach coils when I am ready to install new tires.

Next year will be side corners, front facia, and tail lamps.

I need anyone's take on this matter of the underbody crank pulley as soon as anyone can respond (SOS). Thanks for all your help!

you're talking about an underdrive crank pulley. IT'S AWESOME! everyone thta has them loves them! i know i do!

I've read that the only negative would be trying to run an amplifier in excess of 600w RMS... that would cause problems with your alternator and charging system etc... but if you keep the stereo fairly simple. you'll have no problems...

BTW... pulleys are the best ratio of cost:power available for the G... (quoted from stillen.com) GOOD LUCK!

(Looking at your mod list)....your making me jealous now

I also heard about the possible crank wobble and bushings wearing out. Any thruth to this? I also heard that it might affect the power steering pump and possibly the alternator Any truth to this? How long have those who have used the underdrive pulley been using it? I heard of a person who started having issues at 1.5 years of installing the pulleys. I also heard that installing the pulleys require more routine inspection of the belts and parts. Any truth to these assertions?

Why do the auto manufacturers not use these underdrive pulleys to begin with?

when you get a few hours of free time read this post i started in May 07.

zerothread?id=251971

short answers:i've heard of the wobble issue but never spoken to anyone that it has actually happened to. i've heard of some sort of balancer that "needs" to be installed to correct this but it does not need to be installed.

the only way it affects power steering and alternator is by turning them less. if anything it's extending their lives.

there are a TON of rumors about this mod but very rarely, if ever, will you talk to someone that actually has it. i have spoken to people that have had one for years on a G35 with no problems.

you should always give your belts a quick check anyway. this pulley won't make you check it more frequently, though.

the manufacturers probably didn't put it in because they whad to be %100 sure that the alternator/power steering would run at their optimum levels. mine run fine, though. the UR crank pulley was designed to give performance without losing function.

questions answered?

What about the issue of voided warranty is something goes wrong? How does one deal with this?

What about the water pump--if it is turning less, how do you suppose this will affect cooling and longevity of your radiator? If the power steering pump is turning less, would that not make the steering wheeel harder to turn and thus, with a rack and pinion system, more wear and tear on the steering gear? Just a concern! What about the alternator not turning enough to charge the battery at the correct rate--do the owners of this system replace their batteries and alternators more often than with stock pulleys? Just wondering!

honestly, if you have this many concerns than i wouldn't bother getting it. you might be too worried about all of this stuff to enjoy it.

it turns all of the other pulleys just fine. my dealership sells and installs them and i don't think they'd do that if it caused problems. they're not in the business of spending money.

Unorthodox Racing sells lightweight non-underdrive pulleys.

I would go with these instead. All systems are run at full capacity and you still get up to ponies.

The full set puts you back around $380, but that's with no worries about undercharged electrical, lack of power steering, brake power, and clutch power.

Chad1200 and SentientbyDesign:

Thanks a million for your responses. I appreciate it! Take care!

chad1200 wrote:when you get a few hours of free time read this post i started in May 07.

zerothread?id=251971

short answers:i've heard of the wobble issue but never spoken to anyone that it has actually happened to. i've heard of some sort of balancer that "needs" to be installed to correct this but it does not need to be installed.

the only way it affects power steering and alternator is by turning them less. if anything it's extending their lives.

there are a TON of rumors about this mod but very rarely, if ever, will you talk to someone that actually has it. i have spoken to people that have had one for years on a G35 with no problems.

you should always give your belts a quick check anyway. this pulley won't make you check it more frequently, though.

the manufacturers probably didn't put it in because they whad to be %100 sure that the alternator/power steering would run at their optimum levels. mine run fine, though. the UR crank pulley was designed to give performance without losing function.

questions answered?

I'm with Chad - I love this mod. Beware - if you get this mod your mpg will go down because you will be hauling *** every where you go.

Jacko3 wrote:I also heard about the possible crank wobble and bushings wearing out. Any thruth to this? I also heard that it might affect the power steering pump and possibly the alternator Any truth to this? How long have those who have used the underdrive pulley been using it? I heard of a person who started having issues at 1.5 years of installing the pulleys. I also heard that installing the pulleys require more routine inspection of the belts and parts. Any truth to these assertions?

Why do the auto manufacturers not use these underdrive pulleys to begin with?

Many motors out there combine the harmonic balancer with the crank pulley. This piece essentially reduces some of the instantaneous peak loads placed on the crank when a cylinder fires (engines actually create pulses of torque as each cylinder fires).

I don't know if the G35's crank pulley incorporates a harmonic balancer as I haven't examined one up close. However, speculatively, at least for the manual transmission cars, there may be enough damping effect available in the dual-mass flywheel to negate the need for a more traditional harmonic dampener. But this is purely speculative on my part.

Any guess on how much this underdrives the Alternator??

I've been considering this mod, but with my stereo I'm a little shaky about it

tollboothwilley wrote:Any guess on how much this underdrives the Alternator??

I've been considering this mod, but with my stereo I'm a little shaky about it

I wouldn't recommend it. I have a large sub amp and I can actually feel the car slow down when the volume is turned up during peak bass hits. Unless you get an aftermarket alternator...

do they make any good aftermarket alternators?or would i have to get it rebuilt?

have considered that anyways as I'm pushing about 1200 W through each sub and 100W per 4 channels....

what do you think about the lightweight set mentioned?