Is it better to go with the underdrive pulley or the stock pulley for an engine that is only daily driven and also running a powered stereo system and fog lights, which put a strain on the battery and alternator? I have seen the claims in HP increase and honestly that isn't why I am thinking of doing it.
I am thinking of more of less stress on the engine since I don't drive on the freeway much and want to have the engine work less harder on my average commutes.

 

the underdrive pulley would be smaller then stock pulley and would require different belt but it takes away some power from your electronics and put it to the wheel this good for if you race and trying to get the most power from the car..

you can get either a NST pulley or Agency power pulley which is the same size as stock and you can use the stock belts you wont see as much power as you would the undedrive one but you will notcied a difference...in the accerlation and throttle response..which allows crankshaft to turn faster, in turn giving you the power you want. and still have the power to your system

 

Well said, but don't expect you can feel much different, there is a trade off, always!

 

There really are no trade offs for a UDP.
If you have a big system you might see things that were less evident before like dimming lights. You can fix the electrical issues or you can hide them with a pulley for the Alternator.
But the UDP is a mod that you will feel after the install. The engine revs easier and makes the driving alot smoother IMO.

I'm selling an NST UDP for the 08xB.

 

The only reason to change the pulley from OE is to try to improve performance. If that isn't your goal, then leave it alone. There are downsides to changing the pulley, and there's absolutely no point if your only concern is engine stress. Be assured, the engine is perfectly happy with the stock pulley.

 

And these downsides are what?

There is some power to be freed from UDP's but to say it is only a performance mod is incorrect. It also improves the drivability of the vehicle.
It is a good mod if you just want alittle more throttle response and power in the city.

 

The downside is a decided increase in NVH -- the reason Toyota went to the trouble of the more expensive to manufacture factory pulley.

In the very first post, the OP made clear his only consideration was engine stress, not performance. Therefore, the appropriate thing to do is try to answer his question as he framed it. And that's what I did, including the very genuine downside to installing a lightweight pulley -- many wouldn't care for that change -- most want smooth and quiet.

 

By the way, the stress placed on the engine associated with the pulley when compared to that associated with the flywheel and power train is negligable -- don't worry about it. The factory pulley was designed specifically for use with that engine, so if, as you say, you're not interested in playing with the car's performance, leave the pulley as is.

 

NVH? Yes I know what is means and I have installed alot of UDP's in my life and never felt any addition NVH from a UDP. You could install a UDP on most FWD cars and no one but the installer would know the difference.
That claim is laughable to say the least.
Is that a genuine downside...NO!

I agree I wouldn't put a UDP if I was only concerned with relieving stress on the engine.
But in a way that is exactly what a UDP does, lightens the rotating mass and makes it EASIER to turn. Less stress, yeah! Enough to argue about or to install one NO!

 

No trade-offs? You're trying to say less energy to the battery, and less output from every accessory driven by the belt isn't a trade-off? If there was no trade-off, the factory would have done it already -- it'd save them money. As said above, the primary value of UD lightweight pulleys is in the racing environment -- if purchasing for a DD, make sure you understand the very tangible downsides.

 

Complete and utter BS. The NVH increase on my car was very noticable, and to pretend it isn't is worse than laughable -- it's a lie. The engine noise was clearly louder both inside the vehicle and out. I installed my AP specifically for performance reasons and have since made other mods that have resulted in other aspects also becoming louder. But when I first installed that pulley (mod number one), I definitely had second thoughts simply due to the decided increase in engine noise. It took me a little while to get accustomed to it.

 

You make it seem that every factory part is perfect and can't be improved. Did you forget there is the aftermarket that does this year after year.

Does a UDP have any effects on a vehicle with a stock system NO! You act like there is not enough power to keep things going or safe and that is again false information that you are trying to pass.

Your grabbing at straws now. I agree with you that maybe a UDP is not what the OP needs since he is only looking to relieve stress. I feel there are more to a UDP than just that.

A UDP is not a race only part, it frees up HP/TQ and gives you better drivable. Every car I have installed a UDP from I4's to V8's have been daily drivers, some with power hungry systems to some with no system.

 

Please explain how the NVH is increased from a UDP. Sounds to me like it was installer error on something that is very hard to mess up....wrong belt? This is really the first that a UDP has been said to be loud. LOL

I have probally installed more udp's then many and NEVER had any increase in NVH's.

 

And under what conditions? How about stuck in freeway traffic with A/C and top optioned stereo playing waiting to see how long it takes to get moving again? How long is that U/D pulley going to prop everything up? Just because you've been rationalizing U/D pulley's to everybody you meet doesn't make your argument sound. The factory prefers to minimize customer issues following vehicle sale. Your preference seems to be to find ways to cause them!

 

OK, so you've just made clear you actually don't understand what an NVH pulley is or what it's for or how it works. As I said, mine is an AP, and I did my own install and so I have the direct personal before/after experience with my very own xB. And in case you don't recall, the OP is talking about a second generation xB, no other car.

PS. the engine is a noise source, an NVH pulley reduces transmission of that noise.

 

Let me clear a few things up. I had a 2008 xB that I installed and uninstalled a NST UDP when I traded it in.

Now if we were talking about a V8 then you might have a leg to stand, but many in-line 4's are internal balanced. There is little to no NVH from a UDP install unless there is something wrong. With as soft as the OEM mounts are it would cancel out any little if it was possible. The amount you are claiming is retarded. Either you are super sensitive or reaching for more straws to back up you ridiculous claims.

Your example on the freeway is ignorant. I had a 08 xB with a UDP, premium Pioneer stereo and an amp and sub. And while stuck in traffic with the A/C blasting there was no effects. ? How long does what take to get moving? WTF are you talking about?

I'm not try to tell everyone to get a UDP.
I just can't stand people spreading bad information.

 

For one thing I havent noticed any NVH from my underdrive pulley at all. I have a scan guage and with everything running possible I am still putting out 13.1 volts at idle (i dont have a system though). As far as the water pump, on a hot 90 degree day at idle the engine sits at 190-193 degrees while driving its 188-190. So thats fine. As far as air conditioning goes its fine, still better than my gfs 07 Mazda 3. I was worried about going with the underdrive pully cause of these reasons but my cousin talked me into it. I am glad I did. Hope this helps!

Chris

 

Fine guys,

It's ultimately up to the reader to decide what they want to do. You've provided your input and I've provided mine. I'm done and I wish every one well.

-- Trevor

 

Wow, I really opened a can with one question. I guess, part of my deal would be a small increase in performance as a bonus. I do plan an a couple other performance mods, like the CAI and a custom cat back exhaust. I guess, it would be good to know that I am one of those heavy footed drivers at times in daily traffic, but I have cut back since I went down in power from my Z4 to the XB. I was actually looking at doing the whole set of pulleys that NST offers, but I wasn't sure whether is was better to stick with stock diameter on the main drive pulley or to use the underdrive. From what I have read too, is that anything over 15% under driven will be bad for the electrical system and such. But the NST, if I remember right, is only about 10% under drive. And if changing the all three pulleys would make the car more drivable around the city, then that too is relieving some of the everyday stress of driving I imagine. And excuse my ignorance, but what is NVH? I read these post several times and couldn't figure it out and I am pretty mechanically inclined and pretty good at deciphering abbreviations. Thanks for all your feed back.

 

I wasn't going to respond any further to this thread, but you asked a very specific question and I'll reply:

NVH stands for Noise-Vibration-Harshness.

How you or anyone else responds to that is beyond my concern. Do what you will !