UnderDrive Pulley pros/cons

[RocketMan]

I've been discussing underdrive pulleys with a few engineers at work and 2 of them in particular give very different opinions.

The first has machined his own pulleys and double anodized them for his audi. Says they are great, no problems.

The other says don't do it because the loss in power to the accessory belt will slow down the cooling system, the air conditioning will be sluggish and the steering won't respond as well. He also says that the additional HP going into the wheels will allow the engine to run hotter and since the 3400 has a reputation for head gasket failure he says I shouldn't be dicking around with the horsepower.

Granted there is some bias in these opinions but there are a lot of valid points as well. Who out there can share his/her experiences about the "CHANGES" that they have noticed after installing the pulley, not just in performance but in functionality of the accessories.

One thing i'd like to point out is that the underdrive pulley, is simply a transducer of sorts, dividing energy into different forms. It does not "add" anything but only relieves torque from the engine to the accessories so that it is available for the wheels. In a sense then it is incorrect to say that the engine runs hotter, I think, because it still produces the same net energy per unit time, but allocates more to the higher torque coupling on the shaft, being the wheels.

[slowbird]

I know a few people running them on their 3400's and 3.1L.

No issues I've heard regarding Charging or cooling issues.

Only flaw with the underdrive pulley is that there is no harmonic dampner on them.

[kickarsgrdam01]

there is some issues i have heard with it producing a little less electrical power...which would account for the slower steering response and bad air conditing...however the gain in throttle response is small. i have thought about doing this mod but have not since the cons seem to outweight the good

[slowbird]

Really!?!?

I have heard the exact opposite...that the lighter and smaller UD pulley has a good effect on performance and has little to no effect on electrical and cooling.

[eric99gt]

Only thing I really see wrong with the statements you received is the head gasket failure. That's not one of the GA's many problems lol. As for the actual effect. I would just go with a lightweight one. That way you stay away from underdriving the rest of the system and still sort of see an advantage.

[xonelith]

Here's a post I started with my comments on the underdrive pulley from FFP. I'd retype it, but I'm lazy...LOL (copied this from another post a month ago in this forum)

http://www.grandamgt.com/forum/showthread.php?t=56154

I've noticed zero loss in power to any of my accessories.

Slowbird. Not sure what you are referring to in the harmonic balancer. Not part of the crank pulley on the 3400. We do have a reluctor plate which affects the crank sensor, but you can move it from the stock pulley to the new one without issue.

[slowbird]

Slowbird. Not sure what you are referring to in the harmonic balancer. Not part of the crank pulley on the 3400. We do have a reluctor plate which affects the crank sensor, but you can move it from the stock pulley to the new one without issue. [/B]

The 3400's don't have the rubber peice in the Stock Crank Pulley?

I thought they did....I know the 3.1L motors do...

My bad.

[ntl5002]

From what I understand from FFP the power lose is very minimal it's only 0.10v, that's nothing. You can see anywhere from a 5-10 hp gain.

[RocketMan]

Its not so much the alternator I'm worried about.....just 3 hours ago i found out (from taking my car in for touch up work) that i have a coolant leak and the whole coolant system and manifold gaskets are being replaced and my sway bar and bushings are f***d. I'd be more concerned about inadequate water pump pressure causing the engine to overheat and blow the gaskets.

[Bjornboy81]

Originally posted by xonelith
Slowbird. Not sure what you are referring to in the harmonic balancer. Not part of the crank pulley on the 3400. We do have a reluctor plate which affects the crank sensor, but you can move it from the stock pulley to the new one without issue. :agree:

I love mine, and havn't had a problem with anything other than keeping my foot off the gas pedal :D

[xonelith]

Originally posted by RocketMan
Its not so much the alternator I'm worried about.....just 3 hours ago i found out (from taking my car in for touch up work) that i have a coolant leak and the whole coolant system and manifold gaskets are being replaced and my sway bar and bushings are f***d. I'd be more concerned about inadequate water pump pressure causing the engine to overheat and blow the gaskets.

I wouldn't worry about it. Put in a 180 tstat and the pulley and there shouldn't be a problem. Plus your replacing all the parts:)

[slowbird]

Yea...I can't wait for my warranty to finish so I can toss one on.

[NaturalKonc3pt]

I also have an underdrive pulley on my 3100. i noticed some power loss at idle. but when i switched to a smaller alternator pulley that got rid of the problem. as far as coolant and such the coolant flows slower through the block than normal allowing a longer heat transfer and i've actually seen a decrease in engine temp by maybe 10 degrees or so. but the throttle response and rpm revs with the pulley is awesome. much quicker rev ups and much quicker rev recovery. i personally like my UDP, so i would suggest it.

[sunfirejoe]

just installed mine, pulled a cranshaft postion sensor coed and cranshaft performance range any explanations running an 01 with a 3400 sfi

[Bjornboy81]

Your Crankshaft postition ring is not aligned properly. Is it missing bad?

You can either take it to a dealership and have them do a CASE learn (crankshaft variance relearn procedure) or you can pull the pulley off again and align it right. Make sure one of the "windows" on the ring, are aligned with the keyway.

[sunfirejoe]

how much will a case learn cost me, not its not missing at all, actually im loving i got installed today, and was out all night, pull way harder now, well a lto mroe noticable, revs way faster. umm def a good buy. i used a 2160mm belt and fit just purrfect

[Bjornboy81]

I'm not sure exactly, but some will do it for free...it takes like 5 minutes.

Yes, there is quite a difference with the UDP. You'll notice better gas milage, and smoother shifts too :)

[sunfirejoe]

man i love cept the sensor thign ahvent had time to get that fixed, hehehe,= but im pulling way ahrder, and yes gas is betetr when i keep my foot off the gas pedal, but snow is here so, ill eb tkaing her easy till monday mourning when im on snow tires, damn skates i have tires

[Bjornboy81]

...have you ever looked into getting a spell check....?


j/p around :) Ya it's a nice little mod.

[1992grandam]

Theres no need for a harmonic blancer on the 3100-3400 as they are both internally balanced. I had the 2.3 H.O crank pulley(~the same as an aftermarket one) on my old 2.4 and it helped quite a bit top end.

[slowbird]

Harmonic Dampener is what I was talking about. (Though I think I said balancer)

Yea...the crank is internally Balanced, but the Harmonic Dampener reduces the Vibrations from the Pistons and rods off the crank.

But many people are running their 3400's hard with the UD pullies so it's obviously not needed.

[Bjornboy81]

dampener...balancer...same thing. It cancels out harmonics...and it's all internal.

[slowbird]

Balancer is weighted on certain sides to balance out the rotating mass of the Crank

Dampener is a big rubber peice that absorbs alot of the "ringing" and vibration of the Crank and rods attached to the crank.
(apparently the 3400 dampener is almost non-existent so it's not important)

but there is a difference....silly.

[Bjornboy81]

Where is this "alleged" dampener located? (be specific because this is a new one) :)

[slowbird]

On other cars it's a rubber ring located on the Crank pulley...a large rubber peice attached to it.

I hear on the 3400 it's quite insignificant.

[RocketMan]

...damper :)

[Bjornboy81]

^lol...good call. You're right. :)

[KeWLKaT]

I've always been wary of adding an UD crank pulley to vehicles.

It depends on the conditions of it (speaking of the vehicle).

Even if your engine is internally balanced (which is apparently the case for the GA), the UD pulley, w/out the harmonic damper as opposed to the stock one, WILL cause extra harmonic vibrations to the crankshaft, and this is indisputable.

Now, the amplitude of those vibrations aren't that impressive on N/A applications that aren't far from the stock power output. Let's say... less than 5% on the furthest cylinder. No danger there.

The problem comes up when you have a boosted application. Since there is a lot of extra stress on the crankshaft, the vibrations will go up like crazy... And you will think everything is normal until the day that.. bang... there goes the crankshaft... there goes the timing... there goes your valve(s)... there goes the engine head. And I don't think that you domestic guys have cheap engines like our imports...

So, yeah, think twice before doing this upgrade.

[slowbird]

Though I'm not 100% sure...but the 3400 has a very insignificant damper to begin with.

[KeWLKaT]

Well, insignificant or not... It's there for a reason. If it wasn't needed, then they wouldn't have put one at all, you feel my flow?

But like I said, if you want to keep it N/A then go for it.

Anyhow, if you have boost, and will lose those 9whp out of the extra 100 that you gain, why would you care?

[RocketMan]

I don't have boost and likely won't be able to afford it so this is my proposed solution...but hearing all this about the damper scares me off a bit. I'm wondering if an UD pulley couldn't be jerry rigged to carry one.

[KeWLKaT]

IMO it would be possible but it is always dangerous to attempt that without machine help: the pulley should still be equally balanced throughout its entire circumference... like balanced tires. Or else, a bit of extra weight on one side will backfire at you by giving HUGE vibrations at the shaft. And boom-kaboom.

So, yeah, it would be possible, but only profitable if everything is well balanced.

[slowbird]

The FFP Pulley is proven to be quite good quality and worth the $$

[KeWLKaT]

Does it have a damper on it?

[slowbird]

No.

But the stock one doesn't really have one either.

[KeWLKaT]

Ah... Comes back to the point I made a few posts up LOL.

Anyhow. If you plan on staying N/A, good, go for it.
For instance, I had a Jspeed UD pulley on my car, but I recently put back the stock one for the turbo setup.

I do admit it is kind of useless having the lightweight acc. pulley without the UD one, but it's shiny and nice to look at LOL

[townie15]

I have a UDP on my 2.4 liter and I love it. It does sound a little bit louder tho.

[TulaneGT]

Pulley...make you sound louder???

I ordered one for my 3.4. It'll be in tomorrow. Don't know when I'll be able to get it on.

[KeWLKaT]

well, louder because your engine will rev more freely and with less initial load from the pulleys themselves.

[TulaneGT]

Hrm, I didn't realize there would be a noticeable increase in noise. Cool.

[Bjornboy81]

...I might be wrong, but I don't think it's a good think if it gets louder, espcially on an engine that is't internally balanced (the 2.4 I mean) :(

My 3.4 didn't get any louder, sorry to burst you bubble Kevin. :)

[TulaneGT]

Awww....next you're going to tell me there's no performance gains either...

[Bjornboy81]

sorry, man...no performance gains either.



=P Actually it's one of the best mods for the money on these engines...I love mine, better revs, good low end gain, smoother shifts...very nice mod :D

[TulaneGT]

Low end gain = sweet....but what about top end? Not as much there?

[Bjornboy81]

There is, but I also have exhaust and intake which really take over in the upper end, so I don't really know what the UDP is doing for me. It's not enough to be noticed with the other mods :)

[TulaneGT]

I also have exhaust and intake :)

[Bjornboy81]

Then you're money baby!!! :D

You'll like it.

[TulaneGT]

One question...did yours come with instructions? Or did you just go off the ones online?

[voyager]

my 3100 got louder too - because i used a gatorback belt
=)

it's actually better for the water pump to turn slower - they cavitate at high rpms ( the fluid is forced to the walls of the pump at high revolution, leaving a void in the center ). my motor runs cooler with the UDP.

my FFP pulley came with instructions which were identical to those posted at there website.

[Bjornboy81]

I actually used the Haynes manual :)

[TulaneGT]

Well, I think mine's going on today...looks like I'm probably going to get a shop to do the work for me. Living with my sister = no tools....

[slowbird]

Let us know how much you like it and what they charge you.

[Red99GT]

Yea, I'm curious myself...I'm thinking that it might be my next mod.

[RocketMan]

This is all out of my head so I can't say for certain but the UDP "should" give equal gains percentage-wise across the entire power band, since there is a constant power factor between the accessories and the wheels. ie. Whatever torque manifests itself at the shaft out, is always split proportionally beween the 2 sinks and that proportion never changes. HP gains will depend on torque, which depends on loading conditions so lower torque (like accelerating down a hill) will show the same % but lower HP gains (say 2 HP) whereas accelerating up a hill again has the same % but higher HP because more is used (say 7 HP). Its all a function of what the engine produces. And none of the gains are really gains at all since the energy is not surplus it is merely transfered from one form to another. Its as though, in a metaphoric way you are wiring your air conditioning, stereo and fluid pumps into the wheels to give them extra power.....ok stupid analogy but w/e :)

[Bjornboy81]

that does make sense, but the accesories draw different (and non linear) amounts of power through the rpm range. Take the alternator for example, it's going to require less power to spin it a higher rpms because it's producing more avalible current while the current draw on it is the same. Does that make any sense? I'm sorry I'm bad at typing out my ideas :(

[TulaneGT]

Well the shop was going to charge me just under $80 to put the new pulley in, but when they took it all apart and realized they had to pull the crank sensor ring out of the stock pulley, they wouldn't do it. Said they were afraid of bending the crank sensor ring. So they put the stock pulley back on and now I have a Service Engine Soon light...wonderful.

[Bjornboy81]

that ring is just metal, you can bend it and then bend it back, no biggy. I bent mine a little getting it out, but then straightend it out before I put it in the other one. Go to another shop.

As far as the SES light, they might have moved the orientation of the ring a little, and now it's "out of sync". After you get it replaced, you may have to get a Crank Position Variance Relearn procedure done.

Just do it yourself if you can...it's really not all that hard. Just rent the tools from Autozone or where ever...and get a Haynes manual. :)

[Bjornboy81]

BTW see what code the computer is throwing.

[TulaneGT]

I don't think I need the Haynes manual for this project...only thing I think I am unsure of is the torque specs for putting the new pulley back on. I think I am gonna try this at a friend's house. Only thing I should have to rent is the 3-finger puller. Freaking shop won't do it, I'll do it myself!

[Bjornboy81]

I can post what it is when I get home tonight. :)

[TulaneGT]

As far as those people who wanted to know how much a shop would charge to install it...if they will take the sensor ring out and not be a pansy about it, it's an hour job. So you bring the pulley and belt, and it should only cost you one hour's worth of labor.

[TulaneGT]

I'm about to start this job in an hour or so....anyone have those torque specs handy????? HELP!

[Bjornboy81]

76 ft-lbs...i hope it's not too late :(