does this work??

[subafan]

just saw this on ebay... does this thing work??

http://cgi.ebay.com/ebaymotors/ws/eB...tem=1870058051

[oab_au]

Originally posted by subafan
just saw this on ebay... does this thing work??

http://cgi.ebay.com/ebaymotors/ws/eB...tem=1870058051

It works to make money for the seller.

It wont make more HP.

It wont make more torque.

It wont give more MPG.

It will give less output from the alternator, less cooling from the. air con, less power steering assist.

It will coat the belts with aluminium, causing them to slip.

Worst of all it removes the harmonic balancer, that dampens the harmonics that act in the crankshaft, to prevent breakage.

It is a nice colour.

Harvey.

[sfsvx]

The seller is correct about one thing - removing weight can be advantageous. Unfortunately, as Harvey points out, there are disadvantages to doing it with aluminum underdrive pulleys.

I've seen a website selling aluminum pulleys for Subarus that reduce weight and aren't underdrive - if you're interested in trying that, you could search for it, or I could look back through my stuff and see if I could find the URL.

I don't think I'd ever put underdrive pulleys on a street car.

Several of my friends with WRXs, 2.5 RSs and one SVX have either a lightened pulley or a complete underdrive pulley on their cars. I haven't done it myself on my 2.5 because I already have a 9 lb flywheel. I don't think I should push my luck at increasing the engine vibration. But to answer some concerns.

Subarus are internally balanced. The crank pulley is not a balancer on Subaru engines. It does have a piece of rubber in it, but this is to soften vibrations, not provide harmonic balance.

None of my friends, and I can put you in touch with any of them if you want, has ever experienced a negative affect from the use of the underdrive pulley. These are street driven Subarus, and most of them are daily drivers.

A few manufacturers offer the underdrive pulley in a kit that comes with a smaller alternator pulley that can be put on just in case you do lose voltage. Again, no one I know has experieced this loss, but they are not running 500 watt stereo systems either.

As to the hp claims. I have seen dyno results showing a small increase (5 hp) on N/A cars. The biggest increase (14 hp) I have seen has been on a turbocharged car.

One of my friends claimed he got about 4 to 5 more mpg since he put it on, and he does get more mileage per tank than I do, but he no longer owns that car. He did get more mileage per tank than me, but this could have easily been driving styles.

[oab_au]

Gid'ay Kent, look mate do yourself a favour, go to the library and get out "THE HIGH-SPEED INTERNAL-COMBUSTION ENGINE" BY Sir Harry R. Ricardo, LL.D.,F.R.S.
Read chapter 13, MECHANICAL DESIGN-PART 2, PAGES 230 TO 240.

I think you will learn more from this, than from your ill informed friends.
Harvey.

I think it'd work. At least, it works in neons, I know that for a fact. Yes, it drives the alternator slower. Yes, it drives everything slower...but it does 'free up' a few horses. Is it worth it? Depends. When you're in a car that weighs 2400 and you make 5-8 more hp, I think so. When you're in a 3525 lb car with 230 hp, I don't think you'd even notice the additional hp.

- Ca$h

Was your neon 5spd or auto? I would think that it would make more difference in a 5spd, where you're using more of the rpm band. What an auto needs is something to increase the torque (turbo, blower, stroker crank).

CJ

[oab_au]

Originally posted by $VX
I think it'd work. At least, it works in neons, I know that for a fact. Yes, it drives the alternator slower. Yes, it drives everything slower...but it does 'free up' a few horses. Is it worth it? Depends. When you're in a car that weighs 2400 and you make 5-8 more hp, I think so. When you're in a 3525 lb car with 230 hp, I don't think you'd even notice the additional hp.

- Ca$h

I am always interested in the facts, so may be you can tell us how "it frees up a few horses"

To do this it either has to A; increase the pressure acting on the piston, Increase the area of the piston or increase the crank throw, to produce more torque.
OR
B; Sustain the volumetric efficiency to higher rpm. to make more HP.

Removing a few lbs on a 4" dia will reduce the mass that the crank has to accelerate. This has to be considered in context to the rest of the mass, torque converter, gear train. drive shafts, two diffs, 4 half shafts, 4 wheels disks tyres and finally a 3525 pound car.

I'll leave you to work out the percentage increase.

Underdrive pulleys were used when a 'worked' engines operating speed was increased eg: instead of peaking at 5000 it now peaks at 7000, this meant that the accessories ran too fast so an under drive pulley was used to slow the accessories down to their operating speed.

Unfortunately the uninformed see these items on race engines and without knowing what they do, they become a must have, along with big injectors, cold plugs, blow off valves, cone filters and high octane fuel.

There are plenty of vultures out there who don't mind using false advertising and downright lies to make a buck at your expense, and if they read this and don't like it, they can always sue me. I can back up what I say.

What do you say Robert.

Harvey.

An underdrive pulley can also "Free Up" more HP when some percentage of total HP is taken to drive accessories. By decreasing the diameter of the drive pulley, you effectively increase the gear-ratio of the pulley system, making it marginally easier to drive. This will likely have almost zero effect at low RPM but will increase some as RPM increases because the accessories aren't having to be accelerated as much as they used to be. The increases will be marginal, but when a motor is playing in the top half of the band, it can be perceived/measured. For our cars, I would think you might feel it rev to the red a little faster, but how much difference that makes is probably more a matter of perception than trap-speed.

CJ

[Landshark]

there is a nice website that has a How-To for pulley replacement (and brakes, timing belt, etc.) where the person gives their comments on the Unorthodox pulley. i believe they are a member on these forums. does anyone have the link?

[Beav]

I agree with Harvey, it's an expensive perception. Now if you were to remove a few pounds that would be a different story. However there's a downside to that too - when you take your foot off of the gas pedal the car slows much faster than it used to.

For those of you that want to say "It's my car, nothing bad will happen if I use it, so leave me alone" I have one point to offer. The reason the OE dampener has the rubber insert in the first place is not for balancing the engine. It's there to absorb shock from the belt driven accessories. When that a/c compressor kicks in it does so right now, that's a lot of shock to the system. If the rubber isn't present the compressor takes an additional beating and so does the belt. The crankshaft being a lot beefier probably is unaffected. When you crank the steering all the way to one side there's also a heckuva load imposed on the belt again.

Yeah, the effects probably won't show up immediately. But the 'fantastic power improvement' won't either.

I wasn't disagreeing with Harvey at all... I was simply pointing out a factor that was missing from his last response. He referenced generating more HP while I addressed reducing HP drain at the source. In any case, I think for our cars an underdrive pulley is pointless at best. Unless you plan to put in a 5 speed, strip out 1000+lbs, and compete with it.

Save your money for the tranny fund.

[Beav]

I didn't think you were disagreeing with anyone. Sometimes semantics get in the way of coming to the same conclusions. Harvey and I (and more than a few others, I'd suppose ) tend to see eye-to-eye on most issues, but occasionally we take different trains to arrive at the same destination.

Harvey-

While I don't mind explaining how they 'free up' a few hp, I don't appreciate you talking to me as if you know everything and that I'm some stupid riceboy punk, especially when it is you who is speaking in error. If you didn't mean to do so, nevermind, forget any of that; I might be feeling a bit defensive due to other members who are pretty closed minded in this fora. Anyway, back to the subject: I've SEEN dyno tests where a neon would pick up a FEW (5-8) horses with an underdrive pulley installed. The pulley does not 'make' horsepower... it merely frees a few up. The weight decrease in the pulley does not 'create' any hp, it merely gets rid of rotational mass, which will allow it to rev slightly quicker (would you notice? >shrug< No idea. I'm guessing not)....but the REAL benefit of UDPs is that they are a SMALLER DIAMETER. What does this mean? Alright. I want you take take a junk alternator and sit it on your desk. Rotate the alternator one rotation. Guess what? It took ENERGY to do so. It took POWER to rotate that alternator. Now, instead of rotating it an entire rotation, only rotate it 3/4s of the way. Guess which used less power? Exactly. An 'underdrive' pulley does just that, it underdrives all of the accessories- the alternator, the powersteering, the a/c compressor, and whatever else the belts go to. Because these things are spinning more SLOWLY, you are effectively 'moving' a few HP from the accessories to the crank, hence the GAIN in HP that is noticeable on smaller/lighter cars. In the SVX, I don't think it would be worth it at all, because at most you'd gain 8hp or so, and it wouldn't affect our power/weight ratio much at all.

Understand?

- Rob

[oab_au]

Originally posted by cjoffe
I wasn't disagreeing with Harvey at all... I was simply pointing out a factor that was missing from his last response. He referenced generating more HP while I addressed reducing HP drain at the source. In any case, I think for our cars an underdrive pulley is pointless at best. Unless you plan to put in a 5 speed, strip out 1000+lbs, and compete with it.

Save your money for the tranny fund.

Yes I see your point, though it would be better to turn off the air con, pull the plug on the alt, and keep the steering straight. This way the harmonic damper would be retained.

I am more concerned with the removal of this item and the effects that it has on torsional harmonics of the crankshaft in preventing fatigue fractures.

"The crankshaft of any engine has to be considered as a torsion bar, anchored at one end to a flywheel whose angular velocity is substantially constant and the other end free to oscillate. Under these conditions it is subject to a series of torsional impulses imposed by the pistons. At certain critical speeds the frequency of these impulses will coincide with some harmonics of the natural frequency of the crankshaft.
When this occurs the normal angular deflection of the shaft will be increased many times and if completely unchecked, would build up to such an amplitude as would result in the fracture of the shaft.

The harmonic damper has a small flywheel attached to the pulley by bonded rubber, this functions in part as a de-tuner, for as soon as any torsional vibration occurs, the attached mass tends to move in anti-phase, so opposing the building- up of the amplitude, while at the same time the, the spring rate of the attaching rubber increases with the amplitude of movement, thus altering the tuning of the system." ( Sir Harry Ricardo from the above reference.)

All this depends on the particular crankshaft, you can't compare a 2lt 4cyl to a 3.3lt 6. the harmonics are completely different.

'Puts the chalk away, cleans the blackboard and goes back to the corner.'

Harvey.