Mitsubishi 3000GT & Dodge Stealth Forum banner

1 - 11 of 11 Posts

·
Senior Member
Joined
·
3,802 Posts
Discussion Starter #1
And how much and where do I find them?
Player
 

·
Registered
Joined
·
3,053 Posts
Underdrive pulleys without harmonic balancer do kill the #1 bearing and are also not that good to the #2. There are no dyno sheets available and more than 4 hp isn't i nthe chart anyways.
 

·
Senior Member
Joined
·
3,802 Posts
Discussion Starter #3
What is the harmonic balancer?
Player
 

·
Registered
Joined
·
2,057 Posts
A Harmonic Balancer is the counter weight that is attached to the end of your crankshaft. It is used to equal out (balance) the weight of the pistons, rods and crank, so all the weight is not on just one end of the crank. It also helps to smooth out virbation, by offseting the weight on the other end of crankshaft.

Hope that helps,

Dave Best
3Si #62
 

·
Senior Member
Joined
·
3,802 Posts
Discussion Starter #5
So with a harmonic balancer I'll be alright? What kind of horse power gain are we talking?
Player--'92 3000GT Sl
 

·
Registered
Joined
·
1,496 Posts
Player, I think you missed the point. We are talking about a lot of money for few, if any hp (less than a k&n), and potential side effects (also including problems with insufficient battery charging if the alt. pulley is changed, or a hi-po stereo is in use). A fluidampr harmon. balancer itself is probably $300. +, then the pulley set, another $175? Could be $500. for at best, 5hp (bigger gains may have been made on older cars with less efficient multiple v-groove pulleys/belts). I dont think too many people can feel 5hp difference. Maybe for a highly competitive race car, but not worthwhile for the street.
 

·
Senior Member
Joined
·
3,802 Posts
Discussion Starter #7
Diablo,
Thank you for clearing that up. I guess I did miss the point. That's a lot of money! Thanks again,
Player
 

·
Registered
Joined
·
392 Posts
Player,

To clear things up.... From the factory there is a harmonic balancer built into the crankshaft pulley. When you replace this with the underdrive pulley you eliminate the balancer and risk wear of the bearings. Most domestic cars have the pulley bolt onto the balancer so when you put an underdrive pulley on the car you keep the existing balancer and do not run the risk of bearing wear.
I have tried underdrive pulleys on a corvette and did notice more power but the alternator did not charge at idle and lights would dim when at a stop light.
If we could change the alternator pulley and the power steering pulleys we could do the same thing without the risk of spun bearings. I don't know what this involves but it would seem like a safer option.
The fluid-dampner mentioned in an above post is a very nice design but I don't know if they have an application to fit our cars. Instead of using an elastomer ring like stock balancers, it uses a silicon fluid to dampen the vibrations. I have seen dyno results with show a gain just from switching balancers !!

Hope it helps,
Kevin
 

·
Just Bring It
Joined
·
2,835 Posts
Hey Roger, could you look into the validity of these claims by Unorthodox racing. I have the Underdrive Pulley, and love it. I am worried about this Harmonics thing though. What happens if the No 1 bearing goes bad?

This is off of the Unorthodox Website

The second function of late model crank pulleys is torsional damping. Torsional damping is necessary due to the excessive diameter and weight of the factory crank pulleys. The design of our underdrive crank pulleys eliminates the need for any torsional damping for two reasons. One, the diameter of our crank pulleys is smaller than the original designs, in almost all cases smaller even than the rubber torsional ring, therefore effectively reducing the force the accessories have on the crankshaft. Second and most importantly is that our pulleys are significantly lighter than their OEM counterparts (anywhere from 3 to 11 lbs.). This weight loss dramatically reduces the stress exerted upon the rotating assembly by the excessively heavy factory crank pulley.

Lastly is the misconception that the crank pulleys on these vehicles are harmonic dampers. A harmonic damper is a unit bolted to the crankshaft snout that is completely separate from the belt drive system. An engine that uses a harmonic damper has the accessory drive crank pulley bolted to it, they wholly are separate pieces that are attached to each other. Balance shafts, which are used by several manufacturers, are specifically designed to eliminate harmonic vibrations. None of the vehicles we manufacture pulleys for have harmonic dampers. It is important for owners who have engines that use balance shafts to understand that if they eliminate their balance shafts they must have their engines balanced to 0 grams if they plan to purchase or continue to use our crank pulleys.

Our pulleys are very close to perfectly balanced as 6061 is a very consistent material and the CNC machining process ensures that our pulleys are perfectly true. This balance shaft elimination is rare and only happens on a few models that are modified for racing only

Tuan Luu
1994 3000GT
 
I

·
Guest
Joined
·
0 Posts
I thought that bushar racing was making some underdrives w/ the harmonic balencer built in. Any one know what happend with that
 

·
Registered
Joined
·
3,053 Posts
First, reducing the weight at the crankshaft is a good thing as this will allow a better response. This is the most problem with larger engines like the older inline Mercedes I worked on. Reducing the mass helped to get faster rpm increase. Now on our cars this is NO problem at all as you all know how fast the beast travels through the power band. Also the accessoires do consume much, much lesser power than any domesic car like the LT1 (who is one of the worst besides the Fords)

Now the question is what do you like fro mthe underdrive pulley ? Every mod you buy and let install gives more power because it sits in the brain. This is simply a human factor. Putting a car onto a dyno and finding 5hp would be really good although this is within tolerances of the dyno anyways


Mitsu designed an engine that works good and tell my why they didn't put a simple aluminum underdrive pulley in it. The answer is, that the engine produces some harmonics on the crankshaft (very good explained in a post above) and we use a dampener pulley for this. This is due to the desing of teh engine as other cars like the inline 6 of the Supra has one or two compensation shafts a V6 normaly don't (the Northstar engine has more of them to reduce vibrations)

Nobody says that underdrive pulleys are any bad quality, and I myself would say that they are of very good quality ! But I hate to run into any danger of a crankshaft rebuild (especially as it is not controllable) for a gain that becomes negligible after Stage 2 (fuel upgrade) We are talking of a $3000 job for getting the engine repaired.

I know some have it installed and until now no one reported any problems. This is good and gives facts for the future. But I'd like to see the manufactures showing real number ... but of course they want to sell their products !

Yes, Buschur is making an underdrive pulley with harmonic balancer that also reduces the overall weight. This is a good solution and I can support it ... but $400 for 5hp ... not my preferred mod !
 
1 - 11 of 11 Posts
Top