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Discussion Starter #1
I am going to have a set of Unorthodox lightweight pulleys fitted this week but I am unsure whether to replace the crank pulley as well. I've read articles saying this could create problems, whereas Unorthodox says I should not worry.
Please bear in mind I have an Unorthodox lightweight flywheel as well.
I would like to hear some opinions in favor and against fitting a lightweight crank pully.

Flavio


P.S. How many hours would a competent mechanic need to replace all the pulleys?
 
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DT just went through this with his single car. He had the underdrive pulleys and the lightweight flywheel.

I forget exactly what drive-line component was chronically failing (I think it was a clutch component), but his mechanic traced it to the interaction of the two lightweight items. He said that this combo provided insufficient harmonic dampening causing premature wear.

I've heard of similar stories. I personally would never consider the pulleys. Too much risk for very little gain.

Greg
 

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The way I see it if everyone who put underdrive crank pulleys on their car had massive engine problems no one would sell them. Think lawsuit. Remember they sell underdrive crank pulleys for almost every car on the market. Maybe v8killer knows something.
 

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Discussion Starter #12
NakSuKow said:
The way I see it if everyone who put underdrive crank pulleys on their car had massive engine problems no one would sell them. Think lawsuit. Remember they sell underdrive crank pulleys for almost every car on the market. Maybe v8killer knows something.
Dusty sold them to me so he probably thinks they won't create problems.

Flavio
 

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>7) "Will the underdrive pulleys cause my engine to have >premature bearing wear ?"
>
>This is a fear many prospective owners have and it is a valid >concern since we are dealing directly with the rotating >assembly. It is, however, a fear with no basis in fact. Today's >modern small displacement 4 and 6 cylinder engines do not >require harmonic dampers in the traditional sense.
>
>Due to the design of our pulleys, both the smaller diameter and >the significantly lighter weight, they are significantly better for >longevity of the rotating assembly of your engine. The pulleys >relieve unnecessary stresses inflicted upon your engine by the >larger and significantly heavier stock unit, which has more >harmful leverage upon the crank/eccentric shaft to which it is >affixed.

The links I just gave you are straight from Toyota and Dinan, who both use I6 engines. They indicate that harmonic dampeners ARE needed. I have heard that small displacement hondas do not have one though. How else do you explain the problems that auto Supra owners have had with bolts rattling loose using a lightweight pully?

>Torsional damping is necessary due to the excessive diameter >and weight of the factory crank pulleys

Riiiight. Unorthodox is saying that dampeners are needed to dampen themselves? How does a balanced rotating mass produce torsional vibration exactly?

Someone from unorthodox came on the MKIV list a while ago to defend their product. When confronted with the information in the two links I gave you, they flamed a few people and left, offering no real logic behind their reasoning.

I have no idea how long it would take for the thing to damage your engine. Might take 80,000 miles, or only at a certain RPM, but Toyota designs cars to last longer than that, and they have dampened crank pullies for a reason.....
 

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Howdy Folks -

Greg sent me an email that the Pulley issue had come up again on the forums, and I'd thought I would add my $0.02.

I have a 94 6-Speed, T04R setup, with all the usual suspects. To make sure I covered every possible upgrade avenue I went with a complete set of Unorthodox Pulleys (uncluding the replacement crank pulley). I chose to go with a TRD Twin Disk setup as part of the buildup, which includes a lightened flywheel. During a dyno session the *pressure plate* came apart - the rivets that hold the assembly together were pulled and twisted, and one actually got ripped out. Of course the normal stress element of a clutch is going to be the friction surfaces, the flywheel and disk so this was pretty odd - we assumed a faulty clutch from Toyota. Round 2: a new clutch, this time a Stage III RPS setup, sprung, with the Mueller lightened flywheel. Again, a few 100 miles put on the car for some break-in - car pulls fine - go to a _different_ dyno - BOOM, same problem - the PRESSURE PLATE comes apart the same way - like someone took the front and back plates and tried to twist them apart like an Oreo cookie!

Now we HAVE to figure that two clutches did not fail to do manufacturing defects in the same way - so we turned to debugging the problem that must have been resulting from the car. At one point we wondered if the motor had enough lost tolerance in the crank/bearings to cause a cavitation/vibration in the clutch assembly to cause the failure. Of course, that could have been a costly (well, premature since I am building a motor :D) repair - and who knows, maybe the engine does have slightly out of spec tolerances that contributed to the problem - don't know, it has about 50K miles - but seems to run strong and shows no signs of leakage from the main seals.

OK, so as part of trying to get a solid answer before I dropped $3K on a new small block and installation, I put in a call to Rob Smith at RPS (used to work with Nissan's GTP team, FYI) and to Larry P at Sound Performance - both of who, IMHO, have a pretty established level of expertise in both Supras and drivetrains/clutches. As soon as Rob found out I was running an aftermarket crank pulley (without a harmonic dampener) he ID'ed it as the culprit - said that the combination of a lightened flywheel AND an undampened crank pulley can easily allow for VERY destructive vibrations to enter the crank, clutch (and related parts). He even suggested that I pull and cut open my oil filter to inspect for bearing shavings/particles to confirm no damage was done. Larry concurred about the crank pulley and said he didn't think to ask but was pretty confident that was the problem.

So off comes the Unorthodox crank pulley, on goes a new OEM Toyota part (about $225) my RPS clutch is put back together with a new pressure plate (I also got a new PP for the TRD setup which I'm keeping as a backup). Another few hunred miles are put on the car, and it then survives dozens of dyno pulls (on the original offending dyno!) and is still operating just fine with another 500+ miles, of which the last few hundred have been pretty abusive. I am still running the other pulleys in the kit.

For me, the bottom line is a *minimal* HP increase vs. possible damage to expensive clutch parts and/or (even worse) damage to the bottom end - is 8-10HP worth a $2500 bottom end? Also, when you get to single level, the extra HP is really inconsequential - does 600RWHP vs. 608 really mean anything? Hell, I partially did it for cosmetic reasons, so the performance add was not an issue at all. Grant has already referenced the articles by Rod and at the Dinan site - I tend to put more credibility in independent sources than the manufacturers claims.

Keep in mind: I have a ~650+HP car, with a G-Force ECU that raises the rev limiter to 7800RPM. Also of note, is the damage occured each time on the dyno (though two different models), so there could be something to the harmonics produced on a dyno vs. the street. There are certainly 6-speed owners with the full pulley sets who have not had any problems, but it's really in the specifics - Rob was very confident about the crank pulley, and it was replaced and the problem was solved - so there was *absolutely* something about my setup and the aftermarket pulley.

Hope this helps - this is just my obervations, things I was told by people I consider to have significant expertise about the problem, and the fix that ultimately resolved my problem.

Take care (and good luck to all the pulley users!)
 

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Discussion Starter #16
Hi DT,

Thanks for the explanation. I bought my pulley set mainly for cosmetic reasons. If I understand you correctly the real danger is combining a lightweight crank pulley with a lightweight flywheel. Did you leave on the other lightweight pulleys or did you turn them all back to stock?
If I replace all pulleys except the crank pulley would I still need the longer (Gates) belt or should I use the stock one?

Flavio
 

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Flav -

I'm still running the other pulleys, which are normally the power steering, waterpump and alternator - I am not running the alternator since I'm also running an upgraded 175amp Alt and there was some question about using a different pulley (though the diameters are the same I believe).

My belt is currently a Toyota part #90916 which I'm pretty sure is a stock belt - and it is obviously not the Gate part that's usually used with pulley set.

BTW, your car looks great - I love the euro spec hood (though I guess it's the "native" style in your neck of the woods!)

Take care -

DT
 

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Discussion Starter #19
I'm going back to a stock flywheel (with WOTM clutch), would it be advisable to keep the original crank pulley still or would the combination of stock flywheel and lightened crank pulley still provide enough dampening?

I already have the parts so it's a bit of a waste to not fit them I think but I am a little afraid of damaging the engine/drivetrain.

Flavio
 
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My opinoin you have probably guessed:

Hell no! :)

It is not worth the risk. The gain is little to nothing.

Flavio said:
I'm going back to a stock flywheel (with WOTM clutch), would it be advisable to keep the original crank pulley still or would the combination of stock flywheel and lightened crank pulley still provide enough dampening?

I already have the parts so it's a bit of a waste to not fit them I think but I am a little afraid of damaging the engine/drivetrain.

Flavio
 
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