Underdrive pulleys [ merged 1/6/07]

[larryd]

Worth it or not? I'm thinking of going with the AEM tru-power pulley kit. Anyone used them?

 

[doug]

I'm one of the "Solid, hasn't caused any problems" guys. I like mine so far.

BTW, I think your poll is fundamentally flawed since there's not enough choices. The only choice for people with the stock pulley who have had no problems is coupled with the assumption "will not buy a solid piece." Maybe a lot of people with stock pulleys would buy a solid pulley some day, but there's no way to vote for that.

Also, don't buy the MachV pulley for looks-- you won't actually be able to see it much after it's installed. Don't expect any very noticeable performance gains either-- I didn't really see any. Don't get me wrong, though-- I'm still glad I got one. Like you mentioned, I'm concerned about the stocker separating.

 

[DSMu4ia]

If you insist on running one of those crank breaking, rod bearing spinning things, at least get it balanced.

Otherwise, stick to the 2g balancer, or one of the "legal" ones by Buschur/FP.

 

[Tom Sawyer]

Mine broke, got the new updated OEM pulley that supposedly won't have the same problem. I'm not getting rid of the harmonic dampener on a 7-bolt that has treated me well thus far.

Tom

 

[interceptor]

Do i really need the puller to be able to pull of the UDP or not ?
Can i just use a socket wrench ? need some help here ....!!!

 

[RSTsoon]

you might break it...

 

[interceptor]

Thanx Any one else ????

 

[luvrandfighter]

if you put it on and your car ideals at 3g's and you cant steer. you pu it on backwards. but i have it on my car "right" and i like it. like every other mod though, it takes a bit to get used to. at least for me. and i'll post my track time after i go on friday. a before pulley and after.

 

[interceptor]

Hey did you do it your self.What did you use to take it off ?
Do you feel the difference or not ?

 

[taloniized]

Does anyone know the tension for the belts? I've heard some people's belts have been sqeaking after installing this pulley.

 

[green95hrcgs]

I would imagine that the tension would be the same. A lot of the time, when you install the pulley with the new belts, the belts will stretch a little and require a re-tighten. I know mine did. It's perfectly normal. Mine doesnt squeak at all now.

 

[iwishiwascool]

Originally posted by Silent2g
i was told this years ago about underdrives

you spin the accessories slower, inturn to spin the water pump slower. which leads to running hotter.

this is very bad on turbo cars. or any forced inducted car.

Way dead thread but I wanted to dispense some misinformation

aka. I stand Corrected......

 

[workin_on_it]

so if you are building up your bottom end and you have your ratating assembly balanced, could you use one of these safely? doesn't the balancer compensate for imperfections on the crank, pistons etc.?
lighter pulleys is like a lightened flywheel....easier for the engine to rev.
the pulleys also underdrive the accessories(make them spin slower than neccisary) which also lets them spin easier.
i would rather get a lighter flywheel than a lightened crank pulley...you can drop more pounds of rotating mass easier with a fly wheel and accesery pulleys.
there have been cases where the rubber damper in the crank pulley seperates from the crankshaft....causing some serious damage!

 

[born4music04]

A good time to replace your pulleys is if and when your remove your AC. Then your dont have to buy an extra pulley. Good luck.

 

[GRNDSM]

>Way dead thread

Perhaps you should have kept it that way…

>The crank pulley does not turn the water pump It is run directly off the crank sprocket within the front cover.

WHAT? What engines are you talking about here? Certainly NOT 4G63… In our engine's water pump IS driven by an alternator belt, which is driven by a main accessory pulley (the one that gets “underdriven”).

>This is not one of the reasons not to get a solid pulley, and the others arent going to stop me either.

There are MANY reasons not to use underdrive pulleys. Now, you might think that extra 3-5hp is worth all the risk. Or that the fact that factory pulley can separate is more dangerous than ruined engine bearing. Fine, that is up to you, but there are definitely reasons not to use them…

Leon
RR

 

[iwishiwascool]

I stand corrected. WP is off the CP

However.

You dont suppose my experience last week having my crank pulley seperate.... while starting the car, causing the belts to jump, ac being tangled in the crank sprocket, causing the timing belt to jump and bending 16 valves... might influence my decision, do ya?

Ill edit the above as not to contribute to the misinformation

 

[GRNDSM]

>You dont suppose my experience last week having my crank pulley seperate....
>while starting the car, causing the belts to jump, ac being tangled in the crank
>sprocket, causing the timing belt to jump and bending 16 valves... might
>influence my decision, do ya?

I am sure that it had some influence . But you make an excellent case to replace an old stock pulley, it's just that, I prefer to replace it with a new stock unit .

Leon
RR

 

[Cirus_93TSI]

lets think about this logicly, think about the math here
no matter how small u make the pullys they will spin the same speed as long as every pully is made the same ammount smaller(based on the size ratio), for example if all ur pullys were 5" and ur changed them all to 3" it would be the same, the power increase is from having less roataing weight because the pullys are supposed to be lighter then stock
things get messed up when the pullys are reuced by sizes that are not uniform, if u make the crank pully smaller and leave the others the same(stock) size it will make them rotate slower, if u leave the crank pully stock size and make the other pullys smaller they will spin the accesiroes faster, getting only a crank pully can cause problems because of this, u should get a whole set all at once
hope u can all understand the concept in getting at here, speed is determined by the difference between the sizes of the different pullys, not the size of all the pullys in general

 

[doug]

Originally posted by iwishiwascool
You dont suppose my experience last week having my crank pulley seperate.... while starting the car, causing the belts to jump, ac being tangled in the crank sprocket, causing the timing belt to jump and bending 16 valves... might influence my decision, do ya?

Much concern over the same possibility is what led me to use a one-piece pulley myself. I'm well aware of Leon's differing opinion, as we have discussed this in several other threads, but I still am glad I went with the solid pulley. Leon is The Man, though, and I wish I were a tenth as smart about DSMs as he is-- this pulley thing may still come around to bite me. But not yet.

 

[doug]

Originally posted by Cirus_93TSI
the power increase is from having less roataing weight because the pullys are supposed to be lighter then stock

But a power increase should not be the reason for anybody to go with an underdrive pulley-- whatever increase there is (if any) is pretty much imperceptible. At least it was on my car. Maybe a whole set would be a bit more noticeable, but I would doubt it.

 

[Cirus_93TSI]

i never said it would make a noticable ammount of power, or be worth the money the pulleys cost, i was just pointing out how they really worked, and that only getting a crank pully could mess up ur accesory speeds if isnt the exact same size as the stock one
buying and installing a complete set of unorthadox pulleys will make a power increase because every pulley will be smaller and lighter, but unless ur really working hard to get that extra 5 to 10 hp it really isnt worth it, for a track car it might be but not really for a daily driver

 

[doug]

Originally posted by Cirus_93TSI
i never said it would make a noticable ammount of power, or be worth the money the pulleys cost, i was just pointing out how they really worked,

You're right-- and I didn't mean to make it look like I was arguing with you. I was just speaking in general terms, not a direct rebuttal to your post-- sorry about that.

 

[loreak]

if you replaced all of them you shave alot of weight, like 5lbs just for the crank pulley, add the difference in the rest, thats like taking balance shafts out as far as rotating mass

machv has a kit that is very cheap compared to most, like unorthodox, they are expensive, u can buy a whole 3 piece kit for the same price as the UD unorthodox pulley

 

[VASKO[BG]]

Ok now Underdrive puley is just one expensive acssesoary.
They will never work better then stock ones for sure.If they were better the company woul have them made lightened instead of have as they are now.If u want to have the same efect and not worry for noting do as I did.I just took away my AC belt so Im geting the same efect and to be honest it doesnt realy feels any diference then befor with the AC belt on.
If u realy wana feel the diference I ll tell ya what to do remove ur Power stering belt too then u ll realy feel it with out 2 belts but u also have to have a strong arms
I have seen several DYNO tests for underdrive puleys and to be hones the hihgest gain was 2 HP the lowest was -1HP for 500$ NO TX.

 

[GRNDSM]

Anyone getting one of those pulleys because they are lighter is wasting their money! The weight savings are very small and they happen at a very small radius to be significant. Reducing flywheel weight will be much more significant (not that I am a big fan of that ether). The main benefit of those pulleys comes from the "underdrive" feature.

How much extra power do you get from those? Most cars will be at 2-5hp. On some rare occasions, they have gotten as much at 10hp from a couple of different cars. That is where claim of "up to 10hp" comes from.

I can see 5hp being something noteworthy on a 100hp Honda (those guys must nickel and dime any mod they can find for a combined hp improvement effect), but on a 300-400hp DSM it not something even worth talking about. Unfortunately too many people see this mod hyped up in the Honda world and keep bringing it up...

And then, of course, there is the harmonics issue...

Leon
RR

 

[loreak]

ok to the guy who said his crank pulley separated and the ac belt got into the crank sprocket and messed up his timing belt, i aint buying it, your full of shit

the only way that could happen is if you dont have your timing belt cover on, and if you dont have it on then thats pretty damn stupid and your asking for trouble