Hey everyone, just had a quick question.

As much as I look into this, I can't understand why reputable tuners are offering these 2% reduction crank pulleys that will drive the components quicker than what they were designed to..
Why would you want the alternator and AC compressor to spin quicker than the speed that its supposed to??

Some believe that if installing a 2% crank in an engine that already has a 15% reduction pulley they end up with a 17% lol...

Not trying to sound like a smart a** or anything, I really just can't understand the benefit of having one installed without compromising reliability in some way or another..
Can someone break it down to me?

 

Because race car. Well, it does make everything turn quicker, including the s/c, so yeah, you do gain there as well. Personally, I'm not a fan of this, because like you've said, everything else spins faster as well. I'd rather jack the engine up again and change my 15% with a 17% rather than taking the risk to wear something else than the s/c faster (and since my alternator bearings died at 80000 miles with a stock crank pulley, I don't think it's a good idea).

 

Lol had the same alternator issue, it actually froze so bad that I fried my starter trying to start the engine. Had to replace both outside on my driveway in 20 degree weather...

Still looking for a solid answer to why go with the 2%....

 

My ca came with a 2% but I'll be swapping it out for a normal ( non oem) eventually

 

Should look into a Super Damper.

 

The only pros are that you get a ''17%'' out of a 15% pulley and remove a well known weak link of the Mini, which is the crappy oem crank pulley. To me, the con of wearing the alternator and a/c compressor faster is not worth it. If you want a 17%, buy a 17%.

 

I cant think of any pros associated with this pulley.. I dont want to install a 2%, I'm trying to figure out why they even make these pulleys.

I meant to put out there that 15% SC pulley together with a 2% crank does not result in a 17% total reduction.

I just want to know why they offer these as a performance upgrade when they clearly destroy the engine and components in a very short period of time.

 

do you have evidence that the accessories fail due to the 2%? not hear say or read on forum?

do you have pictures or evidence of a destroyed engine due to one ?

or did you just read that on a forum as well?

personal experience?

im not really disagreeing with you or agreeing with you im just playing devils advocate

no one has come forward with real evidence other than a reputable vendor saying they see engine with worn bearings they "think" was caused by the pulleys...with out any real pictures or evidence other than using their credible name to spread the news

and I have yet to read anyone having failing accessories due to one either

 

In a nutshell, 2% "Oversized" crank pulley is nothing more than an alternative to add more rpm to the S/C, the extra rpm on all the other components is really no more than running your engine 2% faster than normal, thats all. (So figure if your normal cruising rpm is 3000 , your "accessories" are running as if your engine was @ 3060 rpm) It's 2% not 200% (2x).

(To not pi** off the Mathletes out there, I realize that 2% over dimentionally doesn't translate exactly to the other components, but close enough for these purposes... )

 

No one mentionned failed engine. The debate about non-dampened and dampened crank pulleys has been going on for a really long time. From factory, most, if not all engines comes with dampers in the crank pulleys and there's a reason. Chances that you burn your bearings due to a solid crank pulley are really slim, but we all know that it will affect them in the long run, as minimal as it can be. You don't need to be an engineer to know that preventing vibrations from the pulley to be transmitted to the crank isn't a bad thing. On this matter, I prefer paying more for a dampened crank pulley, but that's my opinion, my engine and my money.

On the matter of the oversized crank pulley, it's a logical assumption that if accessories spins faster all the time, they will wear faster.

 

ATI makes a dampened 2% pulley, that's what I have along with a 15% pulley.
As mentioned the OEM pulley is a disaster waiting to strike!
I think I have the best of both worlds and not worried by a 2% increase on my AC (seldom used)/ alternator.

Da Ghost : If you drive in a spirited manner, your parts will spin faster and wear out quicker!

 

I have a buddy that had an 03 cobra for a few years.. the overdriven crank pullies are very common on those cars.

When we did the pulley swap on his car we used a modest upper(s/c) pulley size and a oversized lower. One of the most pain in the butt jobs on that car besides the crank pulley, was removing the alternator so we could put a slightly larger pulley on it to ensure it lived a regular life.

From my memory the larger(say 15% vs 17%) pulley on the s/c helps eliminate belt slip and allows you to use the stock tensioner with no problems. For some reason or another i seem to remember the undersized crank pulley benefited the torque curve in some way.

 

Why not?

Running a -15% and a +2% here. Over 312,000 miles and my alternator and AC are doing fine.

Nik

 

To me the accessories thing is a non-issue, like I said earlier, it's 2% additional rotation not 2x.
But to go back to the title of the thread, I can think of one situation where the 2% over crank pulley may be a "good" idea. Basiclly if you have to replace your pulley anyway and had been thinking about swapping your 15% or 17% pulley for the next step smaller, you'll end up with extra boost with no additional work (you're doing the crank pulley anyway) and no additional cost, except maybe a belt, but hell if the belts not new you'll want to do it anyway & a lot of times the additional 2% in diameter isn't enough to require a smaller belt anyway. And esp. if you're a JCW owner, considering the reputation of the JCW S/C pulley removal nightmares.

 

Light-weight or dampened crank pulley?

 

dampened

 

To be fair though I haven't had the +2 on the entire time. And I can't do the math to figure out how many extra rotations it would have been. But if neither the alternator or the AC unit has failed in 300+ k miles, (with or without the 2%) i don't think it really matters that much. I am pretty certain that I have driven at least 2% more than the majority of members here.

Nik

 

I actually thought about it for a sec and concluded that the accessories will spin at a higher speed when you rev your car anyway... So I guess that doesn't really make a difference..

For the guys who are running the 2%, did you notice a difference in idle soon after the install? Just curious..

 

It's not supposed to change the idle, the pulley is following whatever rpm the engine is going.

 

Right.. But the accessories aren't.
Plenty of parts out are not supposed to be doing what they're actually doing

 

Well, the idle is dictated by the ecu, so technically, the pulley won't change anything about it. The alternator won't charge more than usual since the regulator will keep it in the normal output.

 

No difference, there can't be, it only changes the rotation speed of accessories attached to the belt (AC compressor, alternator, supercharger, and water pump)

Nik

 

I went with a 2% ATI crank pulley to replace the failure prone OEM crank pulley. I have a JCW engine with 12% JCW S/C pulley so to me it made good sense to go with the 2% crank pulley when replacing the OEM pulley. I gained 0.5 to 1 psi in boost.
I have had no issues with the accessories.