Pulley kit have any downsides? Or stick to crank

[ramiram1984]

^^^ in that case, not sure why he's even asking if: when he had the light pulley ON before it was totaled and he could "FEEL" the power change/response, whatever, then why not install a pulley again, or 2 or 3...

hes pretty much answering his own question.

[danthedirt]

Proud owner of the Perrin lw crank pulley and a butt dyno. Def have to say that the butt dyno can feel a difference with the LW pulley. I find it most noticeable when you have to rev match, with the OEM pulley i'd have to give it 2 quick blips, with the lw pulley one good blip is all I need. I had to swap it back to stock to take it into the dealer and I can honestly say I the feel of the Perrin.

[JDKane527]

I have GFB lw crank, alternator, and waterpump pulleys, as well as Raceseng idlers. I didn't notice a difference when I installed idlers on, except for rpms dropping faster. Blips are quicker. Regarding acceleration, I didn't notice as big of an improvement as when I got header and tune. I still have stock flywheel and steel drive shaft, so it will be more noticeable after lightening those.

My butt dyno was recently calibrated to Mil Spec.

Edit: seems like some people's sarcasm detectors need recalibration.

[stugray]

Originally Posted by Readytoxplod

"weighs just 1.2 lbs, 3.7 pounds lighter than the stock OEM crank pulley. This reduction in weight from the crank shaft is equal to removing more than 100 lbs of vehicle weight"

Sounds like more than one kind of "Butt" Going on with that statement.

I guess "physics" doesnt apply to HP measurements.

[stugray]

Originally Posted by Readytoxplod

Do you happen to own one Stugray?

No and I dont own any of that magic magnetic jewelry that cures everything either... Point?

Show me just ONE dyno run with JUST the pulley change.
Even if you see a difference it is within the margin of error of dyno runs back-to-back

[finch1750]

Originally Posted by Clipdat

I'm not sure any of these replies are even on topic. The OP is asking if there is any disadvantage/negative effects of going with a full pulley kit like the Raceseng kit (idler, water pump, etc), versus just switching out the crank pulley only.

Everyone needs to stop debating the effectiveness or value of simply replacing the crank pulley.

He did say "In theory the lighter the better, right?". So theory got brought up. Then it went frm there like all threads. Lol

But you are right. OP, there is no negative that would occure from replacing the other pulleys, as it would in fact lower the mass. Can you notice it, maybe, maybe not. But they look nice and sure dont hurt.

Fwiw I do own a crank pulley. Its cheap and easy to install so any change is good enough for me at the price.

[OICU812]

It's been well discussed what these kits do. Do they show more HP on a dyno?=no.

Do they improve throttle response = yes.

Are they harmful= no. This has been well debated and documented here on several other threads and discussed by folks who understand this motors design far better then myself or anyone else in this discussion.

That said I'm an engineer however personally I feel that's a terrible card to pull in conversations I see it as abit of a "listen to be because I'm superior" kinda comment. Now if someone that was a engineer for Subaru/Toyota comes on this board and had specific dealings with the design of this engine and the dynamics "YES" I will listen and respect all of what they had to say on "this" topic. Being an engineer doesn't make anyone brilliant, there are hundreds/thousands of disciplines of engineering. I'm a process engineer for example and my knowledge in this topic is limited other then my mechanical engineering in younger years.

That said I have the raceseng kit, downshifts match up better and throttle response was definetly noticeable. Others that drive my car noticed immediately and I purposely didn't tell them.

Each to their own.

[Readytoxplod]

Originally Posted by stugray

No and I dont own any of that magic magnetic jewelry that cures everything either... Point?

Show me just ONE dyno run with JUST the pulley change.
Even if you see a difference it is within the margin of error of dyno runs back-to-back

Someone's a smart-ass! I asked because if ya don't own one, why do you put your 2 cents in when you don't have experience with one first hand?
Thanks guys, case closed. Respect and thanks to those intelligent enough to stay on topic OICU812, Finch 1750, Danthedirt, and JDKane527.

[mike the snake]

If you REALLY wanted to reduce rotating mass, you'd install a cam chain drive sprocket that's 1/2 as big so it spun the timing chain 1/2 as fast! LOL

[stugray]

It is simple. It is called physics.

If I simplify the problem enough it is more than obvious.

If you assume that JUST the rotating mass of the Pulley, crank, flywheel - Nothing else, it comes to approximately:
Pulley, crank, flywheel/clutch/pp (this is the rotating mass that is balanced)
4.9lb + 25lb + 30 lb

total rotating mass (NOT counting pistons or rods) = ~60lbs.
If you change the pulley to the perrin: "weighs just 1.2 lbs, 3.7 pounds lighter than the stock OEM crank pulley"
You just reduced the rotating mass by 4% ASSUMING that all the rotating mass of the crank and the flywheel assembly is the same diameter as the pulley!
It is really less than 1%!

The real answer is that changing the pulley rotating mass cannot reduce the rotational inertia of the entire engine assembly by even 1/10 of 1% or .001

"Thanks guys, case closed."

BTW - I put this SH|T together and take it to my local machinist to have balanced. Any other smartasses on this thread done that lately?

[stugray]

Originally Posted by finch1750

He did say "In theory the lighter the better, right?". So theory got brought up. Then it went frm there like all threads. Lol.

Yes and that is why I stated that:

"IF you want to reduce the rotational inertia of the engine as a system, starting with the pulley is silly.
It has the lowest return on investment of almost any component being so close to the center of rotation."
and
"I would not mess with it UNLESS you are doing a dozen other things that would make a bigger difference."

BOTH of those statements were directly addressing the OPs original question.

[stugray]

Another "technical" point:

with a racing engine, anytime you change the: flywheel, pulley, crank, piston, piston pins or rods weights you need to have your rotating mass rebalanced dynamically.

Changing any dynamic balance part on a performance engine without knowing how it affects balance is not a good idea.

[zooki]

Originally Posted by stugray

Another "technical" point:

with a racing engine, anytime you change the: flywheel, pulley, crank, piston, piston pins or rods weights you need to have your rotating mass rebalanced dynamically.

Changing any dynamic balance part on a performance engine without knowing how it affects balance is not a good idea.

Will you please stop bringing logic & reason into Internet arguments? They have no place here. Obviously "butt dynos" are way better indicators of power than anything you could actually measure. And besides, if I spent money on one of these pulleys you're damn straight I would tell everybody it made a difference....LOL

[Seattle944t]

Originally Posted by fang_gt86

Good point. Wonder if it's just one of those really good theory but practically useless in functionality. Is there solid data showing engine rev responsiveness stock vs lightweight?

Yes, there is plenty of evidence. Dynos, etc. Here is a video showing the difference in responsiveness on an STi:
[ame="http://www.youtube.com/watch?v=e5VPh9LqjaI"]Worx Tuning Crank Pulley Install - YouTube[/ame]

Originally Posted by Readytoxplod

I had a Perrin crank pulley on my last FR-S (totalled by idiot), and it was one of the best mods I purchased (freed up engine, more responsive).
My question is whether I should stick with the Perrin crank pulley or buy a kit?(alternator etc.)Theoretically the lighter the better right?
I heard of problems starting with the full lightweight system, and wondered if anyone has first-hand experience?
My goals are to have a faster revving car, any hp or torque is welcomed.

There is no drawbacks of the alternator and water pump on the full pulley kit when they are just lighter. The problems on street cars and full pulley kits are when they are underdrive pulleys. The kits that I am familiar with for the BRZ/FR-S are all lightweight kits, not under drive.