ClubWRX Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
85 Posts
Discussion Starter #1
I am looking to install the Cobb Leightweight Main Pulley on my 2011 WRX. I am looking for some insight...hopefully someone else has done this recently.

I am looking specifically for a couple tools that will take the main pulley off and that will put the timing belt back into place after installation. I watched a video on the installation of the Grimmspeed pulley and they use the tools below...

To take the pulley of the engine block


To put the timing belt back on


Does anyone know if these tools work for the Cobb pulley too? If so, where can I get them?

Any information or insight would be greatly appreciated!
 

·
Super Moderator (Actually a SuperSpy)
Joined
·
29,224 Posts
Wait, what pulley are we talking about that requires re-installation of the timing belt? I find this confusing. Why is the timing belt removed?
 

·
Gold Member
Joined
·
2,175 Posts
It's not the timing belt; it's the "accessory belt"?....you know, the front one. lol

OP - Can you send a link or something that shows why that first "tool" is needed. I think I remember it going like this - REMOVAL: Put the car in gear, get out the longest breaker bar you're got, good luck breaking the bolt loose, and fish out of there. REPLACEMENT: Find the hole, line it up with key/notch, torque new one down. As for the belt, instead of buying and using the tool from your second pic, we just cut and replaced the belt with a better "stretch" belt.
 

·
Registered
Joined
·
85 Posts
Discussion Starter #5
It's not the timing belt; it's the "accessory belt"?....you know, the front one. lol

OP - Can you send a link or something that shows why that first "tool" is needed. I think I remember it going like this - REMOVAL: Put the car in gear, get out the longest breaker bar you're got, good luck breaking the bolt loose, and fish out of there. REPLACEMENT: Find the hole, line it up with key/notch, torque new one down. As for the belt, instead of buying and using the tool from your second pic, we just cut and replaced the belt with a better "stretch" belt.
This video below is what I was watching for removal and installation
GrimmSpeed Subaru Lightweight Crank Pulley Install Video - YouTube

Now that you mention it, putting the car in gear is probably 100x easier. As for the belt...even if you cut the belt you would still need a way to put the new one on. Since a tensioner pulley doesn't exist on this car I have no other choice but to use the tool or chance breaking the belt putting it back on.
 

·
Registered
Joined
·
6,751 Posts
Lightweight pulleys are a total waste of time and money.

Return it and buy something useful with the money.
 

·
Gold Member
Joined
·
2,175 Posts
This video below is what I was watching for removal and installation
GrimmSpeed Subaru Lightweight Crank Pulley Install Video - YouTube

Now that you mention it, putting the car in gear is probably 100x easier. As for the belt...even if you cut the belt you would still need a way to put the new one on. Since a tensioner pulley doesn't exist on this car I have no other choice but to use the tool or chance breaking the belt putting it back on.
Exactly. That's why you may want that second tool I provided a link to. But I'm still not sure if it works for any pulley other than Grimmspeed, after reading the description. They are stretch belts, so 1) no tensioner and 2) they shouldn't break if stretched a bit.
 

·
The Fruit
Joined
·
4,728 Posts
I'm curious too as to why reducing rotational mass is a bad Idea?

The factory pulley weighs what 8lbs? Halving that should make a nice improvement pre-boost and for off throttle rpm drop.

Unless I'm missing some quirk of the car that causes a reduction in mass to be a bad thing? ..
 

·
Premium Member
Joined
·
4,376 Posts
I'm curious too as to why reducing rotational mass is a bad Idea?

The factory pulley weighs what 8lbs? Halving that should make a nice improvement pre-boost and for off throttle rpm drop.

Unless I'm missing some quirk of the car that causes a reduction in mass to be a bad thing? ..
Warning: No first hand experience. Just forum trolling education and a bit of intuition on my part.
-Side Note: Too much rotational mass reduction may throw issues. This can be achieved with a lighter flywheel in itself.
-Second hand observation: The pulley doesn't make a huge difference apparently... But yet the flywheel does.
-Intuition: With such a small diameter the rotational mass/inertial is fairly low due to the shorter lever arm. The flat out 4lb reduction causes nominal rotational inertia changes without the larger lever arm for the majority of the weight... as opposed to a lighter flywheel where there is a large portion of the weight at a longer lever arm.

That being said, its the same idea with a carbon fiber driveshaft from what I've read. Actually slows your revs down (adds rotational inertia), but is a lighter part (removes overall weight). I would infer that more of the weight is spread towards the surface of the driveshaft, than a traditional one that is uniformly weighted (in a radial sense from the center point outwards).

Physics nerds, comment as well. Chances are, my logic is pretty far off from the truth. I don't deal with mechanical stuff much - on the electrical side personally.
 

·
The Fruit
Joined
·
4,728 Posts
well no that makes sense that the flywheel reduction makes a bigger difference.. not only is it heavier to begin with its of a much larger diameter. I can def see why the shorter lever reference would make weight reduction less effective. But I'd think there should be some benefit. How much related to cost though.. that might be the question at hand. They're not hard to change (vs a flywheel) so if there is benefit to be had.. this would be an easy way to go about it.

How many are running them and what are the opinions?
 

·
Premium Member
Joined
·
4,376 Posts
well no that makes sense that the flywheel reduction makes a bigger difference.. not only is it heavier to begin with its of a much larger diameter. I can def see why the shorter lever reference would make weight reduction less effective. But I'd think there should be some benefit. How much related to cost though.. that might be the question at hand. They're not hard to change (vs a flywheel) so if there is benefit to be had.. this would be an easy way to go about it.

How many are running them and what are the opinions?
I think i noticed a positive change. it might all be in my head though.
Most people report noticing a difference that I've read. I think it's just the idea that you can skim the weight off using a lighter flywheel much easier.
 

·
The Fruit
Joined
·
4,728 Posts
effective maybe.. but definitely not easier. Installing a flywheel is quite a bit more involved ;) lol
 

·
Registered
Joined
·
1,393 Posts
The most help that a lighter pulley gives is when you rev-match for shifting... JMO
 

·
Premium Member
Joined
·
4,376 Posts
The most help that a lighter pulley gives is when you rev-match for shifting... JMO
To my understanding, it is a physically identical result as using a lighter flywheel. Normally, to a much smaller extent, however.
 

·
Premium Member
Joined
·
10,943 Posts
I'm curious too as to why reducing rotational mass is a bad Idea?

The factory pulley weighs what 8lbs? Halving that should make a nice improvement pre-boost and for off throttle rpm drop.

Unless I'm missing some quirk of the car that causes a reduction in mass to be a bad thing? ..


Reducing rotational mass isn't a bad thing, it's just that the pulley is the wrong place to be reducing that mass from. For one, the weight and rubber ring in the OEM pulley helps to reduce vibration in the crank shaft. Also, think of the crankshaft as being balanced front to back. If you remove weight from the front of it, then theoretically it will cause the crankshaft to push up on the bearings towards the front of the car and in turn push down on the bearings towards the rear. This will cause abnormal bearing wear (this is bad).


IMO, if you're wanting to reduce rotational mass the best place to start is the crank shaft itself. You can knife edge the crank, then install some light weight forged pistons and rods. This greatly improves engine response. Although you don't want to reduce too much weight or you will encounter drive-ability issues. The only material I've had removed from the crank was in balancing it (which it was surprisingly out of balance), that, along with CP pistons, Manley h-beam rods, and an ACT streetlight flywheel (13.9lbs) and I can honestly say I would not want to reduce the rotational mass of the engine any more. Throttle response is snappy, and rev matching is a breeze. Any less mass and the car would simply be difficult to drive.
 
1 - 18 of 18 Posts
Top