What is the HP & TQ gain for Light weight underdrive pulley?
(Weight 70% lighter and diameter 15% smaller than stock 997TT pulley)
Would this affect the battery charge ampere from alternator?

 

None.

 

I was told up to 12 hp depending on mods ,but who knows .BBI has a new one coming out supposed to be even lighter than there previous one.

 

Okay, maybe not none, but pretty negligible.

https://www.6speedonline.com/forums/...ht-pulley.html

Specifically:

 

In addition to a few HP you get a great response feel. Like a light flywheel. Put it this way. Yes, Not much HP but any true race car has one and if you have heard for example a cup car or GT-3 RSR rev up thats a big part. Low mass moving parts. You IMO you will feel it.

 

Does this create any rattles similar to LWFW mods?

 

I have the 996Cup light weight pulley on my 3.8. It under drives your accessories by about 15%. There are no rattles, no downsides. Like Sam says, it's good stuff. I also have an RS LWFW and a GT3R crankshaft. Those two items make a big difference. Engine is very rev happy... The GT3R crank is about 10lbs lighter than the stock TT crank. With a LWFW you are going from a 28lb DMFW to a 10lbs LWFW which is a loss of 18lbs. Those two items play a huge part in making the engine rev quickly as you are reducing about +25lbs or rotating mass. With a light weight pulley, you are going from a stock pulley which weighs about 2lbs to a light weight one that's under a 1 lbs. Yes, it's a further reduction of rotating mass but a relatively minor one especially considering the small diameter of the pulley to begin with. It does reduce parasitic drag slightly from under driving the accessories but it's negligible compared to the effect you will get from a LWFW for example. Cup cars also have small diameter multi plate clutches which further reduce rotating inertia. Everything ads up.

One if the big benefits in the under drive pulley is the reduced wear and tear on the accessories like your PS pump if you frequently track your car where it sees a lot of continuous high revs.

 

When I had my 996T I couldn't believe how slow the car free revved like when you heel/toe! I felt for a car that cost almost 200K USD that was ridiculous, as a Golf revved more quicker and felt more "exotic" revving there!


I knew I had to deal with this and I did a GT3RS LWFW (with upgraded clutch). WOW what a difference , the engine revved like it should have. Touch the throttle and bang it is where you wanted it without effort when heal/toe. Felt and sounded like a super car instead of the lethargic almost having to floor the gas pedal to match at higher rpms etc. Minus the chatter and the more touchy clutch from the LWFW, it is a must have upgrade for a STREET car of this caliber/enjoyment.......


Or so I thought.


Fast forward to my 997T that I purchased. When test driving the car I noticed that this 997 revved ALMOST as quick as 996T with a LWFW. I asked the sale person if it had and he said no. Sure enough it didn't have a LWFW, but it had a EVOMS LW Under drive pulley, 82mm GT3 throttle body, 82mm IPD plenum and Sprint Booster. After I got in contact with the original owner, he said he noticed the car revved a good bit quicker when he upgraded to the EVOMS LW crank pulley.


As my turbo package was being shipped from Protomotive (purchased it the day I bought the car...lol) I knew I needed to upgrade the clutch for the power. I upgraded to a ERP TRIPLE clutch with their LWFW option (the whole assembly and clutchs only weights 22lbs) & the car revved like a super bike quick!!


I would say if your car is mostly for the street I would definitely do the LW crank pulley, some of the above list of mods and not do the LWFW. If I had to redo it over again FOR A STREET CAR, I would not of added the LWFW, but instead kept the Sprint Booster (as I sold it as it was way to much with the LWFW) and the free-er revving mods my car came with already. I just had to adjust my spring booster to a little more aggressive setting and ALMOST have the quick response as the LWFW with out all the compromises of one.


With the LW crank pulley you would feel the difference with the way the car revs and it response with out a doubt.


I know I said a lot regarding a simple question, but I was very passionate about a couple of details with my car as a complete exotic PACKAGE and one of those things was a free revving engine (that equalled the legend of the Mezger name) and the way the car sounded which was top of my list (Speedtech 3" Catless race X exhaust)!