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-- 997 --
Barcelona


Joined: 11 Jun 2015
Posts: 1275



PostPosted: Sun May 19, 2019 1:39 pm    Post subject: 4" Underdrive Pulley ----------- Reply with quote

Hi, i have a 4" underdrive pulley and belt, i had it a very long while and as ive changed my AOS, new plenum and changed X2 idler pulleys i remembered i had this 4" underdrive pulley sitting around!!,

My question is what benefits are there in fitting this pulley?, and are there any noticeble difference? Also am guessing i would need need to buy a new crank pulley bolt cos onced used they stretch when torqued up??

Cheers

J
 



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Phil 997
Le Mans
Le Mans


Joined: 05 Dec 2015
Posts: 15570
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Sun May 19, 2019 2:20 pm    Post subject: Reply with quote

Jimi , when mine was fitted to my gen1 they used the same bolt so you may be lucky or belt and braces and go buy a new bolt.

there are no added BHP from this mod but what the theory is it redirects unused energy from components that have been engineered to have a supply of energy more than they need this is redirected to the rear wheels so has the effect of giving you a few BHP more power .

But for me a far bigger win from fitting this mod was that it made the power steering slightly heavier as we know the steering on the 997 is very light, in fact a bit too light for a sports car and making it a bit heavier really added to the confidence and control when driving . This plus isn't really widely talked about as a gain from this mod but for me it was better than the bit of extra power Thumb Thumb Thumb
_________________
911 Owners,Some Invest In The Future,
Others Enjoy The Moment Today.
 
  
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-- 997 --
Barcelona


Joined: 11 Jun 2015
Posts: 1275



PostPosted: Sun May 19, 2019 2:48 pm    Post subject: Reply with quote

Phil 997 wrote:
Jimi , when mine was fitted to my gen1 they used the same bolt so you may be lucky or belt and braces and go buy a new bolt.

there are no added BHP from this mod but what the theory is it redirects unused energy from components that have been engineered to have a supply of energy more than they need this is redirected to the rear wheels so has the effect of giving you a few BHP more power .

But for me a far bigger win from fitting this mod was that it made the power steering slightly heavier as we know the steering on the 997 is very light, in fact a bit too light for a sports car and making it a bit heavier really added to the confidence and control when driving . This plus isn't really widely talked about as a gain from this mod but for me it was better than the bit of extra power Thumb Thumb Thumb


Thanks for that phil, more clearer on understanding.. i agree for a performance car the steering ahould feel abit heavier!!

One other question, is the pulley connected to the damper? I.e. its 2 pieces that i have to take apart so that i fit the new 4" pulley to the damper then bolt up together? Cis me thinking that if theres no damper then ill be having major vibration running thru the car lol.

Cheers

J
 
  
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drmark
Monza


Joined: 07 Feb 2009
Posts: 152



PostPosted: Sun May 19, 2019 3:27 pm    Post subject: Reply with quote

-- 997 -- wrote:
Phil 997 wrote:
Jimi , when mine was fitted to my gen1 they used the same bolt so you may be lucky or belt and braces and go buy a new bolt.

there are no added BHP from this mod but what the theory is it redirects unused energy from components that have been engineered to have a supply of energy more than they need this is redirected to the rear wheels so has the effect of giving you a few BHP more power .

But for me a far bigger win from fitting this mod was that it made the power steering slightly heavier as we know the steering on the 997 is very light, in fact a bit too light for a sports car and making it a bit heavier really added to the confidence and control when driving . This plus isn't really widely talked about as a gain from this mod but for me it was better than the bit of extra power Thumb Thumb Thumb


Thanks for that phil, more clearer on understanding.. i agree for a performance car the steering ahould feel abit heavier!!

One other question, is the pulley connected to the damper? I.e. its 2 pieces that i have to take apart so that i fit the new 4" pulley to the damper then bolt up together? Cis me thinking that if theres no damper then ill be having major vibration running thru the car lol.

Cheers

J


Surprised you both feel that. One of the great characteristics of the 911 is steering feel and lightness due to it being rear engined. If you drive an early non assisted car, it is very light and sensitive at speed - and can feel everything perfectly. Assisted later cars have tried to replicate that, and while not perfect I think the helm is one of the best out there.
I guess if you are used to the likes of Audi / Merc / BMW is does feel light, but that’s good isn’t it? I use steering in lightest setting in my RS4, so the 997 has influenced my other cars, not vice versa. But good thing we are all different.
 
  
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MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7323
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Sun May 19, 2019 3:33 pm    Post subject: Reply with quote

What is the difference in ratio of circumference? Can you tell the difference in steering feel between 3rd and 5th at 50mph? That would make much more difference I suspect.

MC
 
  
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Phil 997
Le Mans
Le Mans


Joined: 05 Dec 2015
Posts: 15570
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Sun May 19, 2019 3:43 pm    Post subject: Reply with quote

drmark wrote:
-- 997 -- wrote:
Phil 997 wrote:
Jimi , when mine was fitted to my gen1 they used the same bolt so you may be lucky or belt and braces and go buy a new bolt.

there are no added BHP from this mod but what the theory is it redirects unused energy from components that have been engineered to have a supply of energy more than they need this is redirected to the rear wheels so has the effect of giving you a few BHP more power .

But for me a far bigger win from fitting this mod was that it made the power steering slightly heavier as we know the steering on the 997 is very light, in fact a bit too light for a sports car and making it a bit heavier really added to the confidence and control when driving . This plus isn't really widely talked about as a gain from this mod but for me it was better than the bit of extra power Thumb Thumb Thumb


Thanks for that phil, more clearer on understanding.. i agree for a performance car the steering ahould feel abit heavier!!

One other question, is the pulley connected to the damper? I.e. its 2 pieces that i have to take apart so that i fit the new 4" pulley to the damper then bolt up together? Cis me thinking that if theres no damper then ill be having major vibration running thru the car lol.

Cheers

J


Surprised you both feel that. One of the great characteristics of the 911 is steering feel and lightness due to it being rear engined. If you drive an early non assisted car, it is very light and sensitive at speed - and can feel everything perfectly. Assisted later cars have tried to replicate that, and while not perfect I think the helm is one of the best out there.
I guess if you are used to the likes of Audi / Merc / BMW is does feel light, but that’s good isn’t it? I use steering in lightest setting in my RS4, so the 997 has influenced my other cars, not vice versa. But good thing we are all different.


I must note its not significantly heavier just a little and IMO in a good way. but as you say different views and maybe different driving styles call for different steering feel .
_________________
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Others Enjoy The Moment Today.
 
  
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Phil 997
Le Mans
Le Mans


Joined: 05 Dec 2015
Posts: 15570
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Sun May 19, 2019 3:46 pm    Post subject: Reply with quote

-- 997 -- wrote:
Phil 997 wrote:
Jimi , when mine was fitted to my gen1 they used the same bolt so you may be lucky or belt and braces and go buy a new bolt.

there are no added BHP from this mod but what the theory is it redirects unused energy from components that have been engineered to have a supply of energy more than they need this is redirected to the rear wheels so has the effect of giving you a few BHP more power .

But for me a far bigger win from fitting this mod was that it made the power steering slightly heavier as we know the steering on the 997 is very light, in fact a bit too light for a sports car and making it a bit heavier really added to the confidence and control when driving . This plus isn't really widely talked about as a gain from this mod but for me it was better than the bit of extra power Thumb Thumb Thumb


Thanks for that phil, more clearer on understanding.. i agree for a performance car the steering ahould feel abit heavier!!

One other question, is the pulley connected to the damper? I.e. its 2 pieces that i have to take apart so that i fit the new 4" pulley to the damper then bolt up together? Cis me thinking that if theres no damper then ill be having major vibration running thru the car lol.

Cheers

J


Jimi , I cant help mate as I didn't do the job DIY, and got an indy to fit it. Thumb
_________________
911 Owners,Some Invest In The Future,
Others Enjoy The Moment Today.
 
  
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-- 997 --
Barcelona


Joined: 11 Jun 2015
Posts: 1275



PostPosted: Sun May 19, 2019 3:53 pm    Post subject: Reply with quote

Phil 997 wrote:
-- 997 -- wrote:
Phil 997 wrote:
Jimi , when mine was fitted to my gen1 they used the same bolt so you may be lucky or belt and braces and go buy a new bolt.

there are no added BHP from this mod but what the theory is it redirects unused energy from components that have been engineered to have a supply of energy more than they need this is redirected to the rear wheels so has the effect of giving you a few BHP more power .

But for me a far bigger win from fitting this mod was that it made the power steering slightly heavier as we know the steering on the 997 is very light, in fact a bit too light for a sports car and making it a bit heavier really added to the confidence and control when driving . This plus isn't really widely talked about as a gain from this mod but for me it was better than the bit of extra power Thumb Thumb Thumb


Thanks for that phil, more clearer on understanding.. i agree for a performance car the steering ahould feel abit heavier!!

One other question, is the pulley connected to the damper? I.e. its 2 pieces that i have to take apart so that i fit the new 4" pulley to the damper then bolt up together? Cis me thinking that if theres no damper then ill be having major vibration running thru the car lol.

Cheers

J


Jimi , I cant help mate as I didn't do the job DIY, and got an indy to fit it. Thumb


Aah ok phil, understood, ive added a picture of my pulley, hope someone on here could explain if the pulley is in 2 pieces etc, the main pulley and damper put together etc!!

Cheers phil, appreciated !! Thumb

J
 



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