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Underdrive pulley


Macca

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Is anyone running an underdrive pulley?

I am considering dropping the hammer on this (total911 mag promo $40 off) https://www.ebsracing.com/product/underdrive-pulley-and-belt-kit-986987996997-gen-1

There is a lot of feedback on the US forums,and a heap on the market - Flat 6, RSS, Tarett,BBI,TRS etc.  All in all the feedback is positive. For fitment you have to dremal (cut) some of the engine(boss).http://shop.tunersmotorsports.com/wp-content/uploads/2015/09/trs-underdrive-pulley-install.pdf

What are you thoughts please? 

http://pedrosgarage.com/Site_5/Cheap_horses!.html

 

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Hey Macca,

There are quite a few pros to getting an under drive pulley, just wondering what your main reasons are for the upgrade? Would you be installing it yourself?

As for a few other power upgrades you can look into a IPD plennum, exhaust, tune and also a light weight flywheel (that does come with some disadvantages though). Other than that I don't think there are too many other upgrades that come to mind

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Yes, it was to free up the AC strain on the engine (cheap HP).

Agreed - the plennums look attractive but to commit and fully extract power would need to further invest in a larger throttle body,tune, flywheel,exhaust system etc. This quickly adds up and it is soon approaching that ($) mark where of a couple more thousand outlay and the options of either S/C or Turbo bolt on (100+hp) arrive. It's a road that is tempting to walk down but am currently trying not to. I am happy with C2 but will be on the hunt for a turbo when finances permit. :) 

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I dont really find there are too many issues other than a slight chatter when in neutral. 

Internet hysteria has me believing it could possibly damage the crankshaft but for me it's the issue of it being difficult to drive. With a LWFW the revs drop rapidly during a gear change so you have to be on your game or you burn your clutch or thud the gearbox. 

Other than that it's actually an awesome modification! Power delivery is spot on. 

A under drive pulley is recommended when a LWFW is installed. If you can live with a bit of chatter it's one mod that actually makes a heap of positive difference and what feels like more power due to less rotating mass needing to be spun up. 

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Interesting, thank you for the honest and informative feedback.  

Youre welcome! 

The underdrive pulley requires less thought as it's a straight forward mod. The LWFW is riskier but has more reward! I'd recommend cargraphic for both. 

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  • 3 months later...

Installed the TRS underdrive pulley yesterday (Indie/mechanic did it) as I was a bit hesitant when the install requires holding crank timing and cutting metal in the engine bay etc. Its wet in Melbourne so I havent had a chance to properly stretch the legs however first impressions are that it does free up load and the car seems more peepy than before (most likely my imagination) but for certain it has eliminated an ugly sound that I had when the A/C was on (hot or cold at any level of fan speed). I had a whining noise that is a little difficult to describe (sort of like a bearing noise but more ugly)- I had checked on the interweb and its was/is a difficult one to fix. Some have had the dealer replace the compressor, some  have replaced the radiators and blower valves etc or even traced the noise to vibration to the A/C pipes. When my IMS was done we checked all the pulleys (bearings) and their was nothing wrong with them. Mine is fixed for now and I very happy about it. :)  The TRS pulley came with the a new serpentine belt so I am guessing that it could have had something to do with it -but it seems unlikely due to the sound that the car used to make. Posting this out of interest if any decide to buy a pulley etc - not a fix for A/C noise -interesting that mine is gone and I am considering myself lucky. TheTRS is this one - http://shop.tunersmotorsports.com/?product=trs-4-under-drive-pulley-wac  There are quite a few different brands available - Jake of flat six innovations (US manufacturer of reputable IMS fix) posted (US forum) a couple of underdrive pulleys to avoid, basically they need to be a soild style pulley as the other ones fail and all hell breaks loose. 

26717d1351570670-bbi-underdrive-pulley-a

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Great to hear! 

I wouldn't trust a non sold UDP unless it was a Porsche one like the GT3 etc. 

I haven't driven a non under drive pulley car so can't comment on performance but I love my car with it in. 

Only thing to keep an eye on is the battery charging as it's under driving the alternator at under aprox 2k rpm. 

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Only thing to keep an eye on is the battery charging as it's under driving the alternator at under aprox 2k rpm. 

Yes, cheers for the advise - I read about that also.

My daily commute is from sth east to northern suburbs, so its a decent drive, just as long as the Monash keeps above 40kph :wacko: 

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I have been investigating UDP for my Boxster S. Apparently along with exhaust and intake can give up to 20 to 30hp, seems ambitious!

As I track my 986 another issue can be overheating power steering pump UDP resolves, which make sense.

sorry to bring a humble 986 into a 996 post. ?

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As I track my 986 another issue can be overheating power steering pump UDP resolves, which make sense.

The tuner TRS that I bought the pulley from has a cooling kit but the other tuners would do too

 http://shop.tunersmotorsports.com/?product=trs-power-steering-oil-cooler-kit

http://tunersmotorsports.com/racing/986-spec-boxsters/

Bundle and save on shipping :)

 

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Is it a smart thing to under drive the alternator and water pump on these engines for a street driven application? 

Given the cooling appears marginal to start with and why would you want to risk an undercharged battery anyway?  What all for 5hp that you may get to use a total of a few seconds a week?  Surely if Porsche though you could get away with it, they would have done it themselves?

Just asking but if you guys reckon you know more, go ya hardest I guess, it's you car.  :)

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Is it a smart thing to under drive the alternator and water pump on these engines for a street driven application? 

Given the cooling appears marginal to start with and why would you want to risk an undercharged battery anyway?  What all for 5hp that you may get to use a total of a few seconds a week?  Surely if Porsche though you could get away with it, they would have done it themselves?

Just asking but if you guys reckon you know more, go ya hardest I guess, it's you car.  :)

If Jake R in the USA condones it and there haven't been any negative accounts then its a yes in my book

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Is it a smart thing to under drive the alternator and water pump on these engines for a street driven application? 

Given the cooling appears marginal to start with and why would you want to risk an undercharged battery anyway?  What all for 5hp that you may get to use a total of a few seconds a week?  Surely if Porsche though you could get away with it, they would have done it themselves?

Just asking but if you guys reckon you know more, go ya hardest I guess, it's you car.  :)

Yes I agree but also with "dan_189" - I have fiddled with all my cars and fallen victim of buying bits that cause more trouble than its worth.:wacko:  Re-engineering anything that has been engineered by professionals has a tendency to end detrimentally in some way. If my car was a weekender - I personally would not have done this, if it starts to cause me any issues - I will remove it. Trusting the interweb (inclusive of various Tuners endorsements)- underdrive seems to be without negative comments other than people expecting a power boost and not receiving it and its been on the market since a couple years after the 996 release so long term wear or stress on the components should be attributed to it if it did. Time will tell for me but so far so good. If it starts to give me issues - will update this thread. 

If Jake R in the USA condones it and there haven't been any negative accounts then its a yes in my book

That was the one that sealed it for me also.

 

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