underdrive pulley
05-14-2011, 12:26 PM
#16
Rennlist Member
what the heck does this have to do with Underdrive pullies?
http://www.modernghana.com/news/2066...-contempt.html
05-14-2011, 06:25 PM
#18
Yeah what is TDC Boss?
what the heck does this have to do with Underdrive pullies?
http://www.modernghana.com/news/2066...-contempt.html
what the heck does this have to do with Underdrive pullies?
http://www.modernghana.com/news/2066...-contempt.html
05-15-2011, 01:16 PM
#20
eh, I'm pretty sure its a shorter belt too... try searching google. many other people do it especially in the muscle car world.
Last edited by RPMulli; 05-15-2011 at 07:40 PM.
05-16-2011, 02:06 AM
#25
Racer
I fitted a Flat6 underdrive pulley to my Boxster S about 2 years ago - the reported improvement is about a 10 hp gain, which (according to my delicate bum dyno) is about right.
Here are a couple of observations:
You can definately feel the difference mostly in the low to medium rev range - once above 6,000 rpm its not that noticable.
Yes, the pulley is smaller diameter and you need a shorter belt, which comes with the pulley kit.
Yes, you have to shave off a small part (~5mm) of the TDC (top dead centre) boss which is a hollow alloy protrusion cast into the crankcase and used to fit a TDC rod when locking the camshafts. This is easily done and does not impare the boss.
I did a before and after voltage test of the alternator output because it is turning slower with the new pulley. By the time the alternator is up to 1,800 rpm, its output is just about the same as with the standard pulley.
The interior of the Boxster is quieter due to the lowering of the belt & accessories.
Dollar wise, it is the best bang for yor buck you can get - I've had it on the car for 10,000 km with zero problems - I'm a very happy camper....
And you can always put back the old one if you need to.
Here are a couple of observations:
You can definately feel the difference mostly in the low to medium rev range - once above 6,000 rpm its not that noticable.
Yes, the pulley is smaller diameter and you need a shorter belt, which comes with the pulley kit.
Yes, you have to shave off a small part (~5mm) of the TDC (top dead centre) boss which is a hollow alloy protrusion cast into the crankcase and used to fit a TDC rod when locking the camshafts. This is easily done and does not impare the boss.
I did a before and after voltage test of the alternator output because it is turning slower with the new pulley. By the time the alternator is up to 1,800 rpm, its output is just about the same as with the standard pulley.
The interior of the Boxster is quieter due to the lowering of the belt & accessories.
Dollar wise, it is the best bang for yor buck you can get - I've had it on the car for 10,000 km with zero problems - I'm a very happy camper....
And you can always put back the old one if you need to.
09-25-2012, 09:17 PM
#26
Race Director
I know this is an old thread, but I wanted to chime in anyway. Feel free to ignore.
Here are a couple of fact-ish points about the UD pulley:
1) The pulley doesn't increase horsepower. It makes the other accessories driven by the serp. belt turn more slowly, making that extra power available to the wheels.
2) The pulley does not cause overheating. I ran the 4" underdrive pulley in my 2003 Boxster for 2+ years, and did not notice any significant temperature change before/after. A couple of folks have theorized that the underdrive pulley may actually prevent cavitation at higher RPMs, but I have no way to verify this.
3) The pulley does not cause charging issues. Although I use a battery maintainer if a car will be unused for more than a week or two, I did not notice any battery issues / electrical issues due to the pulley. The car operates at a wide range of RPM anyway. If you're worried, just drive a little faster.
Over the four years I owned my Boxster, I installed just about every bolt-on performance mod I could get my hands on, and the underdrive pulley was by far the best "bang for the buck." In fact, I'd be willing to go out on a limb and say that it's the only bolt-on mod that I can actually tell made ANY significant improvement. It's also the only mod that is backed up by common sense: Using less power to drive the accessories results in more power at the wheels.
As stated above, I installed just about every mod I could find on my Boxster. This pulley will be the ONLY bolt-on mod I install on my 996, at least until I can swing a turbo kit.
*Disclaimer* Everything above is opinion. If you install an underdrive pulley and your car overheats, the battery drains, and your power steering pump explodes and kills everyone nearby - and starts a brush fire that kills a sign-language-speaking gorilla holding newborn panda twins - I am liable for nothing other than saying, "Dang, guess I was wrong."
Here are a couple of fact-ish points about the UD pulley:
1) The pulley doesn't increase horsepower. It makes the other accessories driven by the serp. belt turn more slowly, making that extra power available to the wheels.
2) The pulley does not cause overheating. I ran the 4" underdrive pulley in my 2003 Boxster for 2+ years, and did not notice any significant temperature change before/after. A couple of folks have theorized that the underdrive pulley may actually prevent cavitation at higher RPMs, but I have no way to verify this.
3) The pulley does not cause charging issues. Although I use a battery maintainer if a car will be unused for more than a week or two, I did not notice any battery issues / electrical issues due to the pulley. The car operates at a wide range of RPM anyway. If you're worried, just drive a little faster.
Over the four years I owned my Boxster, I installed just about every bolt-on performance mod I could get my hands on, and the underdrive pulley was by far the best "bang for the buck." In fact, I'd be willing to go out on a limb and say that it's the only bolt-on mod that I can actually tell made ANY significant improvement. It's also the only mod that is backed up by common sense: Using less power to drive the accessories results in more power at the wheels.
As stated above, I installed just about every mod I could find on my Boxster. This pulley will be the ONLY bolt-on mod I install on my 996, at least until I can swing a turbo kit.
*Disclaimer* Everything above is opinion. If you install an underdrive pulley and your car overheats, the battery drains, and your power steering pump explodes and kills everyone nearby - and starts a brush fire that kills a sign-language-speaking gorilla holding newborn panda twins - I am liable for nothing other than saying, "Dang, guess I was wrong."
09-25-2012, 09:56 PM
#28
I know this is an old thread, but I wanted to chime in anyway. Feel free to ignore.
Here are a couple of fact-ish points about the UD pulley:
1) The pulley doesn't increase horsepower. It makes the other accessories driven by the serp. belt turn more slowly, making that extra power available to the wheels.
2) The pulley does not cause overheating. I ran the 4" underdrive pulley in my 2003 Boxster for 2+ years, and did not notice any significant temperature change before/after. A couple of folks have theorized that the underdrive pulley may actually prevent cavitation at higher RPMs, but I have no way to verify this.
3) The pulley does not cause charging issues. Although I use a battery maintainer if a car will be unused for more than a week or two, I did not notice any battery issues / electrical issues due to the pulley. The car operates at a wide range of RPM anyway. If you're worried, just drive a little faster.
Over the four years I owned my Boxster, I installed just about every bolt-on performance mod I could get my hands on, and the underdrive pulley was by far the best "bang for the buck." In fact, I'd be willing to go out on a limb and say that it's the only bolt-on mod that I can actually tell made ANY significant improvement. It's also the only mod that is backed up by common sense: Using less power to drive the accessories results in more power at the wheels.
As stated above, I installed just about every mod I could find on my Boxster. This pulley will be the ONLY bolt-on mod I install on my 996, at least until I can swing a turbo kit.
*Disclaimer* Everything above is opinion. If you install an underdrive pulley and your car overheats, the battery drains, and your power steering pump explodes and kills everyone nearby - and starts a brush fire that kills a sign-language-speaking gorilla holding newborn panda twins - I am liable for nothing other than saying, "Dang, guess I was wrong."
Here are a couple of fact-ish points about the UD pulley:
1) The pulley doesn't increase horsepower. It makes the other accessories driven by the serp. belt turn more slowly, making that extra power available to the wheels.
2) The pulley does not cause overheating. I ran the 4" underdrive pulley in my 2003 Boxster for 2+ years, and did not notice any significant temperature change before/after. A couple of folks have theorized that the underdrive pulley may actually prevent cavitation at higher RPMs, but I have no way to verify this.
3) The pulley does not cause charging issues. Although I use a battery maintainer if a car will be unused for more than a week or two, I did not notice any battery issues / electrical issues due to the pulley. The car operates at a wide range of RPM anyway. If you're worried, just drive a little faster.
Over the four years I owned my Boxster, I installed just about every bolt-on performance mod I could get my hands on, and the underdrive pulley was by far the best "bang for the buck." In fact, I'd be willing to go out on a limb and say that it's the only bolt-on mod that I can actually tell made ANY significant improvement. It's also the only mod that is backed up by common sense: Using less power to drive the accessories results in more power at the wheels.
As stated above, I installed just about every mod I could find on my Boxster. This pulley will be the ONLY bolt-on mod I install on my 996, at least until I can swing a turbo kit.
*Disclaimer* Everything above is opinion. If you install an underdrive pulley and your car overheats, the battery drains, and your power steering pump explodes and kills everyone nearby - and starts a brush fire that kills a sign-language-speaking gorilla holding newborn panda twins - I am liable for nothing other than saying, "Dang, guess I was wrong."
09-25-2012, 09:57 PM
#29
Former Vendor
We love the UD pulley, but the unit we use has a solid center. The CVheetah looks fine, just don't use this one! We've seen three fail this year alone that came in one customers engines. This one didn't have another track day left in it.
But it could have been worse. This is what happens when fashion is employed where it has no place.
I have engines with hundreds of track hours using our solid center UD pulley with zero issues and thousands of miles. The top one above has less than one track season under its belt. The factory isn't the ultimate authority on these sorts of things, hell they are the ones who created an engine with 23 documented modes of failure, most of which occur on the street and not on the track.
But it could have been worse. This is what happens when fashion is employed where it has no place.
I have engines with hundreds of track hours using our solid center UD pulley with zero issues and thousands of miles. The top one above has less than one track season under its belt. The factory isn't the ultimate authority on these sorts of things, hell they are the ones who created an engine with 23 documented modes of failure, most of which occur on the street and not on the track.
09-26-2012, 12:09 AM
#30
Race Director
I see this same question asked on every car forum I've ever been a member of. "If this mod is so great, why doesn't it come from the factory this way?"
The underdrive pulley is a way to eke out some improvement over what Porsche provided. Porsche could also have bored out the cylinders and strapped a turbo onto every 996 that went out the door - but they didn't.
Porsche - just like Hyundai or Ford - has to strike a balance between performance and reliability. Every mod you make - whether it's an underdrive pulley or an aftermarket supercharger - runs the risk of decreasing reliability in the name of increasing performance. This mod is no different. Running the water pump, power steering pump, air conditioner, etc. could keep that piece of equipment from performing optimally, and might even shorten its life.
No car maker that offers a warranty ships their product performing at 100% potential output. It doesn't make sense. When you dial back the performance a little, mean time between failure increases exponentially. Machines that operate at 100% fail quickly - consider how long drag engines last.
I don't think you're busting ***** - but assuming that Porsche wrings every HP and ft-lb of torque out of their engines from the factory is a fallacy. You wouldn't WANT to own such a product. Porsche provides a great product, but there is always room for improvement. Modding your engine is a risk-vs-reward scenario. The mods with the greatest reward also carry the greatest risk.
The underdrive pulley is a way to eke out some improvement over what Porsche provided. Porsche could also have bored out the cylinders and strapped a turbo onto every 996 that went out the door - but they didn't.
Porsche - just like Hyundai or Ford - has to strike a balance between performance and reliability. Every mod you make - whether it's an underdrive pulley or an aftermarket supercharger - runs the risk of decreasing reliability in the name of increasing performance. This mod is no different. Running the water pump, power steering pump, air conditioner, etc. could keep that piece of equipment from performing optimally, and might even shorten its life.
No car maker that offers a warranty ships their product performing at 100% potential output. It doesn't make sense. When you dial back the performance a little, mean time between failure increases exponentially. Machines that operate at 100% fail quickly - consider how long drag engines last.
I don't think you're busting ***** - but assuming that Porsche wrings every HP and ft-lb of torque out of their engines from the factory is a fallacy. You wouldn't WANT to own such a product. Porsche provides a great product, but there is always room for improvement. Modding your engine is a risk-vs-reward scenario. The mods with the greatest reward also carry the greatest risk.
If the UD pulley was such a "good" noticeable mod why wouldn't Porsche have used a smaller pulley thus increasing the HP avail. at the wheels and reducing the cost that is required to produce such pulley, thus reducing the cost of the car overall... Not bustin your ***** just an honest thought..