986 Forum - The Community for Porsche Boxster & Cayman Owners

986 Forum - The Community for Porsche Boxster & Cayman Owners (http://986forum.com/forums/)
-   Performance and Technical Chat (http://986forum.com/forums/performance-technical-chat/)
-   -   Underdrive pulley recommendations? (http://986forum.com/forums/performance-technical-chat/22814-underdrive-pulley-recommendations.html)

Dragonwind 11-18-2009 07:06 PM

Underdrive pulley recommendations?
 
I've been wanting to put a new pulley on and wondered if someone can recommend one.
I looked around Flat6 but didn't see anything there. I see a few out there for sale but would prefer a word form someone who has experience with one.
Thanks
Chris

Jake Raby 11-18-2009 09:01 PM

I am still testing our 4" pulley in real world conditions to see how it effects the operation of the charging, power steering and A/C subsystems. Its the smallest pulley on the market and so far has out performed every other I have tested back to back in the performance category.

I have not added them to our site yet because they haven't proven themselves thoroughly enough as of yet. I hope to have them on line by the beginning of the new year.

I have almost 8K on the test pulley in my 996 and 14K on the unit in the Boxster test car.. I want to see how they perform in cooler weather.

Dragonwind 11-19-2009 02:56 AM

That's a very tiny pulley! How cold does it get in GA? I'm in CT and would be dealing with Zero temps sometimes.
Chris

Wingnut2u 11-19-2009 05:42 AM

Dragon

you can go to boxsterspec.com and do a search for under pulleys, a lot of the spec boxster guys are starting to use them. One the members, Chris Amond, has his own design that I put on my car and I have been very happy with it so far

JAAY 11-19-2009 05:53 AM

I have the RSS UDP. Got it from stuttgartperformance.com Seems to be good.

Jake Raby 11-19-2009 07:48 AM

We see single digits here in the dead of winter, BUT the other cold weather data will be gathered by LN Engineering on their Boxster test car that I built the engine for in March of 09. They will certainly see temps well below zero.

In the heat of the summer this pulley did awesome both on the track and the street.

Lobo1186 11-19-2009 12:44 PM

now what is the threat here with the smaller pulley? the belt will move... slower and so affecting subsystems how?

Johnny Danger 11-19-2009 02:13 PM

I installed BBI Autosport's latest light weight UDP. I am very pleased with it. Its difficult to qualify any performance gain since it was installed along with some other upgrades. However, the car feels great, and there is plenty of data to suggest that it adds hp. :)

Dragonwind 11-19-2009 02:24 PM

Thanks for all the replies. I put my stock headers back in and likely my stock muffler this weekend. I never got dyno data but car feels exactly the same. I had the original maxspeed headers. Now it makes the muffler sound lousy so back to stock till I can find a decent PSE. I want the pully and likely Pedro's techno torque instead.

Chris

jaykay 11-19-2009 07:02 PM

I am running the Mantis pulley at the moment with no ill-effects save some power steering pump wine on full lock while parking.....It is suppose to give 7hp. I did notice a difference when I first put it on...the engine felt it was now free to give! The car pulled just a bit hard on full throttle...this is all subjective feel of course.

amondc 12-01-2009 04:35 PM

This one works pretty good.
 
Have not had any problems with this 4" pulley.

Chris

Jake Raby 12-01-2009 05:09 PM

Quote:

Originally Posted by amondc
Have not had any problems with this 4" pulley.

Chris

Me either ;-0

23109VC 12-03-2009 07:31 PM

on a 2.7L 5 speed - would insalling this pulley create a noticeable difference in acceleration? would engine rev up faster... even if just a little bit..would it be enough to notice?

given the relatively modest price of a pulley - it might be a worthwhile mod if it didn't hurt anything and could actually make some gains that could really be noticed...

amondc 12-04-2009 05:15 AM

I guess it depends on how sensitive your butt is. The pulley will add about 10hp.

Jake Raby 12-04-2009 08:45 AM

So far these pulleys have proven to give me the best improvements in real performance. They bolt on more than an ECU flash or a 3,000.00 exhaust system.

pboard66 12-04-2009 08:01 PM

I apologize in advance for the newbie question, but is there a noticeable increase in vibration? I threw an UDP on my 4 cylinder commuter and although I was happy with the small power gain, I do notice some resonance in the cabin.

Boxster44 12-04-2009 09:17 PM

Ques - when you say Underdrive Pulley and HP gains, are you assuming w/o A/C?... or still have A/C connected?

Would there be more HP gain w/o driving A/C?

thanks,

kj

Lobo1186 12-04-2009 09:25 PM

yes no A/C would "gain" you more HP, if you were to remove the whole system also some weight would be lost giving you even more...

however, its more along the lines that you will just have more HP that the car makes already available to you.


correct me if im wrong.

amondc 12-05-2009 05:11 AM

Correct. They pulley does not create horsepower it only reduces the factors that rob hp from the motor. Another way to think of it is that the motor is just an air pump. It sucks, bangs and blows. If you don't change the amount of air it sucks or how big the bang is or how it blows you do no "create" hp.

That said all we really care about is how much hp we have at the wheels not how we get it, and the pulley does work.

Boxster44 12-05-2009 05:34 AM

... sorry, I asked the question the wrong way. I know it doesn't create HP, I was just surprised at the estimate of 10 extra available to the drive train... that's pretty darn good for just an external pulley change.

I've been thinking about the pulley and instead of full A/C delete, just go with the shorter belt and eliminate the A/C drag from the equation. This pushes me a little farther along.

You're right about the weight, that compressor feels like it weighs 20 lbs. alone... the whole system ought to net 40ish?... no?


thanks,



kj

amondc 12-05-2009 05:49 AM

no worries boxster44. I think the reason there is such a large gain is because you are slowing down all the accessories but Jake can give us a much better answer.

and yes if you remove all the a/c stuff you will pull about 35-40lbs out of the car.

blue2000s 12-05-2009 06:21 AM

Spinning the water pump, alternator, and AC compressor takes power. In the case of the pump and compressor, that power increases by the third order with speed. In other words, it takes 8 times more power to drive a pump twice as fast.

You can imagine that if you spin the pumps more slowly, more of the engine's power can go to twisting the wheels. And because of the third order relationship the faster you spin the engine, the more power is saved compared to a larger pulley.

The drawback is that at engine lower speeds, the pumps may not flow sufficient water to keep the engine cool in an extreme environment, or the alternator may not provide enough current to a car with a very high draw stereo with the lights on.

As Mr. Raby has found, everythimg works fine in his region.

Lobo1186 12-05-2009 07:09 AM

Quote:

Originally Posted by Boxster44
... sorry, I asked the question the wrong way. I know it doesn't create HP, I was just surprised at the estimate of 10 extra available to the drive train... that's pretty darn good for just an external pulley change.

I've been thinking about the pulley and instead of full A/C delete, just go with the shorter belt and eliminate the A/C drag from the equation. This pushes me a little farther along.

You're right about the weight, that compressor feels like it weighs 20 lbs. alone... the whole system ought to net 40ish?... no?


thanks,



kj

im sure that is what you meant anyways but its good to clarify for people who come on here and may not know. but yes im not sure how much the whole AC weighs but it is substantial.

if money is no object. (but usually it is!)

you could do AC delete and replace all panels on the body with Fiberglass or carbonfiber and that would net you quite a bit of weight. I have also heard that the sound proofing removal is quite good too.

stephen wilson 12-05-2009 07:16 AM

I surprised that no manufacturer has gone to an electric water pump, with it's speed electronically controlled. There's lot's of power and efficiency to be gained, though I'm not sure it would ever be as reliable as a belt driven pump. (though Boxster water pumps haven't proved that reliable!)

Topless 12-05-2009 08:21 AM

Quote:

Originally Posted by stephen wilson
I surprised that no manufacturer has gone to an electric water pump, with it's speed electronically controlled. There's lot's of power and efficiency to be gained, though I'm not sure it would ever be as reliable as a belt driven pump. (though Boxster water pumps haven't proved that reliable!)

I am not sure if any benefits would be found here. Having a mechanical WP that varies with engine speed is a good thing. Higher RPMs = higher heat = higher coolant velocity. Also electricity is not free. With an electric water pump, first you must convert mechanical energy to electrical energy with the alternator (maybe 20% loss) and then convert it back to mechanical energy at the pump (maybe another 20% loss). By this very rough calculation an electric pump would consume 40% more energy than a mechanical one for the same coolant velocity. The mechanical pump looks better to me. What am I missing?

JFP in PA 12-05-2009 08:38 AM

Quote:

Originally Posted by Topless
I am not sure if any benefits would be found here. Having a mechanical WP that varies with engine speed is a good thing. Higher RPMs = higher heat = higher coolant velocity. Also electricity is not free. With an electric water pump, first you must convert mechanical energy to electrical energy with the alternator (maybe 20% loss) and then convert it back to mechanical energy at the pump (maybe another 20% loss). By this very rough calculation an electric pump would consume 40% more energy than a mechanical one for the same coolant velocity. The mechanical pump looks better to me. What am I missing?


There are significant advantages to an electrically driven water pump:

1. Reduced mechanical drag on the engine (frees up HP); the higher the engine revs, the more power is saved (drag goes up with engine speed).
2. Slows down the circulation of coolant to a constant speed (higher RPM’s actually reduce the ability of the coolant to exchange heat with the air at the radiators because it is moving too fast).
3. Compact; no pulley or belt is required, so it takes up less space.
4. Works if the belt fails.

By-the-by, electrically driven water pumps are commonly used on race engines for the above reasons……………

Te primary reason that more aftermarket manufacturers are not involved with making them for the M96 engine is the small population size of the application.

23109VC 12-05-2009 09:02 AM

1) where can I get this U/D pulley?
2) how much does it cost?
3) how much will my mechanic likely want to install it? (i'm not even going to try to do it myself)

this sounds like a great bang fgor the buck mod!

Boxster44 12-05-2009 10:17 AM

Lobo,

Yes..... I think amondC (Chris, right?) can really go into detail there as I believe he's with the Spec Boxster group in Texas and they do lots of things with their cars.

kj

Topless 12-05-2009 10:38 AM

Quote:

Originally Posted by JFP in PA
There are significant advantages to an electrically driven water pump:

1. Reduced mechanical drag on the engine (frees up HP); the higher the engine revs, the more power is saved (drag goes up with engine speed).
2. Slows down the circulation of coolant to a constant speed (higher RPM’s actually reduce the ability of the coolant to exchange heat with the air at the radiators because it is moving too fast).
3. Compact; no pulley or belt is required, so it takes up less space.
4. Works if the belt fails.

By-the-by, electrically driven water pumps are commonly used on race engines for the above reasons……………

Te primary reason that more aftermarket manufacturers are not involved with making them for the M96 engine is the small population size of the application.

Sorry JFP, maybe I am just a little dim. I still don't get it:
1. You still have mechanical drag, just at the alternator instead of the WP, plus inefficiencies of conversion.
2. A smart variable speed pump that measures coolant temp and maximizes heat transfer at all rpms would definitely be useful. A real plus if there is such a thing. I have just never seen one this sophisticated.
3. We already have a belt and pulleys on our cars, no space savings.
4. Works if the belt fails, not if the circuit fails. Seems like a wash.

JFP in PA 12-05-2009 11:31 AM

Quote:

Originally Posted by Topless
Sorry JFP, maybe I am just a little dim. I still don't get it.

That is quite obvious.

1. You still have mechanical drag, just at the alternator instead of the WP, plus inefficiencies of conversion.

Many electric pump applications (racing apps) do not use an alternator; but those that do definitely see a measurably reduced drag (seen on the dyno) compared to a mechanically driven unit. It is not a "wash"; it is a net gain...........hence their use on race cars.

2. A smart variable speed pump that measures coolant temp and maximizes heat transfer at all rpms would definitely be useful. A real plus if there is such a thing. I have just never seen one this sophisticated.

You have not for a reason, they currently do not exist. Attempts to do this, even with digital electronics, proved to be overly complicated, not dependable, and added weight. Running the pump at a fixed speed electrically offers simplicity, better cooling, lower weight and free power without all the complications.

3. We already have a belt and pulleys on our cars, no space savings.

Electrically driven pumps are definitely smaller and lighter than their belt driven counterparts.........

4. Works if the belt fails, not if the circuit fails. Seems like a wash.

And if the car gets hit by a meteorite, or is swamped by molten lava, it doesn't work eithereither................ :confused:

al83s 12-05-2009 12:40 PM

AC compressors have a clutch, thus when the AC is off - the electric clutch is disengaged and the compressor pulley is spining free (not much drag there). Removing AC all together will save you weight, but wont give you any power gain.
Installing an underdrive pulley will slow down the AC compressor as well thus it will have less drag when the AC is on (similar to Honda guys installing smaller compressors on Accords I guess)
Just my 2 cents

Topless 12-05-2009 12:52 PM

Quote:

Originally Posted by JFP in PA
That is quite obvious.

1. You still have mechanical drag, just at the alternator instead of the WP, plus inefficiencies of conversion.

Many electric pump applications (racing apps) do not use an alternator; but those that do definitely see a measurably reduced drag (seen on the dyno) compared to a mechanically driven unit. It is not a "wash"; it is a net gain...........hence their use on race cars.

2. A smart variable speed pump that measures coolant temp and maximizes heat transfer at all rpms would definitely be useful. A real plus if there is such a thing. I have just never seen one this sophisticated.

You have not for a reason, they currently do not exist. Attempts to do this, even with digital electronics, proved to be overly complicated, not dependable, and added weight. Running the pump at a fixed speed electrically offers simplicity, better cooling, lower weight and free power without all the complications.

3. We already have a belt and pulleys on our cars, no space savings.

Electrically driven pumps are definitely smaller and lighter than their belt driven counterparts.........

4. Works if the belt fails, not if the circuit fails. Seems like a wash.

And if the car gets hit by a meteorite, or is swamped by molten lava, it doesn't work eithereither................ :confused:

So in conclusion, if we have a specialty race car with no belts or pulleys, no alternator, and electrical circuits that are far more reliable than Porsche circuits, a constant speed elect. pump would be a good idea. Boxster not so much, go with the underdrive pulley instead. Ok I understand now. Thanks for your help. Diplomatic as always JFP. :rolleyes:

JFP in PA 12-05-2009 01:09 PM

Quote:

Originally Posted by Topless
So in conclusion, if we have a specialty race car with no belts or pulleys, no alternator, and electrical circuits that are far more reliable than Porsche circuits, a constant speed elect. pump would be a good idea. Boxster not so much, go with the underdrive pulley instead. Ok I understand now. Thanks for your help. Diplomatic as always JFP. :rolleyes:

Not quite: If an electrically driven, constant speed water pump was available, which it currently not the case, the M96 in your street-driven Boxster would run cooler, as would the oil; would make more power and probably (all other things being equal) live longer. But only if you understand why………………

But have a nice day anyway........................:ah:

Jake Raby 12-05-2009 01:38 PM

I have evaluated the 4" pulley with both A/C and without.. The gains are real, not to mention reduced coolant temps and dramatically reduced power steering temps while on the track.

stephen wilson 12-05-2009 03:04 PM

Actually, there is at least one aftermarket electric water pump with an electronic controller that varies pump speed to control engine temperature, manufactured by Craig Davies.

I don't think any automotive manufacturer would lack the resources to design such a system. They manage to map fuel injection & ignition timing using dozens of sensors, over all possible operating conditions, while controlling emissions. Controlling a water pumps speed would be a piece of cake.

amondc 12-05-2009 06:29 PM

Quote:

Originally Posted by 23109VC
1) where can I get this U/D pulley?
2) how much does it cost?
3) how much will my mechanic likely want to install it? (i'm not even going to try to do it myself)

this sounds like a great bang fgor the buck mod!


pm sent......

amondc 12-05-2009 06:34 PM

Quote:

Originally Posted by Boxster44
Lobo,

Yes..... I think amondC (Chris, right?) can really go into detail there as I believe he's with the Spec Boxster group in Texas and they do lots of things with their cars.

kj

Thats me!! :cheers:

Jake Raby 12-05-2009 07:39 PM

Quote:

Originally Posted by stephen wilson
Actually, there is at least one aftermarket electric water pump with an electronic controller that varies pump speed to control engine temperature, manufactured by Craig Davies.

I don't think any automotive manufacturer would lack the resources to design such a system. They manage to map fuel injection & ignition timing using dozens of sensors, over all possible operating conditions, while controlling emissions. Controlling a water pumps speed would be a piece of cake.

We purchased one of these last year.. Problem is there is no way to efficiently route the water to/from the engine due to the OE water pump location.. There also isn't any place worth a damn to mount the electric unit.

The engine's design is the variable...

JFP in PA 12-06-2009 07:05 AM

Quote:

Originally Posted by stephen wilson
I don't think any automotive manufacturer would lack the resources to design such a system. They manage to map fuel injection & ignition timing using dozens of sensors, over all possible operating conditions, while controlling emissions. Controlling a water pumps speed would be a piece of cake.

The only problem is that a better system would cost the OEM five cents more than the one they gave you....................and there is no "sex appeal" in cooling systems.

stephen wilson 12-06-2009 09:33 AM

Yes, the Boxster's tight packaging is problematic, which of course an OEM could solve, but as JFP mentioned, they have no real incentive to do so.


All times are GMT -8. The time now is 06:19 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website