Under drive pulley

Was looking at getting an under drive pulley. Cheap and easy way to add a little power. However, I've heard that these light weight smaller pulleys could affect the motor by throwing the timing off? Any truth to it affect your car?

Get a smaller belt and make sure you have 6 sided 24mm wrench. UD pulley from BBI (gen2) is excellent. Helped dyno ~286 (on crud CA 91) Might put more hair on your chest so be forewarned.

Best bang for the buck mod you can get for the cayman in my opinion .... I went with the mantis sport version along with new OEM belt and it works great ...

I went with the BBI pulley and the slightly shorter belt ( Gates K060825 ). You will have to trim off the boss on the block that was used to lock the engine at TDC with the old pulley. IMHO the BBI counter hold is not adequate to develop the required additional 90 degree rotation required. I believe the Mantis counter hold is a bit better (longer). I had my mechanic put a fresh bolt on for me so I could sleep better. Two DEs and it seems to be OK.

I went w the BBI LW UD Pulley (Stock pulley and BBI pulley)

You are surposed to only use a brand new bolt each time.

I went with a BBI for the reason on saving stress on other components such as the power steering and water pump. Can't honestly say that I feel any difference in the performance aspect of it.

I used the same belt myself without any issues and I don't know of anyone else who changed belts either. I don't by the timing thing, that doesn't make any sense to me.

I put the RSS pulley on as part of my Evo GT350 mods in March 2011, and a shorter belt was required as well. However, in November as it started to get colder I threw a CEL on start up (car is garaged), which was originally diagnosed as a bad coil. The CEL came right back and I left the car at the dealer for further diagnosis (the dealer did the pulley, intake and TB upgrades). The mis fire moved across several cylinders when the started the car up cold each day, with no firm diagnosis other than possible carbon build up on the valves (maybe related to winter gasoline mix) or maybe slipping of the belt on the pulley. So we decided to put the stock pulley back on, and add Techron to the next few tanks of gas - what ever it was, no CELs since...........

The under drive pulley has nothing to do with engine timing. I have the RSS part with standard belt and no issues. I have noticed no performance improvement but added the part "while we were in there" for the Motorsport AOS as I previously had P/S issues. Earlier added a P/S cooler which seemed to fix the P/S issue.

Hello I went with the new design Mantissport one at $140 in special... including the tool .... and decided to used a shorter length optimal for my configuration OEM Continental is 2115mm, so I went 2100mm (about 1/2" off) Many brand made a belt in this particular size Brand: Part#: Continental PK060820 ***similar as the OEM*** Bando 6PK2080 Dayco 5060820 Gates K060820 ***always a good choice*** mm 6PK2083 Napa 25-060820

25,000 miles and a bunch of DEs on BBI UDP. Used oem belt without any issues. Replaced the belt during routine maintenance with a new oem belt. Use a new bolt - it's cheap insurance.

Underdrive pulles have been the cause of many enthusiast forum squabbles for decades. There is some credence to the theory that the stock pulley serves to absorb harmonics from the firing order (hence why it is sometimes referred to as a harmonic dampener.) This also lends itself to the issue that the poster above was having with a cold engine misfire or what the knock sensor assumed was a misfire. To what extend does an engine receive damage by removing this part is up for debate. I know in the BMW world those long I6 motors do not respond well to changing the stock part. Would a compact boxer engine with a shorter crank suffer any affects? It seems like the anecdotal evidence suggests not. For me it isn't worth the risk for a couple of HP.

The Pulley for a gen 1 car does NOT have or form part of a harmonic balancer. The mass is also insignificant. For gen 2 its the opposite. A UDP for a gen 1 works good.

Gotsol, I'm on the fence on this mod myself. I can say that with my previous car, a G35 coupe, a lot of forum members also referenced the harmonic dampening of the OEM pulley on the G35. I decided to put an underdrive pulley on my G anyway, and had 60K+ miles on it with the underdrive pulley and no issues. I sold the car to my hopefully-future-brother-in-law (lol) a few months back and it's still going strong. 4by4, Can you comment on the difference from Gen1 to Gen2? Why the switch? Was it because they realized it DID need to serve that purpose in Gen 1, so they made that revision in Gen 2? Or was there some other design factor that changed the need?

If it doesn't dampen then what is that rubber ring?

The pulley is not a harmonic balancer. There is no rubber on it

IMO you should not install UDP for the sole intent of increasing HP - it's insignificant in that regard. You would, however, install the UDP to save your power steering pump and other components prone to overheating/melting in the rack/steering system - particularly in gen I cars. Haven't heard of as many power steering failures in later cars.

+1. I've not been able to detect any performance gain from the UDP. BTW, although it hasn't been asked in this thread, there is no detectable decrease in AC performance resulting from the lower compressor speed. The UDP installation has several theoretical benefits with, AFAIK, no actual detriment aside from the expense.

If your the sort of person that expects any mod should have a worthwhile HP improvement then dont do this, get a turbo. But if your the sort of person that wants to squeeze 100% from a NA engine and need all you can get then do it.

No idea. I can only guess that it was part of the refinement process or readying for the upcoming electro-hydrolic steering.

I'd have to agree I don't any way this plays into the harmonic balance. I've had mine changed for about 10K miles and can't detect any difference in mis-fires or other engine control feature. As far a performance boost, I would have to disagree with the comments about no performance improvement. I had mine changed and at the same time I was installing a new flash in the ECU . However, when I picked the car up the shop apologized because they could not do the flash due to not getting the latest version downloaded in time, so I had to bring it back So I take it home and not expecting any difference in the car...wow, what a shock...with just the UDP, it felt like a new car! You know, when you make a change that you expect big things from, you can always "feel" it, but honestly I wasn't expecting much here, so a nice surprise. Quicker revs and much snapper feel. So maybe no HP but the effect was the same...later, after the flash it just got better. I think for this engine the UDP is a good mod and well worth it, with no downsides at all.

Not that impressive on my side, but yes I notice improvement on higher RPM...

I think "feel" is really important, in fact I know it is, as a driver. I know it has saved both me and my car. I won't regale everybody with the story, but I believe "feel", feeling for the car is an athletic gift. Like you, I could tell right away. And there is an improvement in performance. And if I were to pick one adjective with regard to the lightweight underdrive pulley? It would be smooottthhh !

Revive old Thread. So, with any aftermarket pulleys for 987.1 It increases power and decreases stress/temp issues with PS pump. Not worried about AC. But more importantly: How about Alternator and especially Water Pump esp. for us guys tracking our cars. Any issues with temperature?

I have about 115 track days on a 987.1 CaymanS . Added the underdrive pulley years ago while "I was in there". I can't say I felt any additional power but do believe turning the P/S pump, water pump, and alternator slower can't hurt. No ill effects from the change. I don't think the pulley will solve the P/S issue and am using a P/S cooler.

THX. That helps. Off I go to install. BTW: I have never had PS problems on track with OE setup. Knock on wood.

WOW!:drivingskid:

Has anyone been able to get a new under drive pulley bolt torqued to 50 NM and then 90 degrees?? I'm a pretty strong guy but there is no way I can turn this bolt 90 additional degrees.

When I installed the UDP I used a jack handle on a 1/2" drive breaker bar for added leverage. Made it easy. Dan Sent from my iPhone using Tapatalk

Damn. I should have thought of that. Great advice. Just put everything back together.

Ok. Done. Had to put jack handle on the 'tool' to hold the pulley in place, and a long torque wrench on the bolt. Then prepare to flex your muscles. BTW: I had the torque wrench set to 220 ft/lb and it never 'clicked'.