Does anyone have any experience with using a light weight under pulley on a 986 Boxster S ?

 

Mantis Racing first developed the underdrive pulley for their 987 Cayman S. The idea is simply to slow down the accessories (power steering pump, alternator, AC compressor) on a car that spends a lot of time running high revs. 986/987 PS pumps are known to overheat and leak under heavy track use.

A side benefit is that the underdrive pulley reduces parasitic drag from these components and you can measure an increase in hp and torque at all rpms between 5-10 rwhp depending on the model. One size fits all 986/987 and there is no known downside to adding this as long as it is within your class rules for racing. Installation takes about 30 min with the special tool included in the kit. It's not a cool shiny CF bling item you can show off at cars & coffee, it just works. Way better than a reflash that gives a little boost in ponies only above 6500 rpm IMHO.
http://www.mantissport.ca/tabid/55/P...3/Default.aspx

 

WOW !! great explanation and Post
Mantis and BBI are the 2 I see everyone using .have yet to hear about an unhappy customer from either vendor.
BBI just came out with a new lightweight version last friday and already has track tested its worthyness.
You cannot go wrong with either choice IMO
Cajundaddy makes a strong case for the mantis though . I did not know Mantis was the first .

 

Does the crank pulley in these cars have any sort of harmonic balancer built in? On the M3 it did have one and the aftermarket units all deleted it and some motors let go.

 

Do they make one for the 3.8?

 

A very valid question. I had to check with my expert to answer:

" On the M96 motor (986/996) it is a simple drive pulley with no harmonic balancer. On these cars the harmonic balance/dampening is achieved with the dual mass flywheel. The later M97 motor does incorporate a balancer with the drive pulley so an underdrive pulley install is a little more complicated."

If you drive a 986/996 the underdrive pulley is a simple change with no balance issues as long as the new one is true and balanced to begin with. I hope this answers your question.

 

So would this underdrive pulley offer any benefits for cars that see no track use? How would it affect the efficiency of the a/c, water pump, and alternator during normal use?

 

for normal street driving (rpms under 4k, let say) there's a slight effeciency benefit from the reduced drag. all of your accessories are simply running slower and using less energy. the downside is at idle and near-idle where your power steering pump is running below factory speed making the steering wheel a little harder to turn. also, never run underdrive pulleys if you have a lot of aftermarket electronic gear (subs, strobes, superasskickingoverthetop bling) because your alternator won't be running at minimum speed either.

 

This is somewhat incorrect. The M97.21 engine in the Cayman does not incorporate a harmonic balancer in the pulley. It is just stamped aluminum and can be replaced wih either the Mantis or BBi pulley.

I will not make this statement for all M97 derivatives as I am not positive.

Cheers,

 

I purchased BBI's newest under drive pulley yesterday. They reverted back to making their pulley the same size as the oem. However, its 2/3rds lighter than the stock unit and the original belt is maintained. We'll see how it goes.

 

RSS offers a lightweight underdrive pully made from 6061-T6 aluminum that has been very successful.
We have been making them for years.
The RSS kit comes with a wrench as well.
Feel free to contact us with questions.
Thanks.



We are also launching a new harmonic balanced underdrive pully for 3.8 next week. Here is a sneak peak at the prototype:

 

So what was BBI's rationale to go back to the stock size?

 

I suspect their goal was to extoll the benefits of reducing the rotational mass of the pulley as compared to the stock unit, at the same time negating the need to change out and retention the drive belt. Makes sense to me.

 

I could not agree more to the post above! Bryan was a tremendous help throughout the questioning process, shipping, and made sure a tech called me after the item was recieved to explain the installation process. Very well mannered and most importantly I noticed a difference in the way my car pulled. I look forward to ordering the EVOMSit software this up and coming week via RSS and than I will presume testing out these two new mods on the dyno. Once again, thanks bud.

 

Can You PM me the price of your UP ,I am interested
I am assuming it will work on a 2007 2.7 Liter correct? Thanks so much