This is part of an articles writen by the Saturn Race team guys.

"Because there were no pulleys available at the time, we went to the extreme and actually REMOVED the accessory drive belt (only for one run, of course) to see what the impact would be to ZERO drag due to the accessory drive – sort of pulleys with infinitely small diameters. We figured that if we saw a big gain without a belt, that the pulley gains would be somewhere inbetween, right?
We fired up the dyno and low and behold, removing the belt netted a whopping 3 HP (and we’re rounding UP). That's it. The number was repeatable, and even correlated to data run earlier on the doomed BMW motors - they saw similar results in their application.
So, in light of the fact that 3 HP was completely without a belt, we estimated that the best we could do was to underdrive a few components by 20% - or a theoretical 0.6 HP gain (3 HP x 0.2). After that, it hardly seemed worth it to try to custom fabricate pulleys for less than a 1 HP gain."

 

 

Huh? Let me get this straight- they "removed" the accessory drive belt, and I would guess, they ran a smaller belt directly from the crankshaft to the stock pulley. They did a pull on their dyno and saw a 3 hp gain, and doing some voodoo math, decided that a smaller diameter pulley would be of litte or no benefit. Now, granted, this is a saturn engine and not a MCS, but if the diameter of the pulley on the sc is the same, all things being equal, it would seem to me that their hp gains are from the loss of drag from the accessories, not from any change in sc rotor speed. Doesn't that just prove...nothing?

 

What is the point of an underdrive pulley ?

To *gain* HP by wasting less energy on dumb stuff - AC, Water Pump, Power Steering ( not on Coopers because of the Electric one ) Alternators etc...
Yes / No ?

If you remove the belt you are getting rid of ALL the parasitic energy suckers
Yes / No ?

This was NOT done on a MINI - but i would go out on a limb here and dare to say it might be close to the same thing on a MINI if all you could leave connected is the SC ( unless of course the loss attributed to those parasitic energy suckers is MUCH worse on the MINI than on the Saturn ) in which case the gain might be better ....

Hey - Some MINI owing Dyno guy - anyway you can run a similar test ?

The point was ( having purchased a Crank pulley myself ) what possible gains could be had by installing it ...
Two possible areas for HP gain -
1: underdrive the parasites ( minimal gain based on someone elses testing )
2: reduce the weight of the Harmonique Balancer ( TBD )

 

I like using Minows myself - or Crawdads... maybe some leeches...

 

Priceless!

Let the posts start flyin'...

Theo

 

The Butt- Dyno says it's .
I "think" I can feel it "spin" up easier ( less rotational mass)...time will tell if my engine pays the price. ..

Tons has been written on the topic...so do a search and decide w/ the available information.

 

Oh no...here we go again

 

ROFLMAO

The real news here is the fact that Saturn has a race team!!!




I'm gonna laught at that for weeks!!!

 

+1

 

Wow. Good luck with those windmills.

Oh, here's a link to where your proposed test was done:
http://store.webbmotorsports.com/ind...roducts_id=132

Search is your friend, this topic is not.

And now:

 

x2

 

I plan on doing to soon too. I read Randy's article and I think I might go for it.

Question: I would be doing an M7 16% SC pulley and M7 2% Crank pulley. Would this combo be safe to use "as is" or would I also NEED to get the "Alta Nator"? And do I also need a "Crank puller?" How do you remove the stock Crank pulley? Is there a special puller tool like the SC puller?

-Cody

 

This thread was started with the Idea that the Saving from Parasitic loss was *negligible* when changing to a different Crank pulley size -

NOT to argue the fact that changing to an different size would drive the SC faster and get more boost... even I won't argue with the Math on that one...

 

Cody, I'm thinking the exact same combo and questions. Michael

 

Is HP gain is the ultimate goal of underdrive accessory pulleys? The 1960s Cooper S had larger water pump and generator pulleys to compensate for the higher RPMs that the engine ran. It wasn't to save HP but to keep the battery from overcharging and the water from moving too quickly through the radiator.

 

I am running the combo you are talking about in my car. Have been for several thousand miles actually. I do not have the Altanator . The shop used a regular wheel /pully puller from what I could tell There was no real magic involved. Hope this helps a bit.

Randy
M7 Tuning

 

Thanks Randy. I just PM'd Peter about a question.

Let me know.

And Mistro, it's your's.
-Cody