For those that weren't aware, we have a Techinfo article that answers alot of questions:

http://www.bonnevilleclub.com/techinfo/?article=50

this is a Q/A session I cornered Pulley Boys into for us. Brian was more than happy to help.

Some of the questions or 'not sures' in that article have been answered since then. This threads purpose is to point out this article, and answer any questions you may have on the topic.

boooooooooooooost yeah baby does it make you randy?? lmao

Whats Boost???

That is a great article, as usual. That should be very helpful for a number of people.

Shawn

Well, I shall have to get myself one of those new pulleys!

My buddy'* brother actually works for the GM test dept. He has ummm aquired 3 of the orginal test mules for GM. The dyno test mules were for the original concept of the Trans AM 3.8 . I can tell you that the " baddest " one they tried was a 2.5 inch pulley. I know I measured it today with a micrometer. His Dad, who was engineer there, say'* the smaller pulley would cause too much heat and wear the blowers out so they dumped them. Now this may be after 150k I don't know... I've never tried to switch them.Just food for thought.


JLathem

Also, dbtk2 you state the boost numbers above with quater mile times. How the heck did you get 15 PSI boost out of the Eaton ? I know they are engineered for more than the OEM 9 or 10. I'm just curious how you got it up there.

JLathem

Boost is the pressure built in the manifold. You can get higher boost numbers by putting smaller pullies on the supercharger so it spins faster, or by restricting the exhaust. High boost is not always an indication of power and often times will cause the engine to heat to a point of knock induction.

Horsepower is made by pumping air through the engine. The beter the breathability of the motor, the more HP it makes. The sweet spot of the M90 is around 10-12 lbs of boost, anything more and your likely creating more heat and KR than your gaining from the added air. By freeing up the restrictions in the motor (headers, cam, heads, exhaust work, etc..) you will actually lower your boost numbers because the pressure in the manifold is not as great. Your not making any less power, your boost numbers are just lower. This usually means you can "pulley down" on your supercharger and get the boost back up to 10-11 for even more power.

Yet with an intercooler, you will see people running over 12lbs of boost. Even though there is no KR because of the I/C, would the boost be stacked if you haven't done much work to the heads or valvetrain?

You can run higher amounts of boost with an intercooler because of the cooling effect. Even with an IC though you will have maximum amount of boost you can run. For example lets say that the same car without an IC can run a 3.2 pulley (talking series 2 here, series 1 sill be different dimensions) and create 12lb of boost with no KR. The same car with an IC may be able to run a 2.8 creating 16lb of boost with no KR. The IC'd version will be faster and more horsepower however by doing headwork or cam or rockers or exhaust you could get that down to maybe 10lb of boost and go down to a 2.6 pulley briging it back up to 12-14 for more power.

The concept is the same, an intercooler will just let you pulley down further and faster while being less apt to crush the motor under so much boost. The IC will give you a greater maximum boost level per mod than a non-IC car.