rightio hello all and i am after some information please

i have supercharged my 2.2 so does anyone know what psi i am running with a 2.8 pulley? and how much will i be running with a 2.7?

does the supercharger snout have to be machined for a 2.7 or does it fit straight on?

those questions are just for curiosity really!

right now for the main thread question i have been looking at overdrie and underdrive crank pulleys but which is the best one for the supercharged 2.2

many thanks

Joe

 

Most 2.7's and under you have to machine the snout. The smaller you go, the more needed.

For s/c applications you want either stock or overdrive. If you under drive it'll will have the reverse effect on the s/c pulley and make it act as a larger pulley.

Don't know on boost.

 

if you have supercharged your 2.2L why not just look at the gauge?

also 2.7 is the smallest you can go on the GM hub. 2.6 will fit with smaller hub but some pulley rings require the snout to be machined

I am on a 2.7 and make roughly 17-18 psi, but that s with full 3" exhaust

 

Yep going underdrive would just make the supercharger work harder with no real gain.

If you want to go overdrive, but keep the same supercharger pulley ratio, you can use this:

(crank pulley x engine rpm) / sc pulley = sc rpm

Once you find your sc rpm, you can plug that into a new formula to determine what size sc pulley you would need to go with in order to keep the same ratio after installing your overdrive pulley.

To determine sc pulley size:

(crank pulley x engine rpm) / sc rpm = sc pulley

//////////////////////

In your case the stock crank pulley diameter is 6.5", the pulley you are running is 2.8" (?), and I'll go ahead and assume a redline of 6500rpm.

Stock crank (6.5):

(6.5 x 6500) / 2.8 = 15089rpm

Overdrive (7.125"):

(7.125 x 6500) / 15089rpm = 3.07"

So you would need to bump up to a 3.07" pulley in order to keep the same ratio if you went up to a 7.125" crank pulley.

The overdrive size comes from taking the difference between the stock pulley and MRZ's UDP, and simply adding it to the stock size instead of subtracting. I'm sure they could make something like this if it were requested.

MRZ Performance: http://mrzperformance.vstore.ca/prod...roducts_id/144

Note that you will likely need a new serpentine belt in order to accommodate the change in size.

Just for kicks, this is what your effective pulley size would be if you ONLY did an overdrive pulley:

(7.125 x 6500) / 2.8 = 16540
(6.5 x 6500) / 16540 = 2.55"

 

leave your crank pulley alone, the can cause crank walk and will eat up the oil seal and bearings

 

Yep all that mess above JapEatr's post essentially points to one simple fact: Just change s/c pullies, lol.

 

Agree leave the crank pulley the way it is and down size pullies

 

Thanks for the information, so overdrive is the way.

I gave a lighted flywheel and balance delete so changig the crank pulley is a must really as I want to save more rotational weight.

So if I have a overdrive pulley what one should I get? Currently have a 2.8 pulley on but don't mind changing to get a 2.7 and get a smaller crank pulley aswell to gain more power.

Or should I just get a smaller pulley and same size crank pulley but just a lighter one!?

Thanks all for your help

 

Lightweight stock crank. You'll find one in the link I posted above.

 

I was told the crank was internally balanced so it wasn't a big deal if you messed with the crank pulley