1990 Mustang GT Super Charger Question
 

Hi Guys,

Just hoping to get some answers.

I have a 1990 Mustang GT with the 5.0L and I have added GT40 Intake and Heads. I have also added a Powerdyne Super charger.

The question I have is that I could only pump out 4-5lbs of boost. Supposedly it should pump out 8lbs.

Would an Under Drive Pully Kit cause this?? Since I have that istalled also.

Or Could it be that the GT40 Intake and Heads give no resistance??

Just wondering. I have had this problem since it was first installed.

I know I am just grasping for straws but any help would be greatly appreciated.

Thanks in Advance
Peter

Could be the belt slipping. Common issue in this type of application.

I am sure it is a minor issue and shortly you will have many educated replies-good luck

That is the problem... An underdrive pulley slows down the speed of your accessories, one of which is the blower.

I missed that. That would cause your issue for sure.

Remove the pulley and you'll be golden.

So do you mean to put all the original pully back on?

or

Do mean, put a smaller pully on the Super Charger

Thanks
Peter

I am a big fan of stock, other guys not so much. New answers coming shortly lol

Ditch your underdrive pulleys and go back to stock. Once you know where you are at you can look into a smaller blower pulley to get even more out of it if you choose.

If you want more power through pullies, throw the underdrives in the garbage and put a bigger crank pully on (overspeeds the blower), or a smaller blower pully on (overspeeds the blower).

Thanks for all the advise.

I was just wondering, it is easier to just change the blower pully but is there a maximum RPM the blower can spin??

I don't just want to add a smaller pully and find out it blows my blower due to high revs.

Thanks
Peter

your acessary pulleys have nothing to do with boost , because the blower belt is seperate from the others . The Powerdyne is rated 8# for stock engine with more restriction

Someone correct me if I'm wrong, but smaller pulley LESS boost larger pulley more boost.
The reason for under size pulleys are to turn you accessories slower therefore putting more power through to the wheels. Your supercharger is an accessory a small pulley turns it slower.
Put the stock pulley back on and you,ll be up around 8lbs.

The smaller the pulley is, the faster the supercharger will spin creating more boost.

I understand what 351turbo is saying.

The Powerdyne pulleys work on there own. The drive pulley (bigger one) is attached to the Crank Pulley (just in front of it). It doesn't use the Crank Pulley what so ever other than being bolted on to it so it can be rotated.
So the Crank Pulley, when it does one revolution rotates that same as the bigger Pulley of my Supercharger. It doesn't matter what size the pulley is (the crank pulley). It still does one revolution. Now if the Supercharger pulley ran off of the Crank Pulley (same belt) then changing the size would make a difference.

So removing the under drive pulley's doesn't change the rotation between my 2 pulleys that run my supercharger. It has its own belt.

I THINK I purchased the 6psi kit (garage that installed it is no longer in business) for the Normal Mustang. Because my intake and exhaust has been modified with a GT40 intake and heads and with a Mac Long Tube Header and Exhaust. Also with a E303 Cam, then the air restriction is less causing my Boost to only hit just over 4psi.

I have come to the conclusion that I need a smaller pulley at the supercharger. Now what size I need?? I don't know.

pserra

Hey 351Turbo and ChadStang,

Hey 351Turbo,

If I have a #6 Pulley would you know what size it is??

Would you even know what size the #8 Pulley would be??

Just looking for answers. I can measure my pulley but I wouldn't know if it is a #6 or #8. On my receipt it says a #6 (meaning 6psi pulley, i would assume).

Hey ChadStang,

We must have been replying the same time I just hit submit reply a few minutes after you. If I were to put a smaller pulley on the Supercharge yes I would agree that it would increase my boost.
But just how small of a pulley can I go??

pserra

ChadStang
I assume your talking about blower pulley I'm talking crank pulley.
Smaller pulley on crank = less boost

I'm lost, no surprise lol

ChadStang;

Are you talking the Crank pulley that turns my accessories or the Crank Pulley that turns my Supercharger?? They are different. The Crank Pulley that turns my accessories, doesn't matter what size it is. Smaller or Bigger doesn't affect the rotation of the Crank Pulley that turns my Supercharger. If you mean the Crank Pulley that turns my supercharger then I agree with you 100%.

Smaller Supercharger Crank Pulley means low Boost or Bigger Supercharger Crank Pulley means more Boost.

Hey Chad lol

That is correct, I didn't read from the start of the thread. Sorry about that.

As I mentioned I didn't read from the start. I was talking about the pulley that is on the supercharger itself.

That's straightened out lol

Yeah talk about shoving your foot in your mouth. Note to self, read the start of the thread before commenting.

I wish I could do 1/1000th of what some guys do mechanically to their cars just like computers, oh well

Not a problem. We all tasted our feet at one time or another.

Thanks everyone for your advise.

Peter

What size crank pulley and blower pulley are you running now? 6 or 8 rib? I had a vortech sc trim that was a 5-6 pound kit with a 6" crank and 3.33 upper 6 rib. To get it to 8-9 I put a 8 rib 6.87 crank and 3.12 upper.