IPF Pulley Upgrade
 

Currently I have my supercharger off the car and the Pulley removed. After doing some math it looks like the pulley size is 3.8". Doing some math on the Vortech website with their V3 information and the a crank pulley size of 6" I came up with this (Boost Estimate is with a Ported Intake and 1-7/8" Tuned Length Headers (American Racing Headers):

Max RPM = 7300
Pulley size 3.8" = Impeller Speed: 41495. Estimated Boost: 9-10 (Confirmed)
Pulley size 3.6" = Impeller Speed: 43800. Estimated Boost: 10-11
Pulley size 3.48" = Impeller Speed: 45310. Estimated Boost: 11-12 (Tested 11-12 PSI)
Pulley size 3.40" = Impeller Speed: 46376. Estimated Boost: 12-13
Pulley size 3.33" = Impeller Speed: 47351. Estimated Boost: 13-14
Pulley size 3.25" = Impeller Speed: 48516. Estimated Boost: 14-15
Pulley size 3.125" = Impeller Speed: 50457. Estimated Boost: 15-16
Pulley size 3.00" = Impeller Speed: 52560. Estimated Boost: 16-17 (Non-Standard Vortech Pulley, Max Recommended)
Pulley size 2.87" = Impeller Speed: 54940. (Over speed)


The max impeller speed for the Vortech V3 SCi is 53000, so we are safe until 2.87" pulley.

How much of a boost gain should I expect from a 3.48" pulley? That will be 0.32" smaller. Car runs 18.5 degrees of timing with no knock retard on 90 degree days, so it should be able to handle just a hair more boost.

Said screw it and bought the 3.48" pulley. Once I replace all the bolts, belts, and paint on my supercharger I don't want to take it apart again. Will post on what the results are. I get it tomorrow but will be waiting for the new bolts though.

make sure your belt will fit, I had to go to the 061073 size, there is no shorter size close to that without getting real short. So if I pullied down, I may not get a belt that would fit. It would be too loose and cause slippage.

LLT is slightly smaller already, we use K061066 which is 107 1/8" long. Next size is K061058 which is 106 1/2". I think the stock belt should be good though, the tensioner had more room to work with. Will find out though, thankfully the wife's Mustang has 3.73 gears so it isn't as bad not driving my Camaro.

My big concern will be knocking, meth should take care of it though. I don't think Arno will tune for a smaller pulley.

:pop2:

Go for it!
Now we need an expert to tell us what a 9% increase in impeller speed translates to in boost. :pop2:

BTW- just thinking if belt length does present a problem- it looks like the idler pulleys are just 1.8" in diameter (5.65" in circumference). Could you take up a little slack going to a 2" idler if needed? :iono:

I've read that every 0.1" you lower you gain 1 psi. So I might be looking at 11-12 PSI since my exhaust flows well.

I thought about doing the idler pulley but with the bearing problems that cropped up I don't know if I trust any other idlers than the one IPF gives out. I know Vortech sells some, might look into it if the belt length is a problem.

Got the pulley today and came across the first problem, the Vortech 3.48" pulley has an offset while the IPF one does not. The alignment is off by a quarter inch, so I will need to find a spacer to put on the small end of the new one to get it to align the belts correctly.

Without a proper tune, won't you not be able to realize the full potential of more boost?

I'm no expert but I'd assume at high rpms you could experience a lean condition since you won't be getting more fuel. Are you planning to compensate with meth?

Not that I would know, but Magnum is already running meth, right? In theory he's fine... in theory though. Depends on how much fuel he has left at his current boost.

My current tune runs 11.5 - 12.0 AFR without meth, but some other tunes will run 10:1 since my car flows so well at low RPM that my LTFT's are positive. I can easily bring down the ratio one point with meth also. I've run the car at 13:1 and got my best trap speed from it. Majority of the detonation occurs near 5000 RPM's so that is the spot I will be watching at first.

Also, I'm running spark plugs that are 2 ranges colder, that will help with pre-ignition.

I will be taking it easy the first few times to make sure my AFR is good. Will also GoPro my gauges to review later. Hopefully by Saturday I can turn the car on and see how she likes the pulley.

Best of luck!!

First problem solved, took a dremel on a workstation and cut off a quarter inch of the offset side. All I have to do now is file just a small part of it to make it 100% flush with the old one.

IPF one on the left, new 3.48" on the right. Don't know why but it isn't this far apart in person.

It's just the angle. Looks good!