Upper pulley size

[ObiZLWan]

Has anyone ran just an upper supercharger pulley? If so what size? Do you need a tune? I see a lot of packages with lower balancer pulley but not supercharger pulley.

[JBZL1]

Most people don't change the top pulley as there's more work involved. You have to remove the SC to remove the nose/inlet and press the pulley off and new one on. I have done a 2.85 on the upper and ported the inlet at the same time. But the main thing is I had a hub pressed on so I can swap pulleys in the future without removing the SC. Lots of CTSV owners have been swapping a 2.55 /roto fab intake and tune and calling it a day without going bigger injectors. From what I've read the stock injectors are maxed at that point but only your tuner can tell you that, it also brings to question on adding a larger heat exchanger /160 tstat and intercooler reservoir as well. There are many opinions on this but the tune is key as to where your injector duty cycle is at after 2.55" install. Plus adding boost is going to make heat like a steam engine and it must be addressed to get the most out of your mods

[Can'tHave2MuchHP]

There's a few different sizes for the upper pulley, and yes they're very commonly changed: 2.55", 2.38" (Sometimes called the 2.4), and I think there's a 2.31 from somebody. Yes you're going to need a tune no matter what you change. And not just a handheld box like the mustangs.

Anything past 10% overdrive on the supercharger requires bigger injectors, heck sometimes people can't even get 10% overdrive without changing injectors, it varies by car. I know there's a lot of people that run 18% overdrive (2.55" upper only) on stock injectors, let me just state fact: They're Crazy. You'd be well past 100% injector duty cycle at that point, any skipped beat by the fuel system can be big problems, you don't want that. Spend a little more money (800-1000$) and get a set of injectors.

A 2.55 is 18% overdrive, 2.38 is....Let me just give you a chart:



Basically, go big or go home. Change the injectors, or don't pulley. You choose.

If I were you and you're looking for a bolt on build:

2.55" upper and a 8.6" Lower (Or a 10" lower only) or you can stay lower and just do like a 9.1" or 9.55", less boost = less heat = less need for upgrades/cam.
ID850 injectors
Long tube headers
Air intake (Which you have)
Catch can (Which you have)
Heat exchanger upgrade
160* thermostat (Debatable)
Tune on 93.

Then if you want you can add a cam to that later. You should be in the 600-620 RWHP range with the above on 93. Adding a cam can get you 650WHP and more. Here's another thing to consider...You can only run so much boost before it's basically being sent out the exhaust. After I think Ted says 12-13 PSI? You're basically wasting it and just building excess heat that you don't need, and you need a cam to make use of it. That's another thing to consider.

Talk to some shops and ask questions .

[STUNNAH]

Originally Posted by ObiZLWan

Has anyone ran just an upper supercharger pulley? If so what size? Do you need a tune? I see a lot of packages with lower balancer pulley but not supercharger pulley.

I'm one of the few that runs a 2.55 upper pulley...Simple stage I kit results in sig. no fueling issues...One of the benefits of running a upper pulley is that you can have the isolator swapped out and port the snout at that time...My car is otherwise stock and runs a hell of a lot smoother than pre upgrades...

[ObiZLWan]

Thank you so much for the info guys!