I find it convenient and more accurate to talk about the pulleys in their physical measurement rather than the results. I don't know how it got started but there have been many posts wondering why "my 9 lb pulley only give me 8.4 lbs of boost."

Asking to buy a 9 lb pulley requires the manufacturer to do some calculations and they won't since they don't know your engine. They will just ask for a size. Only you know the parameters of your engine. Several things can change the boost while not changing the pulley size. Things like valve adjustment, headwork and final rpm. Are you redlining at 8000, 8300, 8900, 9200, or 9500 rpm?

I have been asked many times "what size pulley do I need for 9 lbs boost?" This is a very ambiguous question without further information, some of it unknown.

Let's refer to pulley size in inches and not psi. It is helpful to also mention redline and boost if you know it. That way, everybody will be on the same page.

Example: My Vortech was pushing 13.4 psi at 9250 rpm with a 4 inch pulley.

 

Anybody else want to chime in on this?

 

Sounds good sideways

My Vortech was pushing 7.5 psi at 8900 with 5 inch pulley =)

 

Slightly off-topic guys, but still related -

I've got the standard comptech kit for MY02/03 with aftercooler. I went for it since European cars maintained the 2.0 litre engine for 04/05/06. I've also got a set of blitz electronic gauges with separate control unit. Location of the boost sensor is via T-connector next to the intake plenum but not connected to the fpr. I'm using shitty 95ron/85mon petrol since it's the only gas available in this country. Now I keep hearing that the comptech kit for the f20c produces 5.5psi and about 5psi with aftercooler. My boost gauge consistently registers 0.4 bar or 5.8psi in imperial.

Dpes anyone know if it's possible? Is my gauge reading too high or are there any other comptech users with similar numbers? Thanks

 

Gauges tend to read high. Put it on a dyno and see what pressures you acheve.

 

Looks like Sideways is up early - getting ready for CC?

I have family down there - are you there pretty much every weekend Sideways?

 

A very nice write-up Sideways! I have been thinking the same thing for quite some time - perhaps posts should be a bit more informative of pulley size compared to psi amount!

Using a Comptech Supercharger with Aftercooler : tuner says he saw a total of 9.75psi @ 9200 rpms using a 3.25" Pulley. The reading was taken from the manifold. Unfortunately it had been a very humid week - he did state he expected another 1 - 1.5psi under cooler conditions.

 

O cool I wanna play!! Mine pushes 16.2 psi at 9350 rpms and is a 3.8 inch pulley

 

Mine does 8lbs. with SOS 10lb.(3.5") pulley. I get 350whp at 8700rpm. I bet I could get 375 at 9300rpm.

 

my does 11.5lbs at 8900 rpm with the 3.5 asp pulley.