03sierraslt

iTrader: (22)

you are right, I was think of something else. The valve should be normally closed. Either way it shouldn’t be effected my a evap leak. Just unhook the vac ref and leave the valve closed and test it. Just don’t leave it this way for a long period as it will run hot.

Mileguru

And we have a winner! The simplest answer was the correct one. A bit of Occam's Razor for ya. Only it wasn't my math that was off, it was Magnuson's. And I was measuring boost through HP Tuners (what is it, Intake Manifold Absolute Pressure -minus- 14.4?). Magnuson finally let me know that they made a mistake and should have never given me the 84mm pulley in the first place to make the advertised 6psi. They said that an 84mm on a 6.2L indeed only makes 4psi and the 78mm makes the 6psi. They could have just told me that a LONG time ago when I asked. And here I was wondering what was wrong with my particular truck or the supercharger install.

They went on to say that for a 5.3L with a TVS1900, an 87mm makes 6.5psi and an 83 would make somewhere between 8.5-10psi (which is the pulley and psi boost that the SLP 1900 kit has for the 5.3L).

I can't help but wonder, what's the difference in FEELING, power, and 0-60mph between a 6.2L crew cab with the 78mm (6psi) and 5.3L crew cab with the 87mm (6.5psi) or even the 83mm (8.5-10psi). And does the 6.2L with the 78mm end up being an inferior choice to a 5.3L with an 83mm because the 78mm is going to spin much faster and heat up much quicker...?

Atomic

iTrader: (42)

With a blower, the air its moving determines everything, not really the engine size. But I will be honest, I have never seen someone get so torn up about 2psi before

Mileguru

Funny, but it was primarily a concern that something was wrong with my truck since Magnuson said I should be getting 6psi with the kit when I bought the SC kit. A 2psi is a big difference when you're talking 4 versus 6. I was only getting 66% of what I was supposed to get and the truck was noticeably weak. Not what I paid for, that's for sure. But they fixed it and finally explained it was their mistake and not my truck, so all is good.

lxcoupe

iTrader: (9)

06 Colorado ZQ8 T56, 3580lbs
TVS2300, LS2 t/b
3.4" pulley, stock truck balancer
L33 5.3L, LS6 cam
1 3/4" longtubes, 2.5" true duals
E85

Makes ~10.8-11.3psi
630whp/555wtq

Merlin1

To revive once again:

02’ reg cab silverado 4wd
LM7 5.3l
Forged Internals
Kooks headers 1-7/8”
243 heads
120# Holley Injectors
92mm Nick Williams TB
Holley Dominator
10% OD
3.8” Griptec
D1x Procharger
E85
23psi at 6900 rpm’s

Obi

This is extremely helpful, thank you

By any chance could you explain the effect of changing pulley sizes while pulley ratio remains the same? The excel sim shows that increasing the pulley sizes while the ratio is held the same decreases the belt load (lb). Would that impact performance?

Example: Would you prefer Set A or Set B?

Set A: Crank 6in, sc 2.5in
Set B: Crank 6.96in, sc 2.9in

MikeGyver

iTrader: (5)

Set B. Longer belt life and less chance of slip. Better performance if the belt isn't slipping.

Obi

Thank you for the response and reasoning. What if the sc pulley was coated in griptec and slip wasn’t an issue? And by any chance do you know if belt load (lb) affects performance?

Atomic

iTrader: (42)

The formula I had in there for belt load is essentially [SC HP / (RPM * Crank Diameter)] with some unit conversions in there. So as crank diameter gets bigger belt load would go down even for the same pulley ratio. Not sure why exactly, I made this a long time ago lol