Magnuson SC on 2014+ Sierra
 

If anyone has a 2014+ Sierra/Silverado 6.2L with a Magnuson supercharger, please read on to see if you can help me out.

I have a 2017 Sierra 6.2L with a Magnuson TVS1900. It came with an 84mm pulley, but only made 4psi of boost instead of the 6psi it was supposed to make. It also had a little bit of ping (not sure why, could be the bad CA 91 octane gas). Upon learning the boost was low and sending in an HPT data log, Magnuson immediately sent me a 78mm pulley. The boost was then right at 6psi (same amount of trace ping).

Out of curiosity, I installed a 2.8 inch (71.12mm) GripTec pulleyI had to see if the boost would go up and if the ping would increase. The drive belt was slipping off of the idler pulley pretty bad, so I took the pulley off without even driving it. This was with the Gates Century Series Micro-V K060938 6PK2385 (94.5 inches) belt that came with the supercharger.

Questions:
1) Does anyone with this same setup get 6psi of boost with the 84mm pulley?
2) If you get 6psi with the 84mm, what might have happened to prevent me from getting that boost?
3) What length belt are you running with your setup?

You don't have a signature listing your mods, is the engine completely stock other than the supercharger?

Search your belt number on this page and find one just a little smaller. Just remove the RPM from the end of the number to get a normal belt or add HD for a green belt.

https://assets.gates.com/content/dam...t-newbrand.pdf

Thanks. I'm in the process of doing just that.

Just an Elite Engineering E2X catch can at the beginning. I tested it with and without the catch can and nothing changed. I've since added an Alky Control system to stabilize the detonation at heavy throttle.

For sure. I already have a tentative 2.8inch pulley tune for when I get a smaller belt.
But to stay on topic, I want to know if anyone else has a 1900 Maggie on a 2014+ 6.2L making 6psi on an 84mm pulley.

Stock LSA pulley, around 75mm...makes between 6-7psi at 900ft elevation. Stock LS3 and LSA blower.

Like I mentioned in my thread, I'm using the 83m pulley on the SLP TCS1900 and making 9.5 PSI on average. The two other guys I know with the kit are running around the same, no less than 8.5 though.

I think I would first check to make sure your bypass valve is closing all the way

You're the reason I starting thinking about this and wrote the thread =)
I'll look into the bypass valve, thanks!