Not building boost with a KB2.8??

[griz_83ho]

So I have been battling this car for awhile and can't figure out what the deal is. Car has a stage 3 2.8kb blower I put on with 72lb injectors, etc.
Problem is the car is getting tuned by Lund and I have had it in the dyno twice and it is only registering 11lbs of boost on the factory gauge and makining 610 on the dyno. Question is what would cause the car to not make maximum boost of 19lbs with the 3in pully?? Also what vacuum line can I T into to get a boost reading?
Thanks

 

[HillbillyHotRod]

First off factory stock gauge is not all that accurate. I went with a manual boost gauge in a pod.

 

[54First]

Also what vacuum line can I T into to get a boost reading?
Thanks

The one that comes out under the front of the S/C and runs over to the fuel pressure sensor on the passenger fuel rail.

Steve

 

[nxhappy]

I doubt you are hitting 610whp with only 11 pounds. The stock gauge is inaccurate. Hook up a cheap manual boost gauge from Summit.

 

[griz_83ho]

That is the vacuum line I was using. Wired part is the dyno is showing no boost when we are Hooking into that vacuum line.
It's weird because it hits boost and jumps to 11 instantly and then holds. Wondering if I have something not adjusted 100% limiting the boost.

 

[54First]

I'm not familiar with a KB setup but I would think it has a bypass valve. If the bypass isn't closing, no boost happens. Your factory gauge is going to calculate something based on other parameters (it doesn't actually read boost, it calculates it). Therefore, the 11 lbs may not be for real. If the dyno gauge hooked to the vacuum line is showing zero I would think that's true.

Steve

 

[MattR]

KB had a bypass on the passenger side. I assume that's not sealing up tight. Or you have bad belt slip.

 

[Joewee500]

Have you overheated the KB? Mine hit 19lbs with 3"/10% combo that should have been 24lbs. Supercharger rebuilt as well as engine and now boost is 20lbs with 3.25"/10%. Also, car ran decent with the poorly performing set up to the tune of 740whp. Hope you find the problem.

 

[griz_83ho]

Just put a new gates greenback belt on it and by how fast it hits boost I feel like it's not slipping. The bypass was my next thought. It should flip the lever back towards to front of the car closing the valve when WOT correct?
Don't think the blower was ever over heated (although the son of a b---- is always hot)

 

[griz_83ho]

Post from the dead. Any other thoughts on this? It's weird because boost holds right at 11 or 12 and doesn't move

 

[nxhappy]

Post from the dead. Any other thoughts on this? It's weird because boost holds right at 11 or 12 and doesn't move

did you install an aftermarket boost gauge like we recommended?