Whipple boost vs pulley size

[FstdodgeKY]

So I've been looking around and seems that what I'm seeing as far as boost levels go I'm not getting as much as I should be so I'm asking to see what everyone else is getting and pulley combos.
Charger 6.4
Forged with cam.
2.875 Upper
6%OD ATI lower
6.78
This equals 15378rpm at the blower if math is correct at 6500rpm. I'm only seeing a max of 12# of boost with this combo and I've seen others making much more with less pulley, or am I missing something?? Also no sign of pulley slip in the logs, hold right at upper 11.8 through the whole pull. Thanks

[white1]

A rough estimate is 2psi per 1/4" reduction in pulley size. Generally, if you are not close to that you are experiencing belt slip

[FstdodgeKY]

How is everyone logging boost?? I've did the custom math. Map-14.7(baro)=boost. I'm guessing that its belt slip but never here any or see any deviation in the logs

[white1]

Using the Map sensor. Anything above 100KPA, or 14.7psi is boost (if you scale it in PSI)

[ramdart74]

AEM boost gauge connected to one of the data line using pro link.

[FstdodgeKY]

So everything looks normal. Guess its just not making the boost compared to everyone else, or its belt slip (don't here or see any on logs) just odd i think it only makes 12# with the pulley combo.
A friend making 20# with 3.0 pulley but she is on a 10 rib setup. Its still makes good power @840 when you punch the numbers.

[rays04gtx]

I don't deal a lot with boost in my life, so understand my personal experience is limited.
My builder doesn't bother with the rib set ups , the few boosted stuff he builds it's cog , I asked once why, his response was , Rib systems always slip, the higher the PSI the higher to potential, you just can't keep enough tension on the belt.
one day I was at the shop he rents chassis dyno time, two Lightning trucks back to back an 04 and an 03 the 1st truck made 70hp more , same size pulleys (6lb pulley) same cams difference was the 1st truck had cog set up on it.
He was working on a 07 Ram, with a 2.9 Whipple talked the owner in to going cog, he picked up 40hp off the bat@6500 rpms, then after re-tuning it , that added another 30hp

I mean no disrespect , but with rib systems you get slip , how often do you change the belt ?

[Dave401Redeye]

I don't deal a lot with boost in my life, so understand my personal experience is limited.
My builder doesn't bother with the rib set ups , the few boosted stuff he builds it's cog , I asked once why, his response was , Rib systems always slip, the higher the PSI the higher to potential, you just can't keep enough tension on the belt.
one day I was at the shop he rents chassis dyno time, two Lightning trucks back to back an 04 and an 03 the 1st truck made 70hp more , same size pulleys (6lb pulley) same cams difference was the 1st truck had cog set up on it.
He was working on a 07 Ram, with a 2.9 Whipple talked the owner in to going cog, he picked up 40hp off the bat@6500 rpms, then after re-tuning it , that added another 30hp

I mean no disrespect , but with rib systems you get slip , how often do you change the belt ?

I have seen several post about about a cog style belt works good on the old 6-71 and 8-71 blowers. But every cog setup tried on a Hellcat has caused major blower damage. The cog style belt probably does not slip but belt stretch and recoil must cause the rotors or possibly the bearings to fail.

[rays04gtx]

I have seen several post about about a cog style belt works good on the old 6-71 and 8-71 blowers. But every cog setup tried on a Hellcat has caused major blower damage. The cog style belt probably does not slip but belt stretch and recoil must cause the rotors or possibly the bearings to fail.

Not every one,