4PSI pulley pushing 7.5psi

[SC V6]

I dunno whats going on.. i have a JPP headers, y-pipe, and 3 inch exhaust, w\ no cat, and I AM STILL SEEING 7 PSI at the end of my gear... it stays at 4 psi till I hit about 5200rpm's then it starts to spike, I thought that it was my Cat being clogged... but its still doing it.. why would this be happening??? I thought it could be that the line could be pinched, but why would it spike like that????

[xtychx]

Everyones s/c's seem to do this. I surmise it is related to temperature. Temperature is proportional to pressure, so as the temperature inside the blower climbs, so does the pressure, which registers as boost. The M62 blower used in our application does not have the best adiabatic efficiency. I would recommend a water injection kit shooting straight into the manifold to cool down the discharge temps and increase power while getting rid of the spiking.

-xtychx

[SC V6]

its just annoying... because it will stay at 4 psi, then when it hits about 5200rpms it starts to spike... and I hate it, I don't want to blow a motor over this... would water injection completly get rid of spiking?

[xtychx]

Yes it is rather annoying but I would not worry about it. At 4psi the risk of detonation with your setup is nearly 0%. You need to understand that the 7.5 PSI is not real boost realized in the cylinder, it is only a reading from the manifold. On cold days, my boost reading goes to 11.5 with my pulley! The reason it starts to spike at 5200 is because of the thermal efficiency of which I previously noted. Some superchargers with poor adiabatic efficiency heat the air inside the manifold to a great degree once a certain lobe RPM is reached within the actual supercharger housing. This heating of the air raises the pressure, causing the false boost reading. Water injection will greater lower the discharge temperature inside the manifold, and with a well sized nozzle it will almost certainly reduce and eliminate the boost spiking. Scott, if you want to talk further, my AIM is "xenoturkey". I would be glad to help you out.

-xtychx

[SC V6]

could it be from running too rich at the end of my gear? because I took my cat out and it only spiked to 4.5 after that, till I did a fuel upgrade, now its spiking again.. could it be too rich?