Wades SnS

iTrader: (2)

I a 246/254 .598/.598 112LSA 108CL custom ground cam in a 385ci engine with ported heads and would like to know what my MAP should read before startup and at idle. I have noticed that my map is at 14.9 psi when in KOEO and goes to 10.6 at 1150rpms when at idle. It seems as if there should be no vaccum when in KOEO why do I have 14.9psi? Also have noticed that after tuning my ve table the values at idle are around 49 and at 3200rpms is at 62-64 Is this normal? It seems like these values are way low for my setup. I am also having a p0106 Map sensor performance code. I have changed the sensor and still same thing. I know that I can tweek the table for the cam but I had previously tuned this same engine on a 2000 OS with no issues. I am now running the 2002 OS. Please help!

Thanks,
..RJ..

5.3LJimmy

iTrader: (10)

The 2000 OS has the P0106 code disabled with no error reported, while the 2002 OS does not. You can either disable the code or raise the MAP sensor max Kpa threshold to stop the code. The MAP reading is higher due to the loss of vacuum and the higher idle speed causing the DTC to set. Atmospheric pressure is 14.5PSI(100Kpa) at 0 degrees C, so I would say that the 14.9 while not running is correct. The 10.6 PSI at idle converts to 73Kpa and that looks right to me for the cam size and idle speed. I'm not sure what your VE should be, but I would not expect the engine to be all that efficient below 4000RPM's. Hopefully someone else will chime in that can better answer that question for you.

xpndbl3

iTrader: (23)

it's not vacuum inHg it's pressure in psia

you'd need a conversion chart to show the difference.