Im at 17k.

I also hear **** rattling around when driving and my exhaust tone got drastically deeper. I wish we could gut the cat easily!!

 

-I remember seeing around 22 PSI over the winter (around -10 degrees) with a 2.6 pulley at see level.

-I remember seeing 19 PSI over the summer (around 80 degrees) with a 2.6 pulley at see level.

-Now at 3500+ feet elevation with this current temp (around 60 degrees) with a 2.6 pulley I see somewhere between 15-16 PSI.

-Tomorrow I'll downgrade to a 2.9" pulley which hopefully will bring it back to a more efficient range (maybe 12-13 PSI at this 3500+ elevation). I had IAT2's soooo high with that 2.6 pulley while cruising. To me anything below a 2.8" pulley without methanol is not very efficient.

The important thing to remind is how high your IAT2 are. It's better to keep them below 150-160 degrees otherwise the PCM pulls timing and add more fuel ...

The true pressure ratio of compressed air is measured with air pressure AND air temperature. The highest the temperature of the compressed air, the lowest effective pressure ratio is.

Also, boosting too much PSI in the intake manifold requires larger fuel injectors, because in that case the differential pressure between the fuel rail and the intake manifold is lower, causing the injectors to flow less. (Fuel rail pressure is constant).

 

I run a 2.8 and 23 degrees of timing in the dead of summer w/o going over 160. Dual pass FTW!!

I think another important lesson is that catless downpipes are the way to go.

 

21.5 i saw this morning it was 50 outside

 

Not to hijack the thread, but does anyone know which downpipe will fit the GMPP extruded manifold and the GMPP catback, if any?

 

ZZP and Vibrant.