:confused: I can't even begin to understand how to read this lol

Pressure ratio on the compressor maps refers to the ratio of boost+atmosphere over atmosphere. so 1.0 on the map is ambient air pressure 14.7 + 0/14.7 or 1.0

so in terms of boost pressure:
1.0 = 0psi
1.5 = 7.3psi
2.0 = 14.7psi
2.5 = 22.0psi
3.0 = 29.3psi
etc

So if the 88mm pulley produces 11-12 PSI, you are at 1.5 to 2.0 Pressure Ratio, so for the c38-81 you are in the middle of the Compressor map just below the 70k line.

On the c38-91/92 compressor map you are at a similar spot but by the looks of it, the c38-91/92 compressor actually has a lower top spinning rate where the 81 can go a bit farther.

I think so, I am doing the math at all RPM's at all the pulley sizes. It may take some time.

Compressor Max Pressure
On the map, find the top-most point on the graph. The vertical coordinate is the max pressure ratio. For example, 2.8 pressure ratio at sea level is 1.8 times the atmospheric pressure, 1.8x14.7psi=26.46 psi.
Compressor max pressure is limited by compressor wheel speed. It's physically impossible to boost higher than this max pressure for one particular turbo. Plus the pressure drop in the intercooler system, the actual max boost reading from a boost gauge that's plugged into the intake manifolds maybe a few psi lower than this max pressure.

Yes, PR of 2.0=14.7 PSI of boost that is at the compressor outlet and very hot. You loose some of that as pressure drop across the intercooler.
More as the volume shrinks when the are is cooled by the intercooler.

So would the airflow at the bottom be rpm ? And since I'm running the 38-91 84mm would be the lowest I should go if I'm understanding the chart

Now that's a chart I can read lol that helps a lot .....so for the stage 1.5 charger the 84 would be best IMO. ANd for the stage two 88mm would be best IMO

I did find this 159-99-8507 - Pulleys - Performance / Accessories - KraftWerks USA
It's a 85mm with 6 bolt pattern for 85 bucks that might work out for my situation Any thoughts ?

I think so, I hate math. You can apply all the numbers to the 38-91 rotrex (stage 2) as well. I still need to do the math for the 82mm pulley I have. I just do not run to 7500RPM the motor might pop!

There are some Dyno charts with the 84mm ran to 7500 .... And was at like 523 hp ... I'm thinking I could use the 85mm .... I don't like running high rpms so 6k-6.5k I feel better at

No dyno near me, sorry

I ran the upgraded stage 1.0 to a stage 1.5 with meth injection to 640 WHP and the 84mm pulley. Ran around 12 lbs of boost. Unfortunately, I have no proof and no record of it. The supercharger has since been removed and sold.

On to the next project :tup:

How hard is the install going from the 1.0 to 1.5?
I should have "all" the new pieces which include, 2 new intake pipes, intake filter pipe (I believe?), 1 engine mount, and a few accessories to re-route PS line.

Anything else I am missing or should know?

Yes I remember how much of a pain it was to remove the stage 1 intake pipe.
Recommend the you drain all the oil out of the supercharger before doing that job.

Oh that is already done, both steps.
My SC seized because we lost all the oil for it. :(

Do you have the 1.5-SC housing, I have a spare,

What injector are you running, 650cc or larger.

If you need the PS parts, I have a full kit, and the Fuel Pump voltage kit I'll make you a super deal.

I can mod your base tune to work any injectors, If you stay with the 600cc injectors you may run lean and pop the motor. Do you have WB O2?