Hello
With my latest adventure into supercharging I stumbled across a couple of formulas on how to determine boost. So I put them into a spread sheet to make simple.

id like you folks to try it out and see how far off and/or inaccurate it is to the real world.


http://spreadsheets.google.com/pub?k...MSw&output=xls

Notes to bear in mind:
- This is NOT hyper accurate. There are too many variables to make a real world unit. I made this more for fun and as a guideline.
- Im not a math guy. any counting above 11 and I get confused I just copied the formulas over from another site.
- Its in an Excel format so you will need Office installed.
-I know NOGTHING about excel so this was more of a learning exercise for me and a challenge. So it may not be very clean. I welcome feed back.
- Blower Step Up Ratio for Vortech's were estimated. Prochargers were listed on their site.
- All Blower Specs were from the manufacture site (what I could find), so of course they would never lie or exaggerate.
- S/C Peak Efficiency for Prochargers were guessimatated based on Vortech units and a WAG (Wild A$$ Guess).

Directions
Dl the file.
I gave 3 examples of each S/C. If you want to do more just use the chart on the bottom of the spread sheet to copy over the; Blower setup ratio, MAX RPM Blower Speed, MAX CFM of blower, and S/C peak Eff for the unit you want.

Input the following data
Crank Pulley Diameter: 8 if you have a over sized unit (dont we all). this is common for most 8 Rib setups. Or the factory diameter is 7.5 (some one please confirm with me)

Blower Pulley Diameter: the pulley size on your Supercharger.
Engine RPM: what your red line Max RPM will be.
Engine CI: how many Cubic Inches you have.

Forum Members feedback
id like to make this better, so If im missing something or I have an incorrect number please let me know.
Im curious to see what you folks get in the formula versus what you get on your cars. how far off is it?
I cannot stress that this is a guideline only. the boost will drop depending on the efficiency of the TOTAL system. for example bends in the pipe, and an inner cooler will change the outcome.

cheers
Chad

 

Chad,

I'm interested I will have to try it later - perhaps at work

Thanks,Matt

 

what are the #'s in red? There's a number under estimate and then there's S/C (is that the abadiatic efficiency rating??) then the number in red. The estimate is higher than my real boost by 3# and the number in red is 1.5# low. Pretty cool.

 

Speaking of boost, where are you at with your build???

 

ok good question..

you may have to take row 1 and expand it a bit to see all of the lettering.

ESTIMATED BOOST
from my understanding this is how much boost you car would make if everything worked at 100% Efficiency, and the car was in outer space. Meaning, no change for temp, engine compression ratio, attatlude, piping or inter cooler.

BOOST in red
that was an after thought that; at MAX RPM the supercharger operates at XX% efficiency. Please some one correct me if im wrong. Just a guess. I used the abadiatic efficiency rating listed from the manfacture website.
SO I took the ESTIMATED BOOST number muplied by the Abadiatic efficiency rating to equil the BOOST number in Red.

 

thank you for asking

another round of head gaskets are going on. first one had a tiny leek
then I only have the following
-second no movement break in cycle.
-putting on a "street" drivability tune.
-getting feed back from the tuner of 'just how much' my fuel system is lacking.
-then buying a Boost a Pump ($300), OR dual pumps with piping ($1100)
-Installing the fuel system
-breaking in the engine/clutch for 500 +/- miles and 'shake down'
-Dyno tune

-then pay the bill.

engine **** shot


.. now back to out regularly scheduled programming.

 

will have to check this out at home

 

 

T-Trim 8 3.8 3.45 6700 55000 1200 1061.741627 346 670.775463 1.582856985 23.26799768 8.567997677 73.% 6.254638304

Actual boost is around 12psi in 75* weather.

 

..wow way off...
cool thank you..
keep them comming.
id like to know if this tool has ANY value.

 

Unless you're only running 5psi boost, I'll bet you're going to need the fuel system upgrade.
What trim blower do you have?

 

ill have twin 66mm turbos soon. do they count?? LOL

Ill have to check that out more at home.

 

Says my max boost is 8.4 with a D1SC stock crank pulley 3.85 SC pulley and stroker 395

I actually see max 12.5

 

wow to be honest I had a hunch that the caculator on this would Over estimate the boost but there are 2 cars here that have shown the caculator is Under estimating.

hmmm a puzzle..
..I like puzzels.

Buldogg, what is the compression ratio of your engine? headers?

just courious
thx.

 

I appreciate you trying to help, however, I believe there are too many variables to make anything meaningful. I have a 416" with 9.2 C/R and a stock crank diameter pulley and a 3.75" on a D1sc, it makes 15psi @ 6600 rpm 858rwhp

 

Yea i hear ya, but it was worth a shot. yaknowwhatimean

 

P1SC-1 7.5 4.25 4.1 6800 65000 1200 1100 402 790.9722222 1.390693591 20.44319579 5.743195786 73.% 4.192532924

My actual is between 4-4.5 psi