Hopefully this will stay in the FI section.
I am trying to figure out how to read a compressor map and how it relates to sizing selection.

TIA,
Charlie

 

TTT it is confusing for me too.

 

www.smokemup.com has some great stuff. Look under the automath tab to start.

SC-

 

Lots of great stuff, but without knowing my **** about turbo stuff then its going to be hard inputing required info. There was a book mentioned about FI, think it was by Yunick, not sure, but does it have the compressor maps in it maybe?

 

This will help to understand it a little better. At least it did for mew. Now I know what the lines mean. LOL

http://www.turbobygarrett.com/turbob..._techinfo.html

 

You have to sit down with a calculator and formulas. Most of the formulas can be found in Corky Bells Maximum boost. That, together with all you motor and turbo info, projected efficiencies of the intercooler and so on, and you can plot it on the map I can not leagally post the entire map, but email me if you would like to see mine...

 

Dude, no offense but if I gotta do maff, nope, someone else can the map for me. hell with that. no wonder the ricers are all over this ****.
For real, Corky Bells book, not Smokey Yunick (although he has some good read out too!). Thanks guys. Will start with the link from F8L... and try to get this Max Boost book before I leave for Afghanistan as I am sure its not a best seller over there.

Charlie

 

The gannis go fast with water injection, not turbos. Watch those camel fockers run!

Good Luck when you go and THANKS. We got your back....way back...
Seriously, bring the book...it'll tke your whole tour to undertand it. But bring a calc and do maff...or the ricers will take over.

 

Thanks Jammer! Gotta share your words of encouragement. Kool

 

Pick up corky bell's book. It's an excellent read.

So I guess I'm the "import" guy?? heh



You first need to figure out the air flow rate of your engine N/A

CID * RPM * 0.5 * VE / 1728

So for a stock displacement 346 this would equate to...

346 * 6500 * 0.5 * 0.85 / 1728 = 553 CFM (at 6500rpm)


Next you need to know your desired pressure ratio.
14.7psi (1 bar) is one atmosphere. You need to add the desired amount of boost to this base amout. We'll pick 13psi which is .89 bar. Your pressure ratio for 13psi will be 1.89

you then multiply your desired pressure ratio against your N/A CFM.

1.89 * 553 = 1045 CFM (boosted)

For many compressor maps you'll need to convert cfm to lbs/m.

The general consenses seems to be multiply by .069

1045 * .069 = 72 lbs/m

So now we'll look at a compressor map...



The pressure ratio is marked vertically on the scale and your air flow (lbs/m) is marked horizontally.

pin point where the two meet on the compressor map. You want to stay within 60% of the compressors effieciency and never hit the surge limit at any rpm.

To calculate where you will be on the compressor map at different boost and rpm levels, change the formula above as needed.

Make sense?

 

Now thats some expalining there. Wow, and other then the math, I actually understood the ****! Thanks.

Charlie.

 

Gosh durn, that 1.3L fella knows some math don't he Good info though...I have never really known how that is calculated until now

 

The majority of what I typed above is what I learned from corky's book. I started reading it earlier this week (time permitting). I had to poke around on the net to find how to properly convert from cfm to lbs/min and a few other things, but for the most part, it's in the book.

Today I'm reading chapter 6: intake manifold design. cool stuff. :thump:


$27 shipped from Amazon.com
http://www.amazon.com/exec/obidos/tg...books&n=507846

 

btw...

for a wide range of compressor maps check out.

http://www.turbocalculator.com/compressor-maps.html

If you guys don't want to do the math this website also sells software to help plot your engine and boost requirements against available compressor maps.

If you molest google.com enough, I imagine you could find a couple websites that will do the calculations for you.

 

Most maps if not all maps show a standardized lbs/min on the bottom axis. It may be necessary to convert your estimated lbs/min to the standard, by taking into account air intake temperature.

 

Wouldn't that make the T76 too small for that engine you calculated? I thought it was about 40 for small block v8 engines? At 1.89 and 72 it is almost off the map...?

Also, With my engine computed it comes out to 94 lbs/m....how would I get in the good efficiency range?


Thanks,
Andy

 

Get an T-80 or bigger... That's a lot of motor you got there...