I've been trying to figure out compressor maps and I think I figured out what turbo I need. If you have "Maximum Boost" you should know the cfm formulas. Here is what numbers I used: 94ci, and 7800 rpm and 85% for Ev. Came out to 252cfm at 7psi, 328cfm at 12psi and 425cfm at 20psi. Based on this I looked a the turbonetics maps and am thinking about the 50 trim. If I am reading the map right, about 74% efficiency at 12psi and 70% at 20. The map looked like the 50 trim flows good between 12 and 18 psi for my application. Does this look right to you guys?

 

I'm curious, are you converting the CFM to Pounds per Minute (LB/MIN) and also the PSI to Pressure Ratio (PR) when you are looking at the compressor maps?

A while back someone gave me the conversion ratio to change CFM to LB/MIN and by doing a little extrapolation, I determined that @ 112 degrees (air temperature)the conversion factor is 0.070318

<U>252 CFM</u>
252 * 0.070318 = 17.75 LB/MIN

<u>328 CFM</U>
328 * 0.070318 = 23.06 LB/MIN

<U>425 CFM</u>
425 * 0.070318 = 29.89 LB/MIN

and to change PSI to PR it's in the book:
PR = (PSI + 14.7) / 14.7

<U>7 PSI</u>
(7 + 14.7) / 14.7 = 1.48 PR

<U>12 PSI</u>
(12 + 14.7) / 14.7 = 1.82 PR

<U>20 PSI</u>
(20 + 14.7) / 14.7 = 2.36 PR


[Modified by BlueShadow, 10:26 AM 4/27/2002]

 

also check out these threads
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https://honda-tech.com/zerothread?id=142398
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Thanks. Good info.

 

Wow! where is that picture taken from??

 

it was just a regular T04E 60 trim compressor map from http://www.turbocharged.com BUT I added all the text and curves with a paint/jpeg/image editor. I just hope my free image hoster doesn't run out of bandwidth.

I would only use this method of selecting compressors for low-mid boost 15 PSI and less. Above 18 PSI thiings start to get complicated and it gets a little more in-depth.


[Modified by BlueShadow, 3:22 PM 4/27/2002]

 

Nice, I have the 60 trim myself. I saved the image so i'll host it if it goes down.

I'm interested in higher boost levels, for 6-8lbs@8.8:1 it's not too efficient, but will be in the higher boost ranges. I took this turbo up to 13-14lbs once on my stock block, and it felt amazing.