Hello,

I have been researching how to read compressor maps and think I have figured it out and a turbo(s) for my setup. Just wanted to run this by everyone and see if my logic makes sense.

Goals and engine:
1) 700 flywheel horsepower
2) twin turbos
3) 5.8L (351w) built engine with aluminum heads
4) Max RPM 6000
5) VE 90
6) Turbo: GTX3576R, 76mm, 58 Trim, 0.6 A/R
7) 12 PSI boost

I ended up with a Pressure Ratio of 1.82 and a CFM of 1005.08. From what I understand, I would divide the CFM by 2 (twin turbo) and I get 502.54 as the CFM and 35.22 lb/min PER turbo.

Ok so in the image attached, the RED line is the Pressure Ratio line, the YELLOW line is the Max RPM at ~35lb/min, the ORANGE line is when I can expect max boost RPM which is 2400 RPM, and the GREEN line is 20% of turbo max RPM CFM for an idea of how close I would be to the surge.

Questions:
1) Did I apply everything correctly to the compressor map?
2) Is the math/logic right to run 35.22 lb/min PER turbo to support 700 horsepower?

I know some of you would use a different turbo, I just want to know if I did the compressor map process correctly.

Thanks!

Slows

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Looks good to me, and yes 35 lb/min is in the ballpark for 700 fwhp. I wouldn't want to be that close to the surge line though, if they spool just a bit earlier than expected, they could easily surge, and there is nothing wrong with being a little to the right at peak hp for the average setup.

 

So im not sure how to get further to the right of the surge line.. I just drew a line down from where the red line intercepts the surge line which I thought was the minimum RPM for when max boost is reached.

 

I'd look for something with a little less compressor flow (smaller compressor). You could be a couple efficiency islands to the right at peak without worry, and that will move your boost threshold line away from the surge line as well.

 

Ok. So what's the best way to do this? Just look at other maps from other turbos? I'm not sure how to size compressors accurately..

 

http://www.turbos.bwauto.com/afterm...wts=400&pt6_wd=83&pt6_wd2=74&pt6_wrsin=92044&

play with some numbers here select different compressors