http://www.turbofast.com.au/FlowT3.html

Here is a compressor flow map for some garrett t3's. What does it all mean? I used to know...but my mind is a mess lately - working a billion hours a week and all.

Thanks in advance.

 

I'm only helping because I was looking for some straight T3 maps
For the x-axis(horizontal):
Displacement in liters*1/2* 0.0353146667(according to Google)*rpm(high or low, or peak hp or whatever you want) = CFM of ingested air. This also depends on the efficiency of the engine, but assuming 100% is pretty safe (anyone say otherwise?)

Then multiply the CFM(in the case of a 1.6l @7000rpm; 197cfm) by 0.0756 to get lb/min(which is about 14.95, in this case and about 8.5@4000rpm)

For the y-axis, vertical, the pressure ratio is (boost+atmo)/atmo, so for 10psi; (10+14.7)/14.7=1.68.

If you cypher those numbers onto the first graph, they both fall into the max efficiency, barely. In theory you want to calculate the points for: lowest rpm where you start to build boost, peak HP, peak TQ and MAX rpm. If all of those fall into the maximum efficiency range (innermost area of graph) then you have the right turbo, in theory. I hate to admit it, but these graphs really showcase how a different trim can make a big difference...you can eek out a few % more efficieny AND lower rpm boost, it seems...

So yeah, I've had a couple beers. Hope that helps

 

Ok, I totally understand your math, etc. But my results don't seem to make sense logically. If you calculate cfm's for a 1.6 at 8000 rpms you get ~ 226. Which comes out to 17 lb/min for air flow. At 10 lbs like you said, you're looking at 1.68 for pressure ratio. So....plotting these points on graph one (t3 40 trim...you're out of all efficiency areas which are mapped. BUT, if you up the boost a couple of lbs.....then you are IN the efficiency range.

Sooooo...my question is..why would a turbo be more efficient at a higher boost level? Why can it flow enough air at 12 lbs of boost at 8000 rpms, but not at 10 lbs of boost?

 

It can flow the air but it will not be happy flowing 'just' that amount of air. It will want to flow more and your wastegate will be very active in preventing boost creep. In effect you'll be constantly bleeding off tons of pressure from the manifold to keep it at that boost level.

 

https://honda-tech.com/zerothread?id=142398 just for knowledge's sake

 

awesome, thanks man