 |
|
|
[Subscribe to Daily Digest] |
[Profile/Gallery]
, Sat, 5 Feb 2005 15:58:30
Members do not see ads below this line. - Help Keep This Site Online - Signup
On the map, which looks like a topographical map, each curve (kidney bean shape in this case) represents an efficiency range. You'll see that in this case they are labelled .77, .72 and so on. .77 is the highest efficiency that this turbo is capable of. This means that for the work you put in (exhaust heat and flow) that 77% of it becomes pressure and air flow while 23% of it becomes heat in your intake charge. Obviously the higher efficiency the better, but 77% is pretty damn good for a centrifugal compressor.
The scale on the left (y-axis) is the pressure ratio between the boost charge and the atmosphere. So if you are near sea level and the barometric pressure in the atmosphere is near 1 bar, you would achieve a 2.0 pressure ratio by using 1 bar boost pressure. Running 2 bar boost (wheeeeeee!!!) would mean a pressure ratio of ~3.0.
The bottom scale (x-axis) is the airflow, which corresponds to a particular horsepower level. I can't remember the conversion factor off the top of my head, and it differs depending on your vehicle setup, but X(hp)=Q(lbs/min) worth of air.
SOOOOOO....
To make use of this thing, you determine where your target hp corresponds to the lbs/min scale, then trace straight up to the highest efficiency "island" you can find on your vertical trace. Then trace left to see the boost pressure ratio the compressor will use to make this power level at this efficiency range. Obviously some hp levels will not be efficient on this map, indicative that this is not a good turbo for said hp level.
Another use is to determine you pressure ratio (for on a pre-existing setup) and your hp level (dyno, then convert to flywheel hp then to lbs/min) to determine the efficiency of your turbo. Close to the outermost contours is bad. Your turbo could be short lived (efficiency towards the left side) or you could be coping with unnecessary lag (close to the right side).
So that is what I have come to understand of compressor maps. If I have slaughtered something please correct me.
Andy
Mechanical Engineering Undergraduate
Boulder CO
1991 Red SPG Airflow (much closer to stock that it was 2 days ago!)
posted by 67.173.2...
, Fri, 4 Feb 2005 18:31:21, Sat, 5 Feb 2005 04:53:15, Sat, 5 Feb 2005 19:29:24, Sat, 5 Feb 2005 15:58:30, Sun, 6 Feb 2005 20:16:23, Fri, 4 Feb 2005 18:57:51, Sat, 5 Feb 2005 21:49:36, Mon, 7 Feb 2005 06:40:16
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
