L28ET Engine Air Flow and Turbo Compressor Maps
Calculations:
280z Displacement = 2.753 litres = 168.00 cubic
inches
Air flow equals: Cid X
RPM X 0.5 X Ev
1728
For 6500 redline and Ev = 0.80:
Air flow equals: 168 X
6500 X 0.5 X 0.80
= 252.78cfm
1728
1lb/min = 14.472 cfm
so 252.78cfm = 17.47 lbs/min
air flow at boost = stock air flow X pressure
ratio
Pressure Ratio = (boost + 14.7)
14.7
So for 20psi of Boost @ 6500rpm:
Air flow = 252.78 X (20+14.7) =
596.69cfm or 41.23lbs/min
14.7
Air Flow Data in Table Form for different
levels of boost: (both cfm and lbs/min)
|
Air
Flow (cfm) |
RPM |
Stock
(0psi) |
7psi |
10psi |
16psi |
20psi |
6500 |
252.78 |
373.14 |
424.73 |
527.90 |
596.69 |
6000 |
233.33 |
344.44 |
392.06 |
487.30 |
550.79 |
5000 |
196.87 |
290.62 |
330.80 |
411.16 |
464.73 |
4000 |
159.44 |
235.37 |
267.91 |
332.99 |
376.37 |
3250 |
131.13 |
193.57 |
220.33 |
273.85 |
309.53 |
3000 |
122.50 |
180.83 |
205.83 |
255.83 |
289.16 |
2000 |
81.67 |
120.55 |
137.22 |
170.55 |
192.78 |
1000 |
41.32 |
60.99 |
69.43 |
86.29 |
97.54 |
700 |
28.92 |
42.70 |
48.60 |
60.40 |
68.27 |
20%
of Redline Flow |
50.56 |
74.63 |
84.95 |
105.58 |
119.34 |
Calculated L28ET air flow in CFM using
Ev 0.85 to 0.80
|
Air
Flow (lbs/min) |
Pressure
Ratio |
1.48 |
1.68 |
2.09 |
2.36 |
RPM |
Stock
(0psi) |
7psi |
10psi |
16psi |
20psi |
6500 |
17.47 |
25.78 |
29.35 |
36.48 |
41.23 |
6000 |
16.12 |
23.80 |
27.09 |
33.67 |
38.06 |
5000 |
13.60 |
20.08 |
22.86 |
28.41 |
32.11 |
4000 |
11.02 |
16.26 |
18.51 |
23.01 |
26.01 |
3250 |
9.06 |
13.38 |
15.22 |
18.92 |
21.39 |
3000 |
8.46 |
12.50 |
14.22 |
17.68 |
19.98 |
2000 |
5.64 |
8.33 |
9.48 |
11.79 |
13.32 |
1000 |
2.86 |
4.21 |
4.80 |
5.96 |
6.74 |
700 |
2.00 |
2.95 |
3.36 |
4.17 |
4.72 |
20%
of Redline Flow |
3.49 |
5.16 |
5.87 |
7.30 |
8.25 |
Calculated L28ET air flow in
lbs/min using Ev 0.85 to 0.80
Air Flow Data Plotted Against Different Boost
Levels (Pressure Ratio vs. lbs/min)
L28ET air flow in
lbs/min at 10, 16 and 20psi (1.68 / 2.09 / 2.36BAR) of boost
- far right end points are at max boost and
redline (6500rpm)
- "knees" are half way to redline
when full boost hits (3250rpm) note: this is an arbitrary point and is
dependent on A/R ratio.
- far left "start" point is 20% of
redline flow and pressure ratio of 1BAR note: this is also arbitrary
Air Flow Data Plotted Against Different Boost
Levels and Transcribed to "Stock"
Garrett T3-60 Compressor Map (Pressure Ratio vs. lbs/min)
- 6500 rpm red line points for this compressor
at all three levels of boost are at the 60% or lower efficiency range. This
means the compressor is making a lot of heat in these regions. The boost
range from 10 to 16psi holds near 60% at redline but it quickly gets
worse as the boost is increased toward 20psi.
- Since the "knee" is ~3250 rpm, and
it is in the 74% efficiency "sweet spot" this compressor will work
well between 3250rpm and 4500rpm
- This compressor is optimized for low boost
small displacement engines
- Goldilocks says "too small, too hot"
Air Flow Data Plotted Against Different Boost
Levels and Transcribed to Garrett T61 Compressor Map (Pressure Ratio vs.
lbs/min)
- 6500 rpm red line points for this compressor,
for all three levels of boost, are in the 76% "sweet spot"
- 3250 rpm
"knee" points for this compressor, for all three levels of boost, are
in the 66% area near the surge limit. This region is where the flow is not
sufficient to spin the turbo wheels.
- This big compressor will give poor performance
unless running full out near red line. Therefore; it is great for drag applications
and not so great for the street.
- Goldilocks says "too big"
Air Flow Data Plotted Against Different Boost
Levels and Transcribed to Garrett T04E-50 Compressor Map (Pressure Ratio
vs. lbs/min)
- 6500 rpm red line points for this compressor
at all three level of boost are in the 75% +/- 1% efficiency region.
- 3250 rpm
"knee" points for this compressor at all three level of boost are
in the 74% +/- 1% efficiency region.
- When accelerating towards redline, the
efficiency passes through the maximum 78% area, thus performance is ideal
during this period.
- It should be obvious that this compressor can
handle even more boost and remain very efficient above the 20psi line. "It can grow with
your need for more speed"
- This compressor will give great performance
compared to the stock T3-60.
- Goldilocks says "just right"
Air Flow Data Plotted Against Different Boost
Levels and Transcribed to Garrett GT35R Compressor Map (Pressure Ratio
vs. lbs/min)
- 6500 rpm red line points for this compressor
at all three level of boost are in the 72% to 79% efficiency region.
- 3250 rpm
"knee" points for this compressor at all three level of boost are
below the 65% efficiency region.
- When accelerating towards redline, the
efficiency increases towards the maximum 79% area, thus performance is best
full out.
- This compressor would certainly work better
with more engine displacement as the horizontal lines would be more to the
right
- It should be obvious that this compressor can
handle even more boost and remain very efficient above the 20psi line. "It can grow with
your need for more speed"
- Goldilocks says good for a turbo stroker.
Air Flow Data Plotted Against Different Boost
Levels and Transcribed to Garrett T04B-60-1 Compressor Map (Pressure Ratio
vs. lbs/min)
- 6500 rpm red line points for this compressor
all fail to reach the highest efficiency region.
- 3250 rpm
"knee" points for this compressor at all three levels of boost are
in the surge threshold region
- It should be obvious that this compressor will
work better with a larger displacement engine as it's sweet spot is far to
the right where higher flows are required.
- Goldilocks says "too demanding"
- 6500 rpm red line points for this compressor
at all three level of boost are in the 60-75% efficiency region.
- 3250 rpm "knee" points for this
compressor at all three level of boost are in the 76% +/- 1% efficiency
region.
- When accelerating towards redline, the
efficiency drops out of the maximum 76% area, thus performance decreases as
rpms increase though this is not as bad as the T3-60 above
- It should be obvious that this compressor will
work best for lower flowing engines with boost between 8 and 12psi.
- This compressor will give slightly better
performance performance to the stock T3-60.
- Goldilocks says "not a significant change
from stock"
- 6500 rpm red line points for this compressor
at all three level of boost are in the 45-60% efficiency region.
- 3250 rpm "knee" points for this
compressor at all three level of boost are in the 69 to 72% efficiency
region.
- When accelerating towards redline, the
efficiency drops out of the maximum 73% area, thus performance decreases as
rpms increase though this is not as bad as the T3-60 above
- It should be obvious that this compressor will
work best for lower flowing engines with boost between 8 and 12psi.
- This compressor will give slightly better
performance performance to the stock T3-60.
- Goldilocks says "not a significant change
from stock"
- 6500 rpm red line points for this compressor
at all three level of boost are in the 70 to 76% efficiency region.
- two of the 3250 rpm
"knee" points for this compressor are below the surge limit so a
dual stage boost controller is needed to only let the high boost at higher
rpms's
- When accelerating towards redline, the
efficiency passes through the maximum 78% area at 10psi and 76% at 16 and
20psi, thus performance is ideal
during this period.
- It should be obvious that this compressor can
handle only slightly more boost above the 20psi line.
- This compressor will give great performance
compared to the stock T3-60.
- Goldilocks says "ok but not most
efficient and needs dual stage boost controller"
- 6500 rpm red line points for this compressor
at all three level of boost are in the 65 to 72% efficiency region.
- 3250 rpm
"knee" points for this compressor at all three level of boost are
in the 73% efficiency region.
- When accelerating towards redline, the
efficiency passes through the maximum 76% area, thus performance is ideal
during this period.
- It should be obvious that this compressor can
handle only slightly more boost above the 20psi line.
- This compressor will give great performance
compared to the stock T3-60.
- Goldilocks says "ok but not most
efficient"
- 6500 rpm red line points for this compressor
at all three level of boost are in the 65 to 68% efficiency region.
- 3250 rpm
"knee" points for this compressor at all three level of boost are
in the 77% efficiency region.
- When accelerating towards redline, the
efficiency passes through the maximum 76% area for 16 and 20psi, thus performance is ideal
during this period.
- It should be obvious that this compressor can
handle slightly more boost above the 20psi line and 10psi boost is just OK.
- This compressor will give great performance
compared to the stock T3-60.
- Goldilocks says "ok but not most
efficient"