VG30ET Engine Air Flow and Turbo Compressor Maps

Originally sourced from L28ET Engine Air Flow

Calculations:

Z31 - VG30ET Displacement = 3.0 liters = 183.07 cubic inches

Air flow equals: Cid X RPM X 0.5 X Ev
1728

For 6500 redline and Ev = 0.80:

Air flow equals: 183.07 X 6500 X 0.5 X 0.80 = 275.35cfm
1728

1lb/min = 14.472 cfm

so 275.35 cfm = 19.03 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 = 275.35 X (20+14.7) = 650.22cfm or 44.93lbs/min
14.7

Air Flow Data in Table Form for different levels of boost: (both cfm and lbs/min)

RPM	CFM 0PSI	7PSI	10PSI	12PSI	14.7PSI	20PSI	25PSI	29.4PSI
6500	275.45	406.32	462.84	500.3	550.91	650.22	743.91	826.36
6000	254.26	375.06	427.24	461.82	508.53	600.2	686.69	762.79
5000	211.89	312.55	356.03	384.85	423.77	500.17	572.24	635.66
4000	169.51	250.04	284.83	307.88	339.02	400.13	457.79	508.53
3250	137.73	203.16	231.42	250.15	275.45	325.11	371.95	413.18
3000	127.13	187.53	213.62	230.91	254.26	300.1	343.34	381.4
2000	84.75	125.02	142.41	153.94	169.51	200.07	228.9	254.26
1000	42.38	62.51	71.21	76.97	84.75	100.03	114.45	127.13
700	29.66	43.76	49.84	53.88	59.33	70.02	80.11	88.99
1240	52.55	77.51	88.3	95.44	105.1	124.04	141.91	157.64

Calculated VG30ET air flow in CFM using Ev 0.80

	Air Flow lb/min
Pressure Ratio	1	1.48	1.68	1.82	2	2.36	2.7	3
RPM	0PSI	7PSI	10PSI	12PSI	14.7PSI	20PSI	25PSI	29.4PSI
6500	19.03	28.08	31.98	34.57	38.07	44.93	51.4	57.1
6000	17.57	25.92	29.52	31.91	35.14	41.47	47.45	52.71
5000	14.64	21.6	24.6	26.59	29.28	34.56	39.54	43.92
4000	11.71	17.28	19.68	21.27	23.43	27.65	31.63	35.14
3250	9.52	14.04	15.99	17.29	19.03	22.46	25.7	28.55
3000	8.78	12.96	14.76	15.96	17.57	20.74	23.72	26.35
2000	5.86	8.64	9.84	10.64	11.71	13.82	15.82	17.57
1000	2.93	4.32	4.92	5.32	5.86	6.91	7.91	8.78
700	2.05	3.02	3.44	3.72	4.1	4.84	5.54	6.15
1240	3.63	5.36	6.1	6.59	7.26	8.57	9.81	10.89

Calculated L28ET air flow in lbs/min using Ev 0.85 to 0.80

Download vg30et Airflow excel spreadsheet to modify calculations: vg30ETAirflow.zip
This spreadsheet has the following plot Air Flow vs. Boost Levels:

Air Flow Data Plotted Against Different Boost Levels (Pressure Ratio vs. lbs/min)

VG30ET air flow in lbs/min at 10, 12, 14.7, 20, 25 and 29.4psi (1.68 / 1.82 / 2.0 / 2.36 / 2.7 / 3.0 BAR) 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" for street, OK for Drag..

Air Flow Data Plotted Against Different Boost Levels and Transcribed to Garrett T04E-50 Compressor Map (Pressure Ratio vs. lbs/min)

L28 compared to VG30et:

For L28:

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"

Fo VG30et:

Over 14.7PSI (1 Bar) Knee gets closer to the Surge Limit.
Over 25PSI, no longer in the sweet spot and not efficient at redline.

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"

GT30R Example:

6500 rpm red line points for this compressor at 10-20PSI levels 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 lower efficiency region.
When accelerating towards redline, the efficiency passes through the maximum 76% area for 10-20psi, thus performance is ideal during this period.
It should be obvious that this compressor can handle slightly more boost above the 25psi line.
Wish the knees were a little more to the right, nearing surge point at 20psi and above. But at higher rpm the compressor will most efficient.
Goldilocks says "pretty sweet below 20PSI."

Just to compare, here it is again with an engine with a .90 Ve, This would be an upgraded engine at or near sea level.

Notice that at higher boost levels it is never near surge limit.
Notice that Lb/min at 25 PSI is equal to the .80Ve at 30 PSI.
Notice that this turbo is now out of the box at 30 PSI. (You would never get there.)

Goldilocks says Too small use the 76.2mm!
No lag rally type application good to 20psi.
Notice that at low boost it is never in the sweet spot (not until 20PSI).

GT35R 82mm Example: Looky looky

Great to about 18psi. always going to 79% eff. range
Needs multi-stage boost control over 18psi , 72% eff. to 25psi (55lb/min = ~550Hp range)

Here it is again with a modified engine near sea level, 7K rpm redline with a 90 Ve 4k and Knee :

Notice that it is good to 25PSI,
Notice that it ranges thru the sweet spot to about 23PSI

GT40R 56trim:

Too close to surge limit everywhere. Maybe a different trim would work.?
Dang too big, Without engine modifications to increase ev and added rpm range to get to sweet spot..
Knee needs to move to higher rpms. 4000 rpm knee to get past surge limit.

GT40R_56trim Ve 90% 4K Knee 7000 RPM range: