There are a few easy to use calculators out there that calculate the information for matching engine air flow with turbo compressor map. However, I wanted to create one that housed the specific information for the g10 and g13B engines. I also want to post up the various different compressor maps for quick reference. I will edit as I go.
Airflow rate = cid(cubic inch displacement) x rpm x 0.5(four stroke cycle engine fill its cylinders only on one-half the revolutions) x Ev(volumetric efficiency) divided by 1728 (12x12x12x12, converts cubic inches to cubic feet).
Then multiple this by your pressure ratio. You can adjust these numbers using the above formula for your desired pressure ratio.
For turbo compressor match up you want to look through the entire rpm range to see where the efficiency lies at your desired pressure ratio. You don't need more than five data points to get a reasonable approximation where your compressor lies.
Volumetric Efficiency
The volumetric efficiency is only a guess, it could be as low as 0.65 or even as high as 0.95. It is difficult to calculate volumetric effieciency of a car without the right equipment, but from what I have read the literature suggest that you take a modern production car's volumetric effieciency somewhere between 75% and 85%. 95% would be excellent. Although in some applications 100% can be exceeded; turbo charging and other ways including designs on naturally aspirated engines. The literature out there also suggest that the DOHC engines have a higher volumetric efficiency than SOHC. This means that the G13B could be considerably higher in VE; as high as 110% to start with.
For the G10 .993 liter compressor mapping
993 cc to cid = 60.6 cubic inches
airflow rate= (cid x rpm x 0.5 x VE)/1728
1728 converts cbic inches to cubic feet
1. First example taking an educated guess for VE
60.6 x 5700 rpm x 0.5 x .80 VE)/1728 = 79.96 cfm. (most of us don't rev a g10 above 5000).
2. Another example where I was comparing the G10 and G13B with known HP for VE: (60.6 x 5700 rpm x 0.5 x .75 VE)/1728 = 74.96 cfm.
3. Another example where I compared the G10 and G13B with known HP at given rpm and using cfm calculator for given HP: (60.6 x 5700 rpm x 0.5 x .825 VE) / 1728 =82.5 cfm
For G13B DOHC 1.3 liter Compressor mapping
1.3 liters = 1298 cc = 79.33 cid
1. First example taking an educated guess for VE79.33 x 6500rpm x 0.5 x 0.90 VE)/ 1728 =134.28 cfm
2. Another example where I was comparing the G10 and G13B known HP for VE: (79.33 x 6500 rpm x 0.5 x 0.91 VE)/ 1728 = 135.77
3. Another example where I was comparing the G10 and G13B known HP, and rpm, and using cfm calculator for given HP: (79.33 x 6500 rpm x 0.5 x 1.005 VE)/ 1728 = 150 cfm
(6500 is close enough to redline, and is where HP is maxed out stock)
If you compare the known horsepower output of a 1 liter Geo Metro 55 Horsepower @5700 rpm to the 1.3 DOHC Suzuki swift GT(i) 100 Horsepower @6500 rpm you see that these numbers are reasonable. Horsepower and airflow calculator will put cfm at 150 to get 100 horsepower, and 82.5 cfm to get 55 horsepower. The VE numbers that I came up with using the equation that included HP, and CFM at a given rpm are the best numbers that I can use for the compressor mapping. They have the most statistical input; they can certainly be off, but they are good numbers. I am actually blown away with where they are at. For simplification I am going to round to 82% for the g10 and 100% for the g13b.
Pressure ratio = 14.7 + boost/14.7
5psi = 1.34
6psi= 1.41
7psi = 1.48
8psi = 1.54
9psi = 1.61
10psi = 1.68
11psi = 1.75
12psi = 1.82
13psi = 1.88
14psi = 1.95
14.7psi = 2
Example:
G13B: 150 x 1.68 = 252 cfm at 10 psi or roughly 7.134 cubic meters/min.
G10: 82.5 x 1.68 = 138.6 cfm at 10 psi.
Side note on turbo cold side pipe size selection:
For turbo pipe sizing you want to take our highest rpm or highest number of cfm's than use a turbulence formula based on pressure resistance inside a tube. I have calculated cfm's up to 400 and never saw a reason to go above 2" piping unless you can't find a way to put the pipping in without using a lot of 90 degree bends. The larger pipping will reduce the pressure resistance across these bends. Anything using smaller than a 2" piping the turbo lag created by the additional volume of piping is something less than 1/10 of a second. I would recommend 2" to make pipe purchasing with fitting and bypass or blow off valves a lot easier.
Remember these are approximations that are used to match up a turbo to your engine's cfm. Your final cfm output is ultimately also determined by a lot of other variables not to say the least the turbocharger you select and the air cooling system you have or don't have.
Airflow rate = cid(cubic inch displacement) x rpm x 0.5(four stroke cycle engine fill its cylinders only on one-half the revolutions) x Ev(volumetric efficiency) divided by 1728 (12x12x12x12, converts cubic inches to cubic feet).
Then multiple this by your pressure ratio. You can adjust these numbers using the above formula for your desired pressure ratio.
For turbo compressor match up you want to look through the entire rpm range to see where the efficiency lies at your desired pressure ratio. You don't need more than five data points to get a reasonable approximation where your compressor lies.
Volumetric Efficiency
The volumetric efficiency is only a guess, it could be as low as 0.65 or even as high as 0.95. It is difficult to calculate volumetric effieciency of a car without the right equipment, but from what I have read the literature suggest that you take a modern production car's volumetric effieciency somewhere between 75% and 85%. 95% would be excellent. Although in some applications 100% can be exceeded; turbo charging and other ways including designs on naturally aspirated engines. The literature out there also suggest that the DOHC engines have a higher volumetric efficiency than SOHC. This means that the G13B could be considerably higher in VE; as high as 110% to start with.
For the G10 .993 liter compressor mapping
993 cc to cid = 60.6 cubic inches
airflow rate= (cid x rpm x 0.5 x VE)/1728
1728 converts cbic inches to cubic feet
1. First example taking an educated guess for VE
60.6 x 5700 rpm x 0.5 x .80 VE)/1728 = 79.96 cfm. (most of us don't rev a g10 above 5000).2. Another example where I was comparing the G10 and G13B with known HP for VE: (60.6 x 5700 rpm x 0.5 x .75 VE)/1728 = 74.96 cfm.
3. Another example where I compared the G10 and G13B with known HP at given rpm and using cfm calculator for given HP: (60.6 x 5700 rpm x 0.5 x .825 VE) / 1728 =82.5 cfm
For G13B DOHC 1.3 liter Compressor mapping
1.3 liters = 1298 cc = 79.33 cid
1. First example taking an educated guess for VE
79.33 x 6500rpm x 0.5 x 0.90 VE)/ 1728 =134.28 cfm2. Another example where I was comparing the G10 and G13B known HP for VE: (79.33 x 6500 rpm x 0.5 x 0.91 VE)/ 1728 = 135.77
3. Another example where I was comparing the G10 and G13B known HP, and rpm, and using cfm calculator for given HP: (79.33 x 6500 rpm x 0.5 x 1.005 VE)/ 1728 = 150 cfm
(6500 is close enough to redline, and is where HP is maxed out stock)
If you compare the known horsepower output of a 1 liter Geo Metro 55 Horsepower @5700 rpm to the 1.3 DOHC Suzuki swift GT(i) 100 Horsepower @6500 rpm you see that these numbers are reasonable. Horsepower and airflow calculator will put cfm at 150 to get 100 horsepower, and 82.5 cfm to get 55 horsepower. The VE numbers that I came up with using the equation that included HP, and CFM at a given rpm are the best numbers that I can use for the compressor mapping. They have the most statistical input; they can certainly be off, but they are good numbers. I am actually blown away with where they are at. For simplification I am going to round to 82% for the g10 and 100% for the g13b.
Pressure ratio = 14.7 + boost/14.7
5psi = 1.34
6psi= 1.41
7psi = 1.48
8psi = 1.54
9psi = 1.61
10psi = 1.68
11psi = 1.75
12psi = 1.82
13psi = 1.88
14psi = 1.95
14.7psi = 2
Example:
G13B: 150 x 1.68 = 252 cfm at 10 psi or roughly 7.134 cubic meters/min.
G10: 82.5 x 1.68 = 138.6 cfm at 10 psi.
Side note on turbo cold side pipe size selection:
For turbo pipe sizing you want to take our highest rpm or highest number of cfm's than use a turbulence formula based on pressure resistance inside a tube. I have calculated cfm's up to 400 and never saw a reason to go above 2" piping unless you can't find a way to put the pipping in without using a lot of 90 degree bends. The larger pipping will reduce the pressure resistance across these bends. Anything using smaller than a 2" piping the turbo lag created by the additional volume of piping is something less than 1/10 of a second. I would recommend 2" to make pipe purchasing with fitting and bypass or blow off valves a lot easier.
Remember these are approximations that are used to match up a turbo to your engine's cfm. Your final cfm output is ultimately also determined by a lot of other variables not to say the least the turbocharger you select and the air cooling system you have or don't have.
