Turbo Flow rates and IC piping

I did some research and found some useful info on turbo flow rates and when the IC pipes start to restrict and when the pipes are an overkill that creates turbo lag.

Quote:

---

*.4 Mach is the point at which air becomes turbulent and losses in efficiency start to occur exponentially. The key is to stay under that speed. You want to use the smallest piping possible that still flows enough to meet your needs. Larger than necessary piping increases lag time with no measurable gain

The velocities are in miles per hour and mach, and the flow rates are in cfm. Measurements for the piping are in inches.

---

2" piping

300 cfm = 156 mph = 0.20 mach
400 cfm = 208 mph = 0.27 mach
500 cfm = 261 mph = 0.34 mach
585 cfm max = 304 mph = 0.40 mach


2.25" piping

300 cfm = 123 mph = 0.16 mach
400 cfm = 164 mph = 0.21 mach
500 cfm = 205 mph = 0.26 mach
600 cfm = 247 mph = 0.32 mach
700 cfm = 288 mph = 0.37 mach
740 cfm max = 304 mph = 0.40 mach


2.5" piping

300 cfm = 100 mph = 0.13 mach
400 cfm = 133 mph = 0.17 mach
500 cfm = 166 mph = 0.21 mach
600 cfm = 200 mph = 0.26 mach
700 cfm = 233 mph = 0.30 mach
800 cfm = 266 mph = 0.34 mach
900 cfm = 300 mph = 0.39 mach
913 cfm max = 304 mph = 0.40 mach


2.75" piping

300 cfm = 82 mph = 0.10 mach
400 cfm = 110 mph = 0.14 mach
500 cfm = 137 mph = 0.17 mach
600 cfm = 165 mph = 0.21 mach
700 cfm = 192 mph = 0.25 mach
800 cfm = 220 mph = 0.28 mach
900 cfm = 248 mph = 0.32 mach
1000 cfm = 275 mph = 0.36 mach
1100 cfm max = 303 mph = 0.40 mach


3.0" piping

300 cfm = 69 mph = 0.09 mach
400 cfm = 92 mph = 0.12 mach
500 cfm = 115 mph = 0.15 mach
600 cfm = 138 mph = 0.18 mach
700 cfm = 162 mph = 0.21 mach
800 cfm = 185 mph = 0.24 mach
900 cfm = 208 mph = 0.27 mach
1000 cfm = 231 mph = 0.30 mach
1100 cfm = 254 cfm = 0.33 mach
1200 cfm = 277 mph = 0.36 mach
1300 cfm max= 301 mph = 0.39 mach


And the flow rates of most Mitsu turbos

Flow Rates @ 15psi:
TDO4-9B-6CM2 265 CFM
TDO5-12A-8CM2 320 CFM
TDO4-13G-5CM2 360 CFM
TEO4-13C-6CM2 360 CFM
TDO4L-13G-6CM2 360 CFM
TDO4L-15C-8.5CM2 390 CFM
TDO5H-14B-6CM2 405 CFM
TDO5H-14G-8CM2 465 CFM
TDO5H-16G-7CM2 505 CFM
TDO5H-16G-10CM2 505 CFM
TDO6-17C-8CM2 550 CFM
TDO6H-20G-14CM2 650 CFM
TDO7S-25G-17CM2 850 CFM
TFO8L-30V-18CM2 1200 CFM


If you have the pounds per min rate or lb/min of a turbo the conversion is done easily:

lb/min x 14.27 = CFM

Example: Big16g has max flow rate of ~39-40 lb/min

40lb/min x 14.27 = 570 CMF

Which means that even 2'' pipes do not restrict the MAXIMUM flow made by Evo3-8 B16g.

Now imagine the lag you get from 2.25 or 2.5'' pipes on 14b!

These conclusions are based on low level boost 8-15 psi on stock internals motor.

Credits go to gstryyder on DSM Tuners and boomtown on EvoM.net

Some more info on air losses

2.25" O.D. straight tubing: 0.17 psi per foot
2.5" O.D. straight tubing: 0.10 psi per foot
3" O.D. straight tubing: .04 psi per foot


2.25" O.D. 90* bend: 0.27 psi per bend
2.5" O.D. 90* bend: 0.17 psi per bend
3" O.D. 90* bend: .08 psi per bend


So having the shortest route from the turbo to the throttle body will equal more psi at the intake manifold

Quote:

---

Originally Posted by mko

Some more info on air losses

2.25" O.D. straight tubing: 0.17 psi per foot
2.5" O.D. straight tubing: 0.10 psi per foot
3" O.D. straight tubing: .04 psi per foot


2.25" O.D. 90* bend: 0.27 psi per bend
2.5" O.D. 90* bend: 0.17 psi per bend
3" O.D. 90* bend: .08 psi per bend


So having the shortest route from the turbo to the throttle body will equal more psi at the intake manifold

---

the way i understand these numbers is that the bigger the diameter is the less air you lose, am i seeing things or is there a mistype in here ??

That info is a good guide, real world results though wouldnt fit that guide as written though. Larger diameter pipes cause a "pressure drop" due to the turbo having to work harder to fill the larger pipes thus creating more lag. The info about losing air pressure around bends based on diameter doesnt make sense though, that info is based on an engine thats 100% efficient. If the engine used all the air at the same rate the turbo is pushing it out then you would never be able to create boost pressure. The same given amount of air will have more pressure if forced into a smaller diameter pipe versus a larger diameter pipe when keeping all other variables constant. God I hate math......

Quote:

---

Originally Posted by Stewi

That info is a good guide, real world results though wouldnt fit that guide as written though. Larger diameter pipes cause a "pressure drop" due to the turbo having to work harder to fill the larger pipes thus creating more lag. The info about losing air pressure around bends based on diameter doesnt make sense though, that info is based on an engine thats 100% efficient. If the engine used all the air at the same rate the turbo is pushing it out then you would never be able to create boost pressure. The same given amount of air will have more pressure if forced into a smaller diameter pipe versus a larger diameter pipe when keeping all other variables constant. God I hate math......

---

ok so here is my question.

my intercooler is 2.5". i got a big 16G i'm going to be using. i got a FP j pipe that goes from stock size to 2"

million dollar question is what size charge pipes to run??????

2.25, or 2.5 would be my guess from reading the chart

Nope, the chart would say a 2" charge pipe would still allow more flow than the turbo could produce, so 2" is fine, you can go to 2.5" if you would like, but you dont need to and running the larger pipe can cause a bit more lag, but lag is non-existant on a 2.4 engine and a 16g anyway, so your fine either way. If you run 2" pipe from the turbo to the intercooler, you should run a 2.5" pipe from the intercooler to the throttle body. Since the intercooler is 2.5" in/out, you would be causing a bottle neck by reducing the outlet from 2.5 to 2.0, it would still work fine, but rule of thumb is to not create a bottle neck.

Hey thats why I went from full 2.5'' after the j-pipe to the TB to 2'' from j-pipe to IC then a "bottle neck" from 2.5'' to 2'' so it can go thru the radiator subframe and then to 2.5'' for the UICP all the way to the TB (since my TB is 60mm = 2.5'')

Big difference in how the turbo spools, car kicks much harder now, BOV is 100% louder

Quote:

---

Originally Posted by mko

2.5" piping
400 cfm = 133 mph = 0.17 mach


TDO5H-14B-6CM2 405 CFM

Now imagine the lag you get from 2.25 or 2.5'' pipes on 14b!

---

I'm a lil confused (maybe i'm reading it the wrong way).
For a 14B at 15psi, you're seeing about 405 CFM.
With a 2.5" setup that's only 0.17 Mach.
Maybe with that low of boosted pressure lag would be more probable? :017:
I was planning on doing 2.5" piping all around with the 14B; maybe i should do 2" instead and open up to 2.5 at my TB? :017:

2.5 is way too big for 14b, its even big for a maxed out 16g

i'm going to do the 2 inch to the intercooler and 2.5 after. thanks for the info

drew are you leaving the stock 6cm hot side on the 14b? i recommend getting the 7cm housing for it from a 16g, find a blown 16g big or small, but it, swap the compessor wheels and covers and hot side and youll be all set.

you cant just swap the compressor housing and wheel. There is this bed in the center housing where the wheel sits in and that is different for every MHI turbo. As the turbo size goes up the wheel size and that bed size go larger as well.

i thought somebody else did the same mod as well... :?

Quote:

---

Originally Posted by run1206

i thought somebody else did the same mod as well... :?

---

i have a 14b chra with a 16g wheel and compressor cover sitting in my basement that i rebuilt and it spins just fine, only difference is the 14b is flat back wheel and the 16g is a superback wheel

So any of these 2.5" intercooler and piping kits off ebay will handle the 25G turbo just fine?

yes it will.