2.5 intercooler pipe
Just worry about this part. Ignoring losses from bends and lengths etc. this part remains true
Just note the gain in velocity is not significant as long as inlet temps dont vary greatly. Like 1 bar boost you see 90 deg after cooler and 2 bar you see 200 deg or something like that. Say 10-20 deg spread is more typical. Velocity increases just alittle bit more because overall cfm is only increasing alittle bit more.
I guess there really is no general formula. Just need to compute the air properties at given temp and pressure. That specific volume is used to calculate cfm rate based on your air mass flow. Air mass flow is basically hp divided by 10. Thats rough estimate for mass flow in lbs per minute
Best i can simplify it is following assumptions.
10 psig of air at post cooler temp of 90 deg f which is a typical expected value most setups can see in a short run. Specific volume is 8.24. Use this for your cfm calc
15 psig of air at post cooler temp of 110 deg f, estimated typical post cooler temp, specific volume will be 7.103.
20 psig at 140 deg f lets say typical post cooler temp, specific volume is 6.40.
Use your estimated mass flow from turbo at that boost or your known/estimated hp level divided by 10 to get ur cfms.
2.5" pipe has area of 0.03409 ft square
3" pipe has area of 0.04909 ft sq
4" area of 0.08727 ft sq
Take cfm divide by 60 to get cfs and divide by pipe area to get velocity.
600 hp 5.3 on 10 psi would have 494 cfm. 167 feet per sec velocity in 3" pipe. Imo i see no reason to run more than 150-200 fps so 3" is perfect.
800 hp 5.3 on 20 psi would have cfm of 512 cfm. Velocity is now 174 fps in 3" pipe
See its not a significant gain in speed.
Just note the gain in velocity is not significant as long as inlet temps dont vary greatly. Like 1 bar boost you see 90 deg after cooler and 2 bar you see 200 deg or something like that. Say 10-20 deg spread is more typical. Velocity increases just alittle bit more because overall cfm is only increasing alittle bit more.
I guess there really is no general formula. Just need to compute the air properties at given temp and pressure. That specific volume is used to calculate cfm rate based on your air mass flow. Air mass flow is basically hp divided by 10. Thats rough estimate for mass flow in lbs per minute
Best i can simplify it is following assumptions.
10 psig of air at post cooler temp of 90 deg f which is a typical expected value most setups can see in a short run. Specific volume is 8.24. Use this for your cfm calc
15 psig of air at post cooler temp of 110 deg f, estimated typical post cooler temp, specific volume will be 7.103.
20 psig at 140 deg f lets say typical post cooler temp, specific volume is 6.40.
Use your estimated mass flow from turbo at that boost or your known/estimated hp level divided by 10 to get ur cfms.
2.5" pipe has area of 0.03409 ft square
3" pipe has area of 0.04909 ft sq
4" area of 0.08727 ft sq
Take cfm divide by 60 to get cfs and divide by pipe area to get velocity.
600 hp 5.3 on 10 psi would have 494 cfm. 167 feet per sec velocity in 3" pipe. Imo i see no reason to run more than 150-200 fps so 3" is perfect.
800 hp 5.3 on 20 psi would have cfm of 512 cfm. Velocity is now 174 fps in 3" pipe
See its not a significant gain in speed.
Just for the sake of argument, I’d ask what possible gains could be had keeping the FPS lower than .4 MACH (whatever that may be at “X” temp and “Y” density)?
The reason to run more than 150-200fps would be to reduce the system volume. . Also I’d think with any heat exchanger an increase in velocity without excessive resistance through the exchanger would improve the heat transfer coefficient/ efficiency? Faster you could get the charge in/out of the IC the better it would work.
I want to say slower velocity thru system would make for a better overall velocity profile in the pipe. Less turbulence around the bends and coupled points. Less flow loss so less overall pressure drop across the system.
I think in plenum transition into the intake, slower is better for distribution. Air mass as dense as it is in boost doesnt like to turn. Same concept applies in head ports, over the short turn, if air is too fast it can separate from the boundary flow layer and go turbulent causing flow stall. Just an idea
I think in plenum transition into the intake, slower is better for distribution. Air mass as dense as it is in boost doesnt like to turn. Same concept applies in head ports, over the short turn, if air is too fast it can separate from the boundary flow layer and go turbulent causing flow stall. Just an idea
