FAQ |
Members List |
Social Groups |
Calendar |
Search |
Today's Posts |
|
Pontiac - Boost Turbo, supercharged, Nitrous, EFI & other Power Adders discussed here. |
Reply |
|
Thread Tools | Display Modes |
#1
|
||||
|
||||
A little "Math for the Boost Guys"
Example:
The Inlet Temperature is 70 deg F, the suction pressure is -0.5 psig (a slight vacuum due to Inlet Plumbing), the discharge pressure is 19 psig, and the efficiency is 72%. What is the discharge temperature? T in= 70 deg F + 460 = 530 deg R P in= -0.5 psig + 14.7 = 14.2 psia P out= 19 psig + 14.7 = 33.7 psia P out/P in = 33.7/14.2 = 2.373 (this is the pressure ratio) T out = (530 + 530 x (-1+(2.3730) raised to the power of .263 ))) all of this divided by 0.72 = 717.8 deg R - 460 = 257.8 deg F So the theoretical outlet temperature is 257.8 deg F. (I sure would like to have an intercooler to cool that hot air down before it goes into my engine.) So assuming a 70% efficient inter-cooler 257 deg F – 70 deg F ambient temp = 187.886 deg F Temp rise from the turbocharger compressor So if you have a 70% efficient inter-cooler: 188 deg F times .70 = 131 degrees of temp removal So the discharge air out of the intercooler is 56 deg f hotter than ambient temp. The actual Air Temp going into the engine is 126 degrees at 19 psi boost pressure Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#2
|
||||
|
||||
Quote:
Most use .283 but it would be closer to .2857. But that would be negligible. But the .263 is off about 16º
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
#3
|
||||
|
||||
Thanks for catching the typo on the .263 vs the .283 commonly used in MacInnis book or the .2857 number that some use today.
Any more suggestions? Tom V. Note to members, Constants are constantly being redefined. Most of the Historical ones like the MOLE were redefined again this year. https://chemistry.stackexchange.com/...fined-for-2019 So don't worry too much about someone posting a number as being gospel for eternity, it does not work that way in engineering. 2019 redefinition of the SI base units https://en.wikipedia.org/wiki/2019_r...ase_units#Mole So take numbers for the most part as a close approximation in formulas. Good info, John, in my case a typo, in your case you need to do more reading as your number is not absolute either by any means. Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. Last edited by Tom Vaught; 10-09-2019 at 10:13 AM. |
#4
|
||||
|
||||
Quote:
If anyone tries to work this out the bold line has extra ( ) (530 + 530 * (-1 + (2.3730 ^.263))) / .72 = 923.94619 530 + 530 * (-1 + (2.3730 ^.263)) / .72 = 717.83508 Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#5
|
||||
|
||||
Thanks Stan, typing is not high on my skill set.
Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
Reply |
|
|