czb83
02-02-2007, 03:39 AM
Hello, first post here(just found forum after searching for turbo jeeps). I've been researching on how to turbo my Jeep cherokee with a 4.0L I6 engine. I saw a few post regarding turbos and Jeeps, so thought this might be a good place to ask for help. I've already researched fuel/ignition, and decided on MegaSquirt, which I am currently tuning. Ive actually drove around town, but there a couple bugs left(wiring issues).
Anways, I've been trying to decide on a turbo, but there so much variations on turbos its seems, that its hard to pick one. I've followed the guides, but was wondering if someone here might be able to help. Heres some calculations I have done.
(CID × RPM) ÷3456 = CFM
(242 * 5250) % 3456 = 368 CFM
368 * .85VE = 313 CFM
(10 + 14.7) ÷ 14.7 = 1.68:1 pressure ratio
T2 = T1 (P2 ÷ P1)0.283 = temperature rise
T1 = 80F + 460 = 540R
P1 = 14.7psi
P2 = 14.7psi + 10psi = 24.7 psi
T2 = 540 (24.7 ÷ 14.7)0.283 = 625 R
625R -460 = 165 F inlet temp ideal
165 - 80 = 85F increase
Ideal Outlet Temperature Rise / AE = Actual Outlet Temperature Rise
85 / .7 = 121F actual outlet temp rise
80 + 121 = 201 °F Actual Outlet Temperature
(Inlet °R ÷ Outlet °R) × (Outlet Pressure ÷ Inlet Pressure) = Density Ratio
(540 ÷ 661) × (24.7 ÷ 14.7) = 1.37 Density Ratio
Outlet CFM × Density Ratio = Actual Inlet CFM
313 CFM × 1.37 = 429 CFM Inlet Air Flow
429 * 0.069 = 29.6 lbs/min
Anyways, the calculation i did here is for 10lbs of boost. I'm making about 200hp stock, i'm looking for about 300. 10lbs boost = 1.68PR which would equal 36.3 lb/min of flow, but I did calculations for air temps and found PR to be 1.37(wow!). So when looking at a flow map, do I plot 1.37 against 29.6lb/min(from calculation with temp increase). 1.37PR = about 5lbs boost. Originally i plotted 1.68 against 36.3, but that was without air intake calculations. Does this mean I have to choose turbo that produces more boost than i want, because after air expansion, it ends up being less?
In the calculations above, it put in 10lbs boost, i end up with DR of about 5lbs of boost. Alright, I think i'm confusing myself now. Anyways, after doing these calculations, a t04B 60-1 trim looks perfect. Does this look good, or are my calculations wrong? Should I take into account intercooler when choosing one, because it would lower temps, and my turbo wouldnt have to flow as much to get same power, or is that completely wrong?
Phew, that was long first post. Well, I'll take advice I can get, as I'm a little lost right now.
Thanks
Anways, I've been trying to decide on a turbo, but there so much variations on turbos its seems, that its hard to pick one. I've followed the guides, but was wondering if someone here might be able to help. Heres some calculations I have done.
(CID × RPM) ÷3456 = CFM
(242 * 5250) % 3456 = 368 CFM
368 * .85VE = 313 CFM
(10 + 14.7) ÷ 14.7 = 1.68:1 pressure ratio
T2 = T1 (P2 ÷ P1)0.283 = temperature rise
T1 = 80F + 460 = 540R
P1 = 14.7psi
P2 = 14.7psi + 10psi = 24.7 psi
T2 = 540 (24.7 ÷ 14.7)0.283 = 625 R
625R -460 = 165 F inlet temp ideal
165 - 80 = 85F increase
Ideal Outlet Temperature Rise / AE = Actual Outlet Temperature Rise
85 / .7 = 121F actual outlet temp rise
80 + 121 = 201 °F Actual Outlet Temperature
(Inlet °R ÷ Outlet °R) × (Outlet Pressure ÷ Inlet Pressure) = Density Ratio
(540 ÷ 661) × (24.7 ÷ 14.7) = 1.37 Density Ratio
Outlet CFM × Density Ratio = Actual Inlet CFM
313 CFM × 1.37 = 429 CFM Inlet Air Flow
429 * 0.069 = 29.6 lbs/min
Anyways, the calculation i did here is for 10lbs of boost. I'm making about 200hp stock, i'm looking for about 300. 10lbs boost = 1.68PR which would equal 36.3 lb/min of flow, but I did calculations for air temps and found PR to be 1.37(wow!). So when looking at a flow map, do I plot 1.37 against 29.6lb/min(from calculation with temp increase). 1.37PR = about 5lbs boost. Originally i plotted 1.68 against 36.3, but that was without air intake calculations. Does this mean I have to choose turbo that produces more boost than i want, because after air expansion, it ends up being less?
In the calculations above, it put in 10lbs boost, i end up with DR of about 5lbs of boost. Alright, I think i'm confusing myself now. Anyways, after doing these calculations, a t04B 60-1 trim looks perfect. Does this look good, or are my calculations wrong? Should I take into account intercooler when choosing one, because it would lower temps, and my turbo wouldnt have to flow as much to get same power, or is that completely wrong?
Phew, that was long first post. Well, I'll take advice I can get, as I'm a little lost right now.
Thanks