hustler's "driver shame" thread
i would assume that the IC would have the same effect as a short ram vs the cai.
the temperature will drop a certain amount regardless of the starting temp... so you would ideally want both the cai and the intercooler together for a colder air charge
the temperature will drop a certain amount regardless of the starting temp... so you would ideally want both the cai and the intercooler together for a colder air charge
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Intercooled or not, it helps.
From SCC issue "10/2005"
Letter titled - "They" say dumb things
I just bought a 2004 SRT-4 and I wanted to change the factory intake. I was thinking about a cold-air intake, but I have heard from a few people that a cold-air will work the same as a short ram because the turbo heats the air to a constant temperature when it passes through anyway. Is this true? If you could give me some advice I would appreciate it. SCC is sick.
Answered by Dave Coleman
Dave goes on to explaint that:
"That hot-air-equals-cold-air theory is a steaming pile of cat poo wrapped in a thin veil of truth. the only true part is the turbo will heat the air anyway. The steaming cat poo comes right about the time "they" start saying the air coming out of the turbo is the same temperature regarless of the temperature going in."
"In the simplest terms, the air temperature actually increases a fixed amount going through the turbo. So if the turbo normally sucks in 60-degree air and spits out 160-degree air, sucking in 100-degree air will make it spit out 200-degree air."
"In reality, it's slightly worse than that. Actual temperature change across a compressor can be calculated with this arcane formula:"
Temperature Rise = (Tin*[pressure ratio^0.238 -1])/Compressor efficiency
"To make the arcane formula work you have to use absolute temperature on the Rankine scale for the inlet temp, which means you take Fahrenheit and add 460 degrees. So 60 degrees F is 520 degrees R."
"Pressure ratio is absolute pressure (boost plus 14.7 psi atmoshperic) divided by atmospheric pressure. So if you run 14.7 psi of boost, the pressure ratio will be 2.0. Let's use that 'cause it's easy. Then let's use 0.73 as the compressor efficiency, since I was born in 1973."
"In that particular case, the arcane forumla insists that air will come out of the turbo 128 degrees hotter than it went in (for a total of 188-degrees F). Now, if we increase intake air temperature to 100 degrees, the temperature rise is 138 degrees (again, a total of 238 degrees F). Air in went up 40 degrees, air out went up 50 degrees."
"In other words, cold air is important in any car, but it's even more important on a boosted one."
Phew - that was long, but sums it up, no?
From SCC issue "10/2005"
Letter titled - "They" say dumb things
I just bought a 2004 SRT-4 and I wanted to change the factory intake. I was thinking about a cold-air intake, but I have heard from a few people that a cold-air will work the same as a short ram because the turbo heats the air to a constant temperature when it passes through anyway. Is this true? If you could give me some advice I would appreciate it. SCC is sick.
Answered by Dave Coleman
Dave goes on to explaint that:
"That hot-air-equals-cold-air theory is a steaming pile of cat poo wrapped in a thin veil of truth. the only true part is the turbo will heat the air anyway. The steaming cat poo comes right about the time "they" start saying the air coming out of the turbo is the same temperature regarless of the temperature going in."
"In the simplest terms, the air temperature actually increases a fixed amount going through the turbo. So if the turbo normally sucks in 60-degree air and spits out 160-degree air, sucking in 100-degree air will make it spit out 200-degree air."
"In reality, it's slightly worse than that. Actual temperature change across a compressor can be calculated with this arcane formula:"
Temperature Rise = (Tin*[pressure ratio^0.238 -1])/Compressor efficiency
"To make the arcane formula work you have to use absolute temperature on the Rankine scale for the inlet temp, which means you take Fahrenheit and add 460 degrees. So 60 degrees F is 520 degrees R."
"Pressure ratio is absolute pressure (boost plus 14.7 psi atmoshperic) divided by atmospheric pressure. So if you run 14.7 psi of boost, the pressure ratio will be 2.0. Let's use that 'cause it's easy. Then let's use 0.73 as the compressor efficiency, since I was born in 1973."
"In that particular case, the arcane forumla insists that air will come out of the turbo 128 degrees hotter than it went in (for a total of 188-degrees F). Now, if we increase intake air temperature to 100 degrees, the temperature rise is 138 degrees (again, a total of 238 degrees F). Air in went up 40 degrees, air out went up 50 degrees."
"In other words, cold air is important in any car, but it's even more important on a boosted one."
Phew - that was long, but sums it up, no?
I wanna play.
Let boost be at 6 psi. The temp gain with turbo is about 14/15F per psi, or about 90°F.
On a 90°F ambient day, ambient absolute would be 90 + 460 = 550F.
The charge temp absolute would be about 550° + another 90° from the turbo, which comes out to 640°F
Density would degrade by 550/640 = .86
The pressure ratio at 6 psi is 1.41.
With the heat from the turbo, then the 141% more density from compression will be degraded by .86 x 1.41, or to about 1.21. Thus a huge chunk of the density/power was lost and the system is 90°F closer to knock.
With a 90% efficient IC, .90 of the 90°F temp rise will be taken out, or about 81°F removed, thus leaving a net gain of 9°F. This would leave a density loss of only 2% from the heat, or a net gain of 1.41 x .98 = 1.38, or an overall gain of 38% rather than the 21% without the intercooler.
This assumes the filter is in a position sourcing ambient air. Behind the radiator is one of the worst places, the temperate sourced from that area is going to be closer to 150-190°F.
So, let's compare:
perfect conditions; 90°F ambient + 8°F after intercooler + 460°F = 555F
unideal conditions; 90°F ambient + [(190°F intake + 90°F turbo addition) x 90% intercooler] + 460°F = 575F
550/555 = 2% density loss or overall gain of 38%
550/575 = 4.3% density loss or overall gain 34.8%
So if you dynoed at 160rwhp with the filter behind the radiator, you have a potential of a a 7rwhp gain if you simply moved the air filter to somewhere that would source ambient air.
something like that. where my dawgs at?
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Thread Starter
Joined: Jun 2006
Posts: 29,085
Total Cats: 375
From: Republic of Dallas
Thanks for the info on the CAI. Unfortunately I'm all out of aluminum sheets, I've misplaced my TIG, and I'm all out of time. I may take it to Alamo for sheet metal work. I'm also going to notch the BEGi heat sheild for the wastegate to clear. I don't want to hide the ABSURDflow glory though.
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No worries. The CAI is not a must-have. The lack of it should not keep you away from the track at any rate. It would be a nice winter project.
Go cowl induction CAI FTW
Go cowl induction CAI FTW
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Senior Member
Joined: Nov 2005
Posts: 846
Total Cats: 0
From: Austin, TX yall
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Thread Starter
Joined: Jun 2006
Posts: 29,085
Total Cats: 375
From: Republic of Dallas
Sport brake clip failure, carbotechs are king. I managed to drive all day withouttouching the hot parts. tim is the **** and gets tons of bitches.
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