Can any of you chemistry experts tell us if adding a cold air intake will actually make a difference in air temperature once the air has been compressed in the turbocharger?

The ideal gas law states that

(P)ressure X (V)olume = moles of gas(n) X gas constant(R) X Temperature

PV = nRT

The value for R stays the same no matter what P,V,n and T are doing.

If you decrease the temperature (T) you also must decrease the volume since we all know air expands as it gets hotter and contracts as it cools.

However, if you've ever owned a manual boost controller, you know that in colder weather, you have to turn you MBC down b/c your boost level rises with a decrease in temperature.

We can then deduce that as the temperature drops the quantity of air (n) ingested with each revolution of the compressor wheel increases which in turn increases the pressure (P) of the turbo at any given RPM....i think.

But does this mean that the air exiting the compressor housing is the same temperature no matter what the ambient air temperature is? I'm confrused........

 

No, the volume is a constant. If temperature decreases, and pressure remains constant (boost pressure), then the number of moles of gas must increase.

More moles, more power.

If the temp is lower, the turbo doesn't have to spin as fast to produce the same boost pressure. So the air coming out of the turbo will be lower. Lower temp, same pressure, more moles, more power.

 

Not to forget our cars run off MAS which is garbage. Our cars measure the amount of incomming air and adjust fuel and whatnot as it does for it. Where as MAP sensors adjust fuel and whatnot according to pressure. Which is why most stand alone units use them, as well as you can flow a good deal more air in by junking the stock honeycomb MAS.

Then there are the cars running both a MAS and a MAP sensor.... interesting.....

 

MAF kicks ***.

Systems that use MAP rely on volumetric efficiency to figure out airflow, which can vary.

MAF systems instead measure actual airflow.

 

too bad airflow changes do to ambient air's density... which is why i say they suck, with a map sensor you can basicly run an open turbo intake . That is if you didn't care about possibly bending some compressor fins from random bugs or other things.

 

Uhh, the MAF measures the ambient air's density using a barometric pressure sensor. It corrects the airflow using the pressure. It also mesures air temp and corrects for that. It is very accurate.

The sucker just wouldn't work if it didn't correct for those two things. And it does work, and it works very well. It is one of the reasons that Mitsubishis are so easy to modify.

And the MAF in the Evo is good for over 450hp to the wheels without modification. With modification, the sky is the limit.

 

MAF does not measure pressure, it has an air flow meter in it. It measures volume of air.

And yes i know how much power the stock MAF is good for, i believe it's 450 to the motor after that it can't flow enough air to support the power, it looks to be the same MAF as VR4's but I can't confirm that. But there is no way you can tell me it's better then running no MAF. Think about that one why do 90% of all stand alone fuel management systems use a pressure sensor over a MAF meter.

 

Dude, the MAF has 3 sensors in it. One is a Karmann Vortex sensor. That measures mass airflow. There is also a temperature sensor. And there is a barometric pressure sensor.

Look it up in the 2G DSM Technical Manual. Also look it up in the Evo Technical Manual.a

 

I retract my previous statements, SHAPEGSX sorry about that... just took out my MAF today and it is a newer design compaired to what i've seen on the VR4's and Eclipse's. This one does infact contain a barometric sensor.

 

The VR4 and Eclipse also have barometric pressure and temp sensors. In fact, the Evo MAF looks identical to the 2G DSM MAF.

 

MAF stands for Mass Air Flow. The Mass is what we are concerned about. Mass is the n in PV=nRT. All MAFs should account for T and atmospheric P in order to be called a MAF.

 

No the temperature varies with ambient. The temperature increase is the fixed part. For a given turbo setup there is x amount of temperature increase based on the turbo effiency among many factors. The is a really good article in SCC (last month?)

 

Not to chime in on your evo ??'s but doesn't the evo have both a MAF and MAS? I know the regular Lancer does which makes for perfection in AFR adjustments.(if you can program them thru piggyback/reflash) I would think the evo's would be the on that note. My testing showed what timzcat stated. Compressor temp increase was the same but when you lower ambient/injestion point temp you consequently lower temps at TB. The engine bay on me was 120 degrees for my SRI turbo setup. Leading my TB temps well over 210 degrees under full boost. By going CAI those temps dropped down to below 160. But ambient dropped down to 70... 50 degree drop on both accordingly. Hope this helps out for a proving standpoint. Now i'm really curious about the evo's sensors!

 

Basically it does. They call it a Manifold Differential Pressure Sensor or MDP.

 

The MDP is only capable of reading vacuum. It is only there to test whether the EGR valve is working. The car runs fine without it (though it does get a CEL if it is removed).