Diesel Cold Air Intake

[spyder]

Its Friday, but try this :-

Pressure Ratio

• Pressure Ratio ( ) is defined as the Absolute outlet pressure divided by the Absolute inlet pressure.
  
  
  
  
  
  Where:
  • = Pressure Ratio
  • P2c = Compressor
  • Discharge Pressure
  • P1c = Compressor Inlet Pressure
• It is important to use units of Absolute Pressure for both P1c and P2c. Remember that Absolute Pressure at sea level is 14.7 psia (in units of psia, the a refers to “absolute”). This is referred to as standard atmospheric pressure at standard conditions.
• Gauge Pressure (in units of psig, the g refers to “gauge”) measures the pressure above atmospheric, so a gauge pressure reading at atmospheric conditions will read zero. Boost gauges measure the manifold pressure relative to atmospheric pressure, and thus are measuring Gauge Pressure. This is important when determining P2c. For example, a reading of 12 psig on a boost gauge means that the air pressure in the manifold is 12 psi above atmospheric pressure. For a day at standard atmospheric conditions,
  
  
  12 psig + 14.7 psia = 26.7 psi absolute pressure in the manifold
• The pressure ratio at this condition can now be calculated:
  
  
  
  26.7 psia / 14.7 psia = 1.82
• However, this assumes there is no adverse impact of the air filter assembly at the compressor inlet.
• In determining pressure ratio, the absolute pressure at the compressor inlet (P2c) is often LESS than the ambient pressure, especially at high load. Why is this? Any restriction (caused by the air filter or restrictive ducting) will result in a “depression,” or pressure loss, upstream of the compressor that needs to be accounted for when determining pressure ratio. This depression can be 1 psig or more on some intake systems. In this case P1c on a standard day is:
  
  
  
  
  14.7psia – 1 psig = 13.7 psia at compressor inlet
• Taking into account the 1 psig intake depression, the pressure ratio is now:
  
  
  
  
  (12 psig + 14.7 psia) / 13.7 psia = 1.95.
• That’s great, but what if you’re not at sea level? In this case, simply substitute the actual atmospheric pressure in place of the 14.7 psi in the equations above to give a more accurate calculation. At higher elevations, this can have a significant effect on pressure ratio.
• For example, at Denver’s 5000 feet elevation, the atmospheric pressure is typically around 12.4 psia. In this case, the pressure ratio calculation, taking into account the intake depression, is:
  
  
  
  (12 psig + 12.4 psia) / (12.4 psia – 1 psig) = 2.14
  

  Compared to the 1.82 pressure ratio calculated originally, this is a big difference.

  
  
  
• As you can see in the above examples, pressure ratio depends on a lot more than just boost.
• 
  
  
  ◊ Mass Flow Rate
  • Mass Flow Rate is the mass of air flowing through a compressor (and engine!) over a given period of time and is commonly expressed as lb/min (pounds per minute). Mass flow can be physically measured, but in many cases it is sufficient to estimate the mass flow for choosing the proper turbo.
  • Many people use Volumetric Flow Rate (expressed in cubic feet per minute, CFM or ft3/min) instead of mass flow rate. Volumetric flow rate can be converted to mass flow by multiplying by the air density. Air density at sea level is 0.076lb/ft3
  • What is my mass flow rate? As a very general rule, turbocharged gasoline engines will generate 9.5-10.5 horsepower (as measured at the flywheel) for each lb/min of airflow. So, an engine with a target peak horsepower of 400 Hp will require 36-44 lb/min of airflow to achieve that target. This is just a rough first approximation to help narrow the turbo selection options.

[COLVERT]

When you compare the lower pressure ratio to the higher, is the lower figure better ??

If so, would a higher than atmospheric pressure on the intake side also improve the ratio ?? ( ie. above 14.7 psi at sea level. )

[spyder]

The lower the pressure ratio the better. But this would take sensors in the position that your MAF is in , in order to measure the loss, IE compared to psia(14.7). It is basically this ratio that weare trying to improve in a perfect world. The absolute manifold pressure will then start to change with a bigger or different Turbo.
THe BMW VV turbo increases this, but I have no idea what sensors or data they use for this.
Of course all these readings, after the turbo can be changed at higher and full boost by controlling the waste gate. As with a lot of performance cars, the EVO Lancia (4WD) use electronically controlled boost system, operated from the cockpit. The spring mod on our cars help. Not that I would try it .

In answer to your question, yes increasing the 14.7 psia would help, and there-in lies the problem. Anyone out there with a spare wind tunnel ?

[Jakg]

Been wanting to do this for ages, finally got round to it.

What I had before (air intake mod as done by the previous owner):





With the FBH in the way it was a massive pain to get in... but I did eventually. Does pinch the EGR pipe a little... Should of gone for a little smaller pipe I think.



Had to cut the engine cover a bit (although I did it a lot more than I needed to, ooops)



You'd never even be able to spot it...





The pipe currently sits behind the headlight.

Throttle response seems a little better (although could be a placebo). Doesn't sound any different.

[Departed 32016]

I too am going to do this mod, I have just got the pipe but i will put it next to the fog light with a bit of mesh around it.

[mark_bonsai]

You need to connect the other end of the pipe to one of the venturis (shown below) that are normally on the end of the shannon tube on a V6, etc. This bolts in place inside the passenger side front wing at the front. A good area for pressure and well out of the way of water.

[Roverron]

The Mk2 intake mod is easy to do for those who don't want to start running ducting and one of the reasons for it was to avoid the engine ingesting spray.
Even with the factory deflector modification fitted this still happens due to the depression at the opening.

Since air still flows into the engine compartment through the original aperture under the slam panel, its only when stationary or moving very slowly that warmer air will be drawn in, which hardly matters at these speeds.

Ducting may be better, though where's the proof? But the intake must be located where spray cannot be sucked in.

Ron

[Roverron]

Originally Posted by kieranswood

I too am going to do this mod, I have just got the pipe but i will put it next to the fog light with a bit of mesh around it.

Too low. What happens if you go through a flood?
Needs to be at headlight height or behind them as others have done.
Ron

[spyder]

Just a question after watching this post. Has anyone worked out the difference in area between the standard inlet been opened and modified, and the inlet of this mod. Surley the bigger the inlet the more the volume will be. Also will the friction in the length of this mod not hinder the volume of air getting into the filter ?

Just asking.

Craig

[HarryM1BYT]

Flow of a fluid (air) is a function of the pressure / the size of the pipe /its length and the smoothness of the pipes bore bends etc..

How you work it out, I don't have a clue