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Intercooler piping ?...

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Hi guys!


It's been a long hard road the last 5 years and needless to say the '83ZXT project has been on hold.


I've done my due diligence and for the life of me cannot understand why you would have the same size pipes before and after the intercooler.


To me, simple physics would lead me to think that a smaller pipe after the intercooler would provide less pressure loss because cooler air is more dense and a smaller pipe would keep the pressure and speed up whereas the same size piping would cause the pressure and speed to drop.


In the real world is the difference too small to consider?


Would the numer of bends and length of the tubing after the intercooler enter into the equation?


This inquiring mind wishes to learn...

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The only pressure that really matters is the pressure at the intake valves.  In order for that pressure to be as high as possible, you need to minimize the pressure drop (aka head loss) through the system.  This would lead you to believe that bigger is always better, but you are balancing it with minimizing turbo lag and having to pressurize a large volume.  


Besides, pressure and velocity aren't linked the way you are talking about anyway.  Physics (more specifically Bernoulli's equation) says that if you make the pipe size smaller, velocity goes up but pressure at that point goes down.

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You are correct that post charge cooler (the correct, but unused, term btw) the air will be denser.


But I like math so lets set an example:

Pre cooler @ 0.8bar (11.5psi) @ 76% Efficiency and 1L of compressed air you have 0.059 Moles of air at 95c

Now if you cool that same mass of air through the charge cooler @70% Efficiency and 0.5psi pressure drop the air will be 43c and use a volume of 0.88L. 


So post cooler the air is 88% the volume it was at the start.


A 2in pipe  has  a cross section area  of 3.1in^2 

A 2.5in pipe has a cross section area of 4.9in^2 (156% Bigger)

A 3in pipe  has  a cross section area  of 7.1in^2 (225% Bigger!)


So you can see the actual volume of air isnt changing as much as you think. Unless you are boosting stupid levels 100psi+ like Diesel guys. Also in the real world is much easier just to stick with the same size pipe. Plus you also have to deal with a set size on the Throttle body and turbo outlet. 


Anyway. Don't just listen to this armchair engineer keep on googling. The world is full of different answers. 

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"a smaller pipe would keep the pressure up"...



Remember my words regarding turbocharging always:




You don't WANT the speed, nor the pressure "up"! You want it flowing with as little loss as possible at the highest density possible.

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