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Maximum Boost Corky Bell. Turbo, Intercooler, Blow Off Valves load of info

These 5 intercooler size calculators will tell you:

  • Intercooler efficiency
  • Intercooler size required for a given CFM
  • Air density increase through an intercooler
  • Intercooler flow/pressure loss
  • Intercooler pipe size/pipe diameter required for a given CFM

Assess the performance of an existing intercooler or find the correct intercooler size and intercooler pipe diameter for a given engine CFM flow or power output eg 300 hp, 400 hp, 500 hp etc.


The percentage increase will give approximately the same increase in power minus the drag inside the intercooler.


The percentage loss here will give the same approximate drop in power.

The benefits of designing or buying a low pressure loss intercooler should be obvious.


How close is the temperature of the air entering your engine to ambient temp. The closer the better. Negative numbers possible here with ice and/or water sprayer.


This is the key intercooler size calculator on this page

We are measuring the surface area that the charge air hits when it enters the intercooler. The length of the tubes are nowhere near as important as the number of tubes. The second half of the length of the tubes only does around 25% of the cooling.


To give an example of what we mean about intercooler fin orientation.

This intercooler which be much more efficient, than this intercooler

The intercooler on the left is more efficient than the intercooler on the right. The air entering the left intercooler has a much bigger area of core to hit, this gives greater cooling. This “area” is what the formula above calculates.

The length of the intercooler ie the distance between the inlet and the outlet is much less important that the area the charge air sees when it enters the turbo.

These intercoolers are from Road Race Engineering


Intercooler pipe size can be too small. If we are trying to force the air through at too high a speed, it can lead to exponential increases in drag.

We want the intercooler pipes to be as big as they need to be but without causing reduced throttle response. Having said that, bigger is better than too small.


Key Takeaways – Intercooler Size Calculator

The surface area of the charge air entering the intercooler is much more important that the length of the tubes in the intercooler (see Road Race intercoolers above).

Ducting can improve the power of an intercooler by as much as 20%. Stop the air from going around your intercooler. Place ducting around the edge of the face of the intercooler to force the air to go through it. Also, the entry to the intercooler duct does not have to be as big as the intercooler itself. The intercooler duct inlet can be as small as 25% of the total surface area of the intercooler. In any case, the duct inlet should be around 80% the size of the intercooler face at most.

Core thickness. Assuming you have the space, a thinner intercooler core is better because it will have a greater surface area facing the air as the car moves forward.

Bends. Factor in a one percent loss in pressure for every 90 degree turn in your intercooler piping. If you have 10 bend of 9 degrees, 1% pressure loss. 6 bends of 15 degrees, same thing, 1% pressure loss. Keep the number of bend to a minimum and if you can, make the essential bends a bigger diameter to reduce their restriction.

Turbolators. When sizing your intercooler, take into consideration the density of the turbolators on the intercooler fins. High density turbolator, bigger intercooler. No turbolators, smaller intercooler.


Further Reading

Maximum Boost by Corky Bell. This is a seminal book in DIY turbocharging. Easy to read, entertaining and filled with gold nuggets of information. Required Reading.

This book is required reading for anyone remotely interested in making their car go faster with a turbo. If it costs less than 50USD, it is well worth the money IMO
This page was last modified Aug 26, 2021 @ 2:21 pm

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