Charge-air cooler is the thing people usually think about when saying intercooler.

Engines with compressors (such as TurboChargers) benefit from cooling the charge air after the compressor has compressed the air (unwanted heat is also produced). The benefit is less tendency to knock, better efficiency, finally higher output from the same displacement.

There are 2 types of intercoolers:

Both are possible to buy or make in the garage.

I thought of making a long tube-like water-air intercooler:

from a lot of small diameter Al tubes (air inside, water outside), with 4..5 mm internal diameter. Putting them close to each other. Very close at the 2 ends (epoxy could seal?) and a little further from each other along the tube so water can flow between the tubes (water needs smaller cross-section than air).

The tube-collection can be embodied in carbon fibre to hold the water back. Maybe the first layer must be fiberglass poliesther to prevent Al + carbon corrosion (I read about that a recumbent builder's page), maybe the whole encapsulation can be done with fiber strenghtened poliesther (cheaper than kevlar).

The hard part is probably the sealing at the ends of the tube. Air-drag due to tubewall thickness of is also an issue, but you can make a small-angle cone driller for this purpose.

If you have some numbers for the drag inside a tube, please post it (or link) here. We can put together a sizing-helper program (eg. in perl). I calculated the heat-transfer, but not the air-pressure drop.

I haven't done it, just thought about.


It was reported that sg. like that is available on some import (usually means Japanese and Korean I think) turbo engines.

Intercooler Links

Intercooler Calculations:

See also