Discussion: Intercooling - which is best?

When a car is running forced induction - be it turbo or supercharged, the air passing through it will rise in temperature due to compression. The higher the boost, the greater the rise in inlet temperature. Also, with turbos (at least in my case) there is a baseline temperature rise even when off-boost.

This can be attributed to the fact the compressor housing is attached to the turbine and therefore soaks up heat from the "hot" side of the turbo. On a 20'c day, off -boost i will typically an outlet temperature of 50'c - therefore a temperature delta of about 30'c as a penalty for running the air through the turbo. Running the water lines to the turbos didn't make any difference to this figure.

Many people say that for low boost applications (6-8psi / .5 bar) that there is no need to run intercooling. I did indeed run the car for quite a while with no intercooling and it performed fine. Although on a hot day, i would see inlet temperatures peak at 90'c (194'f) - which I considered to be too high for making best power. So i decided some form of cooling was required (and i like researching this sort of thing)

Two methods of cooling your charge temperatures exist:

Front Mount Intercooler (FMIC) or also known Air to Air

and

Chargecooling or sometimes called Air to Water cooling. (but probably more accurately Air to Water to Air)

The debate over which type is best continues to roll on, I think its less about which is best, but which is more suitable. The quick answer in my opinion is:

Air / Air Intercooling is the best form of cooling.

Air / Water is the second best.

Benefits of intercoolers: Simple

Effective

Lightweight Cons: Requires quite high air flow to be effective

Requires long and bulky charge pipes to be plumbed round engine bay

Boost lag because of volume (i wouldn't get too hung-up on this factor unless running very long and large pipes)

Benefits of chargecoolers:

Compact

Good heatsink ability

Can be placed very close to engine (if not ON the engine)

Flexible - can increase water capacity, pre-rad size to improve effectivness Cons: Not as efficient as intercoolers - The water is just a conduit of heat, you still need to cool the water back down

More plumbing

Requires a pump

Heavier

One of the only times a chargecooler can outperform an intercooler on a significant scale is by pumping COLD water through the core. An ice compartment is placed in the boot, where the water is pumped over it, this can achieve inlet temperatures LESS than ambient. This is only of use on the drag strip or on dyno shoot-outs - but a useful benefit none the less.

All coolers whether a air/air or air/water are also heatsinks, Chargecoolers provide the best heatsink capability due to the fact that they contain water - in fact adding more water is easy on increases the ability of the cooler to absorb heat without having to (immediately) dump that heat - which I will go onto demonstrate here.

Chargecooling usually eases packaging constraints. The chargecooler can be placed close to the turbo or manifold. The pre-radiators can be placed anywhere they will recieve a flow. There's no need route large 2 or 3 inch pipes through to your front bumper. The decision to chose an intercooler or chargecooler comes down to a few factors. I would say, explore the possibilities of fitting an intercooler first and if you cant find a good or easy solution - then look at chargecooling.

• Street use with speeds that provide constant air-flow over your cooler would steer towards intercooling.
• For Drag Strip, Dyno queen or packaging constraints - then a chargecooler provides good benefits.

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So if intercooling is the best - why did i decide to build a chargecooler then?

I have opted to go for chargecooling because I'm a cautious person who always likes to leave a reverse path to remove something if it doesn't work or I don’t like it.

I know an intercooler would provide good results on my car, but I didn't want to route pipes out to the front of the car, possibly cutting the bodywork - which isn't easily repaired. I was also worried that a large intercooler on the front of the car may block cooling air going into the radiator - whereas with the chargecooler placement, size and design of the pre-radiators is very flexible - if the car overheated due to lack of air flow, i could easily move them into the wings or even to the back or underneath of the car with a scoop to direct air-flow. This flexibility appealed, so that's the route I choose.