Would an upgraded top mount IC be feasible/worth it on Fc's? I've heard that getting a front mount increases lag perceptively, so wouldnt the upgraded top mount both keep lag down while improving performance? (and would it even fit?)

 

I don't think a top mount is worth it because there really isn't much room for a significantly larger intercooler, and the airflow through the hood scoop isn't very good.

An FMIC in itself doesn't necesarily increase lag. However, lag will increase with an increase in the volume of the intercooler and piping. Pressure drop due to piping bends or other restrictions will also increase lag since the turbo will need to spin faster to produce the same boost at the manifold, and it takes a little more time for the turbo to spin faster. This is why it is important do try and reduce the amount of bends in the piping, and also to research intercoolers so that you don't use one with a lot of pressure drop at your estimated airflow and boost levels.

 

Yeah, theres a point where topmounts just blow, even the big ones.
You ever seen the air flow sheet for the FC3S? The hood scoop is garbage, it's really not that efficient. Maybe a cowl, or vent would be better
But FMIC is best for heat exchanging, and just make sure your intercooler piping is properly sized (not way too big, or too small). And make sure it's a good FMIC (although most will be fine, some are more efficient than others)

 

One of the neatest IC setups for the 2nd gen that I've seen was an HKS air to water IC that kept the intake air heat exchanger in ths stock location and had the heat expulsion exchanger mounted in front. Looked like the best of both worlds. Air to water heat exchangers are generally far more efficient than air to air given they take up the same volume.

I saw that set-up in a magazine in '87 and have never seen one since.

 

They do tend to have much less pressure drop, but they are generally only more efficient as long as the coolant is chilled. Therefore, they are really only useful for short duration events like drag racing. Also, they weigh a lot, are more complicated, and more expensive than air/air ICs. The air/liquid IC does have a space advantage because its components can be spread out in different locations of the car, while an air/air intercooler needs a single large space.