Thread: Beat The Heat
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Old 09-11-2009, 04:29 PM   #23
Scooby Newbie
Member#: 152819
Join Date: Jul 2007
Chapter/Region: SWIC
Location: Albuquerque, NM
06 STI
Aspen White


Originally Posted by Circuit Motorsports View Post
I will try and keep this short:

A FMIC is ideal for maximum intake charge cooling. It is the farthest you can get it from detrimental heat sources and is directly in the air stream. However, Subarus are designed to use a TMIC, so the manifold is pointing the wrong direction for a FMIC setup, so the piping has to be extra long.

So what happens when you step on the throttle and want power? The hot-pipe has to fill up, then the FMIC has to fill up (most are quite large, larger than necessary), then the charge pipe has to fill up, and finally, it reaches the intake manifold.

The result is "transient boost-lag". The biggest place this is felt is once you are in boost, turbo spooling hard and you come off the gas, then get back on the gas again. just vented all your pressurized air back into the intake tract our out into the open. You have to fill allllll that piping and FMIC up again.

I personally don't like this. I had an APS 525 FMIC on my STI, a really nice piece. But the lag was killing me. I decided to switch back to a TMIC and see what I was missing.

I was blown away by the throttle response I had forgotten about. Leaving from a dead stop was smoother. Power delivery was smooth and strong, no dips or huccups. Rev-matching was dramatically improved, so much so I had to learn to give it less gas than I had been with the FMIC. And most of all, coming off the gas, say to lift slighty in a turn, and getting back on the gas.....0 lag. Just instant response and power. Upshifts are more fun too, power is right there for you even short-shifting.

Needless to say, I am a big fan of a TMIC. You might leave a few horsepower on the table due to a slightly hotter intake charge, but I would take the drivability over a few HP any day. This can also be taken care of with a good setup, an intercooler sprayer or even water/meth injection.

Not to mention that a FMIC blocks your radiators airflow, making it less efficient. And your a/c condenser to a lesser extant...

This was longer than I wanted
AMEN! You speak the truth my friend! I'm running a fmic and will stick with a tmic on my next Suby. Throttle response and less lag ftw.
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