Intercooler FAQ

The purpose of this thread is to address the advantages and dissadvantages of the two most popular intercooler upgrades for STI's.

The following will be addressed:

-FMIC advantages
-FMIC disadvantages
-When to consider a FMIC
-FMIC limitations
-TMIC advantages
-TMIC disadvanages
-When to consider a TMIC
-TMIC limitations
-how to increase an intercoolers effectiveness
-alternative intercoolers (AWIC, reversed intake manifolds, etc)

Feel free to help me with this by picking a section and writing about it. If you see a section you like post and claim it. I'll add your name next to it so no one will accidently cover the same subject.

When All the sections are finished Ill reformat the whole thread in an organized manner, repost the areas, and give each author credit at the top of each section. :tup:

Sounds good. I have to mull it over. I most likely will be picking a TMIC related subject because that is the only type I have any real experience with.

Let me put it simply. (Seriousness) If you're running a FMIC on a stock location turbo less than the 3076R variants, you're sacrificing too much. Spearco's TMIC flows 1k cfm/min, more than enough to handle a 3076R. (Jackassery) Yeah, you might have to do crazy things like delete your A/C when the supersized TMIC that allows sub-ambient IAT's @ WOT gets on your nerves with rubbing, but hey, sacrifices must be made, especially for better throttle response!


(Seriousness again) But really, if you're not running a 35R rotated or larger, there is no reason really to run an FMIC, unless you LIKE lag. Theory/Physics/what-have-you: Piping takes time to fill with compressed air, especially, what like 8-12' worth, not including the core. Then there's core construction, bar and plate (most efficient, Spearco, Perrin for example) or fin and tube (OEM; works but more restrictive, therefore less CFM with equal sized bar and plate). Those of you calling HEAT SOAK! Yes, it might heat soak in traffic or at a stoplight/x-mas tree, but as soon as you get airflow from forward movement, moot point (Edwin, step in with your positive pressure due to airflow crap!). And your full of it if you think that the close proximity to the largest heat exchanger in your car doesn't heat soak your FMIC either...just saying.


I might be bi-polar with my mood swings.....

STimedic is laying the smack down. Great points and I learned something. :ty:

You're right, I won't refuse.

A couple other things I just thought about, doesn't the TMIC act as a pseudo-plenum? If so, my Spearco holds quite a bit of air in reserve. Might also be contributing to my instant throttle response and another plus for TMIC.

STimedic said:

Let me put it simply. (Seriousness) If you're running a FMIC on a stock location turbo less than the 3076R variants, you're sacrificing too much. Spearco's TMIC flows 1k cfm/min, more than enough to handle a 3076R. (Jackassery) Yeah, you might have to do crazy things like delete your A/C when the supersized TMIC that allows sub-ambient IAT's @ WOT gets on your nerves with rubbing, but hey, sacrifices must be made, especially for better throttle response!


(Seriousness again) But really, if you're not running a 35R rotated or larger, there is no reason really to run an FMIC, unless you LIKE lag. Theory/Physics/what-have-you: Piping takes time to fill with compressed air, especially, what like 8-12' worth, not including the core. Then there's core construction, bar and plate (most efficient, Spearco, Perrin for example) or fin and tube (OEM; works but more restrictive, therefore less CFM with equal sized bar and plate). Those of you calling HEAT SOAK! Yes, it might heat soak in traffic or at a stoplight/x-mas tree, but as soon as you get airflow from forward movement, moot point (Edwin, step in with your positive pressure due to airflow crap!). And your full of it if you think that the close proximity to the largest heat exchanger in your car doesn't heat soak your FMIC either...just saying.


I might be bi-polar with my mood swings.....

Click to expand...

Thats my view exactly. :tup:

Except its more a long the lines of transient response than it is turbo lag. This is why the dyno's will look the same but if you were to go autocross you could feel it.

I just consider it lag time period. I love my near-instantaneous throttle response and wouldn't have it any other way.

TMICs are where it's at unless you're pushing 450+ then they become a little obsolete. Then It's time to move to a FMIC or a Vmount. or something crazy like Fuji.

PS I HATE YOU BEN GO TO WORK

Fuck you Jon, I'm ALWAYS at work. Just got off @ 2315 dick....

And btw, I mentioned my Spearco is rated for 1kCFM, P&L reccommends the Spearco with their 35R kit. I just wouldn't use it for a 3582R.

get tapatalk then so you can use the forums all day long on your phone!

Where's you find the in depth specs for you TMIC? I'm trying to find mine right now.

Tapatalk is the devil and doesn't work when you're in the depths of Ft. Bragg. I usually browse from my pphone throughout the day already......when I'm not busy with work.

STimedic said:

A couple other things I just thought about, doesn't the TMIC act as a pseudo-plenum? If so, my Spearco holds quite a bit of air in reserve. Might also be contributing to my instant throttle response and another plus for TMIC.

Click to expand...

Whether TMIC or FMIC, they're both in front of the throttle body. They'll both act the same in that regard.

TMIC advantages

-With a top mount intercooler the hot and cold side intercooler piping can be much shorter and easier to manage.
-Most times fewer bends are needed to get to where you want to go.
-Less pipe is needed decreasing overall cost of pipe.
-Shorter piping leads to less boost lag to the throttle body.
-Shorter piping also lets cold air reach the Throttle Body before it has a chance to gain heat back from being routed over the engine.

Disadvantages of TMIC

-Sitting right above engine can cause heat soaking at stops. Heat soaking can lead to lower performance for a short period after resuming movement.
-Increased cost of buying a new hood. Many times a new hood will need to be installed. Without a front scoop or proper shrouding an TMIC is completely useless. without air being routed over the fins and through the cooler it will heat soak.(kind of a given)
-Most TMIC's are limited to a max HP. This is completely dependent on dimensions of said TMIC.

There may be more disadvantages but i am not inclined to say what they may be. I primarily work with FMIC's. This means i will not post the HP limits or unproven disadvantages for TMIC due to lack of knowledge.

FMIC Advantages

-Less prone to heat soaking
-Higher HP's possible with supporting turbo and Mods
-Easier to mount to vehicle (universally speaking some vehicles it may be an only option not STI specific)

FMIC Disadvantages

-Longer pipe routing
-More bends will most likely be needed to get to where you want to be
-Increased cost of pipe and bends
-More difficult to fabricate piping, and disassembly of front end may be required to fabricate and install
-Longer pipe means it will take longer to feel the boost.(higher boost lag)
-If your FMIC is improperly sized could result in higher pressure drops across the intercooler
-If the turbo is not large enough the IC piping will heat the air back to pre-ic temps before it reaches the Throttle body

Picking your intercooler

Most setups you have to look at many different variables to find what will work best for you. Some of the main things to consider would be,
-The main use of the car in question
-HP expectations
-Supporting mods that will be done in the near future
-Turbo on the car when IC is installed

There may be more that you are taking into consideration but this is a pretty good start.
-Main use for the car in question
There are many different applications that a Turbo and Intercooler can be added. You need to figure out if this car will be used as a daily driver with small HP gains. Or on the other hand it could be an all out Drag racer that will be trailered to the track. These are very different ends of the performance spectrum. but knowing what you are looking for is the real start of a project.

Small HP gains using a stock or slightly larger sized turbo. This would be considered a daily driver, grocery getter or sometimes an auto cross application. On these applications where top speed is not the goal but getting to speed is, a TMIC would work very well. With shorter piping and a smaller intercooler in some cases, boost would be almost instant. This is good for getting to speed quicker and if used in an auto cross event will help with instant power coming off of short corners.

Medium HP gains are in the TMIC category as well. This will be with a slight variation of course. The TMIC may need to be a touch bigger dependent on HP goals of the car. Boost pressure drop may be a little more noticable with a very slight lag in boost. Still with the short length of piping it will take to install and TMIC it may not be noticable at all. (I will be honest this area is a little gray for me feel free to add info or edit if used)

High HP top speed critical cars. These are about the only class i would consider to be in need of an FMIC. FMIC's have many varying sizes. The longer the FMIC the more boost drop you will have across the IC. Larger IC's are better for high HP. with all the varying sizes there are much better chances to find one that will work for your goals. For high HP you will have a larger turbo to push the air faster through the piping. Even though there is more piping if your turbo can push the air through the piping fast enough the Intake Air Temps. will not increase enough to notice. It is still important to keep the IC piping as short as possible to cut down on boost lag.

It is a good idea to look at what will be going on the car in the near future also. This will save you money in the end and sometimes fabrication time. If you know you will be upgrading the turbo in a week there is no point in building a IC system to fit the turbo on the car at this time. If at all possible use the specs of the turbo and expected HP to build a system that will work well with the up and coming upgrades in store for the vehicle. Yes the car may feel a bit laggy for a week or two when your waiting for your new upgrades, but it will save you fabrication time, money in materials, and down time of the car.

If you are not looking to upgrade your turbo for a while please build the system to fit the turbo on the car. Building the IC system for high HP while using the stock turbo will in all reality hurt the car and your sanity more than anything. Driving a car that is laggy for extended periods of time will drive you crazy. If the turbo cannot flow enough to charge the system your fuel mileage may suffer with a stock tune. You will actually be seeing lower boost numbers and HP due to having to fill alot of extra space that it was not designed to do.

The fallowing is general information about turbo intakes and optimizing IC setups.

Throttle Body- The throttle bodys main purpose is to meter air flow into the intake plentum.

Plentum- The plentum is considered anything from the Back of the Throttle Body plate all the way to the back of the intake valve itself. Intercooler piping or charge piping is not considered a plentum for all intensive purposes.

Runners- Runners are the tubes that direct air into the head of the car. These if i remember correctly are used in plentum size calculation too.

I have a few base line rules to improve preformance of a turbo system. Short runners work better. There are calculators out there to help figure perfect runner length but most do not want to make their own Intake manifold from scratch. That is the only time shorter intake runners would even come up. The next two are not that bad and can be done with some effert and some research. Making the intake plentum larger helps with the performance or a turbo system. many times you can have 2 flanges made to fit the stock throttle body. you can extend the intake plentum by fitting a pipe to these two plates that moves the position of the TB and effectively increasing plentum size. Another would be to increase the TB size. This would involve finding a TB that is larger than stock, either aftermarket or something that can be fit to the car from another model. The aftermarket option is the prefered method. Increasing the TB size directly effects the throttle response of the car. without any other upgrades many times the larger TB will increase fuel mileage by a small percentage.

IC piping and optimizing it!!!
Like i have said many times before the shorter the IC piping the quicker boost will come in. Now as for IC sizing thats a little different creature. To fully optimize your IC sizing you will have to use two different size pipes. From the turbo to the IC most times use the same size as the outlet of the turbo. You may increase it slightly but the outlet of the turbo is usually plenty. This keeps the flow of the charge air constant from the turbo to the IC with no pressure loss at large openings. Once it goes through the IC the cold side intercooler piping should increase in size. As a rule of thumb i have always heard to inrease the cold side by about .25"(someone can correct me if they find different). So if your turbo outlet was 2.25" and your hot side charge pipe was 2.25", then your cold side charge pipe would be 2.5" instead. Cold side charge pipe would be considered from the Intercooler to the Throttle body inlet. As i have understood it in the past this lets the Air molocules spread out a little. With everything have a little more room your IAT (intake air temp) can stay lower from the IC to the TB.

Again thermo dynamics is not my strong suit so if anyone needs to correct me feel free to do so. I do know for sure that the size change does help in the performance of intercoolers and the turbo system as a whole.

Sorry this was the first thread i saw and i had to register. Hope this helps some.

Sentien thanks for the contribution! I'll be sure to include it. You single handedly covered a good chunk of the info. Its much appreciated :tup: