I have a http://www.scangauge.com/ installed in my FXT for several months now. One of it's many features includes a reading of the intake air temperature. Something I've noticed is that when the temperature outside is XX degrees, the intake temp is about 4 degrees F hotter when I'm cruising on the freeway. After a drive, having the car sit for a while (5-30 min) will heat soak the stock FXT intercooler pretty bad. Bad up to ~130 degrees F intake temps at startup and idle. The intake temps drops slowly in city driving, but drops very quickly once I get air ramming through it driving on the freeway. If 70% of my driving is on the freeway, would an upgraded intercooler (such as the Sti TMIC) benefit me for the 30% I'm behind the wheel? What is the benefit of an upgraded intercooler? [besides the fact that it fights against heat soak] :???:
big or small you will get heatsoak.. how bout a ater spray for when you start up, and/or in stop and go?
Yesterday I was out with the laptop connected to the car and was seeing temps of 90°F when cruising, getting up to about 110° after being stopped for a couple lights. TMICs just aren't very efficient. I don't think getting a larger one would help, in fact if you think about how restricted the airflow can be through the scoop it may actually be worse since it's far easier for heat from the engine to rise up and warm the IC than it is for cooler ambient air to come in and cool it.
Peaty from scoobymods mentioned that the ECU reads the intake temperature at the MAF sensor. Whatever I see on my scangauge is what the ECU sees at the sensor, not at the throttlebody--much less the heads. That's not good. A water sprayer would be the cheapest route for all-around cool intake temps, but I don't think I'll go through the hassle for my car. It's Minnesota; one of the coldest states in the US. )
A bigger TMIC will increase the volumetric efficiency of your engine dramatically. If the FXT stock topmount is even remotely similar to the WRX one, it is probably not a very efficient unit. The WRX topmount has nearly 3psi of pressure drop from inlet to outlet. Like Aaron said, any topmount is going to experience heatsoak in stop and go traffic. To get back to ambient temps as quickly as possible, you need a good seal between the intercooler and your hood scoop, so that the air coming in is directed over the intercooler and doesn't have a chance to get around it (behind or to the sides). I don't agree that TMICs aren't very efficient. A bar and plate TMIC with properly designed end tanks will cool intake air VERY well and have very little pressure drop, I can attest to that. You won't quite get the kind of temps you would with an intercooler hanging off your bumper, but on the other hand you get more lag that way too...so there are tradeoffs.
As for the temps, I would say that a tmix will have the same intake temps as a fmic under most driving situations. Stop and go traffic, the fmic will be cooler (at a cost) and the fmic will stay cooler at most track days. For general use, I would go with the tmic. The thing you have to rememeber is the turbo on the fxt is so small that a larger tmic won't really help to much. The stock tmic is very good at cooling the intake air temps. If you really want to maximize the stock ic, get a sti sized scoop and install a splitter. Russ
