FMIC vs TMIC w/ ducted hoodscoop

[Splinter]

From what I've been reading, a FMIC is supposed to give you the best performance, but is far more difficult to install than a TMIC

So why cant we just put in a TMIC, and use a cowling to make sure its getting all the air from the hoodscoop?

Wouldnt that work nearly as well, with far less fabrication?

[dzx]

TMIC's tend to get heatsoaked after a while because they sit on top of the engine as the heat rises, it heats up the intercooler, making it less efficient. But for most applications, a tmic is more than adequate for whats needed.

[Richard]

There's much more lag experienced with a FMIC. That's something to consider also.

Once I get my TMIC in I'd like to experiment with a CO2 cooling system. Sounds pretty easy. So does a chunk of dry ice on top of the IC.

[BAC5.2]

Not really that much more lag with a FMIC. It takes the engine something like 12 RPM to flow the air contained in the piping and core of an FMIC.

The only major suffering is throttle response, but even that isn't bad. Driving my friends WRX with a front mount, feels exactly like driving it when he had the top mount.

[azn2nr]

front mount for the win. i have no problems with mine. and instaling it once you have done it the first time is a snap.

[sammydafish]

There's much more lag experienced with a FMIC. That's something to consider also.

there is no lag with a FMIC compaired to a TM .... the amount of time it takes the turbo to pressurise the aditional piping is only a few milliseconds, basicaly, it's not even a factor


the additional piing ads complexity and the aditional turns and length ad flow resistance and will show an increased pressure drop and therefore increased pumping losses as compaired to a top mount, so that's a bad thing for them, though if designed well and using all mandrel bends, this isn't that big of an issue.

if ducted well, the top mount should be able to be just as efficient as a front mount, the only other downside is that it will heat soak during slow movement, idling or when the car is off.

[dzx]

I wonder where people got the idea that it takes a long time to fill a fmic.

[Richard]

I wonder where people got the idea that it takes a long time to fill a fmic.

More piping to fill?

Would it matter much what size pipe you used? 3" vs 2.5" vs 2"? What kind of pressure drop would you experience? I think I may have found an alternate quest if there's not much lag. But how much of a loss in throttle response are we talking about?

[BAC5.2]

Milliseconds of additional throttle response lag.

I bet people associate increased lag with an FMIC because they also upsize the turbo.

Oddly enough, on my friends car, we did the FMIC, then downsized the turbo, lol. VF22 to VF30.

As far as a top mount being as efficient as a front mount.... are you serious? Consider, for a second what you are saying....

The TXS Superlarge TMIC had, roughly, 1/2 the thermal mass of their post-Hyperflow FMIC. How can something with SIGNIFICANTLY less thermal mass, located in a MUCH hotter area, with horrible airflow (relative to the frontal area of the car), be more efficient?

Subaru used a TMIC for 2 reasons. 1) Turbo location. It's on the back of the motor, it's easy to toss an intercooler between it and the throttle body. 2) It's cheaper. It's a slightly less efficient design (Tube/Fin instead of bar/plate), and it's cheaper than an FMIC.

[azn2nr]

^^^exactly. when i went front mount i went with a vf39 and kept the stock exhaust minus the stock muffler which i replaced with one of thoes ebay deals. the turbo spool up was incredible and the responce was out of this world. it was almost like stock but with more power. then i went to 16g still on stock exhaust, little more lag because its bigger and older but has more punch when it hits, gives you that feeling deep in your stomach that the 39 did not. all in all the only difference in responce had to do with the turbo. the front mount had nothing to do with it.

also of note. the reason most people doubt the remote or rear mount turbo systems made by sts is because of the length of pipe which in most cases only about 6 feet. their setups work perfectly and have minimal lag related to chargepiping. if their chargepiping had issues because of length subarus with front mounts would even be worse. my pips measure exactly 12 feet minus the core and endtanks. with the core its more like 15 feet. my pipes are also run very similar in style to the aps systems but what little thoes have in less piping they make up for in a hugenorumus core and endtanks, something like 30x12x4.

[BAC5.2]

Jason - People also have problems with the STS turbo kits because of the length of exhaust pre-turbo. There is 6 to 8 feet of pipe, which is great for letting the exhaust cool down a lot.

That's why EVO's are so sweet. They can make 30psi at 4000 RPM. Exhaust goes from the port, 3" to the turbine inlet. Fucking sick.

[THAWA]

I wonder where people got the idea that it takes a long time to fill a fmic.

Speculation. Pure unadulterated speculation.

[professor]

pehraps the extra lag results from the higher pressure loss for FMIC, not the theoretical time to fill the pipes

more pressure lost = less energy to spin turbo = bigger lag

when blowing a fan through pipes, the extra length of the pipes, numerous 90 degree fittings, joints in the pipes, etc all add up to a loss of energy

it may not be huge but it is certainly measurable

[tasq]

What kind of FMICs are you guys using?

[azn2nr]

im using a johnny race car 5 inch. im probaly gonna get a bigger one soon.

phil, think of it this way. uppipe is about a foot and a half cross pipe is a foot and a half lets say each of thoes cast iron things are 8 inches thats over 4 feet plus 15 feet of charge piping. now look at the sts kit which is say 8 feet back 6 feet to the front is still less than the combined 19 feet of pipe air has to move thorugh in my system. not starting a sts argument again but im jsut saying. its not like our system isnt exactly the smallest out there. by oem standards ours is the largest.

[tasq]

im using a johnny race car 5 inch. im probaly gonna get a bigger one soon.

phil, think of it this way. uppipe is about a foot and a half cross pipe is a foot and a half lets say each of thoes cast iron things are 8 inches thats over 4 feet plus 15 feet of charge piping. now look at the sts kit which is say 8 feet back 6 feet to the front is still less than the combined 19 feet of pipe air has to move thorugh in my system. not starting a sts argument again but im jsut saying. its not like our system isnt exactly the smallest out there. by oem standards ours is the largest.

Are these $1000 like the WRX ones?

[nzKAOSnz]

http://www.spdusa.com/big_intercooler.htm

ummm - trying to think of best theory behind this. I believe that a large FMIC will introduce more lag than a smaller TMIC.

[azn2nr]

it wanst to start out with but thats what it ended up being. my setup was full custom. i bought the intercooler for a few bucks mounted it and had pipes ran. if i knew the people i know now it would have been cheaper but since i didnt it was all told short of a grand. if you want a front mount get a ebay one for wrx. txs knock off, many people have had great luck with it and you just need to modify it to fit. alot easier than the way i went

[tasq]

it wanst to start out with but thats what it ended up being. my setup was full custom. i bought the intercooler for a few bucks mounted it and had pipes ran. if i knew the people i know now it would have been cheaper but since i didnt it was all told short of a grand. if you want a front mount get a ebay one for wrx. txs knock off, many people have had great luck with it and you just need to modify it to fit. alot easier than the way i went

Awsome! I will look into it Thank you!

[sammydafish]

As far as a top mount being as efficient as a front mount.... are you serious? Consider, for a second what you are saying....

The TXS Superlarge TMIC had, roughly, 1/2 the thermal mass of their post-Hyperflow FMIC. How can something with SIGNIFICANTLY less thermal mass, located in a MUCH hotter area, with horrible airflow (relative to the frontal area of the car), be more efficient?

you're not comparing apples to apples. obviously a larger IC will be able to absorb and dissipate more heat. The largest benefit to a FM is simply that you can fit a larger one. If they were the same IC in different locations they would perform similarly at speed. Properly ducted, the FM does get more air and usually cooler air, but they are also often not ducted correctly and most of the benefit is lost because people leave off things like engine undercovers and don't put ducting between the bumper entrance and the IC. Plus the fact that the air must flow through the IC, A/C condenser and the radiator creates significant pressure passing though the IC, so again, without proper ducting it becomes less effective at speed.

Basically, both locations have the same issues. The trade off is increased complexity and added cost for a front mount. The benefit is slightly greater airflow and the possibility of being able to fit a larger unit. The TM has the benefit of being simple and significantly cheaper and more compact. The downfall is a limitation on packaging and a possible heat soak issue at low speeds and idle.

Everything is a compromise.

Subaru used a TMIC for 2 reasons. 1) Turbo location. It's on the back of the motor, it's easy to toss an intercooler between it and the throttle body. 2) It's cheaper. It's a slightly less efficient design (Tube/Fin instead of bar/plate), and it's cheaper than an FMIC.

I agree, given their constraints (packaging and cost), they choose the best option with minimal compromise for the situation. It works well, maybe not perfect, but for their intention, it does just fine.

[hackish]

Internet parrots have been blindly repeating the lag story for years. I've done dozens of FMIC kits on a variety of cars and have yet to detect a noticeable amount of lag. In many cases replacing restrictive factory piping and poorly flowing factory IC's give less lag.

-Michael

[dzx]

I agree, my Fmic didnt add lag, however removing the heat shields on the exhaust manifold created quite a bit.

[Legacy777]

I agree, my Fmic didnt add lag, however removing the heat shields on the exhaust manifold created quite a bit.

Removing heat shields created lag?

[93forestpearl]

I could see that. The heat sheilds may act as a decent insulator. Just like the wraps. Sound plausible?

[Legacy777]

How????

If we're talking about "typical" lag caused by extra piping or more pressure drop.

Is there temperature associated turbo lag I'm not familiar with? I can see how a bunch of hot air might cause a little knock and cause the ECU to pull timing, but I wouldn't call that turbo lag.