#670947 - 11/12/06 12:23 PM
Re: Explain the difference between FMIC and TMIC turbos
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Noob4Life
Post Master Supreme
Registered: 05/30/02
Posts: 26653
Loc: IL, USA
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afaik, part of the reason is because a Top Mount requires less plumbing, thereby getting the cooled air to the intake quicker. the downside is it is more susceptible to heat soak and requires fugly scoops to direct air onto the IC 
the front mount takes more plumbing to get air to the intake but can work more efficiently, you can use bigger sizes maybe.
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#670950 - 11/12/06 04:47 PM
Re: Explain the difference between FMIC and TMIC turbos
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AMGSiR
Post Master Sr
Registered: 08/23/04
Posts: 7730
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a Scuby is also a flat engine design which allows for a TMIC. Most other vehicles are inline or v's.. and they are too high for a TMIC so they use a FMIC.
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#670953 - 11/12/06 05:16 PM
Re: Explain the difference between FMIC and TMIC turbos
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tylerdurden
Post Master Supreme
Registered: 03/31/02
Posts: 25888
Loc: Shyea, like I'm telling you
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It's better to have the rad and IC not competing quite so directly for cold air. Top mounts and V-mounts coupled with a hood scoop/extractor hood are good for this. Track cars especially need this.
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#670956 - 11/12/06 09:51 PM
Re: Explain the difference between FMIC and TMIC turbos
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aerosaaber
Post Master Supreme
Registered: 06/29/02
Posts: 16004
Loc: Pittsfield, MA
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the mazdaspeed 6 is a top mount but it's air is fed from the front, so no need for a hood scoop.
_________________________
2006 Subaru WRX Wagon (I'm back on boost!) 2001 Subaru Legacy Outback Wagon Limited (sold) 1994 Saab 9000 Aero (gone) http://www.saabrally.com
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#670957 - 11/13/06 12:07 AM
Re: Explain the difference between FMIC and TMIC turbos
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DomesticPower
Post Master
Registered: 02/15/00
Posts: 2008
Loc: USA
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It's all about packaging and cost. Sometimes there's no room for a frontmount and the extra plumbing adds to costs. Putting the intercooler in the engine bay is retarded IMO. It will heatsoak no matter how well it's designed at low speeds. Front mount is the way to go with the intercooler getting priority over the radiator. The extra plumbing does not hurt performance at all.
One of the GN guys did a lot of research on the stock engine bay located intercooler vs no intercooler vs frontmount. It turns out that the stock location heated the air over no intercooler at low to moderate boost levels in stop and go traffic. This is even with the stock crank mounted intercooler fan and scoop/shroud system. Front mount/side mount are much more consistant and effective in real life situations.
_________________________
T-66 256" 84 GN- Toy
06 Acura TL- DD
87 Celica GTS- Beater
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#670959 - 11/13/06 02:27 AM
Re: Explain the difference between FMIC and TMIC turbos
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XT6Wagon
Moderator
Registered: 10/30/99
Posts: 7265
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TMIC on the subarus drasticly reduces the lenght and thus volume of the pipeing. Which makes for more HP, higher response, and lower wieght than a FMIC on the same car. Engine bay layouts other than the subarus would typicly see less of a benifit. The down side is there is a limited space for the intercooler, but given that the STi stock intercooler is good for well over 300whp in most climates.... Typical OEM screwups are too small of a intercooler (1st gen JDM WRX prime example), poor airflow (lol most), and shitty plumbing reducing advantages(lol most).
FMIC's typicly don't do well in OEM applications. Extra cost and wieght are only the obvious ones. meeting bumper laws adds extra wieght and length to the car. More over the extra wieght foward of the front axle hinders handling. Airflow despite "common sense" is a design issue and not in anyway automaticly better. More so since most are not ducted on the input side of the ambient air, and have plenty of obstruction on the output side with the condenser core and radiator.
Sidemounts are a typicly a mess, with tiny cores, and shitty piping. However they usualy are well separated from thermal sources in the engine bay, and have atleast passable ducting even in lower priced cars making them much more acceptable from a end user standpoint.
Edited by XT6Wagon (11/13/06 02:30 AM)
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#670963 - 11/13/06 02:49 PM
Re: Explain the difference between FMIC and TMIC turbos
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XT6Wagon
Moderator
Registered: 10/30/99
Posts: 7265
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Let me guess, when the TMIC heatsoaked in 2 dyno runs... the hood was open... and your fans sucked ass.
I've had plenty of sucess closing the hood, and using a nice powerful fan to put air into the scoop. After all most dyno pulls are simmulating a 3rd gear pull or so in the real world, so even this is under cooling the intercooler from a airflow standpoint, but possibly fairly accurate for most people since it has thermal mass that is starting out at a lower temp than if you started from a dead stop on the street
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[Email]11.893@112.13mph[/Email]
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#670965 - 11/13/06 03:08 PM
Re: Explain the difference between FMIC and TMIC turbos
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DomesticPower
Post Master
Registered: 02/15/00
Posts: 2008
Loc: USA
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The only thing I can imagine that would be worse than the GN's engine bay mounted IC would be the Suby's on top of the motor. In real world driving conditions like stop and go the intercooler is going to get heatsoaked very bad. If the intercooler turns into an interheater during low to moderate boost with the GN's cold air ducting and intercooler fan, I could only imagine what the Suby's is like.
With a frontmount, you're going to get better airflow than the best engine bay located coolers. Not to mention you're keeping it away from radiant heat and heatsoak is non-existant. And again I challenge anyone to show me where slightly longer plumbing causes power loss, lag, or lack of a response. I went from no intercooler with the turbo connected directly to the intake manifold to 16' of 3" plumbing and a huge intercooler with absolutely no difference in spool.
I've done a couple back to back runs with my frontmount and pulled over and felt the intercooler. It's hot on the intake side but pretty much ambient on the outlet side. That goes along with my charge temps that only rise 10-15 degrees over ambient during a run.
_________________________
T-66 256" 84 GN- Toy
06 Acura TL- DD
87 Celica GTS- Beater
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#670966 - 11/13/06 03:22 PM
Re: Explain the difference between FMIC and TMIC turbos
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CommonGutterTrash
This user is more useless than a half-baked compost pile.
Post Master Sr
Registered: 09/16/02
Posts: 6437
Loc: Boston MA
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'eh
any type of Intercooler sitting less than 2-feet from the turbo is not good. let-alone directly above it. I can't imagine having to have forward motion JUST to have ambient-temp air. I suppose, in the grand Scheme of things, your Everyday commuter doesn't matter.
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#670967 - 11/13/06 09:27 PM
Re: Explain the difference between FMIC and TMIC turbos
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B15Sentra
Post Master Sr
Registered: 09/25/01
Posts: 6366
Loc: Bay Area, CA
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Quote:
Well I am going to assume Suby didn't design the STI very well then...I remember when we were dyoning one, and after 2 pulls the thing was HOT to the touch...to the point of burning you...the hood was up as well...
Guy with 450whp Civic and dyno experience with 1 STi > Subaru.
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#670969 - 11/13/06 11:38 PM
Re: Explain the difference between FMIC and TMIC turbos
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aerosaaber
Post Master Supreme
Registered: 06/29/02
Posts: 16004
Loc: Pittsfield, MA
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I read somewhere that at speed air comes out of the suby hood scoop rather than going in.
Therefore the best option is front mount and reverse the hood scoop so air can get out easier.
_________________________
2006 Subaru WRX Wagon (I'm back on boost!) 2001 Subaru Legacy Outback Wagon Limited (sold) 1994 Saab 9000 Aero (gone) http://www.saabrally.com
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#670970 - 11/13/06 11:46 PM
Re: Explain the difference between FMIC and TMIC turbos
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XT6Wagon
Moderator
Registered: 10/30/99
Posts: 7265
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yah its strange then to do 350+ whp on the stock top mount. Hell I'm very sure I was doing well over 400hp on the stock top mount with the AVO500. Course it was <32 degrees the whole time I had boost that high on said AVO500.
you need proper airflow. a carpet dryer or two randomly aimed at the intercooler with no ducting is NOT going to get it done. I was using a 220v industrial fan just for the intercooler that pushes out air in the 50-60mph range which then hits the hood to diffuse it some before entering the hoodscoop.
More over would put money on the car he was screwing with had either just the "hat" part of the OEM heat shield or nothing, and a unwrapped aftermarket downpipe. Can't bitch too much when you remove all the heat shielding on the exhaust system nearest to the intercooler.
Last Impulsives point that a exit duct would be a good idea for the STi intercooler... is dead on. bitch to implement, not cheap, but would improve the intercooling to a measurable degree and reduce heatsoaking at stoplights. My only consern would be transmission cooling, as its likely that subaru counts on a even airflow from the intercooler across the transmission on its way under the car to cool the transmission under high loads. Certainly for the 6spd where the front and center diffs generate HUGE heat, and do not have the transmission cooler of the JDM model. Which reminds me, I should make a kit and sell it since the pump n shit is integrated into all the 6spds to spray lubricate different areas of the gearbox.
_________________________
White 04 Impreza with factory foglamp covers
[Email]11.893@112.13mph[/Email]
on Stock tires
http://www.ej255.net
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#670973 - 11/14/06 05:19 PM
Re: Explain the difference between FMIC and TMIC turbos
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XT6Wagon
Moderator
Registered: 10/30/99
Posts: 7265
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spool time on a well done conventional FMIC usualy doesn't affect minimum spool rpm that much. It does cut down on the response alot, and if going with a big turbo it can raise the min spool rpm alot since you have alot more "lag" between the compressor pushing a few extra CFM, and that showing up at the turbine to power said compressor to push even more CFM.
_________________________
White 04 Impreza with factory foglamp covers
[Email]11.893@112.13mph[/Email]
on Stock tires
http://www.ej255.net
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#670974 - 11/14/06 10:41 PM
Re: Explain the difference between FMIC and TMIC turbos
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normaspirated
Post Master Supreme
Registered: 11/04/99
Posts: 22154
Loc: Nevada
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My tmic on my wrx didn't have any heating issues when I was getting a pro tune 'cause the tuner would spray it with water after every run 
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#670975 - 11/14/06 10:52 PM
Re: Explain the difference between FMIC and TMIC turbos
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RyanTSI
Post Master Sr
Registered: 11/09/06
Posts: 3629
Loc: Canadia
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#670976 - 11/14/06 11:48 PM
Re: Explain the difference between FMIC and TMIC turbos
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Anonymous
Anonymous
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Moderator: auxilary, Professor Paki
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