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Underhood Temps with bigger turbo and N/A hood


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Just wondering if anyone actually has data backing up how important the hood scoop really is. I think i'm 1 in a million, but the hood scoop actually bothers me and considering I am FMIC I have thought abt going to a N/A OBP hood.

 

Being that I no longer have a stock turbo, will cooling be affected that much? It's not a big turbo, just a Ball Bearing 18G. Keep in mind there is no TMIC or engine cover, so is heat still a big issue? I understand the hood scoop is somewhat effective in delivering fresh air to the TMIC, so it is prob keeping under hood temps down a bit, but I'm wondering if the upgraded turbo will require the hood scoop for ample air delivery.

 

I understand everyone has opinions, and while I'm open to them i'd like to see if anyone has actually gone as far as testing under hood operating temps with and without the hood scoop. I don't even mind if the data is on VF40, i'd still like to see some actual figures.

 

Lastly, the car gets driven very rarely now, only on weekends if that (she's been down since early may) so it will be sparingly driven, but I do drive pretty hard.

 

Please move to correct area if it is not, not sure where this would go under exactly.

 

Thanks in advance.

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Depends on wrap/shields. Amount of traffic etc... Lots of factors contribute to underwood temps. I too was considering this move but after a good sit in traffic and opening my hood after, I like that the scoop allows some hot air to escape at a stand still. I'd like to get a chimney like the forester guys have to plumb the scoop directly to the turbo-
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You probably want a vent instead, reverse your hood scoop, but then testing air pressure at the rear of it would be a good idea cos there might be a high pressure area at the base of the windscreen. Otherwise block it or go NA hood and check temps yourself with a cheap temp sensor or gun.

 

The scoop could be creating positive pressure in the engine bay which is not what you want with a FMIC, you want to draw air through it. My brother has a turbo Swift and was having overheating issues, he blocked his vented carbon hood and it actually helped a bit.

 

Airflow is all very complicated and what's best is often counter-intuitive.

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Cowl induction?

 

Cowl induction is an air intake for fresh air at the back of the hood and doing that would be worse than the stock hood scoop. In the 3000GT community someone made some really nice cowl induction hoods which did lower under hood temps when stationary but logging showed that coolant temps were higher. Those with FMIC had over heating issues. The reason was that at speed the cowl induction stalled the air under the hood creating a high pressure area under the hood.

 

Once you go FMIC air flow management becomes top priority. Anything that would create a high pressure area under the hood is a bad idea you want the air to enter at the FMIC, flow into the radiator, and out the engine bay from the bottom or out the hood with proper venting (yes proper louvers would actually work for this).

2003 Baja 5MT

2016 Outback 2.5i Premium w/Eyesight

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I run a blow through set up, the maf(and IAT sensor) are located on the driver's side by the FPR. I could test this by blocking off the hood scoop and taking the IAT. If blocking off the scoop creates a vacuum, it would theoretically pull (more) air through the fmic and radiator. I don't have an underpanel though so I'm not sure how that would affect the outcome. Honestly, I think the FMIC is just blocking the radiator ton. I've thought of hacking up my front bumper and making ducting to force air through but it wouldn't look very pretty :lol:
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I'm too tired to go find the thread but if you are willing to search IWSTI... Cobb, a while back, discovered that they could lower temps by blocking off the hood scoop (they ran a FMIC).

All they did was to cover it with a piece of cardboard then they took it out again. Engine temps came down (forget how much) but not sure if engine bay temps were measured.

Bottom line is if you're running a front mount it does help but I believe it wasn't all that much. If you run yours on track and are fighting heat issues then I'd suggest trying it. I've always thought an NA hood with ducts from a 2.5RS would be ideal.

[URL="http://legacygt.com/forums/vbpicgallery.php?do=view&g=1586"VbGallery/URL]
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I run a blow through set up, the maf(and IAT sensor) are located on the driver's side by the FPR. I could test this by blocking off the hood scoop and taking the IAT. If blocking off the scoop creates a vacuum, it would theoretically pull (more) air through the fmic and radiator. I don't have an underpanel though so I'm not sure how that would affect the outcome. Honestly, I think the FMIC is just blocking the radiator ton. I've thought of hacking up my front bumper and making ducting to force air through but it wouldn't look very pretty :lol:

 

My thoughts exactly. I do not have an under panel either. I'm just running a regular short ram though, no blow-thru or speed density here. I read somewhere that the air the hood scoop was drawing in was flowing over the tmic, down past the turbo and out behind the engine tray. Im guessing by removing the undertray and tmic the hood scoop is doing nothing but venting the air at standstill and creating turbulence at speed.

 

I also heard someone used an NA outback hood in place of the GT hood when they went FMIC. Does anyone know who this was or where I can find a thread pertaining to this? I searched this forum and google and could not find anything. I know people have Macgyver'd oil/tranny coolers where the TMIC used to sit, but I don't know if that makes sense either.

 

Since the car is down for a bit I am planning on cutting out the center bar that is blocking the FMIC on the front bumper. I found this thread when searching around http://legacygt.com/forums/showthread.php/fmic-bumper-cutting-extremely-89894.html?t=89894

and I think I have a good way to reinforce it. I will have a friend fiberglass over the U on the bottom that was cut out and reinforce the top and bottom from sagging in the middle with 1" thick and 2' long steel strapping strips placed on the inside of the bumper. At least i hope that will prevent it from sagging on the top and cracking by the newly applied fiberglass. What do you think?

 

I'll probably just keep it as is, especially with the weather we have been having so far. Just sitting in traffic would probably bring temps up a good bit without the scoop to vent the heat out.

 

Thanks for everyones .02 on this.

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Capestylez had the outback hood with Perrin fmic. That car is long gone. I personally didn't really like the look, I'd rather have just a 2.5i hood. But to each their own-

 

I agree I like the look of a 2.5i hood better but im worried about clearance with the way the piping is run with this sti turbo and the OB or 3.0r hoods look a little taller in that respect.

 

I am going to look up that user ID and see if I can't go through some of his old threads and see his general feelings about the whole switchover.

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Subscribed.

 

Someone else on NASIOC also mentioned blocking the hood scoop to lower the air pressure in the engine bay, to more air through the radiator, to keep coolant temps down. Might have been Phil from Element Tuning, but I'm not sure of that.

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Haven't had a chance to search much, but I did stumble across this when looking into buying a KS Tech intake that will fit wit the new front mount.

http://www.kstech.biz/servlet/the-WRX-fdsh-STI-Hood-Vent-%26-Scoop-Delete/Categories

I reached out to them on Tuesday but have't a gotten a response from them yet. I will be glad to post up their response once I receive it.

Does anyone know how hard it would be to modify one? More importantly, with strictly the vent what would happen to the various components under the hood over time? Wouldn't things be more open to the elements possibly cause issues? my biggest fear is hydrolock. Even though the vent and intake are in 2 totally separate spots, what is preventing the elements from getting to your motor? Is this just a chance you take? This really isn't a soap on the intercooler question, but a rather serious one now that the TMIC is no longer in place.

 

Thanks

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Our hood scoop is integrated into the hood. On those WRXs the hood scoop is attached to a hole in the hood. If you are FMIC and looking for better air flow management under the hood the most simple thing to do would be to just swap with an NA hood. It will take some serious body work to make any changes to the LGT hood scoop and it's just not worth it IMO.

2003 Baja 5MT

2016 Outback 2.5i Premium w/Eyesight

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I finally have 2 days in a row off so I'm planning on running to lowes and fabbing a scoop delete. Unfortunately, it decided to rain in texas(weather is so erratic here) so measuring IAT differences may have to wait until its blistering hot again. Typically I had ambient +20* or so so it may or may not show a difference.
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I'm no expert but it seems to me that blocking off the hood scoop is the way to go. You would also keep the under engine tray so that as the fans kick on they will push the air through the engine bay and out under the car.

 

If you have the hood scoop open that wouls allow air to escape and not help create the proper pressure under the hood and out the bottom.

 

Has anyone added a manual fan under the hood scoop?

 

 

I seem to recall that thread...

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

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I finally have 2 days in a row off so I'm planning on running to lowes and fabbing a scoop delete. Unfortunately, it decided to rain in texas(weather is so erratic here) so measuring IAT differences may have to wait until its blistering hot again. Typically I had ambient +20* or so so it may or may not show a difference.

 

Thanks a bunch. Do you have an undertray? I'm wondering if that extra fan would be necessary to direct air out towards the back. Naturally when the car is moving I would assume the air is directed that way, but the extra fan may be necessary to remove hot air when standing still.

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