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Old 05-18-2017, 04:14 PM   #1
joeb8888
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Default Engine cover with larger intercooler

What's everyone's thoughts on the engine cover? I installed a depo intercooler which is a lot larger than the stock intercooler. Like most other aftermarket intercoolers, the stock engine cover needs to be modified. Right now I'm running it without the cover because obviously stock it doesn't fit, and I think I read somewhere that someone did some testing and didn't notice a large difference between having the cover on or off. So is it worth it to modify the stock engine cover or just leave it off.
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Old 05-18-2017, 04:22 PM   #2
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i leave it off, good luck convincing me it makes a lick of a difference.
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Old 05-18-2017, 04:43 PM   #3
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Quote:
Originally Posted by joeb8888 View Post
What's everyone's thoughts on the engine cover? I installed a depo intercooler which is a lot larger than the stock intercooler. Like most other aftermarket intercoolers, the stock engine cover needs to be modified. Right now I'm running it without the cover because obviously stock it doesn't fit, and I think I read somewhere that someone did some testing and didn't notice a large difference between having the cover on or off. So is it worth it to modify the stock engine cover or just leave it off.
I didn't notice much of a difference at all with the factory engine cover off or on. Ideally you want an aftermarket splitter that helps direct more air but no one currently makes one.
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Old 05-18-2017, 05:13 PM   #4
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I figured as much. I know grimmspeed makes a nice intercooler with splitter. The cost of that setup though is more than I want to spend on this car currently.
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Old 05-18-2017, 05:33 PM   #5
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Originally Posted by mishapopa View Post
i leave it off, good luck convincing me it makes a lick of a difference.
Gimmspeed has data on the difference between shroud and no shroud.
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Old 05-18-2017, 05:46 PM   #6
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Originally Posted by Boggie1688 View Post
Gimmspeed has data on the difference between shroud and no shroud.
to my understanding we're talking about the OEM engine cover, which is pure aesthetics. grimmspeed has proper sealed ducting solution to ensure most of the air is directed towards the intercooler.
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Old 05-18-2017, 06:45 PM   #7
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Engine covers make a world of difference!
So much wasted air is going past the fins if you don't have shroud sealed properly there for efficiency is lost. Air flowing through the scoop is going right over the intercooler and not through it.

Subaru in no way only made the cover just for looks...

Last edited by PERRIN_Thomas; 05-18-2017 at 07:24 PM.
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Old 05-18-2017, 07:10 PM   #8
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Originally Posted by mishapopa View Post
to my understanding we're talking about the OEM engine cover, which is pure aesthetics. grimmspeed has proper sealed ducting solution to ensure most of the air is directed towards the intercooler.
It not pure aesthetics. The oem unit seals as well.

Grimmspeed echoed what the factory did because testing proved it was a proper implementation. They had to redesign the ducting because of the change in the intercooler size/placement.
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Old 05-18-2017, 08:11 PM   #9
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Ok, I will try to get it back on for summer. I notice absolutely nothing when ambients were <15C. Same delta T consistently. These things are designed for the higher temps tho...
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Old 05-18-2017, 09:39 PM   #10
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I'm speculating:

Don't just look at the delta T after a given pull, or max t. You also need to look at the time it take for the intercooler temps to drop. The heat capacity of the air is the same at a given temperature and car speed, so either you boost intercooler efficiency or you increase air flow. The shroud helps maximize flow over the fins.
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Old 05-18-2017, 11:27 PM   #11
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Originally Posted by PERRIN_Thomas View Post
Engine covers make a world of difference!
So much wasted air is going past the fins if you don't have shroud sealed properly there for efficiency is lost. Air flowing through the scoop is going right over the intercooler and not through it.

Subaru in no way only made the cover just for looks...
This actually makes sense. Going to look into option to seal it with either the stock cover or some garage weatherstripping.
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Old 05-19-2017, 08:55 AM   #12
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Originally Posted by mishapopa View Post
Ok, I will try to get it back on for summer. I notice absolutely nothing when ambients were <15C. Same delta T consistently. These things are designed for the higher temps tho...
On the stock IC? Should help in the summer but its really only going to help at like 50+MPH.

Quote:
Originally Posted by Boggie1688 View Post
I'm speculating:

Don't just look at the delta T after a given pull, or max t. You also need to look at the time it take for the intercooler temps to drop. The heat capacity of the air is the same at a given temperature and car speed, so either you boost intercooler efficiency or you increase air flow. The shroud helps maximize flow over the fins.
Delta T/Max T for short pulls like a 3rd gear rip will show you some combination of thermal inertia and cooling ability. The dT/dt after the pull will show you cooling ability on its own.

Quote:
Originally Posted by joeb8888 View Post
This actually makes sense. Going to look into option to seal it with either the stock cover or some garage weatherstripping.
For the larger aftermarket units, people are trimming the stock covers to fit. I think Killer B has an instruction that shows how they recommend it for their IC, which should help.
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Old 05-19-2017, 09:53 AM   #13
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The stock engine cover is definitely functional and should be used. An intercooler without some sort of guard is losing performance due to it. The only issue I see with the stock system is not the engine cover but the hood scoop. If you look at the hood scoop there is a vent that bypasses the intercooler "funnel". The grimmspeed unit directs all the air entering the hood scoop to flow towards the intercooler. Yes the grimmspeed unit is more expensive but there is a reason for it.
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Old 05-19-2017, 10:08 AM   #14
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Originally Posted by playslikepage71 View Post
On the stock IC? Should help in the summer but its really only going to help at like 50+MPH.
Well that's the thing, I no longer have the stock IC and the engine cover doesn't fit. One of my monitors are intake temp and manifold temp and the different is better than stock (in warm weather) and consistent. Obviously it heatsoaks if I'm in traffic.

It's definitely doing its job but could use better ducting for sure.
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Old 05-19-2017, 12:40 PM   #15
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Quote:
Originally Posted by mishapopa View Post
Well that's the thing, I no longer have the stock IC and the engine cover doesn't fit. One of my monitors are intake temp and manifold temp and the different is better than stock (in warm weather) and consistent. Obviously it heatsoaks if I'm in traffic.

It's definitely doing its job but could use better ducting for sure.
Best you can do is trim it to fit. A dedicated ducting solution a la Grimmspeed is best, if not difficult. The other dudes point about the bottom of the scoop is exactly right. There's a bunch of air that bypasses the stock IC.
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Old 05-19-2017, 01:59 PM   #16
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Originally Posted by playslikepage71 View Post
Best you can do is trim it to fit. A dedicated ducting solution a la Grimmspeed is best, if not difficult. The other dudes point about the bottom of the scoop is exactly right. There's a bunch of air that bypasses the stock IC.
Looks like I'd have to trim the bottom of the cover as I have the MAP intercooler which is huge and heavy. I wonder what Grimmspeed's intercooler dimensions are and if they sell their duct seperately because I wouldn't mind putting that on. I don't like the OEM engine cover... at all.
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Old 05-19-2017, 02:09 PM   #17
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Looks like I'd have to trim the bottom of the cover as I have the MAP intercooler which is huge and heavy. I wonder what Grimmspeed's intercooler dimensions are and if they sell their duct seperately because I wouldn't mind putting that on. I don't like the OEM engine cover... at all.
I'm pretty sure they have a chunk that screws to the hood and IC so idk if it will work
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Old 05-19-2017, 06:08 PM   #18
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Similar to what killer b reccomends helps the stock engine cover fit. I removed the rear rib on the underside of the cover in the back. I tucked the "teeth" in front of the intercooler and pushed the front plugs into their spots. It kinda squeezed the cover over the intercooler. There is still some gaps on the side, but not nearly as bad as not having it. Some foam will seal the sides and make everything better.
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Old 05-19-2017, 06:12 PM   #19
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Quote:
Originally Posted by mishapopa View Post
Looks like I'd have to trim the bottom of the cover as I have the MAP intercooler which is huge and heavy. I wonder what Grimmspeed's intercooler dimensions are and if they sell their duct seperately because I wouldn't mind putting that on. I don't like the OEM engine cover... at all.
We don't sell it separately because it won't install on any other intercooler but our own. We have the mounting portion of our intercooler cast into the end tanks. Without that, the splitter will do you no good.

It is pretty ridiculous that these other intercoolers still rely on using the engine cover for the ducting. It's a lazy cost saving measure that certainly does not help performance, and makes the enthusiast have to experiment with getting the stock engine cover to fit without sacrificing the seal (it's not easy at all to get it right).

And the other thing that very few realize is that even if you are able to get the stock engine cover ducting to work, because these aftermarket TMICs are taller (either to the firewall or the intake manifold, or both) the stock ducting can not direct flow through the entire core. That is why our splitter is 2 pieces. Because we've increased the size of the core we needed a larger area duct, and it isn't possible to bolt a single piece splitter to the hood that covers the entire core without it crashing into the cowl when you close the hood. So if you're awesome and got a really good seal on your intercooler using the stock engine cover, chances are it's blocking flow from at least some of the core.

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Old 05-21-2017, 03:31 PM   #20
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Re: air purposely being directed around the intercooler core.

Subaru is clearly doing this for a reason. Blowing air through there is being done to help develop flow through the engine bay and out under with the car.
This is a bit counter intuitive but clearly Subaru did the research and development.

Proof being a guy I know had a FMIC on his GV and like in the GD added a block off plate to the scoop. Once he was tracking he ran into overheating issues. On a hunch because that was all he changed since the last event he pulled the block off plate off and his overheating problems went away.
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Old 05-21-2017, 07:42 PM   #21
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I think grimmspeed isn't talking about totally blocking off air flow into the engine bay, but directing most of it through the intercooler instead of directing it at the intercooler. Without the intercooler essentially sealed to the hood scoop air is directed at it and able to flow over it instead of pushed through it. I think that there does need to be air pushed through the engine bay directing air also down and out of the bottom drawing heat out of the engine bay. But also air pushed through the intercooler is also air being pushed through the engine bay except it is wicking heat off the intercooler.
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Old 05-21-2017, 08:15 PM   #22
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Originally Posted by joeb8888 View Post
I think grimmspeed isn't talking about totally blocking off air flow into the engine bay, but directing most of it through the intercooler instead of directing it at the intercooler. Without the intercooler essentially sealed to the hood scoop air is directed at it and able to flow over it instead of pushed through it. I think that there does need to be air pushed through the engine bay directing air also down and out of the bottom drawing heat out of the engine bay. But also air pushed through the intercooler is also air being pushed through the engine bay except it is wicking heat off the intercooler.
True and I wasn't debating that in the least bit
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Old 05-21-2017, 08:55 PM   #23
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True and I wasn't debating that in the least bit
I know, we must think alike. Must be the galaxy blue pearl. Lol
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Old 05-21-2017, 10:09 PM   #24
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Subaru has engineers devoted to designing, engineering, testing, and verifying function of components like this. In their toolbox they have and extensive knowledgebase going back over 25 year, use simulation software that aftermarket companies can only dream of, have access to wind tunnel testing, and then there's real world testing to again, verify. This all takes years of time from inception to final production design.

Aftermarket companies can spin however they want, to justify their actions or inactions in regards to shrouding the TMIC. We designed our TMIC with the intent of using the OEM components for the above reasons. There was no point in developing and adding costs when our core and end tanks are already at the apex of what money can buy. It seemed pointless in adding unnecessary costs when the OEM components performed well.
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Old 05-22-2017, 09:36 AM   #25
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Quote:
Originally Posted by KillerBMotorsport View Post
Subaru has engineers devoted to designing, engineering, testing, and verifying function of components like this. In their toolbox they have and extensive knowledgebase going back over 25 year, use simulation software that aftermarket companies can only dream of, have access to wind tunnel testing, and then there's real world testing to again, verify. This all takes years of time from inception to final production design.

Aftermarket companies can spin however they want, to justify their actions or inactions in regards to shrouding the TMIC. We designed our TMIC with the intent of using the OEM components for the above reasons. There was no point in developing and adding costs when our core and end tanks are already at the apex of what money can buy. It seemed pointless in adding unnecessary costs when the OEM components performed well.
Seems like CFD is a pretty accessible technology these days. Larger aftermarket companies can afford stuff like STAR-CCM+ or Ansys. Even Solidworks flow simulation does a decent job for simple stuff and that license is pretty cheap. I know a lot of you have laser point cloud scanners to get the OEM geometry with more than enough accuracy for CFD. To act like your decision wasn't more of a business decision seems disingenuous to me. Doing real world testing on an intercooler is cheap and easy. Even a DIY person could rig something up to test shroud/sealing designs. We've already got half the sensors installed from the factory.
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