AWIC and the coupe question

[scott s]

I must say upfront that since I live in Florida that I am leaning more towards an 818s build. I could live with just an electric heater/defroster in that and no AC. I also firmly believe that the VCP AWIC is a must on this car, as a high horsepower street car. There is a chance I may go with the coupe as it is so darn sexy and then have to deal with heating and ac but what to do with the 2 hoses from the roof inner liner. Just plumb then to the engine bay for extra air into the engine bay or could they fitted to the awic on top of the engine for extra cooling? I probably should be directing this to Wayne but hope fully he will see it. I know ffr is working on venting air in from the side ducts and all but still think the awic is the answer.

[Mechie3]

Blowing the air onto the AWIC won't do much for you. The surface area of the outside compared to the surface area of the fins inside plus the thickness of the outside plate means you won't get much heat transfer. You could do a few things:

1: Duct air to an intake
2: duct air to the engine bay in general
3: Plug the intake scoop
4: Cut out the interior channels and and make a new vent that can open and close on the inside to allow fresh air into the cabin like the WRC cars did with the roof scoop.

[STiPWRD]

what to do with the 2 hoses from the roof inner liner. Just plumb then to the engine bay for extra air into the engine bay or could they fitted to the awic on top of the engine for extra cooling?
You can direct the roof scoop hoses into the engine bay, driver cabin, or just block of the roof scoop altogether. None of this will affect the AWIC since it is directly liquid cooled. The heat absorbed by the AWIC water is cooled by the heat exchanger in the front of the car. Blowing cooler ambient air from the roof scoop over the AWIC core will have a negligible effect.

BTW, I agree that the AWIC is the best option for cooling the air down. Although there may be a way to make an A2A intercooler work with the coupe roof scoop.

[scott s]

Well I am still a way's off on my build. The idea of venting air to the cabin sounds like a good idea. Like factory air on old cars. Would almost negate the need for ac except possibly in Florida where I live. Ya if ffr can get the scoop and hoses to effectively work on an A2A intercooler it sure would simplify the build. I will say up front that if the 818s had roll up glass and a convertible top that the windows would seal to I would most definitely go the 818s here in Florida.
Ducting the air to a box around the cobb intake would be effective if there is room for a large enough airbox? Just trying to get ideas and research everything I can ahead of the build!

[bbjones121]

Well I am still a way's off on my build. The idea of venting air to the cabin sounds like a good idea. Like factory air on old cars. Would almost negate the need for ac except possibly in Florida where I live. Ya if ffr can get the scoop and hoses to effectively work on an A2A intercooler it sure would simplify the build. I will say up front that if the 818s had roll up glass and a convertible top that the windows would seal to I would most definitely go the 818s here in Florida.
Ducting the air to a box around the cobb intake would be effective if there is room for a large enough airbox? Just trying to get ideas and research everything I can ahead of the build!

Almost had what you are looking for, I was hoping for the same thing, but Dave mentioned before that the rollup windows on the coupe will not match up with their softtop...unfortunately.

[scott s]

Almost had what you are looking for, I was hoping for the same thing, but Dave mentioned before that the rollup windows on the coupe will not match up with their softtop...unfortunately.

I think FFR should really consider a redesign of the soft top and frame so it will work with the coupe windows if possible or a new frame that will seal with different side glass if the coupe windows are just to tall?
I think it would increase 818s sales now that the coupe is available. I am a semi retired auto interior, convertible top and marine canvas and upholstery guy and have done many antique cars with soft tops and snap or zip in windows and they are just to leaky if caught in a downpour and way to drafty for my likes. Particuarly on cold days. Now that the coupe is available this is why I am leaning more towards it every day!

[Flamshackle]

I also firmly believe that the VCP AWIC is a must on this car, as a high horsepower street car.

I have not gotten my hands on the coupe yet but I would tend from an engineering stand point to disagree on this statement.

I have done a lot of building and development of my own intercoolers for subarus over the years and have found the top mounted intercoolers to be very effective contrary to popular opinions. I have tested many different setups and through thermocouple and manometer inputs found the vast majority of front mounted intercoolers to not be an effective 'upgrade' for the production Subaru. A better flowing top mount is a very effective upgrade with supporting modifications however.

The only issues I see here in the 818 application are to do with the volume and pressure that the roof scoop is able to grab and direct to the std core position.

This is impacted most directly by the pressure under the std cooler (engine bay) and volume of air passing through.

Heat in the rear of the coupe is also a potential issue but as a weight and heat solve I intend to go this route...
47434

If the roof scoop is not able flowing enough air then it could easily be modified to catch a little more with a little fiberglass work without making it too agricultural looking.

So YES the std intercooler needs upgrading for high horse power applications. But the position does NOT necessitate the use of a water to air cooler if supporting modifications are made regarding heat isolation, air flow volume and engine bay air pressure. It can be easily tested and developed to function well at home with a cheap manometer.


The VCP core is obviously an excellent performing option for the 818 but the advantage of simplicity, weight and track performance IMO goes to the well ducted, aftermarket air to air core in std location. Which I believe is not going to be difficult to achieve.

my 10c

[bbjones121]

I have not gotten my hands on the coupe yet but I would tend from an engineering stand point to disagree on this statement.

I have done a lot of building and development of my own intercoolers for subarus over the years and have found the top mounted intercoolers to be very effective contrary to popular opinions. I have tested many different setups and through thermocouple and manometer inputs found the vast majority of front mounted intercoolers to not be an effective 'upgrade' for the production Subaru. A better flowing top mount is a very effective upgrade with supporting modifications however.

The only issues I see here in the 818 application are to do with the volume and pressure that the roof scoop is able to grab and direct to the std core position.

This is impacted most directly by the pressure under the std cooler (engine bay) and volume of air passing through.

Heat in the rear of the coupe is also a potential issue but as a weight and heat solve I intend to go this route...
47434

If the roof scoop is not able flowing enough air then it could easily be modified to catch a little more with a little fiberglass work without making it too agricultural looking.

So YES the std intercooler needs upgrading for high horse power applications. But the position does NOT necessitate the use of a water to air cooler if supporting modifications are made regarding heat isolation, air flow volume and engine bay air pressure. It can be easily tested and developed to function well at home with a cheap manometer.


The VCP core is obviously an excellent performing option for the 818 but the advantage of simplicity, weight and track performance IMO goes to the well ducted, aftermarket air to air core in std location. Which I believe is not going to be difficult to achieve.

my 10c

I am having hard time getting an aftermarket aaic below the rear deck lid. I will cut and reweld the stock mount arms to hold it a bit lower and see if that works. I plan on trying to keep stock location airtoair. I was going to build a nice shroud for ducting air through and out of it. Aluminum to start, eventually building one out of carbon fiber.

[Pearldrummer7]

I am having hard time getting an aftermarket aaic below the rear deck lid. I will cut and reweld the stock mount arms to hold it a bit lower and see if that works. I plan on trying to keep stock location airtoair. I was going to build a nice shroud for ducting air through and out of it. Aluminum to start, eventually building one out of carbon fiber.

Agreed. I can't fit my deck lid with my ~06 STi TMIC. I'm really not sure what to do about it, so I ran some track events without the deck lid. As for the future.... maybe some side intercoolers like Dan (RM1SPX or whatever his name is)

[scott s]

I don't think a top mounted a2a intercooler will have a fitment problem with the coupe. For simplicity I WANT to see it work on a high output motor with the hoses from the roof scoop!

[dukegrad98]

If the roof scoop is not able flowing enough air then it could easily be modified to catch a little more with a little fiberglass work without making it too agricultural looking...

I'm no engineer, but this reminds me of a hot debate about the FF Roadster (Cobra) and air flow through the hood scoop, on the other forum a number of years ago. That thread was more in relation to engine intake and a "ram air" effect than anything related to intercoolers. It was a pretty hotly contested discussion. Lots of talk about boundary layers and so forth. If memory serves, more than a few people were shocked to see a video showing that rather than "ram air" into the scoop / intake, one car was actually flowing air back OUT of the hood scoop!

Cheers, John

[Mechie3]

The limiting factor on the coupe roof scoop might be the channels it runs through and not the scoop itself. The length is longer than an exige S and the path has several turns. The factory exige S uses a large scoop that travels straight. The 2 eleven uses top side scoops (not unlike the 818 in visual appearance, though flow over the body is likely different) but uses two 4" ducts that goes to a plenum (like i've suggested before is the ideal A2A ducting method). I didn't see this diagram until tonight (factory 2 eleven setup):

http://www.lotustalk.com/forums/attachment.php?attachmentid=548921&stc=1&d=1431327453

[bbjones121]

The limiting factor on the coupe roof scoop might be the channels it runs through and not the scoop itself. The length is longer than an exige S and the path has several turns. The factory exige S uses a large scoop that travels straight. The 2 eleven uses top side scoops (not unlike the 818 in visual appearance, though flow over the body is likely different) but uses two 4" ducts that goes to a plenum (like i've suggested before is the ideal A2A ducting method). I didn't see this diagram until tonight (factory 2 eleven setup):

http://www.lotustalk.com/forums/attachment.php?attachmentid=548921&stc=1&d=1431327453

Nice find. That would be perfect, but that is a 1.8l that you can't really push like a Subaru 2.5l. I wonder if it is enough.

[Flamshackle]

The limiting factor on the coupe roof scoop might be the channels it runs through and not the scoop itself. The length is longer than an exige S and the path has several turns. The factory exige S uses a large scoop that travels straight. The 2 eleven uses top side scoops (not unlike the 818 in visual appearance, though flow over the body is likely different) but uses two 4" ducts that goes to a plenum (like i've suggested before is the ideal A2A ducting method). I didn't see this diagram until tonight (factory 2 eleven setup):

http://www.lotustalk.com/forums/attachment.php?attachmentid=548921&stc=1&d=1431327453

I prefer this option if the rear quarters flow enough air. I didn't actually notice that the rear quarter glass had an intake until last night. You could test how effective the different scoops are easily enough by driving with a smoke wand and a co conspirator.

The roof scoops air path through the cabin is worryingly convoluted. FFR may wind tunnel test this and have a intercooler solution in future. If not then personal development isn't that hard really.

[Mechie3]

From a performance standpoint it makes more sense to have the tunnel for the IC come straight back. FFR routed it to the side for rear visibility (a complaint on the exige S).

[Flamshackle]

From a performance standpoint it makes more sense to have the tunnel for the IC come straight back. FFR routed it to the side for rear visibility (a complaint on the exige S).

The big potential setback with side intakes is uneven air pressures from cross winds and cornering creating back flow issues from side to side.

[redfogo]

Why not a side mount intercooler with spal puller fan pulling fresh air from the outside vent? I used the smaller core tell I was into the 400hp then I went to a trunk mount configuration in my mr2.

I know in the mr2 world http://racerxfabrication.com/mr2-celica/intercooler/large-core-side-mount this is the new cool intercooler set up. Its a larger side mount core. I would imagine you could buy just core if you asked and let them know your plans with it.

I imagine an intercooler set up like this would be pretty good if we could fit it. Not sure I don't have a car tell Sunday.

[Mechie3]

People have tried fans and they just didn't flow enough. Dan (RM1Sepex) has done a side mount but hasn't had it running yet to test.

[bbjones121]

I will be ducting from the side vents, deck lid vents, and have been considering a way to force air into the channels below the doors from the front of the car. Each will have its own inlet to an intercooler shroud and I will have some sort of soft close check valves so no channel can have backflow. The coupe top vent will be solely for cooling engine bay. I hope to have it easily switchable from hard top to convertible without drastically changing air flow through intercooler. For convertible engine cooling, I am hoping mechies hump vents are adequate.

[bbjones121]

I have also been looking at narrow scoops to put in sides to pull air into that underdoor channel as well.

[redfogo]

I have also been looking at narrow scoops to put in sides to pull air into that underdoor channel as well.
I think the big thing here is using a good puller fan to pull in the fresh air. Just using an intercooler with no fans seems pointless if you have the room for a fan. Fan should always be pulling as its more efficient to pull air through the intercooler then try to blow air through.

[bbjones121]

I think the big thing here is using a good puller fan to pull in the fresh air. Just using an intercooler with no fans seems pointless if you have the room for a fan. Fan should always be pulling as its more efficient to pull air through the intercooler then try to blow air through.

Definitely, I agree. Plus the little heat the blower puts out, you would rather that hear go out of car rather than through intercooler. I plan to shroud the back end of the intercooler as best I can. The trunk deck lid will be my intercooler exit. It will be shrouded so that when the trunk lid is shut, it seals up to the intercooler exit shroud. Hopefully I can get two small fans in the shroud area.

[scott s]

I am wondering if all these possible solutions wont cost almost as much, not including the time involved as the top mounted awic. Seems like it really is not a simpler solution. That is unless ffr gets the roof scoop and 2 hoses to work for us as a air to air top mount on the coupe, that will definitely need ac for the cabin in my humble opinion. Personally if I opt for the convertible I am not going to mess around and just go air to water. I even think air to water on the coupe using the roof scoop for fresh air into the cabin ( still needing ac!) and all the rear vents for engine bay cooling may be the final answer for me. I have time yet so waiting impatiently LOL!

[bbjones121]

I actually am not too concerned with the work. I am actually wanting to go air to air so I don't have three hear exchangers stacked in front of my car.

[Flamshackle]

I actually am not too concerned with the work. I am actually wanting to go air to air so I don't have three hear exchangers stacked in front of my car.



This is me also. It's not that much work costs if your fabricating it yourself.

[bbjones121]

This is me also. It's not that much work costs if your fabricating it yourself.

Yup exactly.

[lennyspecv]

I have been absorbing information about this charged air cooling issue and risk for detonation using the stock ECU. Since this is well documented, why has FFR not come up with a solution for it? There has got to be a way to mount the intercooler in a different spot, or create more ducting/venting to direct air flow through the engine bay and specifically to the intercooler.

[Hindsight]

To keep kit price low and build simplicity up, it made sense for FFR to keep the stock IC location. For a bone stock WRX on the street, it's probably ok. Anything above that and you have to get creative. Just part of modifying anything.

So it seems based on FFR's tests, they are focusing on solutions for the R which gets pushed harder longer. They are developing solutions and have posted about it here.

[lennyspecv]

To keep kit price low and build simplicity up, it made sense for FFR to keep the stock IC location. For a bone stock WRX on the street, it's probably ok. Anything above that and you have to get creative. Just part of modifying anything.

So it seems based on FFR's tests, they are focusing on solutions for the R which gets pushed harder longer. They are developing solutions and have posted about it here.

I see. Well, if it works for the R then it should be fine for street cooling. Do you happen to know where that thread was posted?

[Mechie3]

They're using an AWIC on the R.

[lennyspecv]

They're using an AWIC on the R.

So it sounds like the majority of owners are going with an AWIC?

It's a big added expense for the project, but I guess when it comes to keeping your motor from blowing up you do what you gotta do.

[bbjones121]

They're using an AWIC on the R.

I believe the last R actually was air to air?

Yup, it was. The last windtunnel tested R had AtoA.

http://thefactoryfiveforum.com/showthread.php?19100-New-818-Configurations-Windtunnel-Tested.

[Mechie3]

Edit: found answer to my own question. They tried the aaic but haven't gotten temps where they want them but found awic slowly increased temp.

[bbjones121]

Edit: found answer to my own question. They tried the aaic but haven't gotten temps where they want them but found awic slowly increased temp.

Yup. who even knows what they are working on now with intercoolers...