818C Intercooler Plenum

[AZPete]

At the Barrett-Jackson Auction I spoke with Jim Schenck about the AAIC in my 818C. He said FFR had made ducts for the side vents that he would send to me if I would install and give feedback. He did, and I did. I made a plenum (air box) that directs air from the 2 roof ducts and 2 side vent ducts to the stock WRX intercooler. My plenum has 2 SPAL fans inside, on a switch, to push air when in traffic, and I mounted an Intake Air Temp (IAT) gauge on the front of the plenum that I can see in the rear view mirror:
Plenum installed.jpg
On the inside, I made walls to separate the air sources so they would not compete:
Plenum internals.jpg
And, the IAT gauge shows the hot pre-IC temp and the cool post-IC temp.
IAT gauge.JPG

I drove 850 miles round-trip to Huntington Beach last week and ambient temps were up to 90 degrees through Palm Springs, but the post-IC temps stayed under 100. Today, at home, the ambient temp was 72 and I tromped on it to get the pre-IC temp up to 180 degrees. The post-IC temp went up to 120 then quickly dropped to 95, so I think it's working.

[AZPete]

The ducts for the side vents are fiberglass and fit on the inside. I bonded threaded studs to the inside of the body near the side vents to hold the ducts in place. Of course, the pieces were intentionally too big so I trimmed them and painted the outside so they might look like aluminum from the outside:
Left duct prepped.JPGside vent outside.JPG
Here's the left-side duct installed, and then with a flex tube attached. This tube goes to the left end of the plenum.
Left duct installed.JPGleft duct with tube.JPG

To see the air flow from the flex tubes, I disconnected them from the plenum and attached crude plastic tubes. I found that as slow as 10 mph there is noticeable air flow and over 30 mph there is strong flow. Though my plastic tubes, made from a garbage bag, are not exactly equal, the side vents deliver as much air as the roof vents! In this photo, from left to right, is the right side vent duct, the right roof duct, the left roof duct, and the left side vent duct.
air flow.jpg

[AZPete]

The ducts from the side vents, the roof ducts, and the plenum seem to be working nicely, but I have 2 problems and ask your help.
First, I made an air box for the engine intake (Cobb short intake with conical filter) and mounted it at the right-side vent. Then, I mounted a flex tube from that air box to the intercooler plenum so any air that the engine didn't suck in would be sent to the plenum. Jim said that the engine intake might suck air back from the intercooler, so I experimented. He's right. See how the plastic on the left gets sucked down at WOT:
Air at WOP.jpg

If I connect the flex tube to the plenum directly to the side vent, I need to change the air box to get more air for the engine intake. To the front is the side sail space but that has a hot radiator pipe and any outside opening would pull in air from hot asphalt. To the rear, over the wheel well, I could build a duct that would draw air from the rear corner. Suggestions?

Secondly, my plenum isn't pretty and it's obvious from the large hatch window. One guy at Huntington Beach thought it was a muffler. Any suggestions on improving the looks?
Plenum from outside.JPG

[redfogo]

Any chance there will be an option to buy the scoops? I am using a similar set up you are but am using a different intercooler. I still need to make an air box for it but I planned to do something very close to what you have


Anyways for your intake scoop and maybe you can make this happen I just can't seem to find anyone to help me with my ideas in my area. I was thinking of taking in air from the side window of the coupe top. Basically like a clear naca duct attached to the window so you can still see through it but it provides air to the intake.
pic.jpg

[RM1SepEx]

Dedicate one of the right side vents to the intake, with some sort of scoop the upper side vent should suffice. Box in the intake with aluminum and put that gold reflective material on the side facing the engine compartment/exhaust.

[AZPete]

redfogo: "Basically like a clear naca duct attached to the window so you can still see through it but it provides air to the intake."
That looks like a good solution. Let's both search for that duct. Or, maybe a plexi scoop on the window?
Factory Five plans to make these side vent ducts available, but I don't know when. The ones I have were for testing so they might make some improvements, of course. I drilled a 1/2" hole in the bottom of the left-side duct because it is below the gas filler pipe and if a back-up occurs while filling, no ka-boom pool.

Dan, once I made the intake air box, the IAT temp measured at the MAS dropped a lot, so you are correct that both isolation and insulation are important. However, I learned that the intake at WOT sucks a LOT of air. The side vent duct is not able to deliver enough air at WOT so it sucked air from the intercooler. I'm not an aero engineer but it seems that I need a cool air source that is bigger than a 4-inch tube. Anyone know the area of the OE airbox intake?

Thanks guys.

[mikeb75]

Good job on the v1 plenum Pete, looks much nicer than the v1 we built.

Some ideas we've been kicking around that you may be able to use:
-adding a set of scoops to the quarter windows like redfogo suggests. I've been looking at molding a complete replacement for the glass that includes a scoop that feeds a 3" tube. I expect this location would provide a large amount of air (depending on how aggressive the scoops are) that could supply enough flow to the entire IC.

-repurposing the roof scoop to feed the airbox. It's not ideal without relocation of the intake & air filter, which would require building an entirely new airbox, but it seems many prototype cars prefer this arrangement so there must be something to grabbing air from that region. I would implement this change in parallel with item 1.

-a radical suggestion would be to open your airbox to under the car, but I'm not sure this would work. It would be dependent on if the undercar flow is high or low pressure I think. Again, prototypes seem to run radiators parallel to the ground at the front of the car immediately behind the splitter with good effect, but totally different than what we are discussing.

Your results with the side feed scoops are pretty encouraging, but I am committed to running my oil cooler in the driver side scoop.

[redfogo]

redfogo: "Basically like a clear naca duct attached to the window so you can still see through it but it provides air to the intake."
That looks like a good solution. Let's both search for that duct. Or, maybe a plexi scoop on the window?
Factory Five plans to make these side vent ducts available, but I don't know when. The ones I have were for testing so they might make some improvements, of course. I drilled a 1/2" hole in the bottom of the left-side duct because it is below the gas filler pipe and if a back-up occurs while filling, no ka-boom pool.

Dan, once I made the intake air box, the IAT temp measured at the MAS dropped a lot, so you are correct that both isolation and insulation are important. However, I learned that the intake at WOT sucks a LOT of air. The side vent duct is not able to deliver enough air at WOT so it sucked air from the intercooler. I'm not an aero engineer but it seems that I need a cool air source that is bigger than a 4-inch tube. Anyone know the area of the OE airbox intake?

Thanks guys.

Another idea I was thinking to help with engine bay temps was to vent the back glass window so its more like a Ferrari F40 with the ovals cut outs.

Here are some links to the NACA ducts

Large--https://www.pegasusautoracing.com/productselection.asp?Product=3629

Medium-- https://www.pegasusautoracing.com/pr...FdO3wAodK78GJg

I'm assuming this is something we can't attach to the glass provided by FFR(not sure maybe someone can help us with that) so we will need a lexan type window. Only issue with lexan is that it scratches easier then glass so I am told. I'm not sure if anyone has better experience with this then I do. Because I was also thinking of using lexan to make my back window with venting.

[ben1272]

To improve the look (in my opinion at least), I intend to make 2 plenums that fit over the AAIC each with a fan. They will run more fore/aft than port/starboard and might look like intake manifolds as on some large v8/V10/V12 engines. I think this could look good under the glass.

[RM1SepEx]

Dan, once I made the intake air box, the IAT temp measured at the MAS dropped a lot, so you are correct that both isolation and insulation are important. However, I learned that the intake at WOT sucks a LOT of air. The side vent duct is not able to deliver enough air at WOT so it sucked air from the intercooler. I'm not an aero engineer but it seems that I need a cool air source that is bigger than a 4-inch tube. Anyone know the area of the OE airbox intake?

Pete, what diameter is your air intake tube connected to the K&N type filter? Mines less than 3 inches IIRC, a 4 inch duct in a high pressure area should be just fine. That's why I'm going with about 8 sq inches above my side mount AAIC and whatever I can squeeze out of what was the FFR IC duct in the engine cover on the right side. 3 sq in?

[Sgt.Gator]

Grimmspeed has a line of TMIC "Dyno" Ducts now that may be useful in some fabrications: http://www.grimmspeed.com/top-mount-...wrx-04-17-sti/
TOP MOUNT INTERCOOLER DYNO DUCT - 02-07 WRX, 04-17 STI


TOP MOUNT INTERCOOLER DYNO DUCT - 08-14 WRX, 05-09 LGT
http://www.grimmspeed.com/top-mount-...wrx-05-09-lgt/

[brian b 36]

I did it a little different I used NASCAR brake blowers 100_2512.JPG100_2515.JPG

[Mitch Wright]

Pete, looks like you have room to add a 2nd duct on the LS duct, one for the IC and one for intake air.

[mistasherm]

Not quite there yet in my build, but I was going to attempt to build/create an air channeling set-up for a TMIC on the 818S. Just curious if there is anyone out there that can attest to the amount potential cooling air that could flow from side ducts ahead of the rear wheels. Would also be interested to hear more about the brake blower option; if that is pushing enough air at WOT to keep temps down.

[Mitch Wright]

Tony is drawing air for his R from the side vents.
http://thefactoryfiveforum.com/showt...ild-Seattle-WA

[turbomacncheese]

secondly, my plenum isn't pretty and it's obvious from the large hatch window. One guy at huntington beach thought it was a muffler. Any suggestions on improving the looks?
Plenum from outside.JPG

decals!!!!!

[mistasherm]

Tony is drawing air for his R from the side vents.
http://thefactoryfiveforum.com/showt...ild-Seattle-WA

I checked with FFR yesterday (after reading through Tony's thread) - they have engineered the 818 side air scoops and they are for sale ($149 pair). They have not been placed on the website yet.

[AZPete]

Thanks, guys, for all the great ideas and suggestions! Now I've got so much to think about that I'm paralyzed.

ben1272 - dual plenums is a good idea I wish I had thought of before.

Sgt Gator - Dyno Ducts are another "I wish I had known" item

Dan (RM1SepEx) - you've made me think that if the OE intake is about 3" diameter, I don't need bigger? I've got to learn more about air flow. I forgot that air takes the easiest path (like some people!) so I'm rethinking plans.

mistasherm - I'm glad to see FFR has the side vent ducts available so soon. Jim Schenck said the side vents showed strong flow in the wind chamber tests and the vent ducts they have now made direct air from the entire vent area into a duct at the top, thus a strong air stream. I'm not an aero engineer but I think the side vent ducts will work well in an 818S, though there is less space for a plenum than in the coupe. In my limited tests so far, I wonder if I really need the 2 fans I put in my plenum because there is decent air flow at slow speeds, and certainly no boost to raise temps.

I Love this Forum! Good guys with lots of helpful ideas!

[bbjones121]

Nice! I asked Jim about these ducts awhile back and kept asking Courtnie every time I talked with her. Shortly after the coupe was developed they had these and I thought I heard they were going to be for sale soon...apparently not.

I am glad you were able to test them Pete. Thank you so much for the testing results with these. It is great to see that there is some good movement from the sides, that has been a debated topic for awhile.

I have been playing with the idea of installing inlet ducts in the lower side sails below the back of the doors. I still have not heard anything from the state on my VIN plates, so it may be a little longer before I am on the road testing.

[C.Plavan]

I did it a little different I used NASCAR brake blowers 100_2512.JPG100_2515.JPG

I have those as cockpit blowers in my NP01. I bet it's noisy, because I have a helmet on and they are loud when on.

[EODTech87]

I'm going to take a guess that running a flex tube from these scoops to the intake probably won't work out very well. I would imagine the tube would end up collapsing. What's everyone's opinion on this?

[brian b 36]

There not bad with the back window and the motor running

[AZPete]

Chad, the 2 SPAL fans I have in the plenum are not loud. With the engine running, I can barely hear them, so I added a lighted switch that shows whether on or off.

EODTech, the flex tubes I'm using are from Speedway and have wire coil support, and don't collapse between the air box and plenum at WOT, when under negative pressure. If you connected a tube directly from the side vent duct to the intake, less than 12 inches, I don't see a problem. The side vent duct is very close to the same size as the intake tube. Since you have an AWIC, it would lower your IAT by not sucking in hot engine compartment air.

[AZPete]

After more months and miles, I now think my 2 fans inside the intercooler plenum are useless. There's plenty of air flow from the roof and side vents when moving, so the fans are not needed. I installed 2 switched fans to move air during stop-&-go traffic or at a red light. However, I eventually realized (duh) that when stopped the turbo is not heating the intake air so the ambient air is sucked through the intercooler by the engine, so the fans pushing ambient air through the intercooler offer no help. What was I thinking?