Max use of stock IC

[freds]

36231

I think (hope) the low pressure behind the car and in the engine bay will assist with some "sucking" through the IC. I'm about to install temp sensors before and after the IC to monitor.

I will test with and without the polycarbonate separation panel.

[Mechie3]

I saw higgins rally car in person two weeks ago. They put the radiator in the back, added two scoops to the rear window. Each scoop fed a large round duct (looks like giant brake ducting, ~12" diameter) that fed into a cover molded to fit on the front of the radiator and seal the edges. I didn't take a pic, but that's the best way to go I think.

Looking forward to some data on your setup.

[philly15]

I'm curious, would there be any benefit to hooking say a radiator fan in and mounting somewhere on the inter cooler? I have like 4 fans Latin around and was contemplating if that would help? Any thoughts?

[Mechie3]

I think someone did that. Maybe Wallace18?

[philly15]

I think someone did that. Maybe Wallace18?

Thanks I'll look into it. Im sure it would help at least a little, maybe more if combined with an intercooler sprayer system like the STi and later wrx.

[freds]

Having thought long about the issue I have come to the conclusion that without effectively ducting all the available air exclusively to the IC everything else is not going to help much. (From wherever the cold air is sourced ..humps, side vents etc.)

The air will take the easiest way it can, and with all the wide open spaces around the IC , it seems that going through the IC is absolutely the last route it is going to take. In addition the hot air rising from the engine in front of the current IC setup is not helping!

In addition only adding fans on the IC (without ducting cool air to the fans) they will likely be sucking mostly hot air from above and around the engine ....

What I have done is, in effect, made a large inlet plenum for the IC air, and wherever cold air is sourced from....that air has to go through the IC.

Instead of trying to make some convoluted pipework ducting to get around the roll bar braces etc.and making it fit the IC I realized that the whole volume under the engine cover and above the engine could form one simple large volume plenum.

So after creating the plenum, adding fans (if necessary) onto the IC will be of much greater effectiveness. Or force feeding air into the plenum, say from a fan on the front of the hump(s), that air has to exit through the IC, and as mentioned the low pressure assumed to be in the engine bay will/might help to suck air through the IC

Adding fans (or similar) will be my next step when I have some data using just the upper side vents.

And obviously a larger non stock IC is another possible simple adder.

So once the plenum is there, many many options as to how you get cold air into it are possible

All of this is cheap and easy, and does not have any heat soak issues.

I believe that there is much to be gained by doing the correct thing for the air cooled IC that will help its effectiveness. Which is what I am going to experiment with before I seriously consider going to Air-Water.

fred

[wleehendrick]

Fred, thanks for paving the way on an solution for the tmic. From an engineering perspective, this will obviously work if the ducting is done rights, as the 911 turbo can make gobs of power reliably with 2 moderate sized a2a ics. The key is each is well ducted and vented for good airflow. Please keep as posted, as I'd like to follow a similar path.

[longislandwrx]

Jerome tried fans, with disappointing? results. you need more (cold) air I think it can work, just needs more engineering.

I am going one of ways... two ducts from the side (hopefully with CF scoops ;) ) 4x brake hoses feeding the IC, or repurposing a CF WRX/STi scoop directly above the IC and using the proper seals.

Last resort is going water... I just don't want the weight.

[freds]

Jerome tried fans, with disappointing? results. you need more (cold) air I think it can work, just needs more engineering.

I am going one of ways... two ducts from the side (hopefully with CF scoops ;) ) 4x brake hoses feeding the IC, or repurposing a CF WRX/STi scoop directly above the IC and using the proper seals.

Last resort is going water... I just don't want the weight.

I want to state clearly that I am not pushing my analysis as "the answer" or absolutely "correct".

These are my thoughts, and believe them to be "interesting" enough to put them out on the forum for other opinions and reasoning.
I don't have the budget for a water cooled system (or the need), but was severely critical of FFR supplied, what they called ducts, and did not want to feed my engine overheated air..... And just adding fans I figured would only blow hot air through the IC

Wind tunnel work by FFR indicated very little, if any, flow into the lower side vents. My "feel by hand" indicates good air flow to the upper side vents.So how far the lower side vent scoops would have to stick out to get any decent flow ???

My points are:

That for about $100 you can isolate the IC inlet side from virtually all engine compartment hot air;

After that it a matter of choice where you source cold ambient air from;

Any fan or blower addition will then have the best possible effect;

The assumed low pressure in the rest of the engine compartment as a result of the rear vent is likely to assist drawing air through the IC. I have not opened my lower side vents hoping to keep the engine compartment pressure as low as possible. It will be easy to open up a feed from the plenum if it gets too hot in the engine compartment;

With the large plenum, there are many possibilities where, and how many air inlets one chooses to make, and whether to use a blower to force air into the plenum.

That all said, I am going that way and will report as i get any data. Big thing is there is no downside...nothing I am doing is irreversible or expensive.


fred

[longislandwrx]

Wind tunnel work by FFR indicated very little, if any, flow into the lower side vents. My "feel by hand" indicates good air flow to the upper side vents.So how far the lower side vent scoops would have to stick out to get any decent flow ???



Upper side vents are an option as well if they are opened up. some Mr. 2 or Lamborghini style scoops could easily grab tons of air.

I appreciate what you are doing, as soon as someone comes up with a good a2a setup, its only going to get better as it's developed further.

[RM1SepEx]

FFR didn't open the side vents much, their aluminum with holes and a 1/2 wide trim reduce the actual open area at least 2/3 from what is available. I'm getting close to being able to fire mine up, new body takes time to mount but you can see how much can be made available here.

36349

I have a 10 inch fan against the rear and will seal off the inlet and add the CF scoop that Craig (Zero DB) is making up. I feel that we can get the air flow pretty good using this approach. I also agree that with some creative work you should be able to add scoops and open up the two existing IC vents to improve flow through the stock IC, it just will be difficult to manage the flow. The FFR aluminum just doesn't open enough, doesn't force air in and had to be made to work with a variety of stock Subaru IC's. Unless you customize to your situation it just can't work.

We should be able to get flow out through the rear vent screen, making the engine area a sort of tunnel since the top and bottom are closed off. I'm not planning on opening the IC vents or the trunk lid vent

While my 2.5 inch IC tubing does run over the top of the turbo, between a turbo blacket and Zero DB heat shield and the high flow rates of intake air I'm not very concerned about the IC operation with my side mount setup

36353

I'm also expecting to be able to duct cold intake air through this scoop and could use the IC scoop to assist if needed

[flynntuna]

Upper side vents are an option as well if they are opened up. some Mr. 2 or Lamborghini style scoops could easily grab tons of air.

I appreciate what you are doing, as soon as someone comes up with a good a2a setup, its only going to get better as it's developed further.


A lot of ideas can be lifted from our GTM brothers...

[Bob_n_Cincy]

I like these scoops.

36366

Actually, I like the whole car.
Bob

[ssssly]

Planning on something more akin to this

http://www.hdcarwallpapers.com/walls/2014_porsche_918_spyder-wide.jpg

[Junty]

36368
For those that can - plan for alternative IC. Try what I used on my stock 2012 WRX engine. These later engines have an almost square intercooler - as apposed to the long narrow original with Y pipe. These later IC's are about 11 x 9 1/2 inch - so Ive mounted a 10inch radiator fan on top. Just fits under the engine cover and Ive used a powerful (high speed fan motor) pushes a huge amount of air through the IC!
Yet to get all the body properly mounted - but I'm hoping that this will temporarily get me through to full compliance and registration before I add bigger turbo and AWIC.

[zippytheclown]

forgive my ignorance, I don't own an 818 (yet) but I've owned a couple of wrx's and I know what a weapon they are, I can only imagine the power to weight when you shed 600 odd kilograms. Has anybody thought of, or actually mounted the intercooler in the front? My my03 had a front mount and obviously was piped from the front to the intake, would the extra distance from the front of an 818 to the rear engine be viable or would you lose any possible advantage with that distance the cooler air has to travel?

[ssssly]

Would loose a lot of power and responsiveness. If the stock turbo could even deal with that much volume.

[freds]

This thread seems now to be focusing on where the air inlets are and how large they are. Undeniably this is critical under any circumstances! That can be addressed in so many ways, but I'm not about that, just commenting on using the existing FFR upper side inlet vents...because they are there, and if they function adequately for my wants...good for me!

My focus is/was on almost totally isolating the inlet side of the IC so that wherever that incoming air comes from or whatever volume/minute it is....the only place it can exit is through the IC, and no hot can be drawn from around the hot engine parts.

I particularly like the fact that that can be done very simply for about $100 and no complex duct work to fit exactly onto the IC. The 818 configuration under the engine cover and over the upper chassis members makes this a snap.

With that isolation done all the creative juices can be focused on how best to get air into that space and there is a lot of real estate that can be penetrated to get into that space, as ducts or openings do not have to end up in front of the IC...just anywhere into the plenum will be good, as it all has to exit through the IC. Have at it..I'm really interested to follow where that goes.

fred

[Mitch Wright]

Fred,

I am going down the same path that you are exploring. I don't want the weight or have the budget for a AWIC. I will not have a passenger seat and plan to seal and duct air from the right side hump to the IC. It will be after the first of the year before I get started on that project. Looking forward to seeing what you come up with.

[freds]

Fred,

I am going down the same path that you are exploring. I don't want the weight or have the budget for a AWIC. I will not have a passenger seat and plan to seal and duct air from the right side hump to the IC. It will be after the first of the year before I get started on that project. Looking forward to seeing what you come up with.

Hi Mitch, Opening up the front of the RH hump is a perfect place to let cold air into the plenum. You could even easily mount a blower right there to force feed the air in.

As far as what I've come up with, if you take a look at the pictures in the first post on this thread, the polycarbonate sheet is fitted and the aluminum profiles to seal up against the humps are fitted too...so I'm done with the isolation of that whole area/volume ahead of the IC.

Now I need to install my in/out temp sensors and report bak on results with the polycarbonate in place and without. After that I'll work on where I pull air from on my 818S, where the RH hump is not an option.

fred

[ssssly]

Sealing around the IC to channel available air will work much better to maximize available airflow.

There is however very, very little airflow in that location.

There is almost no airflow at IC opening, top vents in the rear fenders or humps. The shape of the front of the car and the windshield push the air up and over that area.

I spent quite a while with Jim at FFR going through the wind tunnel media to identify where to pull air in for the IC.

My first plan, prior to seeing the media, was the humps. Won't work.
We then looked through stuff to see about the side and rear top vents. Won't work.

The mass volume of air at the side and rear top vents is about 3"s from the existing body. Hence my plan to widen that part of the body to route the air.

I will also be making a shroud to channel the air through just the IC.

And until I get that sorted out, running some fans. The MR2 crowd has had success via this route with a similar configuration.

[C.Plavan]

After running this last weekend and feeling the heat that was trapped and coming out of the rear, I really do not see how anyone could go without a AWIC. My AWIC only took 1.5 gallons of water. I'll take that weight for having a cooler charge.

[wleehendrick]

My focus is/was on almost totally isolating the inlet side of the IC so that wherever that incoming air comes from or whatever volume/minute it is....the only place it can exit is through the IC, and no hot can be drawn from around the hot engine parts.

^^^^ This x1000!!!

The key is to get cool air to go through the IC; which the 818 in stock trim clearly does not do. There's nothing really magic about an AWIC; the water adds thermal mass which provides some protection against short term temperature spikes, but they will certainly heat soak if the radiator can't dissipate the heat. At the end of the day, both types are limited by air flow, and insuring that is key to a robust system whichever route is chosen. It's just obviously much easier to get good airflow in the front.

There are plenty of Mid/rear-engined turbocharged super-cars that work fine with A2AIC's in the back. The engineers did their homework getting the air to flow through the IC; FFR has left that task to us ;) If the vents can provide enough airflow with scoops, great! If not, then fan(s) may be needed. Since I'm building a street car, I would prefer to have the space for a small trunk and avoid the weight and complexity of an AWIC, so I'm hoping this works.

[Hindsight]

There are plenty of Mid/rear-engined turbocharged super-cars that work fine with A2AIC's in the back.

To my knowledge, they are all hard-tops though. Immediate example coming to mind is the 911 Turbo. I think the Turbo MR2 had one as well but can't remember for sure.

Much easier to get airflow to an A2A in a rear/mid engine car if it's not a convertible. I can't think of any convertible rear/mid engine turbo with an A2A.

[wleehendrick]

To my knowledge, they are all hard-tops though. Immediate example coming to mind is the 911 Turbo.

But they make a 911 Turbo Cabriolet:

36397

The rear fender vents duct air to an IC on each side, which exits low behind the rear wheel. I think the old 911 turbos had a single IC in the 'whale tail'. Stuttgart designed the new ones to take advantage of wide rear haunches and low pressure behind.

[matteo92065]

What are your thoughts about the movement of the engine & TMIC assembly? Other builders have documented the motor moving a total of 1.5" (with stock motor mounts). The hard sheets (sheet metal & plastic) would have to have a minimum gap of .75" around the TMIC, and then something soft to bridge that gap to make a sealed plenum.

[RM1SepEx]

This thread seems now to be focusing on where the air inlets are and how large they are. Undeniably this is critical under any circumstances! That can be addressed in so many ways, but I'm not about that, just commenting on using the existing FFR upper side inlet vents...because they are there, and if they function adequately for my wants...good for me!

My focus is/was on almost totally isolating the inlet side of the IC so that wherever that incoming air comes from or whatever volume/minute it is....the only place it can exit is through the IC, and no hot can be drawn from around the hot engine parts.

I particularly like the fact that that can be done very simply for about $100 and no complex duct work to fit exactly onto the IC. The 818 configuration under the engine cover and over the upper chassis members makes this a snap.

With that isolation done all the creative juices can be focused on how best to get air into that space and there is a lot of real estate that can be penetrated to get into that space, as ducts or openings do not have to end up in front of the IC...just anywhere into the plenum will be good, as it all has to exit through the IC. Have at it..I'm really interested to follow where that goes.

fred

Fred, there isn't any good positive pressure air flow at those top of rear fender vents and no good flow through the IC out the back of the car, just sealing it isn't going to solve your problem. The stock setup uses a scoop in a high pressure area in front of the windshield to force air through the IC core. Even sealing it and using a fan will have little effect about 1/2 of the backside of the IC is blocked by those stupid Y tubes

[freds]

After running this last weekend and feeling the heat that was trapped and coming out of the rear, I really do not see how anyone could go without a AWIC. My AWIC only took 1.5 gallons of water. I'll take that weight for having a cooler charge.

Right, all of that heat is really bad. I'm just trying to keep it away from the inlet side of the IC and make it possible to feed whatever-ambient-air-I-get through the IC without getting it mixed with all that hot air. The polycarbonate sheet I'm using can quite simply be insulated too (to stop both convection and conduction heat transfer). And I'm soon to have facts, ........as soon as I install the in/out sensors.

I am in no way trying to get into a competition or pissing contest with AWIC, I simply don't have AWIC in my budget, and cannot possibly leave just FFR supplied "stuff" as is because it is so obviously totally inadequate in my view.

Thanks to you and all others for the input though...that's what I wanted by starting this thread.

fred

[freds]

Fred, there isn't any good positive pressure air flow at those top of rear fender vents and no good flow through the IC out the back of the car, just sealing it isn't going to solve your problem. The stock setup uses a scoop in a high pressure area in front of the windshield to force air through the IC core. Even sealing it and using a fan will have little effect about 1/2 of the backside of the IC is blocked by those stupid Y tubes

Dan,thanks...I'm not trying to "solve" my problem with one brilliant move, I'm trying to improve what I've got one step at a time. And as far as I can reason through what I'm doing...I cannot possibly make it worse and fot $100 and some hours I am going to get some facts.

fred

[RM1SepEx]

Add some external scoopage, big ones, to get into some high pressure airflow

[wleehendrick]

Add some external scoopage, big ones, to get into some high pressure airflow

And/or fan(s) strong enough to push the equivalent volume of air through it... I wonder what it would would take to get to the same CFM that a WRX hood scoop generates at speed? (not that that's ideal, but at least the minimum we should shoot for)

[RM1SepEx]

I don't have a WRX scoop but let us just make some simple assumptions...

2 inch tall by 1 foot wide, in a high pressure airflow at speed, perhaps 60 MPH? only inches long, no flow associated losses, that's a lot of air! The side vents are in a low pressure area with the nose and windshield directing air up over the body. Their combined open area is about 1.5" high x 10" wide and the air has to flow a couple feet on each side in a rectangular duct, flow losses are not high because almost no air will flow. If you increase the flow, losses will be high as the path isn't smooth. How can you pull from underneath, there isn't any space?

There isn't a low power fan capable with those two side of the engine cover vent locations. It is a tortured air path, too much air required to flow through a long and convoluted path. Too much restriction blocking flow underneath. If you want to feed that IC location like it is in a WRX you need a big honking snorkel type scoop higher than the roof of the car.

As a Mechanical Engineer I did take those fluid dynamics classes back in the pre computer dark ages! My MS addled brain still remembers those long nights studying for heat transfer too, my least favorite class of my entire college education. (I had a little "I'm done with heat transfer, passed that BI***" party. I set that book ablaze! ) Heat tranfered then, didn't it! LOL

[129st]

I assume the goal of this thread is how to get the lowest temperature combustion air coming out of the TMIC without going to the expense of an AWIC. Fred is doing a great job in organizing thoughts on how to duct cooler air to the TMIC. I would add that another way to help achieve the low temperature combustion air goal is to lower the temperature of the inlet compressor air (the air coming into the air filter.) It might be advantageous to include the air filter mount into the ducted cool air (and not just pull this air from the side of the engine.)

[tmoretta]

How about a scoop under the roll bar - between the seats? Maybe could be ducted down and back to in front of the IC.

[Mechie3]

But they make a 911 Turbo Cabriolet:


The rear fender vents duct air to an IC on each side,

Here's a photo of the 996 TT intercooler. You can see it is sealed by a duct that then seals to the bodywork (or another piece of duct) to create a high pressure area.

http://img189.imageshack.us/img189/6564/turbo5.jpg

When I was an intern at GE I worked on a related problem with an arc bulb (HID) in a small table top box. The cathode needed to be at 140C IIRC to maximum light output. Previous attempts by other interns had used bigger fans, more fans, more baffling to direct air. I made a sealed chute from a fan directly to the air inlet and it kept it right at 140C with a single small fan. The trick was to create the high pressure area. Freds is taking a correct step in sealing the front from the back to create that high pressure area, now there just needs to be a way to feed the front area to increase the pressure.

[ssssly]

Someone please correct my math or logic if I am wrong.

Numbers approximated and does not take into account compression due to flow direction changes or skin effects.

Approximate size of v8 IC splitter, 18x6 squarish eclipse. For an area of ~84"s. This is the size of the splitter on my 05 spec C. I ran a gtx3071R at 22psi with water spray on this car with IATs under 95 degrees all day on the track. And regardless of scoop size this would be the max area of uncompressed air that could be flowed to the IC.

Simplified area to circle with a diameter of 10"s.

And flow rate = 1/4(pie)(diameter)squared(velocity) we get ~2880 cubic ft/min of flow at 88ft/s velocity (60mph).

According to the interwebs, 16-18" fans can be purchased that will flow ~3000 c ft/m. Assuming neutral pressure.

So assuming that the current IC intake sits in a low pressure region, which from the wind tunnel media it appears to be, even with a sealed and ducted 16-18" fan enclosure (which there really isn't room for), because it would be running at reduced efficiency due to the low pressure region, indicates to me that additional air from someplace still needs to be routed to the IC to get to the required volumetric flow rate for stock IC efficiency.

The fan would be a definite improvement. But it is not likely to get you back to stock efficiency without an additional volume of air routed to it from someplace else. Requiring something getting the air to the fan from a non low pressure region.

And preferably something not creating an enormous amount of drag, defeating the point of making more power just to have to overcome drag. And if it could redirect the air to where needed an create rear downforce, something also woefully needed on this car, a plus plus.

I'd really prefer not to engineer something I don't have to, so if I am wrong, please lite me up.

Particularly RM1SepEx, I dabble in fluid dynamics hobby wise. Mostly for designing horn loudspeakers, so pretty specialized to acoustic compression. But I'm not versed in heat transfer or taking the extra steps to account for laminar flow changes due to direction changes effecting flow volumes and the such.

[RM1SepEx]

Your math is correct, this situation is so obvious that I wouldn't bother with the math. Bottom line is it is not possible to get the stock IC in the stock location to work any where near as well as it does in a WRX, just can't happen. Since the air intake temp is an important tuning variable higher than expected intake temps = BOOM under high load. And let's be honest who won't be using the power? :o There isn't any place where you can put a fan of any size in the airflow on the FFR design, the IC flow is not possible if you use a std windshield. An "R" could use a simple scoop, wear a full face helmet and a shield.

That's why many have went to a AWIC, you can use an easy to move/control heat transfer "fluid" Putting the heat transfer device in the high pressure area solves that problem. Intake temps should be very well controlled. You end up transferring the heat twice...

I've chosen to go with relocating my IC to the side where I can scoop out the air with a CF addition to the body. As long as it is out in the higher speed airflow I should get good performance. Between a better designed, larger core and its location the problem should be solved. My 2.5 inch tubes make space a big problem, I would use 2 inch if I did it again (or if I wasn't so cheap or bull headed) I'm thinking that on the left side of the car the scoop would funnel air to an oil cooler...

[SkiRideDrive]

Has anyone tried pulling air from under the chassis?

[RM1SepEx]

Has anyone tried pulling air from under the chassis?

? by what route could you get clean air to the top of an IC that is mounted on top of the back of the engine and front of the transaxle? Then the air has to flow through the core out the bottom and exit through the rear vent area above the rear bumper...

[ssssly]

RM1SepEx...In the video when they smoke wanded the car, air flowing from the front of the car does not enter the the side inlets. Goes right around it. some air looked to be getting pulled up from behind the front fender just aft of the door seam and dragged along the body into the vents.

So yes, there is more air there than the stock location. And in theory, the volume would increase with speed. But the air is not laminar and its not the full volumetric flow of the opening. I am planning for oil cooler on one side tranny cooler on the other with some 3d printed AB shrouds. Interested to see what kind of results you get with your setup.

If you had an IC with inlet/outlet on either end you could duct the air off the bottom of the car, around either side of the engine and then to the bottom of the IC blowing the hot air out the top. Trick would be what it did to downforce by disrupting and stripping that much air off the bottom of the car. And you would want a screen in it.

[RM1SepEx]

The minute you add the scoop the flow should change quite a bit, it will be key to have it extend out from the body, the FFR side vents had that trim ring area as a solid "wall" forcing air away from the body and that aluminum with a large % being essentially solid. A boundary layer develops and sort of smooths out the flow along surface irregularities. Even cutting the vents so that they were simply an edge at the thickness of the body would make a difference. When you add a fan on the backside of the IC you will allow the flow to curve back in as well.

I'm reminded of the old wing windows that cars had before AC was so available. It only took a couple inches of protrusion to make the air start flowing into the car vs out around the car's greenhouse area.

The bottom area has no easy flow route and as the route gets more bends and increases in length the flow reduces.

[LoneEagle]

Here are some tips that will hopefully be of value on this IC issue. I've dealth with issues on aircraft engine overheating and do Fluid Dynamics for a living:

NACA scoops are quite effective on aircraft, are flush mounted, and look pretty good. I've used them to provide cockpit ventilation. Of course at low speeds, the airflow will be diminished. The location will be important as discussed earlier. They need to be next to the airstream around the car. The low pressure area behind a rag top would not be a good place to locate them as discussed previously.

Sealing the high pressure inlet side is very important, also discussed at length earlier. Doesn't take much of a hole to allow a lot of air to bypass the IC. The fact that the engine can rock presents issues with the seal design. So inlet placement and seal design are a couple of the biggest issues. Another reason this is important is to prevent recirculation of hot air from the engine compartment. This was a big deal for auto air conditioning condensors. We used to use a thermcouple grid to measure it and it was surprising how much recirc happens at a stop, especially with a tailwind.

In aircraft we use a rule of thumb. Air exit needs to be 2-3 times larger than the inlet to provide the needed low pressure on the exit side (probably not an issue with the 818). Many aircraft use a fence on the bottom of the cowling to reduce pressure at the cowling exit. They are very effective, but do provide a bit of additional drag. They are typically 1-2" deep and extend across the bottom of the cowling. Something like this, if placed just ahead/beneath the engine compartment, could help suck more air out. Ground clearance may be an issue to consider. Using scoops to feed the engine compartment is a bad idea becaused it provides the opposite effect, an increase in pressure.

Aircraft Spruce and Specialty carries a variety of ducting, sealing, and NACA scoop materials. They are a reasonably priced supplier and their online catalog is easly to navigate.

I am not at this point in my 818 project, but if down the road I craft up a solution that works, will provide info to the forum...

Lone Eagle

[freds]

Here are some tips that will hopefully be of value on this IC issue. I've dealth with issues on aircraft engine overheating and do Fluid Dynamics for a living:

NACA scoops are quite effective on aircraft, are flush mounted, and look pretty good. I've used them to provide cockpit ventilation. Of course at low speeds, the airflow will be diminished. The location will be important as discussed earlier. They need to be next to the airstream around the car. The low pressure area behind a rag top would not be a good place to locate them as discussed previously.

Sealing the high pressure inlet side is very important, also discussed at length earlier. Doesn't take much of a hole to allow a lot of air to bypass the IC. The fact that the engine can rock presents issues with the seal design. So inlet placement and seal design are a couple of the biggest issues. Another reason this is important is to prevent recirculation of hot air from the engine compartment. This was a big deal for auto air conditioning condensors. We used to use a thermcouple grid to measure it and it was surprising how much recirc happens at a stop, especially with a tailwind.

In aircraft we use a rule of thumb. Air exit needs to be 2-3 times larger than the inlet to provide the needed low pressure on the exit side (probably not an issue with the 818). Many aircraft use a fence on the bottom of the cowling to reduce pressure at the cowling exit. They are very effective, but do provide a bit of additional drag. They are typically 1-2" deep and extend across the bottom of the cowling. Something like this, if placed just ahead/beneath the engine compartment, could help suck more air out. Ground clearance may be an issue to consider. Using scoops to feed the engine compartment is a bad idea becaused it provides the opposite effect, an increase in pressure.

Aircraft Spruce and Specialty carries a variety of ducting, sealing, and NACA scoop materials. They are a reasonably priced supplier and their online catalog is easly to navigate.

I am not at this point in my 818 project, but if down the road I craft up a solution that works, will provide info to the forum...

Lone Eagle

Thanks for this post

fred

[Sgt.Gator]

Looking at Turbo Radicals for inspiration. As noted the open top Radicals use a large scoop. I think someone here will make a knock off style Radical engine cover that uses a scoop like that for the R:
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http://www.sr3sl.com/wp-content/uploads/2012/07/home_11.jpg

http://www.sr3sl.com/wp-content/uploads/2012/07/home_21.jpg


But on the Coupe there is no turbocharger, and no big scoop:
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http://www.radicalsportscars.com/uk/rxc/assets/images/radical-rxc.png

http://www.radicalsportscars.com/uk/rxc/assets/images/home-video.png and http://www.radicalsportscars.com/uk/rxc/assets/images/home-technical.png

[Mechie3]

Using scoops to feed the engine compartment is a bad idea becaused it provides the opposite effect, an increase in pressure.

I assume you mean using scoops to generally fill the engine compartment is a bad idea, correct, as it increases pressure behind as well as in front of the IC. If you block off the rear of the engine compartment then pressurizing the front via scoops is good. Only problem is that there is no way to realistically seal off the back of the IC from the incoming air unless you make a huge shroud all around the engine bay or make a shroud that sits on top of the IC and isolates incoming air.

[Bob_n_Cincy]

I will need all the scoops I can get to bring air into the engine compartment. My radiator and AWIC heat exchanger will be right up against the rear tail lights. With 2 large cutout in the back of the car. I'm banking on the low pressure behind the car to suck hot air out of the engine compartment.
Bob

[freds]

I assume you mean using scoops to generally fill the engine compartment is a bad idea, correct, as it increases pressure behind as well as in front of the IC. If you block off the rear of the engine compartment then pressurizing the front via scoops is good. Only problem is that there is no way to realistically seal off the back of the IC from the incoming air unless you make a huge shroud all around the engine bay or make a shroud that sits on top of the IC and isolates incoming air.

Unless I'm missing something (and it does happen..hahaha). What I am doing seals off the front of the TMIC from the engine compartment....which in effect forms shroud on top of the IC which isolates incoming air from the engine compartment. (Or, if you like, makes the whole of the engine bay below it "shrouded") And yes...you do not want to pressurize the engine bay.

It is in fact a large volume "shroud" which can be fed with cold air from many locations, but however it is fed the cold air can only exit through the IC into the low pressure engine bay. Air can be ducted or be force fed into the plenum with blowers scoops or whatever, which are not limited by the size of the frontal area of IC.

The fact that I am adding only the polycarbonate isolation sheet at first and will check its effect on my temperatures with only the top "fender-vents" is merely part of a step by step way of checking things by changing only one thing at a time and measuring its effect. (The good old classical way of all diagnostic and development work).

Let me know. All ideas and questions are what this post is about.

fred

[Sgt.Gator]

Freds, I think if you have more than one scoop/intake into the big plenum area you will find air flowing in from the one with the most positive pressure, but likely flowing out the others with lower or negative pressure, not thru the IC and out. At least not as much as you would hope. It seems like you would have to use only one scoop to feed the plenum, and the only exit possible is thru the TMIC. I can't think of any scooped air in any application that uses more than one scoop to feed a common plenum. I've seen one scoop divided mid way down it's duct track to feed two separately ducted devices like an air intake and oil cooler, but never the other way around.

[Mechie3]

Unless I'm missing something (and it does happen..hahaha).
fred

No, I don't think you are. I wasn't clear on what I was thinking in my head. I was thinking about the big side scoops I'm working on. They are beneath the shrouding IIRC and would pressurize the engine bay. The top mounted vents would feed just the top if the IC was sealed against the engine cover and the firewall. I'm intending mine to be used for side mounted IC's, heat exchangers, or to flush the engine bay for those using AWIC's that just want to vent engine bay heat or feed rear mounted radiators.

[ssssly]

Keep in mind rear mounting the radiator will shift about 20lbs rearward.

Keep in mind that with the engine compartment open on the bottom, the hot air is going to be expanding from the rear of the trunk near the taillights.

Unlike a WRX that forces air through the intercooler and then out of the back of the engine bay with additional air flow coming in through the front of the car. The 818 would be pushing the air through the intercooler and it has no place to go.

High pressure air coming off the underside of the car is going be pulled up into the open engine compartment. Since the area above the IC is low pressure, that is where is it going to head.

One of my other projects is to extend the underbody out to the tranny to move that high pressure boundary rearward and push that air out the rear bumper openings. Along with a through duct or two to vacate the hot air coming off the engine out the back of the car as well.

Basically to create a convection circling down through the IC, along the bottom of the engine compartment and out the rear bumper. And another pulling hot air from the engine up and then out the rear.

With some of the basic calculations I have done, just extending the bottom of the car past the IC opening, should promote much better cooling than stock. It could also increase airflow through the side vents. Wouldn't bet too much on that though.

[RM1SepEx]

If you bought the rear diffuser the engine is closed on the bottom...

[Mechie3]

I've shared this photo elsewhere for different reasons. I want/plan to make the rear of my 818 emulate this (not the fender flares, just the back end). It should help vent the rear.

http://www.lotustalk.com/forums/attachments/f163/78829d1208151374-lotus-exige-gt3-hi-res-wanted-exigegt3.jpg

[Scargo]

Racecar! I plan on using an LED strip for brake lights and carving out a lot of the back end.