Max use of stock IC

[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:
<<>>





But on the Coupe there is no turbocharger, and no big scoop:
<<>>


and

[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.

[Scargo]

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