HVAC / Turbulence

[BipDBo]

I live in Florida, so I may consider no heat, no A/C, not even a windshield. Just a motorcycle helmet Ariel Atom style. A removable roof/windshield assembly option would be great but I'm not sure it's feasible.

A completely open roadster won't fly with everyone. Most will build their 818 with a windshield. Some want a hard top. Some will be built with heat and some even with A/C, but the more you add, the heavier you get, and compressors rob engine power.

I'm starting this thread to brainstorm options to keep the cabin a comfortable and reduce turbulence/ buffeting. Here are some ideas:

* A wind blocker could reduce turbulence. One could be placed within the roll bar. This would work with a full roll bar, but some of the designs have switched to double hoops.
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* I remember an old article about Stanford university working on a system called "Open Road" that reduces buffeting on a convertible by passing a duct through the bottom, center of the windshield.
http://www.autoblog.com/2009/07/26/backdraft-does-drilling-a-hole-in-a-convertibles-windshield-al/
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* Someone building a racing or high mpg coupe may not want the weight or power depetion of a compressor, so a rally style roof scoop vent may be a good option.
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[2KWIK4U]

Regardless of weight, I am 250 + lbs, I still am going to install A/C and really would like to see a good top. I think it would be easier to strip the car, for lighter weight, than to try to find places to put my creature comforts on a track version. :)

[kach22i]

I'm starting this thread to brainstorm options to keep the cabin a comfortable and reduce turbulence/ buffeting. Here are some ideas:
Three very good ideas, nice post.

A $500 roof vent is up there, looks like nice quality though.
http://www.mitchellmotorsports.co.uk/trs-carbon-roof-vent-29-p.asp

[bromikl]

Good idea, BipDBo. With no firewall in the front, it should be even easier to do this on the 818. One problem I can see is, if the radiator vents through the hood, the air at the base of the windshield will be very warm. Not sure of a better place to get air from. Maybe someone could divert *some* of the air that goes into the front around the radiator and through the dash. It's worth exploring. Much better than a windscreen behind the passengers - better stylistically and better aerodynamics.

[BipDBo]

Good idea, BipDBo. With no firewall in the front, it should be even easier to do this on the 818. One problem I can see is, if the radiator vents through the hood, the air at the base of the windshield will be very warm. Not sure of a better place to get air from. Maybe someone could divert *some* of the air that goes into the front around the radiator and through the dash. It's worth exploring. Much better than a windscreen behind the passengers - better stylistically and better aerodynamics.

If the radiator vents through the hood, I may want that windshield after all. I suspect it would be fairly easy to duct around the radiator. A tall, skinny, rectangular duct opening could sit to the side of the radiator and transition to maybe a 6" round duct that is routed to a vent in the center of the dashboard.

I doubt, though, that the "OpenRoad" concept would work as well as a wind-blocker. I am reminded of this classic commercial for a Civic Del Sol.

http://www.youtube.com/watch?v=w6oqZCh8Fck

[Oppenheimer]

* Someone building a racing or high mpg coupe may not want the weight or power depetion of a compressor, so a rally style roof scoop vent may be a good option.
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Actually, I'm thinking that the aerodynamic drag of a vent large enough to blow enough air over the passengers to provide any relief will be more than the parasitic losses of the A/C compressor. Weight (of compressor and such) isn't that much of an issue for mileage, except up hill.

So for mpg, A/C (with a good aero body, windows rolled up) will probably be a better bet than than a vent.

[vozproto]

I would venture a guess that the roof scoop wouldn't be quite as parasitic as the A/C (typically 8-12 hp) but then again I dont think I would be quite so happy to have my car lookin like a snork.

I'd happily lug around the extra weight of the system and just turn it off if I feel the need to be naughty.

[slopoke]

could an electric motor be used to power the a/c compressor? ... you would be adding weight, but up front where it could probably be used to help the balance front to back. I'm sure there's a good reason not to ... just looking for alternative methods ...

[vozproto]

You likely could but then you would probably need a larger alternator that draws more power.
More efficient? Dunno.

But it would help with the weight balance for sure. And may make more sense to have it up front anyway.

The gotcha here is the added cost of a new component which doesn't jive with the overall mission statement of this project with the <$10k price point.

[PhyrraM]

IIRC, the Prius has an electric A/C compressor.

I also know the old '90s Calloway twin turbo Vette has an electric A/C compressor.

Given that OEMs are finding that "on demand" electric P/S is more efficient, it's only logical to think that electric A/C might be next.

[bromikl]

One could take apart a $100.00 window air conditioner and run it off an inverter. They use < 1Hp.

[Draco-REX]

One could take apart a $100.00 window air conditioner and run it off an inverter. They use < 1Hp.
Been done. FFR should consider this.
http://1.bp.blogspot.com/_mmBw3uzPnJI/TFq9jraSElI/AAAAAAABgGw/E3_9RDed5dY/s1600/redneck_air_conditioning_01.jpg

[BipDBo]

Been done. FFR should consider this.
http://1.bp.blogspot.com/_mmBw3uzPnJI/TFq9jraSElI/AAAAAAABgGw/E3_9RDed5dY/s1600/redneck_air_conditioning_01.jpg

Swap the boxer for an electric motro, and you've got a hybrid!

[bromikl]

Swap the boxer for an electric motro, and you've got a hybrid!

I have to admit, I've thought of that. But I swear to Dave I will not bolt the generator to the body. I'm imagining a 300 Hp AC motor (no transmission) with enough LiOh batteries to go about 5 miles. Then I'd couple that with an onboard 10-20 Hp diesel generator to continuously recharge the battery pack.

For trips down the block, I wouldn't even have to run the generator. For longer trips, the charging from the generator would +/- = battery power draw at cruising speed.

[BipDBo]

IIRC, the Prius has an electric A/C compressor.

I also know the old '90s Calloway twin turbo Vette has an electric A/C compressor.

Given that OEMs are finding that "on demand" electric P/S is more efficient, it's only logical to think that electric A/C might be next.

Using an electric prius compressor sounds like a good idea. One advantage to putting it up front would be that the condenser coil would likely be up front as well. It might even be possible to assemble the entire refrigerant system so that you could remove it for track day without having to open up the refrigerant loop.

On a serious note about the hybrid comment, I've thought for a while that the 818 just begs to be made into an EV, or a through the road hybrid with an engine on the rear wheels and an electric motor on the front.

[BipDBo]

Here's an example of some slick ductwork, the BMW GTR. I think that thse two small ducts are for cabin ventilation. The 818 could have something similar. A single duct could run under the center of the hood, between two radiator hood discharge vents. As a improvent, this ductwork could be integral to the hood, doubling as structural reinforcement for the hood.
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[Oppenheimer]

The gotcha here is the added cost of a new component which doesn't jive with the overall mission statement of this project with the <$10k price point.

Well I don't FFR ever intended every conceivable option for the 818 to be under the $10K mark. The $10K is for the Roadster version, so it seems a safe bet that A/C would never have been thought of as part of the $10K version anyway. So if A/C is 'extra', if its OK for the A/C option to mean its no longer single donor, then sourcing some of the A/C from another car doesn't seem like a bad idea. If electric compressor were to make sense, I see no reason for FFR not to offer it that way.

[PhyrraM]

Well I don't FFR ever intended every conceivable option for the 818 to be under the $10K mark. The $10K is for the Roadster version, so it seems a safe bet that A/C would never have been thought of as part of the $10K version anyway. So if A/C is 'extra', if its OK for the A/C option to mean its no longer single donor, then sourcing some of the A/C from another car doesn't seem like a bad idea. If electric compressor were to make sense, I see no reason for FFR not to offer it that way.

Yep, I'm sure the WRX interior HVAC unit and underhood condenser could be used just fine with a Prius compressor, if needed.

The SEMA vid says that they are planning a version with power steering. I wonder what FFRs thoughts on that are..... Long lines and OEM motor-driven pump or a 3rd party electric pump?

[vozproto]

I think it comes down to added weight vs added cost.

[Oppenheimer]

I think it comes down to added weight vs added cost.

Really? I think it comes down to people that want AC paying extra for it (and not minding the weight), and everyone else not.

[BipDBo]

Most forum member seem to want a vertical discharge through the hood, myself included.

Ford seems to think it's a good idea for the 2013 Mustang ****** GT500. Somehow, I don't think this small discharge is able to vent all of the air swallowed up by those large openings while its 5.8 liter supercharged, 650 aluminum V8 is pushing this shoebox down the tarmac at 200 mph. I bet at that speed, this thing is pretty scary, and the front end is feeling kind of light, but I bet this vent helps a little bit. I'd like to see under the hood to see how this thing is ducted.
http://www.autoblog.com/2011/11/15/2013-ford-******-gt500-delivers-650-hp-and-200-mph-straight-from/

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[Twinspool]

And I'll bet that car is limited to 155 because nostalgia sells better than it cuts air.

[Admiral Doom]

You'd be surprised how aerodynamic the S197 Mustangs are. Maybe not as aerodynamic as a Prius but it is leaps and bounds better than any previous generation Mustang. They do tend to lift at high speeds but even a small vent relieves a lot of the underhood pressure. Also, remember that the grilles on the S197 Mustangs are mostly closed (most of the mesh look in the front is filled in) so they don't let in that much air.

[BipDBo]

Most forum member seem to want a vertical discharge through the hood, myself included.

Ford seems to think it's a good idea for the 2013 Mustang ****** GT500. Somehow, I don't think this small discharge is able to vent all of the air swallowed up by those large openings while its 5.8 liter supercharged, 650 aluminum V8 is pushing this shoebox down the tarmac at 200 mph. I bet at that speed, this thing is pretty scary, and the front end is feeling kind of light, but I bet this vent helps a little bit. I'd like to see under the hood to see how this thing is ducted.
http://www.autoblog.com/2011/11/15/2013-ford-******-gt500-delivers-650-hp-and-200-mph-straight-from/

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Wow, FFR is really taking that trademark issue with ****** seriously. They're even replacing every instance of "******," with "******."

[BipDBo]

How's this for a model of good airflow, both around and through the car! This is the mid-engined, 2012 Corvette Daytona. Form through function. It's beautiful. I'd like to see it with some body panels removed. Intakes are strategically placed at high pressure areas and they are minimally sized. Cabin ventilation is simple enough. It just comes through those two holes along the bottom edge of the windshield.
http://www.autoblog.com/2011/11/15/2012-chevrolet-corvette-daytona-prototype-unveiled/
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[kach22i]

How's this for a model of good airflow, both around and through the car!
I saw this car posted in the Pelican forum earlier today.

http://forums.pelicanparts.com/off-topic-discussions/640211-corvette-prototype-grand-am.html

We know that racing cars are built with down-force and traction in mind and are often high drag, not low drag cars as a result. However the teardrop canopy of the Daytona Prototype promises something different. Based on what I know, the roof comes back too quickly to be considered aero-template perfect.

I've seen several threads on aero caps for pick-up trucks, people have built caps similar to the Dayton's canopy, but they did not do well on the tuft test.

http://ecomodder.com/blog/makings-pickup-aerocap-vagos-dakota/
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He later switched it to a simple 12 degree slope with a bow in it and rounded edges.

2nd try: with about a 10% improvement over the first one.
http://ecomodder.com/forum/showthread.php/t_vagos-compound-curve-foam-board-pickup-aeroshell-15862-16.html
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