HiPSI

iTrader: (2)

It's 100% the transmission tunnel that causes the excessive heat. During the winter months its actually not a bad thing but during summer it is noticeable within 5 minutes of driving.

Next time the transmission comes down I'm going to make sure and use some heat shield products on the tunnel and above the tunnel to make it better.

t2d2

iTrader: (8)

Thanks, grumpi! That sounds worth investigating. The price is low enough that it would pay for itself after a few tanks of not having to run the A/C. Does anyone know how much space there is above the headliner for installing a thin blanket like that?

100% disagree. I have no discernible heat coming from the tranny tunnel when driving, and my excessive temperature observations have come when the car has sat all day.

t2d2

iTrader: (8)

Here's a few more data points.

5/04/15: 115.5° @ 63° OAT - mid-afternoon & sunny
5/07/15: 93.6° @ 72° OAT - late afternoon, 1-2 hrs after closing roof visor & putting sun shade in window, mostly in the shade
5/08/15: 94.1° @ 80° OAT - 6pm (no direct sun), roof visor closed & window sun shade up all day
5/09/15: 167.8° @ 81° OAT - 3pm (direct sun), roof visor closed & window sun shade up all day

After the 5/08 and 5/09 measurements, I was thinking the front windshield might be a key element, i.e., clear tint it and block much of the heat. However, after today's measurement in direct sun with the window/roof shades all day, that theory is thoroughly busted!

I'm scared to think what that number would be without the window and roof shades... I can't imagine it getting a whole lot hotter than 168°, so I'm leaning toward calling b.s. on the claims that the reflective window shades drop SC cabin temps by 40°. They're probably beneficial for the dash, but that's about it.

t2d2

iTrader: (8)

BTW, I was thinking about houses/buildings vs. cars, as far as heating and cooling needs. Occupied buildings need heat added much of the year, whereas a car's heating needs are basically 100% provided by the engine. Cars really only need cooling, unless you spend a lot of time sitting in your car going nowhere on chilly days.

So, why aren't buildings designed more like cars and cars more like buildings?? Vent the car's cabin like a leaky building so it doesn't create a mobile greenhouse, but do so intelligently so it doesn't attract moisture and wind noise. And seal up the buildings in a big glass bubble that stays warm throughout the year!

grumpi300

iTrader: (1)

idk if it would fit over the headliner but that's actually a pretty good idea if it does fit. but man will the car become super heavy considering people put it on trans tunnels, + dynamat the whole car. some even put layers of dynamat.

t2d2

iTrader: (8)

Wait, those thermal blankets are heavy? I figured they weigh next to nothing, like a space blanket with some fluffy insulation attached.

I'm not concerned with dynamatting the car. That stuff is indeed quite heavy, but it takes mass to deaden sound, unlike for heat. My transmission tunnel isn't an area of concern at this time. No need to add a layer of lead to it.

megamax

iTrader: (9)

it DOES seem to be the tranny tunnel. I have a 1jz 5 speed swap and it's always hot as **** under my armrest. I moved the exhaust away from the tranny tunnel and it seems that didn't help at all.

t2d2

iTrader: (8)

Ok, so you've got a 1JZ 5-spd swap and HiPSI has a 6-spd swap and what I assume is a turbo, and both have excessive tranny tunnel heat issues. That's not exactly indicative of stock scenarios, however, so not particularly relevant to what I'm trying to chase down here. Now, if factory 5-spds have that issue, it could be partially relevant. But again, I'm observing crazy amounts of cabin heat with the car having not been driven all day.

t2d2

iTrader: (8)

While reading through this thread, I saw two suggestions for vented rear quarter windows like the RX-8 and E36. The examples I found were the old pop-out windows like on camper vans, which isn't much good for leaving open all the time if you value keeping your interior dry.

But it got me to thinking, what about a reverse NACA duct with a slider to close it off in cold weather? It would be the perfect opportunity to replace the quarter windows with lexan and shed some weight, although I can't imagine a duct would look all that great. There's got to be something along those lines for venting air out of the ol' greenhouse, though.

Edit: Although I'm not crazy about the look, window visors would be a cheap and easy alternative that would allow leaving the windows cracked during warm weather, without having to worry about pine needles or surprise rain showers.

bigwhite

All cars get hot inside in the summer, a 2-door car has less window area to open for cool down. Maybe a drawback to a rear wheel drive car.

t2d2

iTrader: (8)

For sure, but 167.8° @ 81° OAT is abnormal according to everything I've read. 150°+ on a 100° day is the hottest I've seen reported, but most of the info pertains to how quickly a car heats up in the sun, for child and pet safety. 120-125° is what you typically see in these cases. I did find one estimated max of 150-160° in 110° weather.

However, in researching it, I did come across something that answers the window sunshade question. The ~40° reduction claims are referring to dashboard not cabin temps. That is significant because most of the energy entering through the windows is of the variety that heats surfaces, not surrounding air. The surface temps are only loosely indicative of cabin air temps, based on short vs long wave radiation, I believe. So, there's some truth to the claims, but fairly misleading.

t2d2

iTrader: (8)

I picked up a laser thermometer today and can measure surface temps now. The sun is already down, so this is at 73° OAT with the car in the shade.

Hood/Trunk: 73-74°
Roof: 80-82° at various spots

I imagine the discrepancy will be quite a bit more in direct sun. That confirms my finger tip test findings, but the question still remains if it's a matter of the roof absorbing more heat or being hotter due to cabin venting. There should be no difference between the three horizontal panels in terms of how much sunlight is hitting them.

t2d2

iTrader: (8)

Finally, an encouraging data point to report.

5/27/15: 114.5° @ 83° OAT - 3pm (direct sun), sunroof up w/ custom shield, sun shade in window

That's an astonishing 53° cooler than basically the same OAT on 5/09, at the same time of day, with the only difference being tilting the sunroof up today. I mocked up a little template this morning, and if I'm being honest, the aesthetics are off the chart...



Tough to see in the shadows, but the sunroof is tilted up.

With all the pine trees overhead, leaving the sunroof up would result in clogged drains within a few days. Leaving the windows cracked wouldn't be as big of a deal, as it would just require more frequent vacuuming of the interior. But, I'd have to keep a vigilant eye on rain showers, so that's not a great idea, either. And I can't put up a carport due to the slope and shape of the driveway. But it occurred to me last night, why cover the entire car when I just need to cover the sunroof??

I'll need to either re-do it in fiberglass or carefully wrap the whole thing in plastic, but this definitely looks to be a winner for extended periods of parking at home in warm/hot weather. Obviously, it's not something I would take with me, but then I'm not concerned about parking under a bunch of pine trees elsewhere. And the car is parked at home more often than not.

It's held down by flexible fridge magnets, making it very easy to remove and set aside. The back edge is curved to the shape of the roof, making wind less likely to catch it. It also has the secondary benefit of keeping direct sunlight off the horizontal glass.

t2d2

iTrader: (8)

Rear view, wrapped in a clear plastic painter's drop cloth. Much classier.

SC400slide

iTrader: (11)

Neighbors probably thinking you're exceptionally odd...lol So hardtop SC's will be cooler...