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Discussion Starter #1
I admit it, it has taken me time to come terms with many of the difficult aspects of my Elise, but I have done so mostly and just love the car while not having any illusions about what it asks for.

A couple of things still look weak however. One is the crap HVAC system. The fan can't seem to move enough air to matter much.

But the really big bugbear is the hot air from the radiator vents flowing out of the radiator vents, over and around the windscreen and tumbling into the cabin.

This is noticeable when the ambient temps are above 75-80degrees, and gets really unpleasant. On longer trips, it induces fatigue and dehydration pretty quickly, and its just annoying and unpleasant on shorter trips, and makes me wish I'd just taken the Miata or the sedan.

The HVAC hasn't a hope in hell to counter this, what with all the heat coming into the cabin from the radiator plumbing in sills as well, in addition to the hot air exhausted by the radiator tumbling into the cabin over the windscreen.

I keep having visions of reconfiguring the radiator so that the hot air goes out the sides or something instead of pouring into the cabin over and around the windshield

Do any of you share this annoyance? Any words of wisdom for me?
 

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I noticed the thin layer of hot air coming over the top of the windscreen one night while driving in ~50F ambient temperatures... but then, it was 50F outside so the warm air was welcome :rolleyes:

It doesn't bother me TADTS

Don't forget, the design adds downforce for better handling. You don't want to muck with it.
 

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TADTS also it will come through the shaped hole in the mirror.
 

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I admit it, it has taken me time to come terms with many of the difficult aspects of my Elise, but I have done so mostly and just love the car while not having any illusions about what it asks for.

A couple of things still look weak however. One is the crap HVAC system. The fan can't seem to move enough air to matter much.

But the really big bugbear is the hot air from the radiator vents flowing out of the radiator vents, over and around the windscreen and tumbling into the cabin.

This is noticeable when the ambient temps are above 75-80degrees, and gets really unpleasant. On longer trips, it induces fatigue and dehydration pretty quickly, and its just annoying and unpleasant on shorter trips, and makes me wish I'd just taken the Miata or the sedan.

The HVAC hasn't a hope in hell to counter this, what with all the heat coming into the cabin from the radiator plumbing in sills as well, in addition to the hot air exhausted by the radiator tumbling into the cabin over the windscreen.

I keep having visions of reconfiguring the radiator so that the hot air goes out the sides or something instead of pouring into the cabin over and around the windshield

Do any of you share this annoyance? Any words of wisdom for me?
yes. i too dream of diverting the flow. may as well remove the a/c and save some weight for all the good it does
 

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Don't know where you live, but Tonywa's heater core bypass might help (search forum). The idea is to prevent heat soak from the condenser. You can toggle it with a switch.

Another possibility is to bypass the heater core altogether, also mentioned somewhere on this forum. No toggle on this mod.

I think these provide some improvement, but not a full solution.
 

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yeah, i've learned the hard way that running the AC on a hot day with the top off only makes matters worse becuase the heat from the radiators is more efficient at contibuting to cabin temps than the AC... which is a fact of physics... it's just the side effect that the down force producing design pumps the heat right in front of the wind shield that lets the driver know about this little fact of physics.. ops!

Top on windows up, the AC is not too bad as long as the interior isn't already baking hot.
 

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Discussion Starter #8
It seems to me that Lotus engineers designed the car for crappy English weather where the top is often on and it rarely gets hot enough for this problem to show.

For myself, I am convertible die hard and putting the top on to keep radiator heat from spilling in the cabin is a major disappointment.

Oh well.
 

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There's a device from Lotus that will work wonders for your overheating problem. It's called a Lotus Sports Cap. Right before your drive, you fill it with ice cubes and put it on your head.
 

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I
it induces fatigue and dehydration pretty quickly, and its just annoying and unpleasant on shorter trips, and makes me wish I'd just taken the Miata or the sedan.

The HVAC hasn't a hope in hell to counter this, what with all the heat coming into the cabin from the radiator plumbing in sills as well, in addition to the hot air exhausted by the radiator tumbling into the cabin over the windscreen.

Do any of you share this annoyance? Any words of wisdom for me?
No

I have driven my car several times to Palm Springs in 113 degree weather with the top off and with the soft top on, and have never become dehydrated or fatigued by the heat coming off the radiator. I have also been stuck in traffic for over 2 hours in 105 degree heat of the san fernando valley and did not notice what you are describing.

Are you saying you are attempting to run the AC with the top off??? If so that is not going to work,ever . The AC unit is tiny and light weight, and it works very well for me with the soft top on, windows up , and the recirculate button activated. This is the key, if you don't recirc, the wee little compressor will be in a constant losing battle. If you have recirculate on, then the cabin will be very comfortable 70 or so even on 113 degree days with a passenger. This is not a Mercedes with zone environment control, the AC is an afterthought, it is not a car designed for comfort, it is a street legal track car.
 

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I now have my A/C working great. My objective was to insulate the cabin from outside heat sources thereby enabling the undersized A/C system to cope better.
I installed the latest technology window film which is unlike any other film. Insulated the side sills and front firewall.
Installed a better thermostat on the evaporator coil.
 

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Discussion Starter #13
No

I have driven my car several times to Palm Springs in 113 degree weather with the top off and with the soft top on, and have never become dehydrated or fatigued by the heat coming off the radiator. I have also been stuck in traffic for over 2 hours in 105 degree heat of the san fernando valley and did not notice what you are describing.

Are you saying you are attempting to run the AC with the top off???
I tried the A/C to see if it does anything useful with the top off, but I am talking about conditions with tops off, window down and the A/C off.

I would like hot air off the radiator to not come into the cabin when the windows are down and the soft top is off in 80 degree plus weather

I would also like the A/C to work effectively in 90 degree plus heat when the top is on and the windows are up.

You are very lucky from my perspective if you don't have an issue on either point.
 

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I tried the A/C to see if it does anything useful with the top off, but I am talking about conditions with tops off, window down and the A/C off.

I would like hot air off the radiator to not come into the cabin when the windows are down and the soft top is off in 80 degree plus weather

I would also like the A/C to work effectively in 90 degree plus heat when the top is on and the windows are up.

You are very lucky from my perspective if you don't have an issue on either point.
You are just driving too slow Harbir...:D

I noticed ALOT of heat rising from the front of the car (obviously), but since I don't ever take the top off I haven't experienced this problem. Definitely a difficult issue to solve for the Elise owners, however.
 

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I tried the A/C to see if it does anything useful with the top off, but I am talking about conditions with tops off, window down and the A/C off.
Keep the windows up. Rolling them down is not a good idea as you get much more buffetting from the wind and a lot more hot air from the road getting into the car.

With the side-windows up you should find little hot air from the rad getting into the cabin.

Bye, Arno.
 

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Keep the windows up. Rolling them down is not a good idea as you get much more buffetting from the wind and a lot more hot air from the road getting into the car.

With the side-windows up you should find little hot air from the rad getting into the cabin.

Bye, Arno.
That's how I drive when it's hot out (over 100 right now :panic: ). I haven't had the top on the car in a few months and it's been fine. I mostly drive it at night though to go meet up with friends.

Also, the speed you're moving at seems to play a big role in how much of the hot air comes into the cabin. I seem to notice it the most ~50-60 mph...
 

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For myself, I am convertible die hard and putting the top on to keep radiator heat from spilling in the cabin is a major disappointment.
I'm a drop-top person too. Like others here, I'd recommend leaving the windows up. It reduces buffeting a lot, and reduces the radiator airflow into the cabin.

There is a TSB AC fix for earlier cars. You're a more recent member on this forum, and it's not possible to tell what year your car is, so dunno if the AC fix is applicable to your car. It is well worth checking though.

FWIW, I've always had strong AC in my '05, and I run all summer long with top off, windows up or down according to the speeds I'm driving, and with the AC on. I get a little pool of cool air inside the car under most circumstances and the face-level vents keep me cool at stops. :cool:
 

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the heat flowing over the windshield doesn't happen at a constant rate for me. once in a while I will feel hot air come inside.
 

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Discussion Starter #19 (Edited)
Well, I've decided not to drive my Elise if its over 85°F.

its been upto 104°F today and was damn hot and humid yesterday as well and the day before and I've been experimenting.

When its above 85°F, there is about 1" hot airflow layer around the cabin that pours into cabin whenever the car is moving. When I come to a stop, the "sitting in front of a blast furnance" feeling suddenly stops. When in motion, the hot layer spills in towards the rear of the cabin then swirls forward.

I did back to back drives in my '91 miata and '06 Elise, and in exactly the same temp, humidity, sunlight levels, the Elise cooks me, while the air flow feels cool in the Miata.

With the tops up, the Miata A/C is super comfy and chilly, the Elise is just about habitable. The air flow from the vents is weak (low volume, low velocity), and not particularly cool.

the windows up, top off thing didn't work for me. The hot air still tumbles in over the top of the windscreen.

I am going to harass the dealer about the A/C, but I'm just going to drive the miata on hot days. The discomfort is not worth it.

If you guys aren't suffering my issue, you're real lucky.

me, I am just looking forward to driving my Miata more, since its been getting neglected since the Elise came.
 

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harbir,

I have an Exige and I know what your talking about. When I drive with both windows down on a warm day ( like today in Ohio) the amount of heat that funnels through the holes on the side mounted mirrors is really something. It's like an F1 aerodynamicist spent hours in the wind tunnel to make the radiator heat flow through those holes and into the cabin on purpose! I really don't mind though, this is a raw car any way you look at it - that's why I love it!
 
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