So I think, combined with the previous efforts of other LT'ers I have the 'final answer' on how to make the Elise/Exige AC
[and heat] function at a high level.
These mods keep the cabin temp to 70-72 degrees at 92 degrees in the sun, on the highway. It is still not at 100 percent duty cycle, so I believe it will maintain that to the mid 90's, and have very reason to believe that it will be well over 100 before it will fail to do its job[I have found that 80 degrees and dehumidified is my marker line in houses with undersized AC].
Mods to my AC system, in somewhat order of importance.
1]Removed recirc vent covers
2]Tony Wa bypass mod
3]Installed heater box cover plate[detailed in my previous posting]
4]properly gasketed fresh air inlet
5]replaced factory Lotus AC condenser with vintage air unit that is the same size, but is not upside down
6]insulated per previous AC postings, in addition insulated pedal box and heater diverter assy
7]removed gasket from front facing fan inlet
8]cut holes in passenger side recirc plenum to allow both sides of fan recirc air
9]Added extra holes for recirc air[they will still hide behind the now removed covers]
10]sealed all openings and seams on the heater box and the diverter assembly[box above the passengers knees]
11]moved heater fan resistors out of the air flow, unlike factory update which inexplicably further blocks air flow.
12] added a filter to the fresh air side of the fan. The heater box was full of sand, and this cannot be a good thing
13]permanently propped open the heater flap
14]replaced corrugated air trunk with smooth silicone hose.
15]insulated ac lines in the vicinity of the radiator hose
notes on above:
i did hot insulate inside the cockpit, or tint the windows.
items 3,7,8,9: all are related and work together and allow item 4 to make a difference. From the factory the heater/ac unit is outside of the car,
item 3 effectively moves the heater into the passenger cabin, thus air leaking out of the heater box is inside the car, air
leaking into it is from inside the car. The AC is no longer overwhelmed with hot humid outside air.
item 5: It looks to me like the Series one and series two rover engined cars had the radiator[and consequently the condenser] totally horizontal. Probably adding Federal crash structure made
them move it to slightly sloped. They either did not consider the difference important or did not care, but I think it is. A R134A does not seem to create liquid as easily as the old ones, thus
you are pretty much always dealing with a liquidy gas mixture. With a standard vertical condenser, the hot gas always comes in the top, and as it cools the liquid can fall by gravity towards the lower cold side and
head to the dryer and the evaporator. Totally horizontal is not ideal, as some hot gas is no doubt streaming by and reducing the efficiency but
it is what it is. Totally upside down simply won't work, you could probably get some coolish air out, but the easy path is for hot gas to bypass right
through the condenser. Our original setup is just poor. Liquid must fight gravity to get out of the condenser, and hot gas is trying to move vertically
up towards the outlet, as physics tells us it will. My condenser looked a little beat up, so I felt replacing it was a good idea, but I think with care the brackets could be removed
and the stock condenser mounted correctly, needing only 2 new lines and moving the holes in the crash structure to align with the now moved hose locations.
very few. I think long and hard before doing things that cannot be undone. Obviously doesn't always stop me, but I think about it.
a]The upper condenser line was too difficult to bend enough to get out the factory hole, so I used a hole saw to enlarge it at most a hole diameter.
A factory could bend tighter radius to allow this without a mod, or a different flexible hose setup[a 45 deg at the condenser then a 135 deg back]
b]I added a pair of holes that some add to remove the front condenser bolts. I happened to have some nice black plastic plugs that pop in and look like they
c]Cut about a 2 x 4 inch hole in the black plastic recirc plenum, passenger side. To allow the front side of the fan to get recirc air.
d] there are four factory hole patterns drilled in the alloy panel ahead of your feet for recirc air. I made a fixture and drilled an additional set of holes on both sides of each pattern.
This brings the vent area from just under 18 square inches to just about 22 square inches to allow for the increased airflow to the other side of the fan.
a,b,c are totally invisible when the car is assembled, you pretty much have to have the clam off.
d, If you were to replace the covers it is invisible. That made it acceptable to me, others may differ.
What would I do differently?
Eliminate both black plastic recirc plenums. They no longer serve any purpose. I was hedging in case my heater cover did not work. It does, they are not needed.
I used 100 watt resistors for the fan with a heatsink. They do not get hot in service, and I would simply screw them to the panel making access easier.
Seal the rubber flap on the fresh air assembly. I don't think it serves any purpose now, and it is really hard to detail correctly
Probably wouldn't do the air trunking in silicone, flow increase is marginal, and it is hard to work with. I would probably use a more smooth bore flexible hose.
What do I still want to do?
Lower the fan speeds in low and med. They are too close together and now I have to bleed some heat in on moderate days or my hands freeze. Talk about your first world problems....
I think 1 ohm and .33 ohms will make them better.
move the thermostat sensor further away from the evaporator. It cycles 44 degrees[compressor on] to 51 degrees[compressor off]. You get a little of that damp air smell as it warms up.
I would like to see 40-47 or so.
I do not think it is a problem anymore, and in high, I don't think you will see frost with vent temps of 39 degrees. I am going to go in there and move it back to where it was originally.
I am curious if the fan wuld run faster on 12 volts right from the Exige's nearby battery posts, I may try that, in that case a relay doing just that would be easy, and perhaps allow me to
turn off the thermostat when the fan is on high.
Downsides......uhhhh..........the fan is much louder...........that could be fixed with a foam block in front of the fan to block sound, or perhaps reinstalling the aluminum recirc plates on
spacers to block sound.
As a note to our Norwegian and Swedish friends, I think this mod is just as relevant to heat, particularly item 13 above, allowing full air from the heater vent as well as the face vents. If your engine is
warm enough to make heat, I think this will keep you warm.