Elise-Exige A/C the final answer, conclusions - LotusTalk - The Lotus Cars Community
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post #1 of 17 (permalink) Old 07-10-2016, 08:52 AM Thread Starter
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Elise-Exige A/C the final answer, conclusions

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.
https://www.lotustalk.com/forums/f313...rework-348738/

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
https://www.lotustalk.com/forums/f92/...-wa-how-26740/
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
https://www.lotustalk.com/forums/f313...-system-71031/

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.

Irreversible mods:


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
belong there.

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.

https://www.lotustalk.com/forums/atta...1&d=1467837859
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post #2 of 17 (permalink) Old 08-14-2016, 12:16 PM
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Pretty hot and very humid today. mid 90s[I measured 92 in shade 95 in sun] over 60 percent humidity

Driving west into the afternoon sun, no worries, cabin mid 70's vent down to 47, definitely running higher duty cycle, virtually no thermostat shut off.

Added a 1 ohm resistor to low fan speed circuit[total 1.54 ohms], works great, the last mile to my house, shady low speed just a nice little cool breeze, rather than blasting cold air at my knuckles

Note, use long wires when moving fan resistors, I am bruised up from trying to reach both arms in to unplug and replug wires down below the access panels. I just ty wrapped the resistor in place to keep it from banging around, will permanently mount it at some point. I bought some cheap '100 watt' resistors on amazon, they are not 100 watt, I think if I had bought 'real' 100 watt resistors i could have stuck this behind the heater controls and saved a lot of trouble.

[edit]
Oh I I noticed a fair bit of sand above my heater cover, no doubt from the flapper vent another reason I should block it off.

[exigeg2 was temp ID while password trouble was rectified]
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post #3 of 17 (permalink) Old 08-14-2016, 12:49 PM
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super hot today, 99 degrees without taking humidity into account, the AC did nothing at all in my Exige
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post #4 of 17 (permalink) Old 08-15-2016, 11:23 AM
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Friend at LOG wandered around and looked at Elises/Exiges and noted that only his car and mine had removed the recirc vent covers,it is a good start....
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post #5 of 17 (permalink) Old 08-15-2016, 01:10 PM
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Quote:
Originally Posted by exigegus View Post
Friend at LOG wandered around and looked at Elises/Exiges and noted that only his car and mine had removed the recirc vent covers,it is a good start....

Yup, between that and the heater core bypass I found the triple digit temps tolerable this weekend. This winter I may try to rewire the blower and add some insulation since now the car is cool enough to notice the heat from the pipes around the chassis


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post #6 of 17 (permalink) Old 08-15-2016, 01:42 PM
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it has occurred to me that changing the dead pedal to something that did not result in your leg being pressed up against the sill would be an effective solution. It isn't that hot[maybe 100 degrees] but with your leg pushing against it it feels worse. I may move mine further down anyway.

I think perhaps the minor efficiency improvements and airflow improvements might lower cabin temp enough that the hotspots are not that annoying.

Noticed on the drive back from LOG that the area below the windshield is like a dead zone of heat, put your hand up there and it is like putting under one of those heaters your food sits under at a restaurant.
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post #7 of 17 (permalink) Old 08-15-2016, 10:38 PM
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very interesting thread [just read your older one end to end] and also very timely as i was just about to order a new OEM condenser.

i've just finished heat insulating my cabin [including the doors, pain of a job!] and have removed the re-circ covers in the footwells. i have the oem aircon upgrade ready to fit [my car is MY06] plus forge motorsport single pass rad and twin puller fans. i also plan to use 3m crystalline before she goes back on the road.

i admire your efforts but really can't see myself going that far. even though it was 48degC here last week [120F] i don't enjoy summer motoring let alone in the elise. i will insulate some hoses, but what i'm really interested in is the condenser.

will this provide a benefit if i simply switch it for OEM? i realise some brackets are needed as well as having some a/c hoses made up. is this correct? please say yes as the vintage condenser is wayyyyy cheaper than oem and there is an a/c shop round the corner from where i keep my car!
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post #8 of 17 (permalink) Old 08-16-2016, 11:04 AM
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I believe I listed all the part numbers on the other thread. I used a build it yourself hose, but you could easily transfer the numbers to the 'regular' style hose. Vintage has a good online catalog and price list. You are already making fan brackets so all you need are the top condenser brackets, and those are not very complicated, especially since you will not have fans hanging on them.

Sealing up the fresh air door assembly is really easy, and I think worthwhile, and I think all the mods are all incremental improvements, so leaving various ones out will not ruin the overall effort.

I of course could make cover plates if anyone wanted them. A slightly stubbier receiver drier is needed for that. Honestly a sheet of poly taped in would do almost as well, but just isn't very pretty.

I would love to see how a fully 'done' system performs at 120F
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post #9 of 17 (permalink) Old 08-16-2016, 11:12 AM
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I just thought about it, the 12 inch pieces of solid line [pictured here]might be able to be eliminated and use right angle hose end fittings, and sneaking them straight back without going through the fan baffle, right probably above and below the rear radiator hose
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post #10 of 17 (permalink) Old 11-23-2016, 07:06 AM
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Wanted to make a post script WRT the heat performance. ISTR one of our Scandinavian brethren asking about improving heat performance in one of the many AC related threads

I have been driving some 32 degree F[0C] mornings and the heat works great. Warm air pretty quickly, hot to where I have to turn the fan down by the end of my 7 mile commute. This is substantially the same as my SUV heat performance so while the roads may be salted before I can test it at really cold temps, I think it will perform well.
[edit] 12 deg F[-11C] engine slow to heat up, but still good heat once up to temp. My opinion if engine can reach operating temp, you will have good heat
[edit 2] 2 deg F -16C driving with no coat
As noted above I have added a servo controlled heater valve, and added resistors to the low speed fan circuit to lower that speed. I find it a little difficult to get that perfect setting for motoring around on coolish days, so maybe the low fan speed could be modded even lower. Part of that is probably the variable sun in the windshield in such a small cabin quickly changing the heat load.

details details

comfy when hot, comfy when cold, seems somehow wrong
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Last edited by exigegus; 12-17-2016 at 12:11 PM.
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post #11 of 17 (permalink) Old 11-28-2016, 10:32 AM
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How did you do #12? I've been wanting to add an air filter to the fan as well. Is it accessible without removing the clam?
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post #12 of 17 (permalink) Old 11-28-2016, 11:05 AM
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Nothing worth doing can be done without removing the clam!

Seriously tho, one wants to do everything once the clam is off.
From the factory the fan is sandwiched between the front bulkhead and the rear recirc covers with foam donuts. Because I added the cover, I was able to remove the donuts and slip a piece of air filter foam into the space between the fan and the front bulkhead. The support web of the fan stops it from sucking into the fan, and I used very open foam so it is unlikely to become clogged.

If you have an Elise, I would put the foam in the nose, as you can get to it easily. Make some kind of bracket to hold it, or just maybe velcro it on so you can take it out and wash it. On the Exige, I added the driving lights[making holes one might be able to reach through], but also velcroed the new grille in place, so it theoretically could be removed.
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post #13 of 17 (permalink) Old 06-13-2017, 12:12 PM
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Quote:
Originally Posted by exigegus View Post
Pretty hot and very humid today. mid 90s[I measured 92 in shade 95 in sun] over 60 percent humidity

Driving west into the afternoon sun, no worries, cabin mid 70's vent down to 47, definitely running higher duty cycle, virtually no thermostat shut off.

Added a 1 ohm resistor to low fan speed circuit[total 1.54 ohms], works great, the last mile to my house, shady low speed just a nice little cool breeze, rather than blasting cold air at my knuckles

Note, use long wires when moving fan resistors, I am bruised up from trying to reach both arms in to unplug and replug wires down below the access panels. I just ty wrapped the resistor in place to keep it from banging around, will permanently mount it at some point. I bought some cheap '100 watt' resistors on amazon, they are not 100 watt, I think if I had bought 'real' 100 watt resistors i could have stuck this behind the heater controls and saved a lot of trouble.

[edit]
Oh I I noticed a fair bit of sand above my heater cover, no doubt from the flapper vent another reason I should block it off.

[exigeg2 was temp ID while password trouble was rectified]


Oh I I noticed a fair bit of sand above my heater cover, no doubt from the flapper vent another reason I should block it off.

I believe the same problem exists on my 2008 S240. Sand and dust accumulate in the cubby
storage trays on both sides. It is really annoying. How can this be averted?
I don't know if Lotus made changes in later years to the HVAC system generally
but the A/C cools the car well. I had a 2006 Elise that had terrible A/C and it eventually stopped working entirely. The shop said there must be a hole in the lines or the seals dried up due to non-use. My 2008 S240 is tinted at 5% using highest quality ceramic-nano film so that helps. I mention this because your windows are not aftermarket tinted. The factory provides
a small amount of tinting, probably 35% which is barely perceptible.
What is the first step mentioned in this post, something about recirc covers...Robert

2006 Elise ST (someone else has it now . . . )
2008 Exige S240 ST
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post #14 of 17 (permalink) Old 06-13-2017, 12:32 PM
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Forward of your and the passenger's feet there are plates riveted to the front bulkhead. They cover the recirc holes and are a stupid bodge to make up for lousy detailing during assembly. Drill the rivets out and remove the plates. This frees up a ton of recirc air to get to the system instead of outside[hot humid] air.

Later cars had a better thermostat, and of course it is possible that they did a better job assembling the system, but I kind of doubt it.


The sand is coming in the fresh air vents in the nose. If you are not taking the clam off to fix something and you don't have the driving lights[and hence a hole to reach through] you are kind of screwed in the Exige.

If you can reach in there, either cover the fresh air vents[I like them for nice weather] or put a chunk if filter foam over them to keep the sand out.

If you have the clam off for a radiator or blower resistors, please consider some of the work myself or others have done as it makes the car much more comfortable.

yesterday it was 118 inside the car by the thermometer on the passenger seat [90s outside] and it took a while to pull down, but was comfortable once on the highway.

Still struggles to keep cool in traffic, dunno if it is a weak comrpessor or TADT. If it is already cool it is fine, but if you get in a blazing car and just idle, not very good cooling
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post #15 of 17 (permalink) Old 06-13-2017, 01:44 PM
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All I did was install the electronic evap temp sensor probe and remove foot well blocking plates. I'm getting 42-44 degrees discharge air temp with 66 degrees cabin temp here in south Florida. Oh, I also added insulation between the radiator and evaporator.
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post #16 of 17 (permalink) Old 06-13-2017, 02:34 PM
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I would love for someone to do a before after of vent temps with the factory thermostat conversion. As noted in my base thread I put an adjustable thermostat in mine, and while it has definitely improved the air temp regulation, will have to update that setting it much lower than the 42 degrees is pointless as the system does not be able to pull it lower in hot weather.

As I noted at the top of this thread, removing the recirc plates is the number one improvement. Most everything else is trying to keep air temps lower or increase airflow. This will speed pull down more than lower actual air temps.

I am interested in others idle performance. My Xterra for instance will hold low 40's at 90 degrees ambient at idle, of course it has a giant compressor and is, well a truck.That the Exige doesn't, feels like a compressor issue, but is it normal or is my compressor weak?
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post #17 of 17 (permalink) Old 09-29-2017, 11:09 AM
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So I bought the Lotus thermostat service kit A120P0149S on ebay[sportscarworld in texas, good service]

I had made the wild assumption that Lotus had made a nice adjustable thermostat since it hooks into the temperature actuator

nope

it is just getting power from that.

So, if anyone is installing this update, and wants to save some trouble getting the plug off of the temperature flap actuator, it is just getting power and ground from that. No need to kill yourself, just grab power from any switched source and ground from, well any ground splice.

I will set up and test what the on/off temp on this thermostat is, but since I only get icing with my adjustable thermostat set to 35 degrees, I will stick with that with a setting more like 40 degrees
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