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Even the partial passenger side plate restricts air appreciably. It makes sense to cut all the way around the perforated air return rather than cut across holes, leaving jagged edges.
Michael
I experimented with both finishing plates on, both off ..... no discernable increase in air flow, that little fan can only do so much.
 

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Discussion Starter #22 (Edited)
407: I can't comment on airflow because I didn't attempt to measure it. What I can say is:

1) The value in doing this is to improve recirculation. If you consider that 75% of the overall perforated area (used for recirc air from the drivers compartment) is blocked, this has to help.
2) If you aren't running the AC in recirc mode, then you are still sucking in a lot of hot outside air

3) On my ride home yesterday, it was full sun, 95 degrees, 50% humidity with a THI of 105 (as per WeatherBug locally). Last year, on similar days, I would be warm with a level of sweat on my back by the time I go home. Yesterday, within minutes, I was nearly cold. I stopped, rolled the windows down while I went in the store to bring the temperature back up. Got in the car and again, within minutes, was nearly cold. Keep in mind that I have only full blower speed. What I didn't do was try to see the differential of with and without running recirc mode.

So, my sweaty butt seat of the pants answer is the increased recirc airflow makes a big difference. Your mileage may vary!
 

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Discussion Starter #23
Thank you yellowvert for trying this and it being succesful and blacksix for the idea and sirLotus for help. Then also documenting and sharing with us.

On pic 1 there's the solid alum panel thats held by the 4 rivets.
If one was to cut the opening smaller; an area within the 4 rivets just along the perforated air holes in pic 3, then maybe the solid alum panel can just be riveted back in place, or use some type of screw/bolt for easier access in the future? Then discard the piece with ventilated holes? Is this possible, and any harm in discarding the cut out piece with perforactions
You make a good point. Had I cut in enough to allow me to use the same size panel, it probably would have been enough to allow one to re-rivet in the perf panel and then maybe add some small aluminum trim to clean it up. I will tell you that when you are standing on your head trying to get one hand back there (and then add a second little person later on to help crimp), the more space the better. But cutting it 1/2 on each side wouldn't have mattered. I think cutting it 1/2 on top and bottom WOULD have mattered. Again, in retrospect, cutting just a little less off top and bottom might work.

Sorry, thinking as going...if you cut it narrower (less off sides) you could re-rivet. I'd generally stick with all the height possible because you would need to add the trim on all 4 sides. I just don't think its reasonable to think you could cut it so clean and straight that you wouldn't notice. Lord knows I didn't but I realized instantly that that wasn't something I could do. Maybe wrong tool?
 

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I experimented with both finishing plates on, both off ..... no discernable increase in air flow, that little fan can only do so much.
Airflow meter in the dash vents and proved the airflow was appreciably higher. The fan is not undersized, rather the ducts restrict the flow.
COCKPIT VENT AIRFLOW ................RECIRC. OFF................RECIRC. ON
.................................................. ....(Outside vents open)...........(Outside vents closed)
Footwell vent closed (normal)----------27mV........................16mV
Footwell vent open (modified)----------50mV .......................45mV
There is a greater airflow at the vents with the outside air intakes open, but that air, in the A/C mode, is warm, unconditioned and could result in a higher cockpit vent temperature.Note – Higher voltage (mV) equals greater air flow

Michael
 

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it looks clean, What did you connect the red wire to? how did you route it? thanks
Thanks, route the wire from the AC switch panel (requires drilling one hole behind the switch panel) over to the passenger side cubby (remove the cover) and you can see a space where the wire can be fed down and then forward along the underside of the dash and push the wire thru to the front side of the firewall via the main harness grommet. There is room to squeeze the wire between the firewall and the fan housing foam grommet.
Go back in the driver footwell and strip the wire, put the connectors on, install finishing plate.
 

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Fantastic writeup! I really enjoyed reading it.

I had two thoughts:

1) This could prove really useful in the future, and
2) I pray to God I won't need to perform this fix.

Also the comment about your "favorite little person" was priceless. I always need someone like that whenever I work on a car. Usually it is my daughter.
 

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I will tell you that when you are standing on your head trying to get one hand back there (and then add a second little person later on to help crimp), the more space the better. But cutting it 1/2 on each side wouldn't have mattered. I think cutting it 1/2 on top and bottom WOULD have mattered. Again, in retrospect, cutting just a little less off top and bottom might work.

Sorry, thinking as going...if you cut it narrower (less off sides) you could re-rivet. I'd generally stick with all the height possible because you would need to add the trim on all 4 sides. I just don't think its reasonable to think you could cut it so clean and straight that you wouldn't notice. Lord knows I didn't but I realized instantly that that wasn't something I could do. Maybe wrong tool?
Very true, I wasn't in the lotus position + another person there with me-eek- Once again great work and clear photos in such a tight space!

Thanks, route the wire from the AC switch panel (requires drilling one hole behind the switch panel) over to the passenger side cubby (remove the cover) and you can see a space where the wire can be fed down and then forward along the underside of the dash and push the wire thru to the front side of the firewall via the main harness grommet. There is room to squeeze the wire between the firewall and the fan housing foam grommet.
Go back in the driver footwell and strip the wire, put the connectors on, install finishing plate.
this really helps, ty
 

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Discussion Starter #30
Michael, but the "yeah but" is....how do I get the wire up to the radio from the cockpit? I was so tired (and still sore!) I didn't look too much up there but I reach around and didn't feel any obvious opening. Maybe its through the passenger side cubby?

And one of these days soon, I'll be calling to chat about the solid state controller, etc. I would like to get multiple speeds back. When I do that, the car won't be "original" but it will be "fully functioning" - and arguably better (if nothing else due to your opening of the recirc mod).

Can you explain why Lotus limited recirculation in the first place? I haven't been able to figure that one out.
 

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Michael, but the "yeah but" is....how do I get the wire up to the radio from the cockpit? I was so tired (and still sore!) I didn't look too much up there but I reach around and didn't feel any obvious opening. Maybe its through the passenger side cubby?

And one of these days soon, I'll be calling to chat about the solid state controller, etc. I would like to get multiple speeds back. When I do that, the car won't be "original" but it will be "fully functioning" - and arguably better (if nothing else due to your opening of the recirc mod).

Can you explain why Lotus limited recirculation in the first place? I haven't been able to figure that one out.
Scott, I Just discovered that there is no access from the radio slot to the wiring grommet that goes to the HVAC console.
There are two reasons why the airflow is restricted;
1) I believe the ducts to each cabin discharge vents are too small.
2) The footwell returns were blocked because on a cool day with the heater/fan off there would be a backflow of cold air through the returns. Apparently owners were complaining and Lotus used this method to address it. The disadvantage is that it also inhibits the airflow in, thereby restricting the flow out of the cabin discharge vents
Michael
 

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Discussion Starter #32
Cool day....huh? I'm a looooong way from having to worry about that, as are you, my friend.

Not happy to hear there is no opening....there has to be a way!
 

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Re floor vent covers

Many years ago I had a couple of corvairs and in the engine department they had a plate (cover?) the was removed in the summer and added in the winter to adjust the cooling of the engine. Couldn't the lotus interior covers have the pop riviets drilled out and re-attached with fasterners so that they could be removed or reinstalled as needed? Just a thought.
 

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Discussion Starter #35
Been there done that. Sadly... you must drill a hole. fortunately the switch panel covers it.
407: I don't mind drilling a hole but have no idea where to do this. I've got a wire coming from the big vent hole, behind the gas peddle and up to through the passenger compartment, then all 9 feet of wire are spooled and sitting in the package tray. Can you provide some direction??
 

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Just exactly how PITA is it to pull the clam? I think I'd rather do that than try to flex around in the car to run wiring!
 

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Scott, I Just discovered that there is no access from the radio slot to the wiring grommet that goes to the HVAC console.
There are two reasons why the airflow is restricted;
1) I believe the ducts to each cabin discharge vents are too small.
2) The footwell returns were blocked because on a cool day with the heater/fan off there would be a backflow of cold air through the returns. Apparently owners were complaining and Lotus used this method to address it. The disadvantage is that it also inhibits the airflow in, thereby restricting the flow out of the cabin discharge vents
Michael
Just a quick point of correction...there is access between the radio slot and the HVAC grommet--that is how I wired my ipod adapter. On mine there was a plastic panel taped in place that hid the grommet from the radio slot, but it comes right out.
 

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Just a quick point of correction...there is access between the radio slot and the HVAC grommet--that is how I wired my ipod adapter. On mine there was a plastic panel taped in place that hid the grommet from the radio slot, but it comes right out.
Thanks for that information.
Michael
 

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I will tell you that when you are standing on your head trying to get one hand back there (and then add a second little person later on to help crimp), the more space the better.
I didn't fully appreciate how confined that area is until this morning. I had my mat out and was washing and vacuuming the area and I could barely even reach the aluminum front panel. To think that you also reached behind it to grab wires...all I can say is WOW.:up:
 

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I didn't fully appreciate how confined that area is until this morning. I had my mat out and was washing and vacuuming the area and I could barely even reach the aluminum front panel. To think that you also reached behind it to grab wires...all I can say is WOW.:up:
From someone so flexible, that is suprising ;)
Michael
 
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