I just noticed there is a pipe carrying cooled refrigerant running from the compressor all the way around the engine bay via the driver side and back wall to reach the passenger side and then feeding into the cabin where the radiator/fan assembly is.

Most of the pipe run is exposed to the hot engine temps which seems counter productive to me as the refrigerant must gain some heat along the way!
Has anyone tried insulating that pipe with some rubber hose, or similar? Any issues in trying that?

I wouldn't expect much of an improvement in the Magna's case but anyway....

Some info(including pictures) about this here:


As central Vic along with the rest of aus has been having a bit of a hot time with the weather, i decided to see what could be done - especially after a local mate of mine was showing off how effectively cold his aircon system was in his EL falcon, and mine was about as effective as an eskimo fart..


With a warm/hot car, his airconditioning was chilly from the vents 20-30seconds of the car starting, and having it idle after moving it to a shady spot, within 5 minutes his cabin was in the low 20s (of a 35 degree day)

My roadster - moving it to the shade (after having been parked unavoidably in an direct sunlight area all day), the air con was cooler but not by a comfortable amount after 30 seconds, and after 2 minutes, was only just starting to be cold from the vents and with 5 minutes of running, the cabin was still uncomfortably hot.

Something had to be done!

A few minutes of reading and learnt that folk can insulate the air-conditioning lines in the engine bay..

I'm seriously questioning the common sense of some engineering decisions having run the compressor AC line right past the exhaust system, 5cm away from the headers, unshielded, uninsulated.. thats pretty dumb, and thats why i like to tweak the car..

I'd gone to a plumbing supplies shop and bought 2x 2meter lengths of pipe insualation, totalling about $10, and with 30 minutes of time and a bunch of cable ties, i'd covered up as much of the engine bay's AC lines as i could. Essentially theres only 20cm of exposed piping under the inlet manifold/alternator area that i cant physcially cover/reach.

I've covered both the feed line and return line.
My engine bay, in city driving on a hot day has reached 89 degrees (having measured it from my previous arduino project) - this is after having the car baking in the sun all day, and then driving stop start through a built up area.
On highway driving the engine bay is only 5-10 degrees above ambient.

This 89 degree bay temp will be heat-soaked into the aluminium AC lines and would be transferred into the fluid which would need to be cooled off by the condenser as well as the heat from the cabin. This just makes the condenser have to work even harder for no reason in order to try and cool..

With the insulation installed, and parked again in a hot day light area at work (still no available shade goddammit), and monday here was 42c.. Starting the car at the end of the day, aircon vents where flowing cold air within 15 seconds of being on. (keeping in mind the internal dash vent piping would have been baked by exposure the cabin heat). Within 5 minutes of driving the cabin temp was in the low 20s.

Anyone contemplating this, just do it. I'm looking forward to a highway trip to see how cold the cabin will actually get!
Also, driving with the roof down (in the 40deg day) and AC venting directed to your feet, you can feel the coolth while driving 60kph..

[.....]



Mention is made of using foil heat reflective wrap for the more heat exposed areas.

http://mx5cartalk.com/forum/viewtopic.php?f=55&t=56155

Also, see :

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1698304

Be careful to ensure you purchase the correct types of insulation that does not give off fumes if exposed to too much heat!

I imagine an auto electrical/air con regas shop will have some, or tell you where to buy from.

Stuck to this thread like a fly on a dog's doodoo. My A/C is 'reasonable' but on a very hot humid day it can take several minutes for it to feel 'comfortable', nowhere near 'chilly'
Old Toyota Hiace van you could not possibly stand the A/C on full blast for more than a few minutes no matter how hot it was outside. If you glued all the controls so they were stuck on maximum, the driver would have frostbite in an hour on a 40c day. That's how I want my aircon

Interesting idea. I had a look under the bonnet and the biggest advantage would be from insulating the return line (larger pipe) around the front exhaust manifold. You could also insulate the rest of the return line as this comes out of the evaporator quite cold and would be absorbing a lot heat from the engine bay. The high pressure line (smaller pipe) does not come that close the exhaust or any sources of heat. It would be worth checking the temperature of this line after the condensor, chances are it is hotter than the engine bay temp and dissapating heat. If this is the case then insulting it will make the system less efficient. The line from the compressor to condensor would definetly be hotter than the engine bay temps so this one should not insulated.

Very good info and good points in this thread! I'm going to go ahead and try something because i think it will make a difference which may translate into better economy and faster cooling.

Personally I don't think it would make a difference as my A/C piping can have frost on it during the middle of summer with the engine idling and thermos on.. Out of the vents is around 4 degrees which is about as cold as it will get.. If anyone does this and it works I'd be happy to be proven wrong.. On a side note my problem with the magna A/C is not the temp but the actual air flow.. I drive a 2014 sprinter and the fan is like having your head out the window at 100 where as the Magnas fan just has a gentle waft on high

If your pipe has frost on it in summer then its not working properly. There should never be any frost on airconditioning pipes. They should sweat, not frost

Jarod, I think if anything frost signifies that it is working really well?
ie, the freon is below freezing temperatures hence the frost

It's working too well. There is a temp sensor in the evaporator unit under the dash that cuts the compressor out when the temp gets low. Sounds like it is not working and the compressor keeps running.

Many years ago, my wife's TM sedan hada problem with the A/C compressor clutch. It used to engage by itself, even in winter. End result - the whole evaprator coils generated lots of condensation and that then froze on the evaporator coils. No air flow at all, including the heater. In winter, that is not funny - dangerous in fact because we had no demister. We knew when it was going to happen because the inner fan would blow snow out the fresh air vents.

I'm not saying it it completely frozen, parts of it have frost every now and again not all the time.. My A/C was serviced 12 months ago and is working fine

I'm an air conditioning mechanic by trade...not an auto electrician with a car ac ticket.

Frost at any time on a suction line is not a sign it's working fine.it actually means the opposite.

Refrigerant charge may be wrong.
Blocked drier
Blocked coil
Insufficient airflow
A few other things can cause frost too but these are common issues.

This is a little off subject from the topic but I had the condenser replaced 2 years ago and the air con regassed and there was too much refrigerant added so it was cutting in and out ever 3-10 seconds which wasn't long enough to cool down, I had some taken out which fixed it but if your saying there should never be ice then I'm guessing there's still too much.. It works perfectly, ice cold and cools down in seconds so I assumed it was fine

yeah I wouldn't be worring too much that its icing up occasionally. its icing up because its too low on refrigerant not too high in your circumstance.

its not a major issue that's its occasionally frosting up. if its working fine then don't worry too much about it.

hose down the condenser coil occasionally keep it clean and it will make life easier for the compressor

Below is a quick 101 on the gas flow, as you will see the cold part is on its way BACK to the compressor where it will be re heated as it is compressed, insulating the low pressure line which is the one which is the cold one will do nothing to improve efficiency at all as when you compress a gas it heats up.

Below is a quick 101 on the gas flow, as you will see the cold part is on its way BACK to the compressor where it will be re heated as it is compressed, insulating the low pressure line which is the one which is the cold one will do nothing to improve efficiency at all as when you compress a gas it heats up.

everything is right except the insulating part, insulating it will help. it allows the superheat to stay in a range which is optimal. however I wouldn't bother at it will probably decay with the heat generated by the under bonnet temps.

If the vapour picks up heat from the engine bay it will superheat further and thus expand. This means the compressor will be compressing less mass of refrigerant . Also it will be coming out of the compressor at a higher temperature requiring the condensor to remove more heat before it will liquify. I'm sure the engineers allowed for this in their design by oversizing the condensor to remove this extra heat and as well as a larger compressor. Maybe the exposed pipe near the exhaust was deliberate to ensure that any liquid would be vapourised before entering the compressor.

Below is a quick 101 on the gas flow, as you will see the cold part is on its way BACK to the compressor where it will be re heated as it is compressed, insulating the low pressure line which is the one which is the cold one will do nothing to improve efficiency at all as when you compress a gas it heats up.
Hang on, I want to try insulating the cold pipe coming from the expansion valve (4 in the diagram) to the evaporator blower inlet at the firewall (5). The idea is to reduce ambient heating of the low pressure liquid before its entered the cabin.

I assumed that the expansion valve is the thing sitting near the driver side engine mount inline with the low pressure pipe running around the rear of the engine to the passenger side firewall connection... or is the expansion valve located somewhere else?

expansion valve would be located near the evaporator in the cabin of the car. it will vaguely look like a 'T' if your not sure what it looks like.

insulate the suction line and it should improve, I don't think air con insulation will last too long under the bonnet. my triton is worse than my magna and im considering experimenting with wrapping the suction line in ac insulation then I would also wrap it in that exhaust wrap stuff..