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Difficulty
Credit
evilution
Mod ID
1291
Cost
For
450 Fortwo 600cc
450 Fortwo 700cc
453 Fortwo and forfour
451 Fortwo 999cc
452 Roadster 700cc
454 Forfour
450 Fortwo 700cc
453 Fortwo and forfour
451 Fortwo 999cc
452 Roadster 700cc
454 Forfour
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Since the beginning of the smart, the air conditioning gas type used was R134a.
The European Union decided that R134a was shit-in-a-can and it would single handedly destroy the world.
So they chose a replacement, made by Honeywell and was called R1234yf.
It had a far lower GWP (Global Warming Potential).
R134a has a GWP of 1430.
R1234yf has a GWP of 4.
Carbon Dioxide has a GWP of 1.
In 2011, the EU made up new rules stating that all new car platforms must use R1234yf.
The 451 had already been released so smart weren't required to adapt it to use the new type of gas.
However, Mercedes, Audi, VW and BMW refused to use R1234yf for 3 reasons.
It is less efficient.
The system has to be at a higher pressure.
R1234yf is flammable.
The new R1234yf systems have to be more robust due to the pressure,
plus it has to not leak as easily in a crash.
So, for years, Daimler pushed back against the EU despite fines and legal threats.
Because of this, even when the 453 was released, it was still using R134a gas.
There were talks of a Mercedes model being released in 2018 with R1234yf AC gas
however, the German car manufacturers are researching the use of carbon dioxide instead.
To keep the compressor running smoothly and to keep the rubber O rings from
drying out, a percentage of the air conditioning system is filled with a refrigerant oil.
This oil is normally PAG 46 (Polyalkylene Glycol) but PAO 68 (Polyalphaolefin) is compatible.
PAG 46 is thin, PAG 100 is medium, PAG 150 is thick.
*However, oddly, on the 451 Electric Drive (ED), the car recommends PAG 1234.
This oil is specially designed for AC systems running R1234yf gas but as you can also see, it runs R134a.
