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Custom upgraded components when converting an R-12 system to R-134a?

bond007 on Mon July 14, 2008 6:07 PM User is offline

Year: 1993
Make: Mazda
Model: RX-7
Engine Size: 1300cc
Refrigerant Type: R-12 -> R-134a

Background:
I am attempting to improve upon the components of an existing R-12 system in a '93 Mazda RX-7 so that I have a conversion to R-134a that works as good as (preferably better) than the original.

I am not looking at a bolt-in solution as I can custom-fabricate most of it and outsource what requires expensive tools.

The original specs (per Mazda factory manual) state that the R-12 system:

Dissipates 3900 kcal/hour
Nippondenso TV14C compressor, rotary, 8.42 cubic inches/revolution
Original condenser size: 23" x 10.5" x 0.75", 25 horizontal tubes
Receiver/Dryer: factory installed 16.7 cu/in; dealer installed A/C is 20.75 cu/in but has different fittings

Questions:
1) Is there any major issue using the TV14C compressor with R134a?
(As far as I know, in 1995, all of this model vehicle became equipped with R134a and as best as I can tell, I do not believe they changed the compressor. I believe that the condenser was changed, though to something with a higher density, since the original vehicle configuration didn't permit installing a larger one.

2) Is there any reason I should entertain trying to use a different compressor, i.e. is it a weak link in terms of the the system operating well on R134a based on the specifications listed above or any specific issues with this compressor/type?

As best as I know, the condenser was changed in 1995 for R-134a (it is believed to be a higher density, I'm still researching this). In my case, it sounds like a "Universal Parallel Flow Condensers" would do the trick in terms of being optimal for R-134a as well as being more flexible for my revised plumbing (mostly why I would prefer to change condensers).

3) How big a condenser should I fit?

I have the ability to install a much larger condenser than was originally equipped in the vehicle. The overall dimensions I could go up to are in the range of 26" wide x 18" tall and I could probably fit something around 1" thick. My gut reaction is to go as big as I can (that is my philosophy on radiators/oil coolers, since they have thermostats to regulate things if cooling is "too good")? More refrigerant capacity and surface area _should_ improve the cooling but does going larger cause a problem I'm not aware of (aside from requiring more freon and having to slowly/carefully fill it the first time to determine the new capacity)?

Anyhow, those are my initial questions. I'll probably have some more specific plumbing questions once I figure out what I'm going to end up installing.

brickmason on Tue July 15, 2008 1:38 PM User is offline

Why not just keep it R-12? If your not certified to buy it, you can take an online test for around $20.00 to become certified to buy it as it is a lot cheaper than it was a few years ago when R-134a replaced it.

Bottom line being that it would actually be cheaper to go this route than to spend all the time and money to convert to R-134a and not get any better performance. Just fix the leak/leaks, replace the drier, expansion device, add the neccesary amount of oil, vacuum and refill with the factory reccomended R-12.

Just my opinion!!!


-------------------------
Just another brick in the wall

Had a little mule I fed him castor oil and every time he jumped the fence he fertilized the soil

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