R-134a upgrade

[Dan B]

I want to upgrade the York to a Sanden compressor, and do the R-134a update at the same time. Has anyone done this, and do you know what model of Sanden will work easiest? i would like to salvage one if possible to save $$. I was told that the TR or TRS series of Sanden was better because the rotary compressor causes less drag. Does anybody know if that is right?

Thanks,

Dan Blackwood
South Charleston, WV

80 TR7
66 TR4AIRS

[Dan B]

Ok, so far I have found conversions with a bracket to fit a SD508 compressor to the car. The mounting holes are different, so the bracket is needed. The TR series, however, has the mounting holes in similar configuration to the York. The only TR/TRS compressors I have seen were from Hondas and Chryslers and have serpentine pulleys. If the spacing on the mount holes would match the York mount, seem to me you could change the pulley and clutch.

[FI Spyder]

Keep us posted. I have all the original stuff in place (no belt) for originality sake at car shows. No freon in there as I had hoses off for pulling heater. Don't need it here but there are people in states and Oz that would so would interested in your findings.

TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra

[Ferris]

Dan - The Sanden compressor will push the refrigerant around just fine. But, there are a couple of other things you should know when doing an R134a conversion.

First are the seals. If your car still has its original rubber o-ring seals in the various hose connections, they will need to be changed to neoprene types to avoid leaks. R134a will creep right by them.

Second is oil. R12 used a mineral type oil which R134a will not pick up and carry. Popular opinion is that the mineral oil does no harm once converted - it just settles at the bottom of the condenser, evaporator, and drier - but it does no good either. You'll need to add PAG oil to protect the compressor and expansion valve.

Last is efficiency loss. R12 is a more efficient refrigerant in cars than R134a is, owing to its lower boiling point. If you look at the pressure / temperature curve of both, R134a is 10-15 psi higher at every temp point a car will see. Because of this, newer cars designed to use it have bigger parts - condensers and evaporators in particular. Head pressure is often much higher, but the Sanden can take it. Higher suction pressures, though, equal higher evaporator temp, and warmer air from the ducts.

Fortunately, a TR7 cabin is so small, and the evaporator is so close to you, that cooling should still be acceptable. But, with the original parts, it won't be quite as good as R12.

The conversions I have done have had mixed results. Rolls Royces, for example, work great after conversion, since the AC parts in them could cool your house. Jaguars - terrible. Their AC systems are marginal on R12 already, and don't work worth a flip on R134a.

Like FI Spyder said, I'd be keen to know how it turns out.

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It's true! Bob IS my uncle!

Kevin Anderson
(2)1980 TR7 DHC
1990 Jaguar XJ40