Thread: Aircon pump capacity?

... and 'what' gas you put in t
Failing that, one of the hydrocarbon equivalents, such as Esanty ER-12 or Hychill's "12" gas. Both of which may be better than the original R-12 in terms of cooling capacity and engine loading. Certainly superior to Testicular Cancer, a.k.a. R-134a

Yes it does. But I can apply the appropriate gas Enthalpy chart to account for the gas type.

My main aim is to work out how many kW of cooling the system was designed around.

[ame]http://www.sanden.com/objects/SD_Service_Guide_Rev.2.pdf[/ame]


Page 4 suggests 9 ci displacement

How did I do that...should have been a link

So I've crunched some numbers on three different systems. But it looks like I need The R12 operating pressures to get the final puzzle piece down.

Valeo's TM16 compressor (R134a, 163cc/rev) gave some results using 48C condensor temp, -12C evaporator temp, 10C suction and resulting COP and power ratings.

Benchmark R134a.
15.2/0.18MPa pressures.
COP cooling 1.82
3.4kW drive power.
Cooling Capacity 6.2 kW.
Heat shed through condensor 9.6kW.

Here's the kicker. Using R12 with the 9ci compressor I'm showing slightly worse efficiency (COP 1.79 vs 1.82) and correspondingly lower heat transfer.
Now that's contrary to all the public opinions. However I found this: AIR CONDITIONING HELP HOME PAGE,a/c,ac,air,air conditioning,barrier hose,Behr,Bosch,compressor,compressors,condensers, condenser,condensors,drier,driers,dryers,evaporato r,evaporators,freon,Griffiths,improvements,Kuehl,N ippondenso,Porsche,r12,r134a,San

Originally Posted by griffiths

Actually R134a is more efficient . Pound for pound R134a is a more efficient refrigerant than R12, however it runs at higher pressures in some aspects and therefore requires more effective condensing.

Anyway, here are my results using the same pressures, subcooling, superheat and compressor efficiency:

R12 but slightly smaller compressor.
COP cooling 1.79
Compressor power draw 3.3kW.
Cooling capacity 5.9kW.
Heat shed through condensor: 9.6kW.

Hmmm. Interesting.

So I decided to run Hychill using the same pressures as R134a.
COP 1.69
Compressor power 3.8kW
Capacity 6.44kW
Heat shed: 10.3kW.

These numbers are a bit fuzzy, some of the charts I have are very hard to read (particularly R12) and trying to keep operating pressures/temps equal is likely not a fair fight.
The compression ratio for each gas density however did come out about 7:1.

But either way it looks like the systems are designed for cooling at idle (2-3kW) and have plenty of spare capacity at 2000rpm so will just spend more and more time clutched out as the evaporator inside can't keep up.

Upgrading the classic to a parallel flow condensor is the easy part. Not so sure about upgrading the evaporator in the dash.

Wot you mean is... you need colder and better air-con than what the RR engineers (to use the term loosely...) had ever hoped for.

Might be cheaper to drive a Jap 4WD in summer... my '89 Paj could be a mobile chiller in a heatwave...and an oven in snow country. On "bang-gas"

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Originally Posted by superquag

Wot you mean is... you need colder and better air-con than what the RR engineers (to use the term loosely...) had ever hoped for.

Might be cheaper to drive a Jap 4WD in summer... my '89 Paj could be a mobile chiller in a heatwave...and an oven in snow country. On "bang-gas"

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Honestly the AC in my 85 RRC is better than any standard japanese car I've owned. The main reason is the slide adjustable thermostat so you can choose how cold you want air out the vents. All the way down past -2C.

My 93 hard dash appears to have ok aircon, but it doesn't have the adjustable thermostat so can't go that cold. I will fix that.
My 95 soft dash I know the AC works but that's all. It's still not on the road.

My work car was +10C at the vents which didn't cut it in the summer sun. I've since modified it to get sub zero air out when required and it does ok. But it doesn't have the airflow.

My Skoda has +5C at the vents (R134a system) and shifts plenty of air. The only problem is it's black. So it needs AC a lot.

My short term problems on the 85 include an extremely noisey compressor. My mid term problems include having to change the condensor to fit in an intercooler and matching radiator. Hence the desire to find out how much heat it needs to shed.
Going for a new compressor and more modern parallel flow type is an easy call. The lack of capacity in your soft-dash aircon may be due to this. I can't see enough of the condensor to tell what type. But it doesn't look like anything made these days.

Then long term I'll be looking for quieter and better in-dash fans for the 93 with a better evaporator coil. Like the condensors they used to be just serpentine copper pipes with fins. Which are nothing special for flow or heat exchange.

Must have been lucky with my Japs... Paj was under 5 degrees and heaps of airflow everywhere, notably the demister, Mazda 626 as well And quiet with it. Both needed to be turned down on a hot summer's day after an hour or so.
Wife's Magna is also good on both counts. The CM Valiant was a health hazard.... sub-Arctic plus the blizzard reached the back window... Pity if your knees were in the way. Bit noisy on HIGH, like wind in your hair...

Only the Magna and the Softdash are on 134a, and the Classic is an embarrasment, doubly so when you consider the ticket price back in 1995, and what older and similar age Japs are doing.

Look on the bright side. Anything you do with yours will be an improvement. - You could'nt make it less effective.