BMW published R134 performance vs real world vent temps?

[somecarguy]

The attached from BMW shows very low performance for R134 converted systems. These numbers are what I am seeing, but I am not convinced I have my R134 conversion charged correctly.

Last night it was 80deg / 80%humid and I saw almost exactly what the chart calls for:
59deg center vent (bmw: 57deg)
45psi low side (bmw: 47psi)
225psi hi side (bmw: 218psi)

I have a parallel flow condensor, reman comp, replaced rec/dry, press switch, exp valve, flushed lines etc etc. The strange thing is that I charged with only (2) 12oz cans of R134 which means I likely have LESS than 24oz of refridgerant in the system which calls for over 30oz.

What vent temps are you all seeing?

One reason I doubt this chart is that its showing R134 BEATING R12 with lower discharge temps in all cases...

[ELVA164]

I don't have any specific numbers, but my car (without a functioning recirculator) puts out cold (anecdotally below 55º for sure) until maybe 90ºF, then still does alright past 100º. I replaced everything but the evaporator, though, including a Sanden compressor.

[Jeffnhiscars]

Absolute temps can be misleading. Focus on the temp differential which will, of course, be lower when the humidity is higher.

[tomstin]

I'm struggling with this also. I replaced everything with new, with the exception of the steel parts of the hoses. I had the rubber replaced at a local hydraulic shop with barrier rubber. I didn't have an accurate scale but I think I have roughly 30 ounces of R134A in the system. The pressures seem to be very close to the BMW chart.

I seem to get a 20 degree improvement over ambient air. Its been hot and very humid here in NC lately. Now, I don't trust the thermometer I have now and have a digital, with better reviews, on its way. A contributing factor, I have a "E" model so my RPMs on the highway are pretty low. I've started experimenting a bit with driving in a lower gear to see the RPMs effect on the cooling.

It's a whole lot better than driving without AC but I'm not convinced its 100% just yet.

[somecarguy]

I have the exact same experience - 20deg delta in medium to high humidity after a highway drive.

Yesterday in 89% RH I saw 20deg drop from 78>~59 that evening in 93% RH I saw 20deg drop from 76>~56.
Looks like 95% RH today (joy) so I'll have to wait a bit to see if lower humidity improves temp drop.

I was also testing on blower speed 1, recirc. Any higher speed and I get significantly higher vent temps.

[superj]

using all original parts, and running r-290, if the outside temps are below 90, I see high 40s at the center vent (using a meat thermometer from the house). and that's with the normal 90-100% humidity where I live. over 95 degrees and the temps climbs to mid 60s at a stop light and mid 50s while moving

[Jeffnhiscars]

recirc is cheating lol and turn the blower up and aux fan jumped to high (dont forget to up the low speed fuse)

[ELVA164]

If you guys are using original-type compressors, you're going to lose efficiency. They may work with R-134a, but they weren't designed for it.

[somecarguy]

Yup, 10p-15 here. I'm not expecting it to cool like the wife's S2000. But I don't want to leave anything on the table either.

[ELVA164]

The compressor makes a big difference.

[tomstin]

If you guys are using original-type compressors, you're going to lose efficiency. They may work with R-134a, but they weren't designed for it.

In my case, brand new Vintage Air Sanden Air Conditioning Compressors 04808-VUA

[RomeoMike]

In Vegas, once the temp goes over 100, there goes any chance of getting vent temps below 40 degrees. Closing the two right hand dash vents and keeping the fan on speed 1, I can get it to 44 degrees. On fan speed 2, 50 degrees. The 91's setup is an OEM compressor and original condenser and evaporator using R-134a.