AC vent temps

[Ed Bighi]

Folks, I have been getting some pretty good vent temperatures out of my bone stock AC over the last month. Here they are. On 100+ degrees ambient, 40-45 or better on the freeway, maybe climbing to the high 40's on very slow streets, and a maximum of 60 if the car is sitting in traffic and barely moving. At night, the temps are in the high 30's or low 40's regardless of motion. The other day when it was 111 farenheit, I was still able to see vent temps under 50 degrees if I kept the car in motion. It seems to me that either installing a fan under the condenser to improve low speed situations or using Performance Aire's curved parallel flow condenser might improve things a tad. But to be honest, I am happy the way things are now since I don't enjoy driving in traffic.

The reason I got these temps is the refrigerant. A short while ago I went with the Enviro Safe industrial blend. This is their mix with a somewhat higher content of propane than the standard mix in the regular cans. I used it for a while in mine and my sister's 911. While it was good, on a 108 degree day it tended to take a tad to long to cool the car. While better than r-12, I still wanted to play around a bit with refrigerants. And since my compressor is on it's last leg, I figured my car is the perfect guinea pig. So a few weeks back, I decided to put in pure propane. Even though pure propane raises the high side pressure a substantial ammount, I lost fear of doing it after seeing some very high pressures in a 930 running standard r-12 through it's tiny condenser. Well, I have gotten sort of addicted to the results. On the freeway this thing gets pretty cold. If I were living in any other state, this thing would downright freeze. I think I am going to leave that stuff in. It's nice being cool in a 911 in Arizona. And again, with a stock AC. My mechanic could not believe the vent temps. It's amazing how well that stuff cools.

[bigrubberjeep]

Propane? What ever you do, don't let your friends talk you in to "hot boxing" your car. No sparking it up with the AC on.

[jgporsche]

Are you using a procooler or aftermarket condenser? How much propane and how do you adapt the low side connection?

[subdewd]

same here used about 20% iso and 80 propane running mid 40's
@ vent. Amazing results and last time I checked high side was
210 @ 85. if I remember right

[Ed Bighi]

No aftermarket condenser. Everything is stock. But a pro-cooler might be something that would reduce the high side pressures if someone is interested in having them reduced. It just might allow someone to run pure propane with close to normal pressures. While high side pressures are a non-issue when running 80%/20%, when using pure propane, they get high. Though nobody outide of Arizona would get high side pressures as high as they get over here. But the cooling one gets on pure propane is simply amazing. Considering the ambient temperatures where I live, the results I am getting on a purely stock AC are pretty damn good. With that in mind, there is absolutely no reason why anybody outside of Arizona should sweat inside their 911. Not that I am sweating any more, but over here it takes a bit for the interior of the car to cool when it's been left in the sun all day. But once it cools down, it stays cold.

[Ed Bighi]

Originally posted by jgporsche
How much propane and how do you adapt the low side connection?

Simple, here is how. All you need is a regular R12 charging hose, a small hose clamp and a 1/4 to 1/4 mip fitting from the plubing aisle at Home Depot. First remove the tip that is screwed on the nozzle. There is some drilling that has to be done on the Benzomatic nozzle as has been explained in the past here in the Pelican forum. So just do a search for "propane ac." Really simple. Then use the fitting to adapt the hose since it is simpler than what other people have used. Then you chop off the end of the charging hose that does not push on the schraeder valve. The one without the little tip coming out. Use either some epoxy putty or soldering to attach the fitting to the nozzle. I prefer the 20 minute epoxy putty that comes in the little tubes. When hooking up the two pieces, make sure you put a toothpick on the end of the nozzle so that the epoxy does not block the pathway. When the two pieces are together, remove the toothpick and let cure. It dries rock hard and with no leaks. Then you have to slip the hose over the fitting. This is tough since it is a tight fit. Just apply a little bit of grease over the fitting so that it slips in easier. Grab the hose with a rag so you get more leverage and twist it on. It's a ***** but with some effort it will go fully in. Put on the hose clamp for safety and voila. Easy and cheap. As to how much propane, usually 16 ounces. Ideally, one big bottle of Benzomatic on an empty system since some is usually lost when clearing air from the charging hose, and it is tough to get it all out of the bottle. Actually, I used up part of a second bottle since the first one started freezing up and I lost patience. Charge with the decklid down and have somebody keep the rpms at around 2K to speed up the fan. Stop when the vents get cold. You don't want to overfill so when the AC vents get noticeably cold (maybe in the low 60's), that's it. It will cool down much more once the car is on the road. This is really the only way to charge since the pressures are quite different than normal. It's trial and error but propane is cheap enough that, even if you waste some, it's no proplem.