AC install

[johann86911]

Originally Posted by Josh D

My work here is done.......


Glad to hear you have it sorted Johann. Sorry for all the drama here on Pelican.

That's okay. It gets pretty full on. But in between the barbs there is a lot of good advice so I think the best thing to do is stay out of it. Like yours! Bahamayellow actually attached a smaller pulley to his car to stop the resonance. I'm going to see whether having all the bolts makes the difference and so far it has!

Over time and when funds allow, I will replace other parts as outlined in all the other posts above!

[kuehl]

Johann,

I have seen very few 911's with a/c belt vibration so bad you could feel it in the cockpit; either with stock compressors or aftermarket.

Have you tried simply leaving the car in neutral, flat ground, e brake on, a/c on, deck lid up and have a mate increase the rpms (or push the throttle plate) so you could observe it?

[billybek]

I don't know if this was mentioned as there are large parts of this thread that I just skipped over, but what is the condition of the pulleys for the a/c system? If the belt had been loose and slipping for a long period of time the "Vee" inside the pulley is worn down and the belt starts to suck into the centre of the pulley. This could cause some interesting vibration problems.
Good to see that you have it worked out, Johann. You have had some very good advice from some of the contributors.
Cheers!

[69BahamaYellow]

First - Where were all you guys, when I was building my AC System Definitely some "lively" discussion going on in this thread....

As for the belt vibration, this caught my attention, as I literally just posted on this same topic. I designed my own system with a rotary vane compressor, so I figured I was the only one with this problem, but it looks like others have seen this with the original York recips and the conventional Sanden and Denso swash plate compressors.

What I found is that V- belts will resonate at certain RPM ranges. Sometimes it is severe, and you can feel it in the car, and other times you never notice, unless you are looking for it. Usually, this vibration can be mitigated by increasing or decreasing the belt tension, or by changing the mass of the belt (use a thicker or thinner one to raise or lower the frequency at which it vibrates). When that doesn't work, you have to use idler pulleys to effectively add stiffness to the system at strategic points. One will usually do the trick, but for my system, I found out that my belt actually had dual vibration modes (I had to use a strobe light to actually see this). The ultimate fix was to use 2 idle pulley's on the top side (slack side) of the belt. The bottom of the belt is under the highest tension, so perhaps that side does not go into resonance until above 8000 RPM or so. Needless to say, mine looks great up to 6000, and I'm not testing it any further. I posted pictures of my fix on DIY Air Conditioning for old Porsches.

Keep up the good work, guys. Even the (sometimes hard to understand)jabs back and forth have good information to gleen for the rest of us

[wwest]

Originally Posted by 69BahamaYellow

First - Where were all you guys, when I was building my AC System Definitely some "lively" discussion going on in this thread....

As for the belt vibration, this caught my attention, as I literally just posted on this same topic. I designed my own system with a rotary vane compressor, so I figured I was the only one with this problem, but it looks like others have seen this with the original York recips and the conventional Sanden and Denso swash plate compressors.

What I found is that V- belts will resonate at certain RPM ranges. Sometimes it is severe, and you can feel it in the car, and other times you never notice, unless you are looking for it. Usually, this vibration can be mitigated by increasing or decreasing the belt tension, or by changing the mass of the belt (use a thicker or thinner one to raise or lower the frequency at which it vibrates). When that doesn't work, you have to use idler pulleys to effectively add stiffness to the system at strategic points. One will usually do the trick, but for my system, I found out that my belt actually had dual vibration modes (I had to use a strobe light to actually see this). The ultimate fix was to use 2 idle pulley's on the top side (slack side) of the belt. The bottom of the belt is under the highest tension, so perhaps that side does not go into resonance until above 8000 RPM or so. Needless to say, mine looks great up to 6000, and I'm not testing it any further. I posted pictures of my fix on DIY Air Conditioning for old Porsches.

Keep up the good work, guys. Even the (sometimes hard to understand)jabs back and forth have good information to gleen for the rest of us

I find it puzzling that you are getting satisfactory cooling, in TX yet, from an OEM, OLDER OEM, (mostly) factory cooling system, as I suspect do many others. Can you tell us what the pump capacity is, displacment volume, of the new Panasonic compressor is vs the OEM compressor?

Therein might lie the answer. More pumping capacity would undoubtedly lead to higher pressures, sustainable high side pressures, more pressure = more HEAT = improvement of heat transfer efficiency for both condensors.

[SilberUrS6]

Originally Posted by wwest

Therein might lie the answer. More pumping capacity would undoubtedly lead to higher pressures, sustainable high side pressures, more pressure = more HEAT = improvement of heat transfer efficiency for both condensors.

What? WHAT???? Wait a minute - condenser capacity is just fine???? It's the heat transfer that's the problem?

Man, I hate it when the "problem" shifts around to make the "solution" correct.

[brads911sc]

Damn and I just ordered my SPAL fans and Spray on Insulation. LOL

Originally Posted by SilberUrS6

What? WHAT???? Wait a minute - condenser capacity is just fine???? It's the heat transfer that's the problem?

Man, I hate it when the "problem" shifts around to make the "solution" correct.

[SilberUrS6]

Originally Posted by brads911sc

Damn and I just ordered my SPAL fans and Spray on Insulation. LOL

Hell, next wwest will tell us that SPAL fans will actually cool the interior of the car wihout the rest of the AC system present. Hell, just take out the motor and run a SPAL fan on the decklid - the car *will* run much cooler!

[wwest]

Originally Posted by SilberUrS6

What? WHAT???? Wait a minute - condenser capacity is just fine???? It's the heat transfer that's the problem?

Man, I hate it when the "problem" shifts around to make the "solution" correct.

Condensor CAPACITY, yet again, is being confused with condensing CAPABILITY.

Back many years ago automotive design engineers figured out that more HEAT TRANSFER capability could be attained using the exact same engine cooling radiator by increasing the temperature of the coolant. So now we have PRESSURIZED systems to prevent boiling at sea level atmospheric pressure.

[SilberUrS6]

Originally Posted by wwest

Condensor CAPACITY, yet again, is being confused with condensing CAPABILITY.

No, wwest, it really isn't. The point just flew directly over your head.

[wwest]

Originally Posted by SilberUrS6

No, wwest, it really isn't. The point just flew directly over your head.

Maybe this wording, posted June 2010, will be of help as a aid to your understanding.

Originally Posted by wwest

I have always suspected that the major shortcoming, maybe the ONLY shortcoming, of the Porsche factory A/C system design is the lack of enough gas to liquid condensation capability.

Maybe someone could verify...??

In any case the only improvement suggestion to the above I would make is to add a rear spoiler to make room for a few 12 volt brushless computer fans/blowers (ball bearing, not sleeve) to fore airflow downward through the rear condensor. Even number of fans so pairs can run at 6 volts with the A/C system "enabled" and then switch to 12 volt only when the compressor is operating.

That's the way my '78 will be configured once/if it goes to Tucson. McCall Id at the moment.

[SilberUrS6]

Originally Posted by wwest

Maybe this wording, posted June 2010, will be of help as a aid to your understanding.

No, it doesn't help, because I understand just fine right now. But I am very amused at your continued attempt to be relevant to the discussion.

[wwest]

Originally Posted by SilberUrS6

No, it doesn't help, because I understand just fine right now. But I am very amused at your continued attempt to be relevant to the discussion.

No, just trying to help the local intelligence challenged naysayers.

[SilberUrS6]

Originally Posted by wwest

No, just trying to help the local intelligence challenged naysayers.

More hilarity from wwest. This time in the form of irony.