Remanufactured A6 Compressor Came with Oil

[Domenic T.]

Re: Remanufactured A6 Compressor Came with Oil

Ray,
I think that is a good guess because the 365 with air has the largest pulley.

DOM

Hello Dom;
Do you think the design change is a result of expected higher RPM, smaller passenger compartment, a combination of both, or additional information?
Ray

[Tom L.]

Re: Remanufactured A6 Compressor Came with Oil

Hi Dom, only referring to the valve plate. In commercial refrigeration compressors there are four main variables that effect compressor design depending on the application. They are displacement, comression ratio (usually as high as can be using flat top pistons and a valve plate with no chamber as we see in auto engines), electric motor size and valve plate design. Often a compressor with similar displacement, compression, and motor size will have a different application because of the valve plate design.

Changing pulley size would be similar to changing electric motor size, displacement is directly related to the electric motor size, in refrigeration dished pistons sometimes are used to decrease the compression ratio to decrease discharge temperature, and valve plate design is usually changed to deal with disgarge temperatue. I'm just curiuos to see if over the years GM did something about compression ratio and valve plate design when changing from the POA system to a low pressure cut out system which is most common in cars today.

[Domenic T.]

Re: Remanufactured A6 Compressor Came with Oil

Lynn,
Thats good to know. I have cleaned valve plates stacked together and they look the same.

I guess they could change the compression also by chamber size in the end plates.

I am going to make a few calls and see what I can find out and post it.

One question is when they went to teflon rings, another will be the compression ratio.

I find late pistons in early casses telling me they do the same with the compressors as they do with starters when they rebuild.


DOM

Hi Dom, only referring to the valve plate. In commercial refrigeration compressors there are four main variables that effect compressor design depending on the application. They are displacement, comression ratio (usually as high as can be using flat top pistons and a valve plate with no chamber as we see in auto engines), electric motor size and valve plate design. Often a compressor with similar displacement, compression, and motor size will have a different application because of the valve plate design.

Changing pulley size would be similar to changing electric motor size, displacement is directly related to the electric motor size, in refrigeration dished pistons sometimes are used to decrease the compression ratio to decrease discharge temperature, and valve plate design is usually changed to deal with disgarge temperatue. I'm just curiuos to see if over the years GM did something about compression ratio and valve plate design when changing from the POA system to a low pressure cut out system which is most common in cars today.

[Domenic T.]

Re: Remanufactured A6 Compressor Came with Oil

I was contacted with a few questions about the rings and the different piston design (flat top/ dish)

i said I would post the answers I got and they were no help other than one question they answered when I asked them how they rebuilt classic car compressors.

You don't want to here it.

When I asked them where yhey got their cast rings they said they couldn't get them and they re-use what the parts they can't get.

So if your compressor has cast rings instead of teflon , they don't get replaced.

Now what I was told is that the company that makes the rings might do a special order if you bought 100 sets or more.

The good news is that the cast rings I have seen were not all that bad.

The end gap with new cast rings is .008 and I have found up to .013 in the ones that I have taken apart.

This may be the reason that the compressors are failing if they have a lot of miles on them when you send them in.

Bassically you may only get a re-seal.

Before you send one in ASK them if they do them in house . If they do then do they replace your cast rings or do they replace your old pistons with new style pistons that take teflon rings.

If they are the middel man and get them done elsewhere then it's a crap shoot, you can't tell what your getting.

1- overhauled
2- rebuilt
3- re-manufactured

There is a difference.

DOM

I thought I would throw in a tid bit or two about A-6 compressors.

First of all I'm not good at putting names to 3 letter oils, it has to be spelled out or I can make a mistake.

My shop is tooled up to do A-6 compressors and it wasn't till I recieved NCRS compressors that I saw the lower compression dished pistons (SEE PIC) that were in known mid year vette compressors.

All the others I have seen come out of passenger cars are flat tops.

That and the pulley ratio must have been calculated for the RPM.

There are a 100 ways to cut corners that shops use when so called rebuilding and I have seen them all.

Also the cast rings are being replaced with tefflon, (kinda like the new inexpensive home air compressors) The pic shows the 2 style piston types and rings.

Here are 2 piston sets, one with the cast ring and the other with a NEW tefflon ring that hasn't been stretched in place.

I think Joe lucia may be the only one here to figure out the dish piston application by part #, I am only guessing.

DOM

[Domenic T.]

Re: Remanufactured A6 Compressor Came with Oil

Dave .
That makes sence, it is dependant on the intake presure somthing like a blower or supercharger.

So what we know now is that the hi-low on a smaller car like a vette with dish pistons may be diffferent than the hi-low in a bigger car with flat tops?

DOM

Interesting stuff in this thread. Especially the dished pistons in the C2 applications. Allow me to add a thought:

I don't feel this has anything to do with "compression ratio", because there is no such thing in a refrigeration application. The amount that the cyl fills on the down stroke is dependent on system load. The higher the low side, the more "load" on the compressor, and the more the cyl is filled by the higher-pressure.

On the up-stroke, the outlet valve is opened when the cyl pressure exceeds the system outlet pressure. Because of the temperature/pressure relationships of refrigerants, the system pressures, and therefore the volume of cyl fills varies depending on many factors.

The "dish" affects cyl volume. The compressor actually has more displacement than one with flat tops. But the inlet and outlet pressures are going to be identical for both pistons under the same operating conditions.

Here's my guess as to why the C2 may have the dished pistons. The C2 has a fairly small cabin. Certainly easier to cool, and keep cool than a large passenger car with lots of glass and interior volume. Systems running under low heat-loads are susceptible to liquid-slugging in the suction line. C2 POA/TXV systems could very possibly have liquid-slugging issues because of the low heat-loads. We all know that liquid doesn't compress. The dished pistons would make the compressor a bit more resistant to liquid damage, because of the greater cylinder volume provided by the dish. Small drops of liquid would be accommodated in the dish, without completely filling the cyl and breaking parts.

But it's not "compression ratio". Think about it. There's no such thing in a refrigeration system. It's only capacity, or displacement.
Regards,
Dave

[Ray G.]

Re: Remanufactured A6 Compressor Came with Oil

My hypothesis is that the C2 will be cooler more frequently, and therefore be more apt to develop liquid slugs in the suction hose. The recessed pistons give the liquid somewhere to 'go' without causing damage. Any liquid remaining in the dish at the top of the stroke would flash to gas on the next down-stroke.

Hello;
Great point.
Ray

[Tom L.]

Re: Remanufactured A6 Compressor Came with Oil

Interesting but sadly not new stuff in terms of rebuilders. I my buisness rebuilts are often the standard replacment for some compressors, usually 1 HP or higher (there are other details but it doesn't matter here). There are many "rebuilders" but I won't sell any of them. Typically those are merely "fixed" and the cost reflects that.

The manufacturers do their own rebuilding because the cores are costly and tossing them doesn't make sense. If it doesn't come in their box (Copeland, Dunham Bush, etc..)I won't sell it.

Sadly there's not a big market for A6's, otherwise there would be part availibility and good rebuilts availible. It's a supply and demand thing. Something that hurts us guys trying to fix things correctly.