ctsv a/c compressor

[ls173camaro]

Does anyone know if this compressor will work with vintage airs system? I know the problem with the ls compressor is that they are usually variable displacement compressors. But the ctsv uses a Denso 10S17F A/C fixed displacement compressor or at least that what the pace performance description reads. It should work with the corvette acc to since they share the same balancer pulley. I'm going to call V.A. in the morning. Thanks for any input Bill

[diesel25lrs]

I ran into the same issue with my VA system as i have a NIB CTSV compressor sitting in my garage still... VA told me that it wouldn't work bc of exactly what you mentioned above- variable...
I didn't want to take any chances with the warranty so i used their sanden...

[40STY]

Just bringing this thread up from the dead because I can't find an answer to this question.

Has anyone used a CTSV compressor in their LS swap? And is the CTSV Denso 10S17 compressor definitely fixed displacement (from the expanded GM parts diagrams it sure looks like it, with a clutch in the pulley).

I've got the 6.0L out of a G8 (so short balancer like the Corvette) and have notched the frame so that the stock AC compressor fits, but it's a variable compressor. If the CTSV compressor is fixed, it would be an ideal swap, as it uses the same close balancer.

I've also got the condenser, expansion valve and interior HVAC/evaporator out of the G8 fitted and plan on controlling it all totally separate from the PCM/BCM. Will an old school trinary switch work with this setup?

[parsonsj]

A clutch doesn't mean fixed displacement. I'd bet the CTSV is variable displacement -- I think only trucks still use fixed displacement compressors these days.

[40STY]

My bad- the G8 uses a clutchless variable compressor, so got it stuck in my head that all variables are clutchless, which they aren't.

There's not a lot of definitive info on the net, but I did find this:
http://www.denso-am.eu/media/74742/l...sor_web_uk.pdf

According to that Denso booklet, any compressors with the 10S or 10PA desigantions are dual swash plate, fixed displacement compressors. Everyone seems to be in agreement that the truck compressors are fixed. The CTSV uses the same 10S17F compressor type, so why wouldn't it be the same = fixed-type?

[parsonsj]

I did some of that same searching for Denso 10S and 10PA compressors... and I think you're right: they are fixed displacement.

[LowNfast]

I know this is an old thread, but, The ctsv compressor WILL work with VA systems.

[aika1]

Does anyone know if this compressor will work with vintage airs system? I know the problem with the ls compressor is that they are usually variable displacement compressors. But the ctsv uses a Denso 10S17F A/C fixed displacement compressor or at least that what the pace performance description reads. It should work with the corvette acc to since they share the same balancer pulley. I'm going to call V.A. in the morning. Thanks for any input Bill

Resurrection!

I just called GM asking about the variable vs. Fixed displacement compressors, and they said that if you buy the corvette accessory drive kit (19155067) which has the Variable displacement compressor, but use it with the classic auto air or vintage air system that requires a fixed displacement compressor, the VDC that comes with the 19155067 will act as a fixed displacement and just stay on when the car is running. I don't know if that's how the fixed displacement typically operates or not, but that's what they told me! I'd love an AC guy to weigh in on this one...

[Volks]

Just a little info as I was also looking for a compressor kit for an LSA engine. I ended up buying the gm kit 19244106. It doesn't use a tensioner, just stretch the belt on. It seems like it might be tighter to the engine. The kit comes with a 19130461 compressor. It says Denso 10S17F on it. From what I can tell its a fixed displacement compressor in that kit. Just another option. I'll find out how well it fits into a 71 Chevelle soon.

Don

[Vintage Air tech.]

I don’t believe it is possible to effectively make the variable displacement compressor fixed without major modifications. Quite a few years back, we worked directly with Delphi engineers to try to fix variable displacement compressors. They said modifying or plugging the control valve would not result in fixed displacement operation. Delphi’s modification involved actually welding the swash plate mechanism within the compressor. To my knowledge, this is the only effective way to fix the displacement, but it is also risky and not advised (easy to destroy the compressor by warping the mechanism). The reason valve modification is ineffective is that the displacement is varied via differential pressure between the crank case and the suction side of the compressor. The valve controls this differential pressure. I don’t believe blocking the valve will “lock” the compressor but may instead disable the variable displacement mechanism, making its function unpredictable.

The reason variable displacement compressors don’t play nice with standard TXVs that were designed for clutch cycling compressors is that both the TXV and the compressor control valve are controlling to suction side pressure/temperature. With both closed loop controls working to adjust the same parameter, you end up with wild fluctuations in suction pressure and consequently vent temperature. TXVs can be designed to play nice with variable compressors, but they have to be carefully tuned to the entire system, which is impractical for use in the aftermarket when consumers regularly mix and match components. A fixed displacement compressor will work out of the box w/o any mod's or creative liberties.

Resurrection!

I just called GM asking about the variable vs. Fixed displacement compressors, and they said that if you buy the corvette accessory drive kit (19155067) which has the Variable displacement compressor, but use it with the classic auto air or vintage air system that requires a fixed displacement compressor, the VDC that comes with the 19155067 will act as a fixed displacement and just stay on when the car is running. I don't know if that's how the fixed displacement typically operates or not, but that's what they told me! I'd love an AC guy to weigh in on this one...

[aika1]

I don’t believe it is possible to effectively make the variable displacement compressor fixed without major modifications. Quite a few years back, we worked directly with Delphi engineers to try to fix variable displacement compressors. They said modifying or plugging the control valve would not result in fixed displacement operation. Delphi’s modification involved actually welding the swash plate mechanism within the compressor. To my knowledge, this is the only effective way to fix the displacement, but it is also risky and not advised (easy to destroy the compressor by warping the mechanism). The reason valve modification is ineffective is that the displacement is varied via differential pressure between the crank case and the suction side of the compressor. The valve controls this differential pressure. I don’t believe blocking the valve will “lock” the compressor but may instead disable the variable displacement mechanism, making its function unpredictable.

The reason variable displacement compressors don’t play nice with standard TXVs that were designed for clutch cycling compressors is that both the TXV and the compressor control valve are controlling to suction side pressure/temperature. With both closed loop controls working to adjust the same parameter, you end up with wild fluctuations in suction pressure and consequently vent temperature. TXVs can be designed to play nice with variable compressors, but they have to be carefully tuned to the entire system, which is impractical for use in the aftermarket when consumers regularly mix and match components. A fixed displacement compressor will work out of the box w/o any mod's or creative liberties.

I got some more information on this from GM tech, who called an airconditioning tech that works for the company. This is the information that was shared:

I’m sending you some info on the differences on fixed and variable A/C compressor, and you can send this to Classic Auto Air if you’d like. I’m sure they already know, but if it will help…



FEAD A/C Compressors

There has been some question about the type and operation of the A/C compressors that are included in the GMPP FEAD kits. The small block and big block kits contain fixed displacement (cycling clutch) compressors and the LS kits will include a variable displacement compressor.

All A/C compressors have a clutch on the front of them. When the A/C system is turned off, whether the customer turned it off or there is a fault (excessively high or low pressure), the clutch will be disengaged. When the system is turned on and all pressures are within range, the clutch will be engaged. The clutch will make an audible click when this happens. The big difference between a Fixed Displacement (aka cycling clutch) Compressor and a Variable Displacement Compressor, is that once engaged, a VD compressor can change it's displacement resulting in pressures that should stay within normal operating range. This prevents the clutch from disengaging unless turned off by the driver or a fault occurs. On a fixed displacement compressor, once the clutch is engaged, refrigerant pressures climb until they reach a set pressure and the clutch is then disengaged. Pressures then fall to lower set pressure and the clutch is re-engaged. This cycling continues the entire time the A/C is on. Cycle on/off time will vary based on pressure and all of the factors the affect pressure (charge, temperature, restrictions, etc...).

Speaking of things that affect pressure, all A/C systems use an in-line restrictor to drop refrigerant pressure. This drop in pressure is what causes the evaporator core to become cold. GM uses two different restrictors, a fixed orifice or a Thermal Expansion Valve (TXV). A fixed orifice is self explanatory, it is an in-line restriction that does not change. A TXV uses a capillary tube to measure evaporator core temperature. The TXV will change the size of it's opening based on evaporator core temperature to prevent core freezing. Either of these systems will work with either style compressor.



I found there is not going to be a way to make our variable compressor work as a “fixed” compressor. When I talked to my engineering liaison, he didn’t understand why Classic Auto Air is saying it must be a fixed compressor. If they gave you a specific reason, could you share that with me?

I also verified you would be able to use the non-A/C Corvette FEAD kit and use the components for the A/C from the CTS-V kit. You will need to check and make sure the balancer will line up, when using those A/C components.

[aika1]

I chatted with the Classic Auto Air folks again. It sounded like there's not a lot of reason why a V7 compressor as found on the LS drive kits won't work. Other than the fact that most of these kits were designed 1-3 decades ago and no one has verified they work or don't. Anecdotally, everyone I have talked to that has installed an LS compressor (variable) with Vintage or Classic Air systems has not had a problem. I wonder how much of this is covering the ol' rear end on their part since it hasn't been tested and verified in-house.

[Volks]

And the GM kit Part number 19244106 came with a Denso 10s17f compressor. Which I still believe is a fixed compressor.

[jlcustomz]

I will say this without reading in depth into this discussion or typing too many details of my experience. I did a 99 LS1 g-body swap back in 2002 using factory ls compressor & later swapped to a VA system. Later swapped in a sanden compressor in factory low mount position after going through a 2nd factory compressor in about 6 years.

Particularly if an engine isn't installed yet, making adapter brackets to mount a reliable proven compatable aftermarket compressor, at least for me in my case, shouldn't be that hard.
Just another thought.

[Gaarg]

it will, I recently bought compressor on boodmo on car with similar air system. Agree with jlcustomz, it wasnt so hard to install.

[KUL FIR CHICK N]

This is a very common question and one for which there is not a simple one-sentence answer, so I'll attempt to answer it for the folks here since many of you on PT appreciate a more technical answer than the average Joe. First the short answer:
No current aftermarket ac system which uses thermostatic expansion valve (TXV) metering device is compatible with internally controlled variable displacement compressors (ICVDC).
The reason for this incompatibility is twofold. Both compressor durability and system performance will suffer when using an ICVDC on a system that is not specifically designed for it.

1. Compressor life will be shortened
2. System pressures and temperatures will be unstable at low load
3. Vent temperature will be higher than design intent

Now, a little more detail……
The following article, published on the MACS website in May of 2013 describes the basic principle of VDC operation:


(Delphi Automotive illustration)
by Jacques Gordon
When a belt-driven piston-type A/C compressor is engaged, it produces a noticeable ‘thump’ and a reduction in engine power. This can be eliminated by keeping the compressor engaged all the time and controlling refrigerant flow by varying the displacement of the compressor.
The variable displacement compressor is an axial piston design, with the pistons driven by a wobble plate or a swash plate. Since the angle of that plate determines the length of the piston stroke, changing that angle changes the length of the stroke, therefore changing the amount of refrigerant pumped (displaced) on each stroke. The plate angle is controlled with linkage and springs, and it’s adjusted by changing refrigerant pressure in the compressor housing. So the key to controlling displacement is controlling housing pressure.
When housing pressure is increased, pressure on the back side of the pistons keeps them “higher” in their bores, closer to the cylinder head. This reduces the angle of the swash plate and shortens the stroke, reducing displacement. When housing pressure decreases, a spring pushes the adjusting linkage away from the cylinder head, increasing plate angle and lengthening the piston stroke to increase displacement. Housing pressure is controlled by a valve with ports and passages that connect to the suction (low-side) and discharge (high-side) chambers of the compressor head.
Two different types of control valve are used; mechanical and electronic. The mechanical valve has a precision diaphragm that senses low-side pressure. When the cabin is warm, evaporator temperature increases, which increases low-side pressure and collapses the diaphragm. A port opens to vent housing pressure to the suction side of the compressor head. This decreases housing pressure and increases piston stroke, increasing refrigerant flow through the system.
As evaporator temperature decreases, so does low-side pressure. The diaphragm expands to close the low-side vent port and at the same time open a port that admits high-side pressure into the housing. Higher pressure reduces piston stroke and refrigerant flow volume. Remember, changing flow volume doesn’t change pressure, so a diaphragm-type control valve remains stable.

Delphi’s mechanical displacement control valve is actually two valves in the same body. When low-side pressure is high, the bellows collapses (towards the left). The cone valve opens and pressure vents from the wobble plate case (compressor housing) through the by-pass hole and to the suction side of the compressor head, reducing housing pressure. When low-side pressure is low, the bellows expands to close the cone valve and open the ball valve. Pressure vents from the discharge cavity (high-side) to the wobble plate case, increasing housing pressure.
Around 2001, DENSO introduced a pulse-width-modulated solenoid valve to control housing pressure, based on information from temperature and pressure sensors in the refrigerant system. With a computer controlling the valve’s duty cycle, compressor displacement can be used to control evaporator temperature, rather than the other way around.
The mechanical control valve is still used in some systems because it’s inexpensive and reliable, but it’s range of control is limited. Electronic control valves are becoming more common, and on many applications there is no clutch, so the compressor runs continuously. Displacement can be reduced to about 1 percent when cooling is not needed, keeping seals lubricated, minimizing oil pooling and preventing other kinds of damage that result from long periods of inactivity. Ultimately there is less load on the engine when the A/C is in use, reducing the system’s contribution to tailpipe emissions. As mileage and emissions regulations continue to tighten, we can expect to see electronically-controlled variable displacement compressors on more new models.

The key here is the control valve. In an ICVDC, the control valve is indirectly adjusting the compressor displacement based on the suction side pressure. It will allow full compressor displacement (100% capacity) until the suction side pressure begins to approach its pressure set point. As the suction pressure drops and approaches the set point, the swash plate will begin to de-stroke, reducing displacement and therefore refrigerating capacity until an equilibrium is reached between compressor output and system demand. It’s important to note that the valve will not allow the suction side pressure to fall below its set point. I’ll come back to this later.

In a TXV metered ac system, which almost all aftermarket systems are, the orifice size and therefore the refrigerant flow is also regulated by a diaphragm that is tied indirectly to system suction pressure, similar to the ICVDC compressor. As the suction pressure and temperature fall, the TXV begins to close the orifice, regulating flow to ensure that liquid refrigerant doesn’t leave the evaporator and enter the compressor, which could damage it. This action is controlling “superheat” which is the temperature of the refrigerant above its boiling point at a given pressure. Under very heavy load, the TXV is usually all the way open and under very light load the TXV is nearly all the way closed. In-between these extremes, the valve is constantly modulating the orifice size to maintain its superheat setting.

As you can see, both the ICVDC and TXV are closed-loop control devices which are both attempting to control the same variable at the same time. The majority of OEM HVAC systems that incorporate ICVDCs are fixed orifice tube designs. Some OEM HVAC systems incorporate both an ICVDC and a TXV, but in these systems the control devices are carefully calibrated to work with each other.
Since aftermarket system configurations vary widely due to vehicle customization, these devices cannot be reliably calibrated to each other and therefore often battle for control or “hunt”, especially under moderate to low load conditions. The symptoms of this hunting will be unstable system pressures and vent temperatures. In addition to hunting, the TXV can close almost completely under certain low load conditions while the compressor continues to turn. The compressor relies on refrigerant flow through the system to lubricate some of its components. TXVs used with ICVDCs have features built-in that ensure continuous flow of oil through the system, even when the orifice is completely closed. Without these features, the compressor will eventually fail. Compressor failure often destroys the entire system.

All automotive AC systems have to limit the minimum evaporator temperature to avoid freezing by either turning off the compressor (as with fixed displacement compressors) or reducing compressor capacity (as with variable displacement compressors). TXV systems typically incorporate a separate control device that controls the evaporator surface temperature via a mechanical thermostat switch coupled to a sensing probe inserted into the coldest spot in the evaporator coil or an electronic thermostat and a thermistor probe, also inserted in the coldest spot of the coil. The thermostat is set to turn off the compressor when the evaporator surface temperature approaches freezing, usually around 33-34 degrees F and then turn the compressor back on several degrees higher. Under most conditions, when we disengage the compressor at a 34-degree evaporator surface temperature, the suction pressure is around 20 psi.

Most fixed orifice tube systems, which are similar in theory but differ significantly in several ways, avoid freezing by sensing suction side pressure, usually switching off the compressor when suction pressure dips to a preset limit. Since suction pressure is not an exact indicator of the surface temperature of the evaporator, the compressor is shut off much earlier (higher evaporator temperature) than in systems where surface temperature is measured. Typically, the set point for these pressure switches to open, disengaging the compressor, is 30-32 psi. This is an important point to remember because most ICVDCs have a control valve set point near this same pressure.

Let’s now double-back to the earlier mention that the ICVDC control valve will not allow the suction pressure to fall below its set point. Since the set point on most ICVDC valves is 10-15 PSI higher than where aftermarket systems are designed to operate, the valve will limit how cold the evaporator can get. These valves are factory set and not adjustable so when you use a carry-over compressor, such as one from an LS powered F-body with ICVDC, you’re stuck with the factory valve setting.

The two takeaways from all of this are these:

1. Never tell a hot-rodder something won’t work, he’ll prove you wrong. In this case, yes it will work, but it won’t work well.
2. Even if you can make it work, you risk compressor failure, which often circulates metallic fragments throughout the system and essentially destroys everything.

To close, many may not be aware that Vintage Air also manufactures complete HVAC systems for OEM manufacturers and is currently supplying the HVAC system for the 2016+ Ford GT (as well as the previous model). Both vehicles had variable displacement compressors. The ’05 GT had a variable capacity scroll compressor with an orifice tube and the ‘16+ has an externally controlled variable and a TXV. We’re well versed in the application and control of VDCs. For aftermarket applications, however, we feel fixed displacement compressors offer the best performance, reliability and value for the aftermarket systems currently offered.

Ryan Zwicker
Vintage Air, Inc.

[KUL FIR CHICK N]

And the GM kit Part number 19244106 came with a Denso 10s17f compressor. Which I still believe is a fixed compressor.

This is correct and yes, it is compatible with Vintage Air and other aftermarket systems. This is a good option if you can fit it. Keep in mind you'll need the special fittings to mate it to whichever hose kit you're using.

It should also be noted that there are three generations of CTS-V, each with a different engine and also each with different compressors. The compressor that is being talked about here is from the second generation CTS-V with the LSA engine.



Ryan Zwicker
Vintage Air, Inc.