trabots

When working my KC works great, getting my tank water down to around 40deg and under freezing with the cabin evaporator bypassed with the "Drag Kit" valve. The problem is the inconsistency I see in the cabin thermometer which reads the tank water temp. Sometimes the IC water cooling just stops totally going well above ambient before suddenly kicking in. Other times the recovery after a pull is very slow compared to other times. I suspect the Tx valve is the culprit. As delivered the TX valve is sensing temp of the water outlet when all information I see on Tx valves is that it should be sensing the refrigerant suction line temp. Joe??

Tommyboy928

Same problem on mine, it comes and goes the aircon cooling ,, some valve stopping the operation

gixxerboy

I'm having similar issues with mine. Did you find a solution?

trabots

I have a 2nd KC which I am going to install in series with the first. That should get the refrigerant sufficiently warm by the exit of the 2nd KC that the TX valve will be irrelevant (always open). The TX valve is supposed to stop liquid refrigerant (still cold) going back to the compressor and possibly damaging it. I purchased a different TX valve which allows adjustment of the spring without de-gassing but it still stalls no matter where I have it adjusted. There are different orifice sizes for TX valves however Joe doesn't seem to want to know. I plan to put a ball valve either side of the TX valve so that I can also change orifice size without de-gassing. We are not allowed to de-gas/re-gas ourselves here in Oz so expensive to make adjustments. He did tell me early on that he runs 2 KCs in series on his drag Mustang for 20% less water temp whatever that actually means in degrees. The Dodge Demon has an evaporator cooled SC system but as yet I can't find any information in that regard. These evaporators are found in cool drinks fridges and may be a cheaper way to go.

sjc246

Am I to take it that you modified the ambient air temperature sensor to read the temperature of your water tank (and display that in the instrument cluster)? If so, that's most likely part of your problem (if not all of it). That temperature sensor isn't just for the display in the instrument cluster: among many other things, it is used to determine the automatic climate control operation. For example, if the ambient temperature reads cold (I'm not sure the exact value, but probably somewhere around 40-45 degrees), the a/c will be disabled (compressor switched to minimum displacement) because a/c is unnecessary at that temperature and operation could cause damage (liquid refrigerant returning to the compressor = broken compressor).

Even if you have not modified the ambient temperature sensor operation, running the evaporator (the water tank) near the point of freezing may adversely affect operation (and even potentially cause damage if the controls fail to regulate the compressor).

trabots

I have a totally independent probe into the top of my tank and an independent temp read out. Getting the water as cold as possible is the game with evaporator cooled IC water. Below freezing IC water will have no effect on any factory systems, it is not frozen as I use antifreeze. All the ECU sees is IATs from which it will determine whether to pull timing or not. At 10 deg F, I have seen my AC still working well proven by my KC operating still operating. The colder the ambient temp the colder the IC water gets, to a point as you say, where the AC compressor gets switched off by the ECU. What this thread is trying to solve is the erratic operation of the TX valve on the evaporator which I see by the erratic temp variations in the IC water.

sjc246

I don't have much experience with the KC, but I do know thermodynamics and a/c systems so I thought that info might help.

I'm not saying that below freezing IC temps will affect the engine. As you said, it has no idea what the IC temp is. However, the a/c system isn't designed to create those temperatures. The refrigerant flow isn't controlled solely by the TXV; it's also controlled by the variable displacement compressor which is designed to keep the refrigerant temperature above freezing by regulating the low side pressure. By regulating the low side pressure to a bit below 30psi (not sure the exact point) the evaporator temperature shouldn't get much below freezing (regardless of TXV operation). The evaporator temperature should only drop below freezing once the compressor reaches minimum displacement (so it cannot further reduce refrigerant flow). As long as ambient temperature and HVAC evaporator temperatures are ok, it will keep going at minimum displacement and can (theoretically) cool near or slightly below 0 degrees if the load is small enough (or until you get liquid refrigerant back to the compressor and it stops cooling completely). However, if you add any load (heat) to the IC at this point, the compressor will stay at minimum displacement until the IC temperature (and thus, refrigerant pressure) goes above freezing (at which point it will resume modulating the temperature right around the freezing point until load drops too low again). Normally the variable compressor and HVAC TXV work together to control the evaporator temperature to be just over the freeze point. When you start mis-matching compressor set-point and TXV set-point (as I suspect is the case if your IC is below freezing), you are bound to get some erratic operation even if both components are working correctly.

trabots

That is great info. The coldest I actually got the IC water to was -2 deg C. That has never been repeated since I fixed my SC pulley. It now only gets down to around 5 deg C as there is intake air compression now going on far earlier. So that said, if my IC water is never getting near 0 deg C, why do I and others have this stalling of the cooling with sudden re-starting or not re-starting at all, at all positions of the TX valve spring adjuster? I know the AC is still working when this happens as the cabin air stays cold. I have other orifices to try. The KC comes with the TX sensing capillary wrapped around the IC water outlet not the refrigerant outlet. Is that correct? Cheers.

sjc246

I can't tell you how it's supposed to be on the KC but you are correct that the sensing bulb is typically on the refrigerant suction line. With the sensing bulb on the coolant line, the TXV will go fully open whenever the coolant femperature exceeds the TXV set point. This could be by design but I would worry about flooding the evaporator (if you get too much liquid refrigerant in the evaporator, it can't evaporate). If the heat exchanger is big enough to always keep up with all the refrigerant it can get (txv wide open, compressor at full capacity, high rpm, and HVAC load low or off) this shouldn't cause any problems, but I'm not sure if that's the case. I would contact the manufacturer to find out if that's normal or if it was assembled incorrectly (you'll need to speak to someone in the engineering department, not a salesman).

trabots

Thanks again. If I double the volume of the evaporator by installing a second KC in series would that not decrease the chances of it flooding?

sjc246

I would think so. Just to be clear, we're only talking about a second heat exchanger, right? You shouldn't put two TXVs in series.

trabots

No, two evaporators in series but using the low pressure outlet of the second for reference to a single TXV on the high pressure side of the first. The KC vendor has done this on his drag car successfully. I understand that the phase change should be complete by around 2/3s of the evaporator length. If the TXV is closing on the single evaporator, the phase change is incomplete is it not?

sjc246

Evaporator and heat exchanger are the same thing. The generic term for that device is heat exchanger and in this particular case, the heat exchanger is being used as an evaporator. (I'm not talking about a water-to-air heat exchanger, if that's what you thought: it's a refrigerant-to-water heat exchanger.)

What you describe should work fine. Assuming the TXV is referencing the refrigerant temperature after the evaporator, the TXV closes because phase change is not complete (excessively cold temperature at the sensing bulb reduces internal TXV pressure and allows a spring to close the valve; warm temperatures at the bulb builds pressure which opens the valve against the spring). By restricting flow, the TXV ensures that less refrigerant enters the evaporator so that phase change can be complete. With a properly functioning TXV, it should regulate so that phase change is complete inside the evaporator; not necessarily 2/3, the exact location depends on many variables, but definitely before the end. Ideally, you want the phase change to complete just before the outlet of the evaporator, otherwise the rest of the evaporator isn't doing much of anything.

However, if the TXV is referencing the IC coolant temperature as you previously described, all bets are off because if the coolant is warm the TXV will stay full open, even if liquid refrigerant is exiting the heat exchanger ("evaporator"). If too much liquid refrigerant enters the evaporator, it can "fill up" and pressure will rise preventing complete (or, in an extreme case: any) phase change. The higher the pressure on the low-side, the higher displacement (higher output) the compressor, so it will force even more refrigerant through the TXV. Whether or not this happens will depend on the capacity of the evaporator: if it's big enough to allow for complete phase change even at max compressor output than this design would probably work ok, but I doubt that's the case (particularly if you are blocking flow through the HVAC evaporator). (I have never heard of or seen a device that references anything other than evaporator outlet temperature for the TXV. The entire point of the TXV is to regulate evaporator outlet temperature.)

trabots

That is the best info I have managed to receive on this subject. Thanks again. I will advise this thread the outcome of adding the second KC in due course.

trabots

I have now determined that my tx valve is supposedly closing at different temperatures. That is if it is the tx valve. I am getting the impression it is the compressor shutting down during operation due to the KC doing such a good job that even at the lowest possible cabin setting, a sensor is telling the compressor that the cabin is cold enough and disengaging. I suspect this is the case because the shut down occurs at different ambient temperatures and with my tank water varying from 2 to 7 degC when from that tank sensor I can see the temp increasing again.