Custom AC project - general feedback and condenser selection

[bond007]

Project:
Custom AC installation in a 1993 Mazda RX-7 with non-standard components and non-standard heat exchanger orientation aka "V-Mount" radiator and intercooler.

I've machined custom mounts for a variation of the NipponDenso SCSA06C compressor. I had a slow leak in my original one/previous iteration of this configuration and suspected the original compressor was leaking/needed a rebuild, so I figured might as well move to something designed for R-134a. Hopefully, this compressor isn't going to be a step backward, as it is much smaller than what was in there and I should have picked something else.

Q1: Request for comments on this compressor before I get too much further into building stuff. This is a small 2-seat sports car cabin. It seems like it should work for my use case from the other listed applications in the ND catalog that have used it.

Q2: Is there a source for generic compressor pad mounts/line components aside from OEM lines for this compressor? I see some pieces that adapt from something that looks like this pad to standard #6/8/10.

I would like a condenser that covers the entirety of the custom radiator I'm building as a sacrificial part for any potential impacts from hard road debris. The car will see usage at road racing circuits. I'm not getting any younger, so, having a cool cabin while waiting on the grid for my track session is getting to be less of "tough it out, buttercup" and being smart about having a less tired driver (especially when wearing a driving suit for fire protection)...

Some folks seem to use the RX-8 condenser but I have 16"x28" of radiator core that I want to protect, which looks like it might leave me about 2" unprotected with it being 14" tall. I also figure that having a larger condenser would help, as some say the RX-8 AC can be anemic when it gets really hot (2" taller is 15% more surface area).

Q3: The NipponDenso AC component catalog shows condensers with the dryer integrated as having a "supercool" section. Is there a significant efficiency/advantage of this design over a standard parallel flow and an external dryer (I have room to fit but it adds extra plumbing work)? I've found a 16x24" generic dryer integrated condenser I could use, but I'm trading some potential condenser surface area for the integrated dryer...

[tbirdtbird]

I can’t answer all your questions, but you need to fit the largest condenser you can possibly fit. The condenser is how the heat from the cabin is given up.
Other consultants will be along with more comments.

[bond007]

I can’t answer all your questions, but you need to fit the largest condenser you can possibly fit. The condenser is how the heat from the cabin is given up.
Other consultants will be along with more comments.

Thanks for your thoughts.

Yes, that (fitting the largest condenser) is central to my third question. The original OEM condenser is 12x24 at best and everything I am considering has the goal of filling the available area due to the revised V-mounting layout.

It’s small nose compared to a domestic / classic. I have 28” between the frame rails which means 27.5” is what will practically fit but leaves no room for normal plumbing of #6/#8 on the ends. A pad mount would definitely help. I don’t see generic condensers using those, so it seems like to maximize surface area, I would need to pick a OEM that uses pad mounts that are on the top surface instead of the sides.

Any suggestions or a catalog with dimensions of OEM? Some aren’t viable due to the plumbing being way out to the side instead of streamlined on the “end tanks”.

FWIW, the small original OEM worked okay when mounted this way in a prior iteration of this design but I’m in this to do it “one last time” unless I can’t use this layout because I swap in a 3-rotor.

[DetroitAC]

Condensers can have additional subcooling passes built in after the integrated receiver/drier. It creates a bit lower enthalpy at the condenser outlet, and is a better use of the condenser fins/tubes, all things considered.

It's not a big effect, just a sensible improvement, with no real increase in cost or weight. I'd say nearly all current USA OEM R1234yf condensers will be IRD/subcooling types.

[tbirdtbird]

Always good to see you, Detroit….

[JohnHere]

I've machined custom mounts for a variation of the NipponDenso SCSA06C compressor. I had a slow leak in my original one/previous iteration of this configuration and suspected the original compressor was leaking/needed a rebuild, so I figured might as well move to something designed for R-134a. Hopefully, this compressor isn't going to be a step backward, as it is much smaller than what was in there and I should have picked something else.

Just because the case looks smaller doesn't necessarily mean that the displacement is less. It would be interesting to compare the displacement of the original compressor to the new one if you can find the specs for both.

Q1: Request for comments on this compressor before I get too much further into building stuff. This is a small 2-seat sports car cabin. It seems like it should work for my use case from the other listed applications in the ND catalog that have used it.

It probably will work if the displacement specs are close enough. Are you using the original Wankel rotary engine in this car?

Q2: Is there a source for generic compressor pad mounts/line components aside from OEM lines for this compressor? I see some pieces that adapt from something that looks like this pad to standard #6/8/10.

Check with Cold Hose in Florida. They might be able to help you out with that.

I would like a condenser that covers the entirety of the custom radiator I'm building as a sacrificial part for any potential impacts from hard road debris. The car will see usage at road racing circuits. I'm not getting any younger, so, having a cool cabin while waiting on the grid for my track session is getting to be less of "tough it out, buttercup" and being smart about having a less tired driver (especially when wearing a driving suit for fire protection)...

Some folks seem to use the RX-8 condenser but I have 16"x28" of radiator core that I want to protect, which looks like it might leave me about 2" unprotected with it being 14" tall. I also figure that having a larger condenser would help, as some say the RX-8 AC can be anemic when it gets really hot (2" taller is 15% more surface area).

Two inches isn't much (1" top and bottom), but it would be nice to find a condenser about the same size. Vintage Air and/or Old Air might be able to help.

Q3: The NipponDenso AC component catalog shows condensers with the dryer integrated as having a "supercool" section. Is there a significant efficiency/advantage of this design over a standard parallel flow and an external dryer (I have room to fit but it adds extra plumbing work)? I've found a 16x24" generic dryer integrated condenser I could use, but I'm trading some potential condenser surface area for the integrated dryer...

As far as I know, there's no advantage of the integral design over the separate R/D other than packaging. I'd say do whatever works best and that will be the least amount of work.

[bond007]

Just because the case looks smaller doesn't necessarily mean that the displacement is less. It would be interesting to compare the displacement of the original compressor to the new one if you can find the specs for both.

OEM is a TV14C (rotary compressor type):
Capacity: cm^3/rev {cu in/rev} 138 {8.42}
3900 kcal/hr
Receiver/dryer capacity 274 {16.72}

This was an R12 system. They were required to use R134a the following year(s) it was imported in 1994 and 1995. I don't see that the components were changed, just the fittings on the lines. The R12 condenser was already parallel flow. It worked okay and has been run on R134a for many years.

SDSC06 (scroll type) and these are the RX-8's documented specs but I'm not using the RX-8 version of the compressor to be able to run a 6-rib belt:
Discharge capacity (ml {cc, fl oz}) 60 {60, 2.03}
Radiated heat (kW {kcal/h}) 7.0 {6,020}
Receiver/drier capacity (ml {cc, fl oz}) 190 {190, 6.42}

So, less than half the discharge capacity, less R/D capacity but 50% more radiated heat?

Q: Are you using the original Wankel rotary engine in this car?
Yes. The only different engine ever going in this car would be a 3-rotor instead of the factory 2-rotor Wankel.