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Good working AC setup

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Old 02-08-18, 08:16 AM
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Good working AC setup

With the summer approaching in the near future Id like to start to tinkering with my AC system soon.

Who has a good working AC in your FD and what is your setup, for example SMIC and stock AC configuration or VMIC. PFC, Haltech, Adaptronic or stock ECU. Do you have a fan on your condenser?

Good working means, strong fan speeds temps below 40 degrees when its 95 degrees out.
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Old 02-08-18, 10:40 AM
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I'm the original owner of a completely stock 1994, with about 40k miles. From new, the air conditioning was always adequate even for desert runs on the highway. I was quite satisfied until one summer when I found myself stuck in Phoenix rush hour traffic (just one additional reason not to go to Phoenix in the summer.) Think about it, those air conditioning lines are running 4 inches from the turbo chargers which are cooking away at over ~600 degrees, one of the lines is bare aluminum. Mazda engineered the car for Right Hand drive where the AC lines are on the other side of the engine compartment which is not nearly as hot as the turbo side. So, I figured we had to rectify that engineering oversight. The biggest improvement to my stock Mana air conditioning system was insulating all the air conditioning lines in the engine compartment with silicone pipe insulation from McMaster-Carr. I slit the silicone pipe insulation and slipped it on to all the air conditioning pipes and hoses. Once on, I used silicone adhesive to glue the slit back together and used high temperature Tefzel cable ties to hold it while it was drying. In the end I just left the cable ties in place after the silicone adhesive dried. Now the air conditioning works like a champ under all conditions, although you won't find me in Phoenix in the summer again.
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Old 02-08-18, 11:19 AM
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yea i did something similar I cut a slit into some hoses and put reflective tape on the outside. Didn't really help me though.

My setup
  • Single turbo with no turbo blanket
  • DP wrapped
  • Blitz FMIC
  • no fans on the condensor
  • PFC

AC worked "ok" with adaptronics but i can't get the fan speeds 3 and 4 to work now that i'm on a PFC. Haven't tried adding a relay yet.
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Old 02-08-18, 11:46 AM
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First off, the AC system in the FD stock works REALLY damn well. My car when it was new with R12 in it would freeze you out of the car - 34 degree air coming out of the vents.

The big trick with a front mount is getting the condenser mounted where it can get good airflow. Ideally you want it similar to stock - the condenser is right in front of the radiator, like a half inch air gap between the two, so when the fans on the radiator run they pull air through the condenser.

I have a Blitz FMIC as well and my AC has always been so-so, but it could be due to many other factors.

I don't know if a secondary fan will help that much. FC's actually had an electric pusher fan in front of the condenser, but I think that was due to the clutch fan the FC had. The pusher fan let it increase airflow when the clutch fan wasn't pulling enough.

That said, most pusher fans end up being a restriction to airflow more than anything. You could put a fan on the back side, but that starts becoming a packaging mess. Also, pretty much all aftermarket fans I've ever worked with are crap - super loud, crappy wiring, so-so airflow, etc. They cause WAY more problems than they fix and will typically fail in some fashion or the other in less than a year.

Refrigerant is also a big factor. On an FD I'd either dig up some new unused R12 or use Dust-Off (R152A). There's a HUGE thread in the FC forum about using Dust-off, I've used it in other cars and it works awesome. R-134a will get COOL, but never COLD, in an FD. You can get it running cold for a short time with an overcharge but it's a time bomb.

The other big problem is the receiver/dryer. If you have a Nippondenso factory installed system, you're good. The MANA system has no easy route - either do a custom drier and lines or get the MANA drier rebuilt. Supposedly there are hot rod shops that will cut open old driers, put in new desiccant, clean, weld together, and paint. No idea on cost.

For my buddy Jon's car we're going to try running an RX-8 AC condenser which has a built-in drier. It's going to be more fab work - some custom lines and brackets - but that condenser is pretty cheap new and you can replace the dessicant bag in the assembly down the road if you have to.

Oh, also, with regards to V-mounts, the condenser needs to be fairly straight up and down and not laid down flat. The condenser has an input and output, and the input needs to be up top, output at the bottom. The refrigerant is actually condensing in the drier and you want the liquid to settle to the bottom to be sucked into the compressor.

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Old 02-08-18, 12:40 PM
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To over state the obvious, without good air flow across the condenser there is no hope of achieving an efficient air conditioning system. I'm sure you know the FMIC exacerbates the problem by heating the air before it even gets to the condenser. As far as the insulation project, the thermal conductivity of neoprene rubber is 0.19 w/m K the conductivity of expanded closed cell silicone insulating sponge is 0.08 w/m K. As you have demonstrated a simple insulation job will not fix your problems. If your serious about empirically measuring the improvements of modifications to your AC system the Body Electrical Trouble Shooting guide (page G47) and this pdf, which is a good summary on how to diagnose and measure improvements in efficiency, is a good start. I would take special note of page 18 #5 which is one of your problems and page 23 which explains why the air conditioner isn't working at top efficiently with this problem. Using an AC gauge and the Sanden AC Trouble Shooting Sheet you will be able to directly measure the effects of any improvements, modifications, or repairs you make. If your air conditioning has been serviced sometime in the last 20 years there could be several problems you are dealing with. Start by measuring the pressure and calculating saturation temperature with the gauge, then get the cooling fans working, measure and calculate again to see the improvement. If the measurements point to other problems get those fixed too. After getting everything in top working order you can start making and measuring improvements to the system like insulating the hoses and tubing.

Last edited by mdp; 02-08-18 at 01:22 PM. Reason: corrected shop manual page number
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Old 02-08-18, 12:52 PM
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Yea I've only used Dust off for the refrigerant on the cars. Both of the FDs i have are 93 touring models, so I'm not sure what system i have.

The MB has VMIC setup and it's laying fairly flat so that's probably part of the problem.

Both condensers are right on the radiator.

Thanks for the info mdp, will have to give that a good read.

If a stock system worked well, i'm assuming a SMIC setup would work well also?
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Old 02-08-18, 04:22 PM
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Originally Posted by DaleClark View Post
Refrigerant is also a big factor. On an FD I'd either dig up some new unused R12 or use Dust-Off (R152A). There's a HUGE thread in the FC forum about using Dust-off, I've used it in other cars and it works awesome. R-134a will get COOL, but never COLD, in an FD. You can get it running cold for a short time with an overcharge but it's a time bomb.
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Here is a journal article comparing R152a and R134a in an automotive application. After careful reading you should be able to make an informed choice based on the data.
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Old 02-08-18, 07:16 PM
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Stock system is the result of millions of dollars of R&D, and impossible to beat. Seriously...no fan(s) on the condenser? That alone is gonna kill you.
My A/C works decently well, I've measured ~40 degree air coming out even on hot days, but the fairly large 'greenhouse' of the car (big front and rear glass) combined with black dash (on most cars I've seen) means hot Kansas summers see me keep the car in the garage. Tinted windows will help some, but overall the system, in my opinion, simply lacks the capacity to cool well in extreme conditions.
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Old 02-09-18, 10:12 AM
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If the cars are tourings, most of them have the Nippondenso system with the silver receiver/dryer that's easy to get your hands on. Most auto parts stores have them in stock for like $20.

The big for-sure test is if the bracket that holds it to the car is a clamp that clamps onto the drier. The MANA had a welded on bracket.

Here is the mega-thread on R152a -

https://www.rx7club.com/1st-gen-arch...gerant-997918/

Anything from Jackhild59 is worth careful reading. Buried in there somewhere is the amount of refrigerant, you need 12-13oz for an FD. It's best to fill by weight as it's more accurate.

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Old 02-09-18, 10:19 AM
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On my greddy v-mount setup, the condenser wasn’t receiving enough cool air from the mouth of the bumper. It was both flowing straight through the radiator and intercooler. I was receiving warmer air temps then stock side mount intercooler location and vertical condenser, Unlike the v-mount condeser location. Installing a brand new compressor and ensuring all lines were rebuilt, I still experienced the same issue. I installed a low profile 800 cfm spal electric fan and had it mounted on top of the condenser to pull in some of the fresh air from the mouth of the bumper and that helped a bit. But my sacrifice of where the hot air was now being drawn from and pushed to was onto the intercooler itself. I saw rising air temps sitting in traffic in summer and temps were not dropping as fast as they used to when driving/sitting.

My my next step was to insulate cracks around the vmount air dividers which I did and saw little improvements. I was going to buy a radiator cooling plate, the one that mounts on top of the bumpers aluminum mounting points to the support core to see if I can improve on air control effieicency and wasn’t able to do any findings after my accident.

My next thoughts at the time was to steal cool air going to going to the vmount and blow towards the radiator where the majority of the fresh air is running through.
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Old 02-11-18, 02:55 PM
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Bump, no one has a good working AC on these 25 year old cars?
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Old 02-12-18, 08:16 PM
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Only good ac setup that i have ever experienced in an FD is fairly stock setup fd . thats with SMIC and orignal configuration.
ive felt ac with fmic fd and vmount fd none felt like the smic fd all were very good and well sorted. Just not AS good as the smic fd with ac
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Old 02-13-18, 07:50 AM
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^ thanks for the info, I'm considering getting a greddy SMIC.
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Old 02-13-18, 10:31 AM
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I think it's possible to have good AC with a front mount. I think if you opened up part of the belly pan and maybe had a panel bent down to help scoop fresh air up towards the condenser/radiator you'd be in good shape. One of the things in the LONG list of stuff I'd like to do with my car once I finish a bunch of other projects first.

Most V-mounts have the condenser in open air in front of the radiator so it should get good airflow.

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