ABC's of 80's Cooling Part III - Press Switch (1 Viewer)

[SUMOTOY]

ABC's of 80's Cooling Part III.5 - Hood Vents

Just an update on the Sumotoy 80 and a preamble to Part IV...
I installed the drivers side hood vent yesterday, and will be installing the PS today. Yes, I took pics of slicing up the hood for Part IV.

Unfortunately using the Z34 hood vents doesn't look to be a good avenue, I ended up using another type (not sure the app) that doesn't require rewelding of the hood frame. I suspect that the pontiac hood vents I saw posted here might be the 'other' set that could work.

I also put the vents a bit further forward than I really wanted, but I verified it's low pressure zone by driving around with yarn (matching green yarn specifically) on my hood trying to ignore the stares...

Sitting in the truck today with the A/C running, I noticed that welcome ripply hot air coming from the DS hood vent. I'm putting in the PS today, and will get ABC IV up with some data asap.

Scott Justusson
94 FZJ 80 Supercharged - half vented

 

[landtank]

Scott, we already have a few threads about hood vents. How about adding your info to one of those.

 

[stlcruiser]

Additional pics

Greetings:

Here is a straight on pic of the fan. No need to use zip ties. I did not want the fan resting directly on the condensor. Using existing mounting bracket from Mazda fan and spacer at bottum, I maintained a approx. 3/4" gap between condensor and aux fan shroud. Mounting is solid and retains the OEM look.

Power to fan is direct to second battery protected with a 25 amp inline fuse. No problem if using main battery. Used Sumo's intructions for wireing up relay and incabin switch. The incabin activation switch tapps into the wire at the preasure switch that leads to pin 86 on relay. (make sure of proper fan rotation when determining which wire off fan is positive and ground!).

After relizing the first lit switch I chose was LED where polarity matters went to a Toyota incandecent one as pictured from rallylights.com. Works flawlessly with light indicating fan activation in "automatic" mode and manual override mode. (Thanks Sumo for the lesson in polarity)


Steve
94'
160,000

 

[SUMOTOY]

Scott, we already have a few threads about hood vents. How about adding your info to one of those.

I thought about using 'Da Hood' thread started by Photoman, but it wanders a lot Rick, and ends up hijcacked with pics of guages. I'm sure many will excuse a new thread in my ABC format. Anyone is welcome to combine them all into something more encompassing if they so choose.

I put the PS vent into the hood in under 30 minutes this afternoon, and did a quick measure of temps coming out the vents, ambient +35-50F at idle. And much more than expected during passive, er free convection, with the truck off.

I suspect with the truck moving it's doing much more, and the improvement to tip in throttle with the SC is noticeable.

Cheers

Scott Justusson
94 FZJ80 supercharged mit vented hood

 

[SUMOTOY]

Nice find,

Just got out a mirror an indeed there are 4 pins on the switch, neither the FSM nor EWD for my 96 make any mention of this third contact in the switch,


I wonder if this is where the condenser fan (CDS FAN) found in other markets gets its input from?

I suspect that is the case, and that it's been an 'option' for quite some time. That pressure circuit is clearly listed in my 93-93 FSM in the A/C section, but not used in the wiring diagram.

Nice too, that Mr. T left the plug for us all, so that in a couple minutes you have a water tight set of pigtails for your wiring pleasure.

SJ

 

[citadel]

any reason you decided against Z34 vents? I purchased 1 passenger side vent with drip pan and just had it painted to match the truck.
How tough is the install?

 

[SUMOTOY]

any reason you decided against Z34 vents? I purchased 1 passenger side vent with drip pan and just had it painted to match the truck.
How tough is the install?

I saw that one for sale too... It can be used, but only in line with the HVAC vents or really far forward on the hood outbound of the hood bump. To put it on the outside of the HVAC in the back of the hood you will need to reinforce the hood somehow. If you already painted it, I'd put it dead center between the windshield squirters. Or you can put that vent up on ebay, and get what you paid for it citadel...

Since I have a plethora of hood vents available in my shop, I just grabbed the set that had the least work involved in installation. I've modded hood frames, and it isn't fun. And I almost went for the quater panel vents instead, but got good low pressure zones 18in forward of the rear hood line....

I'll post up pics of my install in ABC IV new thread. With A/C on and aux fan running, I got a peak of 70F over ambient parked with the engine running. I'm most pleased with that number.

More to follow. If you didn't paint it a wild color Citadel, I'm sure I can get rid of what you have to the audi boys...

Scott Jususson

 

[Tools R Us]

My main concern is on a 115F day which is what prompted me to check the temperature earlier, how often and long will the aux fan run with the engine shut off? I measured the condenser temperature from another truck that has been sitting for more than a week, the condenser temperature is 103F, 8F higher than ambient. I am trying to avoid draining the battery on a 115F day.

My truck parks in the sun at the shop and most of the time I bring the remote temp displays in a put them on the desk. It's not uncommon to see 120F+ underhood and 140F+ interior temps. I doubt that the fan would run all day, probably cycle on and off. Just add a switch to turn it off when parked, or trip the relay with the compressor so the fan only runs when needed. Better yet mod the fan clutch, then you wont need the pusher.

 

[medtro]

My truck parks in the sun at the shop and most of the time I bring the remote temp displays in a put them on the desk. It's not uncommon to see 120F+ underhood and 140F+ interior temps. I doubt that the fan would run all day, probably cycle on and off. Just add a switch to turn it off when parked, or trip the relay with the compressor so the fan only runs when needed. Better yet mod the fan clutch, then you wont need the pusher.

Thanks for the data. Agreed, but I am trying to have the afterrun cooling feature. Which fan clutch mod are you referring to? Landtank boiling mod or the thicker fluid mod?

 

[SUMOTOY]

Thanks for the data. Agreed, but I am trying to have the afterrun cooling feature. Which fan clutch mod are you referring to? Landtank boiling mod or the thicker fluid mod?

Medtro:
Use an ignition trigger for the relay activation if you have any concerns about afterrun. I would not compromise on the ground thru the pressure switch. The problem with compressor clutch activation is that if the compressor is off so is the fan. Including an overheat or overpressure compressor shutdown mode. With the pressure switch mod, with both those compressor shut down scenarios, the aux fan is running when it's needed the most.

SJ

 

[landtank]

Currently I don't see me installing this mod but if I were to consider it I wouldn't be wiring it the was Sumotoy is suggesting. I'd sooner look into using a DPST relay, using one set of contacts as a timed latch circuit so reguardless of the temp the fan would shut down within a predetermined time, say 5 minutes after shutting off the truck.

 

[landtank]

Maybe this was covered in parts 1 or 2, I don't know, but start with the basics like making sure the foam seals between the radiator and condensor are in place and in good shape. Also as Tools mentioned be aware of the fan clutch. We are driving a mechanical fan with a 212 HP motor, I don't see where using a 12v fan is going to bring a whole lot of magic into a system where the stock fan is operating properly. CDan saw issues with his modified clutch where the auxillary fan had no effect at idle, only opening the hood helped. If you stock fan is moving so much air that it's restricted by the amount of air that can exhaust the engine bay then I can't see the aux. fan helping.

 

[clownmidget]

There's no room for an intercooler with that fan and your tranny cooler up there!

I've found with just the intercooler in front of the a/c condensor and radiator I've got no issues with cooling - either the engine or the a/c.

Are there any specs on this fan in terms of air flow, amp draw, etc.?

 

[SUMOTOY]

Currently I don't see me installing this mod but if I were to consider it I wouldn't be wiring it the was Sumotoy is suggesting. I'd sooner look into using a DPST relay, using one set of contacts as a timed latch circuit so reguardless of the temp the fan would shut down within a predetermined time, say 5 minutes after shutting off the truck.

I work with those failures in the audi turbo quattros all the time. The biggest problem with DPST relays is that they generate a lot of heat, and when they fail, it's usually the timer circuit, and they drain the battery. My suggestion is to try it with the after run circuit hooked up, and time your 'worst' case day. IME, it won't run long.

If your worst case day exceeds 115F, drop the after run, it only requires you hook up the positive relay trigger to a ignition source.

I highly recommend that one keep this circuit as simple as possible. You can complicate it if you like, not my intention or design. It's not a issue to even address until someone tries it and reports. Fixing it requires a simple 12v+ relay trigger from direct battery to ignition. Hardly a monumental hi task. Nor is the primary focus of using the medium pressure switch for ground altered; after run or no.

Tough crowd

Scott Justusson

 

[SUMOTOY]

Maybe this was covered in parts 1 or 2, I don't know, but start with the basics like making sure the foam seals between the radiator and condensor are in place and in good shape. Also as Tools mentioned be aware of the fan clutch. We are driving a mechanical fan with a 212 HP motor, I don't see where using a 12v fan is going to bring a whole lot of magic into a system where the stock fan is operating properly. CDan saw issues with his modified clutch where the auxillary fan had no effect at idle, only opening the hood helped. If you stock fan is moving so much air that it's restricted by the amount of air that can exhaust the engine bay then I can't see the aux. fan helping.

Rick:
In parts 1 and 2, I address the benefits of cooling the ocndenser with an aux fan. If the primary task is to increase total cooling capacity, IMO, you are wasting your time. Blowing cold air on a condenser with a mechanical fan is the modus of Volvo, Mercedes and saab. I didn't see a decrease in engine temps, but I did see a significant increase in underhood temps with the aux fan. Which makes sense, since I have appeared to have increased the efficiency of the condenser which should be a measure downstream.

This also applies if you change the fluid in the clutch = more underhood trapped heat in traffic vs stock fluid.

Making sure the foam is in the radiator, and air is sealed around the radiator are baselined in other threads, but good advice. So is IDoug's suggestion to clean out the rad and condenser from the back side with a garden hose.

In the meantime, hood venting is an excellent way to alieviate the high underhood temps now trapped under the hood. IMO, it's the best cooling mod I've done to date in terms of noticeable driving improvement. I even like a bit more of that supercharger whine coming thru the PS vent

Scott Justusson

 

[landtank]

The biggest problem with DPST relays is that they generate a lot of heat, and when they fail, it's usually the timer circuit, and they drain the battery.

I was going to respond, but not worth thr trouble.

 

[Tools R Us]

...

This also applies if you change the fluid in the clutch = more underhood trapped heat in traffic vs stock fluid.
...

Scott Justusson

Where is this "data" from? On my rig all of underhood temps, along with every other measured temp fell big time with the upgraded fan clutch. I don't see this trapped heat theory there is very good airflow under my hood.

 

[SUMOTOY]

116 ambient need apply

I was going to respond, but not worth thr trouble.

LT:
After run is quite secondary to the primary function of using the pressure switch ground circuit on relay activation. I chuckle a bit at all the concern regarding the after run circuit. Simply hook up the 12v+ (pin 85) relay activation feed to the ignition, fan runs with 3 conditions met:
Ignition switch on
A/C climate control activated
A/C pressure above 192psi

If 'after run' is desired in my hookup scenario, ambient temps would need to be less than 116F. If it's *really* desired to have after run, and ambient temps are above 116F, you could certainly add a timer circuit to the relay. IME with timed relays, this dictates that the relay not be mounted under the hood, which means you are stringing a *lot* of high guage cable to get a convenience feature.

I propose a much simpler solution of adding a switch in the pin 85 12v+ feed circuit, that allows 12v+ from battery power in one position (after run), and ignition power in the other position (no afterrun - temps above 116). This allows one to use the same 4 pin standard relay.

Your method will certainly work, I say it adds a lot of inconvenience for a convenience. It's a moot point, as very few have done the pressure switch mod yet. The primary/targetted benefit in doing that mod is to retain fan function during overheat compressor shutdown. The incidental benefit is the *ability* to have an afterrun feature. Hardly necessary.

Scott Justusson

 

[SUMOTOY]

Where is this "data" from? On my rig all of underhood temps, along with every other measured temp fell big time with the upgraded fan clutch. I don't see this trapped heat theory there is very good airflow under my hood.

TRU:
This data is not unique to the 80. You might see 'some' decrease in underhood temps with a thicker fluid, but by definition you won't when the fan isn't engaged. Your own data showed air filter temps higher than ambient under heat soak. Air Density is free power! The closer you reduce the air temp to ambient the better.

Cdan did exactly the hood vent experiment. Measure underhood temps with the hood closed, then open it. I was just at the track last Friday, and commented to a buddy on a couple 280Z with the ultimate hood vents, they just removed the hood!

I don't need to convert anyone here. Those that have done hood vents know the benefits. There is no question in my mind, more will do them, it's part of effective heat management. You can push the air harder, or release the air more efficiently, or both. I have done both, and the difference in driveability with the vents installed was immediate and more dramatic than adding 10k fluid.

You certainly don't need to believe Kevin. I've done them on dozens of cars and trucks, and think this forum needs to shift the paradigm in heat management. In fact, LT has a pretty old post regarding flow in 'Da Hood' thread Photoman put back up just this am. I agree with the principles of trapped heat theory he presented, and took action on it.

Scott Justusson
'94 FZJ80 supercharged and vented

 

[flintknapper]

This is a non invasive procedure, you are not pulling the pressure switch only the connector to it. You are NOT opening the A/C system.

The pressure switch is the only electrical connection in the A/C circuit. Yes, on 94> it is located in front of the battery on the Drivers side.

I'm working on getting pics up which will help.

Scott Justusson

I know this is an old thread....but does anyone know if we got pics. on this. I searched and didn't find anything.