Adding 3 fans to rear A/C condenser - Page 3

mthomas58 · 11-07-2006, 05:46 PM

Yes, Told him exactly what I had in mind and he thought it would be fine. BTW my condenser is brand new OEM Porsche at $750 vs non-OEM's at $300 (mechanic could not find one with fittings that lined up properly with hoses & brackets). Hopefully, the price is indicative of a better quality and will hold up better.

Jim Sims · 11-07-2006, 06:16 PM

It's sort of a moot issue now but the strengthened, triple pass 911 condensers Scott's Performance Aire sells look a lot like that OEM one; they're ~ $450 each:

http://www.scottsind.com/Navigation/MastercraftAC/Mastercraftacframe.htm

Installed Performance Aire 911 aftermarket condenser:

mthomas58 · 06:04 AM

Fan Project Update:

Well, I worked on the fan project today. Unfortunatley, I was a little too ambitious in my planning and was only able to fit one of three fans on the condenser. Not enough clearance above the heater tube or the alternator fan shroud

.

I'm going to play around with it some more and may get one addl fan to fit...or order a smaller fan to fit above the alternator. No clearance above the heater tube at all.

In any event, the fan mounted easily with the nylon push throughs, although it was necessary to unbolt and lower the condenser. I installed a relay in the engine compartment to control the fan and wired it to the A/C compressor to turn the fan on and off automatically whe the A/C is running.

Wiring of the fan was a b*tch because of errors on the wiring diagram that came with the relay but I was able to get things figured out after a lengthy troublshooting process.

The spal 7.5 "pull" fan that I used is rated at 440 CFM. I was pleasantly surprised with the amount of air that it moves! I think this is going to be a great addition to the A/C system.

Nylon push through ties worked nicely.

Had to remove center fan after test fitting

Very clean & easy installation

Fan relay...pic is before I connected power through the lower fuse (rear wiper/ defroster 25 amp fuse)

mthomas58 · 11:22 AM

Follow-up. Fan working nicely. Very faint fan motor noise can be heard in the cabin - positive feedback that it's working

Considering adding a TDR to allow the fan to run for a minute or two after shutdown to assist engine cooling. More here:

cooler carrera

(BTW, it's an old post......Scott has sold his 911 and no longer has the wiring diagram)

911pcars · 02-22-2007, 03:20 PM

Mark,
Installation looks clean. Congrats.

"Considering adding a TDR to allow the fan to run for a minute or two after shutdown to assist engine cooling. "

RE: to piggyback on your timer idea. Since heat normally rises, I think it'd be more efficient to reverse air flow after shutdown. Since the fans are powered by a DC motor, they are potentially reversible by changing polarity (+&–) - check w/Spal. That way, the fans can help evacuate hot air from the engine much like most imports continue blowing air over the radiator after engine OFF. I'm pretty sure they use a thermal relay rather than a timer.

FWIW,
Sherwood

Hladun · 02-22-2007, 05:04 PM

Quote:

Originally posted by scottb
I'd love to see some empirical data on whether fans on the rear condenser actually help. Some on this BBS swear that they help. I'm skeptical.

Fans on the rear condenser do help a lot. I did an A/C installation several years ago. Do a search on my name.

Contrary to popular belief the engine fan doesn't move very much air. As I recall max air velocity through condenser is <5 mph with engine fan alone.

mthomas58 · 02-22-2007, 06:01 PM

Hladun, I think this is the post you are referring to.

'74 911 a/c upgrade

Reading through it reminded me that on my install, I did have to remove the airbox horn in order to get my fan to fit. Did some more measuring tonight......no way to get another 7.5" fan to fit on the underside of the condenser, BUT, I think one or two 4" fans will clear the alt fan housing and heat duct.

http://www.spalusa.com/fans/automated/motorcycleatv_4_paddle.html

At 124 CFM each, the addition of two 4" fans would increase my supplemental airfow to 688CFM from 440CFM - an increase of 56%! As I sit here remembering sweating my a$$ off last summer before getting my system functioning, this sounds encouraging. I was and still am obsessed with improving the performance of the stock A/C system.

Hladun · 02-22-2007, 07:02 PM

Here's a picture of my installation:

1990 911 Air Conditioner

Keeps car cool in 90F+ with no other condensers.

mthomas58 · 03-01-2007, 08:36 AM

OK, after remeasuring and test-fitting I can add one addl 5.1" fan (313CFM) and one addl 4" fan (124CFM) to my rear consenser bringing the total CFM up to 877 - an increase of 100% over the single 7.5" fan.

Ordered new fans yesterday. I've now got two extra 7.5" fans rated 440CFM from my original plan that I'm not going to use. I'll let them go for $40/shipped (each) if anyone is interested. (I paid $53/each).

Looking forward to a cooler summer!!!!!!!!!!!!

derkpitt · derkpitt's Garage

Mark, save one for future replacement of the front oil cooler fan.
And I'll take the other.

mthomas58 · 03-12-2007, 08:12 AM

Derk, good idea on saving the fan to relpace the oil cooler fan. Finally heard it kick in in a traffic jam last week - nice to know it works. I gotta think the Spal moves more air than the OEM cooler fan.

Just sent you a PM on the extra fan.

Elu · 03-12-2007, 02:16 PM

I did the exact same thing, except I added 2 fans. My mechs have said time and time again that they can't believe how cold a stock AC can be. Well it's not exactly stock, but it really does work.

Here was my thread:
I did it too...Pro Cooler Mod for my A/C

mthomas58 · 03-20-2007, 08:27 AM

Project Update:

Received the two addl fans for the rear condenser and a time delay relay last week, but, due to an evap freeze up - I got a little distracted this weekend and diverted my attention to cleaning the evap coil and box and added one of the new fans to the passenger floorboard as a blower assist at the evap intake port/resistor pack. Details here:

Thread:
Evap assist fan install in floorboard

Got vent temps of 34-35 today with rapid temp drops when the compressor, rear condenser fan and evap assist fan were all running - AT IDLE. I realize that the true test will be at ambient temps of 90+ sitting in traffic (not too far away) but the initial results are encouraging.

I've now got to order another 4" spal fan to replace the one I used in the footboard. The 5.1" and 4" fans yet to be added to the rear condenser will move an addl 427CFM to the 440CFM already installed.

I'm never giving up!

mthomas58 · 02:55 AM

Couple of pics with two fans installed (7.5" and 5.1"). I'm holding off on the third for now since the system is working so well after cleaning out the evaporator and adding a fan to the evap intake in the passenger footwell.

Link to my performance results to date here with encouraging vent temp data:

Vent temp update: I think I'm gonna survive this summer!

scottb · 04-02-2007, 03:22 PM

Mark: Maybe I missed it earlier in this long thread, but are your fans "pushers" or "pullers?" I'm guessing "pullers" since you'd want them to work in sync with the engine fan, but I'm checking to be sure.

Nice work!

mthomas58 · 03:46 AM

Scottb, you are correct, they are pullers.

Thanks!

SCWDP911 · SCWDP911's Garage

sub'd. good thread for those of us in the humid south

shbop · 04-02-2007, 08:05 PM

I recently routed a 10 ga. + to the back via the a/c lines under the driver's side. I went into the cabin through an existing grommet, then out the upper door jam grommet, finally down and through the rocker. Since this car is running relays on the headlights, fan booster, and some other stuff, I ran a fuseable link wire to a central terminal up front by the fuse box. From that point, I pull to the various components that are relay operated, including the rear power supply. All power lines begin with another fuseable link.

Hladun · 04-03-2007, 02:29 PM

It's nice to see that the solution I proposed more than 5 years ago is now gaining popularity. You just can't beat A/C on a hot day and it's a shame that for 20+ years the solution was to tear the system out and sweat!

rnln · 04-15-2007, 12:45 PM

mthomas58,
I wonder if you can get 7.5" pusher fans and install them on top of the condensor? Assuming you have whale tail.

Quote:

Originally posted by mthomas58
OK, after remeasuring and test-fitting I can add one addl 5.1" fan (313CFM) and one addl 4" fan (124CFM) to my rear consenser bringing the total CFM up to 877 - an increase of 100% over the single 7.5" fan.

Ordered new fans yesterday. I've now got two extra 7.5" fans rated 440CFM from my original plan that I'm not going to use. I'll let them go for $40/shipped (each) if anyone is interested. (I paid $53/each).

Looking forward to a cooler summer!!!!!!!!!!!!