Griffith's fender condenser dimensions

[Dennis Kalma]

That picture captures the need completely (that is the white pre-'74 car). Basically on the later cars, the battery bulge gets in the way, that is why I am cutting mine away, fitting the smaller battery and getting a fit similar to that picture.

BTW, the C2 has a very similar layout and orientation, with the added airflow benefit of having a bit of a cutout in the front trunk wall and nearby inner fender which makes a bit of a duct into the condenser. I am not even going to try to replicate that, but rather I will just ensure that the bumper has a cut out in it to admit air and probably depending on the fan a bit more than waht the C2 needs....

Dennis

[niner11]

Charlie, thanks for the info and please keep it coming. I have been collecting parts (964 condenser, procooler, vents, evap, etc..) for about a year and when it gets cool in the fall I'll be brave enough to install it all on my 82SC.

I have seen kits for sale that block off a number of smaller vents and apparently send more flow to the "bowtie" and center vents. Wondering if you have tried anything like this. Thanks.

[kuehl]

I've got an old c2 condenser/fan assy. sitting underneath
one of the work benches, I'm wondering what it is worth.

Yeah, I've seen something peddled on in one of the aftermarket catalogs. Frankly I never reviewed it as we never viewed the air flow problem in that manner.

I may be repeating my self, last night was a Becks night, I'll have to use the spell checker here:
As you know one of the problems with the pre 964 cars was a/c vent air flow volume. You have the primary vent in the dash above the radio which gives some good yields. Prior to 86, factory air cars used the two slotted vents on the left and right along with the bow tie. In 86 they englarge the side slotted vents for more air flow.

A friend approached us years ago and wanted a better solution for the bow tie. He drove up with a 86 which had a vacuum formed double vent layed over the bow tie outlet. Apparently someone designed a fairly good solution years ago however the client complained of three things with the product, a) he had to drill through the bulkhead into the distribution plenum, b) though the product had two directional two, the location or placement of the vents were difficult to reach, and c) he felt the location somewhat restricted air flow.

Though there were several ways to skin the cat to speak the center 911 Kuehl vent we developed is a good "overall" approach with respect to ease of installation, function/performance and looks. Is it expensive? We'll that is all in the eyes of the beholder. If you have "free" time on your side and you like to tinker, then finding parts here and there is less expensive in terms of the material side. If you want something you can simply "plug and go", the product is well worth it.

Subsequent to the center Kuehl another client with a pre 86 model demanded more air and we mentioned increasing fan speed. With the greater velocity in the vent system he did not want the noise. So we focused on trying to open up the side slotted vent sheetmetal. Here again the client did not want any "hacking". So we simply modified the center Kuehl and engineered is a simple drop and connect.

Bottom line through my redundancy is "more air flow" rules. As one threader wrote, "in my car I simply take the targa roof off". He has the right idea, more volume.
So rather than re-routing the air branches you want to relieve them of restriction to point where you want directional control (your louvers).

You'd be amazed at the volume of air the stock box puts out through its little 2.87" nominal ID outlet . When we were exploring a "total ac package" for early narrow bodys lacking ac we field trialed a dozen or so vent arrangements. What we found worked best for early cars lacking dash vents was simply the original Behr knee pad vent system. We tried to route vents up the side window supports to the roof , cosmetically it looked terrible and we killed the drivers field of vision on the left. Then we designed a center console with a template allowing various vent arrangements. Off the floor the problem is you are too low coming out with the air. And there are limitations of the max. footprint of box you can safely put in front of the stick and near the gas peddle. The overall best arrangement for volume (with a/c) is in your chest or face. And that is what the industry designs.

So the bottom line here (though we never walk away from another good solution) is the OE layout with mods to the bow tie outlet is the best overall improvement you can sensibly make. Based on the direct feed back we get on the Kuehl vent I would have to agree as well.

[Mysterytrain]

Charlie..as always thanks for your input on the subject. I've been asking this question for awhile and haven't got a good response..so its your turn. Can anything be done [or does anything need to be done] to the return air duct work. I look at that design and it must have been a 'Beck night' when they designed it. The passeneger side arrangement is poor [ especially with carpet in place] but the driver's side is just plain silly. That 3" duct from the smugglers box snakes its way to the pedal area and then dies. Toss some factory carpeting on the pedal board and then a floor matt and the return sucks..well doesn't suck and that is my point. Jim Sims had mentioned a aux blower on the passenger side I believe but there wasn't much info on what or where? Any thoughts on this. I've always thought that they should have used the tunnel and pulled some air from under the seats into that 3" drivers side duct. thanks in advance.

[cmonref]

Earlier 911's had a return register at the rear of the tunnel where the shift rod connection is to the transmission. It is between the feet of the rear passengers. The access cover was a perforated plate that let air into the tunnel to be drawn forward to that 3" driver's side duct you mention. By the late 70's, they covered that access hole with a solid cover and the carpet set covered everything. that arrangement was on the original 911's and provided the return air to the Webasto heater in the smuggler's hole.

Just how much air you can expect to pass thru the length of the tunnel is pure conjecture.

[Mysterytrain]

My thoughts were openings under the seats on the sides of the tunnel and then having that 3" hose that dies in the pedal board area, draw from the tunnel.

[kuehl]

I have never registered a problem with the intake side, considering you have a substantial amount of square inches combined for both sides of the intake, however:

On the RH side what you can do is "shim" the wood foot board outward and inch or two which will allow more air to be drawn from the top side of the board, and insure the carpetset does not overlap the RH side over the tunnel.
A tip on the carpet set going over the tunnel, you know what a pain it is when you need work on the console wire harness and aluminum sensor tube from the thermostat under the carpet. You can slice the carpet down the centerline of the tunnel starting at front by bulkhead and work your way back to under the console. Sew or bond velcro (easier when you are doing and R&R on the carpetset) on the slit seam. Next time (and we hope you dont' have to) you need to work on the underlying components under the carpet you simply break free the velcro and put it back when you are done.

On the LH side, the nominal 3" pipe inlet mounted in the "smugglers box" for the old gas heater is one problem area for the oe "butt joint" seal. If the bottom half of the box is not mounted flush on the steel plenum intake you will draw in hot outside air which will raise your evaporator vent air temps. As you recall the system is basically a re-circ. Here we designed a rather simple but funtional sealing arrangement which we market as either a overahual kit or include with our Kuehl 911/930 Evaporators. Moving toward the inlet area to the steel pipe you are under the driver's side wooden floor board.
Here air is drawn in from the slots for the peddles and in conjunction with the tunnel.

Once again, we have not determined improvement gains could or could not be found exploring the intake side.
But, I imagine you could do a simple check to test a theory on intake loss by comparing the amperage draw on fan motor before and after.

charlie

Originally posted by Mysterytrain
Charlie..as always thanks for your input on the subject. I've been asking this question for awhile and haven't got a good response..so its your turn. Can anything be done [or does anything need to be done] to the return air duct work. I look at that design and it must have been a 'Beck night' when they designed it. The passeneger side arrangement is poor [ especially with carpet in place] but the driver's side is just plain silly. That 3" duct from the smugglers box snakes its way to the pedal area and then dies. Toss some factory carpeting on the pedal board and then a floor matt and the return sucks..well doesn't suck and that is my point. Jim Sims had mentioned a aux blower on the passenger side I believe but there wasn't much info on what or where? Any thoughts on this. I've always thought that they should have used the tunnel and pulled some air from under the seats into that 3" drivers side duct. thanks in advance.

[brcorp]

One positive on the LH intake, the sweet aroma of my feet is added to the air stream exiting the vents.....

[kuehl]

Oh we can solve that too. Try our Kuehl soles, 50% pure ground Chernobyl carbon with 45% used carbon fiber tail section, 5% blood sweat and tears.

[RandalJ]

First, I want to thank the earlier posters here for their efforts, sweat, tears, etc. I have followed this thread on and off for a few months.

I have an 86 Carrera, basically stock, and my experience so far over three Phoenix summers has been that when the stock system is operating as designed, you should be good up to about 100-105F. Above that, it's marginal. I'm still on R-22 by the way. And my car is a dark blue targa. The sheet metal gets pretty hot.

I would like to modify my system to blow cold at temps well above 120F, which would be about the max we ever see here - and bear in mind, sitting in traffic on a 115 day on dark pavement can mean 130+ where the car sits.

It appears from all that I've read here and elsewhere that the basic system is good, but lacking in condenser heat transfer capacity. I have thought about the forced air, under the fender, and the static under-belly condensers.

Ideally, I'd like to dispense with the rear condenser altogether for better engine cooling and cooler intake air.

Today, I looked at my car, and it appears there is a reservoir of some sort blocking the way in front of the driver's side front wheel, as already discussed. It also sounds as though others here have had issues with venting space, even if they can get a condenser and fan to fit. As for the under-belly condenser, that's fine if you are moving, but maybe not ideal if stuck in traffic (not to mention the heat coming up through the floor). And, truth be told, it's too damn hot here to undertake a major modification project right now. While I have not given up on these ideas, something occurred to me when i was checking my oil level.

I have an Autothority MAF, installed by the previous owner, that provides more space under the rear condenser (as opposed to the stock vane-type air flow meter). I'm thinking, hum..., maybe I can attach two powerful, very flat suction fans there. I'd do three, but the plastic air ducting on the left side of the engine would interfere with a third, and maybe the current draw would be too great.

My thought was that this would be relatively inexpensive, and it would bring down the condenser temperature significantly, which would not only help the A/C, it would also bring cooler air to the engine.

My idea was to connect these to the compressor wire, so they would activate only when the compressor is activated. Problem is that I don't know how much of a load that wire can take. The fans I'm looking at are from www.tripacfans.com (model # 14-E5167S1), and each draws 5-6 amps. I don't know yet what they cost, by my guess is under $100 each.

So, my questions are:

Can the compressor wire handle the compressor clutch PLUS two fans rated at 6 amps each? I'm guessing that the compressor clutch draws a maximum of 13V/2ohms = 6.5A. Fuse is 20A, so I'd be at about 18A (too close for comfort, I think). Are there any other loads on this circuit to worry about?

If the load would be too high, any suggestions for wiring?

Is this even worth doing? I know that the engine fan draws a lot of air already, expecially at higher RPMs. Would these fans make much difference?

And is this a flawed concept from the start? The compressor is going to create a fixed amout of pressure and heat energy, right? And the point is to extract that heat into the atmosphere. It seems that maybe the fans would just be moving the given amount of heat faster off of the condenser, but the engine wouln't process it any faster to the outside, would it?

Thanks again.

[scottb]

You have to ask yourself this question: How much more airflow do you think you're going to get over what's being pulled in by the engine fan?

Also, will the fans impede airflow to the engine?

I had no issues with venting space when I installed my front left fender condenser. It took some fabricating and replumbing, but it was a fairly straightforward job.

I can understand your reluctance to do anything in this heat, but come winter you might consider the front left fender solution. Until then, you can try the fans on the rear condenser, but I suspect you'll get marginal improvement, at best.

Let us know what you conclude.

[kuehl]

Scott B kinda has the story here on fans on the deck lid:
added fans are fighting the engine cooling fan above idle,
the fans impede air flow in the same situation (above 2k rpm),
the size of the fan you need to cover the condenser limits you to small cfm fans.

With respect to current draw, we have operated off the compressor clutch feed, you can easily pull another 8 amps off it with a simple splitter wire (Y )and you could fuse it too, you other option is mount a standard ac relay on the power panel on the LH side rear, tap off one of the fuses there and use the "Y" splitter as your trigger.

We have tried fans on the stock deck lid condenser, a very marginal improvement at idle, above idle the engine fan draws more CFM than small fans.

[scottb]

When it comes to Porsche a/c, Charlie Griffiths (aka Kuehl) is "da man." You can take what he says to the bank.

Your best bet is to look for improvements elsewhere.

Have you put in a kit to replace the bowtie under the dash? That helps a great deal to bring air out from under the dash into the cabin. Griffiths.com sells one and three vent versions. I have the older (single) vent version, and it represents a big improvement over the bowtie. This is an easy, can-be-done-in-the-heat, improvement that is worth considering.

Scott

PS: No affiliation with Griffiths, other than as a customer.

[RandalJ]

Well. That was fast!

Yeah, I wasn't sure if I'd be fighting the engine fan at some point or not. Do we know what the engine fan is gulping down at high RPMs? I'm not sure what these fans pull because they spec them at different CFM at various pressure differentials, it appears. Like 124 CFM at 15in H2O, and 411CFM at 0in H2O. Were the fans you guys tried similar?

Anyway, yes, I think the under the fender mounted with fan is the way to go. I'll research some more. I'll search back through the thread for your condenser and fan suppliers/part numbers. May also see what 20th St Auto has for salvage 993/964 front mount units, and find a way to make one fit, though it did not sound too promising fitwise without major cuts.

Scott, since mine is an 86, it has the bigger A/C vents, so force and direction is not much of a problem. Kinda loud though...

Thanks again

Randy

[scottb]

Randy: The air under the dash coming from the bowtie is wasted under there. It's better used in the cabin...IMHO.

[RandalJ]

Scott, all the air seems to be coming from vents built into the dash. At least I'm not aware of any flow from under the dash, except when I have the heat on. I have seen the Keuhl fixture that goes onto the center console of older 911s, which re-directs the flow, but I have no outlet there. I'll have another look underneath, though. But the main issue at hand is getting colder air. I seem to be getting plenty of wind.

[kuehl]

Randal,
Scott B is referring to the "bowtie vent" ; this is mounted in front of a 1" nominal hole outlet located in the "bulkhead" or firewall in front of the center console. All "factory air" cars have them from 1978-1989. The bow tie vent deflects the air from this hole left and right on your feet. The Kuehl Vent replaces the bowtie vent so you can direct the air upward and to the sides.

With regard to 86+ cars, yes you have more air flow from the side vents. However there are some issues with the center vent located in the console, sometimes the housing gets warped and you will lose ac air in its joint. Another area of lost ac air is sometimes the side vents on the 86+ cars. If you remove the heater booster fan cover (rug covered panel) on either side, you'll see a funky arrangement or manifold that takes the ac air and directs it into the side vents. What happens here is the hose falls off the manifold (we did not design it), you can fit that with adhesive tape (duct, electrical or your favorite flavor).

Getting back to the question about "how much cfm the engine fans pulls" . You could measure it with anemometer however you'd only be measuring the fan's work in its shroud. What you really want is the air flow across the deck lid inlet. But here you have problems related to loss from air coming in around the engine's rubber skirt and as well the gap between the deck lid and the body. Your deck lid condenser is approximately 8 inches in width. If you mount an 8 inch fan the housing diameter of the fan will be too big. So you have to step down to a 7 nominal inch fan. However you are not pulling a 7" diameter column of air because the pancake fan motors (under the center hub that forms the fan) are around 4 inches in diameter. And since you are flush mounting the fan you are effectively only moving the difference between the 4 inch hub and outer housing diameter. So if for example you purchase a 7 inch fan that boasts 500 cfm (for example only) you might only be pulling 200 cfm. You might consider you could get more cfm by mounting 3 of these 7 inch nominal fans across the deck lid condenser provided they did not hit something. In the end you have xxx square inches of fan pulling xxx cfm (maybe), when the engine fan is under xxx RPM's. However when the engine gets up to speed its fan will "over run" the fans and soon afterward the fans are in the way of providing cooling air to keep the motor from toasting. This is why we designed a condenser and fan assembly to mount in a different location, such as the rear fender, or in mama P's choice the front fender.

If mounting a fan or fans on the deck lid condenser of non turbo cars was the solution, by now you would see the set up bcing sold by the major catalogs or ..... cough ebayers.

[philipguziec]

I beg to differ on the fan CFM logic. If you build a sheet metal shroud (box) that seals to the sides of the condenser and covers the entire condenser and provide a small gap between the fan(s) and the condenser, you will get flow through the entire condenser. Also, depending on package space, there are electric fans available that flow huge amounts of air, and it is possible to leave the edges of the fan hanging over the shroud sides, as long as you block off those areas. You want to make sure the only air inlet is thorugh the condenser, there is a small gap between the condenser and the fan, and the only air outlet is through the fan outlet, and that any interfaces are sealed with foam of some sort. There are fans used to cool Ford 3.8L tauruses and Lincoln Mark VIIIs that pull ridiculous amounts of air--well into the multiple thousand CFMs. There are also some good products made by spal and the spal usa website gives dimensions and flow specs. The extra flow through the condensers can be forced out around the edges of the decklid, so it is possible to flow more air through the condensers than flow through the engine, especially at idle.

Phil Guziec
'89 930 Slate Grey/Black

[kuehl]

Phil,
Yes, in logic that might work. However there are limitations with respect to both the fan's height or thickness; many of the 7-9 inch pancake motor fans are 2" nominal thickness, if you want more cfm from the same diameter fan you need to increase fan speed or change the rake or angle of the fan, that requires a greater thickness; typically 3.5" nominal. Then if you want to pull the fan away from the deck lid condenser's surface you have increased the depth of the total package. Once again, if it has been done and tested with before and after results with the same constants (ambient temp), we would all enjoy seeing and reading about it.

[philipguziec]

I'm working on it. I'll post results when I have them.

Packaging is tight on the 930, but I'm managing to cram quite a bit of fan in. I would bet the naturally aspirated guys have a lot more room to play with. It would be a much cheaper and more elegant solution than adding condenser capacity.