Griffith's fender condenser dimensions

[rusnak]

whoa, long thread getting dizzy....

has anyone enlarged their front stock cutout for the stock condenser and put in a bigger one in the stock location? It seems two fans there would work.

I can't put a condensor in the front left fenderwell without losing the washer bottle, so that's a non-starter.

The left rear fenderwell is too hot (take an infrared thermometer and measure the temps there). The cat gets to around 500F on a cool day, more like 600F + on a hot day with AC on.

I need to get some help for the rear decklid condensor, which stops working at around 102F ambient temp. At those temps the engine block is around 220F and the condensor is useless. As it is on a mild day the condensor only cools the refrigerant by around 5F. Most of the cooling is done by the coolant hoses.

[scottb]

Originally posted by rusnak

I can't put a condensor in the front left fenderwell without losing the washer bottle, so that's a non-starter.

I respecfully disagree. The washer bottle and vapor recovery tank can be relocated, and a condenser will fit nicely in that spot. I put a generic washer bottle in the trunk, and this is what now resides in the front fenderwell:



The cooling fan for this condenser is on the other side, and the condenser itself is protected by a mesh guard (not shown in this picture). The fins were a bit mangled during the installation process, but I've since straightened them.

[Jim Sims]

"I need to get some help for the rear decklid condenser, which stops working at around 102F ambient temp. At those temps the engine block is around 220F and the condenser is useless. As it is on a mild day the condenser only cools the refrigerant by around 5F. Most of the cooling is done by the coolant hoses."

There is something seriously wrong with your A/C or your temperature measurement techniques. What counts is the temperature of the air flow being inducted into the condenser through the decklid grill not the temperature of the engine. How are you measuring the refrigerant temperature drop across the decklid condenser? The decklid has to be shut and the engine idling (preferably at 2000 RPM) to correctly take this refrigerant temperature drop measurement. I doubt very much cooling happens in the refrigerant hoses. Don't confuse surface temperature of a hot component with local air temperature and the air's ability to remove heat by convective heat transfer.

Performance Aire (Scott's Independent Porsche?) in SoCal sells an improved triple pass decklid condenser for 911's.

Jim

[rusnak]

I would be interested in buying the triple pass decklid condenser.

Basically I pulled over after driving with AC on for about a half hour, then popped the decklid and then took the temp of the copper tube going in, then similar temp "technique" for the copper tube going out. Pretty much a 5F difference. And for the past 3 years the AC is useless at over 102F, as the condenser is so hot that "cool" air can't really overcome the amount of heat being pumped into the condenser from the motor.

You outta try measuring the heat coming off the motor at close proximity on a 102F day. It's pretty darn hot, and when the ambient air is a 102F everything including the driver is just dang hot.

[Jim Sims]

Last summer when I passed through Needles, CA during the afternoon (temp over 100F) in my '76 911 the A/C was working fine (turned down a notch from max cool) and all I have is a single 1976 vintage deck-lid Kcool condenser and a homemade sub-cooler up front above the steering gear splash pan. As long as the condenser and refrigerant are hotter than the ambient air the condenser will still work (but less efficiently of course as the delta T between the refrigerant and air decreases) if air is flowing through it. As soon as you lift the lid you invert the liquid outlet and stop the air flow due to the engine fan pulling in air so I'm unsure how valid the temperature measurements you made are. However, if your not getting cool air you have a problem somewhere. Have the system's refrigerant charge and operation checked and troubleshot with a refrigeration harness and thermometers.

The triple pass 911 condenser is over $400 if I recall correctly and you'll need an external oil cooler for the engine if one isn't already installed.

Cheers, Jim

[kuehl]

The left rear fenderwell is too hot (take an infrared thermometer and measure the temps there). The cat gets to around 500F on a cool day, more like 600F + on a hot day with AC on.


I can understand your concern about temps in the rear fender with cat's. However rear fender condensers, when properly designed, move air toward the cat and the air is cooler. In our first design we were pulling air from the cat side moving it toward the condenser and it worked fine.... meaning the cat did not overheat the condenser. However the plastic fan did not get along well with the cat when mounted on the cat side. We changed the design and improved air baffling and the system works extremely well.... so well other's have attempted to copy the design.





One of the benefits of placing a condenser outside of the engine compartment, and running it in series with the deck lid condenser, is that you reduce the "load" (lower psi; and sub cooling the liquid side) placed on the deck lid condenser : meaning less heat moving into the engine.


Basically I pulled over after driving with AC on for about a half hour, then popped the decklid and then took the temp of the copper tube going in, then similar temp "technique" for the copper tube going out. Pretty much a 5F difference.

As Jim noted we don't know how you measured the delta of the refrigerant temperature in/out. The delta could be determined using thermocouples clamped on the inlet and outlet pipe extensions (or hose fittings) to the coil, or possibly by using an infrared thermometer aimed at the alike sections however not as accurate at times.

Deck lid should be down so that the engine fan is pulling outside air down and across the condenser. Cooling increases with rpm (the "P" standard point of reference has been 2000 rpms; engine cooling fan pulls in the air).

You may want to check the rubber seals between the engine sheet metal and the body to insure you are not pulling in air from places that would bypass the deck lid condenser. We had a client stop by last year with a problem like you described and apparently he did not know he was suppose to re-attached the sheet metal skirt after he did and engine R&R. If the the deck lid condenser is not stock (undersized or a shape that does not fill the rectangular cut out in the deck lid) there could be a problem with air bypassing the coil.

[rusnak]

Hello Kuel:

Yes, that new design does address my concern. It's an improvement that I was not aware of. Any plans to increase the capacity of the "chin" condensor in the front of the car?

[Mysterytrain]

Ok, lets chew on this bone. Can an effective AC system be installed in a 911 that does not include a condenser installed on the engine lid? I would be interested in a C2 condenser in the rear fender and an improved front lip condenser. I've often thought that street car could employ a center mounted condenser much the same way as track car uses a center mounted oil cooler.

[rusnak]

I agree, Ron. But if it's a street car then it has a cat, and it should have a state of the art heat shield between the cat and fender condenser.

[Jim Sims]

"Can an effective AC system be installed in a 911 that does not include a condenser installed on the engine lid?"

Probably but only at the cost of a new front valence/bumper. This would get into aero effects and the appearance of the car. It would also require adequately sized, switched (perhaps based on condenser pressure) cooling fans and arrangements for air flow. A static unit (like the under-body units) by itself likely will not suffice for slow driving or idling in traffic.

[930slant]

Check out the August edition of Excellence, page 24... the ad by RennAire.com, shows a new serpentine "twice as thick" front condensor that is purporting to do a better job than the stock unit. It is designed for 911's 1978-1989. The owner, Ron, said that the unit will be particularly effective when outside temps are in the 90's.

I currently have barrier hoses, deck lid fan, pro cooler, Griffiths evaporator, and the bow tie comnversion kit on my 88' 930.

Yesterday in DC I got vent temps of 39 with an outside reading of 84.

[rusnak]

Got a pic and info on the decklid fan setup?

[Jim Sims]

"state of the art heat shield"

The Griffith's fender kit already contains one metal radiation heat shield; the fender location is a hostile location for any fancy selective surface coatings. One can easily add some additional heat shields (I'm considering putting one between the muffler outlet pipe and the rearmost condenser lower manifold) but this is a balance between air flow and radiation interception. What do you consider state of the art? The Stefan-Boltzmann law is now 122 years old; radiation heat transport is not a new field. Do you seek an expensive, elaborate piece of titanium with many facets and features to get the view factors and air flow just right?

[Jim Sims]

The improved Renn Aire front condenser is a good development but I also suspect this area needs a fan improvement over the weak stock unit for operation in slow traffic.

[rusnak]

I apparently want a laweresque fancy and offensive to some heat shield I guess.....

I never said I was going to hire a team of scientists, just that it needs more shielding, which you yourself allude to, Jim.

[930slant]

rusnak,

I got the deck lid from performance aire, 714-634-9184. Sorry, no pictures but it easily attached to the underside of the deck lid condensor on the passenger side. (Since my car is a turbo, I only have 1/2 sized condensor in the deck lid.) It called for a fused wire for powering it as I recall. The fuse kept blowing so I had a shop install a relay for it. no problems since then. As an aside, i tried to find out the rating of the motor that runs the fan, but performance aire had no data on it.)

[rusnak]

930 slant, thanks for the info. I don't think that will fit unless I put a tail on my 3.2, but it may also increase airflow since the inlet is moved to a high pressure area. I'll call perf aire.

Around here pretty much every day is over 100 in the summer, some days hover at 105-107 all day long.

[Jim Sims]

"laweresque fancy" view factors? The heat transfer people will get a kick out of that one.

"just that it needs more shielding, which you yourself allude to"
IMO, relative to the cat there is little to be gained by more heat shielding in that area.

Almost everything can be made a little better but there some point where it just isn't cost effective or it unbalances the total system. But then again we Porsche people like to do things to excess.

Cheers, Jim

[kuehl]

Originally posted by rusnak
Hello Kuel:

Yes, that new design does address my concern. It's an improvement that I was not aware of. Any plans to increase the capacity of the "chin" condensor in the front of the car?

We have a serpentine front condenser.

[kuehl]

Originally posted by Jim Sims
"Can an effective AC system be installed in a 911 that does not include a condenser installed on the engine lid?"

Probably but only at the cost of a new front valence/bumper. This would get into aero effects and the appearance of the car. It would also require adequately sized, switched (perhaps based on condenser pressure) cooling fans and arrangements for air flow. A static unit (like the under-body units) by itself likely will not suffice for slow driving or idling in traffic.

Agreed. It would be something like a 964/993 and requiring "hacking". The Kuehl systems are designed to bolt-on and go.