Reid, PM and e-mail sent.SmileWavy
Thank you!

KelogGes. Very interesting concept. It was literally 130 degrees in the shade here in Baghdad today. Makes me think my anemic vent temps won't be so bad when I get home.

Regardless fixing my AC is on my to-do list and this could be the final piece i'm missing. Already have the rennaire hoses, evap, compressor, procooler but after about 30 minutes my AC stops blowing cold.

I noticed that it doesn't seem to be designed to fit the 87-89 Carrera or am I missing something?

Modifying The rock-guard
 

THE ROCK GUARD NEEDS MODIFICATION
http://forums.pelicanparts.com/uploa...1312375665.jpg

I have not talked about this before so I thought it was time I bring up this subject and now you have at least a pretty good idea about what will be needed to modify your rock guard and so you can still use it.

This is just a quick primer to let you know one way you still can use your old Rock Guard with a little modification, I will come back to this and show you in the future better how to modify your rock guard yourself or have someone in a shop you can find for not much cash to help you. For the welding and cutting off of the bracket ends to the rock guard, I doubt you can use MAP Gas but I am not sure, however I know Oxy/Acetylene torch works fine using an old coat hanger metal rod for the filler material for the welding or even brass rod, because I have an Oxy/Acetylene torch I have used to modify many damaged steel rock guards after they have been damaged by parking lots and wiping out several condensers of mine not being careful enough when parking UPPSSSS he he he

However I am sure some of you may also want a custom one made for you and if I get enough requests I probably will make new ones avalible I will make for you custom; mybe in stainless; or steel, anodized, plated, or powder coated etc if you want a closer body color match to go extreme coolness :)


If you use one of my Front Condeners THE ROCK GUARD NEEDS MODIFICATION because as you can see in the pictures I posted my condenser is a little larger; and planned this way very carefully increasing surfice area more then OEM demensions, and pushing these demensions to the limit of the limited avalible space more then Porsche did with their BEHR condenser

http://forums.pelicanparts.com/uploa...1312376330.jpg


if you look closely you can see that my front condenser is just a little too big to fit the OEM Rock guard in lengh and width; note also how much smaller the width is too.

The ROCK GUARD IS Steel this makes it easy for most people to modify it or get help modifying it fairly easy.

it would be best to unbraise or grind off the welds that holds the steel metal brackets from the rock guard and set them aside

next you will see a slightly bent end on one side of the metal to the guard, this can be Pounded flat (put it on a concrete sidewalk and get a ballpin hammer and flatten just the bend out so its flate on the one side of the guard

now try to put the end with the hose fittings on the end that is open, and the other end of the condenser inside where the metal is boxed in.

you should now notice that you can cut down the width of the rock guard to fit the new condenser buy just leaving enough width inside that works out the best between the square holes and still leaves an edge on the open end that is just a little more then the condenser that will be inside srewed into the lower pan body of the underside front of the car between the wheels where through moving it around gives you the best fit in relationship to your hoses connecting to the condener fittings.

again when i get time I will show you what I am talking about better what I mean using one of the work benches at the shop and a car on the lift rack nearby

It appears that your condensor extends BEYOND the lid airflow opening quite substantially. Wouldn't, might, the "excess" CSA with no source of airflow be "gathering" radiant heat from the engine compartment rather than dispersing it into the air stream...

Well, it is still quite new, but so far no problems. I suspect at idle you may see some of that, but even then, that fan moves a lot of air and I suspect the temperature in the engine compartment (and the condenser) is pretty close to outside ambient temperature.

There was a comment about air bypassing the condenser in various directions and again, so far no issue. There is not as much space around as you might think from the picture and the air has to follow a fairly tortuous path to get around the condenser, so I think the vast majority of the air does in fact flow through the condenser and not around it.

D.

No disrespect intended, but another way I might look at this is to say that your condenser needs modification.
If you are touting high-efficiency, custom made condensers, aim to make it fit. The heat transfer area you are losing by making it fit the stock location is negligible anyway with the anemic Bosch blower fan that sits over the top if it.

Yes, and even WORSE at the rear with NO fan and the engine idling.

Just to add...I had originally told Reid I have a front condenser on my factory AC equipped '71, but after a further look it appears I don't have one.. Any other early car users have only a rear condenser??

"..suspect...temperature...engine compartment (and the condensor) is pretty close to outside ambient temperature..."

No on your life...!!

"..suspect..." " pretty close"

It should be really easy to come by actual measurements rather that speculate..."suspect"

But don't forget you need to take 2 measurements, air temperature and radiant temperature.

NEVER have I encountered a time, after the engine has been running for some period, including at roadspeed conditions, that I did not "feel" a blast of hot air, "HOTNESS" (***) upon opening the engine lid.

*** possibly radiant HOTNESS, but that has just as much impact, or even maybe moreso, on the efficiency of the engine lid mounted condensor as does the lack of sufficient cooling airflow.

"..that fan moves a lot of air..."

Have you taken note of the fact that absolutely no effort has been made to prevent the fan's "draw", suction, from bypassing the condensor, at least partially..??

No engine lid seals, sealing.

Clearly for his application he is happy, and the airflow bypass of the condenser is not making an appreciable difference in his operating temps. Could it be more efficient? Yes, probably, but he has functioning air and is happy with minimal fuss from the Retroair kit.

If the cabin is adequately cooled to his liking, with marginal or no effect on engine oil operating temp, I call that a win.

As has been noted, so far I am happy with the install and also the gap looks far bigger than it is as there is a depression to fit the grille which makes the space between the condenser and the opening quite small (like 1 cm or less). It does block off part of the condenser though, which makes the one being discussed here interesting.

I guess the question would be, how much air flow does the condenser need to work at an optimal level? I do know that airspeed that is too fast can impair heat transfer, so what does it really need?

I have a seal on the back of my engine compartment, plus the fits are reasonably tight around the lid, so my bet is that the vast majority of air comes through the grille anyway and most of that goes through the condenser.

I have never experienced the heat flash you mentioned, in my case at idle, it is cool enough and close enough to ambient that I have not felt any major heat off of the engine unless I was close enough to hug the metal parts of course..

D,

"..how much airflow does the condensor need to work at an optimal level.."

Difficult question that..!

Obviously the need for increased airflow rises as OAT and radiant heating effects rise. A secondary factor is the pressure/temperature of the refrigerant inside the condensors, the high that pressure(temperature) gets the more effecient will be the heat exchange functionality of the condensors.

The easy answer would be, enough to condense the refrigerant gas into liquid form/state and it reaches the recvr/dryer. In the Porsche the airflow control is pretty much totally open loop, a result of engine RPM.

"..in my case at idle.."

Yes, but I wasn't speaking of idle. My original point was the HEAT soaking of the condensor post engine shutdown.

"..how much airflow.."

You can build a control to modulate the fan speed as a function of the temperature at the condensor outlet. Tape a thermistor (A) at the condensor outlet, and have another thermistor (B) to measure OAT. Now control the condensor airflow level, fan speed, to keep the "A" temperature to within a defined/selected temperature difference above ambient (B).

wwest...What is the defined perfect "A" temp...I guess I am missing the point you are trying to make...why not come out and tell us what you are trying to accomplish on this thread because I, for one, don't get it. All of us with A/C cars want better and the exploration of new tech - low tech - any tech is better than what we got now..Love to hear your theory on what to do to make it better..

BGCarrera32; No disrespect back to you too!

First you have made comments about a picture you know nothing about and furthermore you have completely taken your comments out of context for what this picture represents or why it was posted!!!

Did you not read what I wrote and said about these 2 pictures before making your negative comment???

Picture Subject caption “THE ROCK GUARD NEEDS MODIFICATION”

*The description words posted with it to explain*
“I just uploaded these pictures and do not have time at the moment to write the discription and what will be needed”

“I will re-edit this to explain so you understand better about this subject”

Lets clue you in;

These 2 pictures have to do only with the “MODIFICATION of the OEM 911 ROCK-GUARD” and adapting the OEM 911 ROCK-GUARD to fit my Patent Pending Front Condenser<<<NOTHING MORE!!!

My Patent Pending condensers need no modification they were specifically designed to be exactly what they are and appear to be for good engineering reasons; furthermore I am not going to discuss with you or anyone here the technology or specifics because they are Patent Pending,

MY test result prove they work as designed or better.

FYI: I have no intention of making perfect replacement exact fit of the original dimensions of the 911 OEM extremely old technology Porsche/Behr condensers, and have never claimed this!!! Furthermore; if you had read my whole tread here I stared and all of my posts, you would have read of my almost complete refusal to do this when someone asked me here almost a month or so ago, and why I told them I did not intend too!

Where did you get your degree in thermal dynamics and/or also mechanical engineering?

What professional experience do you have in these fields?

How Many A/C heat exchanger condensers have you invented, or made, and what was the technology you used?

What is your scientific experience, background, and knowledge with Parallel Flow heat exchangers & BAM coils?


Give me good answers to this questions and maybe I will take some time with you, as long as your intent is not only negativity.

No disrespect intended

Perhaps the next time you start making comments about something someone started to post here, “said it was not finished yet and would be finished later”; you will wait until they FINNISHED what the started writing that was not finished, so you know what it is before you make a comment about something so far off topic it has nothing to do with what the person was writing about!

P.S I never said anything in any of my posts about the anemic Bosch blower fan except I DO NOT USE IT!!!

Now I can go back and finish what I started writing this morning

Problem really is that this car was originaly designed in a cold environment .

Yes you can and its done all the time (smile)

There are a ton if really cool things you can do with current technology

hint go read about what major appliance A/C companies have done to get their SEER numbers up so high, and all the different things they now have also micro processer controlled with actuators and sensers <grin>

with ready you will gain lots of knowledge

Yes you did <grin?

ratpiper71T got a surprise for you comeing in a few days SmileWavy:

Stop what you are doing on your toy or at least slow down until you read it, as it will extremly help you to say the least. (Speaking of saying I cant say much at this time)

I am doing something with RennAire (wink) related to a 1971 911; you will read about I think maybe next week .

I have edited THE ROCK GUARD NEEDS MODIFICATION
 

In case you missed it because it was not finished this morning I had posted some pictures about THE ROCK GUARD NEEDS MODIFICATION but without saying anything except its not finished and I would edit it later when I had more time.

so go back a few messages and you will see it now what I have to say about THE ROCK GUARD NEEDS MODIFICATION

if you get one of my front condensers you are going to want to read this

Reid