Stacking front-mounted oil coolers & A/C condensers? Is it possible?

[tirwin]

A while back I was looking at my friend's AMG. One thing that caught my eye was that way that there were several radiators that were stacked in front - water cooling, A/C condenser... there was also a 3rd one but the purpose of it escapes me.

Obviously, this isn't an AMG or a Porsche but you get the idea...



Anyway, that got me thinking about a lot of our discussions regarding front oil coolers and the use of front 964 A/C condensers. I was also thinking about the need for front brake cooling.

Lots of solutions out there for these problems individually, but I don't think I've ever seen anything that really integrates the three in an elegant way. Maybe I'm wrong (and I probably am -- in fact, I hope I am because it would be really convenient if someone else has solved this problem) but I don't think I've ever seen these ideas combined before.

Assuming something doesn't already exist, why couldn't it be done? Ok, you'd have to figure out a solution to relocate the windshield wiper reservoir in some cars -- but that seems like a solvable problem. Same goes for horns.

What I'm imagining is a combination of something like the ducts on the IROC front bumper that feed into a left & right set of stacked oil & A/C condensers mounted in both of the front wheel wells. Don't get too caught up in the fact that it is an IROC bumper. Will worry about the aesthetics & bumper mods later. But this pic gets the idea across.



You'd have one set of supply lines on one side of the car and one set of return lines on the other. Some thinking would have to be done there. Maybe there is a way to do a crossover oil return line in the body cavity where the steering rack sits. That would minimize changes to the under body mounting points for the oil and A/C lines. I think everything else would be relatively unchanged as far as mount points go.

Additionally, the use of puller fans to help draw additional airflow through the ducts. Karl (Discseven), if you're reading this, your experiments with the RC turbine fans might have an interesting application here too!

Here is a pic of a 964 A/C condenser. Now imagine that there are two "stacked" condensers on each side -- one for oil and one for A/C.


Now imagine a duct connecting the front bumper intakes to the stacked coolers and then to the brakes. Airflow to the brakes could be diverted before or after the coolers -- haven't thought that far ahead.

This isn't a 911 but it conveys the idea of an A-arm mounted duct. (I know this has been done before on 911s - just didn't have a 911 picture handy.)


A third nose-mounted combo set of condensers could optionally be added in series if that much capacity was required. That might require tub modification on some cars.

Again, maybe this has been done before. If it hasn't, let's discuss the feasibility and design challenges that would need to be overcome.

First challenge to me is to figure out physically compatible condensers -- i.e., ones that have same/similar size, shape, openings, surface patterns so that one does not impede the airflow of the other.

Second question is whether there is enough space on a narrow body or would something like this only work on a wide body?

Thoughts?

[gremlin]

I've sort of wondered this myself. With the electric AC retrotfit in an early model car I thought I'd read that you needed to cut out the battery box, but I have a oil cooler on the non-drive side (right hand) of my car with a battery box, so I wondered if the AC unit could fit in the left side, or it had to be front mounted

[Bill Verburg]

Originally Posted by tirwin

A while back I was looking at my friend's AMG. One thing that caught my eye was that way that there were several radiators that were stacked in front - water cooling, A/C condenser... there was also a 3rd one but the purpose of it escapes me.

Obviously, this isn't an AMG or a Porsche but you get the idea...

.....

Anyway, that got me thinking about a lot of our discussions regarding front oil coolers and the use of front 964 A/C condensers. I was also thinking about the need for front brake cooling.

Lots of solutions out there for these problems individually, but I don't think I've ever seen anything that really integrates the three in an elegant way. Maybe I'm wrong (and I probably am -- in fact, I hope I am because it would be really convenient if someone else has solved this problem) but I don't think I've ever seen these ideas combined before.

Assuming something doesn't already exist, why couldn't it be done? Ok, you'd have to figure out a solution to relocate the windshield wiper reservoir in some cars -- but that seems like a solvable problem. Same goes for horns.

What I'm imagining is a combination of something like the ducts on the IROC front bumper that feed into a left & right set of stacked oil & A/C condensers mounted in both of the front wheel wells. Don't get too caught up in the fact that it is an IROC bumper. Will worry about the aesthetics & bumper mods later. But this pic gets the idea across.

.......
You'd have one set of supply lines on one side of the car and one set of return lines on the other. Some thinking would have to be done there. Maybe there is a way to do a crossover oil return line in the body cavity where the steering rack sits. That would minimize changes to the under body mounting points for the oil and A/C lines. I think everything else would be relatively unchanged as far as mount points go.

Additionally, the use of puller fans to help draw additional airflow through the ducts. Karl (Discseven), if you're reading this, your experiments with the RC turbine fans might have an interesting application here too!

Here is a pic of a 964 A/C condenser. Now imagine that there are two "stacked" condensers on each side -- one for oil and one for A/C.
......

Now imagine a duct connecting the front bumper intakes to the stacked coolers and then to the brakes. Airflow to the brakes could be diverted before or after the coolers -- haven't thought that far ahead.

This isn't a 911 but it conveys the idea of an A-arm mounted duct. (I know this has been done before on 911s - just didn't have a 911 picture handy.)
......

A third nose-mounted combo set of condensers could optionally be added in series if that much capacity was required. That might require tub modification on some cars.

Again, maybe this has been done before. If it hasn't, let's discuss the feasibility and design challenges that would need to be overcome.

First challenge to me is to figure out physically compatible condensers -- i.e., ones that have same/similar size, shape, openings, surface patterns so that one does not impede the airflow of the other.

Second question is whether there is enough space on a narrow body or would something like this only work on a wide body?

Thoughts?

First the 911 and 964/993 have different chassis sheet metal configurations which make it difficult to use the 94/993 longitudinal/diagonal coolers on a 911

here's a 993, 964 is the same in front
Note the tapered area in front of the front wheels


Same area in a '72 911, delete the battery boxes and that's what you get through '89 and a '74 w/o battery boxes



Here's my 993 w/ stacked 2nd cooler an Ac condenser on the drivers side, there just isn't room to do this on a 911, A very efficient duct is formed w/ intake mouth diverting a huge amount of air left and right, both sides are sealed so than air has to go through the coolers and exhausted either under the chassi just in front of the wheels or in some cases into the wheel well. There is a further very efficient transport of air out of both wheel wells, both brake and oil cooler air are removed by this mechanism. For heat transport to occur efficiently a very large sealed duct and some large as possible pressure differential needs to exist.





The front coolers nee air moving through them, the more air the more cooling the more area the more cooling which is why a relatively small nose mount can cool better than a much bigger fender mount, there is a relatively huge amount of cool undisturbed air going through the nose, very efficient, You'd need 2x larger fender mounts to cool w/ the same efficiency. Many choose to go the 2x fender route more because of optics than anything else, it does work ok though so why not.

As for stacking it does lower the efficiency as does the provision of a fan, both impede air flow, though the fan at least is helpful at really slow speeds, If you can afford the cooling loss and have the room there is really no reason not to stack, it's just that space is at a premium on a 911 front end

[tirwin]

Thanks, Bill. Good info regarding the 964/993.

Is this what you mean by the tapered area?


I have an aftermarket Terbatrol (sp?) oil cooler up front. It seems like that kind of form factor could possibly still work on narrow G-body cars, or perhaps on a wide body.

Some math would be required. As you noted, there would be less efficiency in a stacked configuration. Surface area, airflow & efficiency of heat exchange would have to be factored in.

Some possible scenarios:
1) stacked L/R front wheel well only
2) stacked L/R front wheel well + nose
3) stacked nose only

If you knew how much heat exchange capacity is needed and how much could be achieved by each of the 3 scenarios, that would answer the viability question.

Need to figure out some back of the napkin thermodynamics math.

Make sure I'm understanding this picture correctly. I've circled what I think is the intake port. Is this correct?


A sealed unit such as this is exactly what I was envisioning. Either a single channel for the heat exchanger + brake. Or an internal diverter with two separate air flow paths for brake and heat exchangers.

[Bill Verburg]

Originally Posted by tirwin

Thanks, Bill. Good info regarding the 964/993.

Is this what you mean by the tapered area?

yes

Originally Posted by tirwin

I have an aftermarket Terbatrol (sp?) oil cooler up front. It seems like that kind of form factor could possibly still work on narrow G-body cars, or perhaps on a wide body.

My final solution when I had the stock 3 liter in the C3 was a Turbatrol, It worked fine for track days w/ the 3.0, but not a 3.6 even on the street

Originally Posted by tirwin

Some math would be required. As you noted, there would be less efficiency in a stacked configuration. Surface area, airflow & efficiency of heat exchange would have to be factored in.

Some possible scenarios:
1) stacked L/R front wheel well only
2) stacked L/R front wheel well + nose
3) stacked nose only

If you knew how much heat exchange capacity is needed and how much could be achieved by each of the 3 scenarios, that would answer the viability question.

Need to figure out some back of the napkin thermodynamics math.

You are over thinking this, The system either works or doesn't and there are plenty of examples that work w/ any possible combination of engines and chassis, You do not have to reinvent the wheel

Originally Posted by tirwin

Make sure I'm understanding this picture correctly. I've circled what I think is the intake port. Is this correct?

no, the air enters the mouth which spans the full front lower bumper, there are several different versions of 993 front, the orange scoops on mine are for brake cooling, as are the scoops on the others, the stock one has lights there, I also opened the flow a bit by removing the central bar seen on the others.


The flow goes inside out(chassis side to fender side and then down, it is directed by the trunk wall on the inside and the fender on the outside, then down through the bottom of the splitter into the outer forward wheel well area. where natural flow exhausts it to the side






Forget stacking, forget how a 964/993 does it.

Known 911 solutions are single radiator cooler w/ fan in the right side front fender ala factory

twin fender mounts one in each fender

Elephant would be the best source for all the necessary parts

More efficient is either a single chin mount or a chin mount added in series to the stock fender mount, this will satisfy all but the most extreme cooling needs, The only reason not to go this route is that some don't like the optics

Here's mine, I use a single B&B 5 1/2 X 2 1/4 X 20 mounted in the Ruf bumper, the grills where the fogs were are really functional here I put them in in anticipation of having to feed at least 1 fender mount but that proved to be unnecessary the edges are sealed so all the flow goes through the cooler. This has proved adequate for up to a 3.8RS engine in this chassis for street use. It would not be adequate for track use, For track use a different bumper and larger cooler and possibly a fender mount in series would be needed. The 3.6s generates a lot of heat at track days and even the stock 964/993 large Setrab isn't adequate on hot days w/ long runs

[Tbone1209]

I have a 3.8 RS type motor in an 84 with a very similar front RUF Style front air dam. I also have a B&B cooler in that central chin location. The car was built for Southern California and includes two B&B fender mount coolers with a fan on one of those fender mounts. The car now resides in San Francisco so safe to say that it takes some time to get warmed up and never triggers the thermostat switch for the fan operation unless driven very hard on a warm day. Some folks have said that I could probably pull one of the fender mounts if I wanted to to save a bit of weight but who knows where the car will end up.

[tirwin]

Bill, maybe I am over-thinking. I am doing some ideation about a possible future project. As you noted, 964/993 chassis lends itself well. But it is also heavier too. Preference would be to use a G-body chassis as starting point for lightness.

A goal in stacking is elimination of A/C condensers in other areas (decklid, rear fenders). Eliminating that problem helps address others. So from an oil cooling standpoint, single fender + center nose should be sufficient. Center cooler being most bang for the buck. 2nd fender would likely be overkill. Now add stacked A/C condensers to the equation. Is that still enough cooling capacity for both applications factoring in slightly less efficiency of each due to stacking?

Like the RUF!

Thanks!

[tirwin]

Originally Posted by Tbone1209

I have a 3.8 RS type motor in an 84 with a very similar front RUF Style front air dam. I also have a B&B cooler in that central chin location. The car was built for Southern California and includes two B&B fender mount coolers with a fan on one of those fender mounts. The car now resides in San Francisco so safe to say that it takes some time to get warmed up and never triggers the thermostat switch for the fan operation unless driven very hard on a warm day. Some folks have said that I could probably pull one of the fender mounts if I wanted to to save a bit of weight but who knows where the car will end up.

Beautiful car! So, you have 3 oil coolers in series? Nice!

[Jonny H]

Some maths for ya (or ’math' as you'd say in the US). The 964 AC condenser (5kW heat load) on a 30 C / 86 F day would result in output air temperature of 47 C / 116 F.

So for your 'stacked' oil cooler to work, one would have to prove it at the hotter temperature. Or like Bill says, just try it!

By the way, if you're tempted to 'stack' two AC condensers, don't bother. The second is rendered next to useless by the heat output of the first.

[Tbone1209]

Originally Posted by tirwin

Beautiful car! So, you have 3 oil coolers in series? Nice!

Yup. It's probably over cooled but why mess with it. It gets hot in wine country in the summer. It's a factory wide body. Windshield washer tank got moved to the frunk and the headlight washer tank was eliminated. Mark Kinninger (@skidmark) did all the work on it. It's pretty bullet proof..

[tirwin]

Originally Posted by Jonny H

Some maths for ya (or ’math' as you'd say in the US). The 964 AC condenser (5kW heat load) on a 30 C / 86 F day would result in output air temperature of 47 C / 116 F.

So for your 'stacked' oil cooler to work, one would have to prove it at the hotter temperature. Or like Bill says, just try it!

By the way, if you're tempted to 'stack' two AC condensers, don't bother. The second is rendered next to useless by the heat output of the first.

Jonny, just to clarify... I'm not suggesting to stack 2 oil coolers in the same location. I'm suggesting stacking oil cooler + A/C condenser.

Imagine a series:

Right fender "stack" (oil cooler + a/c condenser) + chin "stack" + Left fender "stack"

The question is whether there is enough surface area for sufficient heat exchange capacity for both applications? The efficiency of each heat exchanger in a stack would be less than if it was standalone. I just don't know by how much. Your comment that a 2nd stacked A/C condenser is worth noting. But the practice is quite common in other vehicles but the limited nose horizontal surface area of the 911 makes it a challenge. How do they get away with it? 3 stacked heat exchanges in a series seems like it would be about the same (or more) surface area of a single stack in a typical front-engine vehicle.

Maybe this is where Bill's comment regarding the (comparatively) reduced airflow to the the fender exchanges is less than the nose.

[Bill Verburg]

Originally Posted by tirwin

Jonny, just to clarify... I'm not suggesting to stack 2 oil coolers in the same location. I'm suggesting stacking oil cooler + A/C condenser.

Imagine a series:

Right fender "stack" (oil cooler + a/c condenser) + chin "stack" + Left fender "stack"

The question is whether there is enough surface area for sufficient heat exchange capacity for both applications? The efficiency of each heat exchanger in a stack would be less than if it was standalone. I just don't know by how much. Your comment that a 2nd stacked A/C condenser is worth noting. But the practice is quite common in other vehicles but the limited nose horizontal surface area of the 911 makes it a challenge. How do they get away with it? 3 stacked heat exchanges in a series seems like it would be about the same (or more) surface area of a single stack in a typical front-engine vehicle.

Maybe this is where Bill's comment regarding the (comparatively) reduced airflow to the the fender exchanges is less than the nose.

whether or no stacking an oil cooler and condenser works will depend on air flow, 964/993 works because there is a large efficient fan on each side. When moving these rarely if ever come on because of the large flow through the mouth, through the cooler and then out the exit.

What's wrong w/ the usual 911 condenser mounting point under the front pan?

as I said a single chin mount is fine for the biggest motor you are likely to use in street use(and the heaviest traffic I've ever been in but I don't live in LA or NYC), for some extra insurance by all means add a chin mount in series to the existing right side oil cooler, 99% of the time it won't be needed. Evn On mine the temps mostly oscillate around 180-190F rarely above and never above 210

Then if you still want to fool around w/ the AC condenser use the left side fender,

Just FYI here are some pics of an early RSR clone which went the route of dual longitudinal mount coolers