I'd like to start an open discussion on oil front mounted oil coolers and ducting.

I had a nice chit-chat with Brad today on the subject and I am convinced that I need to get one installed.

Planning to go BIG to be prepared for the SIX later in the year.

Any opinion on ducting from the fog/horn grilles and the round rubber front trunk body grommets?

Exit air into fender wells is what I think. You?
Andy and I tossed around the idea of getting the air out through the grill below the windshield. Might be tricky.

I'd like to use a piece of sheet metal to create an air space for the install and still have *some* trunk space available.

Pics would be nice.

KT

I did a search on this...I just want a fresh thread

whatever gives you the least restriction. going through the fender wells means two 90 deg. angles on each side. air doesn't like that kind of thing.
it'll just pile up behind the oil-cooler, rendering it useless ....

only 2 (well, actually 3) options that will give you good results, IMHO ...

1. the factory GT shroud method. small angle, low resistance. good cooling. only drawback is adding more air under the car, which will give you more lift at very high speeds.

2. hang it under the bumper. the very early GT's had that, no cutting of the tub, just run a wide but slim cooler under the bumper, hot air will be directed under the car. very good air-flow. downside, you run the risk of ripping it off getting in/out the starbucks parking lot.

3. out the top. slightly more angle than 1. still very good airflow (add a lip in front of the hood cutout!). downside, highly visible and brad doesn't like the warm air coming over your windshield. (pussy!)


Andy

ohhh... I love this thread.
I've been there and tried a few things...

On my first race car, I ran 3 different set ups with the same cooler. I agree with Andy completely that its all about the exit. I finally went through the hood on my 3rd attempt and found another 20degrees each of the times I changed my exit.

since I don't have a camera or enough intelligence to post a picture, Andy can you post my front hood picture for me?

regarding fog light grills.... It is possible, but I don't know if you want to go there..... I have this set up right now on my race car, but since the car has still not had its maiden voyage I can't guarantee you that it works.

I first saw this set up from a friend of mine named tom hayes. He ran a pair of mocal coolers behind the fog lights with round PVC tubing behind the bumpers to force the air into the coolers.... Didn't work too well and he ended up ditching it for a race cooler in the spoiler (PCA-GT 5 car).

I realized that his exit was (IMHO) what was not working for him. In my new car I've run a pair of fluidyne double pass coolers in series. I talked with the engineers at fluidyne at length while planning my new set up. This car has no headlights so the air enters through the fog light grills and into an aluminum custom fit Square tunnel (approximately 6inches wide and 12inches tall.. Air goes through the coolers and still remains airtight inside of the tunnel on exit and then finally into the fender wells... The coolers are sealed inside of this tunnel, which I think is absolutely key. Its a straight shot with no bends... TONS of fabrication time into the tunnel... Double the fittings since I'm running 2 coolers in series, and pricey...

I wanted my fuel cell down lower than the stock location and was not allowed to go the hood route with the new car due to "Vintage Rules" in the new class I'm going into...

I strongly recommend you stick with what is tried and true. A good cooler set up will run a grand with lines and all.

brant

Geeze I dont have a windshield wonder how that would make him feel

Here's what we're working with.
Use you favorite photo software to edit up your proposals.

Keep the comments about the dirty trunk to a minimum, thanks

KT

I used a crayon to draw this

the ducting would be the same hieght as the spare tire arch with a rubber gasket on top so when the sheet metal is set over the top and into the space it is air tight.

Think rat running through maze. <_<

The flow of the air is large and unrestricted.
It " Y's " left or right straight out the wells.

storage on top.

KT

two coolers in series ? conventional wisdom says run them in parallel for a lot of good reasons. but if it works for you go for it...

back to Trekkor...

GT shroud, duct it out the bottom, be done with it. clean, safe, simple, works. the factory cars didn't lift at Le Mans, they didn't lift at the Nurburgring, and if you've got straights as long as Mulsanne i don't know where, now that the Riverside CanAm course is a shopping center ...

in front of the windscreen is a HIGH pressure area - might be good for a cooler INLET (have a look at have every NASCAR car uses cowl induction) but you'll never get air to exhaust there.

you might be able to duct it to the fender wells IF you add some exhaust vents to the bodywork. this isn't legal (unless stock) in even SCCA SOLO-II Prepared Class and will move you to Modified if your competitors have read the rulebook carefully.

GT shroud, duct it out the bottom, be done with it.

how about the maestro himself? that'll keep things cool ...

Andy

That's one of the funniest things I've ever seen...and it might work!

KT

White wine and pumpkin pie; is that a Texas dinner?

Trekkor, you need to stop by tomorrow or saturday. I know you like crazy ideas and I have a few.

Granted, all of my experience with heat exchangers (or an oil cooler in this case) is military aircraft related, but they're all run in series (primary and secondary HE's). Just curious what the "conventional wisdom" and "good reasons" are for running them in parallel? Resistance/back pressure?

Word. Do it once this way and move on to other projects

I considered ducting air thru the fog light grille exiting the headlight cover. There is alot of plumbing involved with this arrangement. With a wet sump TIV, not sure it would be a good situation.

A six with dry sump and good scavenge arrangement could make this work, but the coolers are in a very vulnerable location.

Also, while you could make this work within production car rules, it would not fly in most vintage classes, at least down here.

dr

So I'm going with dual coolers at the rear. I know of another 914 racecar that runs a similar arrangement with excellent results.

This is probably not good for a street car, won't cool unless the car is moving.

The coolers are actually mounted now, will post pictures later.

dr

actually, i think that was beer in a wine-glass. x-mas dinner party at my place lascht year ...

I'm sorry but I always go factory whenever I can.
You can get the GT shroud and internal air baffle from Getty Design.
The GT option has kept my previous 2.7 motor very cool and my current 3.2 motor barely gets to 190degrees on the freeway.

Check out Jon Lowes GT page
http://fly.hiwaay.net/~jonlowe/MyGT.html
This page shows the cutouts.
http://fly.hiwaay.net/~jonlowe/MyGT0005.html

The GT won Lemans and many other races with this arrangement.

I hab no thoughts....I gots a pic, tho.

You can see that I punched some holes in the bulkhead to vent the thing and was prepared to punch more if needed. They aren't. Maybe I found a low pressure area.

At any rate, the oil temps never go over 100 C....hot day, 2 driver AX. A mild temp track day....90C all day.

The feed line to the cooler is hot (no touchy hot) and the drain line is warm (grab aholt).....what more does one need?

Built a cover to go over the whole wurks...see next pic ....so's I can haul shittage in the front trunk....duh...piece of cake.

the quick brown fox........

VERY neat JP

mostly, it has to do with the nonlinear efficiency of a heat exchanger and the temperature differentials.

if a heat exchanger can reduce the temperature of 250F oil to 200F, you've rejected 50F to the airstream. that same exchanger is not going to reduce the temperature of 200F oil to 150F. the greater the temperature differential between the oil and the heat sink (the freestream air) the more efficient it is going to be.

so for most efficiency, you want the oil entering the heat exchanger to be as hot as possible to avoid getting into diminishing returns.

as you've observed, there are places and applications where serial coolers make sense.

Nice cooler set-up JP.

Rich,

my ignorance shines through...
I should have clarified that my new set up is in parallel (sp)

and not in series...
(however I am using double pass coolers so actually the coolers are in series, but they have a built in parallel component also)

Andy, do you still have those pictures of my front hood and ducting on the black car?

brant

Can someone diagram or describe a parallel arrangement?

Do you need coolers with multiple ports like the ones fluidyne makes? If not, I imagine a couple T's in the lines.

dr

JP,

I like that set-up. That kink in the tub where the steering rack is looks like a good low pressure area.

You do you leave the steering rack cover / skid plate off?

Series versus parallel?

Series is when all of the oil flows first through cooler #1 and then through cooler #2.

Parallel is when the oil flow is split with a part of it flowing through cooler #1 and the remainder flowing through cooler #2.

yes, inline Tees.

less overall pressure loss too, even without considering the scenario where one cooler gets plugged with something.

since the flow is split, you might be able to take advantage of a reducing Tee and run smaller, cheaper, lighter lines to the separate coolers -- but i'd probably keep it all the same.

if you were determined to run two coolers in a /6, a second or replacement cooler in the pressure circuit can pay off -- the pressure-side oil has been de-aerated and pressure-side coolers are much more efficient. scavenge oil is more like foam, yet another reason the fittings must be on the top...

The cover is on.

The holes are 3 inch diameter. That would seem to be an inadaquate amount of venting area, but it works.

Maybe the front valence helps build air pressure at the cooler.

JP,
How much did that cooler setup end up costing?

IIRC

The cooler .....direct from Fulidyne... 300
Troutman thermo ....165....got a deal on that. They're around 200-210.
Fittings & hoses.....about 280 (IIRC)....ya need lots of bent fittings and them suckers aren't cheep...damnit....Summit Racin'.

I've got some -12 hose & straight fittings left over....or was that plan B? .....Anyhew, the stuff is F/S cheep.

As you stated, heat exchanger efficiency/transfer is non-linear. Let's assume that the maximum heat transfer one HE can achieve will drop the oil temp 50F. So using your example of a heat exchanger lowering the temp. of the oil from 250F to 200F, a parallel HE system would still have a total outlet temp of 200F (50F differential). So if there's an efficiency drop in the secondary HE of a series system (say 50% for the sake of argument) which only allows for a 25F differential over the inlet/outlet temp (200F to 175F), you would still have a total of a 75F differential from a series system VS a 50F differential from a parallel system. So wouldn't "diminished returns" on a series setup be better than "no returns" (in the form of added heat loss) on a parallel setup? NO disrespect intended with my question, just trying to get the facts straight prior to running all of my oil lines (dual cooler).

Kevin

NOW i remember why i hate you

no matter what i do to the 911 this winter it's getting a front cooler, the big 911RS-sized FluiDyne one. naturally my '71E had no factory cooler and therefore no factory thermostat, so i'm gonna need to do -something- ... a quick search for Troutman thermostatsturned up nothing but people recommending them or bragging they were using them - no leads on suppliers. are these things even available any more ?

i'll use a factory thermostat console if i have to, the more i hear about the Mocal the less sure i am that's a viable alternative. (the factory thermostat console is expensive, but so's my engine ...)

I think that in the parallel system, the temperature drop in each exchanger would be greater than it would be in the first exchanger of the series system since in the parallel system the fluid volume is split and would spend more time in each exchanger. But then again, this is all just theory (WAG).

How about you try it both ways and prove it one way or another with a real world experiment? Then we would know.


Andrew

Good point Andrew....okay, same senerio but with equal flow/pressure through both types of systems.

Carroll Smith (who had access to a lot of real-world data) covered this very succinctly in one of his books (the first, i believe, "Prepare To Win"). i don't recall all the details of the points, but give me a couple of hours and i'll be back home with access to all my reference materials. i'll post what Smith had to say on the subject, and then we can debate -that-

Excellent! Should the data show a parallel system is more efficient at dissipating heat than the series system (which it obviously does or you wouldn't be posting) then I'll have to rethink my plumbing for my oil coolers and condenser coils. Now would be a good time find out if I'm F'n up by going with my original "series" setups!

I have all his books.

In "Tune to Win", Carroll says to plumb multiple coolers in parallel (pg 98)

Can someone diagram this parallel arrangement for me?? I am too dumb to figure it out.

dr

Troutman still advertises the thermostat in Pano or Excellence

I believe this is Troutmans site

I do have a factory thermostat though if your interested..

hot oil from engine
cool oil to engine

that sure looks like Troutman's site - germanpartsusa.com - i'da never found that one by guessing !

interesting nomenclature on the thermostats tho, i suspect the website was built by someone who doesn't know Porsche oiling systems - lists 10mm, 12mm, and 30mm. that's gotta be AN-10, AN-12, and 30mm ...

Rich,

for the sake of it, since you obviously know how to use paint brush and I don't...

draw out the "series" diagram also please.
brant

Perhaps... they have advertised the other (smaller sized) thermostats for years, perhaps for other applications..I think the print add reads 10an and 12 an

hot from engine
connector line
cool oil to engine

sorry - there is no 'brown' textcolor...

note how ALL the oil goes through BOTH coolers.

Ok...
not that it matters but I have to one final time correct myself....

I am running my coolers in series.


When I planned it out with the fluidyne engineer, they were very technical and were using not only PSI, but other info about my cooling needs....

They were very concerned about restrictions (for example you must use smooth 90's and not sharp 90's fittings)..

They wanted my total pumping lengths and factored in their cooler restrictions.

They were very concerned about the angle that I mounted the coolers and wanted them stood up straight with no lay back...

but they did not mention the series - parellel argument...

The reason I bring this up is do you fluid dynamics minded souls see a volume or pressure problem with the parallel design?

brant

I do... You can plumb the coolers in parallel, and have only one cooler working.. Fluid will find the path of leat resistance...If one of the coolers has restrictions ( some gunk, a snot of teflon tape, trapped air) the fluid will flow to only one of the coolers.. You wont have and problems with pressure or flow, but you may only be using one of the two coolers you paid for.... a quick touch test will confirm this

Fluidyne coolers are the shizzle... the reason the want you to mount them straight up is again to not trap any air. if the cooler is layed over at an extreme angle, you may only get fluid flow through one or two of the passages..

Ill have to shoot some pics of the install on my 911... I have the cooler layed down at about a 45 deg angle, but it is don in such a fashion that there can be no trapped air..

Also ponder this... the front cooler in a 911 is plumbed in series ( stock from the factory)

Tim,

when I talked with the engineers they explained that they wanted the cooler stood up for maximum air flow reasons and not trapped air inside the cooler...

The guy had a percentage chart and told me that If I bought the larger cooler I was looking at and then laid it back at such and such angle, it would be less efficient than the smaller cooler I did buy and stood straight up.

Maybe its all bunk.. but they were insistent that there would be more restriction and less air flow if I laid it back.....

dunno, but I can say I was totally blown away from spending 45minutes on the phone with the guy and having him go over my whole oiling plans..

I may be way over cooled, but we choose to run 2 (a pair in series) of model # DB- 30617 coolers. They were also able to custom make them with the AN fittings on them instead of the NPT fittings (saves weight don't ya know, to not have an extra adapter in there)

brant

that's true, but your engine won't die because a single-point failure shut off all the flow.

fundamentally, you want coolers normal (perpendicular) to the airstream, especially if there are fins involved. fins (vanes) are just like shutters, and if you can't see through the cooler, the air will have a hard time getting through. the entrained air issue is also significant.

you're gonna hafta s'plain your last point, unless you're talking about coolers on 3,4's and up. on all 911's with engine-mounted coolers, the engine cooler is plumbed into the pressure circuit, and the front cooler is plumbed into the scavenge circuit. they're actually completely separate, neither parallel nor serial - each cooler has its own separate pump ...

3,4's and newer that have no engine-mounted cooler - typically have only one cooler...

(and i agree with the FluiDyne... i'll be running one big RS-sized one behind my RS bumper...)

Here's a little something to get the juices flowing!

Discussed this with a club member today.
Bear with me on this one.

Put the cooler in the space between the fuel tank and the windshield , right under the fresh air intake grill.


Now, dig this...Use the existing air tubes to route the air out the back of the car where the hot air would normally come from the heat exchangers to the front of the car.

With careful planning, you can use this set-up as an alternate cabin heater by shifting the levers on the dash.

Another concept would involve using brass or copper pipe as oil lines to the front of the car in the rocker space.

Flexible hoses would thread onto each end. Using metal pipe would allow heat to escape freely the entire trip.

KT

that all depends on how you get air to the cooler..you want the cooling air to enter the cooler dead on..if the cooler is at an angle to the airflow, it basically makes a high pressure area just before the cooler...ie less air passes through the cooler..

I will of course defer to the fluidyne techs.... they make a great product, and lots of big bucks race teams use fluidyne coolers...

also having the extra oil coolers gives the benefit of more oil capacity, which is a good thing

Okay, now I'm getting confused

If the only reason for running parallel HEs VS series HE's is restriction/back pressure, then crunch some numbers to figure out what line sizes to use to achieve the desired outlet pressure/volume. I still haven't seen anything to show me (pressure, volume, and airflow/temp across the HEs being equal) how a parallel system could be more efficient than a series system.

Sorry, it's a "Missouri" thang.