As all you probably know, i have a ej20 turbo subaru in my car. I love it and it runs great, but now i am at the point where i want to streamline how well the system works.......

First matter of attention is the intercooler placement. I have a small water to air intercooler tucked in front of the pulley on my subaru motor. It works great, but i am getting a little too much heat soak on the aluminum tubes leading to it. I was debating an idea of putting it in the rear trunk or in the fender since placement wouldnt be a factor because its a water to air. I do like the one members ORANGE nice turbo car on 914world here with the air/air one in the back and vent in the wing.....

Looking for ideas....

another

Wrap your heat tubes with nasa gold reflective foil.


Works on my GTi with cheaper stuff.

Don't know how much space you have above the intake and under the engine lid, but on my car I used a GT style double vented lid, no rain tray, and a subi intercooler with about a 2" plenum below and an 800cfm sucker fan. Never had intake air temps more than 20-30 degrees over ambient. I plan in version2 to make another plenum, and have 2-1100 cfm fans sucking thru the intercooler. I expect this to cool the intake charge even better, and while it may be a bit loud, its an auto cross car, so noise is not an issue. With the single fan, you can hear it a little over the sound of the motor, but not alot. You can put your hand 6" over the engine grill and feel the air being pulled thru. I think this also helps engine cooling a little, as the IC is located up front in the engine area, over the air intake for the engine fan. More pics can be found in the build thread linked in my sig.

I have the same idea but instead of sucking I was going to use a pusher fan..airflow is bottom to top.. Figured I would try to take advantage of that..???

Airflow is which way? Stock, cooling air comes in through the engine lid. I don't think there's enough natural air flow moving through there to take advantage of... The fans are going to be what moves the air through the intercooler. I would think you would want to pull the coolest air possible through it.

As you mentioned, i put mine in the trunk using 2 fans pulling-sucking the air through.
You wouldn't have to mount it in the far back as i did, mine is there because the turbo
is there also.

airflow studies have been done by someone around here show the that cooling air for the flat flor comes in the bottom..hence issues with big spoilers up front..

Now will I be pulling from the coolest resource,,probably not. but I am try to exploit the natural airflow..and yes that area above the grill is a dead zone...so pulling from the engine bay will pull, maybe, more heat out.. I could possibly duct from the sides for cooler air.. also there are flaps on the bottom of the car to create tubulance to send air into the engine compartment.



Besides if Im dead wrong most of the fans are reverseable!!

according to the huge cloud of smoke that was coming out of my tailpipe while drivin around yesterday, airflow goes UP through the engine compartment. There is a HUGE vacuum right behind the window that pulls the air up. (when there is no engine tin in position, and the exhaust dumps right after the axle)

(my fuel map was running a little rich, that's how I made the cloud of smoke for the test)

Sorry that's just wrong. All the cooling air comes from up top. of course I'm talking stock, not this app. I no clue what happens on a convert.

The "study" shows that the turbulence from the little flaps (under the car just before the engine bay) dissipates the exiting hot air faster, thus reducing temperature.
An air dam could imped this turbulence.

http://www.cassidy-online.com/porsche914/a...2008_poster.pdf

read the engine section. "Air flows up in Porsche 914 regardless of configuration"
"The results of the engine compartment were
consistent with the expected result. Air flowed up
through the compartment for all configurations.
However, the amount of air flow was reduced for
configurations that had the rain tray."
"

Cooling air for a non-stock engine might come in from the bottom.

Aiircooled 4 and 6 cyl engines for street use use cooling tin to prevent airflow from bottom to top, and flaps under the car to promote turbulance and cooling when moving.

Remove the stock engine, engine tin, and seals, and yer on yer own as to which way the air flows and when.

It's a safe assumption that when a car without engine tin is stopped and the engine is warm, that warm air will rise. When the car moves with missing tin, it's your configuration and your test.

There was a guy who placed a subie engine and a radiator in the engine compartment. He built an under-car scoop to get air for the radiator and discovered (big surprise!) that ground air is hotter than air a few feet up..

there is also one that drove cross county with one..!!?? My car is not running and again a simple switch of wires will save me if Im wrong!!!!

The area behind the targa is relatively dead...Im just thinking I might be able to get rid of some extra heat and get air flow by the intercooler at the same time..... I COULD be dead wrong..lord knows it wont be the first time..

Greg,

You didn't read enough...........

Under engine compartment theory it sez......

"Porsche 914 is powered by an air cooled engine.
The engine sits behind the passenger seat and is
cooled by a fan. This fan sucks the air from the engine
bay and sends it out the bottom of the car
The air pressure along the car is
different along its contour. Finding
the coefficient of pressure (Cp)
can assist in determining the
airflow through the engine. A
positive coefficient pertains to high
pressure, a negative one
corresponds to low pressure."

And, it shows a flow picture with air moving top to bottom...

The conclusion supports this view by saying...."The results of the engine compartment were consistent with the expected result."

The author then made a boo boo and said "Air flowed up
through the compartment for all configurations."

Im just going to have to say I dont see it... The area behind the targa is the same as that behind the cab of a pick up...swirling low pressure. I see no dramatic air flow from top to bottom.

To be truthful I dont see a huge airflow up from the bottom either...the stream flows under the car and as per stated the original seals kept top and bottom separated.

I think we need tony to chime in since he has played in real world..

It doesn't matter which way the air would flow naturally. In stock form it comes from above - the tin blocks the bottom off and the fan sucks cool air in through the engine lid.

All that is really a moot point, because you are not going to have a lot of air naturally wanting to flow either direction in such a velocity as to be useful for this application. It's the fans that are going to move the air through your intercooler and natural airflow isn't going to make any significant difference.

Therefor, my point was you will want those fans to be moving the coolest air - obviously cold air works better than hot air. If you move the air upwards, it's going to be coming from the engine bay... a much hotter air source than the outside air you could pull down from above.

I would put it near a cool air source and pull it in from outside. The engine lid is a sensible choice. The wheel well or under the car is dirtier and warmer. Anyplace else you'll have to do some cutting.

Which is how and why my IC ended up where it did- source of cool air, and behind the targa is a spot of low pressure, making the job of the fans pulling cool air thru the IC that much easier, and if pulling air thru the IC would happen to provide a slight air pressure increase to the engine fan, so much the better, since with a stock cooling motor and tins, the cooling air goes from top down.

Aero info: http://www.cassidy-online.com/porsche914/a...aids/index.html

All true, except Budman's car has a watercooled engine and no more engine tin, meaning the air will flow through the engine compartment basically without impediment and probably from high pressure to low. That makes the student's statement "The results of the engine compartment were consistent with the expected result. Air flowed up through the compartment for all configurations" very curious. Curious because their professor's car was aircooled, meaning air flow through the engine compartment could only have been top to bottom, from the cooling fan intake above to hot air exhaust below. This is from the presentation summary and I didn't see a link to the full report, so maybe the "for all configurations" is explained better there.

I'm interested because my car has the same WRX engine with an aftermarket air/air intercooler on top. It's a little different in that I vented the IC opening like this:



In the future I intend to replace the expanded metal on the lid with solid metal, sort of the reverse of doing a GT lid, so the only opening will be for the intercooler. Then I'll do my own tuft testing to see which way the air is being drawn through the engine compartment (high pressure to low) then add a spoiler or two to "encourage" more of that natural flow. For example if the air is flowing up because the lowest pressure is being created by the drop of the top behind the rear window I'll try to increase that flow by putting a little duck tail on the rear of the targa top to create more low pressure there. If it's flowing downward I'll try to increase it by putting a flexible duck tail across the bottom of the car just below the front of the engine compartment. With the closed decklid the intention is to channel all the top to bottom or bottom to top airflow through the only opening, which will be that intercooler cutout.

I'm looking forward to seeing how the flow with fans works out. Just in case. In the meantime I've limited boost to 10 lbs. Also just in case.

Interesting thought, closing off the grilled section, could result in a smooth, cool. custom look for the back of the car. You'll gain a bunch of IC cooling if you can duct the opening in your engine lid to the intercooler. Air will take the path of least resistance, and right now, assuming your airflow is top down, that would be thru the hole in the lid, hitting the IC, and rolling off the sides. True, some will be going thru the IC, but you're loosing alot of flow around it also. To duct the cooler to the lid, and add fans and a plenum below (assuming you have the space) to push/pull, whatever you determine is the correct direction of airflow for that motor in that car with that IC set up, would make for a more efficient IC. I was going to just mount my fan to the back of the IC, and a couple friends, one who is the leading HVAC guy in our town, and another who works for CAT designing IC systems for their earth moving equipment, both got all over me for not using a plenum on the back of the IC to better direct the airflow thru the intercooler, rather than just have the fan blow air at the intercooler. The CAT guy was showing me testing data that where the centerline of the blades was in relation to the plenum was, so in effect mounting the fan on the back of the plenum, inside the plenum, or with the blades even with the back of the plenum would have a measurable effect on the cooling ability of the system. A little to picky for my little project, but shows that having the plenum/ducting makes a difference.

Hey iamchappy.....

What kinda temps are you seeing with your rear intercooler? I think i might go this way and keep my water/air intercooler so i wont need to vent it anywhere. I will save heat in my tubes in the engine bay and be able to make them shorter.....well depending on which larger water/air intercooler i decide to use in the future.

Yes, I'll duct it later when I close in the deck lid. There's space under my I/C for fans, but the hope is that I can manage the natural flow of air well enough that I don't need them. I'd like to get some of the advantages of a front mounted intercooler without needing to put it in the front. It's a different idea, what budman said he wanted. We'll see how it works.

By the way -- nice wheels Dave!

(in your opinion) What are the advantages?

It's that beautiful direct stream of high pressure air, same as for the radiator. They're a lot more practical on front engined cars, unfortunately, but even for front engined cars a front mounted I/C is a big step up from a top mounted one.

I'm re-reading this thread and a coupla thoughts..

You want efficiency or pretty?

If you want efficiency, hang the sucker on the outside of the car in a direction for airflow to pass through it-ie on the roof, deck lid, in the rear spoiler, etc....

Pretty is hide it like yer doing....

DB, what's stopping you from doing a quick test to solve this top to bottom or bottom to top issue????

Can you hang a coupla pieces of yarn on the top of yer intercooler, drive yer car and look at the tuft movement on the top of the intercooler in the rearview mirror at several different speeds??? If the flow is bottom to top, the yarn goes up, if the flow is top to bottom, the yarn stays down...

A piece of cheap posterboard and some duct tape can also cover yer engine grille and might give a more definitive flow answer through the smaller opening over the intercooler with the yarn test- ie: up or down.

Then again, covering the grille may change the flow....

Ain't testing fun??? Airflow is not always intuitive....

My gut says making a smooth custom top with no openings is a heat bomb. Why? Have a nice hard run, get stuck in stopped traffic, and the extra heat has to go somewhere but can't... Warm air rises, and the engine is stuck in a hotbox......If you do the run and stop test with a stock Subie car, the fan kicks on and forces cooling air through the radiator and out of the front engine compartment....

Ken

What, you mean these old things?

Yeah, those. Beauties, aren't they? Nice narrow spokes, love 'em.

Thanks, Ken, but I don't think I'm going to put the intercooler on the roof. I'll put a radiator in it, O.K., but I'm not THAT hardcore.

The car's getting ready to get a Subaru transmission, so it's not going anywhere for a while. Not only that, it's in California and I'm in Texas, so all things in good time. But hey, bingo, that's almost exactly the way I intend to test. Should be interesting. I don't think it'll be a heat bomb, though. It's water cooled and the fans have only come on twice, so I don't think it will be any worse than a stock Soob stuck in traffic. And if you're stuck you're not making boost anyway, so no worries about hot air.

Ken;

I have done quick tests with both of my watercooled 914's. (I know you were talking to DB... but...)

The first one, the radiator was in the engine compartment. We HAD to figure out the airflow in order to get the cooling correct. We used strings.

This recent one, the exhaust pipe from the turbo dumps out right behind the axle and it was running quite rich when I'd put my foot into it. The cloud of smoke from the exhaust came up from the bottom, and out the top.

I'm telling you, airflow in the engine compartment is from the bottom, up and out the top.

DB;

are your engine shelves still in place around the engine compartment? Got pics of your engine compartment somewhere?

I have a few ideas, but want to see your compartment first.

100%

Bob

I don't have photos of that part of the engine compartment, but it's all intact. The only cuts on the car have been what you see in the decklid and in the front for the radiator. And those bits of metal were saved so they could go back in if these cars ever begin to get up to 356 values.

More photos HERE.


Yeah, that's what I've heard, which means I'm going to try a little ducktail spoiler across the back of the targa top to increase the low pressure at the decklid. Can't wait for the CW contingent to see that.

.

Click to view attachmentBudman, since your set-up is water-to-air, the main thing to consider is the placement of your "Exchange core" radiator. Maybe I've missed it...but is that core in a cold air area ? Your placement of your intercooler with the charge pipes visible just behind the firewall would be a bad choice for an air-to-air (however your's is air/ water), the culprit is getting really cold flowing water to the intercooler. You may also want to explore a larger intercooler , the downside is pressure loss of 1 to 2 psi, but the gains ( and engine life) are enormous with a colder intake charge temp. There is no real need to put an air-water intercooler in the trunk, I've seen them stuffed under the HOT hoods of twin turbo supras with no problems. Another downside to trunk mounting is the distance your charge pipes will need to travel...which will also contribute to pressure loss.
The air-to-air that I use works well, and takes approx 130 deg out of the charge air. The charge pipes are also kept short (no pressure loss) as I've built custom plenums facing rearwards. Since you are not running an oil tank, maybe put the exchange radiator in that fenderwell with a naca duct.
Marty

Marty, Clewett and I all put ours back in the trunk, why not air to air, get it out of the engine compartment and give it some fresh unheated air....

Budman I really think the air to air ic in the front that you converted to water is letting the water move too fast through the awic system. The aaic has a different tube design than a radiator which is what you need. Heatsoak can be a real problem though in the engine compartment. I would like to know the water temp from the front entering the heat exchanger in the engine compartment compared to ambient temps. We know the motor is about 200f. If ambient is 100f and the air entering the intake of the turbo is 150-200f, that should be the easiest place to get the temps down. 150 is 50f over ambient. If the turbo is making 320f at high boost and you give it 50f cooler air that is less work for the ic.

You might buy a cheap electronic cooking thermometer and mount the probe in the air cleaner and check the incoming air temp. Then check the incoming water temp to the ic at the motor.

130f air temps may be the best you can do.

Thanks guys. Its really been a hot summer so far so my mods to my newly built project subaru are done for a few months. Now My modded SeaDoo now thats a different story!

I am running a safe 7lbs of boost for now and pump 91 octane gas. The air intake location is probably my first mod to be done, along with exhaust wrap on all the intake and charge aluminum tubes...I'll definately post the results.

Oh also, i think i take your advice Charliew and put a regular heat exchanger up front, possible a nice huge A/C condensor. (that should slow down the flow and actually give it time to cool down.) They actually save about 5 lbs of weight off that air/air converted one i did. I thought heat would be a problem when i installed my A/C, but my temps are still 195 Max when freezing inside and 113 degrees here in AZ.

Avoid the exhaust wrap on the intake tubes as it will keep heat in more than reflect. You want something that is reflective moreso than insulating in its properties.



Kwales:

That is a logical idea, but the issue is with an intercooler in open air the majority of the air will flow *around* the intercooler core not through it!

I have done extensive IAT testing post intercooler and pre, to determine that without proper chanelling of the air into the I/C core, the air will choose the path of least resistance around it.

This has also been verified by myself and others on honda turbo cars. Lots of them like running around with no front bumper and an intercooler core that is 2ft tall by 4ft wide.

These are street cars making 600whp or so and running around my area on 26" slicks on the weekends. The "honda crew" as I call them were having issues with IAT temps and IC efficiency. That all went away with a modified bumper to direct the flow of air into the core itself.

THe lack of bumper and shrouding to channel the air is a problem. Just like running a radiator fan without a shroud, it nullfiies the effects a bunch.

Make sense?

I think maybe some naca ducts in the fenders and perhaps a channel into the hell hole/battery tray or opposing area then placing it there with some shrouding to route heat/air out the engine cover may work.........

Perfect size I/C core for this IMHO is a Ford probe turbo intercooler.




I have one I am using on a Golf Syncro I am building, but it's size and construction look very friendly to fitting in a 914 bay.

You could add a simple circuit with a temp sensor that turns on a few box fans or 12v radiator fan once the IC heatsoaks to pull air in when in traffic.


2" inlet/outlet with a decent pressure drop given it's design and size. available cheap in any junkyard. They came in some mazdas as well. Metal endtanks.

go to the Turbonetics site and check out the Spearco intercooler systems . Even if you don't buy from them , there is a wealth of data to read. By the time you have a pick-a-part intercooler cleaned out, repaired or refabricated, you may as well buy a new properly flowed unit.
Marty

Some solvents, and compressed air to blow out the residue afterwards is fine. If you care enough about the few percent more of efficiency after x amount of years worth of oil is out from the solvent you can get the actual surface clean again.

The key is reusing a proper intercooler, not some ass horrid 80's japanese design that is not bar and plate.

Lots of crap was put on turbo cars that are now in junkyards, but there was also a lot of golden engineering win here and there.

Being able to do this stuff and experiment cost effectively time and financial wise is legit as well.

Let's face it as well, with modern turbo technology and EFI, how much intercooler do you need on a Type IV? How much turbo do you need?

What will you do with more than 300whp in a 914 without extensive aero, chassis work etc?

You can do it the right way, and not go broke, while having a clean good looking setup if you spend the extra time.

Spearco makes good products, but do you need 700-1000$ worth of custom intercooler? No. That money could be properly applied elsewhere with more dramatic results.

Ghuff,

I don't disagree that properly designed ducting increases efficiency on any front mounted radiators -air, water or oil. Colin Chapman proved that with his much copied radiator design used on his Lotus products. Colin found that for front mounted radiators, the proper shrouding design produced a 3-4X cooliing factor. He used shrouding that acted like a scoop and directed high pressure air into the front of the radiator. The shrouding also created a low pressure area behind the radiator for a push-me pull-you effect and much greater efficiency.

The 914 is a different case- engine is in the middle and out of the airflow. Unlike mounting an intercooler in a stream of cool air, the problem is more like putting an intercooler in a box with a small hole in it for airflow and a coupla fans to pull through. If the air flow comes from the bottom of the car, then the air run across the intercooler will be hotter than air drawn from higher up. That says placing the intercooler into a location that can receive cooler air would be good.

One of my suggestions is placing the intercooler in the spoiler. When the car moves, you get high pressure on one side, low pressure on the other, with the spoiler acting as a part of a duct.

Here's a thought. Go back and look at the Lamborghini Countach. The car has the same problem- midship engine, vertical rear window, and cooling in the rear. There were a lot of design changes over the years from the sleek prototype to the variety of later versions where they tried to get the radiators to cool properly. Maybe one of them will provide an idea for intercooler placement.

Since its driven in autocross, why not build a plenum above the engine/intercooler, put a snowmobile engine with a really big fan on top, and suck the car to the ground while cooling the charge....two birds with a boulder!!!!!

You have to cut a huge hole in the side and fill it with an mr2 scoop, they are mid engined to, but make sure you cut the scoop up to make it hard for the mr2 club to identify.

something like this might work ,, mounted low in the engine department


Click to view attachment

Yeah, the "Jim Hall" effect! THERE's an idea that will stir things up!

Greg,

Where did you find that intercooler pic? It looks kinda interesting...

Rob