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JohnJL's Avatar
 
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Pulling air through the intercooler?

Just sitting idly by the laptop waiting for Gerhard to finish up my intercooler and was thinking about taking the intercooling a step further.

Here's whats in the mail from Bell...




Has anyone measured the difference in intake temps with/without an intercooler "pull" fan? I've got ~4.5" of room under the intercooler if I mount it high up against the tail grill.

Any results out there from using something like one of these?



1,250 CFM, 12" diameter 9.5AMP 2.25" thick...$110.00

Seems like a foolproof way to ensure as close to ambient air temps as possible, which must be good. Especially at ~1.4 Bar.

Any thoughts?

Oh, this is the toil its going under...would be nice to not worry with shrouding.

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Old 02-11-2009, 04:01 AM
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I don't know if this helps you or not but the 993tt's have the intercooler seal to the decklid so the engine fan pulls air through the intercooler...and when that white 964 with RUF wheels was reviewed by Excellence (with a 993tt motor) the made mention to Porsche's efforts with it and they duplicated it on the 964 they built.

So your theory is sound and has been done before by Porsche - so it makes sense.
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Old 02-11-2009, 05:05 AM
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There is a fan already attached to your engine that pumps about 2800 CFM. Be sure the only path into your engine bay is through the intercooler and you're set. That's the advantage Porsche has with intercooling, it's forced air. Check your rubber seal between the sheet metal and body. Also there is a gap between the shock tower and bulkhead that about as thick as your fingertips that runs the width of the bay. Stuff some foam in there to stop the hot air from entering from the ground. This keeps the dirt out of the bay too. As previously mentioned, be sure there is good seal between the top of the intercooler and the wing. Put a light under the car at night and look for paths for hot air to migtrate up from under the car. This is especially important in stop & go traffic. Air is lazy, force it to go through the intercooler by giving it no other choice.
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Old 02-11-2009, 05:34 AM
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I agree with 930turbo. You should use the fan that is already on the engine. You should spend more time sealing the intercooler well to the wing so that all your engine cooling air must be pulled thru the intercooler. This is a mistake that many people overlook when installing aftermarket coolers.
If you just put on an electric fan and don't seal it to the tail anyway it will not do alot of good, just pull air directly in front of the fan blade diameter. You may even be able to take advantage of the high pressure area over the tail to help force more air thru it when the car is moving.
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Old 02-11-2009, 06:34 AM
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I don't understand the logic that the engine fan draws air through the intercooler, i'm not saying is is wrong but it doesn't make sense to me.
Surely air will find the easiest route, it would therefore draw it's air from below? I would have thought that the intercooler shrouding to the tail is to force the air being pushed into it by the forward motion of the car, no shrouding and the air would blow all around the intercooler.
Somebody educate me to why i'm wrong (i will not be shocked to find that i am)

Edit: Wouldn't it be a good idea to have a moulded shroud under the intercooler to the fan on the engine, so that the fan REALLY draws air through the intercooler?
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Old 02-11-2009, 06:41 AM
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I tend to have the same thought as jbl. The engine fan blades are at a 90 degree angle to the intercooler. Sure the fan is moving air but without a shroud I find it hard to believe that the engine fan is moving enough air to actually cool the intercooler at it's current angle. It was always my thought that the intercooler is cooled by moving air generated as the car is goes faster. Hence why a fan should be placed above the engine when doing a dyno run.

A real simple/cheesy test would be make sure the cooler is sealed then put a piece of paper on top of the intercooler. Close the lid then see if the paper is being sucked to the intercooler. If it's not the I'd say that the engine fan isn't pulling as much air through the intercooler as one would think.

Or for the non cheesy/cheap approach we can get more scientific and use an anemometer to measure the coming from the top of the intercooler. You would need something like this http://www.crosse-technology.com/ea3010u.html

Last edited by osiris2600; 02-16-2009 at 09:39 AM..
Old 02-11-2009, 07:13 AM
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Quote:
Originally Posted by JBL930 View Post
I don't understand the logic that the engine fan draws air through the intercooler, i'm not saying is is wrong but it doesn't make sense to me.
Surely air will find the easiest route, it would therefore draw it's air from below? I would have thought that the intercooler shrouding to the tail is to force the air being pushed into it by the forward motion of the car, no shrouding and the air would blow all around the intercooler.
Somebody educate me to why i'm wrong (i will not be shocked to find that i am)

Edit: Wouldn't it be a good idea to have a moulded shroud under the intercooler to the fan on the engine, so that the fan REALLY draws air through the intercooler?
Your on the right track. You need to force the engine fan to draw cool air into the engine bay. That is why you must be sure the seals separating the engine from the exhaust side of the car (the road side) are pristine. Someone alluded to this in the post earlier.
The only way then is thru the tail opening.
Now you want to limit air bleeding around the intercooler by sealing it in similar fashion. The only drawback is that you are preheating the air slightly that is now being blown over the engine to cool it, but this is of less effect than providing cool air into the intake manifold via the intercooler.
Of course you need a little free air insie the engine compartment for the air filter box, so you leave some venting in the tail near the air filter opening to let air in for that.
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Old 02-11-2009, 07:17 AM
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The engine fan creates relative low pressure inside the engine bay. The air will creep in from anywhere it can, including around the top edge of the intercooler if it isn't well sealed. The 911 is the only car on the road that you can pre-cool the intercooler while sitting at a stop light. Just rev the engine. To give you an idea how much air that fan moves, try standing behind your car bare-footed and rev it up. I bet you won't stay there long :-)
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Old 02-11-2009, 07:30 AM
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Pull fans under the IC, 110%. I've done all sorts of experimenting in this area.

The engine fan concept does a mediocre job AT BEST - the routes for air pulled into the fan are numerous - and cavernous (hey, it rhymed):

Sides & top of the engine lid: Huge areas for air to come on in, and it does
Sides of the engine: Despite the rubber side skirts, air flows on in, easily. And it isn't cool air.

Air leakage on a 930 engine compartment - fans take care of this.
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Old 02-11-2009, 08:08 AM
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SPAL fans - many sizes to fit the varying clearances under the IC.
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Old 02-11-2009, 08:09 AM
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I built a shroud for my intercooler as I knew air was going around it instead of through it.
HUGE difference. At idle I can put my hand on the intercooler and feel the air pulling it down. I left a slot near the air filter which the fan also pulls air in right past the filter. The filter now gets more dirty in that spot where before it got dirty from behind as air swirled around the engine bay.
My vote is to seal up the engine compartment and intercooler first and see how it does for you. It has worked very well in my application. Turbo lag has been noticably reduced and power increased. Dyno runs suffer however as the lid is open.
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Old 02-11-2009, 09:59 AM
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Yep, big difference for me, too. Just not big *enough*.
I've screwed with this stuff for many hours.

Very, very difficult to seal up the engine compartment. Next to impossible with way too many gaps everywhere. As Brian did, let the engine fan draw air over the air filter gap so that inlet is within 14 degrees of ambient (mine). Shroud the rest.

Installing fans is fairly easy, about a 2 hour job start to finish, switch and all.
Dyno runs with sensors etc usually require the lid open and a 110v fan should be strapped to the IC for these runs anyway. Gratifying to see IC temp increases of only 15 degrees after a dyno run. Then they'd go right back down.

All this said, shrouding is a great first step and all that is required for most folks.
Fans will get rid of 'car sitting after engine running' heat buildup - very quickly .
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Old 02-11-2009, 10:10 AM
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I hadn't thought about the dyno aspect. Perhaps we should be running with the lid closed.

The engine fan should be drawing a lot more air through the intercooler than a fan sitting on top during the dyno run.

Of course this could be a problem with some dyno's RPM sensor.
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Old 02-11-2009, 11:38 AM
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Run with it open - the large floor fan bungees nicely on top of the IC.

The fan pushed a TON more air and is much more effective than the engine fan - in actual practice.

I've shrouded and gap-filled and ran both ways several times, hands down the fan made a huge difference in inlet/outlet temps - according to the IC temp gauge.
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Old 02-11-2009, 11:49 AM
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With everything properly and complete shrouded, the engine fan WILL pull more than an adequate volume of air to cool the IC. However, as others have stated the task of doing so isn't as easy as it seems. Boot seals, engine tin, harness and oil line boots, and rubber lip seals all need to be in perfect order with virtually zero leaks. On a car as old as most of ours, a majority of these things have shown their age, or are non existent all together. I can't tell you how many 930/965's I've worked on that are missing the engine bay block off tin all together. Those cars are surely drawing a majority of the cooling air from under the car!

There isn't a downfall in my opinion for using a SPAL or FAL type puller fan on these cars to draw air into the bay. If you have adequate space it's very worthwhile and the cost isn't that bad. I'd suggest that if done, proper steps are taken to create a good shroud for the fan to allow airflow to be pulled across the entire face of the core. A flat sheet covering the core with a cutout for the fan is not a proper shroud. Obviously setup and space constraints are going to be a per car basis, but if you can get one in there it's worth the cost and time in doing so.
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Old 02-11-2009, 06:21 PM
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Quote:
Originally Posted by RarlyL8 View Post
I built a shroud for my intercooler as I knew air was going around it instead of through it.
HUGE difference. At idle I can put my hand on the intercooler and feel the air pulling it down. I left a slot near the air filter which the fan also pulls air in right past the filter. The filter now gets more dirty in that spot where before it got dirty from behind as air swirled around the engine bay.
My vote is to seal up the engine compartment and intercooler first and see how it does for you. It has worked very well in my application. Turbo lag has been noticably reduced and power increased. Dyno runs suffer however as the lid is open.
I tend to agree. Let's not forget this is all about physics and the path of least resistance. A small opening has much more resistance than a large one; thus, most of the air coming in to the engine bay will be drawn from the top and through the intercooler before being blasted downward across the cylinders and heads. Not to belittle the smaller leaks, but they are...after all...small peanuts in the scope of things. Seal the intercooler to the lid as best as possible, and you'll have a virtual vacuum cleaner suction pulling though it. My two pennies.....
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Old 02-11-2009, 06:44 PM
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My solution

Here is my solution. I have a B6 965 intercooler. I am of the opinion that blocking off air to force it through the intercooler just limits the amount of cooling air available to the engine. I KNOW I am getting a LOT of air through the intercooler with these fans. I have not used a pyrometer, but the low tech hand touch method shows a substantial drop in temperature across the intercooler. I had to make my friends feel it at the last DE, they were amazed. I can also run the fans a few minutes before the next DE session. This pre-cools the intercooler. You know these intercoolers become a big heat sink in between runs. Why start out with a heat penalty? Due to interference when closing the tail, these were the only places that fit. There is no room under my intercooler so they had to go on top. I know it's not beautiful, but it sure is effective.

Old 02-12-2009, 06:02 PM
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Thanks Turbodog

What model are those?
And whats that Diet Coke bottle? Oil catch can? Does Diet make it lightweight?

Regs here are to run a 2L catchcan...will be learning to TIG this weekend building one under Paul's direction...
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Old 02-12-2009, 09:48 PM
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Heh...... ;-) looks familiar - I use a Mobil 1 bottle as a catch can.

Position one fan under the inlet portion; heat conducts through the turbo to IC pipe and saturates the IC in this area.
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Old 02-13-2009, 06:51 AM
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The fans are Spal low profile. http://www.spal-usa.com/ I run the power from the starter and use a relay for control. The coke bottle is an emergency solution to a problem that showed up at the track. Only when driven in anger does the oil go through the breather and into the intake where it trashed my air filter. I use diet coke for the weight savings. Can't use a Mobil 1 bottle. not enough ZDDP. Really sharp eyes will see a cool collar, a gift, which I figure drops my oil temps by 30 or 40 degrees. Seriously, if you want to move air, use a fan. Or fans. The 9 inch Spal low profile fan fits in the stock 78-89 intercooler perfectly.
Old 02-13-2009, 10:04 AM
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