I hope this works (you can see the pic).

According to my logic, adding a pull fan above the IC can only help. I have no blocker right now above the intake, so the air would easily fill the engine compartment.

http://forums.pelicanparts.com/uploa...1162618931.jpg

feel free to flame me for this but could the cooling properties of an ac system be used some way to cool the ic?

Yes, but it would cost you more power than you can make. The A/C makes heat (which needs to be radiated off) and requires power (to run the compressor). It also adds a lot of weight.

A good idea once we discover super-efficient A/C systems.

I like the logic - 'cause it agrees with mine ;)

I put on my aero hat from the Boeing years + the properties of the tail area and it all adds up - do it

I will be adding a pusher fan(s) *below* the 965 IC - more room below on my setup than above -

If you add a pusher fan you will be pushing engine bay air through the IC and not outside cool air. This plus the aerodynamic effect of the rear deck lid will be completely negated. Why do you think that the engineers in all of the automotive companies decided to pull the outside air in instead of pushing the hot air out through the radiator/IC? I have heard the same argument about the AC condensor in the engine bay that if you wanted a helper fan it should be a pusher. All you have to do is feel the air coming out of the engine compartment in traffic to realise that this is a no brainer. What would make more sense would be to route the IC discharge air out of the engine bay without any restrictions and be discharged over hot componets such as the turbo or manifold area. Where am I going wrong on this?

* The air in that area of the engine isn't really that hot. There is a large rubber gasket designed just to keep the "hot" stuff (exhaust, CAT, headers, etc...) from heating up the "cool" stuff (intake, intercooler, etc...). I will be moving so much air that my temps will be nearly ambient.

* Porsche wanted a high pressure area above the spoiler to force air into the intercooler and reduce lift and drag. In stock form, the air isn't very high pressure up there (preventing it from being forced through the intercooler). My fan will INCREASE air pressure in this area, aiding aerodynamics and engine cooling.

* "...the engineers in all of the automotive companies decided to pull the outside air in instead of pushing the hot air out through the radiator/IC?" Because the engine is in front on most cars, and blowing air into the wind doesn't make sense.

* Yes, it makes sense to dump post-intercooler air out of the engine compartment. However, that doesn't solve the relatively low natural flow of air through the intercooler - the fan does.

Agree on all points with Emission.

Data point: "Engine compartment air" is at MAX 14 degrees warmer than ambient - avg about 7 or 8.

Its great that Craig did some measurement first :D

Now for 7-8 deg, say 10 deg, warmer. Is it worth adding extra weight fairly high up? Wouldn't an efficient intercooler gives you near same "eventual" performance without all the complexity, reliability, weight, ....

The original design has the engine fan pulling air thru the IC (as well as through the AC) and across the engine.

Well take me through this like a child. You're pulling air from the passenger side of the lid to the drivers side of the lid. How are you actually improving the high pressure on the whole tail? Furthermore, if it is the case that you are pulling air up through the IC, into this admittedly higher pressure area, won't it be inefficient by definition? Note Jim's numbers. There is a slight pressure gradient from top to bottom of the IC.

From an aerodynamic point of view, it might be beneficial for down-force at the tail to suck air from between the road and car to above the teatray, but would a tiny fan like that move anywhere near the CFM to actually see a noticeable difference?


See my first observation. The air through the intercooler is being sucked by the engine fan.

Emission, why not simply block off the AC side as previously suggested? Probably be easier to fab, won't potentially harm the IC, and cheaper.

At speed, I can't see this diagram working. At under 30? probably but not at speed when the pressure from the tail is in effect, I can't see it.

http://forums.pelicanparts.com/uploa...1163310274.jpg

There is not much high pressure on the tail grill area.

I've pretty much settled on a pull type fan (installed under the IC) to augment the current 'one-way air direction' setup I currently have.

The engine fan draws air in from many locations. Engine side skirts, back skirt, lid join area, etc. 'Leaks' if you will. Theoretically the engine fan - if (somehow) sealed so the draw is through the IC only - would be the best solution by far. Yet the above variables don't allow it.

My solution is different. A pull fan, drawing air down, mounted beneath the IC. Enhance what is already happening - AND can be quantified, back-to-back via on/off switch.

A 10" SPAL fan will pull 1070 cfm through the intercooler (out of the engine compartment). Add that to the cfm the engine fan is pulling in (3000+ cfm?)... and you have quite a few cfm's that must be pulled through the opening in the grill (or from other "leaks"). The way I see it, that's a lot of fresh air.

* You are getting cool air into the intake.
* You are getting cool air into the engine.
* You are getting cool air through the intercooler.

Sure, it is a bit more complex, but I really don't see where the logic fails (I'm not a scientist, so tell me if I am nuts).

With the open grate blocked off so all air is forced through the intercooler, the intercooler would benefit, but the engine and intake would be taking in "post intercooler" warm air.

Oh... one more benefit. When you park your 930, the intercooler becomes a huge heat sink - takes a lot of time to cool down. With the fan, you could pre-cool the intercooler at idle (in the hot pits)!

lets let craig try it and be done with it! sounds interesting whatever way we look at it. if its wrong we can all laugh at him, if its right we can all say that we agreed with him in the first place!

I'm not going to be rude and laugh, but my difficulty is with a fan that draws air from the engine area out rather than into it. I mean, have you felt the draw the engine fan produces? If the engine is at full song at even 4000 rpm, youll have a fan trying to push against all that air coming in. It almost seems like it hasn't been thought out completely. No offense.
If there is downforce at speed, it seems logical to my aerodynamicaly simple mind that there is some higher pressure there. Isn't force measured in some sort of measurement of pressure? I know my car has downforce in back cause my front end is too light (I don't have a spoiler yet).

Downforce to the rear of a 911 functionally doesn't exist - if anything, it is the lack of, or more accurately , the reduction of - lift.

There is so little 'action' under the wing of, say, a 3.8 tail that it is practically a joke. Not much lift, no downforce, just essentially air 'guidance' (to reduce lift) via the tail itself.

So what will *I* do? A pull fan, under the IC. Bought one a year ago ;-) It does kinda bug me to have the IC air go into/over the engine, but the other solutions seem to have too many oddities and problems. That said, I still think a fully open tail grill with a set of push fans under/or a set of pull fans on top of the IC would work just fine - and provide ambient air to the engine and cool the IC quite well. Hell, I just may give that a shot someday.

So there ya go, that's my dos centavos.

1070 cfm may seem like a lot, but at speed?

The empiric test by Jim on the first page suggests that there is a top to bottom gradient across the IC (with the pass side blocked). This suggests a little down force, not just an absence of lift.

Taking air from one side of the tea tray to the other makes little sense to me in terms of pressure (what you posted at the top of this page).

The engine fan is pulling some air through the IC if there is positive top to bottom pressure, and certainly could be "helping" if it was completely neutral pressure gradient. Therefore, Craig's idea of a pull fan below the IC (top to bottom flow) makes some sense.

Is the ambient air that much hotter after going through the IC? If Craigs temps are to be believed (I don't see why not) doesn't sound like it. Furthermore, aftermarket (larger IC's) tend to lower engine temps at least by oil temp, suggesting the gain from charge cooling outweighs any potential negative (in heat terms) to the engine cooling air.

It seems that it would take a heck of a lot of machining to close all the holes, and huge volume fans (unless you added radical skirts/front spoilers), to suck the air from below the car up on top of the teatray to create really prominent downforce.

The air temp I mentioned is NOT post IC air temps - it is just temps off to the side (inlet) temps.

Keep in mind I now see upwards of 130-150 *post* IC temeratures. The air drawn from/through the IC resides directly over the fan - FWTW. One wonders what the air temp below the IC is - not that it really matters.

I think a fan (or two or three) pulling air downwards through the IC presents a nice opportunity to futher cool the IC in a way that is really not possible with any other configuration.

With added weight of fans, has anyone thought about water intercoolers? You could put a radiator in front with lines bringing liquid to the cooler in back and you could place the cooler more out of the way, or at least not over the engine in such a dramatic hide and seek kinda way. Plus, you wouldn't need to worry about the hot or wormer air coming out the bottom of the intercooler. I have asked this before and gotten don't bother with it answers before, but I kinda like it.

FYI, RUF found out long ago with the CTR that there is so much air coming into the engine bay at speed that it actually becomes pressurized. That is why they ditched the NACA ducts they had on the side because air was being forced OUT of them from the engine bay. If that much air is flowing into the engine bay you do not need any kind of fan at speed. Just block off the rest of the tail around the i/c and your set.

Actually the NACA ducts on the CTR were in a position that external low pressure caused them to reverse air flow from the intended out-to-in direction. The engine compartment isn't pressurized at all.

Not being a d*ck, this is just the truth -