Kento

Agreed. Also should be noted that while units like Summit Racing and Permacool can flow more air, the thickness of their motors requires added space. One need only look at the size of the stock fan motor to get an idea.

I'd tend to disagree with the backpressure concept. There is plenty of space just behind the belly pan that runs underneath the radiator and engine, and the shape of the pan is made to speed up airflow over its surface at speed, thus helping to "pull" some of the engine bay air that escapes in that area.

Regarding the "1st inch" IC heat transfer conundrum, I'd be more inclined to lean towards reason #2, although I wouldn't call it air pressure; more like airflow velocity. As IC surface temps rise, you need more (i.e., "faster") airflow to effectively transfer that heat from the IC fins, and even the biggest fan won't come anywhere close to the airflow that speeds over 30 mph can produce.

I wish I had the room on the engine side of the IC to mount a larger fan like the Permacool unit, but I didn't want to wait months to get an M2/ASP medium IC, so I had to settle for a Greddy, whose intake routing is somewhat crowded. Nonetheless, much better than stock, and I'm not pushing huge boost numbers, so it's adequate.

Radical Rotary Avantgard

Brentis, we are getting deep into the subject now, I like it!
I am not an engineer, but the more electrical comsumption sounds to me to be a not so much efficient motor and has nothing to do with moving air or cooling ability.
The length, width and pitch of a blade is much more important for moving, air even more so than the amount of blades or electrical comsumption, IMHO.
The question now is, why does the industry measures in CFM and not based on current draw????
(Cubic feet per minutes)
Anyways, good discussion.
Have to agree that a vented hood would help tremendously by creating a low presure area behind the IC therefore increasing the cooling ability.

KevinK2

I did simple tests that showed when the main rad fans came on, car stopped, the hot rad exit air back flowed thru my greddy smic, out the IC duct, and back thru rads.

Same issue with just a smic fan on. car stopped, hot air will back flow thru rad, and find it's way to IC duct inlet. Ken, this will happen to u unless u have a very isolated IC air source.

M2 smic have best shot a proper fan fit. My thoughts to avoid smic heat soak when stopped or in traffic:

1) all, esp greddy, need a shroud like the oem ran fans. could be made from aluminum sheet. prevents flow reversal thru IC core outboard of fan. mabe 1/2" min standoff from the core back face.

2) rad fans should be run at low when IC fan(s) is on, to prevent backflow thru rad. The 'fan mod' switch will help, or a simple ground switch fro one of the contacts in the diagnostic connector (TAB?) this puts fans at low speed.

Regarding bottleneck, the smic smallish inlet duct opening is ususally the bottleneck, and as long as you match that area with fan 'open area' size, should not be a problem, even with shroud.

Radical Rotary Avantgard

Airborne, the answer is B.
In my post that is the subliminal message.
You only need the fans for cooling down the IC once it is heat soaked.
When you are at speeds over30 mph it won't do much but hamper flow.
The reason is because the air velocity at 30 mph or over is much more than that of your fan.
So, that is why at highway speed you don't see any improved difference.

airborne

figured. i like fiddling with switches and stuff anyway

Radical Rotary Avantgard

KevinK2, thanks for posting your explanation which validates what I was trying to explain here.
I read your post a while ago and it was clear then to me what was happening.
Agree that the major bottleneck is the narrow shroud opening for air.

LUV94RX7

iTrader: (3)

When you see all those dyno charts on rwhp I wish I could also see what their intake air temps were. I'm sure they are a lot higher on the dyno than when they are driving down the road at 100mph. I'm sure those dyno numbers are really low compared to real world application when the IC is really working. What's the old "rule of thumb" for every 10F degrees cooler the intake you gain 1-2% more power.

airborne

good point.

ech

Here is one big pile of speculation. Have fun:

I doubt that the little IC fans will move enough air to push a signfiicant amount of air through the rad. Maybe a tiny bit (teeny-tiny bit) at standstill. But then when the water gets a little hotter, those fans will come on by themselves - So I don't see a lot of issues. It isn't air-air so there won't be heat soak issues in the radiator. If you have the PFC then lowering the temps those fans come on will help as well.

So "in conclusion" I believe it's more important to get the IC fan to trigger with the rad fans than the other way around - if you have an automated system. If you are going for an on/off switch for max cooling - then I agree - might as well trun them both on.

-----------------

regarding blocking flow w/ a rear mounted fan. The fan I have has minimal housing and sits 1/4 inch off the surface. The intake front end has a very small opening / when compared to the IC face. Airflow will already be fairly slow. I wish I had a better handle on flow, but at 60 mph, the air speed though the fins has to be much slower.

Brentis

From what I read... CFM is a marketing term like watts, and we all know how watts differ, further the comment about the motor efficiency is, per the article I read, a non-factor as motor efficiency hasn't change much if at all in the past 10 years. The article had similar statements about pitch angle.

One other thought, seeing how the radiator fans stay on at speed, wouldn't that tend to indicate something?? If they are not needed and impeed airflow, why hasn't someone designed a solution?

Just pondering..

Radical Rotary Avantgard

Brentis, lets do a subjective non scientific experiment lets match the fans out.
Lets get together and check out how much air is being pulled by placing the hand behind the fan on your IC and my IC fan and come back and report.
PM me or cal me 972-347-2070 h.
Will bring in Bob as a third party.

Radical Rotary Avantgard

sorry double post

Brentis

Also was at radio shack and they have a low cost air flow meter $40. Only measures to 30mph - but could provide some supplementary info.

airborne

was pokin around the net and found the supercharged thunderbirds are frequently modified with an ic fan. this page details the before and after temps fairly well, scroll almost all the way to the bottom

http://www.sccoa.com/articles/cwintercooler.php

Brentis

great article. makes us sound like arm chair quarterbacks..

Radical Rotary Avantgard

Brentis , I am not challenging you, so don't get me wrong.
I am just curious to see what fan realy pulls more air.
I have no problem changing mine, if yours works better.
So give me a call it won't take long 972-347-2070 h.
We can meet for coffee at Starbucks on Park and Preston.
Your call.

That article was way to much for me.
I'm not worthy!!

Brentis

Radical - I didn't even think that - no prob. My IC is currently not installed. I could bring the IC and car battery, but it would be easier if you would want to stop by my house. I'm on McDermott & Coit.

Radical Rotary Avantgard

I go by your hood to get to my office.
I'm an Orthodontist with an office on Independence & Spring Creek.
I"m off tomorrow just in case you want to get together for a few minutes.
Let me know.

7racer

man...you guys are intense...

count me on the Frankenstein project....

I'll be the unbiased observer

airborne

note on that jaycorptech:
i ordered the fan stuff on friday by 2 day air. got an email today saying since it didn't get out that day they bumped it up to next day for me so i'll have it today. thought that was pretty considerate.

LUV94RX7

iTrader: (3)

I ordered mine from jaytechcorp yesterday morning.
I received an e-mail one hour ago with the UPS tracking number. I checked the tracking from UPS and it is scheduled to be delivered today UPS ground. I'd say that's good service. It was shipped from Des Moines, IA to Minneapolis, MN.

Ken

Radical Rotary Avantgard

Luv94Rx7 and Airborne,
post photos as soon as you get them and report your impressions about the fan.

LUV94RX7

iTrader: (3)

I have an Omega gauge and 4 air temp probes. They are located in the K&N air filter, after the turbo, right after the IC and just before the intake after the water injection. I bought a small fan(5.6", 295 CFM) that uses 2.5 AMPs. It will only cover about 27% of the IC surface. My GReddy IC has a pipe that gets in the way for the pull type fan. If the numbers look good I might buy a bigger push fan for the other side to cover more of the surface area. It all depends on my test results. I can take pics, but have to learn how to post them.

airborne

pics are easy to post, just look towards the bottom of the window when you're doing a reply. and it has to be under about 100k.

will do on the pics, have only the pfc's intake temp to measure stuff.

LUV-are you saying you ordered a push style fan?
and bigger picture, why do you need a fan when you have water injection?

LUV94RX7

iTrader: (3)

[QUOTE]Originally posted by airborne [B]pics are easy to post, just look towards the bottom of the window when you're doing a reply. and it has to be under about 100k.

will do on the pics, have only the pfc's intake temp to measure stuff.

LUV-are you saying you ordered a push style fan?

No, it's the pull one. I might add a push one on the front of the IC if my tests on the pull turn out really good.


why do you need a fan when you have water injection?

I would be using the fan to help heat soak at idling in traffic and to cool down the IC when car is stopped and turned off. My water injection will be kicking in only when I'm at 5psi boost and up.

Ken