MR2 Owners Club Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
523 Posts
Discussion Starter #1
I am relocating my intercooler to the stock USDM location, and will be using a 10" fan. Question:

1.) Should I try to pull cool air in from the hood, or push air up from below the car? (I think the air has a slight tendencey to go up from the bottom, but no one has been decisive on this)

2.) Best fan for the job? (SPAL? Twosrus?)
 

·
Registered
Joined
·
648 Posts
You want a puller fan not a pusher. A puller fan is going to pull cool air from the top out side of the engine bay a pusher fan is only going to push the hot air from the engine throught the intercooler. When you race turn the fan off.
 

·
Registered
Joined
·
523 Posts
Discussion Starter #4
Why turn the fan off when racing? (I only autox the car, no drag)

Doesn't the air flow up from the bottom?
 

·
Registered
Joined
·
3,544 Posts
this is one of those forever debatable topics. you'll get everyone's opinions and experiences, but it seems that neither side of the argument can ever produce any sort of EMPIRICAL fact. no fan within any sort of physical dimension which could be deemed useable in the engine bay can produce the same sort of airflow that the car's aerodynamics could produce. now that being said, and saying that i've utilized a fan with my intercooler set-up, i have NOT had a problem with the fan that i used nor with the configuration i've chosen to utilize although many have said in the past that it would not work. it was also said in the past that the intercooler i have chosen to use and in the factory IC location (which is where i installed it) would produce no good results. in fact, i got the lean-out from just installing the same-said intercooler (fan was there even on the OEM IC) with no other changes to the boost. go figure. so, whatever.
 

·
Registered
Joined
·
523 Posts
Discussion Starter #7
What fan setup are you using? ie push/pull from top/bottom?

Good points. My rough calculations give a 1000 CFM fan about the effect of 11 mph. So I guess, if you're going faster than that, and the i/c is in the airstream, the fan would cease to be a benefit.
 

·
Registered
Joined
·
6,057 Posts
Jim King measured intake temps on a big pulley SC at a hot lap event at Streets of Willow Springs. It was a pusher from underneath to assist moving air out of the engine bay and out the top of the lid (WITH natural air flow).

With the fan on/off on successive laps (IE same ambient and driving conditions) the intake temps were 20-40 deg. F lower with the fan on. That's hard data to argue against. You might say in the fan off position natural airflow was impeded by the fan, but I just can see that making a 20-40 deg F difference.

I modified my AC radiator fan (I am cheap and did not have AC any longer) to fit under the IC. I had my rear glass out of the car and was able to directly observe/feel (with my hand) the airflow with and without the fan coming out the lid vents. A LOT more air was coming out with the fan on, even at 65 mph.
 

·
Registered
Joined
·
6,057 Posts
wyowrx said:
What fan setup are you using? ie push/pull from top/bottom?

Good points. My rough calculations give a 1000 CFM fan about the effect of 11 mph. So I guess, if you're going faster than that, and the i/c is in the airstream, the fan would cease to be a benefit.
Just curious about the calcs: Did you calculate that 1000cfm was moving 11 mph given the open area of the vents in the lid? That would have to be equated to the opening that is letting in natural airflow in at higher speeds (small intake surface area), which then slows down considerably as it exits a much larger opening (lid vents).

Also, remember that even at 60+mph the side vent on the SC that sticks out into airflow doe not stick out very far, so the CFM will be directly related to the size of the side vent that is perpendicular to the airflow. You could calculate the CFM of air entering the side vent (not based on the opening perpendicular to the surface of the car, but parallel). This is a small area, as it sticks out less than an inch into airflow. I am not sure how much air comes from under the car (being sucked up form underneath the engine by the low pressure zone on the top of the lid). That is a another story that is probably much harder to figure out.
 

·
Registered
Joined
·
7,127 Posts
I see how the pusher fan would be more beneficial, it basically directs the natural air flow from under the car to where it has to go once you're up to speed.
 

·
Registered
Joined
·
523 Posts
Discussion Starter #11
My calculations are way simple, and assumed a front mount location. And I don't think they are very accurate in that sense either, but they give you a feel for how much air is being moved by a 1000 cfm fan.

again, I know this is simplified:

A cubic foot of air traveling at:
1000 ft/min = 1000 cfm

is equal to...
60 min/5280 ft * 1000 =
11.36 mile/hour

I think this logic is flawed though...

However, if the effect was 20 mph or so, this would be a good arguement for not doing the tranny mount, for autox (since the avg speed in autox is around 25).

Anyone using a CO2 i/c sprayer? JustDSM, you still have that bottle?? LOL
 

·
Registered
Joined
·
724 Posts
ToyotaTechGeek said:
this is one of those forever debatable topics. you'll get everyone's opinions and experiences, but it seems that neither side of the argument can ever produce any sort of EMPIRICAL fact. no fan within any sort of physical dimension which could be deemed useable
Actually there has been some good data recorded. I can't remember the guy's name, but a few years ago on the SC list, someone measured the air flow through the IC with no fan, and then repeated the experiment with a puller fan (sucking in air from the top). The results were very clear that even at highway speeds, there isn't a lot of air going up through the IC, and worst yet it's hot air. The puller fan moved A LOT more air throught the IC and the bonus being it was ambient temp. When comparing a pusher and puller fan, the pusher will move slightly more air, but it will be quite a bit hotter. A went over this with an ME friend of mine at work that is a heatsink/cooling solutions expert for our server processors and he confirmed that given the tradeoff, you always go with lower air temp over air flow for maximum cooling. This is why I run a puller fan.

Believe it if you like. Bottom line is any fan is better for no fan.

-Rob
 

·
Registered
Joined
·
3,544 Posts
oh i have no doubt that fan is better than no fan. i have a fan. i think i remember those 'tests' along with the arguments about the airflow and the engine lid being open and such and how the airflow created lifted the engine lid and such like that. i just think that the tests need to be replicated and yadda yadda yadda.
 
1 - 13 of 13 Posts
Top