which is more efficent, push or pull type thermo fan setup??

[oldcorollas]

Interesting post, I knew pull was more efficient, but not by 15%.

Permacool say pusher is only 80% of puller
http://perma-cool.com/faq/efans.htm

Flex-a-lite say 10% more for puller
http://www.flex-a-lite.com/auto/html/4-wheel.html

i can't find the reference i saw many moons ago, but i remember something about 15%.. there are probably research articles around


flaps, like these but better designed and more area
http://www.wellerracing.com/pictures...20radiator.jpg
http://image.hotrod.com/f/techarticl...hallenger+.jpg
http://i46.photobucket.com/albums/f1...y/100_4141.jpg

[Robbos_Toyotas]

mate i recon you're mad - replace the hydraulic fan pump - those hydraulic fans are monstrous! no thermo fan willl pull even half what that would....im putting a 1uz into my hilux and am having a custom radiator made so i can fit the hydro fan - i know itll never get hot doing hill climbs/ long steep low range crawls. Same with your 1j - if u want to take it out on the track thermos will be useless compared to the hydro fan....

[matty12]

^^^^^yes, yes and yes!!!!

[The Real Roadrunner]

SPAL rate their 14" fan at a higher cfm when mounted as pull instead of push.

Only due to the fact that the pull type runs a bigger motor and is 24mm thicker.

read the catalogue properly and if you compare the same motor and blade designs the pull and push has no difference in CFM rating.

i personally prefer a pull setup but if you want a neat engine bay or are restricted in the amount of room a pusher will still do the job fine.

Cheers
Linden

[mullett]

mate i recon you're mad - replace the hydraulic fan pump - those hydraulic fans are monstrous! no thermo fan willl pull even half what that would....im putting a 1uz into my hilux and am having a custom radiator made so i can fit the hydro fan - i know itll never get hot doing hill climbs/ long steep low range crawls. Same with your 1j - if u want to take it out on the track thermos will be useless compared to the hydro fan....

Very big difference between a low-speed 4wd and a track car. A fan is next to useless over 60km/h, if you could drive without stopping, you wouldn't need one... The only time you need a fan is low speed, idling, etc.

my 2c

-RM

[RA35GT]

Only due to the fact that the pull type runs a bigger motor and is 24mm thicker.

read the catalogue properly and if you compare the same motor and blade designs the pull and push has no difference in CFM rating.

i personally prefer a pull setup but if you want a neat engine bay or are restricted in the amount of room a pusher will still do the job fine.

Cheers
Linden

I was going of a drawing I had for the 14" I have, which has one drawing for both (I assumed they were both the same except for blades and wiring, guess I was wrong here). At the time I read that the puller had a higher airflow, but I can't find where I read that now.

[matty12]

that not 100% true in all cases i dont think altough I did think the same though.For example,pulled my clutch fan of my hz 308 one day chasing a vibration and drove it around the block(semi rural area) about 60/70 kmh,she steadily got hotter until i got home,well above normal operating temp.

Another example,drive the busted ass work hilux down the freeway(100kmh) on a 30cish day with the a/c running,i could clearly hear the clutch fan start to drive for about 30 sec or so.

[river]

Hi,

If your fans are coming on when driving over 50 or so kph then you have a problem with your system. Fans should only come on when there is not enough air flow through the radiator. Furthermore, having a fan come on at 100kph is pointless as I doubt it would suck (assuming a pull fan) a 100kph blast of air, so I can't see if providing any additional airflow at 100pkh as that speed will push air into the radiator faster than the fan can.

CFM, being a push or pull fan is a ncie figure to look at, but that's like hp or kw of an engine at the fly wheel... sounds good, but in practice it is lower than that due to obstructions, etc.

seeyuzz
river

[oldcorollas]

read the catalogue properly and if you compare the same motor and blade designs the pull and push has no difference in CFM rating.

this is true, until you put the load (ie radiator) on it. It is the pressure increase vs pressure drop of the radiator that changes the amount of air it actually flows in push/pull, not the blade/motor.

surely for a dorifto car, you would be better off having a big fan, for when you are sideways, and having cheater holes in the shroud for when you actually go fast enough and have enough air coming in, to provide more air than the fan can pull...

ie, it's not like when you are driving in traffic, more like a moving burnout comp, so thats more the style of cooling setup you need to think about

[MWP]

read the catalogue properly and if you compare the same motor and blade designs the pull and push has no difference in CFM rating.

The CFM ratings are probably measured when in free air, not when mounted to a radiator.

If your fans are coming on when driving over 50 or so kph then you have a problem with your system. Fans should only come on when there is not enough air flow through the radiator...

Correct, but it can depend on the car front & coolers design.
On my GT4 after adding the FMIC, the fan does come on more regularly than it used to when driving around town.
People often forget that adding a FMIC or other coolers infront of the radiator can impede air flow (and heat it) somewhat.

[mullett]

This is true, but the fan is only on a heat switch, so your engine is definitly getting hotter, but the fan probably isn't doing much to help when you're at speed. I'd be surprised if the fan circuit was smart enough to read road speed etc and take it into account.

-RM

[matty12]

Hi,

If your fans are coming on when driving over 50 or so kph then you have a problem with your system. Fans should only come on when there is not enough air flow through the radiator. Furthermore, having a fan come on at 100kph is pointless as I doubt it would suck (assuming a pull fan) a 100kph blast of air, so I can't see if providing any additional airflow at 100pkh as that speed will push air into the radiator faster than the fan can.

seeyuzz
river

See, i used to think the same but it also comes down to load on the engine as well.I also know there is nothing wrong with the system aswell(BTW it has a clutch fan not thermos).I would really like to know how much "ram air"you are actually getting from behind a grill/condensor/intercooler/front bumper etc,i dont think it would be as much as people belive it is.But this is getting slightly of topic from Thors original question.

[The Real Roadrunner]

this is true, until you put the load (ie radiator) on it. It is the pressure increase vs pressure drop of the radiator that changes the amount of air it actually flows in push/pull, not the blade/motor.

Agreed. Hence why i said they had the same rating not that they have the same actual airflow.

Dorifto cars suck arse to keep cool, especially when the morons stack 5 coolers one infront of the other. meh all ways managed to sort them out in the end.

Cheers
Linden

PS good to see you back here Stu

[charliechalk]

To give you an idea on losses for something completely unrelated but slightly the same , this is a comparrison between two amca standards the higher curve is a bellmouth with ducted inlet to the fan and free outlet, the lower curve is bellmouth with ducting behind the impeller. Generally if you can allow a large length of ducting to your radiator with a push type fan you can minimise the difference but obviously that's not possible in a car. Rotating high pressure air is not your friend when trying to go through thin straight channels, or even just plain old ducting.

http://users.tpg.com.au/caburg//amca.pdf