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View Full Version : rad fan delete?


slimjim
02-25-2008, 10:30 PM
...ok im not saying i want to do this, i personaly dont think the fan gives a big enough restriction to cut your whp, but i got into an arguement about this and it would be interesting to see what u guys think.
first of all, do u think theres a big power increase or an increase at all?
does the aux fan provide the needed air to the rad or is it strictly the air that blows through the rad while driving.
if u deleted aux fan/ condenser and rad fan would u be totally fked for cooling ur engine?

Edit. this is in an e30, if that help.

BmW1819
02-25-2008, 10:34 PM
yea good thread i was debating on this too

Redster
02-25-2008, 11:02 PM
Interesting, but how does this vary from model to model (E39 here)?

slimjim
02-25-2008, 11:08 PM
Interesting, but how does this vary from model to model (E39 here)?

from diagrams, i believe the e39 has the same concept. aux fan>condeser> rad>engine fan. so id think it would be the same.....

Redster
02-25-2008, 11:40 PM
from diagrams, i believe the e39 has the same concept. aux fan>condeser> rad>engine fan. so id think it would be the same.....

Yes it's the same positioning but what about the settings/computer stuff?

It make sense that aux fan is there for a reason so removing it might not be that good?

slimjim
02-25-2008, 11:42 PM
Yes it's the same positioning but what about the settings/computer stuff?

It make sense that aux fan is there for a reason so removing it might not be that good?

ya, probably not, but i weas just wondering if the aux fan is a main source of cooling for the radiator or just for the a/c

Dr. Flyview
02-26-2008, 12:30 AM
lol...the aux fan is electrical guys.

You may see 1-10 more whp (range of what I've heard reported) from deleting the engine (rad) fan but not the aux fan...

You need at least the aux fan for proper cooling and even then you have to get a lower temperature thermostat and a lower temperature aux fan switch.

slimjim
02-26-2008, 12:32 AM
lol...the aux fan is electrical guys.

You may see 1-10 more whp (range of what I've heard reported) from deleting the engine (rad) fan but not the aux fan...

eerm, i didnt say anything about aux fan being belt... that would kind of be hard to imagine... im asking does the aux fan also help cooling too the rad, and if u took it out, aswell as rad fan, would u be screwed?

lol im saying if u took it out becuase i dont have one :)

Dr. Flyview
02-26-2008, 12:46 AM
It helps cool the rad if it gets too hot, or if AC is running it cools the rad and AC components.

I don't see you gaining any power from it, except for maybe pulling less on the alternator?? Actually I always wonder about this cause when I turn my foglights on while idling, rpms dip for a second, so does that mean I'm losing hp with all lights on? lol

Mickey Knox
02-26-2008, 11:43 AM
eerm, i didnt say anything about aux fan being belt... that would kind of be hard to imagine... im asking does the aux fan also help cooling too the rad, and if u took it out, aswell as rad fan, would u be screwed?

lol im saying if u took it out becuase i dont have one :) if you dont have one as in somebody took it out, then you probably want to add that back in if you want to do the fan delete. if your car didnt have one i would think you "should" be fine if you replace the clutch fan with an electrical. (i am speaking strictly from e36 experience / readups)

the aux fan (in a e36 at least) is wired to the radiator temp sensor, if it gets too hot it turns on. it also turns on when you turn on the ac. due to its position it does cool the radiator of course, and it is used as such. in short, yes you are screwed if you take it out, but why would you? its electric and only uses power when its trying to save your engine.


i did my fan delete this winter so i cant say if it works in the hot new england summer yet, but i eventually also plan to do an A/C delet and rip out the compressor and condesator etc.

I also wired the high speed side of the aux fan relay to turn on with my secondary aux fan at the lower of the two temperature the radiator temp sensor spits out (81). this way i have max cooling right away. both fans on seem to be pushing an ungodly amount of air through the rad so i think i should be fine. with the condensator out of the way it should be even better.

btw that thing looks pretty sturdy (condensator) would i need to think up a grill or osmething to protect the much more fragile looking coolant radiator from road debris? all that would be left int hat setup is the kidneys and the aux fan, which i can see letting some small stones through.

Mickey Knox
02-26-2008, 11:56 AM
It helps cool the rad if it gets too hot, or if AC is running it cools the rad and AC components.

I don't see you gaining any power from it, except for maybe pulling less on the alternator?? Actually I always wonder about this cause when I turn my foglights on while idling, rpms dip for a second, so does that mean I'm losing hp with all lights on? lol

In theory you are right, the more electrical power you are using the more "hp" need to be converted from mechanical energy (engine running) into electrical.
but if you figure your fog lights have 100 watts tops, then that converts to0.134102209 HP worst case. They way the cars electrical system is setup, i would imagine there is overproduction from the alternator at almost any engine speed, unless there is a clever way alternators use the left over electrical power to help turn the alternator to reduce drag on the engine, then above will apply with some degree of variance for losses due to resistance and mechanical drag.

all this is based on the principle that all energy inside a closed system can be accounted for. (energy has to come from / go somwhere)

craz azn
02-26-2008, 12:37 PM
Yay for saving all of that 1hp... lol

Wire up a lower temp sensor (81deg) so your Aux fan will pop on if things get out of hand.

98Dinan3
02-26-2008, 02:04 PM
The main purpose of the Fan Delete is NOT to gain power. It is to avoid the notoriously self-destructing fans from ripping holes in the hood,rad,hoses, etc... The plastic fan blades get brittle over time and can come flying off at high speeds. Worn engine mounts and really spirited driving can also cause the fan to strike the rad as the engine moves around, causing it to break. The FDM is mainly a precautionary mod.

From what I've been told, the power increase is only even noticeable when the FDM is paired with a set of underdrive pullies.

slimjim
02-26-2008, 03:57 PM
thanks for othe reply guys. I took my aux fan out myslef becuase it was ceased and now just wondering if it plays a great role in cooling rad, and from ur guys input, sounds like it does, aswell as protect the rad from debry ( never thought about that one) :)

Helka
02-27-2008, 01:17 AM
I have a 94 318i and i did the fan delete mod and i really noticed smoother, faster rising rpm. For power increase imagine spinning an umbrella thats open. Isn't very easy but close it and spins more easily. I did put an electric fan in place of it. I also removed my ceased aux fan. I drove all summer with the aux fan ceased and never had a AC overheat problem. Mind you my electric fan is from a 2.8L engine so it cools my engine down right quick.

Maybe I'm talking out of my ass but it makes sense to me that there would be a noticeable increase in power.

Dr. Flyview
02-27-2008, 01:24 AM
I have a 94 318i and i did the fan delete mod and i really noticed smoother, faster rising rpm. For power increase imagine spinning an umbrella thats open. Isn't very easy but close it and spins more easily. I did put an electric fan in place of it. I also removed my ceased aux fan. I drove all summer with the aux fan ceased and never had a AC overheat problem. Mind you my electric fan is from a 2.8L engine so it cools my engine down right quick.

Maybe I'm talking out of my ass but it makes sense to me that there would be a noticeable increase in power.

What electric fan did you put in place of the engine fan (behind the rad?...shall we say, posterior to the rad? :P)? How hard is it to fit in?

Helka
02-27-2008, 01:28 AM
I placed it in between the engine and radiator. I went to the junk yard and found a fan that would fit in and i only paid $45 for it plus i had to wire it up myself. Really easy. I haven't placed anything where the aux fan was. Just removed it last week. Freed up about 5lbs LOL

Mickey Knox
02-27-2008, 02:03 AM
Yay for saving all of that 1hp... lol

Wire up a lower temp sensor (81deg) so your Aux fan will pop on if things get out of hand.
not even, its 0.1hp