Cutting stock fans when installing FMIC

[DaveT]

One thing I have noticed when people install FMIC is they cut the stock fan to fit the LICP. I wanting to bring something up and get some input on it. I installed 2 slim fans when I did my FMIC install so I don't know the answer.

Stock, each fan blade on the fan is pretty much identical in mass, so when it rotates, there is no vibration created. When you start to cut the blades, the mass changes. Unless each blade is cut perfectly, the mass between the blades will not be the same. This will induce (when rotated at high speeds) some sort of oscillation/vibration on the fan assembly.

Now the fan is attached to the radiator, which is attached to the car. Because everything is firmly in place and bolted down, when the fan is on, it does not appear to be vibrating. However, that does not mean the fan is not vibrating. That vibration has to go somewhere, ie the fittings on the radiator where the fan mounts. This vibration could (over time) weaken these fittings, causing them to crack/leak.

Now this may be far fetched, but it was just something I thought of when I saw people were cutting their fans. Has anyone seen this before or is it not a problem?

DaveT
92GSX

 

[TD05HTalon]

i believe that when people cut thier fans they are cutting the shrouds - not the blades. I had to cut part of the arms that holds the fan motor to the shrouds in order for my J pipe to clear with the 1G lower radiator hose in my 6 bolt swap. I didn't trim the blade though so there's no problems with messing up the balance of the blades. This of course is a temporary solution until i put one big fan on the front side of the radiator in blow through since i have no AC anymore.

 

[DaveT]

I have seen some who cut the blades. Here is an example:

http://www.dsmtuners.com/forums/showthread.php?t=153438

DaveT
92GSX

 

[Endz0r]

the engine vibrates too, which vibrates the entire car, i really don't think adding a little more is going to hurt anything.

 

[Royalty]

I have seen some who cut the blades. Here is an example:

http://www.dsmtuners.com/forums/showthread.php?t=153438

DaveT
92GSX

yea thats me i didnt ahve the $$ for a slimline so thats what i did for the time being. I'll be gettign a slim line for christmas but i dont see how the cut blades will make that much of a diff for a limited time.

 

[DaveT]

Yeah, that's my question. Is there an affect with the fan blades cut like that? If you loosen the fan mounting bolts, turn on the fan, does it oscillate?

The oscillation may be very minimal and not be an issue at all. I just wanted to get some input on whether or not people have had problems when they cut the fan blades.

DaveT
92GSX

 

[Omega]

The amount of vibration that cutting the blades will have little effect on any structural ridgidity. The rad is secured using gromets that will absorb most if not all vibrations.

You would really have to try to hack the blades up to even notice anything.

 

[DaveT]

I'm talking about the radiator fittings for the fans, where you bolt the fan to the radiator. Will any stress on these fittings cause any premature failure, i.e. cause a leak at the radiator fittings do to a stress fracture? I do not remember, but are there any rubber spacers between the stock fan and the radiator?

DaveT
92GSX

 

[Royalty]

i dont remember and rubber fittign but its a piece of cake to put a silicone bead or a piece of rubber between the fan and the radiator. instant shock absorber.

 

[PaleDSM]

I'm sure there is some weird oscillations going on from butchering fan blades. I doubt it is enough to weaken any of the mounting points though.

 

[98RedGs]

I agree with a couple other guys.
A little more vibration isn't going to kill anyone or hurt anything personally.

I'm going to have to say it will be fine actually.

 

[R3dR]

What geneally happens is the fan weakend its own mounting on the shaft and the fan falls off, most times this will not damage the rad but...

 

[98RedGs]

What geneally happens is the fan weakend its own mounting on the shaft and the fan falls off, most times this will not damage the rad but...

It's a possiblity but it's not highly likely.

 

[R3dR]

I will beg to differ "IF" you have no heat sheilds on and are using the stockers, i have seen it happen 3 times but damage was only done to one of the rads.

The fan is held on by a retaining clip that sits against the OLD brittle plastice that has been heated up alot and now you throw in a drastic wobble ( harmonic vibration)

1+1 is always 2

 

[devlish]

i would think it would cause vibrations and maybe ruin the mounts, but also the fan motor itself due to the off-balance rotation. not to mention, cutting the fan blades probably has an adverse effect on cooling ability as well.