540i Viscous to electric fan conversion

[Silvercat]

Anyone done this by any chance? If so I'd like to know if the shroud has to go - I'm looking at a 17" fan which may or may not fit within the existing shroud. (Can't measure it at the moment because there is a 1000 or so km between me and the car) I suppose the main reason for keeping the existing shroud is that it has hose fastenings etc as part of it's structure.

[bmwmech1]

I just picked up a 95 540i Sport and this is on my short list of things to do. Keep the shroud, it helps with the efficiency of the fan and reduces hot spots in the radiator core. I'll post back a reply when I get the pieces together to do the swap. Here's a pic of the new ride...



BMWmech1

[Silvercat]

OK I'll wait until you know more. Do you know the diameter of the existing fan by any chance?

Many thanks!

[Silvercat]

Originally Posted by Silvercat

OK I'll wait until you know more. Do you know the diameter of the existing fan by any chance?

Many thanks!

I think I can answer my own question on size. According to Pelican Parts a replacement fan is 18" (450mm) and the fan I am looking to fit is 429mm - so it should fit in within the existing shroud fairly easily.

[Jeron]

The shroud is unnecessary for the electric fan but keep it to route the hoses etc.

Make sure to measure the max depth.

If you have to go with a 16 or 14" fan you will be fine. The electric will pull a lot more air than the mechanical fan.

[bmwmech1]

I will respectfully disagree with Jeron's reply that the shroud is unnecessary... The fellows at Zionsville agree with me, as well, and they do BMW cooling better than anyone. If the shroud were not necessary, there would never be one installed on any car, viscous or electric fan setup. Yes, the electric will flow much more air, but why remove the shroud? It definitely helps with airflow and efficiency and BMW added it for a good reason. Not trying to start an opinion war here, just saying that there would be no good reason to remove the shroud, so why do it? Even if I decide to run a dual 12" setup, which I may, I will fab a new shroud... just no good reason not to...

On a separate note, the 17" or 18" single fan will work in the factory shroud... verified it today at my shop. The core is roughly 26" wide and 19" tall, so a dual 12" is possible, but nothing bigger for a dual, unless you staggered a pair of 14"s, but it makes fabbing a shroud more difficult.

BM1

[Jeron]

I did not suggest removing, there is no reason to.

The stock shroud is necessary for the viscous fan because it is so far from the core. Without the shroud the viscous fan would not pull air through the core.

The electric fan sits less than 1/2" from the core and has its own mini-shroud, so the stock shroud is unnecessary. You can make the electric fan more efficient by covering the entire back of the radiator. However if you do this with a small fan you will loose cooling capacity at speed.

[bmwmech1]

Originally Posted by Jeron

I did not suggest removing, there is no reason to.

The stock shroud is necessary for the viscous fan because it is so far from the core. Without the shroud the viscous fan would not pull air through the core.

The electric fan sits less than 1/2" from the core and has its own mini-shroud, so the stock shroud is unnecessary. You can make the electric fan more efficient by covering the entire back of the radiator. However if you do this with a small fan you will loose cooling capacity at speed.

Okay, last go of this and then I'll let the dead dog lay... Again, respectfully, I did not say you suggested removing it, I simply disagreed with your suggestion it was unnecessary in an electric fan conversion, which implies to remove it. You even said at the end of this last post that you can increase the efficiency of the electric fan by blocking off the entire back of the radiator, which is exactly what the OE shroud does and it even includes flaps to let air pass through the entire core at speed. So, again, I say that the OE shroud is necessary, functional and more efficient with either a viscous fan or electric, no matter how close to, or far away from the core the fan sits. The low pressure created by the shroud and it's proximity to the core will benefit any fan setup, no matter how close or far away it is to the core, because the shroud effectively seals the rear of the core off, except for the area that the fan occupies. This ensures the entire core is part of the cooling airflow, especially at lower vehicle speeds, thereby maximizing cooling and fan efficiency. Those crafty Germans then went a step further by putting flaps into the area not occupied by the fan which allows airflow to pass through the core in that area at higher vehicle speeds, via a ram air effect. So, I again respectfully disagree that the OE shroud is unnecessary and now I'll keep my big mouth shut...

BM1

[Silvercat]

Originally Posted by bmwmech1

I will respectfully disagree with Jeron's reply that the shroud is unnecessary... The fellows at Zionsville agree with me, as well, and they do BMW cooling better than anyone. If the shroud were not necessary, there would never be one installed on any car, viscous or electric fan setup. Yes, the electric will flow much more air, but why remove the shroud? It definitely helps with airflow and efficiency and BMW added it for a good reason. Not trying to start an opinion war here, just saying that there would be no good reason to remove the shroud, so why do it? Even if I decide to run a dual 12" setup, which I may, I will fab a new shroud... just no good reason not to...

On a separate note, the 17" or 18" single fan will work in the factory shroud... verified it today at my shop. The core is roughly 26" wide and 19" tall, so a dual 12" is possible, but nothing bigger for a dual, unless you staggered a pair of 14"s, but it makes fabbing a shroud more difficult.

BM1

Just for information, the fan I am looking to fit comes with an integral shroud and the whole unit fits to the face of the radiator - however I will keep the existing shroud for reasons Jeron already mentioned. The thickness of the unit is 2" so I guess there is plenty of room between the end of the water pump shaft and the radiator - but if anyone has the actual measurement????;

[bmwmech1]

Just measured it, it's 3.5" from the back of the core to the front of the waterpump threads. Plenty of room and you could offset it slightly away from the pump centerline to gain more space, if needs be...


BM1

[Silvercat]

Originally Posted by bmwmech1

Just measured it, it's 3.5" from the back of the core to the front of the waterpump threads. Plenty of room and you could offset it slightly away from the pump centerline to gain more space, if needs be...


BM1

And for that sir, I am exceedingly grateful!!!!!

[Jeron]

I havent seen the shroud on this car. If the fan does fill the entire open space of the shroud then yes it will certainly work and be beneficial.

The shrouds I have seen are about 3 inches deep and the electrics fans used are usually only a couple of inches thick at the sides. In addition, you usually cant fit a fan the same size as the shroud opening because the pump threads interfere with the electric fan motor. Typically you have to get a smaller 16" or 14" fan and offset it on the core.

It's these smaller offset fans that make the shroud meaningless.

Feel free to reply. I enjoy the discussion.