How to: Change OEM 3b fan to Pacet PF1311P

[Mr.Crossfire]

Yes, with the OE-fan. But the Pacet one has a cowl in itself, preventing the fan sucking air from anywhere else but through the radiator.

[SteveH]

Old thread, but I'm about to purchase a replacement fan. What's the score with the three fan speeds available with the standard fan when you move to one of these two wire versions? Do you just loose the high speed fan feed and just work on the fan power supply that activates at 90 degrees or do you connect the 2nd and 3rd fan speed inputs to the new fan wires to get both mid speed + feed and high speed + feed?

I've looked at a few fans, most are 80w, but I have also spotted a 120w high flow version, does anyone know what the standard fuse and wiring will support?

Cheers,
Steve

[AndyP]

Can't help on the 120w version but I just wired mine directly into the std 3B fan plug. You do only have one speed, but it copes fine. Thinking about it, it does run slower when the after-run pump is on, not sure how that controls the speed?

[Error404]

anyone know how these slimline fans compare to the ABY unit in terms of efficiency?

[SteveH]

Can't help on the 120w version but I just wired mine directly into the std 3B fan plug. You do only have one speed, but it copes fine. Thinking about it, it does run slower when the after-run pump is on, not sure how that controls the speed?

Thanks Andy. I guess if the 120w version puls too much current I'll have to increase the fuse rating or use the existing feed via a relay and new feed from the battery.

[re2500]

...about 20-30% increased efficiency by having the cowl in place apparently, hence the desire to retain it..

I can imagine you would have the 20-30% extra efficiency if the fan was in the opening of the old cowling, but the way you have fitted the fan means that the fan is only sucking hot air through the rad in the circle beneath the fan, whether the cowling is there or not.
If the fan was in the opening it would suck through the whole rad, would it not?

Although on the other hand the air being blown through the hole by the fan may cause a little suction within the cowling and encourage air flow through other areas of the rad?

TBH, im sure what you have done works great, and will be far better than the standard setup, but im just trying to work out if you're gaining anything from the cowling? correct me if im wrong!

[Zeus]

I can imagine you would have the 20-30% extra efficiency if the fan was in the opening of the old cowling, but the way you have fitted the fan means that the fan is only sucking hot air through the rad in the circle beneath the fan, whether the cowling is there or not.
If the fan was in the opening it would suck through the whole rad, would it not?

Although on the other hand the air being blown through the hole by the fan may cause a little suction within the cowling and encourage air flow through other areas of the rad?

TBH, im sure what you have done works great, and will be far better than the standard setup, but im just trying to work out if you're gaining anything from the cowling? correct me if im wrong!

The way the fan is mounted in these pictures, the cowl is probably only decreasing efficiency by a few %, it's creating extra resistance when driving at high speed, so the fan will cut in faster because of the cowl. Also, the fan doesn't seem to be placed directly in front of the opening in the cowling, also creating extra resistance... it would be better if the fan was able to blow it's air away freely when mounted this way.

Also, placing the fan in the stock position would increase cooling efficiency in 2 ways:
1. You will be sucking air through the entire radiator surface, which means air resistance through the radiator will be lower as compared to just sucking the air through the circular surface of the fan. This means you will suck more m^3/hr through the radiator.
2. The speed of the air passing through the radiator will be lower, so it will be in contact with the radiator longer, and thus heat up more. So the fan will effectively blowing more air, and hotter air, reducing the time that the fan needs to run in order to cool the coolant. (so the fan will run less often and for a shorter period of time)

Also, because of the reduced air resistance (and thus reduced pressure loss) the fan will probably be using less power (and pull less Amps).

[s2driveruk]

hmmm....i need science lessons

In all honesty, having had this on the car for a while now....some quick observations:

1) - its quiet
2) - I have no idea whether the cowl makes an difference at all, I will see if i can remove it and run without for a while a note the differences if any
3) - In the VERY hottest weather and longest total driving distance i have done on a single day in the car and in almost stationary traffic for well over an hour, it did actually start to struggle to contain the temperature but that was with the a/c running and after a 450mile drive in 25-28degree heat. Didn't bat an eyelid at the Ring even after 3 consecutive laps...
4) - I'd researched what fans would fit and this was pretty much the biggest sucking version I could find, the stats are somewhere on the Forum for air moved/min
5) - The fan could not be centred on the ABY cowl due to the OEM offset position, I got as close as I could to it
6) - I had mine wired to stage one fan from memory, kicks in an out as expected and its also manually working off the a/c button in the cabin (even though the a/c is no longer fitted to the car)

Hope that helps

[Zeus]

hmmm....i need science lessons

In all honesty, having had this on the car for a while now....some quick observations:

1) - its quiet
2) - I have no idea whether the cowl makes an difference at all, I will see if i can remove it and run without for a while a note the differences if any
3) - In the VERY hottest weather and longest total driving distance i have done on a single day in the car and in almost stationary traffic for well over an hour, it did actually start to struggle to contain the temperature but that was with the a/c running and after a 450mile drive in 25-28degree heat. Didn't bat an eyelid at the Ring even after 3 consecutive laps...
4) - I'd researched what fans would fit and this was pretty much the biggest sucking version I could find, the stats are somewhere on the Forum for air moved/min
5) - The fan could not be centred on the ABY cowl due to the OEM offset position, I got as close as I could to it
6) - I had mine wired to stage one fan from memory, kicks in an out as expected and its also manually working off the a/c button in the cabin (even though the a/c is no longer fitted to the car)

Hope that helps

Sorry if it seems like critique, but my post was only meant to suggest some improvements for people who might try and do this conversion in the future. I'm not saying your solution is insufficient or bad, but there is some room for improvement if you're keeping the cowl in place anyway.

Removing the cowl might stop the car from overheating in the hot traffic you're describing, but the difference won't be that much, so I doubt it will be enough to solve that problem.

Best solution would probably be to use some fiberglass or something to glue the fan against the cowl in its stock position so it will suck air through the entire radiator, making sure it's nice and flush against the edge of the cowl so there isn't any gap between cowl and fan (if it doesn't fit precisely: close the gap with some fiberglass or some material as the air will always search the path of least resistance).

As for point 4, the fan that moves the largest air volume isn't always the best, you need to look at how much air it moves at a certain pressure difference (as there will be a certain pressure drop over the radiator as air moves through it at a certain speed, the higher the speed, the more pressure drop you will have. A fan can suck a million m^3/hr at 0 Pa pressure difference and 0m^3/hr at 1 Pa pressure difference rendering it completely useless for this kind of application.)

And again, I'm not saying the fan you have is bad, it's probably fine (after all, it was designed to suck air through a radiator )
Also I don't know the resistance of the radiator, but if you have those figures, you can calculate which fan will suck the most air through the radiator, but that isn't necessarily the one with the most m^3/min. (However, it probably is if each fan creates about the same max. pressure difference at 0m^3/min flow )

Hope that clears things up a bit more

[s2driveruk]

hey no worries i wasn't taking it as a dig, just trying to add an update....it is what it is, as i say in 99.9% of cases its been absolutely fine and worth the change