Hello,
I am currently running a 12v 80w rad fan. I am wanting to increase my cooling performance. I have added a large shroud and ducting, so now looking at fan options.
I have a concern that if I increase fan power I may have issues with power supply due to the output of the bike engined power regen system.
Anyway, would love some comments and experience.

Currently running a 08 Yamaha R1.

Was thinking something like this

https://daviescraig.com.au/product/brushless-12-high-power-thermatic-electric-fan-12v-0127?srsltid=AfmBOoqYibomBPF-b_pyyY1SGDAmo-Fegsnm1GASeQt36DY0EDn PSDT-

Correct me if I'm wrong, but no radiator fan can compete with a well designed airflow from a moving car. You say you've added a shroud and ducting, are you sure you've actually improved air flow?

I remember reading an article at some point that suggests trying to force air into a radiator does not work if the pressure behind the radiator isn't dealt with. If the back side of the radiator just empties into an enclosed engine bay then you won't get the through flow.

For me a fan should only be required to keep engine temps reasonable when sat in traffic, other than that it's just a parasitic drain.

Sorry I should of added more info. It's mid engine with rad at the back. I have ducting to get airflow to read and have a shroud to make the fan flow more efficient

I'd agree with slimy if you dont get the airflow away from the back of the radiator it will stall and it will not matter one jot how hard the fan blows, you need to get the warm air away from the back of the rad.

Have you thought about the idea that has been used on the Dax Rush? Ventilation out though the sideplates in the engine bay?
I’m facing the same problem, Yamaha 5VY engine, and not much Watt to use for radiator fan.
Finding the fan with most cfm flow at the lowest amp draw isn’t easy.

I'd be very interested to see some photos of the setup.

As others have said it's more about the ducting front and (more importantly) to the rear of the rad.

Ducting around the fan would make it more efficient, with the fan a minimum of 1.5 blade widths away from the face of the rad.

quote:

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Originally posted by pigeondave
I'd be very interested to see some photos of the setup.

As others have said it's more about the ducting front and (more importantly) to the rear of the rad.

Ducting around the fan would make it more efficient, with the fan a minimum of 1.5 blade widths away from the face of the rad.

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Looking at your pics exit flow isn't your issue. It's more likely to be warm/hot air entering from the engine. You need cold air ducting to the front of the radiator.

The bike ecu switches the fan at 105c so don't panic at 100c. My front engined r1 Fury though would be around 70 at steady 7k rpm and run at 90-100c at full chat on track. Fan only gets used stationary or in traffic and only if ambiant temps are >35c does it struggle to pull temp down.

[Edited on 8/3/25 by adithorp]

[Edited on 8/3/25 by adithorp]

It may be worthwhile attempting to see what the airflow is like on the more. The old idea of bits of wool thread stuck in places is simple but effective. Would need somebody following to watch/film, or a gopro type camera set up.
You may find the air is moving in an unexpected direction.

Super Mini ford 3100 v6


This is a old race car of mine what you need is a funnel box feeding air into the rad and it looks like you could fit a bigger rad too
G

Are you sure the fan is not acting like a bit of a block to the air flow coming out?
I think modern fan shrouds have got rubber flaps which allow the air to blow through but when the fan fires up it draws through the rad.

This video has some good rules of thumb and it's got sources of these rules
https://youtu.be/doP04J05QdQ?si=WDhGJBLOK4CJYZn_