Radiator Fan

[Ivan Hernandez]

I just wanted to ask a quick question?, and please give feed back asap. We are working on a one cylinder engine and i want to know if its necessary to put a fan on the radiator since its a one cylinder.

[NickFavazzo]

What will happen when the engine is running but the car is not moving? ie little or no airflow over the radiator.

[Mbirt]

As a counterpoint, do dirt bikes have cooling fans? It's an engineering decision you and your team will have to make. Will your starting system be robust enough to restart several times while in line for an event if it begins to overheat without a fan? Will your charging system be up to snuff for handling fan in addition to a fuel pump, ECU, and data logger? These are all things that need reconsidered when lightweighting an FSAE car.

[Rex Chan]

we (Melbourne Uni) run a 4 cylinder, with a radiator.

The number of cylinders/size of engine shouldn't matter to whether you run a fan or not. One of the aims of your cooling system should be to bring the engine up to temp as quickly as possible, then hold that temp.

The amount of heat transferred to the cooling system will vary as you drive around, so the cooling system needs top be able to buffer + dissipate that energy. Relative to no fan, the radiator will have to be bigger in order to achieve that. That said, RMIT did not run a fan on their singles.

Our 2010 data shows that it takes about 1/3 to 1/2 of the 1st drivers run of enduro to get the water up to temp ~85C. After that, the fan is switching on/off to keep temps within 90-92C. This year (2011), we have reduced the size of the radiator, so should heat up faster, but will need to use more fan to keep things cool. The 2011 car will be running soon, in spring/summer heat, so we'll let you know how that goes.

[Spetsnazos]

Depends on how you want to do it. Ideally, I would do it like the radiator/cooling guy did it last year where he analyzed it as a compact heat exchanger and calculated how much heat is dissipated.

The kind/size of radiator you choose will impact your decision...A blanket statement like "single cylinders don't need fans" would be pretty bad IMHO.

[Spetsnazos]

Originally posted by Mbirt:
As a counterpoint, do dirt bikes have cooling fans?

They also don't have the engine behind the car/driver...

[Ben K]

Originally posted by Ivan Hernandez:
I just wanted to ask a quick question?, and please give feed back asap. We are working on a one cylinder engine and i want to know if its necessary to put a fan on the radiator since its a one cylinder.

*facepalm*

First of all--we do not have to answer you ASAP--this is a forum for discussion of new ideas and general help....but it is clear that you didn't do any research.

Either way, having a one cylinder does not preclude the idea of a pro-con list of what happens when you don't have a fan. Our team didn't run a fan on our one cylinder when it was cold outside and we were moving constantly--but with no movement, the engine would overheat after 3-4 minutes. Pro -- Less weight. Con -- It might overheat.

Better safe than sorry--unless you really are looking to save the couple of pounds. I'd run some experiments once you have a running car.....

Ben

[Dart]

To begin with f1 cars have no fans, but the speeds at which they run and superb ducting makes it possible to do without it. for fsae cars the speed is relatively very less. so according to me not having a fan can be troublesome. You can also have more responsive system by switching the fan on or off according to the temperature.

[Whitney Hurlbut]

I've noticed there are very few rules surrounding this topic. Would it be possible to have a fan with the pit crew in the pit lane, as that would be one of the few times when the car is idling?

[Rex Chan]

No rules, probably cos there's no safety aspect to it. In driver change, only 2 drivers and 1 extra person is allowed in the area. And no fans.

I do not think it a wise choice to design your car so that it REQUIRES an external fan to operate.

Just use a fan - is it really worth the weight/power saving? I like having a fan as a backup in case something goes wrong with the cooling (such as your calcs were wrong).

By pit crew, you mean the disorganised bunch of ugrad students playing at building a racing car? I would think 90% of teams would not be organised to rememeber to build/test/charge/bring/use a fan

[jlangholzj]

Originally posted by Dart:
To begin with f1 cars have no fans, but the speeds at which they run and superb ducting makes it possible to do without it. for fsae cars the speed is relatively very less. so according to me not having a fan can be troublesome. You can also have more responsive system by switching the fan on or off according to the temperature.

yes/no. I finally got a decent cooling package on our car this last year. I analysed the system using the epsilon-NTU method and with the fans we were able to run on the car, being able to meet the "1/3 rule" for heat rejected, we were flowing about 1400 cfm total. (~700 per side). That gave us enough cooling while driving to keep it within operating temp. We didn't have any ducting/diffusers so pretty much any air pulled through was due to the fans. Similarly, that same setup with some ducts would flow about ~twice as much at 40mph. This is obviously the case of over-sizing our radiators *if we properly ducted them* truthfully if i would have had a diffuser/duct on the front i could have probably only used one of the two radiators.

its not a speed issue, its a reliability issue http://fsae.com/groupee_common/emoticons/icon_cool.gif

[Racer-X]

On the topic of running a fan. Bikes do not have them, but bikes also don't have the motor and radiator stuffed in bodywork that may or may not hinder flow. Even then my crf450x that I trail ride doesn't like sitting for more than 5 minutes once it's warmed up. Chances are you will run into a situation where you need the fan to pull air through the radiator.

As far as "can you have a blower for when the car is stopped?". You could but chances are it will be banned the next year...

The car would risk overheating anytime it stops and you are not right by it to cool it down. So that leaves you with running around with a backpack leaf blower or shutting off the engine and needing to restart all the time, all while letting the motor heat soak. Then there is also the possibility of a slow endurance course, on hot day, with too small of a cooling system...

[jlangholzj]

Originally posted by Racer-X:
On the topic of running a fan. Bikes do not have them, but bikes also don't have the motor and radiator stuffed in bodywork that may or may not hinder flow. Even then my crf450x that I trail ride doesn't like sitting for more than 5 minutes once it's warmed up. Chances are you will run into a situation where you need the fan to pull air through the radiator.

As far as "can you have a blower for when the car is stopped?". You could but chances are it will be banned the next year...

The car would risk overheating anytime it stops and you are not right by it to cool it down. So that leaves you with running around with a backpack leaf blower or shutting off the engine and needing to restart all the time, all while letting the motor heat soak. Then there is also the possibility of a slow endurance course, on hot day, with too small of a cooling system...

the last time i looked the R6 has a couple fans on its radiator....really they don't need to flow that much at idle. Can't vouch for the f4i but I'm sure they're no different.

[Racer-X]

Originally posted by jlangholzj:

the last time i looked the R6 has a couple fans on its radiator....really they don't need to flow that much at idle. Can't vouch for the f4i but I'm sure they're no different.

I was talking about singles like the OP was asking about. Yes most modern 4 cylinder street bikes have cooling fans.