Carbs air cooling with fan ... Is it a crazy idea?

[Cadorna]

Hi,

Well, I'm cleaning and fixing my rubbers bell mouth on my H1, I have to make some modifications to do it in the following days .... Paralelly, I'm cleaning my PC from dust and in this moment, I have an idea when I saw the 12 cms fan inside it, what could be happend if I installed 2 of this fans into the air box pushing air to the carbs mouth ? Improve on something? I mean, mechanically, any advantage would send jets of air to the carburetors? There are no problems for space because both fit without problems, and being behind the air filter would drag dust ... even could regulate the speed of making same increase or decrease the air flow according to engine revolution ... I don't know ... What do you think about it? I know, it is not a real RAM AIR, but do not work the same way?

Take a look at the pics please.

http://dl.dropbox.com/u/2247024/192.168.1.106.jpg
http://dl.dropbox.com/u/2247024/192.168.1.106_2.jpg
http://dl.dropbox.com/u/2247024/192.168.1.106_3.jpg
http://dl.dropbox.com/u/2247024/192.168.1.106_4.jpg
http://dl.dropbox.com/u/2247024/192.168.1.106_5.jpg

[CaNsA]

what could be happend if I installed 2 of this fans into the air box

you will restrict the airflow subsequently less air will get into the carbs.

[gavinfdavies]

in theory, it would pump some air into air box. but consider this...
400cc engine = 0.4 litres per revolution. being a 4 stroke, only every other stroke is sucktion, so you're looking at 0.2l per revolution. At 14,000 rpm you'll be looking at a wopping 2,800 litres per minute of air flow. now assuming that an engine is only 80% efficient then you'll still be looking at a peak flow along the lines of 2,240l per minute.

now, pc fans. the biggest/fastest commonly about is the 120mm fan a sythe slip stream 1900 pumping 110 cfm (cubic foot per minute) which is about 3000l per minute. now whilst this may actually be more air than the zxr sucks in, the next thing to consider is static pressure. with things like fans, as the pressure rises, the flow drops, since alot of the air is forced back passed the fan by the pressure. After all, if you attached the fan to a sealed box, the box wouldn't blow up, the air flow through the fan would drop rapidly. now, a similar fan at 64CFM can hold a static pressure (the pressure inside said sealed box) of 1.3 mm of water, which in modern units is.... 0.13mBar, where 1mBar is a 1000th of atmospheric pressure. so lets be generous and say our high flow fan can hold a static pressure of 0.2mBar at 2,240l per minute (ie it was keeping up with engine demand). If you recall, turbo boost is measured in bar. if you boost pressue by 1bar, you're giving the engine another atmosphere's worth of air, ie you double the air flow, and will in theory double the power.
So a fan producing 0.2mBar (0.0002Bar) will improve an engines peak power by.... 0.02%! roughly 0.002bhp!
Of lets put it another way - you'd need 5000 fans to produce 1 bar of boost and thus double the power.

so on paper the flow rates might look good, but it's the pressure that's important.

if you've got some fans to spare, they'd probably be more use attached behind the oil cooler and linked in to the radiator fan to keep the engine cool on hot days.

[CaNsA]

gavinfdavies - Using the shovel of logic to slap people in the face

[RedexRobB]

Goog idea, but theres also the fact that installing fans on top of the bellmouths will interupt the flow, they are shaped for a reason.

Also, fans do not produce a constant air flow, because of each blade they produce pulses of air, which is why wind tunnels suck air through and not blow.

I think also the amount of air required will vary with engine speed, so the fans will need to vary with it.

If it worked i dare say id would have been thought of.

[gavinfdavies]

i didn't mean to slap...

it has been done before - you can buy big electrical tubines, they cost a lot, require a dirct link to the generator, and only produce about 1psi boost and you can only use them intermitently because they over heat. This being because a good supercharger needs about 50bhp to run, but creates about 150 extra (in typical car) so a 1000w electric fan (1.3bhp) isn't going to do much!

[Cadorna]

Thank you very much for the explanation, I learn a lot about it.

Surfing the web, searching for another thing, I found this:

http://www.pedparts.co.uk/koso-turbine- ... 5073-p.asp

I didn't know it ...