02GF74
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| posted on 10/4/06 at 02:41 PM |
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air filters open to rain
I've often wondered about this. I have seen K&N oval filters sticking past through the bonnet into the open air so what happens when it
rains? Obviously the filters must get soaked with rainwater so how does that affect the engine?
...... and thinking more about rain, how come when it is raining and we breathe the air, our noses don't get filled up with water? Is it
because out nostrils point down so as we suck air upwards, there is no enough suction to suck in the rain droplets?
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rusty
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| posted on 10/4/06 at 02:44 PM |
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I think even it we had our air filters pointing down driving them in to the rain at 60mph at full throttle they would still suck in rain.
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02GF74
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| posted on 10/4/06 at 02:49 PM |
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quote:
Originally posted by rusty
I think even it we had our air filters pointing down driving them in to the rain at 60mph at full throttle they would still suck in rain.
ok, but is the engine down on power due to their being more moisture in the mixture? or more power as it is a kind of water injection situation?
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Hellfire
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| posted on 10/4/06 at 02:53 PM |
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Have you noticed that your engine is more powerful in cold rather than hot weather... apparently it's to do with the nominal oxygen content at a
given temperature.
Personally I've no idea...
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nick205
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| posted on 10/4/06 at 02:56 PM |
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will you be driving a lot in the rain? 
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02GF74
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| posted on 10/4/06 at 03:04 PM |
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quote:
Originally posted by Hellfire
Have you noticed that your engine is more powerful in cold rather than hot weather... apparently it's to do with the nominal oxygen content at a
given temperature.
Is that because at lower temperature the air is denser so for a given volume there is more atoms of air and this means more oxygen; but then air
resistancce has to be greater.
quote:
Originally posted by nick205
will you be driving a lot in the rain?
No, but planning for Sod's Law; i.e it will rain for my SVA
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JoelP
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| posted on 10/4/06 at 03:05 PM |
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yes!
rain will get sucked in and there will probably be slightly less power due to more water hence less oxygen. I dont think you would notice though,
especially considering you have less grip in the wet anyway.
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ned
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| posted on 10/4/06 at 03:09 PM |
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isn't water injection used to raise compression ratio's? does rain work in the same way or are the amounts negliable I wonder?!
beware, I've got yellow skin
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JoelP
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| posted on 10/4/06 at 03:11 PM |
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i thought water jets as used on turbos were used to further cool the charge, to help prevent premeture ignition, hence more boost possible or
alternatively more compression.
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Marcus
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| posted on 10/4/06 at 03:22 PM |
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I can confirn that with the air filter sticking out of the bonnet, and heavy rain..... YOU STILL GET WET!! 
IN the South of France, we hit the most horrendous storm and the car started spluttering - more down to water in the electrics though!
Marcus
Marcus
Because kits are for girls!!
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DIY Si
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| posted on 10/4/06 at 03:59 PM |
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The filter will be splash proff, but no more than that. I know since mine sticks up outy of the mini's bonnet and gets soaked. The engine will
start to suck in water. If it's only a little wet, you'll slow down. If it gets really wet, you'll roll to a stop somewhere
inconvienient. If you're really lucky, all the electrics get wet too. 1 guess as to how I know all this.
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oliwb
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| posted on 10/4/06 at 04:01 PM |
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Funny thing - there is less dust in the air at dusk or during the night also which gives a hike in BHP.....you could really notice it working on the
farms at night in the tractor - they'd have a lot more go about them! Oli.
If your not living life on the edge you're taking up too much room!
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miserableoldgit
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| posted on 10/4/06 at 07:46 PM |
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In the rain
Most petrol engines will develope MORE power in wet conditions, something to do with water moisture increasing compression ratios. Been known in
motorcycling since 1930's to the extent that mist systems supplying water over the carb bell-mouths has been tried.
Not so sure about modern engines with injection and turbos, suspect effect will be less.
Youth and vitality are wasted on the young
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DIY Si
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| posted on 10/4/06 at 09:52 PM |
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Whilst this may be true, a soaked air filter won't let any air through. And what it does will be soo full of water it stops the sparks/flame
front from working properly. Or at least it does in my engine.
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SteveH
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| posted on 11/4/06 at 10:41 AM |
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I suspect that water drawn into the intake gets turned into steam when & if ignition takes place. Steam takes up a lot more room than water, think
it's about 1200 times the volume at atmospheric pressure...
It's the water content in methanol that helps to raise it's knock threshold...
I was reading an old article on Supercharging writen by an Ozzy, Eldred Norman & he recond he had put "A Gallon of water through a three
litre motor in seventy seconds at 5000 rpm without a trace of misfire"... but then I suspect he didn't try it with mixed driving with an
open air filter when it was pissing down...
I supose you could describe your motor as a hybrid...Petrol/Steam.....
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NS Dev
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| posted on 11/4/06 at 10:56 AM |
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Aha, well I happen to have quite a bit of experience on this one! Have a look at my avatar!
The filter on my grasser gets covered not only in water but mud and pretty much everything else too!
No problem at all, water just gets sucked in and vapourised through the engine, you'd need to suck in a huge amount to cause an issue.
Water injection is used in order to quell detonation. It has two properties, firstly it's high latent heat of evaporation cools the inlet charge
and reduces the potential for det. secondly it also has a property which nobody seems to understand whereby even at high charge temps the water
vapour/steam reduces the det risk, seemingly by breaking up the hot gas pockets in the combustion chamber that are the normal starting points for
pre-ignition.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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DIY Si
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| posted on 11/4/06 at 03:32 PM |
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In which case, any idea why mine splutters and stops in the heavy rain? My k&n sits out in the wind straight through the mini's bonnet.
Would take a pic, put the head's off at the mo.
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rusty nuts
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| posted on 11/4/06 at 05:43 PM |
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Ignition system getting wet ? Usual Mini problem
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MikeRJ
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| posted on 11/4/06 at 06:19 PM |
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I had K&N's on a bike years back and that would always start misfiring and eventualy die during a heavy downpour. Eventualy got shot of
them and replaced with stock airbox and no more problems. Actualy I lie, I had plenty of other problems with the bike, but cutting out in the wet was
no longer one of them...
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DIY Si
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| posted on 11/4/06 at 07:22 PM |
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Ignition sytem's all electronic. Never missed a beat at that end. Would love to fit something standard, but i'm running an ida on a custom
manifold. So can't fit/make an air box really as the filter sits entirely outside the car.
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