Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 1:05 pm  

Ferocious Aardvark wrote:

:BOW:

However, I'm not sure it's right. My even more scientific calculation is that usually, after it's been raining, the air can be incredibly fresh and satisfing, which I'd always sort of put down to all the invigorated plants including grass and trees going to town with their photosynthesis, and ramping up oxygen output; making oxygen while the rain shines, sort of thing.

I know that in good rainy conditions most plants can go absolutely berserk, just like they can close down in a drought.

So to me, any calculation needs to start with this: despite the fact that the AVERAGE oxygen content of all air may well be 21%, what is the actual local oxygen percentage in a prolonged spell of good rainy growing weather? I'd bet it would be above average.

All of which is instantly nullified when you're stuck in a five mile queue on Kirkstall Road at 8.30am and your car is breathing in the fumes from the car in front

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 1:17 pm  

Right, so according to this thread I need to avoid driving in the rain. Given I live in (north) Manchester that's gonna be a toughy. And if I can't avoid driving in the rain I need a set of appropriate tyres. So I'll be changing tyres every other day. And if I feel faint after changing tyres for the third time during my journey thanks to another sudden downpour I just need to take some deep breaths near a tree?

That's sorted then.

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 1:18 pm  

McLaren_Field wrote:

All of which is instantly nullified when you're stuck in a five mile queue on Kirkstall Road at 8.30am and your car is breathing in the fumes from the car in front

But not really, if the base local oxygen percentage is higher than average, don't see why, however much the cars in the vicinity may dilute or reduce it, it still wouldn't be higher compared to the same queue on a dry day?

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 2:07 pm  

Scooter Nik wrote:

Wet weather actually helps 2-stroke engines. They run slightly leaner in it, meaning lower fuel consumption with a greater bang, meaning better power output. It's not a huge difference, but you're aware of it.



Oh, and what's a traffic jam?

All benefits cancelled out in my experience by the effect of rain on six volt electrics.

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 2:28 pm  

Ferocious Aardvark wrote:

:BOW:

However, I'm not sure it's right. My even more scientific calculation is that usually, after it's been raining, the air can be incredibly fresh and satisfing, which I'd always sort of put down to all the invigorated plants including grass and trees going to town with their photosynthesis, and ramping up oxygen output; making oxygen while the rain shines, sort of thing.

I know that in good rainy conditions most plants can go absolutely berserk, just like they can close down in a drought.

So to me, any calculation needs to start with this: despite the fact that the AVERAGE oxygen content of all air may well be 21%, what is the actual local oxygen percentage in a prolonged spell of good rainy growing weather? I'd bet it would be above average.

Don't forget we are talking about driving in the rain here.
Not after the rain.
During rain the light intensity is lower than on a bright sunny day, so photosynthesis at the time would probably be nothing out of the ordinary.

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 2:37 pm  

Stand-Offish wrote:

Don't forget we are talking about driving in the rain here.
Not after the rain.
During rain the light intensity is lower than on a bright sunny day, so photosynthesis at the time would probably be less, irrespective of the water in the ground.

Hence my reference to good growing weather. I appreciate that the effect isn't instant.

Also a factor not mentioned is that driving through rain even discounting the tyre drag means you are having to use extra energy to (a) penetrate a "wall" of water and (b) carrying about the weight of the water on your car at any given moment.

But I think we've established that the answer is less than straightforward!

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 3:00 pm  

Ferocious Aardvark wrote:

Hence my reference to good growing weather. I appreciate that the effect isn't instant.

Also a factor not mentioned is that driving through rain even discounting the tyre drag means you are having to use extra energy to (a) penetrate a "wall" of water and (b) carrying about the weight of the water on your car at any given moment.

But I think we've established that the answer is less than straightforward!

Yes indeed I appreciate there are many factors.
I only wanted to address the dry air /moist air factor irrespective of the local oxygen content variations.
I hope I did that.
Cheers.

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 3:25 pm  

Keith wrote:

All benefits cancelled out in my experience by the effect of rain on six volt electrics.

Thank god all mine carry 12v DC then, eh?

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 3:37 pm  

Stand-Offish wrote:

Yes indeed I appreciate there are many factors.
I only wanted to address the dry air /moist air factor irrespective of the local oxygen content variations.
I hope I did that.
Cheers.

If I could understand a word of it, you very likely did

Re: The effect of rain on fuel consumption : Tue Mar 06, 2012 5:03 pm  

Stand-Offish wrote:

Yes indeed I appreciate there are many factors.
I only wanted to address the dry air /moist air factor irrespective of the local oxygen content variations.
I hope I did that.
Cheers.

Apparently I was wrong to assume it was the oxygen content in moist air that was the contributing factor to improved fuel economy. It would appear that it is the density of the air that makes the difference, moist air being less dense than dry air