Bad Air Days.

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Zanx
19/09/2002 at 17:42
Anyone here notice that on some days the bark goes out of their bike yet on others, it's like the proverbial bat out of hell? Is this down to bad air or too much pasta?
satanspawn
19/09/2002 at 17:45
The KTM is like that some mornings mate....so i put it down to temperature, seems a bit wheezy sometimes.

When it gets really warmed up and on the ride home its fine again

Maybe its too much pasta only sensible answer i reckon

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mot
19/09/2002 at 17:45
it always makes me think the things about to go bang on me and cost money, but performace and noise does seem to change from time to time.

Would anyone care to do an impression of badly tapping tappets for me so I can either stop worrying or get the thing to a shop quick.
mot
Jkulin
19/09/2002 at 17:48
Some engine tuners have told me that it can be relative to atmospheric pressure or humidity, I don't know enough but can undestand on variable pressure days.

Can't really explain humidity unless its because the air is denser and therefore carrying more oxygen.
Now Motardless
badrider
19/09/2002 at 17:49
ssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhoooooowwwwwwwbllllllllllllllll drip drip drip a bad tap
never fear captain cartwheel's here
Hiney
19/09/2002 at 17:55
Its the same for us, we don't work well on thin air and nether do bikes (unless they've been set up to)

The thicker the air the bigger the bang!

Jkulin
19/09/2002 at 18:10
Hiney wrote

Its the same for us, we don't work well on thin air and nether do bikes (unless they've been set up to)

The thicker the air the bigger the bang!


I keep tellin me missus that...ooops wrong forum
Now Motardless
Papercup
19/09/2002 at 19:26
don't worry about the noises comign from your LC4 lump - they all sound like a food processor full of nuts and bolts


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jacka$$
19/09/2002 at 19:34
I've a guess it's alot to do w/ humidity, I should know, where I live it's between 80-100% nearly all summer!
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MZpog
19/09/2002 at 20:08
jk, humidity? nah, the only thing that affects your bikes performance is whether or not you took a dump before you set off.
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fastasulike
19/09/2002 at 22:12
Best performance on a cold dry day.

Worst, hot and humid.

All to do with relative air density.
demographic
19/09/2002 at 22:44
fastasulike wrote

Best performance on a cold dry day.

Worst, hot and humid.

All to do with relative air density.
Yep thats the one Hot air is less dense and humid air has less oxygen in it Cold air is denser and can't hold much water so if jetting is spot on for a hot humid day it will be lean on a winters morning. Also if it was setup spot on on a winters morn then it will be rich as feck on a humid hot day. Errrm we just done this in workshop in the dyno correction thread? and this is why I was looking for information on Relative air density the other day cos then once you get the jetting spot on then you find the RAD and write down the jets used and you can calculate jetting for different weather (or at least get it pretty close)
Funners
19/09/2002 at 23:05
Just to throw another spanner into this discussion...humidity HELPS atomization of fuel and you motor run better............Dont believe me...........well (Mike).the Chance-Vought Corsair a 2ww fighter plane had a water injection system that when activated would spray water into the chamber for as long as the water tank lasted (approx 10 mins) giving the plane an immediate performance jump of about 30 knots..........fairly impressive huh!
a humid evenig as the air ccols and densens up with a touch of humidity and your motor runs sweet!
A lot of performance cars run water injection to help things as well !
demographic
19/09/2002 at 23:35
WR-Fun wrote

Just to throw another spanner into this discussion...humidity HELPS atomization of fuel and you motor run better............Dont believe me...........well (Mike).the Chance-Vought Corsair a 2ww fighter plane had a water injection system that when activated would spray water into the chamber for as long as the water tank lasted (approx 10 mins) giving the plane an immediate performance jump of about 30 knots..........fairly impressive huh!
a humid evenig as the air ccols and densens up with a touch of humidity and your motor runs sweet!
A lot of performance cars run water injection to help things as well !
Bugger, Just when I thought I was getting my head around it as well Oh well this is the equations on how to work out relative air density anyway HERE
Jaffa Racer
20/09/2002 at 06:11
WR-Fun wrote

Just to throw another spanner into this discussion...humidity HELPS atomization of fuel and you motor run better............Dont believe me...........well (Mike).the Chance-Vought Corsair a 2ww fighter plane had a water injection system that when activated would spray water into the chamber for as long as the water tank lasted (approx 10 mins) giving the plane an immediate performance jump of about 30 knots..........fairly impressive huh!
a humid evenig as the air ccols and densens up with a touch of humidity and your motor runs sweet!
A lot of performance cars run water injection to help things as well !


there are a few cars around with water injection it boosts the compression IE steam takes up more space than water, so when the mixture ignites water turns to steam forcing the piston down the bore harder and faster than plane old fuel/air. hence the BHP boost.

then we move on to turbo's, compressors and intercoolers
Jaffa Racer
20/09/2002 at 06:14
oh not forgetting ram air induction and pressurised air boxes

got any maths for those
fastasulike
20/09/2002 at 06:25
Water injection and riding/drying/flying in humid conditions are not the same thing.

Water injection was done mainly to cool the air charge and increase density.

A humid evening will be better for engine performance than in the day, but it's still humid air and not so dense as dry cold air.
stoo
20/09/2002 at 10:19
WR-Fun wrote

Just to throw another spanner into this discussion...humidity HELPS atomization of fuel and you motor run better............Dont believe me...........well (Mike).the Chance-Vought Corsair a 2ww fighter plane had a water injection system that when activated would spray water into the chamber for as long as the water tank lasted (approx 10 mins) giving the plane an immediate performance jump of about 30 knots..........fairly impressive huh!
a humid evenig as the air ccols and densens up with a touch of humidity and your motor runs sweet!
A lot of performance cars run water injection to help things as well !


I think that one's gonna take a while to sink in... almost as bad as a fuel tank a mate of ours designed at uni. Think it was for Hydrogen, but the basic idea was you could fit many times as much fuel in the same sized tank if you filled the tank with this foam stuff first. Almost made me wish I paid more attention at school....
Funners
20/09/2002 at 15:37
fastasulike wrote

Water injection and riding/drying/flying in humid conditions are not the same thing.

Water injection was done mainly to cool the air charge and increase density.

A humid evening will be better for engine performance than in the day, but it's still humid air and not so dense as dry cold air.


He He He He He keep it coming mate
demographic
20/09/2002 at 15:45
Jaffa Racer wrote

oh not forgetting ram air induction and pressurised air boxes

got any maths for those
I could find some and if I had a sportbike I might even give a shite then but as all this air density stuff does affect jetting (more so on two smokes, ie my bike) so I thought I would try and get my head around it. You might notice I don't go on about cams and valves much? Thats cos they don't affect me much
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