1. It's hotter than cousin-love right now, like 95+. Also the humidity is way up there, probably greater than 85%, even in the hottest part of the day. At night, when the temp gets below 85 or so, moisture is condensing out of the air and forming fog. So obviously there's a lot of water grains / cubic foot, which mean less O2 per cubic foot of air, correct? Is this O2 displacement significant enough to be noticed by the XX engine? My engine seems to be just a little off when the humidity is really high, or maybe I'm just really high....
2. I read recently (per Philip and Forrest) that the XX engine should hit 10K rpms at least once per day of riding. I know the XX engine can handle 10K rpms all day long. But I rarely rev my engine that much, should I? At least every so often? Does it actually help somehow?
Full Version: A couple of engine questions
Mine's a bit sluggish on the HHH days too.
Funny you mention the 10k thing. I haven't let it rip in a few weeks and let her loose for a bit this afternoon. I need to do it more often
Funny you mention the 10k thing. I haven't let it rip in a few weeks and let her loose for a bit this afternoon. I need to do it more often
Basically, in NA ( normally aspirated ) engine high humidity in high temps kills power,unless motor had some problems like carbon build up,too high CR,or fuel was marginal ( octanes)
In 100 Far.deg and 100% humidity water would make 6.5% of air,so power would drop 6.5% due to lower O2 content vs "dry" 100 F deg,like in the desert. Engine pressure sensor can`t distinguish between pressure exerted by water vapour and "normal" air,motor will run 6.5 % richer .Most likely another source of power and fuel economy drop.
100 F and 100% humidity, perhaps it is too extreme example,but in 90 F deg and 90 % humidity saturation pressure of water would be about 4 %,would still kill power.
If you have power commander you could safely lean out the mixture for high temp/humidity days using bottons on the module without touching base map.
BTW,today it`s been hot and humid like hell here in Chicago,,,,
In 100 Far.deg and 100% humidity water would make 6.5% of air,so power would drop 6.5% due to lower O2 content vs "dry" 100 F deg,like in the desert. Engine pressure sensor can`t distinguish between pressure exerted by water vapour and "normal" air,motor will run 6.5 % richer .Most likely another source of power and fuel economy drop.
100 F and 100% humidity, perhaps it is too extreme example,but in 90 F deg and 90 % humidity saturation pressure of water would be about 4 %,would still kill power.
If you have power commander you could safely lean out the mixture for high temp/humidity days using bottons on the module without touching base map.
BTW,today it`s been hot and humid like hell here in Chicago,,,,
"Life Begins at 7000RPM..."
QUOTE(tomek @ Aug 7 2007, 08:57 PM) 
Basically, in NA ( normally aspirated ) engine high humidity in high temps kills power,unless motor had some problems like carbon build up,too high CR,or fuel was marginal ( octanes)
In 100 Far.deg and 100% humidity water would make 6.5% of air,so power would drop 6.5% due to lower O2 content vs "dry" 100 F deg,like in the desert. Engine pressure sensor can`t distinguish between pressure exerted by water vapour and "normal" air,motor will run 6.5 % richer .Most likely another source of power and fuel economy drop.
100 F and 100% humidity, perhaps it is too extreme example,but in 90 F deg and 90 % humidity saturation pressure of water would be about 4 %,would still kill power.
If you have power commander you could safely lean out the mixture for high temp/humidity days using bottons on the module without touching base map.
BTW,today it`s been hot and humid like hell here in Chicago,,,,
In 100 Far.deg and 100% humidity water would make 6.5% of air,so power would drop 6.5% due to lower O2 content vs "dry" 100 F deg,like in the desert. Engine pressure sensor can`t distinguish between pressure exerted by water vapour and "normal" air,motor will run 6.5 % richer .Most likely another source of power and fuel economy drop.
100 F and 100% humidity, perhaps it is too extreme example,but in 90 F deg and 90 % humidity saturation pressure of water would be about 4 %,would still kill power.
If you have power commander you could safely lean out the mixture for high temp/humidity days using bottons on the module without touching base map.
BTW,today it`s been hot and humid like hell here in Chicago,,,,
That's interesting and I know this is hugely important on high performance 2-smoke GP style bikes (or 2-S dirt bikes) but I did not think it would effect 4 strokes that much (unless heavly machines for high perf). Normally when severe heat occurs the humidity, while still pretty high runs inversely proportional to heat (i.e. @78* youre @~83%, @99* youre @~44%....roughly but the Dew Point stays about the same 72*ish ) so I would agree there may be another source for the drop but you make an excellent point.
This is what the PGA boys are playing in here in Tulsa. If you're a golf fan we'll see who's fit on the tour this week!
Temp vs Humidity Wednesday Aug 8th graph Tulsa.
http://www.srh.noaa.gov/forecast/MapClick....amp;AheadHour=0
Temp vs Humidity Wednesday Aug 8th graph Chicago. Dew point at 68ish.
http://forecast.weather.gov/MapClick.php?w...56&site=lot
Maybe Bowen will get in on this I know he regularly hits the rev limitter, on ANY BIKE THAT IS LEFT WITH KEYS. 
I'm a firm believer that running any engine up to its redline on a regular basis is a good idea. Aside from the obvious emotional benefits to the operator, it helps keep carbon and other crud from building up in the engine. I have 27K on my '99 Bird and the intake ports and valves still look almost new. My theory is that the detergents in gasoline and oil work a lot better with more velocity. Kinda like a pressure washer.
What the fuck is a water grain?????
QUOTE(Dion @ Aug 9 2007, 01:37 PM)
What the fuck is a water grain?????
Kind of like that mist you get in your face when you pee into the wind.
QUOTE(Dion @ Aug 9 2007, 01:37 PM)
What the fuck is a water grain?????
The number of water grains in a unit of air (pounds or cubic feet) quantifies the absolute humidity instead of the relative humidity, which varies by temprature. If you want to remove temperature as a variable then express the amount of moisture in the air as the number of water grains in a unit of air
1 pound of water= 7,000 grains
Here's an article discussing how it relates to engine tuning. RaceCarBook.com. Water grains are discussed about halfway down the page.
QUOTE(MrBadExxample @ Aug 9 2007, 05:12 PM)
QUOTE(Dion @ Aug 9 2007, 01:37 PM)
What the fuck is a water grain?????
The number of water grains in a unit of air (pounds or cubic feet) quantifies the absolute humidity instead of the relative humidity, which varies by temprature. If you want to remove temperature as a variable then express the amount of moisture in the air as the number of water grains in a unit of air
1 pound of water= 7,000 grains
Here's an article discussing how it relates to engine tuning. RaceCarBook.com. Water grains are discussed about halfway down the page.
I like my answer better
QUOTE(Northman @ Aug 9 2007, 05:56 PM)
I like my answer better
Oh your answer was, I was in a more serious mode when I posted, like all gettin' my science on.
QUOTE(MrBadExxample @ Aug 9 2007, 08:29 PM)
I was in a more serious mode when I posted, like all gettin' my science on.
Booze will help you with that
I like Chris' answer best
BUT!, properly stated scientificly would be
BUT!, properly stated scientificly would be
QUOTE
So obviously there's a lot of grains of water / cubic foot, which mean less O2 per cubic foot of air, correct?
water grains and sluggish feeling?
Shut the hell up and just down shift you damn fruit loop..
Shut the hell up and just down shift you damn fruit loop..
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