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Old 07-19-2012, 03:53 AM   #21 (permalink)
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thanks, but i think your wrong; high pressure exists under every road going vehicle. it's the pressure differential on top that creates lift(following bernoulli's principle: air flow over the immediate top of the vehicle increases in speed and decrease in pressure, wanting to return to it's original pressure and speed)(considering the vehicle is slicing through the air not the other way around, and it's not like air is piling up underneath the vehicle(nothing is stopping it from coming out from under the vehicle or compressing it), if anything the air is being slightly pulled out by the vehicles' vacuum wake); or how else would you explain lift at speed in general?

and fan blade, it's more like a turned over shovel.

ps. i didn't feel any discernible lift(short wheel base would make any lift felt especially at 100kph(over 60mph); it felt more stable.

if anything the air dam that is suggested would make the air pressure closer to equal(over vs under) along with the drag associated with parts in the air flow otherwise.
but i think there is a a vacuum induced behind both my skid plate and any air dam implemented, limiting the size/amount of vacuum would be best.

pss. sven do you have a problem with reading or comprehension?(do i need to draw pictures?)


Last edited by baldlobo; 07-19-2012 at 05:26 AM..
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Old 07-19-2012, 03:44 PM   #22 (permalink)
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The slope of the skid plate compresses air between itself and the ground. Opposite reactions, air pushes back up, pressing up on the car from underneath, creating lift.

There's a reason race cars have air dams and spoilers, the opposite of upward angled skid plates.
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Old 07-19-2012, 11:17 PM   #23 (permalink)
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ok so here's a picture

[_
.. \
... \

_____

you're saying it would compress the air(air as far as i know doesn't compress until your going well over 100mph; this is why ram air doesn't work)

then you're saying it'll over expand to fill the void increasing pressure(creating lift)

can you calculate gas expansion for what little it would be compressed for me(yes i'm asking you to do math)

oh and one more thing by the time my jeep cover's it's wheel base in distance it only needs to be going 10kph(jeep's wheel base is 93.4 inches(2.37 meters)

first of all direction isn't your strong suit is it, the skid faces downward not up... and most air dams i've ever seen are mostly straight down where as most spoilers are upward curves(designed to impliment downforce and drag).

if i felt any lift in the jeep it would make the rear end of the vehicle light, meaning it would feel unstable(it feels the complete opposite)

if you need better pics i'll break out paint next time.
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Old 07-19-2012, 11:51 PM   #24 (permalink)
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oh and why are you making a comparison with what looks like a 70's japanese race car to a truck; at least use truck racing cars
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Old 07-19-2012, 11:55 PM   #25 (permalink)
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Relax the people here are trying to help.

The lift they are describing is probably neglagible at best, but it does exist. One of the main reasons you are likely more stable is you have reduced the ammount of turbulance underneath. Highway stability is one of the reasons I am wanting to modify mine, expecially with cross winds. You might even notice a reduction in dust behind you on a dirt road.

The downward front skidplate wouldn't make the back lighter it would make the front lighter, but thats countered by the 650lb @300kg chunk of cast iron under the hood.
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Old 07-20-2012, 12:17 AM   #26 (permalink)
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thinking about putting a vacuum/boost gage through the floor(yay for floor drains)

i'm seeing vacuum due to the drop in intake temp.
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Old 07-20-2012, 12:31 AM   #27 (permalink)
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Quote:
Originally Posted by baldlobo View Post
i'm seeing vacuum due to the drop in intake temp.
I don't quite get what you mean.
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Old 07-20-2012, 12:52 AM   #28 (permalink)
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the engine bay is evacuated by speeding up, dropping engine intake temp.
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Old 07-22-2012, 02:41 PM   #29 (permalink)
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so just finished a weekend journey 250km(240km at 1/2 a tank 40 was city, 12l/100km), so the skid really only helps out with city driving.

wishing i could find a aisin r154 5th gear, that would help out with highway mpg.
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Old 07-24-2012, 06:27 PM   #30 (permalink)
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compress

Quote:
Originally Posted by baldlobo View Post
ok so here's a picture

[_
.. \
... \

_____

you're saying it would compress the air(air as far as i know doesn't compress until your going well over 100mph; this is why ram air doesn't work)

then you're saying it'll over expand to fill the void increasing pressure(creating lift)

can you calculate gas expansion for what little it would be compressed for me(yes i'm asking you to do math)

oh and one more thing by the time my jeep cover's it's wheel base in distance it only needs to be going 10kph(jeep's wheel base is 93.4 inches(2.37 meters)

first of all direction isn't your strong suit is it, the skid faces downward not up... and most air dams i've ever seen are mostly straight down where as most spoilers are upward curves(designed to impliment downforce and drag).

if i felt any lift in the jeep it would make the rear end of the vehicle light, meaning it would feel unstable(it feels the complete opposite)

if you need better pics i'll break out paint next time.
typically,compressibility effects are not encountered in automobiles until above 250 mph.
Pressure differentials will cause lift whether a function of velocity or separation/turbulence.

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