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Old 01-16-2019, 09:26 PM   #1 (permalink)
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Benefits of undertray lip?

Hello, I have a doubt!

I watch several cars, how suvs with a undertray lip, behind the front fender.
And also Cámaro zl1 1LE has one.





Does it have the same properties as a normal front lip of the fender? Despite being behind?
I think that it will increase the lift, but Cámaro zl1 has one....

Sorry for my English!

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Old 01-16-2019, 10:43 PM   #2 (permalink)
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I can't be sure what you're pointing to.

With the Camaro it's not clear whether the [lower element/feature in question] is vertical or horizontal.

With the HR-V it appears to have a vertical air dam with a central notch, followed by two wheel spats.

A biplane splitter is a race car thing, air dams and spats are eco-things.
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Old 01-17-2019, 08:30 AM   #3 (permalink)
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Old 01-17-2019, 03:45 PM   #4 (permalink)
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Old 01-17-2019, 06:16 PM   #5 (permalink)
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Does this graphic image help clarify your terminology?

S2000 Aerodynamics
https://robrobinette.com/S2000Aerodynamics.htm

Quote:
Note how the high pressure (red) bubble sits on top of the splitter adding downforce. The underside of the splitter also generates low pressure (blue) and downforce but the splitter needs to be lower than about 3 inches to generate this low pressure area. Graphic by Hancha Group Consulting.
Less blue area with a splitter, blue is lift from what I can tell - it has a negative number.

There is also an explanation for "dive planes" in that link, just more down-force and more drag.
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Old 01-17-2019, 06:35 PM   #6 (permalink)
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Yep, but the air dams of I refer are behind the front of the bumper...
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Old 01-17-2019, 07:31 PM   #7 (permalink)
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Quote:
Originally Posted by fastflyer View Post
Yep, but the air dams of I refer are behind the front of the bumper...
Putting them further back is a concession to practicality, they won't scrape as much on driveways etc.
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Old 01-18-2019, 11:11 AM   #8 (permalink)
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Quote:
Originally Posted by oldtamiyaphile View Post
Putting them further back is a concession to practicality, they won't scrape as much on driveways etc.
Exactly, and the main point is - not much of a difference from the CFD images I posted.

Don't look for the small differences just yet fastflyer, look for the overall similarities to understand the concepts involved.

EDIT:
Another way to place value/importance to the forces on the chin spoiler with and without splitter relative to it's inboard or outbard distance from the center of vehicle gravity is to reflect upon "moment arms".

https://www.physics.uoguelph.ca/tuto...que.intro.html

Quote:
Imagine pushing a door to open it. The force of your push (F) causes the door to rotate about its hinges (the pivot point, O). How hard you need to push depends on the distance you are from the hinges (r) (and several other things, but let's ignore them now). The closer you are to the hinges (i.e. the smaller r is), the harder it is to push. This is what happens when you try to push open a door on the wrong side. The torque you created on the door is smaller than it would have been had you pushed the correct side (away from its hinges).
I'm just saying that the further out from the center of gravity (C of G) the more the resultant effect.

That is to say, move the same force a little more inboard, and it will not have the same effect, it will be less.

To put your mind at ease, the chin spoiler and or splitter tucked further under the car is going to exert less force because of it's shorter moment arm.

Below is an example of using moment arms to maximize down-force on front and rear axles.

https://www.f1technical.net/forum/vi...16453&start=30


The idea location for down-force on a well balanced car would be at it's center of gravity, but the wing must be much larger because like the door and door hinge example there is a very short moment arm (so more force is needed to get the same net results - work done).

https://www.f1technical.net/forum/vi...16453&start=30


By studying these extreme examples of moment arms in practice you can put in context and properly evaluate the effects of tucking inboard a chin spoiler 6-inches or so.
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Last edited by kach22i; 01-19-2019 at 12:08 PM..
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Old 01-19-2019, 12:36 PM   #9 (permalink)
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lip

Quote:
Originally Posted by fastflyer View Post
Hello, I have a doubt!

I watch several cars, how suvs with a undertray lip, behind the front fender.
And also Cámaro zl1 1LE has one.





Does it have the same properties as a normal front lip of the fender? Despite being behind?
I think that it will increase the lift, but Cámaro zl1 has one....

Sorry for my English!
General Motors has said that everything they've done on the Camaro is for high speed stability/downforce/cooling.
Don't know about the Honda.If it's like the R-spec,then it would also be about stability,at the expense of drag.
There aren't any 'clean' fast cars.They have coefficients of drags similar to a RAM 1500 pickup.
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Old 01-22-2019, 05:20 PM   #10 (permalink)
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Quote:
Originally Posted by aerohead View Post
General Motors has said that everything they've done on the Camaro is for high speed stability/downforce/cooling.
Don't know about the Honda.If it's like the R-spec,then it would also be about stability,at the expense of drag.
There aren't any 'clean' fast cars.They have coefficients of drags similar to a RAM 1500 pickup.
How about the original acura NSX? Cd of 0.32. Not amazing or anything, but not bad either.


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