Isn't a spoiler bad for performance on our Yari?

[CtrlAltDefeat]

Spoilers increase downforce at speed (like adding weight) at the rear, at the expense of drag.With front engine front wheel drive cars, I'm pretty sure that a spoiler adds to the under-steer they already have. Under acceleration adding more downforce to the back would also shift more traction away from the drive wheels and increase wheel hop. It seems to me that spoilers are purely cosmetic for our cars (adding unnecessary weight and drag too). Granted, I love how they look on Yari , but I'm pretty sure there's not any real advantage to them. What do you guys think?

[eTiMaGo]

I'm not sure that any actual empirical testing has been done but they could add to high speed stability too, like on the highway.

But yes, they are certainly mostly for looks

[markitect]

Most OEM spoilers are specifically designed to not do anything but look cool. In theory they may increase stability at high speeds, but not on our cars. For example Audi put a spoiler on the first gen TT because they had problems with high speed stability(140mph+). If you look at pictures of it it has about a 30 deg angle on it as opposed to the 5-10 deg or so the OEM spoilers have on our cars. Now if you buy a huge wing, then yes you will get some downforce.

Also as you said the force is in the wrong location for a FWD car to really benefit from it. I think you would see the most benefit from a front splitter, and/or a venturi device located in front of the back tires the second of which would give you ground clearance issues.

In either case having someone sit in the back seat will give you the same affect at high speeds(at low speeds no aerodynamics have any effect).

[kimona]

Hmmm... I wonder if a simple front spoiler would improve highway stability for the Yaris?

Has anyone noted a difference with that addition?

[eTiMaGo]

The front underpanel Micro Image sells seems very promising in that respect. Not an actual spoiler per se, but it should help reduce underbody lift at speed...

[CtrlAltDefeat]

does it actually add downwards force, or does it just prevent turbulent air and lift?

[cali yaris]

by speeding up air traveling beneath the car (smooth unbroken surface), it creates a small vacuum, which counts as downforce. So what you're saying is basically correct.

It would take a pretty high speed to be noticeable, I think.

[cali yaris]

Any rear spoiler behind the rear axles may create downforce in the back -- but it will also create a smaller amount of lift in the front (thinking of the rear axle as a lever).

[Kaotic Lazagna]

I'm pretty sure my rear spoilers is non-functional. However, I do see that my VG's on my roof actually move the air.

[CtrlAltDefeat]

It's such a shame, because I love how they look, but can't bring myself to buy a cosmetic upgrade until performance is dialed in the way I want it... (which means I still have wheels, exhaust/intake, and coil overs before I consider a spoiler...)

[markitect]

Originally Posted by cali yaris

by speeding up air traveling beneath the car (smooth unbroken surface), it creates a small vacuum, which counts as downforce. So what you're saying is basically correct.

It would take a pretty high speed to be noticeable, I think.

This may start a huge argument, but I really don't think your underpanel will make any additional downforce vs stock. Yes the smooth surface will speed up airflow(dropping air pressure relative to the top of the car), but your ignoring the pressure drop created by the black "curb feeler" that is normally under the bumber (unless you can keep this installed and your pictures don't have one because your lowered).

If you think about an airplane wing the front has a big hump on top to speed up the air flow. The curb feeler acts(to some degree) like this hump
but on the bottom and therefore reduces lift generated by the general car shape. The question is which speed up the air more, the curb feeler, or the smooth surface. Anyone got a wind tunnel?

Still I think the underpanel is a great piece and will cut the drag a lot.

And I doubt the downforce difference matters at the yaris's speed limiter.

[IllusionX]

though, our yaris come with a tiny whiny spoiler that does pretty much nothing...
it's not like we have one of those huge spoiler that not only adds downfoce at high speed, but also adds weight... (those things probably weights 5kg or something) lol.

[scape]

is there any kits for the rear underbody panel (reducing the underside of the bumper), kind of like this:





but more appealing, haha
this might make some difference in reducing drag

[lilredrocket]

To the curb feeler comment I believe that most LB didn't come with one.

For the rear diffuser question Garm will be producing one after sales pick up on the front under panel and after he makes a belly pan to smooth out under the driver and passanger.

That is how I understand everything after reading through his thread one the under panel. Please set me straight if I'm wrong Garm.

[Biggie™]

As has been touched on earlier, most OEM spoilers/wings are there to counteract the inherent LIFT that the vast majority of production cars produce at high speeds.

[cali yaris]

lilredrocket, correct about the curb feeler.

Yes the smooth surface will speed up airflow(dropping air pressure relative to the top of the car)

That IS downforce, by definition. Nothing is removed from the car to install the underpanel.

The fact is, in testing, the underpanel yielded 1-2 mpg increase. I know that's not a lot, but it proves that it is functional for its intended purpose -- to decrease turbulent airflow under the engine bay.

[Yaris Hilton]

I doubt the factory spoiler does anything other than add a couple of pounds. It's a styling touch, nothing more.

[TheRealEnth]

However, I do see that my VG's on my roof actually move the air.

VG's? like the evo sonic thing? and What are they called? and could you show me a picture =p