Extending the Decklid (Toyota Echo)

[MetroMPG]

True.

But I have no doubt they'd send flow to that spoiler after testing them myself on a Corolla - not quite as steep, but you can see in the video they completely remove the separation bubble at the bottom of the rear glass/forward part of the decklid - http://ecomodder.com/forum/showthrea...olla-2390.html

[CigaR007]

Originally Posted by MetroMPG

The question is how do you know that the net energy cost of adding VG's is less than the benefit of getting that airflow to the spoiler for clean separation.

That is what I want to find out as this will be a trial and error type of experiment. I am religiously following Mitsubishi's take on VGs.

http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

However, the VGs that are installed for generating
streamwise vortices bring drag by itself. The actual
effectiveness of installing VGs is therefore deduced by
subtracting the amount of drag by itself from the
amount of drag reduction that is yielded by shifting the
separation point downstream.

Given that Mitsubishi and Renault have undertaken that strategy, I am certain it has merit, if properly applied. That is where the challenge resides imo.

[aerohead]

Originally Posted by MTrenk

"Bigger" and "smaller" wakes don't really matter, it's the measured turbulence, which... you have to measure through trial and error or CFD. Smaller wakes can create more turbulence than big wakes depending on the resulting flow of the air, but you can't really argue over because there isn't any evidence lol

As far as the Fusion goes, I see that the back end of the spoiler certainly matches up with the face of the trunk, but to my eye, it sure seems like the beginning of the spoiler is raised a bit (maybe less than an inch), and I only say this because if they did raise it an inch at the beginning, they did it for a reason. But it is no matter anymore.

It might be beneficial if we qualify a context in regards to wakes when discussing quanta associated with them.
The type of vehicle design (squareback/notchback/fastback),etc.,has much to do with the wake and how it might be managed.
I'm guilty of pushing the smaller wake,in context to the 'Template' moving the separation point rearwards, such that when the air finally does separate,t
he wake produced is smaller and of higher base pressure,and free of attached vortices,all leading to lower pressure drag,and with it,lower profile drag.Hucho states that this is the premise of streamlining.
Since the wake is turbulence by definition,and streamlining reduces the size of of any given vehicle's wake,we've been using this relationship as a talking point.It is a bit of a convention.

[aerohead]

Originally Posted by CigaR007

That is what I want to find out as this will be a trial and error type of experiment. I am religiously following Mitsubishi's take on VGs.

http://www.mitsubishi-motors.com/cor...004/16E_03.pdf



Given that Mitsubishi and Renault have undertaken that strategy, I am certain it has merit, if properly applied. That is where the challenge resides imo.

Try and stay away from any spoiler which produces anything close to a 28-degree angle when measured projecting up and forward,grazing the backlight or it's header.
This 28-degree angle has been found to create flow which is be extremely unstable.The wake behind the Echo will jump between a square-back and fastback type wake,playing hell with the drag.
And limit your up-kick angle (if you use it) to no more than 30-degrees.
CAR and DRIVER Magazine investigated spoilers back in the 1970s and found that drag increased when their spoilers exceeded the 30-degree mark.
Good luck!

[MTrenk]

A few points:
--> Spoilers are for good looks, or downforce. Recently someone developed an awful looking spoiler for vans that does crazy things to the flow behind the van resulting in highly decreased drag. Spoilers can be used correctly for lift, downforce, or drag reduction.
--> VG's are awesome and I followed Mitsubishi on that development as well. It's an effective solution, and that article is quite detailed, so if you're going for a trial and error process, they give you a fantastic set of conditions to start with! However, notice their tests are in line with what I've been saying: hours and hours of wind tunnel testing AND CFD. So good luck lol.
--> Best eco cars out there are just a bunch of airfoils connected together to protect the parts and driver of the car. Airfoil shapes win everytime.

[CigaR007]

Originally Posted by aerohead

Try and stay away from any spoiler which produces anything close to a 28-degree angle when measured projecting up and forward,grazing the backlight or it's header.
This 28-degree angle has been found to create flow which is be extremely unstable.The wake behind the Echo will jump between a square-back and fastback type wake,playing hell with the drag.
And limit your up-kick angle (if you use it) to no more than 30-degrees.
CAR and DRIVER Magazine investigated spoilers back in the 1970s and found that drag increased when their spoilers exceeded the 30-degree mark.
Good luck!

Duly noted ! Many thanks !

[ChazInMT]

Mauricio, I measured your current spoiler to backlight top at 20°, so unless you take a torch to your trunk, you'll be <28°. Just say No! (to the torch)

[CigaR007]

Originally Posted by ChazInMT

Mauricio, I measured your current spoiler to backlight top at 20°, so unless you take a torch to your trunk, you'll be <28°. Just say No! (to the torch)

Can't say I fully understand what you mean regarding the angle.

[aerohead]

Originally Posted by MTrenk

A few points:
--> Spoilers are for good looks, or downforce. Recently someone developed an awful looking spoiler for vans that does crazy things to the flow behind the van resulting in highly decreased drag. Spoilers can be used correctly for lift, downforce, or drag reduction.
--> VG's are awesome and I followed Mitsubishi on that development as well. It's an effective solution, and that article is quite detailed, so if you're going for a trial and error process, they give you a fantastic set of conditions to start with! However, notice their tests are in line with what I've been saying: hours and hours of wind tunnel testing AND CFD. So good luck lol.
--> Best eco cars out there are just a bunch of airfoils connected together to protect the parts and driver of the car. Airfoil shapes win everytime.

The challenge with airfoils is the adaptation of a 3-dimensional flow, bluff body, 'door-slammer', production automobile in ground-effect,to a 2-dimensional flow body which typically requires a prone or supine body position to fit inside of.
Airfoil shapes do nice on closed-course,and controlled-access race courses.

[aerohead]

Originally Posted by CigaR007

Can't say I fully understand what you mean regarding the angle.

You're in safe 'angle' territory thanks to Toyota's design,and Chaz's scrutiny.