Roof spoiler and extended boot lid questions - Fuel Economy, Hypermiling, EcoModding News and Forum

Novaz_nz · 08-04-2008, 08:54 PM

Hi all,
I won an event, and the prize was the pair of spoilers shown in the picture below. I will probably fit them to the Silvia (I think they look cool).

Would those in the know care to comment on whether they will be of any advantage in the quest for cleaner aero?
At the moment they are on the "play" car, but I can source a set for the daily drive if they will be of any benefit. (Daily is also a generic 3box sedan)

MetroMPG · 08-04-2008, 09:10 PM

Hi Novaz_nz -

My opinion is that the first spoiler renders the second one useless! It ensures that air coming off the roof has no chance of following partway down the rear window before separating. Instead, its slight upward angle will cause separation higher up and a larger turbulent wake.

However, I think there's a possibility that if you leave OFF the roof edge one, the decklid spoiler may be long enough to reduce drag, if flow off the roof can reattach on it.

Wool tufts hold the answer...

Novaz_nz · 08-04-2008, 09:32 PM

Hi Metro,

I can trim down the supports to get the roof spoiler to follow and extend the roofline - would this help the airflow follow the window profile? I may as well make it as functional as possible before it gets fitted!

MetroMPG · 08-04-2008, 09:38 PM

That would be better than leaving it off, yes. Great idea - I didn't realize it was adjustable.

If you can get it to angle down a couple of degrees lower than the extended roofline, it might be slightly better still.

What will happen with the sides of the roof spoiler though - they look like they sit flush against the side of the rear window gasket

Novaz_nz · 08-04-2008, 09:47 PM

Both wings were freebies, so it can be modified in whatever way will work

If I can't get it to sit flush I will just keep trimming until it matches up (or bog / fibreglass it over).

The factory spoiler is shown in the image below, and is the only rear wing I've had on a car. Bling and tack-ons don't really appeal, it has to be functional or there's no point shelling out my hard earned. These are a little different because they were free (I would sell them, but they aren't really worth anything)

MetroMPG · 08-04-2008, 09:58 PM

Good to hear. Trim & fit, I say.

Quote:

Originally Posted by Novaz_nz

(I would sell them, but they aren't really worth anything)

They may actually be worth a little bit of drag reduction, properly modified!

What does "bog" mean (bog / fiberglass them over)?

Novaz_nz · 08-04-2008, 10:06 PM

Cool. I'll add it to the list of things to do when the weather gets better - hopefully by then I will have an MPG log so I can tell if it's made any difference. I'll start a "help me" thread for the daily when I get around to taking some decent pictures too.

Bog I think you guys call bondo? It's a body filler.

cfg83 · 08-05-2008, 01:27 AM

Novaz_nz -

Welcome to EM! Whenever I see that spoiler combo, I wonder if these could be anchors for kamm-backs. All the holes drill into the spoilers, not your car!

CarloSW2

Novaz_nz · 08-05-2008, 02:10 AM

Hmmmm. It's a good idea, but I don't know if that would be legal here.

justpassntime · 08-05-2008, 05:36 AM

Welcome Novaz,

Will be very interested in the outcome of your spoilers. I am working on the same thing for my Accord, looks as if you are a bit ahead of me. I am building mine.

I need to build a center support so it doesn't flap or vibrate. Here is what I have so far...