Does this CRV look like it needs a spoiler?

[Xringer]

I've looked at the OEM spoiler/deflector thing that Honda sells, and it seems to have a big gap under it, like it's a wing on a racing car. I can't see it doing much for the cd. Plus, it costs about $200..

I've been looking at those top-edge spoilers this afternoon while bike riding.
I noticed that many of them curve downwards to follow the roof line.

The roof line on my CRV is sloping down towards the rear too. But, for some reason, I've been thinking that a lip(?) spoiler on top of that rear window should be level (parallel to the ground).

I was thinking of a thin 'Bill' like surface (shaped like a short bill of a baseball cap) on the back edge of the roof.
It would stick out in the center about 12" and curve back in on the ends.
Be like a little sun visor.

Sound crazy or what?

I won't get into building a boat-tail, but something that gives some improvement while not looking to outlandish would be doable..

Thanks for any comments.

Cheers,
Rich

[aerohead]

I did a post on aft-bodies and spoilers.Vans and wagons(SUVs) don't produce lift and are not proper candidates for "spoilers".Since they do have enormous wakes,they are candidates for boat-tailing.The CRV does have some plan tapering to it's body,so it enjoys a little pressure recovery before the flow breaks away at the rear.The rub is that SUVs,vans,and wagons, are the worst candidates for streamlining.If you've read my installment on rooflines you'll see why.Any significant drag reduction would only come from a tail of significant length.Again,you can read about it.Some of the devices you see on backs of these types of vehicles is to direct a downwash of air from the roof,to blow stuff away from the rear windscreen,to help keep the glass clean.While air IS directed into the wake(which you might think reduces the wake drag) the device itself has its own drag,which in poorly-conceived designs add to overall drag.Body contour-following additions,as Darin has done on the MetroMPG Swift are a form of the Kamm truncated roof and are one of the "sure-bets" for drag reduction on these body styles.

[Xringer]

I knew about those down-wash things being drag makers.. I will not be buying into one of those.

After reading here for more than a few hours, I'm starting to see the limitations of the CRV's shape. No easy fix..
For now, I'm going to try the small improvements and see if I can hit my 35MPG (highway) goal without going to a boat-tail project.

Thanks,
Rich

[SuperTrooper]

Take a look at the spoiler for the latest generation CRV:



Something like this might be helpful to ease to transition of airflow at the roofline.

The more I read threads here and other eco sites, the more I'm convinced that mods need to start at the front of the vehicle, not the back.

[Xringer]

It does look better than the old Gen1 CRV model, but it looks like it still has that little
down-wash intake slot across it.. The TE looks so wide, I get the feeling that it's a down-pointing defector fence. (aka draggy fence).

If I could make something like that, but solid from the hinge seam on back.. No under-flow.
Make it rounder in the back, extended a little more in the middle.
And very thin on the trailing edge. Thin as one sheet of coroplas

Would something like that move the separation point back a ways?
Since it seems logical that moving it back would result in a little less drag..

Or, maybe slope it downwards a little, like the beginning of a truncated boat-tail.?.
I see a lot of SUVs around these days with that sloped down look on the rear 'visor'..

I remember seeing a lot of 50s cars with a visor that look kinda like that spoiler,
only they were on the front windshield..

[SL8Brick]

Instead of a spoiler, how `bout VGs?

[SuperTrooper]

Originally Posted by Xringer

It does look better than the old Gen1 CRV model, but it looks like it still has that little
down-wash intake slot across it.. The TE looks so wide, I get the feeling that it's a down-pointing defector fence. (aka draggy fence).

If I could make something like that, but solid from the hinge seam on back.. No under-flow.
Make it rounder in the back, extended a little more in the middle.
And very thin on the trailing edge. Thin as one sheet of coroplas

Would something like that move the separation point back a ways?
Since it seems logical that moving it back would result in a little less drag..

Or, maybe slope it downwards a little, like the beginning of a truncated boat-tail.?.
I see a lot of SUVs around these days with that sloped down look on the rear 'visor'..

I remember seeing a lot of 50s cars with a visor that look kinda like that spoiler,
only they were on the front windshield..

I wouldn't slope it down. If my understanding of the relavent aerodynamics is correct, you want a clean break of the air flow from the body to reduce drag. I think that's what a kammback does? Moving the separation point aft is the ideal.

A look at the typical spoiler found on the backs of Mini Coopers (a CRV on a smaller scale) shows how it probably should look:




I'd use filler to smooth the transition, but the basic idea is there. Going much beyond this, in length, may offer little improvement.

[Xringer]

Originally Posted by SL8Brick

Instead of a spoiler, how `bout VGs?

I've been studying up on VGs a bit, and it seems like they might help a little.
But the problems here are so large the effects of VGs might be unnoticeable.

[Xringer]

Originally Posted by SuperTrooper

I wouldn't slope it down. If my understanding of the relavent aerodynamics is correct, you want a clean break of the air flow from the body to reduce drag. I think that's what a kammback does? Moving the separation point aft is the ideal.

A look at the typical spoiler found on the backs of Mini Coopers (a CRV on a smaller scale) shows how it probably should look:

I'd use filler to smooth the transition, but the basic idea is there. Going much beyond this, in length, may offer little improvement.

Now that is a sweet looking little spoiler (Lip Spoiler?) That's a size that I might be able to simulate using Coroplas.
Maybe I should start looking at the rear glass with some yarn tassels taped on it. And then make a test spoiler.

[SL8Brick]

I'm not sure how well they'd work on your CR-V either, but it'd be interesting to see what that airborne dust would do if your car looked like this: