2008 Honda Accord sedan aero improvements
 

Hi all,

Anyone done any worthwhile minor changes? Rear lip spoiler? Upper rear window spoiler? Or found that a full lower grill block is safe in weather from 70-95F(21-35C)?

Thanks!

Define "worthwhile." :)

Most individual changes will be undetectable in the normal variability of tank-by-tank results. (Not the same as saying they don't work, just that the impact is small.)

I definitely wouldn't do a rear window spoiler on a sedan. That separates flow near the maximum cross section size. I'd consider a small decklid spoiler though. (Like the Civic Hybrid used.)

Off the top of my head, I'd consider (in order of effectiveness & ease):

- partial grille block (with ScanGauge to monitor coolant temps)
- passenger mirror delete
- smooth wheel discs
- passenger wiper delete / cowl block
- lower air dam
- rear wheel skirts

Consider doing an upper grill block vs lower. Look at the corvette and other sports cars front layout where they intake cooling air almost always on the lower portion of the front. The bottom is messier for aero anyways, might as well keep the air path going over the car as smooth as possible.

Having experience grille blocking 2 different accords, i've got some info for you.

Previously I had a 2005 4 cylinder 5mt, I could block MOST of the bottom grille, but not entirely or it would start to overheat. I don't remember which temperatures were too hot for it. Never tried an upper grille block on that car.

With my current 2006 V6 6mt I usually run a 60-70% lower grille block. Above 85 degrees and the fan kicks on a lot. When it drops below 50 degrees I can run a partial upper grille block, usually blocking half of the upper grille.

If you are willing, I strongly recommend pulling off the front bumper and making a panel to ensure the incoming airflow going to the lower grille does not bypass the radiator by going underneath it. I did this and a partially ducted grille block and was able to make the opening smaller while keeping the same cooling capacity, if not better.


Rear window spoiler: Absolutely not, you will only increase the drag.
Trunk lid spoiler: If you can get one for cheap/make one then you should consider it. This is something that will likely not pay itself back unless you DIY.


A full undertray will definitely be worthwhile as far as aero goes, but it is a lot of work. I've got a mostly full undertray on my car and it definitely improves coasting, as well as high speed stability.

Daschicken - thanks!Was hoping you'd chime in with your first-hand experience.

Thanks all! Anyone else care to chime in? I know this generation is incredibly smooth under the body.

You sure about that? From what i've heard, the 8th gen accord drag coefficient is around .31 instead of the 7th gen's .30.

Here is the underside of a stock 7th gen
Attachment 22429

Well, as sure as Honda is. They state 7G sedan was 0.34 and the 8G is 0.31here:

2008 Honda Accord - Body - Honda.com

I've looked into that before and came to the same conclusion that someone else has: Honda used the term "previous generation" very loosely. Those drag numbers are for the 6th gen accord.

Did you make a decision on any potential mods yet?

Sounds reasonable.

My old-school Turbo car has bonnet vents and bonnet scoop. Because of a Top-Mount-Intercooler it got to a point where it had significant cooling issues.

https://bringatrailer.com/wp-content...RC_Front_1.jpg

What I learnt from it is that reverse scoop bonnet vents are the-best*. Within that model Toyota found that out as well and the factory did actually change the design completely over to reverse-scoops.

http://www.subaru-impreza-body-kits....OP_BUG_EYE.JPG

There are various different types and will let air out away from the frontal area. Since hot air rises, it's easy to work out how they work.

Ordinarily on most passenger cars, they are designed on the premise that if airflow is fast enough, hot air will be pushed down and under the car and out the back. That's true, but hot air prefers to rise.

Anyway, I support blocking off the front in the way that others do and suggest the investigation of reverse-scoops to get back what you are losing.

Perhaps there is another way of dispensing the heat such as using black panels to disperse heat in stealth mode. In a way that would only show up on a thermal camera - :cool:

Thanks to aerohead I will be adding a rear lip spoiler. That's it so far unless I add some vortex generators at the rear roofline.

Vortex generators are frequently discussed on here, and I have yet to see any improvements from cars. Trucks are another story, but cars are not designed like trucks. I have looked up vortex generators before and the people selling them claim all sorts of things they don't do, such as 'reduced wind noise'. No, they actually increase wind noise.

Don't waste your money on that. I mean, you can if you want, but I wouldn't. I would buy another 4' x 8' sheet or 2 of coroplast for vortex generator money.

See if the underside of your accord is anything similar to this:
Attachment 22512

If it is, then you could get the 7th gen hybrid rear diffuser, which looks like:
Attachment 22513

I got mine for $40.