Prius aero mods (undertrays, grille block, mirror delete...)
 

Note: see also Autospeed article: adding a chin undertray to a 1st gen Prius

http://us1.webpublications.com.au/st.../2456_25lo.jpg
This is the 1st gen Prius tray.


I did this about a month ago....
http://www.cleanmpg.com/photos/data/500/DCP_6376.JPG
http://www.cleanmpg.com/photos/data/500/DCP_6374.JPG
Compare to the Prius undertray in this article: Autospeed article: adding a chin undertray to a 1st gen Prius

At least we are on the same page.

Yesterday I kicked it up a notch.....
http://www.cleanmpg.com/photos/data/500/DCP_6372.JPG

Prius Rear Undertray Rear View. The drivers side does come with a tray (diffuser) but the passenger side is open due to the complication of the muffler and exhaust. I used a screw thru the coroplast about 1" long that rests on the muffler to keep a gap between the coroplast and the muffler. From the rear, the white coroplast was quite visible. The green paint was all I had. I also ran out of coroplast. Once I get more I will do something less piecemeal and paint it black. I have yet to go for a drive. Hopefully nothing falls off.

That front undertray looks smooth! Nice work.

Where does the forward edge of the rear tray attach? What's the leading edge position relative to the control arm?

PS - why is your grille not (partially) blocked? Inverter cooling concerns?

I want to call it the rear axle, but that is not a good name for it. The horizontal member between the two rear wheels is heavy gauge steel formed into a "V" cross section the point of the V is facing forward, one leg horizontal and the other sweeping down at a 45 degree angle. This forces any airflow down underneath. Within the V is a torsion bar. The leading edge of the coroplast conveniently rests in the V just under the torsion bar. I used wire ties in three places around the V shaped member. Did that answer your question?

Well first of all it's warm down here so keeping the engine warm is not a concern. Last year I did tape up both grilles and monitored the coolant temp. Normally it stabilizes at 185F. With the bottom grill blocked, the coolant temp did not change. With both blocked, the temp would cycle between 205 and 195 because of the fan kicking in. So one or the other is fine, but both is not good.

From an aerodynamic perspective, grille blocking is worth looking into. In fact, I will be heading up north next weekend to do some "research".
I also have one more aero mod in mind. Hopefully in a few weeks I will have something to show.

Thanks, yes I can picture the rear undertray setup.

I wish the Prius had caught on more up here than it did, so I could find one to look at more closely.

The Camry hybrid has been outselling the Prius in Canada - I know 3 people who own them.

Looks good. I like the rear underbody panel very much. Let us know how it works!

Well first of all, nothing has fallen off or melted, so that is good news. As far as effect on FE, it's hard to say for sure. Comparing today's drive to work with one a week ago which had the same temp and wind direction and speed, I noticed a 2 mpg gain after adding the rear pan and removing the passenger side mirror. But I can't be sure that the gain can be attributed to those changes because 10 days ago I had new tires installed which tanked my FE by 6 mpg. It could be the new tires breaking in.

Update:
I met with Frank with Hybrideffects.com last Saturday. We used my car to make a mold of a lower grille block. Frank will be making me a fiberglass panel that will fit over the lower opening and hopefully I will have it installed soon. I will post pictures when I get them.

The grille block will have no openings to begin with. If I need more than the upper grille for cooling, then I will use a hole saw to cut a few openings. I will use a rubber plug to close them when I don't need the extra airflow.

I was able to get a 4x8 sheet of black coroplast. It is getting quite pricey now. The first time I bought coroplast, I paid $15. Now it is up to $30. I guess we can blame the ecomodding craze for that.

This weekend I hope to do a complete underbody pan. I also plan on working on a RH mirror delete cover panel and a windshield wiper shield.

A few weeks ago I installed new tires, ContiPremierContact in the OEM 185/65/15 size. These were highly rated by CR for low rolling resistance but they have fallen far short of my expectations. At first, my FE dropped by 10%. After 2000 miles, I still see a 5% reduction. When I put the Integrity's back on, the FE goes back up to the previous levels. When I finally do some tests to determine the effectiveness of all of these mods, I am hoping that the Conti's break in fully and get me back to where the Integrity's were. What would be really great is if I can find someone local with a Prius who could do a few highway runs so that we could do some comparisons. PM me you are willing to participate.

Hi,

Is the panel going to be flush with the bumper or inset at the grill? Also, what are you going to make the under pan out of?

It will be flush with the bumper. I am using coroplast for the under pan.

Did Frank mention anything about the rear wheel skirts.

He did mention rear wheel skirts, but he is trying to get to market with something ASAP. The front grill block will be the easiest and quickest. I think his next project will be decided by whatever mod has the highest level of interest by those on this site and others. Why not reassert your interest on the hybrideffects thread.

Hi krousdb,

What is coroplast made from ? What is $100 a barrel now ? Maybe that is why its twice as much. I think we need to move to a future where petroleum is not burned and only used for plastics. That way, its sequestered. Like it was in the ground for many years.

Ran out of coroplast, again!
Full drivers side belly pan. 2/3 passenger side, missing middle 1/3.
http://www.cleanmpg.com/photos/data/500/DCP_6398.JPG


RH Mirror Delete
http://www.cleanmpg.com/photos/data/500/DCP_6396.JPG

Ready for bondo on the inside. Need to go get some later tonight. Once the inside is filled in, I wall add bondo to the outside to build up the contour. Then sand, primer sand and paint.

http://www.cleanmpg.com/photos/data/500/DCP_6397.JPG

Are you planning to cover more? If I recall, when you did the VX and Del Sol, you covered everything, but left a channel/gap where the exhaust was routed.

Yes, just need to convince my wife to get more. The store closes before I get home from work and they are not open on weekends. I guess you don't need to be open much if you can get someone to pay $30 for a 4x8 sheet.

Looking very good:thumbup:

Maybe I missed it somewhere, but are those just sheet metal type screws holding it all on?

And, how much of an issue will it be to you when you have to remove this for some type of regular mtce/repairs?

Yes they are sheetmetal screws. I will have to remove for inspection and oil changes.

Finished the RH Mirror delete last weekened.
http://www.cleanmpg.com/photos/data/500/DCP_6400.JPG

Looks slick, Dan.

krousdb -

Thanks for posting the details! I am most interested.

CarloSW2

Nice work!

Update?
 

Any update on the results, after your latest coroplast addition?

Welcome to the site!

I'm curious too, though, dan!

krousdb,

Nice job on the mirror delete.

Mods like these are difficult to measure separately so I can't say if there is a difference. But as a whole, I believe that everything I have done is worth about 3 MPG at 60 MPH. The easiest way to get a direct comparison would be to use a non-modded car as a control and run tests on the highway and compare the results. Maybe we could do something like that at hybridfest.

http://img257.imageshack.us/img257/4...6404du3.th.jpg

I installed my hybrideffects.com grille block today. I noticed a quicker warm up, but the normal operating temperature remained at 186F at 48F ambient. It is raining here so I can't quantify any FE gains at this point.

For reference, this is a coroplast version on my old Del Sol from a few years ago.
http://img329.imageshack.us/img329/7987/dcp60280tb.jpg

nice work, I would to see your coefficient drag after such modifications.

Hybrid Grille Block
 

http://www.prestoimages.com/store/rd...d1271677_1.jpg

Do not they make clear duct tape? Photo shop on pic 1 ease.:)

I am interested in knowing if the car handles better and the fuel milage change. Great job Dan! Thanks

http://www.hybrideffects.com/catalog...ects/pd1271677

I used a bead of clear RTV for installation.

As soon as it stops raining here I will get a better idea about any FE benefits. In the morning my water temp usually takes 5 minutes to reach 157F. Now it takes 3 1/2 minutes. FE in the first 5 minutes went from 45 to 50MPG. So far the warmest ambient has been 55F and I show no difference in max water temp, 186F.

http://img187.imageshack.us/img187/8869/dcp6408ape5.jpg

Finally got to wash my car now that the water restrictions have been relaxed.

Yesterday, on the way home from work (37 miles on I-95), with a 12 MPH tailwind, 72.1 MPG at 59 MPH, 86F. A new record for me.:thumbup:

For the entire 67 mile trip, 73.5 MPG, also a new record.:cool:

Nicely done.


For the mirror delete, did you use bondo to fill in the hole left over from the original mounting? Can you recommend a good place to look for interior mirrors?

I'm looking to do a mirror delete on my Golf, and I'm having a hard time finding appropriate mirrors to go on the inside, and panels for the mounting plates.

The lower grille cover looks awesome.

Yes,
I used bondo. My inside mirror came from Walmart.

Any additional details on how he did this? I'm looking for some direction on how to do something similar to my civic.

K
 

I have around 25 years of custom corvette painting experiece and mold making it helps. You will need to make your front bumper flush and then make a mold of the front bumper. I used fiberglass to make mold and bondo to make the bumper a plug.

Which thickness of coroplast do you use. The choices available to me are 1/8", 1/4", and 3/8". With 4x8 sheet prices of $18, $45, and $60 respectively. Should I use the same thickness for both the underside and the wheel skirts. I have found no references to coroplast thickness in any of the articles.

Which thickness of coroplast do you use. The choices available to me are 1/8", 1/4", and 3/8". With 4x8 sheet prices of $18, $45, and $60 respectively. Should I use the same thickness for both the underside and the wheel skirts. I have found no references to coroplast thickness in any of the articles.

Hi,

I'm curious where you got your flush wheel covers, and how they are working for you?

I am confused. My post asked how thick the coroplast was that was used to make grill shields and belly covers. I still need an answer to that question. Coroplast is available here in 1/8", 1/4", and 3/8".

Hi,

Most Coroplast used around here is the 4mm, which is 0.157" so, roughly 1/8".