Yaris mods

[spookybathtub]

Here is the rear belly pan, almost completely trimmed. This covers the back 2/3 of the car. I'll use a separate piece for the front 1/3, which can be removed for oil changes, etc. I planned to use toggle bolts on some of the existing holes in the under-carriage, but that failed miserably. So I ended up drilling small holes and using self-tapping screws. I tried to use all one piece as much as possible, but I had to glue 2 coroplast strips along each side. Gluing coroplast to coroplast is the part that makes me nervous. Maybe I'll reinforce it with pop rivets. The middle part is cut out for the exhaust pipe, and I'm covering the edges with HVAC foil tape.

[freebeard]

I bought this scrap of Plexiglass just to get the fastener. I don't know a source.

It's like a captive Dzus fastener. The head is 3/8" in diameter and the post extends 3/8" on the inside. It has spring loaded pins that engage the other half.

[aerohead]

Here's an overlay of the hatchback to help you think about the rear end

[Daox]

Great mods so far. Got a grill block planned? I didn't see that on your list.

[spookybathtub]

Here's the front belly pan, and the final attachment. I'll probably add some gaff tape across that front seam, but it all seems to be pretty secure so far.

I do have a grill block planned. I want to drive around for awhile testing one thing at a time.

@aerohead, where does that overlay shape come from, is it your own creation? I'm curious about the science behind it, and is the idea to get as close as possible to that?

@freebeard, those fasteners look pretty cool. How much do they cost?

[aerohead]

Originally Posted by spookybathtub

Here's the front belly pan, and the final attachment. I'll probably add some gaff tape across that front seam, but it all seems to be pretty secure so far.

I do have a grill block planned. I want to drive around for awhile testing one thing at a time.

@aerohead, where does that overlay shape come from, is it your own creation? I'm curious about the science behind it, and is the idea to get as close as possible to that?

@freebeard, those fasteners look pretty cool. How much do they cost?

Third down from the top of the Aero Forum page is an Aerodynamic Streamlining Template tool for helping to design aft-body mods.
It was put together from 92-years of empirical research which was smattered throughout the decades (thread: Aerodynamic Streamlining Template Part-C)
NOTE: The image of the Yaris is not in 'true length' as with a blueprint,or technical drawing,so it's not perfectly accurate.

[freebeard]

@freebeard, those fasteners look pretty cool. How much do they cost?

Unknown. I bought the scrap of plastic for an example. The other half of the fastener is missing. If I make over to the westside, I could walk into Eugene Fastener and ask if they have anything similar. That wouldn't happen soon.

You might try McMaster-Carr or Grainger Industrial Supply but I don't even know what it is called.

[spookybathtub]

After a few days of driving with this belly pan, I have some noticeable results. First, my FE increased from 43 to 45 mpg (5%). Awesome. Also, it takes longer to come to a stop. A few times when I had to brake hard, I didn't stop as quickly as I expected. I will have to retrain myself in this regard, it's a potential safety hazard.
Surprisingly, when driving in high cross-winds, the car feels less stable, like I'm blown harder side to side. I wasn't expecting that.

[jimsiggy]

Originally Posted by spookybathtub

Surprisingly, when driving in high cross-winds, the car feels less stable, like I'm blown harder side to side. I wasn't expecting that.

This is just a hunch, but looking at the shape of the front of the tray, it looks as if you would be inducing some lift; kinda like looking at a boat from the front. It's trying to get on plain like a boat, that may be the source of the instability.

BTW, I have a similar car; small hatch, so I'm intrigued to see how this works for you. I plan some of the same mods.

[BrandonMods]

Great pan design!