Green Grand Prix modding thread

[Vman455]

Originally Posted by California98Civic

Are you running grill blocking? Because that seems like it would be relevant to these pressure readings and would be really interesting if you still had such pressure differences when grill blocks and an undertray are installed, no?

Yep, factory undertray and ~50% lower grill block.

[California98Civic]

Originally Posted by Vman455

Yep, factory undertray and ~50% lower grill block.

I wonder if it would be possible and useful to plumb that pressure along the inside of the undertray and out somewhere toward the back, like the wheel wells.

[Vman455]

Bumping this thread back up. GGP announced a couple weeks ago that the next running will be April 5, 2019! Although it's been cold here and I've been busy with school and work, I've gotten a a few things done, with many more on my list before April.

Completed:
-Repaired front bumper cover with fiberglass. I had a run-in with a raccoon in Indiana a couple years ago that cracked the cover and grill in several places. I had stitched it back up with zip ties, but I took the whole thing off and repaired it properly last weekend.
-New grill block. I calculated the size of the OEM grill openings (yay calculus!) and made a stealth block out of aluminum sheet to reduce it to 1/6 the radiator area, full width slot. (I'll get a picture soon). The Prius's radiator is fully ducted in front; part of the lower duct had gotten cracked as well, now repaired.
-All else as above, except the rear seats have gone back in. Since I don't have a garage to store them in, and they're quite bulky, I swapped them back in the car for the winter. Everything else is still out, including the radio. I've come to quite enjoy the silence, especially on long road trips.

Planning before April 5:
-New tail, this time a lightweight design. Details to come.
-Thermal engine blanket, to reduce warmup times.
-Thermal cabin insulation. I got this idea from reading van forums; since I camp in this car quite frequently, and will on my way to the GGP again, I'd like to add some thermal insulation both beneath the interior panels/headliner/carpet, as well as on my window blocks. That way when I hole up for the night, I can have almost a complete insulative layer wrapping the entire cabin. And since thermal insulation is light (and is better the lighter it is), it shouldn't add much mass to the car.

4 weeks of Winter Break start after my last final tomorrow, which should give me time to work on some of these.

[freebeard]

-New tail, this time a lightweight design. Details to come.

Will you share the design before it's completed?

[redpoint5]

For some reason I forgot about this thread and assumed this was about a Pontiac Grand Prix. In which case I'd say buy full coverage insurance, and leave the keys in the ignition in a sketchy neighborhood and walk away. Those things are pigs.

Very cool though. I look forward to the results.

[mpg_numbers_guy]

Originally Posted by Vman455

Planning before April 5:
-New tail, this time a lightweight design. Details to come.
...

How much of an increase in fuel economy did you experience from your tail?

[redpoint5]

Originally Posted by freebeard

My friends have a Prius that's missing one wheel cover. I tell them it would look better if they took the other three off, but they say they like the sliver cover better. Just not enough to replace the missing one.

I was looking for a place to post that:


https://jalopnik.com/this-lifted-pri...eps-1825777000

Ha! Regen joke.

Did I ask this already... is that Lolo Pass road?



Looks like the place I get Christmas trees and almost fishtailed my truck off a cliff.

[freebeard]

Ignore the Porsche cooling fan. What's left is full wheel spats, front and rear of all four, a rear diffuser, and the Moon disks.

On the boat tail have you considered cold plasma vortex de-generators? (I forget the search term at this time, in this location)

[Vman455]

Now that this year's event has come and gone, time to turn my attention to next year. This year, this little car was the third most efficient non-plug-in overall, behind a 2000 Insight and 2010 VW Jetta 3-cylinder diesel; that's more efficient than every other Prius there except the one Prime, including two Gen 4s. I don't have any classes this summer, so I'll have a bit more time to mod while the weather is nice. The plan is:

1) Get an accurate curb weight (me + full tank of gas) on the car, at a truck scale or one of the local recycling places (we have two in town that I can potentially use)

2) Brainstorm any other weight reduction possibilities

3) Swap in the new suspension I've had sitting in my closet since last fall. They're Godspeed coilovers with 6 kg/mm front and 8 kg/mm rear springs and dampers, which will be more to my liking since the suspension is ridiculously soft for my tastes right now. I'll also be able to fine-tune the ride height; on the aftermarket Tein springs it's on now, the driver's side front sits ~10 mm lower than the passenger side for some reason. Overall it's pretty close to the optimal 0.75 body cover:tire height ratio Obidi says typically results in lowest wheel drag, so I won't be changing the ride height much.

4) More aerodynamic modifications:
-add front wheel air curtain ducts
-add front wheel strake fairings from the 2018 Ford C-Max hybrid (already ordered)
-aluminum underbody panels to replace the coroplast ones that grenaded themselves two summers ago. These will be bolted in, with a vent near the catalytic converter where the engine bay exhausts now.
-vent the rear wheel housings with convergent ducts to the rear bumper edge, and front wheel housings if I can figure out how to do that with what little real estate Toyota left there
-add hood vents
-add spoiler extension

5) Get a front photo from some distance and write a Python program to count the pixels and calculate an accurate maximum cross-sectional area, so that I can...

6) Do coast-down testing and correct for wind (good way to keep up on my physics over the summer) to calculate an accurate CD. My goal is to get under CD 0.20 with minimal extension.

I'll be attacking these in roughly that order after finals are over (week of May 13).

[freebeard]

Overall it's pretty close to the optimal 0.75 body cover:tire height ratio Obidi says typically results in lowest wheel drag, so I won't be changing the ride height much.

Explain like I'm five?

Counting pixels is tedious. I'd crop to a bounding box, reduce to black and white, do a maximal Gaussian blur and look at the greyscale value.