Ecomodding 2015 MX-5 Miata

[Ecky]

A few items from the brochure from Verus, who makes the diffuser and black panels:

[Ecky]

Shamelessly stolen from someone else who has these panels installed:





Source

[Ecky]

First parts came in. Shipping took approximately 1 month. I have some ramps on the way and picked up a sheet of coroplast, which I plan to use to make a temporary diffuser.










It was raining today so I wasn't able to do any top-down testing. The notch exists so that the roof latch clears when raising and lowering the top.

[MetroMPG]

Ecky - wow. Congratulations all around!! Beautiful place to live, wonderful car to drive.

I missed this thread when you started it. Subscribed!

I'm envious of the 25 year progress in engineering between our cars. Yours gets such great highway fuel economy out of the box. Numbers that mine struggles to get with me throwing every driving trick in the book at it (except generally no P&G), not to mention all the ecomods.

I threw my mountain bike in mine this morning, the destination being about a 60 minute round trip on deserted rural roads, and I barely squeaked 50 MPG US out of it, driving extremely conservatively. Averaged maybe 40 mph.

Don't get me wrong: It was a beautiful morning & I really enjoyed the drive! (And the ride.) Still jealous though.

Are you doing any engine-off coasting? I do lots. (I avoid fuel cut/engine braking because I discovered the engine sucks a fair amount of oil past the rings under high vacuum.)

[Ecky]

Your thread was actually quite inspirational for me, in picking this car. I'm still in awe that you're able to squeeze 50mpg out of yours, when most drivers are struggling to break 30 in an NA, even driving conservatively.

I've been a bit reluctant about EOC, even if it seems like very low hanging fruit, what with how the roads are here. The push-to-start probably isn't as scary as it seems to tinker with, but I imagine some of the traditional methods of killing an engine while driving might not play as nicely with the electronics.

My biggest economy hurdle right now is in my desire to take curves very fast, which often means use of brakes somewhere down the line. There isn't a whole lot of weight savings to be found, so I'm kinda waiting to see how the nut behind the wheel adjusts.

[MetroMPG]

Wow again - the photos. So nice.


Special request: I notice most (all?) are hosted on a 3rd party server. Eventually, they will disappear from the internet... and this thread.


Maybe upload a few locally? Or at least some of the important ones?



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Your talk about the panel behind/between the headrests has me thinking.


It makes sense that could help aero, similarly to the way drag is reduced with a tailgate up vs. down on pickup trucks. Encapsulated vortex/turbulence.



Makes me want to do some tuft testing. Are you aware of any existing testing?

[Ecky]

Originally Posted by MetroMPG

Wow again - the photos. So nice.


Special request: I notice most (all?) are hosted on a 3rd party server. Eventually, they will disappear from the internet... and this thread.


Maybe upload a few locally? Or at least some of the important ones?



---


Your talk about the panel behind/between the headrests has me thinking.


It makes sense that could help aero, similarly to the way drag is reduced with a tailgate up vs. down on pickup trucks. Encapsulated vortex/turbulence.



Makes me want to do some tuft testing. Are you aware of any existing testing?

I'll upload some of the photos locally, no problem.

I haven't seen anyone publish any numbers, or even visuals (like tuft tests), it's entirely anecdotal. I can say that with the windows up and the top down, the air in the "cabin" is really quite still, except for on the top of my head and in that area between the seats.

Any ideas on how I might be able to visualize this?

[MetroMPG]

Tuft testing is the best way I know... unless you have access to a wind tunnel or really good CFD.


I was looking at my tonneau vs. the way your roof section makes a pseudo-tonneau, flush with the deck lid. Yours looks better to my eye.








I haven't done any tuft testing in a long time, but now I want to.

[MetroMPG]

Looks like the screen does cause a separation bubble in the cabin that air flows over:




Unfortunately, it's not clear if there's any benefit in terms of drag reduction.



From:

https://www.youtube.com/watch?v=0x4cnO_qrEQ

[Ecky]

I put in a few hours of driving today. Subjectively, the buffeting, which was already low, is reduced. With the windows up (top down still) it's virtually zero, and there is almost zero wind noise.

My last tank average was right around 36mpg, though it was almost 100% city driving. I'm about half a tank into the next one, and I'm sitting at 38mpg. Possibly no relation to the deflector, but rather, just environmental conditions.

I saw this fabric (?) deflector in the video you linked, and it gave me some ideas. It might also be interesting to see if there's a specific height where a spoiler would help. To my eye, the trunk lid's trailing edge is probably too low to spoil the air.