Ecomodding 2015 MX-5 Miata

[Ecky]

Originally Posted by cRiPpLe_rOoStEr

What do you mean by less aggressive? How would you expect it to affect towing capacity?

The current tires are 10mm wider than stock, and are a sticky ultra high performance summer compound - they're goopy enough that rocks and pebbles just stick into the tire, not just between tread blocks. I was thinking of dialing them back to the stock width, and maybe back to "high performance summer". They still have a lot of life left, however.

As for towing... probably not much? I was towing much heavier loads in the Insight, with 165 width RE92s.

[mpg_numbers_guy]

Originally Posted by Ecky

I have a few very small mods planned for it in the immediate future: LED turn signals, DVD player delete, a partial grille block, and when I do eventually need tires, something a little less aggressive.

How are NZ regulations for vehicle modifications?

[Ecky]

Originally Posted by mpg_numbers_guy

How are NZ regulations for vehicle modifications?

They're very explicit.

https://www.lvvta.org.nz/documents/s..._Threshold.pdf

For example:

Fitting of or modification to: LVV Certification is not required provided that: (refer to LVV Certifier if beyond threshold below):
Body kits and components (including utility canopies, plastic bumper skins and bonnet projections)
▪ the fitting system does not weaken the vehicle structure (Note 1); and
▪ no frontal impact components have been removed where the vehicle is required to comply with a frontal impact occupant protection standard (Note 3); and
▪ the kit or components do not present any forward-facing external projections that could cause injury, to the occupants or pedestrians, or present a snagging/hooking risk to a vehicle or person; and
▪ the driver’s vision has not been affected; and
▪ the performance of any lamp is not affected as a result of the kit or components.


^
Basically, they're strict on safety, and lax (or don't care at all) about emissions or power.

A vehicle needs no certification as long as it meets those standards. A one-time certification is needed if you exceed them, where a mechanic inspects it. I can, for instance, do lightweight 2 piece brake rotors without certification, but if I change the calipers for aftermarket, I need them certified - but if they're meant for the vehicle, they'll almost certainly pass.

[cRiPpLe_rOoStEr]

Originally Posted by Ecky

As for towing... probably not much? I was towing much heavier loads in the Insight, with 165 width RE92s.

Weight capacity of the tires is just one aspect. I was wondering how a different tire would affect traction.

[Ecky]

A small non-update - we're coming back toward summer in the southern hemisphere, and I haven't been driving much. I'm living a 4 minute walk from work now, and everything I need is more convenient to get by walking or a quick trip on a scooter. I've come around to the idea of going almost full-eco with my next set of tires, but more as a hobby than anything. I've also been doodling some partial rear wheel covers.

[MetroMPG]

OOo, please share doodles!


Nothing like being able to walk & bike (or scooter!) vs. drive. Quality of life.

[Ecky]

Doodles will be attached at some point! Or, I might just put them on the car.

Most tanks I use my car for either spirited driving, or for towing/carrying things, and my averages reflect that.

As of this last weekend however, it looks like I've made the top 10 gasoline cars list after my road trip. The cynical part of me suspects this is in part due to lower competition (especially as people move to hybrids and EVs), but regardless, I had 3 tanks at 4.8 L/100km (49mpg), 4.9L/100km (48mpg), and 5.0L/100km (47mpg).

Driving conditions were approximately 50-50 top up and top down, with air conditioning running when the top was up. The drive was probably 60% at 100kph (60mph), 20% at 110kph (68mph) and 20% at 80kph (50mph). Weather was warm and mostly sunny.

I haven't had much desire for air conditioning since getting the car and as such, hadn't used it much except for the occasional windshield defrost. I was surprised to find it made virtually zero difference on economy - perhaps 2% or less. I suspect fuel economy is better with the top up and aircon running, than top down, windows up, but the difference there is marginal too.

Prior to the trip I pumped the tires up to 42psi, which makes them thunderously loud on the more coarse road surfaces outside of major cities.

[Ecky]

Some more towing shenanigans. Who'd have thought that a 2 seater convertible would be a great choice when an ad says, "please bring a truck".




Lately I've been looking at ways to cut tire noise, so I can up the PSI. Once these are worn I'll switch to something more efficient. My latest bit was finding the bottom of the trunk is a drum, so I threw some sound damping and foam pad over it, and stuffed small blankets into the vent/deadspace that connects the trunk to the cabin. Small but noticeable improvement.

[redpoint5]

How was your approach/departure angles?

I hadn't thought about it until now, but I wonder if I could create a shim to slightly angle the receiver up, to counter the sag induced by heavy objects hanging off the back? Easiest thing might be some washers, but the receiver might rely on full contact with the frame for strength.

[Ecky]

Originally Posted by redpoint5

How was your approach/departure angles?

I hadn't thought about it until now, but I wonder if I could create a shim to slightly angle the receiver up, to counter the sag induced by heavy objects hanging off the back? Easiest thing might be some washers, but the receiver might rely on full contact with the frame for strength.

It sits low, but it's usable on public roads. I built the rack to sit around a 15° angle when unloaded, as I expected to always be carrying weight. I also have the ability to angle it upward a bit more by threading a bolt through the bottom, preventing the hinged part of the rack from sitting fully down.

The main issue is the bottom of the receiver contacting the ground, not the rack itself, and there's not much I can do about that. When attached, it hangs ~2" below the diffuser in the rear, and can't easily be given any more clearance.