I killed my Mazda.

[Assiduous]

Thanks Pete, well your 5.11 has certainly set the benchmark. I have instrumented mine with a UTCOMP-PRO. I've got a traffic light free control segment on my commute that i collect data over in light traffic conditions. My best A-B-A fuel consumption is 4.7 L/100km @ 83km/h - no warm up, no braking & modest P&G.

Agreed on the car Pete i do hope to hold on to it for a while, and i also would like another gear at highway speeds. I might take a lead from you and step up to 185/70 on the next set of tyres.

Did you experiment with grill blocking? Mine seems to take some time to warm up - so much so that i'm planning to check the thermostat to see if it is frozen open. According to my UTCOMP data, my Astina is fully warmed up when the coolant temps hit about 82C. On a recent drive it took over 12 minutes to hit these temps (~10C ambient) which incurs a significant hit to fuel economy due to rich running. Very interested in your observations commuting out of the blue mountains. I'm thinking there are definite gains here as my partners Swift warms up in a fraction of the time of my Astina.

[D.O.G.]

In regards to grill blocking:

My commute wasn’t “normal”.

On a good day, I could coast (engine off) far enough downhill that the engine temp went down in between pulses. I could be halfway down the mountains before maintaining operating temps without a grill block.

The problem with a fixed block is that it has to accommodate worst case conditions. For me, that was climbing the mountains going home.

The best version I used was 60% completely blocked (30% either side) then the whole thing covered in shade cloth. At lower speeds most of the air passed through the shade cloth, as speed increased, more and more air was blocked.
I didn’t get overheating issues, but did remove the completely blocked sections (so it was all shade cloth) in mid summer just to be safe. My commute was 25 km mountains, 20 km motorway, last few km urban.

As a side benefit, the shade cloth was almost the same shade of green as my car, so it wasn’t obvious to casual observers.

[Assiduous]

The shade cloth is a good idea, might even keep debris away from the radiator as a bonus.

I've tested a pool noodle ~50% grill block through the cooler seasons to good effect on temps. Even with no grill block my Astina will fairly quickly rise to fan activation temps when caught in traffic, even at mild ambient temps so you are right to be cautious mid-summer. Ack the cooling worst case - it's finding the trade off that allows the fan to do its job in traffic in summer, but also harvest a Cd reduction at speed. My hypothesis is that substantial blocking could make little difference for this stuck in traffic corner case as even a 25% inlet won't bottleneck the cooling fan. It will however mean the fan is quicker to activate and may thus have to run longer. I'll keep a sharp eye on the temps as i test this - my real time digital temp readout and programmed temperature alerts give me confidence i can intervene before cooking the engine if i'm wrong. Grill block version 2 is a side to center 50% coverage paired with flush fog light recess covers. Yet to test.

Did you have a go at measuring Cd and Crr for either of your Astinas Pete?

[D.O.G.]

Originally Posted by Assiduous

Did you have a go at measuring Cd and Crr for either of your Astinas Pete?

No, I never tried to measure mine.
Factory Cd figure for the hatch is 0.32.
I don't think the curved rear end helps, most modern cars feature hard edges to act as trip points at the sides.

[Assiduous]

Ok, i'll try taking some measurements in the near future. Particularly Crr as...

I've just finished a right front brake service - both sleeve pins were stuck and the M-spring was missing. I was hoping to improve my Crr by addressing this, but my testing shows that all the friction seems to be somewhere in the drive chain. Even with no brake drag i only get about ~half a revolution from a two handed spin of the wheel.

The rear dead axel's spin for many revolutions.

Did you find this to be the case also with your Astina's Pete?

[D.O.G.]

I had a similar issue with the left rear caliper, fixing it increased (restored) coasting distance by a noticeable amount.
As you've found, the front wheels are hard to test due to the drive line drag.
I lubricated the front to be sure but noticed no improvement.

If you have access to a non-contact thermometer, check rotor temps after driving.
There should be a big difference in temps if the brake pads are dragging on any wheel.

[ThermionicScott]

Or if you don't have a fancy thermometer, you can make a quick round of the car after driving and touch each wheel near the hub.