"MPGiata" modding thread: aiming for 50 MPG with a 1990 Miata. Update: success, 55 MPG!

[Cd]

I'm late to the party.
Do you still have this car ?

[MetroMPG]

Still have it!



At least it was still in my garage last time I checked a couple of weeks ago. It'll go on the road in July-ish.

Further ecomods planned his summer:

- I recently came into posession of a large capacity 12v battery, so there may be some alternator-less motoring
- rear skirts
- rear tire deflectors
- belly pan


I probably won't get all of that done, but it's good to have dreams.

[Ecky]

Originally Posted by MetroMPG

Still have it!



At least it was still in my garage last time I checked a couple of weeks ago. It'll go on the road in July-ish.

Further ecomods planned his summer:

- I recently came into posession of a large capacity 12v battery, so there may be some alternator-less motoring
- rear skirts
- rear tire deflectors
- belly pan


I probably won't get all of that done, but it's good to have dreams.

If you don't have time, you could of course give it to me, for my ever-expanding fleet. I'd park it next to AeroCivic.

[Cd]

Darin - reading that you refuse to add a top to the car was painful to read.
A top could be made to come right off with just a few bolts or something fancier that is quick release.
You could even make it out of canvas stretched over ribbing.

It would be for SCIENCE, man ! ( Lol )😛

I even started looking for a used one myself to modify.
Just a toy project I would keep at my parent's place.

I was thinking I could find one for like $1,200 , but then saw the insane prices the cars are fetching now.
I have seen several 1990 cars going for 12 -14 K !
It's funny that you called the car the same thing as what I did - I told my sister I was looking for a little 'turd bucket ' Miata.

So this is my dream :
Modify a Miata into something like a Panhard LM 64.

That drag coefficient was .12 - POINT TWELVE !
Even if off by several counts in reality, this is a car that has one of the best cD figures of all time on a side by side "real" car.
I realized that the upright fins actually have another purpose besides stability : safety.
The car is so low to the ground and the tail would pretty much be a ramp to a large SUV driving behind you.
( One of the reasons I gave up on the dream of creating a Karman Ghia streamliner )
Not only could the fins add a tiny bit of safety from behind ( If they had a strong steel bar inside ) but they would also make the car more visible in parking lots.
There is a fella that added a full boattail to Prius has had the problem of people wrecking into it because it is so low at the back. The fins could help this problem.
As a bonus, you could be amused at the people asking you if you drive a fake Superbird kit car.
(They would have no idea that the Superbird copied the LM64. )

[MetroMPG]

Originally Posted by Cd

Darin - reading that you refuse to add a top to the car was painful to read.
It would be for SCIENCE, man ! ( Lol )��

Sorry to disappoint!

But the main reason for buying this car was its lack of roof.

I realize trying to optimize a convertible for better economy is kind of like adding insulation to the walls of a room with permanently open windows. It's not ideal. But that's where I am with it.

MPGiata is coming out of hibernation this week!

[Piotrsko]

Well other than the huge vortex caused by the windshield, shouldn't be that difficult with flow directors and straighteners, If it's a proper rag top and has a calm area for passengers. Think of headrests. I like the challenge. Tufting the flows will be tough however.

[MetroMPG]

Well, I started it up to pull it out of the garage, and it only ran on 3-cylinders for about the first 45 seconds or so.

It was totally fine after the second start.

I was able to ID the problem cyl by touching the head near the exhaust ports looking for residual combustion heat, so I know which spark plug/wire/coil to investigate.

In previous years there was sometimes a brief miss on one cyl on cold starts, but never this bad. That one cyl wasn't firing at all!

[MetroMPG]

First trip of the year, and first fill @ 51 MPG US.


(Thought 90% of the driving for the tank happened last fall.)

[MetroMPG]

I did a synthetic oil & filter change today, the first in a couple of years @ ~10k km = ~6k miles interval.

I'm confident I understand the oil consumption issue now based on frequent oil level checks and record-keeping since last year: as long as I avoid high vacuum (eg. high RPM DFCO), it hardly uses any oil. That translates to more neutral coasting and slightly more brake use.

Next mod!

I have a large capacity deep-cycle battery on hand, so I'm going to put it in and do a bit of alternator-optional motoring this tank. It'll add 20-30 lbs of battery weight, but that'll be outweighed (ha!) by the reduced engine load.

Next next mod!

I'm also on the hunt for a pair (or set) of Prius tires for the back wheels for slightly more of a gearing boost. The stock 5th(?) gen Prius tire is a 195/65R15 Bridgestone Ecopia EP422 plus. I actually know several people with Prii, but sadly they're not close to replacing them yet.

[MetroMPG]

Foiled by the alternator!


It's a 1-wire unit. Meaning, unlike the Mirage, disconnecting the field/sense wire connector doesn't disable it electrically. It just defaults to a high charge rate.