Secrets of the Mirage

[Loren]

Got the crankshaft pulley installed. It is 1.8 pounds lighter than stock.

Doesn't feel any different. And the difference in acceleration is simply... none. My acceleration test is 1500-6000 rpm in 2nd gear. Using 30 fps video, the difference in acceleration (there has to be one, it rotates, and it's lighter) is pretty close to in my margin of error. I could really stretch and say it's a tenth of a second faster. But, I think I'll just grudgingly say "maybe a half a tenth". It's not a lot, I'm not gonna lie! But, if it is .05 seconds improvement on 8.1 seconds... that's 0.6%. And, would you really expect more?

I figure that's 0.6% on top of whatever a lightweight flywheel gets me... still working on that one.

[CaptainSquirts]

Hmmm never thought about a lite weight flywheel improving acceleration. Is it because of less rotating mass or something?

[Loren]

Yup.

[Loren]

Just tripped 40k miles. Kinda surprised, I really don't drive that much, at least I don't think I do. But, I've done over 9,000 miles in 13 months.

9,000 miles, two sets of tires, one oil change, $1500ish in mods, 206 autocross runs, one championship, and a lot of silly fun!

[Loren]

Need more quickness. There's a certain Krautwagen that's way too fast!

If I wasn't leaving on vacation tomorrow, I'd surely yank the back seat out. Today, I made runs with and without passengers. An easy half second for <150 pounds. That's a tenth for every 30 pounds! The back seat is 2/10. The spare is 1/10. Taking the floor mats out (I usually toss them in the rear floorboard) is almost 1/10.

This car needs a diet. (oh, and I've lost 17 pounds, myself)

[Native]

There's a certain Krautwagen that's way too fast!

BILL - there's your new forum signature.

I've lost 17 pounds, myself

Keep up the good work!

[AScoda]

That's a tenth for every 30 pounds!
Taking the floor mats out (I usually toss them in the rear floorboard) is almost 1/10.

1) Who is tech-ing you with floormats in the rear floorboards?
2) Your floormats don't weigh almost 30 pounds

[Jamie]

That's a tenth for every 30 pounds!
Taking the floor mats out (I usually toss them in the rear floorboard) is almost 1/10.

1) Who is tech-ing you with floormats in the rear floorboards?

Nothing illegal about floormats in the back. Or for that matter, in the passenger footwell. No pedals to interfere with there.

2) Your floormats don't weigh almost 30 pounds

His back seat doesn't weigh 60 lbs, either!

[Magooiii]

That's a tenth for every 30 pounds!
Taking the floor mats out (I usually toss them in the rear floorboard) is almost 1/10.

1) Who is tech-ing you with floormats in the rear floorboards?
2) Your floormats don't weigh almost 30 pounds

[twistedwankel]

2) Your floormats don't weigh almost 30 pounds

Mitsubishi got the contract for removing all the depleted uranium from the Japanese typhoon nuke accident. So there you have it.

[Loren]

Whatever they weigh, it all adds up.

[mymomswagon]

There's a certain Krautwagen that's way too fast!

[emoji38]
BILL - there's your new forum signature.

I've lost 17 pounds, myself

Keep up the good work!

seriously considering that signature.

two can play weight game. my wife would love it if I would drop a few.

edit:
Steve, come to think of it, at least when you're driving, the sportsperson like thing to do is just add some weight to the wagon so Loren does not have to go to so much trouble.

[Loren]

Well, we found one thing you can't do in the Mirage. (I mean, besides accelerate, or pick up chicks)

Shifting from 2nd to 1st at 54 mph doesn't seem to be something the valvetrain approved of. The solution to that problem warrants it's own thread.

Hopefully, we'll get a newer 2017+ engine with that extra 4 horsepower, and add some lightness to the flywheel. And, if all goes well, we'll be back in action for the Nov 17 Open event!

[Loren]

So, the engine done blowed up. Did I mention that?

Well, here's the plan:
2017 engine w/ 20k miles. +4 hp (5%)
Lightened flywheel. Maybe 3-4 pounds lighter? (1%)
Smaller battery with smaller battery shelf, maybe 30 pounds? (1.5%)

All told, I should see a net improvement of about 7.5%. And then in a couple months, we'll be putting wider tires on the front. The car might actually approach something in the vicinity of "almost fast" by the end of the season!

[Loren]

I think I'll revise that to "almost not quite slow" for the sake of accuracy.

Took the flywheel over to a friend's shop to put it on the lathe. Turns out his lathe is TOO big. The center hole in the flyhweel is too small.

But, "he knows a guy" who is a racer and has a machine shop. So, he's going to take it to him tomorrow and see if he can do it.

Otherwise, the engine is out of the car. New engine should be delivered this week. Ordering a clutch kit. And will do the battery probably sometime this week, as my work schedule seems light.

[Loren]

Second option for the flywheel fell through. Third option, machine shop that does a bunch of spec Miata engine work... they're doing the job for $40. Don't know how much they're going to be willing to take off of it, but I guess I can't complain for $40.

The replacement engine showed up today, along with a pile of brake parts and hubs and engine mounts. They forgot the caliper brackets, but are going to send them to me. Otherwise, I have everything I need. The engine was a clean "quick pull", so it has absolutely everything except for the coil packs, as promised. They even cut the harness, so I have spare connectors for everything, extra hose clamps, etc.

Weighed the battery and brackets today. The battery weighs 34 pounds. The main support bracket weighs 1.8 pounds, and the battery tray and tie-down weigh another pound. I'll probably use the main support bracket because it provides a nice horizontal shelf and also a bunch of brackets for wiring harness and stuff attach to it. But, whatever I use to tie down the replacement battery will weigh next to nothing, so there will be at least a half pound saved on battery tie-down stuff. (yawn)

The battery itself. Geez, I went down this rabbit hole (again) a few months ago and decided to just buy a cheap cycle battery. And I *did* buy one, it just arrived to me damaged, so it didn't make it to the car. But, last night I went back down the rabbit hole again. Lightweight stuff is just SO tempting!

OE battery = 34 pounds. (525 CCA, absolute overkill)
9 Ah AGM motorcycle battery = 6-7 pounds. (120-190 CCA... people use them in Miatas all the time)
Lithium equivalent of the 9Ah motorcycle battery = 1.5-2.5 pounds.

I can get a "good" AGM battery for around $35. (the first one I bought was non-AGM, about $15, and they skimped on packaging it) That's 28 pounds of weight for $35!

From there, the cheapest Lithium battery is around $80. So, $80 to save 32 pounds... which is still pretty good. But, compared to the AGM... it's $45 for the last 4 pounds. Which STILL isn't all that bad when you're talking about a lightweight car! I was really on the fence about it for a couple hours. Problem is that the first Lithium technology (LiPo) just plain sucks for cars. It doesn't tolerate being discharged too far at all, it doesn't charge properly with a standard automotive charging system, it doesn't handle temperature extremes, and it's prone to -splodin'. The newer Lithium tech (LiFePO4) is better on almost all counts, but still quite finicky and unforgiving. Were it not for that, I'd have probably ordered an $80-100 Lithium battery. But, for that kind of money, I want reliability to go with it!

So, I'm ordering a $40 ETZ10S AGM battery from a known supplier with great reviews. It's 8.6Ah, 120 CCA. Should be enough for my little 1.2 liter low-friction engine. And it weighs 6.1 pounds. So, between the battery and bracket, I'm looking at 28-29 pounds of weight reduction. That's 1.4% of the weight of the car.

[Native]

28-29 pounds of weight reduction

That will make a noticeable difference.

[twistedwankel]

That will make a noticeable difference.

If it will start repeatedly? Somehow I cannot imagine a small battery being able to survive the output of that alternator or running an AC compressor at idle to make up the difference in amps.

[nathanwilliams617]

Sorry if I missed this, but what safeguards are being put in place to prevent the engine killing down shift from happening again?

[Jamie]

Sorry if I missed this, but what safeguards are being put in place to prevent the engine killing down shift from happening again?

Co-driver's forbidden to leave second gear....