Just a thought... What could the factory have done to lighten then car?

[Ultramaroon]

Originally Posted by babydriver

Sometimes it's helpful to me to simplify the problem somewhat.

Imagine that we have a coil spring connecting two weights, one small one on the bottom (the unsprung weight) and one very large one above the coil spring (the sprung weight). Any change in the sprung weight will either compress the coil spring more (if heavier) or less (if lighter). For the purpose of this thought experiment, we will ignore any side to side motion that may be possible; only up and down motion is "allowed".

True but the typical 1/4 vehicle model also takes into account tire spring rate between the unsprung mass and the road surface (input signal). It gets complicated fast. We can't simplify this problem any more that that standard model because any further simplification would result in junk answers, ie. Garbage-in-garbage-out.

Originally Posted by babydriver

What complicates matters further is that the lower "unsprung" weight also moves. As force is applied to it in an upward direction, the spring compresses and rebounds. A downward direction will cause stretching and then rebounding. At some critical combination of rate and weight, the unsprung weight will come into resonance with the spring's rate, allowing the greatest motion with the least effort. However, this is also the point at which the entire assembly wants to continue to oscillate at the same speed as long as there is additional energy put into the system. The shock absorber (on the car) is there to reduce this resonance (i.e. bouncing).

The question is: If the damped resonance is something that is desirable or undesirable?

The system is already tuned way lower than what you're describing, somewhere between 1-2 Hz, I think. At most 8 Hz for super racecar.

Resonance is good for musical instruments but way bad in this case.

[totopo]

Originally Posted by Ultramaroon

Isn't wheel rate simply a way to combine spring rate with the moment arm of the suspension? I don't understand how mass would figure into that.

I couldn't find my vehicle dynamics book last night. @babydriver's question is interesting and I'm taking ownership. Thank God brick & mortar libraries still exist.

You are correct. I am mixing up wheel rate and suspension frequency. Time to hit the books again

I was talking about frequencies Mostly I think? haha, though wheel rate is better than spring strength.


edit: what the heck am I thinking? I think I have something majorly wrong in what I thought I knew about suspension. ignore half of what I say please, hahaha.

[Ultramaroon]

We're way off topic in this thread. Should we start a new one? @himbo?

[Ultramaroon]

Originally Posted by strat61caster

But of course I wouldn't mind the lesson, my class did not go that in depth.

I studied this a little because of my FSAE team. That's all. My vibrations analysis prof. and I really bonded. I'm no genius but I innately consider the acoustical implications in just about everything I see.

Keep me honest. That's the most important thing.

edit: btw, I reread your first post with this in mind.

Originally Posted by strat61caster

However it would not be detrimental to comfort and I pointed it out explicitly because it was the opposite of baby's assumption.

The victorylibrary article's statement about lowering spring rate makes more sense if considering the primary goal to be comfort. It's not that you need to lower the wheel rate accordingly, it's that you can get away with lowering it to improve comfort.

[Koa]

Originally Posted by Bristecom

As with any car, there can be issues but my Eclipse is nearly 17 years old, always sat outside, dealt with salty winter roads, and barely got washed, and I still don't really see much rust under it or anywhere. That's pretty impressive to me. But I have seen pictures of some that are badly rusted. I'm not sure what they're doing to get that kind of rust. Maybe they park it in a swamp? But even so, Mitsubishi has had a 10 year rust warranty for a long time. So those people still probably could have got that taken care of.

But yeah, I'm not claiming Mitsu is better or anything; it's just that I don't absolutely have to buy a new car right now. I will get the FR-S soon enough and I was considering getting it when the Monograms came out but decided to wait it out a bit longer.

It's a design flaw with a large number of factory year versions of their flagship performance market offering is what I'm trying to underline here.

[himbo]

Originally Posted by Ultramaroon

We're way off topic in this thread. Should we start a new one? @himbo?

Nah. I'm not a huge stickler for these things, I'm all about a good flow of ideas. Mostly, I wanted to see what people would have done if they were designing the car within the perimeters it was built around. The perimeters being cost, safety, etc. Sometimes these types of perimeters promote really innovative and creative ideas.

[zman]

Stickers as headlights 😃


Sent from my iPhone using Tapatalk

[BRZtoni]

remove passenger seat and rear seats.

[whiplash]

No rear seats would probably have been the best. Spare tires can be handy lol

[strat61caster]

Originally Posted by CatDaddysBBQ

I'd say the easiest way would be to have a lightweight battery, no rear seat (parcel shelf and a wall to block off the trunk) and ditch the spare for a plug/compressor kit. Ditch the Sound tube while they're at it as well.

That'd save 100lbs or so, and the added cost of the fancy battery would be offset by the cheaper rear seat area option and the fill kit vs a wheel/tire/jack/etc combo.

Originally Posted by whiplash

No rear seats would probably have been the best. Spare tires can be handy lol

Rear seat delete is estimated to be ~25 lbs.
link 1 link 2
Spare tire is about the same at ~25 lbs.
http://www.ft86club.com/forums/showthread.php?t=7881

The OEM battery weighs ~30 lbs and a super light replacement (<5 lbs.) is going to cost ~$500 or more. (See above link for the tire)

At most you're looking at 75 lbs for all those things, maybe 80 since the design engineers can likely make other savings with those changes that the consumer can't by ripping them out (i.e. no well in the trunk = less sheet metal, remove hardware there for mounting tire).

There's potential for an OEM GT3 RS like version coming in under 2,600 lbs wet (there's at least one member who's down to ~2,400 lbs with fuel) but there's a small cross section of people who want that and would pay for it instead of living with the weight and luxuries (A/C, NVH, Radio) or the people who would do it themselves to a more extreme degree. Given how expensive the special editions have been I think they'd struggle to keep the cost under $30k as it would take significant changes in production to complete instead of a new color and some bits slapped on after the fact.

[CatDaddysBBQ]

Originally Posted by strat61caster

The OEM battery weighs ~30 lbs and a super light replacement (<5 lbs.) is going to cost ~$500 or more. (See above link for the tire)

I've seen the small battery that replaces the oem one (that the electric supercharger setup uses) and it's way less money than 500. It's like 130 or less. Huge difference.

[TylerLieberman]

You could have put down the fork and went running...

[strat61caster]

Originally Posted by CatDaddysBBQ

I've seen the small battery that replaces the oem one (that the electric supercharger setup uses) and it's way less money than 500. It's like 130 or less. Huge difference.

Yup you're right, I just pulled the one from the vendor, here's a Shorai battery for a bike at $185 that some guys have used. The SuperB I was thinking of seems to be for heavier duty applications, with this Shorai it sounds like there is a risk that it won't keep up with some rigorous demands but if you're going for all out performance then the compromise is worth it.

[ame="http://www.amazon.com/Shorai-LFX-Battery-LFX21A6-BS12-Black/dp/B0088JGUTA"]Amazon.com: Shorai LFX Battery - LFX21A6-BS12/Black: Automotive[/ame]

http://www.ft86club.com/forums/showt...=42284&page=28

[Anthony]

I think this about covers it:

Originally Posted by DAEMANO

Remove and replace spare tire + tools with can of fix-a-flat - 30-40 lbs (depending on laws)
Smaller washer fluid reservoir and less fluid - 2-4 lbs (est)
Single exit exhaust and muffler - 20 lbs (Tanabe concept G as benchmark)
Manual on CDROM - 1 lbs
Lighter weight front seats - 14 lbs (est)
Delete front strut bracing - 3 lbs
Remove all sound dampening tiles - 3 lbs
Smaller door speakers - 2 lbs
Sound tube delete - 3-4 lbs

My first thoughts were single exit exhaust, and that surely they could've made much lighter seats at the same price point. Hell, the single exit exhaust would've saved money, so maybe they could've taken the savings and invested them into making the wheels a pound lighter or something. Maaaybe a one piece driveshaft? Which again seems like it would save money.

Originally Posted by Ultramaroon

Haha... dunno but I wonder if there's a per-thread quota on saying "bullshit" legitimately, or otherwise.

Turns out, there is. No one talks about it though. It's actually a minimum requirement, and so far you're the only member on this entire website that's even attempting to pull his/her own weight. So... by my calculations, you're winning.

Oh. And I also just realized...