Even thinner paint?

Within reason... I was responding to those who were saying that they can go much faster by taking a crap or working out a bit. Of course a whole nother body's worth of weight will make a difference.

Yeah... I'm a weird lurker who's been around since 2011/2012. But I might just give up on this forum because lately it's become a haven for trolls. It used to be about interesting in-depth discussions but now it seems like everyone just wants to try and troll for laughs since they probably don't have any real life friends and it makes them feel special when they get a "Thanks." As far as I could tell, the OP was asking a serious question and when I give him a serious response, I get criticized for it?

If you've been around for as long as I have, you would know why I haven't bought an FR-S yet and my thoughts on it as I have posted about it many times.

It's nice to get the gears turning, which is why I posed the question.

Thinner you say?

You're probably not going to get lighter wheels from a factory on a car at this price point. If you saw what Enkei/oz/bbs do when manufacturing theirs, you'd know why they cost what they do. It's a much more time-intensive process that's not suited well to mass production on Subaru/Toyota's level, which is why you usually only see lightweight performance oriented wheels on much more expensive cars produced in low-volume. Not on the same level of difficulty as something like carbon fiber/composite brake discs, but same idea.

The stock wheels are designed for minimal machining, cost, and production time.

The single exit exhaust would be nice, and far more efficient, but that's dictated by market studies and focus groups saying people want dual exit exhausts even when they're entirely unnecessary on a 2.0L 4-banger.

I would have liked to see them save some weight on rotational mass like the driveshaft and elsewhere as well. For a lightweight car the sound tube was just pointless, I'm glad I took it out.

There's an awesome weight thread somewhere, where pretty much everything unnecessary or replaceable stock parts was weighed and tallied. If you want too cut weight, start there. It's not hard to cut a lot without buying anything, and without spending a lot either.

Once you get into lighter weight performance parts your wallet is going to take a hit unless you're replacing something that already broke.

Bristecom tldr: He has two whole test drives under his belt, calls the car disappointing, says his Mitsubishi is better and is holding out for a faster version.

Maybe they should make a higher end model with stuff like forged wheels, forged aluminum links, and Brembo brakes for those who value that sort of thing. Aftermarket is not always the most reliable or cost effective way of going about that stuff.

The dual exhaust is likely a consequence of needing a bigger muffler to meet stricter noise ordinances. But I would love to see them design a lighter and straighter exhaust that could accommodate a real rear diffuser for minimal lift.

Three test drives. ;)

I did not say the car was disappointing. I love it. That's why I'm still here. The main thing that disappointed me was the power band and I am still somewhat concerned with reliability. If I buy a new car, I want to try to avoid the dealership at all costs. So I will get one eventually but for now I'm sticking with my Mitsubishis.

At least you've been around long enough to know me strat. :D

Stock wheels are made by Enkei already (well, the STI wheels are... I bet the normal ones are too as Enkei is an OEM supplier).


Driveshaft is what it needs to be for multiple reasons that I'm really not in the mood to get into. It's not a great place to cut weight.


Cast/forged aluminum control arms would have probably cut weight quite a bit too, but it depends on the type of steel they used on the factory parts.


I'm sure some of the FI guys wish they added some weight in the transmission and gave us an overall stronger trans...

On second read I can see that. Guess a little context woudn't hurt. :D

Edit: Yeah, no. You went way into detail basically saying it was worthless to reduce mass unless it was up high, at the ends, or unsprung. I'll stick with B.S. No offense.

Wheels are certainly good for OEM!
I put on RPF1's and don't think I saved much at all.

My point was that it is the least important area of weight as it the most centrally located and not a part of unsprung weight or rotational mass. I didn't say it didn't matter though. But to try to lose enough body mass for a performance gain is silly unless you are overweight/obese to begin with. Then by all means, try to lose weight as there are many benefits in life by doing that. But this thread was asking about how they could have designed the car to have less weight - so that does not include the driver or passengers as they are a variable the designers/manufacturers can't really control unless they refuse selling the car to anyone over a certain weight.

I see your point and true, you never said it didn't matter. And my bringing in driver weight was off topic.

Points well taken. My interpretation and response was pretty coarse. Thanks for your patience - really. :cheers:

drives a mitsu... concerned with reliability..

yea, because being around "longer" than contributing "quality" is the name of the game right? ;)

Between my wife and I we had 7 Mitsus over a 20 year period and other than my Talon (I consider it a Mitsu) that just died of old age we never once had to have one repaired. Not so much as a light bulb required work!

Since the wheel is part of the sprung weight of the suspension, it seems to me that changing the mass of the wheel+tire would require changing the factory springs (and their rate) also. Less mass in the wheels will result in a lack of full compression of the springs and I suspect that the ride will become rather stiff and paradoxically you could lose some control and contact with the road. Am I misunderstanding something here?

Info inbound.

http://www.formula1-dictionary.net/unsprung_weight.html

You'd end up with a softer suspension as the unsprung assembly that creates traction with the ground requires less force to 'follow' the road.


http://victorylibrary.com/mopar/sprung-c.htm
Basically if you envision the body of the car sitting still and it's traveling over a bumpy road the wheels and suspension work like mad to stay in contact with the road, if the wheels and suspension are heavy they react slowly because they have high inertia and require a lot of force to change direction so you would need stiff suspension to 'push' them into the ground while simultaneously being soft enough to 'absorb' the rises in elevation, a tough compromise. With a lighter setup there's less inertia, the wheels 'track' the road with less effort, increasing traction overall. That's a very simplified explanation but the fundamentals don't change when talking about an F1 car or an off-road buggy.

Image for funsies:
http://mscdrupal.mscsoftwarecorpo.ne...spension_0.gif

:cheers:

Thanks! BTW, I meant to say "unsprung" rather than "sprung" earlier. :bonk: The above underlined sentence was effectively my point; lighter wheels need lighter springs too.

Yeah, I bought the Evo X and fourth gen Eclipse right when they were released and they were faultless for all the years I had them (6+). The ones who claim poor reliability are generally those who mod the heck out of them (add 200+ hp to stock engine) and try to blame the car itself for poor reliability. But with that said, my DD, the Eclipse GSX is getting tired at nearly 200k miles so I will inevitably have to replace it and the FR-S is by far my favorite prospect for that. Also, now that I live in Florida, I don't need AWD so much. :P

I was referring to this, among other issues:

https://www.google.com/search?q=rust...oe=&gws_rd=ssl

but this doesn't apply to your sexy X

Fair disclaimer: I don't believe Subaru performance platforms are more reliable than Mitsu's performance offerings :D

Obviously I am a Mitsu fan but found the FRS blows the Eclipse out of the water in every aspect even without the AWD.

I'm at work so no time to actually review but I think the article which makes that statement is incorrect.
http://victorylibrary.com/mopar/sprung-c.htm

All other parameters being equal, reduced unsprung mass does not require reduced spring rate. Actually, reduced spring rate in both cases lowers the resonant frequency of the suspension system which negatively affects the system's ability to recover quickly from a perturbation (bump). Traction is lost during that increased time required for the wheel to reverse direction and regain full contact with the road surface.

I'll wait until this evening to find out how wrong I am but for now, I'm going to stick it out there for consideration.

Of course there is another factor at work and that is damping (the shock absorber). The damping would be enough to eliminate any oscillations from the lower rate (as you say, a lower resonant frequency too). I'm assuming though that there has to be an optimum spring rate for each unsprung mass designed to achieve certain goals of handling and traction, otherwise all car manufacturer would use the same springs. Toyota went to the trouble to change the spring rates on the 2015 FR-S compared to the two previous years to improve handling. They must have had their reasons.

I'll look forward to your later post, Ultramarine.

Springs absorb bumps and shocks control springs and body motion.

Spring rates are mostly meaningless to talk about from a modeling perspective because of differing motion ratios for different suspensions and makes. Resonant frequency/wheel rate is the real measurement. Lighter unsprung weight is basically almost linear w increasing the wheel rate.

10% less unsprung weight is basically similar to 10% stiffer springs in terms of wheel rate. Ie if your wheel rate was 1.5, now it is 1.65

Generally lower wheel rates (like 1) makes for more comfort and better traction, but needs more suspension travel. So wheel rates are mostly governed by bump travel and expected hauling weight of the car. Most cars have rates around 1.2 or so and end up needing at least like 6 inches bump travel Minimum. Most non-aero driven pure track cars aim for 3 inches bump travel which ends up at wheel rates around 2.5. sports cars end up in the middle.

roll angle is harmless in steady state but bad in transitions and makes drivers unhappy if there is too little or too much. Anti roll bars are to control roll angles.

shocks control body motion at low shock speeds and control for bumps at high shock speeds.

Edit: the wheels also count for rotational mass, which does help acceleration and braking


second edit: I think I have something wrong with the unsprung weight. Please ignore the wrong half of this post. which half is wrong I'm not quite sure. ahaha

Damn poor Ubersuber he would have loved this!!!!!
You would all be wrong of course but he would still have loved this.

Pretty much except for a few of things - mid to high range torque, the raw feel/feedback of an old sports car, and traction (although sometimes you don't want this :burnrubber:)

But don't worry, I'll be moving to an FR-S soon enough, even if they don't improve the engine at all (as much as I would like them to).

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.

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.

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're absolutely right that lowering unsprung mass does not 'require' lowering spring rate and doing so would likely be detrimental to performance.

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

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

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".

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?

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.

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.

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

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.

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

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. :D

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

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.

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.

Stickers as headlights 😃


Sent from my iPhone using Tapatalk

remove passenger seat and rear seats.

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.