Stinger weight reduction thread

[djerickd]

Yup

 

[AWDGT2]

This entire thread confuses me as to its purpose. Remove parts of the car that weigh a pound or two? Seriously? What’s next? Wait, I know........

1. We should all go on diets to lose 5-10 pounds (some of us more maybe). But if you lose 1-2 pounds, that’s great also. Or just be sure to purge bodily contents before driving every time.
2. Remove the spare tire and all its trinkets. Better to be stranded and call roadside assistance!
3. If you don’t have kids or never have passengers, remove the rear seats!
4. Add every possible aerodynamic enhancement to cut down on wind resistance. Oh wait, that might ADD weight.
5. No floor mats. There’s gotta be at least a pound or two there!
6. Trade in for a RWD to save a few hundred pounds unless you absolutely positively live where it snows, a lot.
7. Drive naked. Clothing is strictly optional!
8. Never have more than 1/4 tank of gas. Those extra 10-12 gallons weigh a ton!
9. Drain all washer fluid. Heck, if you live where it doesn’t rain but once or twice a year, ditch the wipers!
10. This space left open for other inane additions to the list.

Says some who obviously and literally has never been to a track and raced

 

[Volfy]

Easy weight savings (Kia put unreasonably heavy wheels on this car)
After reading about people having issues with the stock brake pads, I decided to preemptively put in some z23 pads with under 300 miles on the car. I took this opportunity to weigh the passenger side rear wheel tire combo (61.4 LBS) and the drivers side front (58.6 LBS). This seemed kind of heavy so it got me thinking. The Michelin primacy tour A/S tires are not my favorite, in fact I feel they hamstring the AWD car compared to the 4S I have on my other 2 cars and offered on the Stringer in RWD.
The Stinger is my winter car, however I have a dedicated set of snow wheels and tires) so I can get away with a more aggressive tire for spring – fall.
I took a look at an “affordable” wheel tire package. I decided to go to 18” wheels for a little more sidewall, however similar weight loss can be achieved with 19’s.
I looked at the tried-and-true Einkei RPF1 in 18x9 with a 35mm offset weight: 17.3 LBS and in 18x8.5 with a 30mm offset weight: 18.3 LB (yes according to tire rack the narrower fronts are 1 lbs more).
Looking at a set of 4S tires that should work with the AWD system I went with 235/45/18, 23LBS and 265/40/18, 27 LBS
Weight savings: one rear wheel tire combo (17.3+27) =44.3 LBS
Stock combo: 61.4 LBS
Rear corner weight savings: 61.4-44.3 = 17.1LBS
One front wheel tire combo 18.3+23=41.3
Stock combo: 58.6 LBS
Front corner weight savings: 58.6-41.3=17.3
Total weight savings: 17.1+17.1+17.3+17.3=68.8LBS!
I think I will be ordering this soon
I am sorry for taking up so much room with the numbers but I didn’t believe just how much weight can be shaved!

Wheels are worth far more than their static weight. Because most of that additional weight in in the barrel (or perimeter) of the wheel, it contribute a great deal to the rotational inertia of the wheel/tire assembly. If you calculate the amount of energy required to accelerate and decelerate the additional rotation inertia, it is about twice that of the same weight but static in the chassis. So the weight you are saving with those Enkei's are worth at least twice. So instead of 68.8 lbs, it'll be more like 138 lbs.

Of course, once your car is up to cruising speed and holding steady speed, there will be no rotational inertia gain/loss, so it isn't as big a deal when you are not engaging in High Performance driving.

Still, that weight saved is also unsprung mass, which will affect your suspension action significantly. Your springs and dampers will have a much easier time controlling suspension articulation - faster reacting to road undulations and faster to recover as well, which means your tires will maintain contact with the road surface and, in turn, your effective traction will improve.

This is yet another reason why going to heavy big ass rim and fat tires don't always improve your real-world traction. It is also why such setups tend to skip side to side as the tires take turn loosing traction and momentarily sending torque to the other side, upsetting chassis in the process.

Light ALWAYS makes right.

 

[ElChanclo]

How would removing 200lbs from the rear of the stinger (trunk covers/liners, tools, donut, seats, lipo battery) effect track-day dynamics?
Setting my rear sway bar to hard (front stays on soft) is on my list of track day to-dos, though I forget why or where that was suggested.

Light ALWAYS makes right.

I got to ride a lap with some crazy kid in a tracked out miata, he was on the gas well into my would-be braking zones, sliding all through the turns. He was ecstatic when he looked at the track data and saw a new personal best lap time. With his 1900lb car, I swear my 200lb balance weight deserved some credit .

 

[Volfy]

How would removing 200lbs from the rear of the stinger (trunk covers/liners, tools, donut, seats, lipo battery) effect track-day dynamics?

Easiest way to think of it is by the fact that reducing substantial weight from one end of the vehicle effectively increases the spring/damping rates on that end. This is because the coil springs, anti-roll bars, and dampers all now have an easier job at controlling wheel articulation as well as body mass movement.

A good thought experiment would be to imagine a car with zero body (sprung) mass and zero unsprung mass. In that scenario, even what would otherwise be the softest springs are now effectively infinitely stiff, because the body mass and unsprung weight take zero force to move. That's clearly impossible, and reality, of course, lives on a grey scale somewhere above zero mass. However, that trend is proportional to how much that mass is.

The other important dynamic is mass centralization, which I touched on recently in another thread. Antigravity batteries. You probably already read it.

Setting my rear sway bar to hard (front stays on soft) is on my list of track day to-dos, though I forget why or where that was suggested.

I'm afraid that was probably me a while back. To be quite honest, this is why I hesitate to answer when folks ask what I have my suspension is set to. Things like this gets taken literally and subsequently requoted without originally context. That can be rather dangerous. Suspension tuning is a balancing act. What works well in one setup might not be appropriate in another. FWIW, here's the original context: that was when I was still on Eibach springs. Since the stock dampers were non-adjustable, as were the spring rates and ride height, anti-roll bar was the only means, with which I can influence the cornering attitude of my car at the time (other than tire pressure). Now that I am on Riaction coilovers, I have set my anti-roll bars back to even both front and rear.

Now, Riaction rear spring rate is 10k, so not overly stiff. It is probably still relatively safe to tune my chassis by increasing the rear anti-roll bar stiffness relative to the front, if the car is still understeering substantially. This may not apply to other coilovers. Some of them have much stiffer rear spring rate (like 14k) relative to their front (7k?). In a set up like that, I would be very very careful about stiffening the rear end any further.

 

[Thomby]

Does anyone have pre- and post-reduction weight comparisons? Weight reduction usually runs into diminishing returns pretty quickly, so it's hard to pull big totals out vs. starting with a lighter car, but I'm curious what people have accomplished.

If we take these as our starting points:
- 4cyl RWD = 3600 lbs
- 4cyl AWD/6cyl RWD = 3800 lbs
- 6cyl AWD = 4000 lbs

I'd be curious if there are any V6s running around under 3500 lbs, for instance.

 

[djerickd]

i want to weigh my car. i’ve done lightweight wheels, water pump pulley, brake rotors, and battery.

i wish DSS would make a carbon or aluminum driveshaft for our cars!

 

[Volfy]

I definitely need to weigh mine. The published curb weight for the 2.5T is all over the place. I've seen it anywhere from 3611, to 3792, to 3814 lbs. I would think it is heavier than the 2.0T, so the 3611 number is likely incorrect and just some lazy editors copying old base model specs from the earlier model years.

I may have a way to do it, albeit weighing each corner separately. Actually better and more telling that way.

BTW, I'm almost certain our G70 has an aluminum hood, since magnet doesn't stick to it. Stinger's hood is steel.

 

[Ohiocruiser]

My GT AWD is 350 -400 lbs lighter than stock by now. Also you have to remember that gt2 is heavier than gt1. And gt1 is heavier than gt.

 

[Ohiocruiser]

i want to weigh my car. i’ve done lightweight wheels, water pump pulley, brake rotors, and battery.

i wish DSS would make a carbon or aluminum driveshaft for our cars!

They can build it, if you can get the measurements.

 

[ElChanclo]

My GT AWD is 350 -400 lbs lighter than stock by now. Also you have to remember that gt2 is heavier than gt1. And gt1 is heavier than gt.

I'd love to see the list of weight reduction mods you've made. I'm looking for ideas myself.

 

[Snicklefritz]

My GT AWD is 350 -400 lbs lighter than stock by now. Also you have to remember that gt2 is heavier than gt1. And gt1 is heavier than gt.

Really? I thought the weight differences were almost entirely in sunroof and AWD components. What else? I never did find a weight difference between sunroof and steel roof though. Guesses, but no hard number. As I recall, the added AWD is another almost 200 lbs.

 

[Ohiocruiser]

I'd love to see the list of weight reduction mods you've made. I'm looking for ideas myself.

Sure. Wheels-40, brake rotors-15, spare with all tools and shelf-50, reat seat-50, battery-40, rear door panels and speakers-20, front seats-90, both subwoofers-10, carbon hood with front crash bar-30, all those noise dampeners with a lot of aluminium and titanium bolts gotta be at least-30lbs. Probably missing some other small parts. But you get an idea.

 

[Ohiocruiser]

Really? I thought the weight differences were almost entirely in sunroof and AWD components. What else? I never did find a weight difference between sunroof and steel roof though. Guesses, but no hard number. As I recall, the added AWD is another almost 200 lbs.

the difference probably is not that big. But sunroof would add around 40lbs. I know the front seats are 20lbs heavier than gt ones. 19 inch wheels will add another 10-15 lbs vs 18 inch on gt model. Electronic steering column and rear lift gate mechanism gotta be heavier than manual one. Just the stuff that comes to my head. But I wouldn't be surprised if gt2 is ~100lbs heavier than gt.

 

[Volfy]

Glass is much heavier than steel panel. I don't doubt that has to do the Stinger/G70 owners that had the sunroof spontaneous combust while driving. Kia/Genesis probably tried to save every last Oz. of weight by thinning the glass as much as they can get away with. "Acceptable casualty" might be part of that calculation, unfortunately.

Besides, the roof cage accounts for a very substantial part of a sedan's torsional rigidity. So, when you cut big holes in the roof panel, you are gonna have to add structural reinforcement to make up the loss in that rigidity. That adds weight too. This is especially critical for a fastback already with a huge opening in the back and no rear bulkhead. For a traditional sedan with nice beefy cross ties behind the rear seat, it's not quite as bad.

 

[Volfy]

Sure. Wheels-40, brake rotors-15, spare with all tools and shelf-50, reat seat-50, battery-40, rear door panels and speakers-20, front seats-90, both subwoofers-10, carbon hood with front crash bar-30, all those noise dampeners with a lot of aluminium and titanium bolts gotta be at least-30lbs. Probably missing some other small parts. But you get an idea.

Dang! That is hardcore.

 

[ElChanclo]

Sure. Wheels-40, brake rotors-15, spare with all tools and shelf-50, reat seat-50, battery-40, rear door panels and speakers-20, front seats-90, both subwoofers-10, carbon hood with front crash bar-30, all those noise dampeners with a lot of aluminium and titanium bolts gotta be at least-30lbs. Probably missing some other small parts. But you get an idea.

Damn! You'll be getting a visit from the men in lab coats soon.

I looked at the G70 Al crash bar, looks identical, was it an easy swap? Where did you source it, and will you do the rear as well?

I'm curious how much you can feel that kind of weight loss, but you'll have to pry my cooled seats from my cold dead hands!

 

[Ohiocruiser]

Dang! That is hardcore.

Rear seat belts. Aluminum brace bars instead of steel stock ones. Secondary downpipes. Now, that's hardcore

 

[Volfy]

Rear seat belts. Aluminum brace bars instead of steel stock ones. Now, that's hardcore

Which brace bars?

 

[ElChanclo]

Suspension tuning chartView attachment 86020

Very handy! I have mostly understeer, but all my weight reduction is at the rear, guess I'll find out what that does when I'm on track. Here's hoping turning off TCS helps bring the rear out.