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Discussion Starter · #1 · (Edited)
So this isn't your typical build as I am a weight savings nut. But I figured I would post it here so you folks could see all the data I've collected thus far and in the future.

My No Option ST1 weighed 3190lbs in stock form with a full tank of gas.
My goal is to get this car under 3000 lbs static weight.
The car now drives and feels like a much lighter car.
Every 10 lbs of driving weight is roughly equivalent to 1 hp.

View attachment 8963

My old car for reference as to how much can be saved (2676 lbs / 291whp / 338wtq)
Project ACR-4

Focus ST Part Weights for Reference...

Weight - Part
3 - Rear Deck
4.5 - Rear Headrests x3
25.69 - Stock Rim
25 - Stock Tire
20.1 - Sparco Assetto Gara 18x8
16 - MRT Axle Back Exhaust
2.19 - Tirerack Gorilla Lugnuts x20
30 - CNT Racing Exhaust
6.35 - Gallon of Gas
10.5 - Stock Resonator
4.31 - SS Pipe Section to Replace Resonator
45.13 - Stock Exhaust
33.93 - Borla Exhaust
 

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What is the difference between the static saved and the driven saved ? Well I pretty much understand the static but I don't get what makes those number change when you are driving :)
 

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Discussion Starter · #5 ·
What is the difference between the static saved and the driven saved ? Well I pretty much understand the static but I don't get what makes those number change when you are driving :)
Some of the parts are rotational parts. When a part is rotating it creates the effect of more weight when it's moving. So for example the rims make a HUGE difference in the way the car drives and responds to input because it's rotational weight. Its the equivalent of 4 times that of just removing static weight. So just the rim change alone makes the car feel like it lost almost 90lbs while it's moving! That's the equivalent of almost 9hp!
 
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Some of the parts are rotational parts. When a part is rotating it creates the effect of more weight when it's moving. So for example the rims make a HUGE difference in the way the car drives and responds to input because it's rotational weight. Its the equivalent of 4 times that of just removing static weight. So just the rim change alone makes the car feel like it lost almost 90lbs while it's moving! That's the equivalent of almost 9hp!
Ohh I get it ! Pretty interesting !
 

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Some of the parts are rotational parts. When a part is rotating it creates the effect of more weight when it's moving. So for example the rims make a HUGE difference in the way the car drives and responds to input because it's rotational weight. Its the equivalent of 4 times that of just removing static weight. So just the rim change alone makes the car feel like it lost almost 90lbs while it's moving! That's the equivalent of almost 9hp!
A tire that weighs 1 lb less than OE makes a much bigger difference than a wheel that weighs 1 lb less, which is a much bigger difference than the lugnuts. It's called Moment of Inertia, and there is a distance component as well as a weight component in that equation, and the distance component is squared. The tire's weight is 12" from the axis of rotation and the lugnuts are 2" from the axis, so the tire is 36 times more important than the lugnuts.

These inertial forces cannot be converted to static weight by a tidy, internet-friendly factor of 4, though.

This inertial resistance also is only in effect when you are accelerating. Climbing a hill, you're still dragging the weight of the car minus your 105-ish lbs, not the so-called 180. The weight saved on the wheels makes an important difference in handling though, as it's unsprung weight. We could all use a little less of that!

Good work, though. I didn't come in here to rag on your efforts, I believe this car could easily shed some serious weight if the user could put up with some NVH. There's got to be a TON of sound deadening in here! I can't wait for a light steel single-mass flywheel to show up - it's lighter and has less inertia, and that inertial loss is multiplied by whatever gear you're in.
 

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I'm with omniphil on this obsession with weight reduction.

Aftermarket calipers and rotors for the front should be here this week. If they are as advertised I'll drop 5+ lbs on each front corner which is significant.

Note for those with a Weathertech cargo liner! You can take out the ST's carpeted trunk floor and cover the hole with your liner dropping almost 9lbs. with almost no downside.
 

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Discussion Starter · #11 ·
I could certainly take some pictures. The underside of the hood looks way better without the padding, but your only going to notice it when the hood is open. Its also easily reverse-able if you hate it, just don't break the clips. The lower grill looks a little weird if you focus on it, but its so low that its not all that noticeable. Its very hard to remove from the front tho, I took mine out when I had the fascia off as I wanted a way to stick my hand in there to be able to push the rubber flap back up if it fell down again. Plus I figure it allows a tiny bit more air flow the the stock intercooler.

Do you have any photos of the stuff you've been taking out? I'm kind of interested in the under-hood, and the front lower grille and what the car looks like without them.
 

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Discussion Starter · #12 · (Edited)
Yes, you are correct about rotational weight. The further out on the rims, the larger difference it makes. I am just using the factor of 4 for a general point of reference.

I also agree about inertial resistance only coming into play while accelerating, but that is exactly why I am doing this. To make the car accelerate, brake, and corner faster. :)

I personally am waiting for a lightweight underdrive pulley set to show up as that will wake up the top end.

A tire that weighs 1 lb less than OE makes a much bigger difference than a wheel that weighs 1 lb less, which is a much bigger difference than the lugnuts. It's called Moment of Inertia, and there is a distance component as well as a weight component in that equation, and the distance component is squared. The tire's weight is 12" from the axis of rotation and the lugnuts are 2" from the axis, so the tire is 36 times more important than the lugnuts.

These inertial forces cannot be converted to static weight by a tidy, internet-friendly factor of 4, though.

This inertial resistance also is only in effect when you are accelerating. Climbing a hill, you're still dragging the weight of the car minus your 105-ish lbs, not the so-called 180. The weight saved on the wheels makes an important difference in handling though, as it's unsprung weight. We could all use a little less of that!

Good work, though. I didn't come in here to rag on your efforts, I believe this car could easily shed some serious weight if the user could put up with some NVH. There's got to be a TON of sound deadening in here! I can't wait for a light steel single-mass flywheel to show up - it's lighter and has less inertia, and that inertial loss is multiplied by whatever gear you're in.
 

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Discussion Starter · #14 ·
How much does the weather tech liner weight? That is a really good idea actually. The only downside is that it won't fit correctly with the spare removed as there will be a large gap at the back. I was thinking of removing the carpeted floor and just replace it with some black lightweight carpet cut to size...

I'm with omniphil on this obsession with weight reduction.

Aftermarket calipers and rotors for the front should be here this week. If they are as advertised I'll drop 5+ lbs on each front corner which is significant.

Note for those with a Weathertech cargo liner! You can take out the ST's carpeted trunk floor and cover the hole with your liner dropping almost 9lbs. with almost no downside.
 

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How much does the weather tech liner weight? ...
Ahh, damn, forgot that. It weighs 3.5 lbs.

...The only downside is that it won't fit correctly with the spare removed as there will be a large gap at the back...
I'm assuming you're talking about the hole that's left when you take out the spare leaving the liner without support in that area. My plan is to just fill that void with another piece of foam.
 

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Discussion Starter · #16 ·
Its the void at the top near the seats as the stock carpeted floor isnt long enough when you remove the foam blocks.

I have a blanket in my hole. (That didn't sound right...) I use said blanket when working on the car (I lay it on the ground so I have a place to lie on) or carrying stuff in the trunk with the seats folded down to protect the interior. Plus it helps fill that void.

I may have to see what kind of carpeting I can find and cut it to fit.. Hmmm...

Ahh, damn, forgot that. It weighs 3.5 lbs.



I'm assuming you're talking about the hole that's left when you take out the spare leaving the liner without support in that area. My plan is to just fill that void with another piece of foam.
 

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the armrest is another easy removal but like most of these reductions the pros dont outweigh the cons (pun intended), and how much does a can of fix a flat weigh, if you are getting rid of the spare you have to atleast take some kind of precaution. The mustang guys live on the edge why cant we. Everyone hear has roadside assistance till 60k atleast so there is that, but if you dont have a spare your going home on the hook.

Keep the ideas coming. Cheers
 

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Front disc set came in today. Here's a picture of one of the rotors/hat/bolts on a scale. BTW, Stock rotor/hat weighs 21 lbs or so. Front rotors 001.JPG
 

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Front disc set came in today. Here's a picture of one of the rotors/hat/bolts on a scale. BTW, Stock rotor/hat weighs 21 lbs or so. View attachment 7784
I would be afraid to use those rotors. Can you say "Brake Fade City"? They have practically no venting and all that loss of heat-absorbing mass means serious overheating if there's not an offsetting uptick in ventillation. That rotor looks too narrow to vent any better than stock and that hat does not look like it's floating. If it's mounted solid to the rotor, the rotor or hat can crack at the mounting points due to uneven expansion rates between the two materials (aluminum vs. cast iron). Where did the rotors come from?
 
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