I know Cortc and others have made a specific effort to reduce unsprung and rotational weight for performance gains. I'm making this a general post as a request for those who have made these kinds of mods, if they could post what they've done, how much weight was saved, what are the parts replaced, where are they available, etc.

It would be a great help to know what actually works, how well, etc. from those who've actually done the mods.

TIA!

 

I would like to know as well. I think that the options are light polycarbonate windows, removing some stuff in the trunk, removing the AC, lighter flywheel, etc.

 

Rotary Extreme has a Carbon Fiber hood that is supposed to take about 10 lbs. off the front (even though the stock hood is aluminum). This should help because of the very slight front weight bias of the car. Also there was another poster who just had the Amuse titanium exhaust installed. That is big $$$ but the weight of titanium is usually about 1/3 to 1/4 of the stainless steel versions.

 

I would start with wheels. SSR Comps would shave a bunch of weight on the car. If someone make OEM spec brake rotors with aluminum hats, that would help a bunch too. I haven't seen them, but have been looking a bit.

 

In order to keep this thread organized, there is unsprung rotational weight (wheels, lugs nuts and bolts, break rotors, tires, TPMS, valve caps), unsprung stationary weight (break caliperas and pads, a percentage of the a-arm, msc. nuts and bolts), sprung rotational weight (pullys, flywheel, driveshaft, all the nuts and bolts on those, the rotors, the e-shaft, parts of the tranny, and probably a ton of things I'm not thinking of), and sprung stationary weight (everything else).

As a general rule, removing unsprung weight is more effective than sprung weight. As a general rule, I think, the 1/15 unsprung/sprung ratio is used. However, removing sprung rotational weight (weight the engine has to turn) frees up power to the wheels (which is why, AFAIK, getting a lighter flywheel is better than getting lighter wheels when it comes to power) and offers a (mostly insignificant) loss in overall sprung weight. Likewise, removing rotational unsprung weight shows better effects than reducing stationary unsprung weight.

So, what I am saying (and as far as I understand all of this), is that a CF hood is not the same as lighter calipers is not the same as lighter wheels is not the same as a lighter flywheel.

So, lets categorize as we go. Ole Spiff, it's your job to keep a list in your top post (use edit to add new items to the list). In order for this thread to be useful, only post data that you have all the answers to. We need to know 1) The product, 2) How much it weighs, 3) what type of weight it is, 4) how much stock weighs if it isn't already listed, 5) total savings, 6) Multiply how many are on the vehicle. You should probably also post how it makes the car feel afterwards if you know from first hand experience.

So, for example SSR Comps I would post:
Then Ole Spiff can add it to the list in this fashion
I think this thread could offer tons of great information, but

1) We don't need guesses. We need REAL values. If it isn't common knowledge or independent research, then post a link to where you got the info.
2) The list needs to be updated and kept in order.
3) This is for REAL items, whether they are on the market (like the SSR comps) or being independently researched (like Cortec's titanium lugs). Don't list speculative items, because they won't help us gather real information, which will make this thread useless.

If all of these are fulfilled, then I think this thread might be useful. Otherwise it will end up being a pain in the *** to use for any real information. So, assuming Ole Spiff agrees with me (which he can let us know below) and is willing to keep up with this thread, lets try to follow this order.

Any suggested changes to this structure are open for suggestion. Is this method cool with everyone?

 

www.importfan.com has a really good price on carbon fiber bits. You can get the four doors, hood, and trunk lid in carbon fiber for $3,500. The doors should make a huge difference since they are on the very outside edge of he vehicle.

 

Well I'm okay with keeping it organized, but it doesn't appear to have generated much response or interest. Bummer

 

its hard to reduce the weight much without starting to lose utility and/or safety. if you stripped out the interior and removed stuff like the AC, etc the car would be lots lighter, but also will not much of a car. i did this to my rx7, and used it as a street/track car, but it sure wasnt fun on the street anymore. noisy, stiff, hard to get in and out of.

would be a great motor in a 1500lb car though!

james

 

Hope isn't lost. We'll just have to start by looking up numbers from previous posts. Maybe more people will get into it after we have some info here.

 

Any idea how much weight reduction no AC would have? I never run it anyway...thats what the sunroof and 80 mph is for :D How involved would it be?

Besides the weight reduction, wouldn't removing the AC also reduce parasitic loss?

Oh, and incidentally just got a speeding ticket. Hrmph.

 

According to: https://www.rx8club.com/showthread.p...414#post497414

One stock 18 inch wheel, unsprung rotational, 21.5lbs, 0lbs, *4, (no changes)
One stock SSR "Type-C" wheel, unsprung rotational, 16.5lbs, 5lbs, *4, (a lot more nimble, according to IZoomZoomI)

You can add that to the list.

 

Ole Spiff, add these to the list:

Rotational Unsprung Weight List (Product, weight, savings over stock, number on vehicle, perceived difference)
---------------------------------------
*One Stock Lug Bolt,2.1oz,0oz,*20, (no changes)
*One T4 Titanium Lug Bolt,.96oz,1.14oz,*20 (according to cortc "there was a difference you could feel")

*Taken from Cortc's Titanium Lug Project: https://www.rx8club.com/series-i-wheels-tires-brakes-suspension-55/titanium-wheel-lug-project-32091/

By the way, I'm trying to make note of the lightest parts that I can find. While I like the Volk TE37s, they weigh a few pounds more than the SSr Competitions, so I'm not posting figures.

Also, Cortc installed lighter lug nuts, but he never posted weights. He also made the light-weight pulleys, but never posted the final weight of the stock OR the replacements.

 

Sprung Rotational (product,weight,savings,total needed, changes)
-----------------
One Stock Flywheel, 16.8 lbs, 0, *1, (No Change)
One Racing Beat Flywheel, 12 lbs, 4.8 lbs, *1, (Consensus: Better response, more HP freed up)

http://www.racingbeat.com/resultset....rtNumber=11468

 

robertdot, reducing mass in the driveline doesn't "free up" any power, it's just less mass to drive like anywhere else on the car. reducing weight at the wheels (pound for pound) will actually be more effective in helping acceleration, even though they turn slower than the motor does until you hit 6th gear, 'cause they have a bigger diameter and more weight around the edge blah blah, not to forget the help they give to suspending the car more effectively. changing out the flywheel has the biggest effect on the driveability of the engine.
where you see the "increase in power" (which leads retard FWD ricers to have lighter wheels on the fronts and big 20" rims on the back) is on dynomometers that measure the acceleration of a drum with a known mass, the dyno doesn't know how much all the driveline stuff on your car weighs, so that's why the rating is lower than if you went to a brake-type dyno, and also why you get these pretty huge "power gains" from reducing mass in the driveline.

 

What I think I want to do is create a list of the stock weights of items so we have a baseline for comparison. I'll need the stock weights of the factory 18" rims, tires, brake rotors, calipers, lug nuts, engine pulleys, flywheel, muffler, and anything else anyone can think of. Once I can post that we'll have something useful to help us determine the true weight savings of a mod.

If anyone has any of these stock item weights please post them!

Thanks

 

Ok, did some more calculations on weight reduction including the light forged lug nuts I have on the car...

Stock lug nut 2oz (2x5=10oz per corner) 10x4=40oz or 2.5lbs...
Forged lug nuts 1oz (1x5=5oz per corner) 5x4=20oz or 1.25lbs...

That is another 1 1/4 lbs savings in unsprung rotating weight, including the 1 1/2 lbs savings of the titanium lug bolts that is a total of 2 3/4 lbs...

When rotating at high speed that weight increases by a factor of 7 or 19.25lbs...

I took the car out for a ride with the stock lugs and bolts before doing the install and then with the titanium lug bolts and lightweight forged lug nuts and there was a difference you could feel... With the new wheels and two piece brake rotors this should really lighten things up.

So for those that ask, does reduced unsprung weight or rotating unsprung weight reduction make a difference?; the answer is yes...

 

The new pulleys should be here soon and I wil post pictures and weights, then some before and after dyno runs...

 

I'll give this a try:

This is a pdf file so hopefully it will be readable by everyone.

 

how much weight would the carbon fiber doors, hood, trunk deck save?

 

Unless this is going to be a race-car or you are will be installing a full roll cage I would not replace the doors as they are an integral part of the cars crash safety systems...

 

Yeah. So, correct me again if I am wrong: If I put a lighter flywheel on my car, it allows the power that was wasted spinning the heavier flywheel to reach the rear wheels. It doesn't create more horsepower like FI does. It just allows more to trickle down to the wheels (aka frees it up more HP to the wheels, aka RWHP, different from BHP which I wasn't talking about). If I am wrong here, then 1) so are alot of other people in other threads (or at least I am wrong in my understanding of what they were saying) and 2) I'm going to be asking you a ton of questions to get my story straight.

In the previous post that you are commenting on, I was trying to get all the people that were going to say "just pull out your interior, AC, HU, engine, and there you go, a really light car" to not say that. I didn't want this thread to turn into another garbage weight reduction thread where people start talking about losing weight and going on low carb diets. I was trying to offer a quick and dirty explanation to make this a valid "scientific" thread and justify using different categories.

Granted, the motor DOES actually directly turn the rear wheels (which I try to ignore in these general-idea posts), so changing the setup to a lighter rear wheel (with stock fronts) will be effective similar to a flywheel; will lighter front wheels with stock rear wheels have the same effect on RWHP as stock front and lighter rear wheels? It shouldn't have as dramatic of an effect (at least in my head and my understanding) because it isn't putting spinning drag on the engine (e.g. it isn't the difference in changing a stock flywheel to a lighter flywheel). Am I wrong here?

I don't want this to turn into a debate over different types of weight and how they effect the car. You and I have hijacked threads before, but I'm trying to keep this one on topic I'll admit I'm wrong if I am, and I will PM you with all my questions.

 

From Cortc

Stock Alternator Pully> 5.8oz
Stock Water Pump Pully> 10.9oz
Stock Timing Ring> 5.5oz
Stock Water/Alt Rear Crank Pully> 11oz
Stock A/C Front Pully> 1lb 2oz
Stock Crank Hub> 15.6oz

Total Stock Crank Pulley - Hub & Nuts/Bolts> 2.156lbs

Total All Stock Pulleys - Hub & Nuts/Bolts> 3.2lbs

Total All Stock Pulleys + Hub - Nuts/Bolts> 4.175lbs

Total All Stock Pulleys/Hub/Nuts & Bolts> 4.345lbs

Stock Water Pump Bolts> .175oz x 3 = .525oz
TI Water Punp Bolts> .075oz x 3 = .225oz

Stock Hub Bolts> .325oz x 4 = 1.3oz
TI Hub Bolts> .125oz x 4 = .5oz

Stock Alt Nut> .9oz x 1 = .9oz
TI Alt Nut> .5oz x 1 = .5oz

Total All Stock Nuts & Bolts> 2.725oz

Total All TI Nuts & Bolts> 1.225oz

 

Here's the latest chart with new info courtesy of Cortc!

 

nah, it's just straight "how much mass are you pushing?". power to weight. a lot more energy is being stored in the spinning masses of the car (drive train components, wheels, whatever whatever) propotionately than the stuff that's just being accelerated linearly. so by reducing the weight of the spinning stuff, to get it to a certain speed requires less energy thus leaving you with "more" energy to accelerate the rest of the stuff getting you where you're going faster. the "more power to the wheels" is just an illusion created by the dyno. but yes, exactly the same idea.

 

I get what you are saying.

I'm comparing it to solid matter. It's an illusion created by the composition of matter that makes us think it is solid, when it is really 90% empty space (or something like this). Sometimes we are forced to operate under illusions.