I am curious what can be shed weight wise.

How much can i save by taking out the stock jack stuff and the stock spare. curious because the family has a towing company so i dont need all that crap. what does it weigh.

thomas

 

there are many threads about this, you should search.

 

Yep.

Lucky you I had these two pages bookmarked:

https://www.rx7club.com/forum/showth...hreadid=128497
http://www.mantissaconsulting.com/et...eight_data.htm

 

congratulations on addressing the often overlooked side of the power to weight equation.

mazda tasked 2 teams with the single job of taking weight out of the fd and gave them a year. neither team could talk to the other team during that year.

they did a great job and light weight is one of the defining aspects of the fd.

being human they made a few mistakes which is to be expected... for instance look at the swiss cheese front swaybar mounting bracket. in fact you should look at it often as it is prone to cracking from all the holes drilled into it. i run an aftermarket replacement.

and after shortening the spark plug wires to shave weight they bolt on power steering? i consider manual steering to be my favorite mod. hello road feel... goodby video game steering. goodby 20-30 pounds of front weight.

but i digress

the purpose of my post re weight reduction is to emphasize that what you really want to do besides reduce weight is to increase rear weight and decrease front weight. move the battery to behind the pass seat, get everything out of the engine compartment etc etc.

i have a set of scales and my car which is a combo street, road racing track car runs 52% rear weight.

good luck,

howard coleman

 

Please don't flame as i'm always learning more, but shouldn't we try to get the car at a 50/50 (or as close to) weight balance when moving, therefore try to get a 53% front bias? As the car accelerates wight shifts. . . well im sure you know the physics and what not so theres no need to cover that.

Is your rear weight bias personal prefference? Please shed light if you do not mind.

 

For a primarily street driven car, I actually favor the power steering (and for these humid summers, my A/C as well). Granted less weight has its obvious advantages, but it has more significance depending on where the car sees most of its driving time.

 

the fd is a front engine rear drive car. as such, when attempting to lower road race lap times or canyon carve on the street the primary challenge is making the rear end stick from apex out. the more rear weight the better.

the first one on the gas in a corner wins... you can't get on the gas if you have no rear traction.

remember that unlike the front tires, the rear tires not only support roughly half the vehicle weight but drive the car forward.

that's why we run larger rear tires, lower rear air pressure, softer rear bar, softer rear springs and shocks. all to attain more rear grip.

additional vertical load from a greater % of rear weight helps plant the tires.

the front of the vehicle is most important from corner entry to the apex. less weight in front makes it easier for the front tires to change the direction of the car. less front weight equals less mass to change direction. less front weight creates better braking just before corner entry as you can dial in more rear brakes so as not to overload the front tires just before you need them the most at corner entry.

if you are just going to the store 50/50 is excellent. if you use your car more aggressively you want rear weight bias.

howard coleman

 

hey Howard, where and how much are corner balencing scales? I need to re-balance my car and I'm not too sure if any place around here does it.

Thanks,
Dan

 

I need to take a trip to the scales...my car is pretty light..no AC, no ps, gutted interior, passenger airbag removed, single turbo, cf hood.....

 

^ about $1k. Check out http://racerpartswholesale.com/

I'm sure some race-prep shop in your area can potentially set you up.

 

I think with stock glass and uncut steel body it is pretty hard to get under 2500lbs with twins, even with single it still isn't easy while still having enough gas to even auto-x the car.

 

1. Go to your car.
2. Open hatch.
3. Spend 1 minute removing spare tires and jack.
4. Place tire and jack on bathroom scale.
5. Read results.

 

Speaking of weight bias, my car already has a rear weight bias! If you put in a full tank of gas, it is 48.5/51.5. The only mod to reduce weight is a downpipe. I do have an aftermarket stereo, but that's about the same weight as the bose stuff. I still have A/C, P/S, etc.

But, if I empty the gas tank, it goes back to slightly front-heavy.

In my humble opinion, the single biggest packaging mistake Mazda made was to put the gas tank in the rear and nearly useless bins in the front. They should have put the tank right behind the seats and get rid of the bins. That makes for a lower polar moment and less weight bias difference from empty to full. Plus, it makes the trunk bigger so you can cram more stuff in there when you need to (it screws up weight bias, but sometimes you don't care). I realize that they did this so they could put in rear seats in Japan, but they're useless, too :-).

Take care,
Shad

 

LOL, well the FD did have a requirement of having rear seats, so the bins location was used. BUT even if it wasn't used the fuel tank wouldn't really fit back there. The FD is a RWD car, not FWD, the driveline and PPF tunnel right through the bins. I'd guess you could put dual 5 gal tanks in the bin location MAX, no way to put a large tank in that location.

 

I am removing the extra connectors from the harness i don't need including the wires all the way back to the ECU plug if that counts as weight reduction

 

re scales...................

while electronic scales are down to about a grand i suggest you look at Ruggles Scales. i used them during the last 10 years of my racing career and the work just as well as the more expensive electronic variety. about $425 from Pegasus Racing. they are accurate and easy to use.

howard coleman

 

what's the advantage of moving the battery to the back other than engine room? Sorry, i'm new to all of it and I've heard of people doing that. Isn't the best ground the firewall?

 

As howard said before... it lightens the front of the car so it helps the front tyres turn. Pretty much and weight from the front wheels forwards should be reduced as much as possible. Im not sure about the rear though... I suppose if you lightened behind the rear wheels you would make the car easier to bring back in if the tail swings out...

Don't take my word on it... take howards im just a lowly n00b

 

sorry rynberg just asked cause i just got back from afghanistan and havent gone and bought a scale from walmart. good idea though

thomas

 

Hello-

I know there's a PPF and driveshaft there... that's obvious.

That doesn't mean you can't fit a fuel tank there. 20 gallons is about 2.7 cubic feet. You could make one horseshoe-shaped tank to go over the tunnel with a 1/2" tube underneath to connect the two sides. Or, you could put two seperate tanks connected together at the bottom. Mazda wouldn't be the first to do things like this. Just food for thought... it would have given us more trunk space and a better weight distribution all in one, the only cost being that rear seats are impossible.

Take care,
Shad

 

There isn't really any room under the car for fuel hoses to connect to saddle type tanks. Start measuring, take a look at your stock fuel tank, I don't think you'd have room for a good sized tank, pump and filter and any type of decently engineered hose setup. Imagine fuel slosh from tank to tank, you'd need a more elaborate baffle setup and you'll also have to install the fuel fill pipe, preferrably without passing it through the passenger compartment. THere are more problems than benefits with that solution.

I'm intimately familiar with what that area looks like from both the top side and the bottom side, it is tight.

 

so they're basically the same as the more expensive ones, but they don't have the fancy computer to connect them? I'd have to build ramps to drive the car onto the scales.

-Dan

 

1. Transferred my battery to pass. seat storage compartment. (Also better corner weight distribution)
2. Replaced entire stock exhaust W/ S.S. Downpipe, cat and cat-back. (Must've saved 30 lbs. overall)
3. Lost the spare tire & added a can of FIx-a-Flat & a small electric tire pump. (Tools & jack now reside there in foam tire well filler.) I have SmartTirepressure monitoring system on the rims.
4. Tore out the usless Bose "Wave " rear speakers (22 pounds saved)
5. Bought 17" SSR forged wheels. Not much weight savings but better rear "gription" W/ the 9" wheels and 265 width tires. (No 18" wheels for weight reasons) Yeah, maybe more weight in rear but it is offset by the above rear weight losses.

QUESTION: Is it worth it in rotational mass loss & safety to install a carbon fiber driveshaft?
The current RX-8 has one stock.

 

I figure I could eat less Big Macs and it would result in a 50lb weight reduction.

 

The stock driveshaft is actually INCREDIBLY lightweight for what it is. Going to a carbon fiber driveshaft would be quite costly (like $500-1000) and realistically only save a few pounds - not a lot of bang for the buck there.

Makes more sense on cars with goofy multi-piece driveshafts.

Dale