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Weight Reduction - a Comprehensive Guide

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  • Weight Reduction - a Comprehensive Guide

    Weight Reduction is one of those things that I always wind up talking about in other people's threads but never seems to have it's own thread for any vehicle, so here goes:

    As with any aspect of tuning, you will have to make compromises when you cut fat. Sometimes these compromises are minimal, sometimes they aren't - your own and your vehicle's level of involvement is up to you, but hopefully this guide will help you through the process of trying to figure out what to pitch, what to cut, what to buy, and what to leave alone.

    Cutting the ribs from the factory hood can save a lot of weight, especially when the factory latch is replaced by aluminum hood pins. A rib-trimmed hood may not have the rigidity that is required to stay in place during high speeds. Usually a third or fourth hood pin is required to keep things settled down. Also, if the factory hinges are spring-loaded, the springs may need to be removed unless you want the inadvertent "raised hood modification". Usually ribs are taken off completely by cutting the bond between skin and rib with a hacksaw blade. If some ribs are needed for rigidity, an angle grinder can be used to shave them down.
    A fiberglass or carbon hood may also be purchased (usually the first thing to spend money on) but will most likely need hood pins to secure it. Different shapes and vents are available, and the less material, the less it will weigh.
    Some OEM body panels are quite light already (AE86 fenders) and don't need replacing. Some body panels (Cressida trunklid) are anchors and need to be ditched/lightened ASAP! Additional body panels depend on manufacturer and material, expect to pay handsomely - replacement doors come in carbon only most of the time and can fetch up to and including $600 per door!
    Cost -
    De-ribbed hood/trunk = $1.50 hacksaw blade/$4 grinding wheel
    Fiberglass hood/trunk/hatch = $100-350 depending on material and style
    Hood pins = $20/set for knock-off, $30/set for locking-type
    Compromises -
    Weaker panel if shaved, spent money if replaced

    For some of us a car needs to be a Lay-Z-Boy on wheels, gliding along in smooth silence while Bach softly fills the cool cabin air. For others a seat and a wheel is all that is important - screw all that other stuff! Perhaps what is surprising is that weight can be saved either way.
    For the coushy-types, a manual slider seat can replace a power seat and save a bunch of lard in power motors and switches. How often do you adjust the seat anyway? A Momo or Sparco steering wheel will generally also save some valuable ounces and feel good on top of that. Ditching the spare, tie-down, toolkit and jack in favor of a fix-a-flat is also often a good move unless you're driving across the desert or alligator alley and don't have AAA. Plugging that sunroof you never use will also help - here either a metal plug, fiberglass plug, or lexan panel (with plenty of silicone sealer and pop-rivets) can be used. Welding a metal plug to the other roof material might accually gain you a smidgen of rigidity too, but don't try taking on Mt. Akina with any boost of ego...
    For the iron-hided commandos, a substitute heater matrix from a Miata or EF Civic/CRX will save you here. For those Miata and CRX drivers, just ditch the thing and get a 12-volt fan for the summer and a coat and gloves for the winter! Ditching the stock seat and sliders for a rigid-mount aluminum, fiberglass, or carbon racing seat will be rougher on the bum but better on the turns as well. Pitch the rear seats, seatbelts, and brackets unless you plan on mounting a harness to them. Carpet - who needs carpet, you got socks, right? Once the carpet it out why not peel up the sound deadening using some dry ice and a chisel or soaking the whole bit in some WD-40? With carpet goes healiner and sunvisors - sunglasses are cheap.
    Interior lights can go, since few guys will read a map anyway. Other gadgets such as clocks, compases, thermometors and that drawer-thing on the passenger side (don't knwo what that is...) can go as well. Door panels can usually be replaced by a flat panel of fiberglass, aluminum flashing, or that foam-core poster board you can get at Wal*Mart (just don't get it wet) pop-riveted onto the old panel. The metal inner door frame can also be cut away so that all that is left is the window-lift supports and edges. While the door panel is off, ditch that power window mechanism for a handcrank and work those arms, ya pansy. The dashboard also never did you any good, and the stereo and speakers only served to drown out that soothing engine roar.
    If you've got the cash, Flex-a-lite now makes sets of polycarbinate windows that can substitute lightweight plastic for those heavy glass rear windshields and windows. Make sure that if you're going to run the car on the street that they pass your state's safety regulations, otherwise you'll have spend a lot of money on windows AND tickets!
    Exterior mirrors can also be dumped in favor of light racing mirrors, which will slip through the air better at high speed anyway. The rear view mirror inside can be swapped for a Broadway or autozone-equivalent, not only improving your rearward vision but also helping those in it stay behind you.
    Although not technically "interior" items, fancy options like fuel-filler door releases can also be taken out and replaced with either a race filler door or simple gas cap.
    Rear window wipers can be eliminated along with the motor. The passenger side front wiper arm can be taken off and the driver side modified to cover the full sweep on the passenger-side spline. Turn on the wipers and shut the car acc. off right when the wipers are at their highest, then put the wiper back on the desired maximum sweep.
    Headlight pods can be replaced with Pilot or Cibbie headlights, which are lighter and brighter than OEM equipment, but once again, make sure that they conform to safety req's.
    As for a horn, if you live somewhere that has a fair amount of traffic, a horn is pretty key to not getting hit. If you live in the boondox, this piece can probably go without much consequence. Make sure to remove the whole bit though, and not just the noisemaker - bracket, wiring, fuse and button can all go.
    The only other ends that come to mind are just the extraneous things that no longer have a use or never had a use in the first place. This includes excess wiring for options that the car wasn't built with, brackets for interior panels, trim plates, pads, fasteners, tape, excess sheilding, covers, latch parts, and whatever. Sure they may be small and insignificant on their own but a bucket of little things can add up to one big savings - removing the accy. wiring on 4-th gen F-bodies can save 40 lbs!
    Cost -
    Usually free, lots of time ripping things out...
    Dry Ice = $5 (be careful not to freeze your fingers, it's dangerous!! Seriously!!!)
    Broadway mirror = $15
    Racing Mirrors = $50 to $350 depending on material
    Steering Wheel = $35 to $250 depending on brand and style (a quick-release can be a good theft deterent)
    Racing Seat = $100 and up. Sparco, OMP and Kirkey make god entry-level models
    Race filler door = $25 to $50
    Headlights = $20 a pair ( -> store)
    Fix-A-Flat = $7?
    FAL Lexan windows = $250+ depending on application
    Compromises -
    Less cozy? More Cozy? Depends on your outlook...

    There isn't much free that can be done to remove heavy mechanical parts, but there is a lot of weight to be saved here. Even if all you do is buy a cheap cotton gause filter and ditch the airbox, you'll be improving performance to the engine and getting rid of more stuff that'll slow you down. Often times a cold air intake or short ram will weigh the same as the OEM intake tube and give better flow, helping to increase power. Heat shields CAN be removed, but usually they are worth their weight unless replaced by carbon or aluminum pieces (although aluminum has a lower specific heat than steel, making it less effective at blocking heat transfer). A lightweight racing battery can cost quote a bit and usually isn't available at your local Pep-boys, so a 3-coil Optima Battery or tractor battery with high Cold Cranking Amps (brought to you by the letters CCA) will allow you to pitch the old heavyweight of a battery, or use it as a home-made electric chair for bugs and your little brother. A ceramic-coated aftermarket header will also helo to free up some flow and is lighter than the stone-age technology cast iron piece that has been choking your motor, but be careful not to rip the wire out of the old O2 sensor or else you'll be spending more money than you planned. On the spinny side of things, light flywheels will improve response and shed some pounds (5-20) and will be further improved by an aluminum driveshaft. In drifting power steering is usually a very useful acoutroment, but for autocross or drag racing it really doesn't matter all that much and can be dropped as long as you can find belts that will fit your motor without the P/S pulley (in most cases you'll want to leave power steering if your car came with it). You could stop by good 'ole Flex-A-Lite for a lightweight aluminum fan as well, to go with your lightweight Koyo radiator! An aluminum or carbon fiber (available for 4AGE from Japan and B-series in the US) intake plennium may cost a pretty penny, but will look prettier under the hood and on the flow chart. If you've got the money for something like that, you could try bolting it down with aluminum or titanium ($18 a pop) fasteners just to show off. The list of possibilites increases as the wallets get fatter, but those who have the funds to do such things already know what is possible (check out Ueno's Soarer to see what money can do for the weight of a car).
    Cost -
    Air Filter - $20 for the official Super Street version
    Battery - $20 Tractor, $100+ Optima, $depends Lightweight
    Cold Air Intake - $50 Ebay to $200 nice and new
    Header - $50 Ebay to $300 new (no rust)
    O2 Sensor (in case you break it) - $60
    Intake Plennium - $30 if you can weld, $300 if you cant, $a lot for carbon
    Light Flywheel - $250-$500
    Aluminum Driveshaft - $400 for S13
    Compromises -
    Um... Spend money maybe? It's not like you wouldn't get these things anyway just to improve performance and response.

    If you're going to get coilovers or even just springs and dampers, it never hurts to save some weight. Koni's or KYB's can save you about 10 lbs per axle over OEM suspension while SilkRoads or Tien HE's will save about the same (beefieness is heavy). If the suspension of your car will be roll-resistant enough to eliminate sway bars, you can save a good amount of heft quickly. If you want mad understeer, just removing the front bar will give you that and so much more (but be careful on the street in the rain or you'll kill yourself in a high-speed spin). Bushings don't weigh much, but Urethane ones are better for handling anyway and can save about a pound for a full car's worth. Aftermarket TC rods and tie-rods that are made from aluminum may be tougher than OEM when installed properly and do what? That's right - weigh less! Aluminum control arms, wheel studs and lugs can also cut the ever-important unsprung weight, making it possible to turn harder and grip better.
    If you only get one suspension modification (besides SilkRoads, that is), then get some lighter wheels. Motegi now makes wheels that weigh in at around 11 lbs for 16x7's to match Volk's TE-37's and the hundred fifty million other wheel companies that are making lightweight alloy wheels. If you're lucky enough to be able to find used OEM rims that fit your car then you can save a bundle over buying new, but often times even brand new packages of wheels and rubber (which drifters will promptly burn through) will go for less than $750. Your best bet for budget-friendly light wheels is to buy off of somebody who needs money and has wheels. Sets of 4 will go for rediculously low prices (think a case of root beer and a burned Dido CD).
    Cost -
    Coilovers - $1000+, SilkRoads and Daiyamas for around $1200 at
    Bushings - $100+ for full car, depends on what you get.
    Rims - $250 for a used set up through $5000 for uber-light JDM only steamrollers.
    TC Rods - $?, hit up and check out their TC rods - way better than those Korean knockoffs (no offense to Korea) and cheap to boot!
    With suspension it really depends on what you get. Quality suspension parts are important - you don't want something to be breaking at 100mph as you're sliding past a barrier with people behind it, unless you're a sadistic sicko . Also don't waste money by going half-way. Once you use a set of cheap coilovers you won't get much for selling them. Something awesome like Zeal or Daiyama or Silk Roads will be worth the money.
    Compromises -
    Rougher ride, and something that begines with an "M" - you get one guess...

    There's a lot of crazy stuff that track-only cars can be subject to. The Calsonic team shaved almost 100lbs off of their RB26 in the 02-03 JGTC season just by grinding down the Iron block. Removed bumper supports and carbon bumpers can save you loads of weight. Metal gas tanks are for the DOT, a real car drinks from a cell. Everyone's got a bunch of Benjamins laying around that can fund cutting out that crappy old floor pan and replacing it with a Carbon honneycomb one. If Silvia is really self-conscious, she could always get the ultimate in automotive lyposuction with a tube-frame conversion...
    Cost -
    Ask the team at Mopar.
    Compromises -
    People will say that you sold out. You'll have to mortgage your house.

    WHAT IS YOUR LEVEL OF COMMITMENT? (a VERY loose guideline of what you can expect to pay, and what you can expect to save):

    ENTRY LEVEL (for the comfortable daily driver, weekend racer):
    Removed spare and jack, removed air box in favor of cone filter or intake, removed floor mats, drilled bumper supports, lightened/fiberglass hood and trunk, lightweight steering wheel, manual seats, sunroof plug, exhaust header
    Total ~ $100 to $450
    Savings ~ 100-200 lbs

    DOUBLE-DUTY (noisier ride, fewer passengers, faster times):
    Smaller Heater Matrix, tractor/3-coil battery, removed trunk and rear carpeting, removed rear seat, removed option wiring, hood pins, trunk/hatch pins with removed release mechanism, removed rear wiper and motor, removed stereo and wiring, window cranks replace power option, lightened wheels, broadway mirror
    Total ~ $75, sell your power windows, stereo and old wheels for used light ones.
    Savings ~ 125-325 lbs (in addition to Phase I)

    BAM!!! (for the hardcore, no grannies with hemroids allowed):Removed bumper supports, fiberglass front and rear bumpers, no interior trim, racing seat, removed horn, removed A/C parts, removed heater matrix, substitute headlights, no heat shields, coilovers, single windshield wiper, removed gas tank door and release, removed sun visors and map light, removed sound dampening, fiberglass/aluminum/posterboard door panels, racing mirrors, removed power steering(?), removed sway bars (?)
    Total ~ $1500 depending on what you get (coilovers = handling = $)
    Savings ~ 250-350 lbs (in addition to Phase I and II)

    FIND A SPONSOR (high-dollar weight savings):
    Engine shaving, ceramic exhaust, carbon body panels, fiberglass/carbon doors, lexan windows, titanium bolts, fuel cell, urethane bushings, aluminum radiator, aluminum fan, carbon/aluminum intake plennium, aluminum driveshaft, tubeframe chassis... "Speed costs money, how fast do you want to go?"
    Total - "More than you can afford, pal"
    Savings - "A penny saves is a penny earned"

    I hope this helps bring the whole topic of weight savings together, and maybe even earn a sticky from the mods and a link in the Beginner's forum - that would sure be nice


  • #2
    good write up, it should be a sticky


    • #3
      Heres a good one dont fill up your windshield squirter. A gallon of water wieghs 7lbs. Also wouldnt a V-mount intercooler setup get the weight of your intercooler and radiator farther back. And it would get all that coolant farther back.

      Would cutting the ribs out of the hood and then laying two layers of fiberglass still save a lot. It would help rigidy a bunch. (I dont know how much those ribs weigh)


      • #4
        yes sticky this.


        • #5
          Yeah, definately. I believe a gallon of gas also weighs 9lbs, but am not sure. But, racing/drifting on a tank that is about a third full is about right for a day's worth of runs and doesn't cost you extra weight.

          You're definately right about the V-mount - it puts the weight farther back and lower AND helps cooling on top of all that. I guess it would save a fet feet of turbo piping, so it would even maybe help weight savings if you didn't gain it all back in radiator hosing and bracketry. If you've got the room, there's really no reason not to do a V-mount besides just doing the work. I could do another write-up about the same length on how to re-arrange weight if people really would like to have one posted, but I think this one is enough for today.

          Regarding the hood - a stock hood weighs around 45 lbs depending on the car (longer hoods usually weigh more, duh) and a fiberglass hood can weigh anywhere from 7 lbs to 15 lbs depending on the thickness, how big it is and whether it's got ribs or not. Laying F-glass on top of metal isn't really that beneficial if you cut all the ribs off because then you're just essentially making a flat laminate. If you were to attach the ribs to a fiberglass hood skin, you'd save some weight since the skin could be very thin, but if you were going to do that you may as well make fiberglass ribs instead and resin them to the thin skin.



          • #6
            MR is the man, officially.

            Unofficially, he should be president.


            • #7
              Originally posted by GRiDRaceTech
              MR is the man, officially.

              Unofficially, he should be president.
              we can agree on that....

              And yeah Mr anything you can write up ill read.


              • #8
                Originally posted by nissanguy_24
                we can agree on that....

                And yeah Mr anything you can write up ill read.
                Aww shucks fellas, I'm flattered

                I was pretty much just getting tired of posting the same stuff in a bunch of different threads - I have a speil about why weight reduction is so important with math formulas and everything as well that I guess could be an appendix or something...

                I'll see what I come up with.

                Thanks a ton for the compliments!



                • #9
                  Originally posted by mranlet
                  I was pretty much just getting tired of posting the same stuff in a bunch of different threads
                  Thats exactly why this should be stickied.


                  • #10
                    nice this is a lota help i was looking for someting like this earlier..thx


                    • #11
                      Well, in case this thread falls into oblivion, it's posted in my sig for anyone who is interested...


                      • #12
                        This doesn't help my fat *Censored**Censored**Censored* supra. J/k Great write up.


                        • #13
                          Originally posted by mranlet
                          Well, in case this thread falls into oblivion, it's posted in my sig for anyone who is interested...
                          Make sure you have a back-up saved. Some times useful threads get lost during house cleaning.


                          • #14
                            Originally posted by emission
                            This doesn't help my fat *Censored**Censored**Censored* supra. J/k Great write up.
                            I wrote it just for you, sweetums.

                            I thought you said the Supra was totaled?

                            I have a copy saved on my Hard Drive becuase these things happen...


                            • #15
                              MR, you forgot how valuable drivetrain lightening is: every one pound shaved from the rotational bits of the drivetrain is equivalent to shaving 20 pounds off the car.

                              Thus, shaving 6lbs from the flywheel is like shaving 120lbs from the car. Shaving 10lbs from the driveshaft (very easy to do on the 240, considering it's a heavy two-piece unit... probably weighs about 30lbs) would be like shaving 200lbs from the car. Going with a lightweight four-puck clutch assembly would sacrifice streetability a little due to a stiffer clutch pedal and more abrupt engagement, but might shave a couple pounds.
                              $350 for flywheel, $460 for aluminum driveshaft (less if you have it custom-made) and $380 for the clutch... so total price of $1190 for the equivalent of 360lbs of weight removal without any sacrifices in comfort. By the way, that leads to a 0.36-sec faster quarter-mile, if not more due to less parasitic drag.