Replacing parts with lighter parts to save weight?
 

I was thinking, if I had a '96 honda civic, in order to save weight, would it be cost effective to replace things such as the Windows (except windshield), Hood, trunk and doors with lighter materials?

Carbon fibre is quite expensive, but fibreglass should be cheaper, also Fibre glass weighs less unless we're talking lb for lb strength. So I was thinking I could replace at least the hood and trunk (Bonnet and Bootlid) with fibreglass and or carbon fibre parts. I'm not sure if they have this but I would if I could replace the fenders with fibreglass and or carbon fibre as well. For the Windows, I'd possibly replace them with something like Perspex. The only thing I'd worry about for the Perspex is how likely am I to damage it and how much would it cost. I'd try and store all the original OEM parts in the event that said replacement parts get damaged or whatnot. They also make a carbon fibre door but I don't know how much that would cost nor how it'd impact safety. Would going with an aluminum door be possible? And would it add a significant amount to weight savings?


How much does the Hood, Trunk and windows (including rear) weigh individually?

Just read about Lexan, maybe this would be a better alternative to the perspex? One reason I'd want to use the lexan is because it'd be stronger than the glass, making breaking and entering into my vehicle more difficult, not to mention safer for me. I also don't care too much about tint.

I think the cost of doing something like that would be very significant. also I have heard (and this is just what I have heard) that it takes 100 lbs of weight reduction to get .1 second better in a qtr mile. I know we aren't racing but we use a lot of racing technology for FE.

also of note: I have a friend that rides to work with me. he weighs 220ish lbs and I don't notice a difference in gas mileage when I drive alone vs when he rides.

I think there are long term advantages to weight reduction but you would have to lose a lot of weight and it would take a while to recoup the money you put into the weight reduction.

just my opinion

How often do you ride with your friend? Has he ever been with you through an entire tank of gas?

Gym membership : $35 - $80/mo, Personal trainer, $20 - $40/ session

Weight loss is expensive and a lot of effort... ;)


I have a friend that is 450 pounds. I always think what kind of mileage increase he could get by loosing weight. When he rides with me in my truck he is so large sometimes he has difficulty buckling the seat belt.

Now, to be a bit more on topic, there is a bunch of crap I never use that's just thrown in the back seat, and in the bed of the truck. I figure I could easily shed at least 200 pounds from the vehicle by taking that stuff out and putting it in the garage. Its just the problem of finding time to do it.

-Jay

I don't know the actual costs, but for CF replacements for fenders and hood, you'd be beyond $1000 invested, and only save 50-60lbs, if that. Fenders don't weigh much, being so small. And the structural supports built into a CF hood only allow for 10-20lbs of reduced weight. A CF hood for my GP is only 15lbs lighter, yet costs $650. Even tubular control arms save 3lbs each. I remember reading someone decked their GP for drag, completely stripped (bare metal inside, lexan windows all around), with lightweight parts swapped. It weighed ~3150lb with a 200lb driver, vs me and my GP at 3520lbs. Extreme example, not worth doing on a daily driver.

There are better ways to invest in your car than expensive weight reducing parts. Areo-mods are more likely to increase FE than weight reduction.

as far as my comparison with and without my friend in the car, I have a scangauge and I have one of the displays set at trip mileage and that is what I am basing it on. I drive 20 or so miles each way to work so it is a descent comparison. I haven't done complete tanks both ways but the difference is so minimal from the days that we don't ride together that I didn't worry about that experiment

one day he jokingly said something about weight reduction by taking out the rear seat (I think it is less than 30 lbs) and I said if I could just get the 200lb weight out of the passenger seat, I would be doing even better. He didn't think that was funny.

my mileage may suffer because he rides with me but we carpool and take alternate days. I went from filling up every week to just about two weeks between fill ups.

I would think you would gain more (dollar for dollar) by blocking your grill and working on aero than replacing body panels. if you look at racers, they do weight reduction last because it is the least bang for the buck in my opinion

I replaced my Civic's hood with a CB hood. cost me $700 before shipping. looking for a CB trunk lid that's a little cheaper but they are still quite pricey at $500 to $600.

it can be done and lighter cars do get better FE but at what cost. save in gas but it will take a while to realize the benefits.

there was an article about why there wasn't a 50mpg car today and ford said they could make a focus do that easily. they went through all the details about aluminum frame and aluminum body panels all the electronics to make it happen but he finished the conversation by saying the car would cost around 60k which most people wouldn't spend on a focus regardless of the mileage.

I think the idea is the same.

not sure how much you care about looks, but don't forget to factor in the cost to paint the parts.

So if weight is a minimal factor, then why do people try to justify the Civic VX getting better mileage because its curbweight is 2094lbs vs 2313lbs of the Civic HX? Also why does the HX weigh more than the DX coupe which comes in at 2262lbs?

I think that curbweight has a greater factor on city driving MPG than highway driving as I've seen quite heavy vehicles get about 30-34MPG on the highway but 20mpg in the city. At 1000lbs differences, it's really about gaining momentum (city driving) and maintaining momentum (highway driving). It'd be interesting to see a comparison of two vehicles one weighing 6000lbs and one 3000lbs being the same in every way except weight and seeing what kind of highway MPG they get.

Just as a flywheel stabilizes the output of an engine, I think the mass of a heavy vehicle actually helps it once it starts traveling at highway speed. It carries a lot more momentum, plus the heavy vehicles also have larger displacement engines which barely have to turn to maintain a highway speed of 65 mph. Its simple... An object in motion will want to continue to stay in motion. the engine has to do little to keep it going.

-Jay

easy. I towed a trailer with an F250 2 weeks ago. Going to pick it up: 16.7mpg. Towing it home: 9.2mpg. I had a tailwind going, headwind coming back, so it exaggerates the stats, but the truck weighs about 4700lb empty, and the trailer was pretty close to 3000lbs. In town was just as bad: slower starts, longer braking etc etc. Weight of that magnitude will make a difference.

Its just the 200lbs in a sub 2500lb car with a motor that can handle 3000lbs just fine isn't going to make a huge difference (maybe 1mpg). And at a cost of $500-700 for a hood that's 10-15lbs lighter, that's not worth it unless you can make it pay for itself within a reasonable amount of time.

I will find out in 2 weeks how much of an impact 3 more (over 2) people in my GP (3380# empty) make on the highway. I'm assuming 3-5mpg hit. I know there's not enough lightweight aftermarket parts to offset the weight of 3 people to keep that 3-5mpg. I know that after all the parts swapped, It'd only be about 140lbs saved. To my car, thats a passenger to me driving. It doesn't notice.

Like beef said, it can be done, its just way too expensive for the net gains.

For normal city driving, weight does matter, but you have to talk about a significant amount. 300 pounds in a 2000 pound vehicle is significant. 100 pounds in a 2500 pound vehicle is probably not.

Common hypermiling tactics may make weight significantly less important. When hypermiling, one avoids acceleration as much as possible, trying to coast instead; acceleration is the time when weight matters. Hill climbing is affected, but while descending extra weight can help keep DFCO longer or gain more speed.

How much weight do you plan to save by replacing parts?

another factor about the VX example is that it has lean burn which kicks in and shoots your air fuel ratio to something like 17:1. I am not an expert on this but I have heard about it. that is why the VX owners are...well that is one reason the VX owners are getting stupid good mileage.

I have heard of someone taking 150lbs out of a geo metro and getting better mileage but they didn't replace it with anything. took out the seats, body panels (interior) and insulation (road noise deadening material). personally I want some level of comfort in my drive and versatility in case someone else wants a ride. you can take out your spare tire and save a little but one flat will kill all your profits from gas savings. just my opinion

the hx comes with air conditioning, power steering, electric door locks, and electric windows. depending on the options of a particular the DX it can be had with out power steering, air condirtioning, or electric anything else. I have a 96 DX hatch and the only difference between it and a base CX was the passenger side air bag. it has power nothing.

a lighter vehicle with a drive train identical to a heavier vehicle will get better mileage. it takes more energy to accelerate and maintain the velocity of greater mass. the only exception would be if the route a measurement was taken from was downhill. the word "insignificant" is vastly abused in automotive forums and seldom used by engineers. There are measurable differences between systems- whether or not one considers a difference "significant" is a matter of opinion, economics, convenience...

the vx and hx have different drive trains. the vx is lower powered and more efficient regardless of the weight difference between it and the hx. it also has a smaller frontal area and I believe a lower drag coefficient. taller gearing too...

Don't forget about lightening the parasitic loads on the engine. Aluminum pulleys, carbon fiber driveshafts and lightweight rims.

Maintining velocity of greater mass requires almost zero more energy. The only slight difference is a tiny amount of rolling resistance, which barely differs with more mass (unless we're talking about many times as much mass). Furthermore, additional mass can help a hypermiler have longer glides, as the additional mass beats aerodynamic drag better, and is probably less affected by bumps in the road.

Now, that's not to say that I advocate adding ballast; indeed, if you can remove a LARGE portion of mass without consequence, it's probably still a good idea. The gain from removing the spare tire, jack, and backseat in most cars would easily by beaten by always driving on half a tank instead of filling it up all the way, though.

Thats what i did on my mazda, removed/gutted as much as possible and drive with only 5 gallons. Since i post in the garage i have been filling the tank. I may go back to 5 gallons to save more weight and do aero mods now that i have sort of a base line.

Most carbon fiber products are actually fiberglass products with carbon fiber overlay.

Cost will never be justified. But I would suggest getting a one-piece fiberglass front end. You're wasting your time just doing the hood alone.

It's much cheaper to get the Odyssey motorcycle battery in place of the factory battery. Same weight savings, much much cheaper price.

when I say "maintaining velocity" I mean in real world driving. When I am driving a car with a real time gas millage computer it is very very rare that the mileage settles on some number, say 40 mpg at 60mph. In the western U.S. (where I live), it is very very rare to drive on a flat road. throttle position is changing almost constantly as I respond to: slope, wind, air density, safety, merging, passing, police presence, animals in the road... the computer millage reading reflects those changes. I try to minimize throttle position changes to maintain a constant speed but still: In order to maintain a mass at a given speed I am changing throttle opening in order to do it. It takes less energy to maintain the velocity of less mass than more mass. it is measurable. it makes a real difference.

5 gallons of gas wiegs approc 30 lbs. if you take more than 30lbs out of a car you are allways hauling around 30lbs less mass. you will get measurably better milage.

"Furthermore, additional mass can help a hypermiler have longer glides, as the additional mass beats aerodynamic drag better, and is probably less affected by bumps in the road."

the above sounds like conjecture to me.

a lighter car with all else being equal will always get better millage unless you live in a world where you are always going downhill.

??? What do you mean by this?

I beg to differ. I'm almost certain that if you were to put a D16Y5 in a VX, convert it to OBD2 and run the Y5 ECU, you'd get better mileage than with the Z1. I plan to do it someday. For now I'll settle for my 3 Stage VTEC swapped VX getting 39/47 mpg.

Hole saw and packing tape.

in the end, what is the purpose? you spend more at the pump but you save possibly thousands in new body panels that go on a car that already has them? how much gas are you planning to save?

if you want to do it because it is cool then go for it. I think that if you were doing it solely for FE then you will probably never realize the gas savings from that investment. I hear that carbon fiber is really expensive (I may be wrong).

1.5 liter vs 1.6 liter, very different final drive ratios, different valve sizes, different intake manifold shapes and runner size, different ecu, difffernet v-attack actuation point, different redline. lots in common to be sure but quite a bit different too.

It would be interesting to see how it worked out! i am getting 38/42 or so with a y5 mini-me in 96 hatch. I drive 70-80 to get the 42ish hwy mileage. I hope to get a little better than that as i dial the set-up in.

You can get extensions for the seat belt free from the dealer for just about any car.

Actually the HX has a better drag coefficient due to it gradually coming together towards the trunk opposed to the VX. The VX would be more like an SUV in the sense of drag.

80% of the drag comes from the rear of the vehicle.


Naw, I think you've got the most ideal setup. Reasoning is that you've only got 1.5L block opposed to the 1.6L block. A larger cylinder means that much more fuel, unless you can get it to learn out even more than with the smaller block.

The big problem is when I have crap piled in the back seat, and he can't get that seat all the way back. I need to get that stuff out of there anyway. Right now I have about 4 Kirby vacuum cleaners (cast aluminum!), then some stuff I bought at yard sales and flea markets that just never made it into the house. It would be nice if people could sit in my back seat again... :)

-Jay

Kirbys are tanks. I had the pleasure of having to use one of those things around the house growing up. You'll lose 100 lbs right there.

HONG KONG (MarketWatch) -- Nissan Motor Co. will cut the weight of its vehicles by an average of 15% over the next seven years as it seeks to improve fuel efficiency...

I am going with a fibreglass hood thats only $350 shipped for my BMW to cut weight, Lighter seats, no exhaust, and a lighter batter (mazda miata probably to stay cheap). All this and wheels + tires should net around a 200lb weight reduction (on a 2800lb e36 318i).

Remember, less weight means less pressure on the tires which equals less rotational friction with the road... I think the less weight the better. Heck, I think cars in the future will go down to around 1500-2000lbs (just like in the old days).

One factor that I haven't heard in this entire thread so far is the safety impact (pun intended). Mechanical Engineers designed the crash safety of your car based on the ACTUAL parts installed on the car and NOT based on the installation of aftermarket parts. You may be literally risking your LIFE to try to increase fuel economy by reducing weight. Regardless of how much money you've got in the account for car repair emergencies and car insurance deductible, no matter what your car insurance coverage is, no matter how much car insurance coverage the other guy has, no matter how much health insurance you have, in the event of an accident, it's just you, the safety cage of your car, and the physics of the collision between you and another car or you and a stationary object. The crash strength of your car will be the only actual life insurance you've got. The science boils down to: 1) If your car is strong enough to protect you in the collision, you live 2) If your car is NOT strong enough to protect you in a collision, you die. Was the weight savings worth it if the new lighter part is only designed to geometrically fit into the position where the previous part was located without being strong enough for a collision?

The same safety argument comes into play for those here who go from a heavy modern car to a 1992 Civic VX or Geo Metro...it's just not a high priority for a lot of folks here. Different strokes for different folks.

Nonsense. Do you have any specs to back this up? The HX was made into a coupe for the same reason that they added power steering and all the other luxuries. Not for mileage, but to sell the car.

Calling a VX an SUV... those are fighting words.

The 1.5 and 1.6 blocks are exactly the same block. The D16Y8, D16Y5, and my D15Z7 have the same block. Same part number. Same "size".

How can they physically be the same block yet be called two different things? The only way you could have a 1.6L is to have enough volume to BE 1.6 Litres. I wouldn't be surprised if they bored out a 1.5L block to make it into a 1.6L just like when they made the 1.7L block for the 2001+ models. Why else would they be called D series engines unless they made huge overhauls for each incremental increase in litres for the block?

The civic coupe is going to be far more aerodynamic in the rear than the civic hatchback. The civic hatchbacks drop off far too steep, like an SUV which is why I made that comparison. https://www.gearlog.com/2008/02/modde..._honda_civ.php
What that guy did made the CRX far more aerodynamic because of what he did to the rear, not so much to the front. I was very surprised to read that most of the drag a vehicle has occurs towards the rear of the vehicle but if you learn about fluid dynamics, it'd probably make sense. I believe it's mostly attributed to creating a negative pressure behind the vehicle, so when you have sort of a diffuser, that is when you can significantly improve aerodynamics.

Maybe the VX hatchback has additional aerodynamic features that aren't visble in order to make it more aerodynamic than the coupes. Though if everything is the same aside from chassis shape, the Civic Coupe should be more aerodynamic.

I thought they had different bores.. 84.5mm vs 90mm if i recall. same stroke. they are interchangeable but a bit different in sleeve thickness i think.