Weight Reduction

[AnDoireman]

Well, I'm just recently after passing the annual "MOT" test, or a test of roadworthyness for your car, and I've decided now's the time to start making some mods. The thing that's been on my mind for a while now, is a strip-out. Losing the rear seats, carpets, parcel shelf, etc. I'm wondering how this is really going to reflect on my fuel consumption though. My car weighs 1280 stock. If I can manage to get 128KG of parts out of it (which I would probably consider unlikely) how is the 10% less (all from the sprung weight) going to effect my FE? Would I be likely to even see a 5% betterment? I was also considering losing my wing mirrors, but was talked out of it , probably still going to drop the mud flaps though. I can't see the mud flaps making a huge difference either, but every little counts. Essentially what I'm looking for I suppose is advice on stripping out. Is it generally seen that it's overkill to have to live with for the tiny increase in FE?

[offroad1994]

Think about it this way. MPG is about:

1) Weight
2) Efficiency of drive train
3) Aerodynamics

So if you drop the weight by 10% and the other two factors stay the same, then you will gain something in MPG. Take out the tire, and the rear seat and see what the improvement is, then calculate what the projected savings are.

All about the math.

[AnDoireman]

Aye, I've got that much like. I'd just like an idea of calculations beforehand, even roughly speaking. I'm not sure I could go without the spare wheel though.

[garys_1k]

Weight reduction is most significant in city, stop and go, traffic. Accelerating the extra mass up to your speed is what takes the extra power. Driving on the highway at a steady speed means the higher weight just coasts along, using little extra power (the weight on the tires DOES increase their rolling resistance, but only a small amount compared to the inertia power use in velocity changing driving).

So, how much of your drive is stop and go, and how much is cruising? If you go red light to red light (like the paper delivery guy in another thread), weight will count a lot. If you cruise a lot, weight won't make much difference -- aero will.

[aerohead]

I looked back over my materials,going back into the 1970s,and couldn't get a "straight answer" about weight reduction.In 1975,a 10% reduction would net about 3.7% average,the range was 4.8-6.48%. A 1973 intermediate car(3500-lbs) would see 0.4mpg hwy/0.5mpg city.In 1965 the SAE allowed 1/4mpg per 100-lbs weight loss.------------------------------- In 1991,100-lbs is supposed to yield 1mpg.----------------------- 1993 100-lbs nets 0.5mpg. Another source says lose 125 pounds,and pick up 0.5mpg.----------------------------- CAR and DRIVER compared the Mercedes 300E to the 300SEL and said the 470-lb weight difference( 12.41%) was good for 15% better fuel economy.---------------------------- Try and make sense out of all that!------------------------- I think if you drop 10%,you'll see it at the pump,especially in the city.Out on the open road I don't know.My CRX at 3,300-lbs only lost 2mpg compared to 1876-lbs.Good luck.

[Johnny Mullet]

Weight reduction does help, but only gets you so far. I maybe gained on estimate about 1 MPG by losing the rear seat, jack, spare, tools, etc, but removing my mirror and antenna gave me about 3 MPG increase, so I would suggest aero modding and some slight weight reduction.

Removing stuff like interior panels and carpet will only make the inside of the car much louder and pick up road noise. I removed all my interior panels in the back, but they literally weighed less than 5 pounds for all, so I put it all back in.

[rsx2002]

i removed my backseat and my spare tire at the begining of the tank I am currently on and seem to be getting 2 mpg avg each trip better than the last few tanks. I estimate it to be a reduction of about 60 lbs. How ever it is too soon to tell if that will stick. And in replace of the spare I bought a bottle of run flat. Most of my trips are less than 20 miles, with a few gas stations in town that have free air pumps so it should be sufficient to get me home. Now I am looking for some used racing seats. My front seats weigh 35 lbs each and they will only weigh 15. To me ecomodding is about adding up all the little improvements to get big results. Carpeting probably only weighs 5-6 pounds and the road noise youll gain by losing will probably will drive you crazy so I recomend leaving that in. there are much bigger things to lose first.

[Twerp]

I wonder what would happen if you replaced the carpeting with soft spongy foam... It prolly wouldn't be as resilient as the carpeting, but it should be lighter and might dampen some of the noise. It would definitely look weird...

[EP3]

I think every little bit helps. It is all about how far you want to go, and your comfort. I am personally trying to perfect my driving and get a baseline of a few tanks before I mod too much.

[Will]

I like Johnny Mullet's approach. I don't think I would want to give up the small amount of comfort in my Metro for 1 or 2 mpgs.

[Will]

I just found a way I can remove 50 pounds from my Metro I could lose 50 pounds

[rsx2002]

sounds like a good idea

[Twerp]

I've lost about 20 so far.

[modmonster]

wait- are you guy on the slim fast diet?

[nowhhs]

You guys must be doing something wrong. The only difference between the new Honda Fit and my 90 hatch is that the fit weighs 340 pounds more. Same size engine, same length and width. That extra 340 pounds, about 15%, costs it 12mpg! I think weight reduction must be the answer.

[NeilBlanchard]

Hi,

The Cd of the Fit, and certainly the CdA of the Fit is higher than your Civic. Aerodynamics are very important to FE; since most ICE vehicles do their best FE at 45-55mph.

[Binger]

I took out my passenger seat...which weighed 30 lbs, the back seat bottom cussion was 12lbs, both of the back cussions for the back seat are 7lbs each and the brackets for the seats and seatbelts weigh 5lbs.

[aerohead]

Originally Posted by nowhhs

You guys must be doing something wrong. The only difference between the new Honda Fit and my 90 hatch is that the fit weighs 340 pounds more. Same size engine, same length and width. That extra 340 pounds, about 15%, costs it 12mpg! I think weight reduction must be the answer.

For the EPA composite cycle,a 10 % change in weight would yield only a 3.8 % difference in MPG.Less than 6 % for the 15 % difference.There must be something other than weight to account for the 12-mpg differential.

[whokilledthejams]

Originally Posted by aerohead

For the EPA composite cycle,a 10 % change in weight would yield only a 3.8 % difference in MPG.Less than 6 % for the 15 % difference.There must be something other than weight to account for the 12-mpg differential.

Drag and gearing, probably.