light weight car? suggestions (for removing weight from 81 VW Rabbit diesel)
 

Hi Guys,

I am thinking about possibly cutting some of my car away to lose some weight. Its a 81, 4 door rabbit diesel with hardly any rust anywhere its the one in my pic. I have 2 aluminum small truck camper tops that i can cut up to use to replace a lot of the cars heavy metal.

I was thinking about getting rid of the back door glass and the rear hatch and probably about 2/3rds of the roof and using one of the camper tops to close it all in . i am guessing this would be around a 200 or so pound weight loss. I thought of using part of the other camper top to make a front air dam for the car and a underbelly. It gets really hot down here in east texas so im a bit worried about doing to much of a grill block.

I am wanting to bust 70 mpgs with this car. heck 100 would be better but i dont think in this hill country thats gonna be to easy. One other option for weight reduction would be make it like a mini truck and just cut the back end off from the door glass up and use the camper shell to close in the back of the cap since it has the right small rear window set up already built in. I even thought about drilling holes in some of the metal to lighten it up.

I dont think i can get many more mpgs from the car with my driving habbits...... heck i would make most gramdma /grandpa drivers look like speed demons LOL.

any thoughts or suggestions?

Thanks for reading, Don

As the owner of an '81 convertible I ask you to please not kill that beautiful Westy! Make reversible mods wherever possible.

If the interior is already stripped (and I hope you either kept it or sold it to an enthusiast) you could get lexan windows made and pick up some lightweight wheels. You can lose the bumpers and save some real weight, take out any A/C system it had (the compressors are heavy) and remove the spare tire.

It sounds like you do a bit of highway driving, in which case doing some aeromods would really help, possibly even more than weight reduction. GTI valences are supposed to be the most aerodynamic of the mk1 air dams, so try to get one of those from a junkyard. If you've already built a smooth belly pan I'd start on a Kammback or boat tail built off of the hatch. If you can't attach one without drilling consider building it off of a strap-on bicycle rack.

If you're looking for other ways to save weight search VWVortex for Mk1 racecar build threads. There are probably several to peruse.

Don't cut!

Hopefully these will help you??
 

Weight reduction to the max & documented :)

Lane's SCA - Project 92 SC - Weight Reduction (1)

Tom Stickland's MK2 Vauxhall Astra Pages (Opel Kadett)

I read a technical paper recently where the researchers improved the FE of a late-model TDi just 2% by removing about 250 lbs from the car. In contrast, reprogramming the chip yielded 4%.

OTOH, one CAN get 70 mpg from an old Mk1 dwiesel radjit... :D

Start by reading this Ecomodder thread and the linked article about the "Rabbit Sipster". Forget transplanting a TDi into it...just apply the aero mods he does and I bet 70 mpg is not out of the question. Heck, I used to get 50+ mpg from my first-gen Rabbit and Pickup both just by using a light foot.

you can move 500 pounds or so fairly easily, but then it gets expensive.

spare tire, glass to lexan, remove window regulators, bumpers, bumper supports, back seats, spare retracting seat belts, AC, etc. are all pretty easy.

or, start with clean slate, build a trike from scratch, and 1000 pounds finished is realistic with your power plant.

Tru dat, Dr Miller! The article I read did all those things, plus made carbon fiber hood and rear hatch, sun roof, etc. Big bucks for negligible gains. In the Rabbit Sipster article he gained about 10-12 mpg from the engine swap (from low 40's to ~55 IIRC), but got another almost 30 mpg from very crude aero mods (floor pan and front treatments, mainly). By the end they recorded ~84 mpg.

I wouldn't hack up a nice one. There are plenty of rust buckets to choose from for hacking up.

DO NOT start with a rust bucket of any car to modify. Rusty cars are dangerous and should just be crushed. The effort to modify a car deserves a good starting point. And geez, how many precious highly valuable 4-door Rabbits must we save?? :rolleyes:

I say go to town on weight reduction, if you have hills, it makes a big difference! But don't sacrifice aerodynamics in the process. A camper top sounds worse than the stock rear.

Interesting about the weight vs chip tweaks.

I also used to have an 81 diesel Rabbit, and saw high 40s constantly. Didn't know squat about eco-modding.
Take a look at three-wheeler's Honda or the aerocivic. A good boattail should help you out.
I also suggest you replace the soft rubber front motor mount with the harder rubber from VW Sport or better yet polyurethane. I ran a poly mount for some time; doesn't really change the vibes and it keeps the engine from rocking.

Sheeit, here in the rust belt most everything over 10 years old has rust. They aren't dangerous- you just have to figure out how you're gonna attach the new metal.

Rabbits are like Vegas around here- haven't seen one on the roads in decades. I sure as hell wouldn't hack up a nice one, especially if the hack is likely to gain me 1 mpg... or less.

If you really want to go to an extreme and mod a VW, get one of the convertibles and put a Diesel engine in it, the car you have is a unibody and cutting in to the body will make it weak, convertibles have a stronger sub frame, of course the draw back to a convertible is that they tend to weigh more because of the reinforcements that are needed when you don't have a roof.

I agree with what everyone else has said about not making mods that can't be undone, after all you have a car that when it was new had an EPA rating of nearly 60mpg while being a 4 door hatch back.
But if you really do want to make your 1,900 pound car lighter, I'd start with unsprung weight.
You are also going to see an improvement with better/faster glow plugs, a block heater and smoothing out the underbody air flow.

In my opinion, don't worry about weight, concentrate on aero. I live in hilly country( Vermont) and use the hills to my advantage. With an added passenger( my son who weighs 260 lbs plus), I see little overall difference in mileage, more going uphill, longer coasts going downhill, pretty much a wash.
I know that the MKI and MKII are a bit different, but there are a lot of similarities.

I would suggest an upper grill block, full belly pan, and, if you really want to get wild, put a tail on that wabbit.

If you have the 4 speed, your top gear ratio is the same as my 5 speed with my re-geared 5th. If you have a 5 speed, there are options for re-gearing 5th here that might benefit you.

Keep (V)Dubbin'!

buy one of these

Trabant - Wikipedia, the free encyclopedia

1,653 lb, and a 4cyl will fit in it; there's an outfit in toronto that sells them

A 1990's Toyota Tercel hatchback , cheap, light,reliable and fun.

Can you do some ABA testing to determine how much 250lbs difference makes? Or add another 100 to test 350 lbs.

It is not a wash going up and down, you don't recover the lost efficiency of the engine from going uphill, and if you have to brake going downhill it is worse.

for market research, if you could buy a car body and put your running gear into it, what would you pay?

it would be a 2 seater, tandem, with huge doors for easy in and out.

total weight would be 1100 pounds ready to go.

Would you pay 3000 for it? 5000? 10,000?????

hi guys,

Thanks for all the responces. Its been an internal battal as far as cutting the car up to make it lighter. With the responces i think i will leave the car as it is and just to what project sipster did.

Everything takes me a while to get done, partly due to financial situation and partly due to some of my physical limitations. I did move my fuel cut off switch to my gear shifter to make it easier to get to and i like it there much better. the car has really tall gears in it already I was told it has the tallest 5th gear that vw put in them, and driving the car makes me a believer of that.

the grill block worries me a bit but im going to start doing it in small implements. I have a couple of small pieces of plexi glass i can cut to make the headlights smooth and was thinking that maybe blocking the lower grill portion first...............I mean if i did a bumper type airdam (Bumper to 4 inches above the ground) it would have the lower grills blocked anyways.

thanks again guys.
Don

Years ago Chrysler engineers determined for each 100 lb loss in weight, a 0.1 mpg gain was obtained. This applied to larger cars with higher Cd. Test by adding weight. I would not carve on the unibody or eliminate all forms of bumper for safety sake. Substitute lighter materials and eliminate parts not used. A lighter battery, wheels, and seats would help so long as you don't sacrifice satey or comfort. Big gains are from aero mods and driving techniques.

Nimble and Grant- With Pulse and Glide techniques, there can be an advantage with the extra momentum. There have been quite a few posts on here where they will say that their best trip on their favorite road was with extra weight in the car. I also have taken data on all my car usage with load descriptions and ambient temp., and found that there was less difference with weight than temp.. Just my vehicle, my roads, and my experiences.

If one has silly amounts of cash, Volk wheels might be worth to consider, in Rabbit's size single wheel weight is under 3kg, tires can be heavy too, so one could save a lot of weight with good tire choice.

Replacing rear glass with plexiglass or thin not transparent plastic might be possible, depending regulations on your area.

Problem with cutting the car is that body is self supporting structure without separate chassis so if one would make it more like 2dr short pickup with aero bedcover, that would require some ingenious support structure that would not kill driver when one is rearended by blind fellow motorist.

If driving is at city, weight has meaning, but if highway, then weight has less meaning, in Rabbit's figures, as starting weight is so small, that it is not possible to cut it to half like with some bigger cars it is possible.

In rallying, most crazy ones use acid treatment to make sheetmetal thinner, but they have rollcage and sometimes fibre parts, like hood and front fenders, doors from glassfibre or if money is no object, making those from carbon fibre might provide some weight savings. Gains are however bit questionable, at least at highway.

Suzuki Alto, that is something that was before Geo Metro (early 80's) I believe? Weight something around 600kg, putting rabbit motor to such might be easier and more beneficial as weight reduction of Alto might put it to 500-600kg with rabbit motor and getting rabbit to that weight would be really difficult, also Alto would have less frontal area too, finding one might be challenge though, they did rust a bit. I think Alto is hypermini class or something like that, it is a lot smaller than most others I know, almost any other really.

Besides, nobody will ever miss Alto, but Rabbit is icon, don't cut that.

Places to loose weight in a Mk1 VW: in no particular order
1)remove undercoating from bottom of car
2)remove asphalt sound deadening that is attached to the inside floor
3)remove sound deadening under the carpet - VW has used several types over the years, sand, thick felt, foam- westy is most likely foam backed rubberized cardboard. and from under the hood if it's still there
4)You should already have aluminum bumpers, if not, the steel core bumpers are 45# each.
5)replace the telescopic bumper mounts with solid stamped steel bumper mounts from base model.
6) remove any unused carpet and side panels.
7) Solid disk front brake rotors- your car should have them already
8) light weight rims and tires
9) replace factory seats with something lighter like Lotus Elise seats or aluminum racing seats.
10) replace widow glass with lexan,polycarbonate etc - light weight plastic but I'm not sure which will last the longest/not scratch easy
11) make bolt on body parts like hood, fenders, doors, hatch, etc out of carbon fiber.
12) smaller alternator and battery
13) replace any steel brackets with ones made of aluminum.
14) remove any excess muffler/exhaust components. - replace cast iron manifold with tubular headers.

A friend has a 77 Rabbit that is in the 1600lbs range. Once you are done striping all the comfort items out of the car you will be left with a tin can brick with the aerodynamics of said brick. you will need ear plugs to drive = you wont want to drive it after spending lots of time and money. That will give you excelent savings in fuel since you wont be driving anyplace.

About more aero bumpers, I have seen the big bumpers off of 90ish jetta's and golfs morphed onto Mk1 rabbit and pickup bodies. Actually looks decent. Or find the clipper kit off a 88 and newer convertible rabbit.

to the OP: Hi there neighbor!

I know the terrain you drive very well. It's just about PERFECT for pulse and glide. I agree that weight isn't too much of an impediment. I do get lower mileage when I'm loaded down, but it's only by a small margin. I'd go for aero and easy weight mods first.