Custom Car Brainstorming
 

Since I'm pretty much done modifying the aerofocus, I'm ready to move on to the next thing. Something I've always wanted to do is make my own car. I spent a while deciding on front wheel drive vs rear wheel drive, mid engine vs front engine, and 4 wheel vs 3 wheel.

My current plants are:
to build a mid-engine RWD drive 4 wheeled car with a narrower rear wheel track. I plan on using a geo metro 3 cylinder mated to a 5 speed. The reason for the mid engine is to be able to build an optimal front end and rear wheel drive because if the engine is back there, might as wheel put the power back there.

The purpose of the build is to create the most fuel efficient car I can and learn a lot about building a car! My dad was a mechanic for most of his life, so I'm confident we can handle everything. This will be done on a relatively inexpensive budget(aka reusing things) but it won't be cheap or ghetto either.

I am still up for input on many things, so here is a list of things to stimulate some brainstorming

3 wheel vs 4 wheel?
gas vs diesel?
turbo vs non-turbo?
OBD 2(post 96) vs not OBD 1 or whatever(pre 96)
It looks like I'll need airbags here in Ohio, although I haven't confirmed that. so that adds a slight challange. I may use the passenger compartment(A-pillar to B pillar) from the donor metro so I can have airbags, but I'll be gutting everything else out.

Ideas I've thought about but thrown out:
3 wheeled powered by a motorcycle engine. I'm not too keen on the idea of using a motorcycle engine/transmission to move something 2-3 times the weight it was designed for and I like the idea of having 4 wheels on the ground during winter.

4 wheeled with even track front and back
I've decided on the narrower rear track because it allows me to taper the whole car in earlier which reduces drag and will help my highway MPG.

My current "blueprints":
http://i1271.photobucket.com/albums/...us/design1.gif

Take note of my rear exhausted radiator. the air inlet slots on the side of the car will be able to open and close when needed and the vacuum behind the car should help pull air through the system. Let me know if this is a bad idea, but I think it's a pretty good one.

Here is a link to a website showing what I'll basically be doing: Dad's Dune Buggy. Mine will have a body around the frame and be road legal. It looks like he re-used the front suspension in the rear. If so, that seems like a real good idea to save time and money and be sure of the safety aspect.

I plan on going all out with the drivetrain modifications and the aerodynamics so hopefully I can reach 100 mpg while cruising at 60 mph. That may be a lofty goal, but I always figure it's good to aim really high :thumbup:

Again, let me know what you guys think about the build. I'm hoping to start construction this summer, but finances will be the main constraint.

By the way, it would be cool if you guys could make some of those fancy renderings that you always make so we can get a better visual than my sketches. :D

have you seen this thread:
http://ecomodder.com/forum/showthrea...tml#post336418

This looks like a cool idea. As for the radiator inlets, a NACA duct would be the ideal inlet without introducing drag. However if you already have the sides tapered inwards following the "template", I'm not sure how well the air will be able to curve in beyond that into the duct. It may be a non-issue all together, but something to consider.

I really like the idea of using a FWD engine/ trans layout in the rear, that seems like an awesome way to set things up simply on a budget, especially if you can pull the subframe all in one and deal with the suspension all in one. Plus, if you were ambitious you could easily have 4 wheel steering. :)

Weather Spotter- I have been following that build, but his build is definitely a step up from what I had in mind. I'm going to be using metal a lot more in my build. I'm not too confident in my fiber glassing skills and metal is something I know well

2000neon- I may move the ducts closer to the front before the car begins to taper in, but the edison2 VLC did it, and it worked for them. I don't think I'll be doing rear steering, but it is definitely possible.

The biggest problem I've run it to is the front glass. I'm pretty sure I need to use tempered glass my law but I can't find any cars with the right shape glass besides the aptera glass.

If I had the skills, time and money my answers would be

1. 4 wheels, a full compliment seems ideal. A mid-engined layout lends itself to mounting an FWD powertrain behind the seats with the steering locked. If you get 2 subframes from an FWD car you get both ends. The MGF was made this way :

http://www.carpages.co.uk/mg_rover/m...e_23_07_04.jpg

It used the front subframe of one of these at both ends :

http://i4.photobucket.com/albums/y10...GTi_red_vr.jpg
(this is what we in the UK know as a Metro...:D )

2. Tricky. Diesel is automatically better on MPG but worse on emissions and in some cases weight and reliability issues such as DPFs. I used to run a TDI here in the UK but all new Diesels have a DPF so I switched to petrol. On the plus side they can run on refined veggie oil for low $$s and have more driveable torque profiles.
If you go Petrol then smaller and more modern the better - maybe a Smart engine (watch for wear / oil consumption on earlier ones) or Geo Metro / suzuki 1.0 & 1.3 units. Also look at the smaller Toyota, Kia, Nissan etc. engines - somewhere between 1.3 and 1.5 would be ideal.

This will be driven more by what you have available locally than a general question I suspect.

3. If you go Diesel then turbo, if petrol then N/A. Turbo on a diesel makes it more driveable and can positively affect MPGs in normal driving and they tend to be more modern (TDI etc.) and FWD/transverse format. An NA diesel is more flexible on fuel and cheaper to buy but also heavier - think more truck engines than car ones.

4. The more modern your engine is then you gain more than you lose.
You gain the OBD2 stuff (readings and ECU) plus better FE and more power.
You lose based on complexity (more electronics) and also when makers link things like security (immobilisers) to the engine management system so it makes it more complicated when you use the engine in another vehicle.

Seems like I'll be going with a 90-95 metro 1.0L 3 cylinder mated to the manual tranmission from the 4 cylinder for the taller gearing. I'll also be going with the Xfi cams and ECU. It would be nice if I could find an Xfi engine with the lighter pistons, but metros are a dime a dozen here while the xfi version is not.

I most likely won't be using airbags due to the added complexity, but I'll have a large crush zone in the front and a 5 point harness. NASCAR doesn't use airbags and only recently began using head restraints because they have high speed crashes.

is this an all out mpg car? seems so because you chose the 3cyl. are you going to modify an existing car?

i've considered it a few times, if i were going to spend the time, effort, and resources to build myself a car. it would have to be fun to drive. i think either taking an aero sedan and making it a small truck or using an old dodge rampage as a base and putting a v6 in it with a tremec 5/6 speed would be ideal. im confident a good v6 in an aerodynamic vehicle with the proper gearing could easily do 50mpg highway.

This will be an all out MPG car but within the reason of about a $5000 budget.

I will probably be using 2 metros as parts cars, but most of the car will be from scratch.

1 metro will be for the 3 cylinder engine
The other will be for the tall geared transmission.

I'm hoping the car will be fun to drive due to a low weight, good aerodynamics, a lowered suspension, and good weight balance. Worst case scenario I'll have a 4 cylinder engine and a shorter transmission which I can mix and match with to find a good combination of speed and MPG.

People who have mated the 3 cylinder to the taller transmission have said there is some driveability problems, but I'm going to have a lower weight car than they had and rear wheel drive, so we'll have to see how it goes.

If you want to build the ultimate MPG/Aero car an alternative approach would be to get a Metro or a Civic and play with the aero. It will be cheaper because parts just bolt on and there isn't anything which mechanically hasn't been done before - things like the 3 cyl with the longer gearing. You could gain by being the lightest or the most aerodynamic as a lot of those types of vehicle have to retain seats or carry stuff.

Search for the Aerocivic thread and follow that if you haven't already.

A mid engined car using Metro bits might be a lot of fun though.

I have already modified a car. But I'm more into the challenge of building a car than anything. Plus, if I build the car from scratch, then everything can be the way I want it.

I like that there is a lot of people in my area with that mentality except it is with offroad vehicles instead of FE. People take a lot of trash talk if they buy their rigs prebuilt rather built from stock. I plan on 1 day in the next 5 years to strip an s10 down to bare and everything but the cab and frame being replaced for FE

Fieros are good for kit cars as you can remove the body and the rest of the vehicle is basically self contained (the Ferrari used in the early seasons of Miami Vice was a Fiero kit car - it's a fact! lol). Already mid engined, if you could mate the Metro 1.0l to the existing gearbox then you could build whatever body you wanted to around it, and all the really hard stuff would be done already.

A narrow rear track may be great for aerodynamic drag, but is extremely bad in snow because it pushes snow at four instead of two places. Double the drag.

Where's your gas log? We are curious about your MPG with all those mods.

Gealli- a lot of my kids at my high school think they're sweet driving the cars that their parents bought them with their flashy rims, exhausts, and stereos that they couldn't even install themselves. It's a sad epidemic. I feel like just 30 years ago, things were way different, but I wasn't there so I can't tell for sure. My dad says kids used to build up their own cars all the time. he also said prices were a lot cheaper back then.

War-Wagon- The idea crossed my mind, and I'm still considering it, but didn't want to have the deal with custom adapter plates between the engine and transmission.

JRMichler- very good point. Something I may have to consider. I think I will end up going without the narrower rear track because I would have the find/make new axle shafts and I'm trying to make this a lower budget build. obviously it will hurt drag, but I'll just have the make a longer boat tail! :thumbup:

Midengined! Good stuff.

As far as bike engine goes, the 2 issues are that 1. Motorcycle clutch is no good for starting a car 2. No reverse. Both are fixed by using a car transmission, but getting the motorcycle engine to mate to a normal car transmission takes a lot of fabrication. Best to just stick with a proven FWD drivetrain the way Elise/Exige/Evora/MR2 does. The one thing that will need some modification is the shifter linkage.

Same width rear track, sunken in ducts on the sides should be good. If you're going to have a bit of tail hanging out you'll be able to enjoy a lot of drag reduction already compared to typical cars, which have short rear overhangs for various reasons. On my MR2 Spyder the side ducts are sunken in at around the maximum angle possible.

You'll have the chance to design the ducting to pass air through the engine bay much more freely than on my MR2, so be sure to do that. Since some of the air on the side will be diverted to the engine bay, I think you can taper the greenhouse portion more.

I've pretty much given up on the motorcycle idea for these reasons. Thank's for the tips about the air ducts

I've been thinking about the front end of the car some more. I would like to make it a blunt front end like the aero template, but finding a piece of tempered glass in the right shape is proving the be quite the challenge. Plus, a wedge shape front end is better looking, so I'm going to use a little inspiration from dave cloud's cars.

I'm going to use the passenger compartment from one of my donor metros and chop the top like this: http://ecomodder.com/imgs/aerocivic/chopped-metro.jpg

I'll lose window functionality, but maybe I'll figure something out to get a functional window so I can breath during those hot summer days.

I may also switch the doors to being hinged at the top instead of the front.

This does 2 things:
1. gull wing doors are cool.
2. this allows me to not worry about interference from my body work.

Basically, this shows what my body work is going to look like around the front wheels:
http://i1271.photobucket.com/albums/...s/bodywork.jpg

It makes it much easier to make front wheel skirts that can cover the whole wheel all the way down and not stick out like a giant bubble.

Cool beans!

No need to re-invent the wheel. Just design within this envelope.http://i.imgur.com/wCEYs.jpg

The dymaxion uses flat glass in a teardrop.http://i.imgur.com/XfdLj.jpg

Given that the Metro parts are sized to a given aero drag, if you improve the Cd, you can increase the cross sectional area. And the length:http://i.imgur.com/nOLih.jpg

If you follow the Dad's dune buggy plan, please replace the rear coils with something sized more like the front ones. Build to a show car finish. You know you're going to want to show it, may as well make that part of the plan.

Autospeed has some pretty good info:

Monocoque tubs
Building an Ultra Light-Weight Car, Part 1

Building an Ultra Light-Weight Car, Part 2

Tubing trusses
Building Ultra Light-Weight Tubular Frame Vehicles, Part 1

Building Ultra Light-Weight Tubular Frame Vehicles, Part 2

I've been brainstorming a little more. and here is where I'm at:

http://i1271.photobucket.com/albums/...alerdesign.jpg

Now I'm back to the front wheel drive or rear wheel drive question.

Front Wheel Drive:
Pros
easier to fabricate
can have narrow rear track
more optimal rear end
can use existing brakes which simplifies emergency brake

Cons
Not as cool
slightly less optimal front end
Crowded engine bay

Rear Wheel Drive:
Pros
Really Cool and unique
more optimal front end

Cons
harder to fabricate
No idea how I would handle the shift linkage
less optimal rear end
emergency brake would be added cost and complicating with disk brakes around

With front wheel drive, radiator would be vented under car(or into front wheel wells)
With rear wheel drive, radiator would be vented into the wake

Let me know what you guys think. I'm leaning towards front wheel drive because I can pretty much just chop the car off at the B pillar, build what I want, and not have to worry about moving the engine all around. Plus, I have no idea how I would handle the shift linkages. Plus, I can have a narrower rear track to help the aero. I've dismissed the idea about a narrower rear track hurting snow MPG because I'm not planning to drive this in the snow very often.

BUT, a mid-engined car with rear wheel drive is too cool.

decisions decisions :confused:

Anyways, I think my design is something that an average person would say looks cool which is good

RWD / Mid engine is the optimum, there is a reason most race cars are mid-engined including reduced aero drag - this was the reason that Cooper cars used this layout to beat Ferrari with smaller engines in F1.

http://www.motorstown.com/images/cooper-climax-02.jpg

That tapped Arthur Mallock managed to compete with (and often beat) mid engined cars with his own front engine / RWD racers.

http://www.simonlewis.com/motorsport...-GT-Sept94.JPG

The disadvantages of the mid-engined layout are poor luggage space, poor mechanical access and (sometimes - e.g. early Mk2 Toyota MR2s) tricky handling.

FWD packages all of the components in one place with reasonable access and it can be extremely aero - the aerocivic for example.

http://www.inhabitat.com/wp-content/...civic-ed02.jpg

or the Metro based Dolphic electric car

http://images.thecarconnection.com/l...00339509_l.jpg

The early one was a Daytona convertible replica / kit car based on a vette. The later series used a (real) Testarossa because they were into spending silly money. They also featured supercars from the 80s - Phil Collins did an episode and had a Lambo Jalpa I think.

The forum software ate my lengthy reply when I clicked Preview Post. (grumble, grumble) Memo to self, copy before you click anything. Anyway...

You will need to lock down some decisions and not revisit them. Front engine = fiberglass body kit and a top chop. Mid-engine = cooler than poo.

Does the Metro use a rod or cable for the shifter? Mid-engine dune buggies have that all sorted out, look through their catalogs.

What are you using for your graphics? If it supports transparent layers, work over a side view of the real car and then turn the bottom layer off. You will see that your wheel/tire is way out of proportion. I know you asked for help with that. Without better specification, anything someone else might do will lead you away from where you want to be.

For the shift linkage, I imagine there's a simple way to attach it with the usual cables and whatever (I think FWD cars are all cable actuated shift linkages?), and then you'd just need to get used to the shift pattern being flipped around? Someone tell me if I'm overlooking something.

IMO the most important feature of midengined layout is the shorter front lets you keep the overall car length shorter with an equal length tail. Adding a boattail to a front engine car makes it awkwardly long. The need for side intakes and venting to the wake reduces drag slightly too.

I'm not sure if every model is the same, but Coyote X's geo build had a solid shifter linkage. which seems pretty simple to do.

Shifter installed

HydroJim - you may take a look here: http://grabercars.com it's a sports middle engine car build from a scratch. You may get some ideas there and answers as well.

You mentioned engine air flow earlier.

You can run radiator hoses to wherever you need, the rad doesn't have to be right by the engine. That might free up some of the decision process. However for a FE car, remember a long hose run will increase total coolant capacity slightly so warmup time will be slightly longer.

I've seen mid or rear engine performance cars in the lot at work with the radiator in the front. Sorry, can't recall if they were Porsches or Lotus. In nice weather, we often have several of both in the lot! An odd perk of working where jet engines are designed built, more than one employee is seriously interested in speed for some odd reason.

For now, I have decided to stick with the front wheel drive, because I am trying to get this done in one summer and it will require a lot less fabrication to keep the engine in the front. Plus, gains from putting it in the back would be minimal and front wheel drive will allow me to pull the rear track in to help with the aero.

Hopefully I can convince the university that I study at to fund a fuel economy project so I can build the mid engine car I dream of. I think I could beat the edison2 VLC with the right budget. :cool:

Some questions:
What are some weight saving mods specific to the metro?
Maybe some lighter brake components are available? I know the civics have light drums and wheels.

Any idea how to deal with rear window defrosting?
I'm not sure if I'll be putting a window in, but it would be nice. I just want to make sure I can see out of it if I have one.

What do you think of this guy's mods?
Singh groves and intake manifold turbulence
Grooved Metro number 2

Search is your friend.

I feel like the coolant capacity thing is not that big of a deal, as car radiators are pretty big in the first place.

But yes it's typical for mid engine/rear engine cars to stick a radiator in the front. I actually can't think of a car that doesn't do that, although I might be derping. MR2s have the radiator in the front. Some supercars with additional cooling requirements might have radiators sitting in the back as well. Space in the back is precious.

Oh what do you know, the McLaren MP4-12C ONLY has radiators in the back, to save piping. I think that's what those divided inlets are for, the inner ones turn air into the radiators.

http://i1271.photobucket.com/albums/...etrodesign.jpg

This is where I'm at in the design process.

Maybe you guys can help me name it? It's going to start off as a 1989-1994 geo metro, but nothing will be recognizable except things under the hood. I plan on painting it white because there won't be A/C to cool a dark car and white paint is generally cheaper. It will be a 2 seater(maybe a third whose legs would be between the front seats) and I'm shooting for 100 mpg while cruising at 60 with the use of lean burn.

I'm sticking with front wheel drive because I'm trying to get this done in one summer and rear wheel drive would add too much fabrication time.

Since it looks like Dave Cloud's car, "Dolphin Too"

If you move the rear axle forward, with the same taper, you wouldn't have to narrow it as much. It might corner better.

I actually used Neil Blanchard's dolphin model that he made in google sketch up. I plan on using the same car, so it saved me a lot of time. My rear axle will be about a foot or 2 more forward and should only be about 7-8 inches narrower than the front which is what the honda insight's rear track dimensions were. Based on the streamlining template, the sides can have a lot more taper, but the top needs to be pulled up a little bit.