Building a 100mpg consumer vehicle
 

I'm going to build a 100mpg consumer vehicle.

Goals:
100 mpg mixed, 75mpg at 75mph.
Legal in Idaho (where i live).
seats me (285 lbs, 6'1") and my lady (not a petite lady) COMFORTABLY.
My lady has to be willing to ride in it.
My lady has to be willing to drive it on occasion.
1000 pounds???
Build it for less then 5000 bucks at my redneck engineering shop.

It will be reverse trike, enclosed, with heater and AC.
Honda engines are cheap, and I have a 93 honda civic hatchback which has been rolled over (DX) as a donor car.
Seatbelts, rollcage, windows, etc.

fiberglass body which my 16 year old son will be willing to drive and proclaim as "cool" (hardest spec, but essential for marketability).

Engineers and people with excuses why I shouldn't do this can do me a favor and keep their mouths shut.

I have started laying things out, and prototyping.

Some interesting things. Tandem REALLY SUCKS according to my lady. She refuses to ride around with her knees 2 feet apart, and I don't want a car which is 12 feet long.

So. Lots of trials and fitments. We removed the two seats from the hatch. It appears the inside of the car will be 33 inches wide. This allows the driver to be offset to the port side, the passenger to the starboard side, and behind the driver. It gives room for the passenger to put their legs on one side of the driver, but both have plenty of shoulder room.

front of car appear to be 60 inches wide, main cockpit 33 on the inside, and over all height is going to be 44 inches or so, despite my best efforts to make it lower.

Wheelbase will end up at 10 feet or so.

I don't think a used stock driveline set up for a much heavier car will do what you need it to.

Sounds like fun! Got any sketches?

whats wrong with a 12' long car? some added weight, no added sail area, a chance to reduce Cd. and 12' is pretty darn short, a truck is generally over 18'

should have clarified - the car will be over 12 feet, but I don't want the wheelbase 12 feet long.

...remember, long-thin is better for aerodynamics (lower drag).

That's what she said!

No seriously, get a Ferrari kit car. It's fibreglass so you can cut and mould to reshape aerodynamic problem areas. Put a little diesel inthe back. Kubota has nice little 2&3 cylinder diesels, 10-25 hp eforethey get really big and heavy The 10 hp would run for hours cutting grass on a gallon, very efficient you could find a garden tractor with manual gearbox but they are non syncromesh trannies mate it to a firefly transmission it wil run nice with some tall skinny tires

ferrari kit cars pretty much do not exist. We will both probably get a letter from Ferrari's lawyers for even mentioning using a Ferrari kit car - they have a LARGE team of very bored lawyers sitting around sending nasty letters to people like you and me who even think about making Ferrari replicas.

Besides - Lamborghini is a much cooler car. I plan to use a Murcielago nose........
(Grins!!!!!!!!)

Hi drmiller,
I wish you the best, this sound really exciting.
I wanted to make a couple obsevations. First a 10 foot wheel base is pretty long, this is necessary for tricycle stability, right?
And have you looked at the links on the Zing post? The Zing is an electric with (opional?) gasoline genset. On the apteraforum Ken Fry makes the point that conventional gasoline generators have really poor efficiency, but he will do better.
To achieve 100 mpg you will still need an efficient engine. I hope you can get a better match for your load than "Honda engines are cheap..."

Good luck, and keep us informed of everything.
-mort

Subscribed!

Yes I work on 900cc kubota diesel generators that run at 1800RPMs and put out 4kw continously for about 36 hours on 11 gallons of fuel.
I have been trying to get one to use as a generator for years.

The Zing is a different approach. I am actually ahead of that project in terms of build and layout. he will have a few surprises, but and I invite the owner/designer of that company to jump onto this thread, and I would be willing to discuss in order to both build a better car.

I have my basic frame laid out, motor mounts designed, steering completed, suspension pretty well ddsigned and laid out on the front. Rear suspension SHOULD be pretty simple.

The car keeps growing and growing.

True tandem seating has some pretty serious issues for mainstream Americans. The basic idea of sitting tandem really sucks for the back rider. If you don't believe me, my seat for my ass is over two feet wide, and most people, especially LADIES, don't want to sit down very long with their knees spread 2 feet apart.

So, we end up making the car wide enough to offset the passenger, and the passenger must be offset to the starboard side in the US. So, now the passenger can lay their legs out to the right side of the driver.

Will we have an emergency brake? Where will the handle be?

Will we have a 5 speed? if so, then the shifter must be on the right side of the driver.

Add that up, and pretty quickly we MUST have a door on both sides of the car.

Plus windows which roll up and down of course.

Add that up, and pretty soon the car gets even wider.

As for length, the steering rack sets the back of the engine, and needs a foot or two from front axle centerline.
Driver needs 4 feet of leg room to make pedals with a low car.
Passenger really ends up needing 3 feet of leg room unless you make the car taller.
Then you need a foot of clearance behind the passenger's behind and tire.
and the back tire is 24 inches tall, so another foot back to wheel centerline.

Pretty quickly 10 feet of wheel base is eaten up.

120 inch wheel base seems pretty long. But the back is a LOT narrower then the front, so it won't cut corners.
Steering is pretty sharp, so turn radius won't be truly ignorant.

And of course you have reverse.

I don't want diesel on this project. I have a diesel truck and if I wanted diesel, I'd just drive it around on the 55 cents per gallon I can do.

I want mainstream commuter car. Diesel is not an acceptable alternative in the US. If I can get 75 at 75 on gas and 100 combined, I'll be happy enough.

The only Porsche I drove had the hand brake on the left side of the drivers seat tucked down so you didn't snag it getting in and out, not ideal but it worked, my commuti-car has the hand brake pull up right under the steering wheel, having it pull out of the dash like it is on pickup trucks is also an option, as I see it, the gear shift should be pretty far forward that it shouldn't be in the way of the passengers feet, if you are unsure of this try sitting in the back seat of a car that has the passenger seat removed and see how far forward your feet rest.

Do you have any photos of your progress so far?

i say build the car the for one and delete the passenger. That will be version 1 so for version 2 you can work out the things.

The passenger needs to sit on the starboard side of the car.

If we have one door, it is not realistic to put it on the port side - the passenger would then have to lift their feet up to their chin to get their feet over to the starboard side.

So, we put the door on the starboard side. If we put the only door on the starboard side, then the gear shift and emergency brake are in the way of the driver getting in and out. The e-brake we can move around a bit, but the gear shift is a PITA anywhere else for a 5 speed.

an electric car will not have these issues.

Interesting project.

In your original post you call it a "consumer car". How are you defining "consumer"?

What's your basis for this statement? Noise? Weight? Just curious.

The important unadressed question I see is, what is about your vehicle that going to be different and thus give you 100 mpg? It looks like your going to have a stock engine, stock frontal area & weight (as compared to say a Geo Metro). I guess you can improve the aero some from stock. Where are all these extra mpgs going to come from?

not a stock engine. Lean burn is for sure in the works, as well as a few other tricks.

frontal area should be half of a metro.
drag coefficient should be pretty good as well.
weight should be in the 1000 pound range (I am hoping).
aero should be a LOT better then a stock metro, or even a honda.
rolling drag should be only 75 percent of a metro.

will I get 100mpg? hard to say. Can I double a honda CX with half the weight and half the frontal area and only 3 wheels?

Makes it fun to try!

as for diesel, most consumers won't put up with them.

Depends on the ride.

In all seriousness, though... Since you're obviously looking to work within a budget, have you considered finding yourself an old VW chassis (bug or Karmann Ghia); installing a high-efficiency motor; and doing a custom, aero body redesign? They are already laid out for a rear engine/rear drive, so you can do almost anything you want to clean up the aero on the front.

Also, if I were in your shoes, I'd be asking myself if I could do better myself than just getting a used Insight. Then again, maybe it's not big enough/spacious enough?

So, did you like driving that 914? :D

-soD

the only diesel option I considered is an old vw diesel rabbit, non turbo. 60 horsepower or so, FWD, really light.
I might build one of those, or stuff the engine in my car if I can't get to the 75/75 mark with gasoline.

I own a couple of VW pans. I built several cars off fo those. for a variety of reasons I want FWD.

So what about the "consumer vehicle" definition? Are you planning on selling this vehicle commercially?

A dream would be to sell a few vehicles a year to feed my children.

Realistic? I don't know.

I am building it in case it works - 3 wheelers are motorcycles and don't require crash safety stuff. I am using automotive motors so I can get past the EPA regs.

And I want to make it as "consumer friendly" as reasonable.

My landlord came by yesterday - he said he would want one with an automatic transmission even if he only got 60 or 70 mpg. He spends too much time on the phone to shift gears and survive in traffic.

I'm more familiar with large diesel EPA regs, but here's my take:

I don't think using an automotive engine will get you past the EPA regs. I think the regs are based on the year of the vehicle--not the year of the engine. In addition, I believe all passenger vehicles need to be chassis certified (not engine certified)--so the vehicle needs to be certified, not the engine.

That being said, here's 2 ideas for how you might get around the EPA regs if you decide to go commercial:
1) Look into what regs apply to "choppers". I mean, guys make custom motorcyles and trikes and I assume the EPA is okay with that.
2) If you're just selling it in Idaho, for use in Idaho, you might not have to deal with the EPA. This is because, it wouldn't be "interstate commerce", and therefore not under federal jurisdiction. I think I recall hearing about Montana or one of those western states that was using this argument with respect to federal gun laws. They claim is the guns are made in the sate, sold in the state, and marked to not leave the state, then the feds didn't have jurisdiction.

Just be glad you don't live in California!
http://abclocal.go.com/kabc/story?se...ent&id=4977150

What route are you taking to license and title this vehicle?
My favorite route that works well in my state is hobbyist plates, those are the plates that are used for home built vehicles, but also for hot rods, kit cars or any vehicle that is no longer stock and is over 20 years old, because of that loose and broad definition you can pretty much take any 20+ year old vehicles vin number that you also have a title for and put it on your home built vehicle, if you are building a kit car or home built vehicle then they want records that show that parts you used were not from stolen vehicles and it is supposed to be inspected.

I have the titling and licensing figured out. Don't really want any help on that, don't really want any unfounded opinions which start big problems, rumors, and issues.

Suffice it to say I can build my vehicle for my use legally. Someday if I choose to sell one or two I will do it completely legally.

Hi Doug,

The Zing! is driveable. It has been getting 100 mpg on gas and 10 miles per kilowatt-hour on electricity (which the EPA calls 337 MPGe). I hope others do not think that the Zing! is just an idea. (The Volt, for comparison, gets 37 mpg on gasoline, and less than 3 miles per kilowatt-hour (93 MPGe))

The term "proof-of-concept" prototype may have tripped you up. The concept has been proved -- the car performs as predicted. The Zing! POC is not like a Detroit "concept" car where they are showing off styling and future ideas on a chassis that may not even have an engine.

Your project sounds like it should be fun.

Regards,
Ken

For perspective on engines, chassis, and aero:

Steve Fambro built a gasoline-only Aptera (as one of their numerous prototypes). It had a 660 cc kei car engine. Like all the Apteras, it has excellent aerodynamics and a composite structure. He got 55-60 mpg. The same car with a Civic engine would get about 45-50 mpg.

If you hunt around for the BSFC maps for these engines, you will see that when producing 15-20 hp the 660 is substantially more efficient than the Civic engine at that hp, because it is more heavily loaded.

As a general rule, unless you are planning to create a hybrid, around town mileage will be lower than cruise speed mileage. The Prius is the only car in which both figures are essentially the same.

A good place to start, unless you have unlimited funds, is with the math. You will find that for 100 mpg, your car must need very little HP to go 60 (on the order of 6-8). That means very light weight and excellent aero. Once you have that, then you cannot use a large engine because you also need very low brake specific fuel consumption, which means a highly loaded engine.

Do you have a Cd value for your body, and its frontal area?
Have you calculated the HP requirement at 60?
If you have the data I can run a spreadsheet for you.

Regards,
Ken

60 inches wide front fenders, 2 feet tall.

cockpit is 42 inches tall by 35 inches wide.

The windshield is behind the fenders. Does that mean my frontal area is 10 square feet, or 10 plus 5?

No idea on Cd. .30 should be pretty easy. .20 possible????

Lets guess 1000 pounds.

I've got a few ideas to try to improve efficiency on the engine. lean burn is a no brainer. cam profiles are worth messing with. And i have a couple of other ideas from old school rednecks.

If I get close, but can't get it all the way, I've thought about using V-tec to hold two cylinder's exhaust valves open, and shut off two fuel injectors. Idea would be I would shut off two cylinders and lose the pumping losses at part throttle.

I've got another couple of ideas to minimize pumping losses and relieve the penalties of a large cc engine.

Ken, on your car, I tried mocking up seats with true tandem. We really did not like comfort in the back seat, and our criteria is a 45-60 year old lady MUST be comfortable in the back seat. We ended up making the cockpit a bit wider, and it REALLY added to comfort and usability.

http://ecomodder.com/forum/tool-aero-rolling-resistance.php?Weight=1000&WeightUnits=lbs&CRR=.00 8&Cd=.25&FrontalArea=12&FrontalAreaUnits=ft^2&Fuel Wh=33557&IceEfficiency=.22&DrivetrainEfficiency=.9 5&ParasiticOverhead=0&rho=1.22&FromToStep=5-200-5

Depends on how much overlap there is.

If you took a picture from the front, and colored in everything that was the car (fenders, cabin, wheels, tires, etc) the total of the 2-D colored area would be the frontal area.

-soD

With those dimensions it's physically impossible to have frontal area of 10 sq ft.

ok.
60x24 for the nose = 1440
20x33 for the cockpit above the nose = 660. minus probably 60 because the top corners are rounded.

call it 2000 square inches - / 144 - = 13.8 square feet.

can I make it as clean as a Prius or Insight? I sure hope so.

I have two slots left for 2012. See Think Big. Drive Small. for details. My phone number is on the site, so feel free to call anytime.

so I am confused. Is the Zing! a single seater or 2 seater?

If you have 38" headroom, and 5" ground clearance, and a 4" thick seat, you'd have 47" height with the seatback vertical. A Corvette is 48" which may be a reasonable minimum for being seen, especially with the narrow cabin. The Lamborghini Countach was only 42," as is the T-rex. I've towed the Zing! POC, and see just a tiny bit of the roof out the back window of my Accord. The POC is 44", and the production version is 49."

It sounds like you are saying that the top of the fender is 24" off the ground. A 24" diameter is a smallish tire. You will probably want several inches for suspension travel.

There is no standard for how a manufacture must measure frontal area. I prefer to use the actual dimensions from a cad drawing, including wheels, etc. In your case that would reduce the area a little, because we wouldn't be measuring the air under the car. We'd have to count the projection of the rear wheel.

Your 13.8 figure is probably pretty good, if you're OK with the height.

The Zing! POC seats 1; the Zing! production version seats 2.

Hi Doug,

The calculator you linked to is useful for certain very limited purposes. As you probably know, the urban cycle has an average speed of 20 mph. I plugged in numbers for a Prius (plus driver) using its peak fuel efficiency of 38%. At 20 mph the Prius gets 196 mpg, according to the calculator. We know the Prius really gets 50 mpg on the urban cycle, so the calculator would appear to be off by a factor of 4.

the calculator

The "problem" is that the calculator is applying one efficiency number to all speeds. If you look at 85 mph (on the perfectly flat road represented by the calculator) then the number is close to 50 MPG, meaning that at that speed the engine might be operating at a point near peak efficiency. But we would have no way of knowing that, because we didn't look up the efficiency at the power required for 85 mph. (Because we are working backwards, we can conclude that the Prius engine must be close to 38% efficient at 85 mph, where it is producing 27 hp. So at some speed, the calculator produces a number that is close. At all other speeds, it produces a number that is incorrect -- any where from wrong to incredibly wrong. And we have no way of knowing where it is producing a correct number be cause we can't feed in the right BSFC for each load condition.

To use the calculator, you'd have to plug in actual efficiency figures (from a BSFC chart) that correspond to the engine efficiency at each speed. (This would be much easier to do with another spread sheet made for the purpose.
That other spread sheet, or series of spread sheets, could assess the power required at each five seconds on the UDDS, lookup the relevant efficiency at that power point, and use that in doing the math.

For many cars, you can come close to a correct combined figure if you calculate the fuel efficiency while going up a 2.5% grade at 45 mph. You calculate the hp required (more or less as as the linked calculator does, but incorporating grade) then find the efficiency at that hp level and then do the math to find mpg.

Optimizing for running near peak efficiency is why a Prius gets twice the mileage of an Accord. You can't just plug in a single efficiency value for either and get a good mpg number.

Of course, you can skip the math, and just go ahead and build it. It will probably get pretty good mileage.

Regards, Ken

Sounds like fun. You'd probably get fewer pumping losses with both valves closed, rather than pulling in exhaust through the open exhaust valve.