If You Were Going To Build A 200mpg Car..
 

If you were going to build a 200mpg car...

what engine would you use?

Ninja 250 motorcycle engine maybe, or a buell 500?

So my question is, for per/hp and gas consumption... which is the least gas sipping engine out there?

I don't know much about those specific engines- but I think the most important issue would be precisely controlling the air fuel ratio. So it would definitely need an oxygen sensor and computer. Perhaps a liquid cooled engine would be better at running a little lean without overheating.

Better think about what car you are going to use because even if you double the efficiency of any engine you still will not get 200mpg without a extreemly purpose built vehicle.

Well, lets say that I plan to build (from scratch) a three wheeler.

Not a super-complex-want-to-beat-every-car-out-there-at-everything kind of car, just an everyday car that I can commute with.

As far as the engines, I have read that ninjas get around 90mpg with a simple sprocket change so coupled with better areodynamics, harder tires, and even lower gearing I think its possible to hit very high mpg's.

(I come from a racing car background so thats why i ask about gas efficiency, to me (in the past) and efficient engine was one that could hit 1000hp and not break lol)

Bikes are not geared towards fuel saving, so they have really tall gearing, really soft tires (look how much they last 3000miles at the most?!) and their areodynamics are not that great around .37 for a Suzuki Hayabusa (and its considered a really slippery bike).

Get really low resistance tires, lower that .37cd to about .20, add only about 400 pounds or so (which doesnt matter because weight has barely no effect on highway cruising gas consumption), and lower the gearing and you are set...

Again, I don't know which car engines might also be efficient... im open for suggestions here ...

Bikes are not geared towards fuel saving, so they have really tall gearing, really soft tires (look how much they last 3000miles at the most?!) and their areodynamics are not that great around .37 for a Suzuki Hayabusa (and its considered a really slippery bike).

Get really low resistance tires, lower that .37cd to about .20, add only about 400 pounds or so (which doesnt matter because weight has barely no effect on highway cruising gas consumption), and lower the gearing and you are set...

Again, I don't know which car engines might also be efficient... im open for suggestions here ...

A single cylinder diesel engine coupled to a transmission such as those used on some Royal Enfield motorcycles. If it has to be a gas engine it should be low RPM long stroke small bore.

Q

Here's one that's not quite finished https://www.jalopnik.com/cars/alterna...own-335325.php
It's a DIY lightweight 3 wheeled diesel-electric hybrid. Even if you don't buy the plans for this one it'll still give you some ideas.

I would start with a small Common Rail Diesel with Piezo Injectors. It would have a VVT (Variable Vane Turbo) to give the power (read Torque) you need.