
San Antonio man has engine that gets 100 mpg - coreyp_1
http://www.khou.com/features/san-antonino-man-has-engine-that-gets-100-mpg/242673922
======
userbinator
_This recycling feature boosts the engine 's efficiency to a whopping 50
percent. For comparison, a standard internal combustion engine operates only
at 14 percent efficiency._

I don't know what a "standard internal combustion engine" is, but 14% is
absurdly low. Maybe a Ford Model T would be around there? A glance at

[https://en.wikipedia.org/wiki/Specific_fuel_consumption_(sha...](https://en.wikipedia.org/wiki/Specific_fuel_consumption_\(shaft_engine\)#Examples_of_values_of_BSFC_for_shaft_engines)

shows efficiencies of ~30% for typical gasoline engines of the automotive type
(which agrees with what I remember when I studied this stuff), and closer to
50% for large two-stroke diesels.

~~~
gameofdrones
The most efficient fossil fuel-based engines are massive two-stroke diesels
found on extremely large ships and in some peaker power gensets which
currently have efficiencies just over 51% and BSFC's over 275.

[https://en.wikipedia.org/wiki/Brake_specific_fuel_consumptio...](https://en.wikipedia.org/wiki/Brake_specific_fuel_consumption)

In this case, he may have matched the performance of very large engines, which
have the advantages of optimizing for scale, but time will tell whether this
solution can deliver.

~~~
semi-extrinsic
> The most efficient fossil fuel-based engines are massive two-stroke diesels

Unless you count combined-cycle gas turbines (also found on big ships and
powerplants), which can squeeze above 60% efficiency.

------
chrischen
> "Josh “Mac” MacDowell says he not only has the engine, he has come up with
> an idea, strong enough the U.S. patent office has given him a patent for
> it."

Gave me a chuckle.

~~~
johnloeber
A worthy submission to the "Found Prose" subsection of the Little Lytton
Contest...

------
strommen
As usual, Tom Murphy has a great top-down analysis of why cars don't get 100
mpg:

[http://physics.ucsd.edu/do-the-math/2011/07/100-mpg-on-
gasol...](http://physics.ucsd.edu/do-the-math/2011/07/100-mpg-on-gasoline/)

Spoiler alert: it's mainly because cars are shaped like cars, not fish.

~~~
walrus01
[https://en.wikipedia.org/wiki/Volkswagen_1-litre_car](https://en.wikipedia.org/wiki/Volkswagen_1-litre_car)

aerodynamics on a car taken to the extreme, to the extent that it has cameras
and LCDs instead of side/rear view mirrors.

------
patrickg_zill
It should be possible in terms of energy expended.

This guy : [http://diesel-
bike.com/Centurion/urba_centurion.html](http://diesel-
bike.com/Centurion/urba_centurion.html) built a kit car from these plans :
[http://www.rqriley.com/cent.html](http://www.rqriley.com/cent.html) and got a
tested and verified 200mpg after tuning (scroll down the circa-GeoCities page
to see the results from his participation in the Toyota Green Prix).

Not sure the car above would be good as a daily driver, however.

------
engx
What happened to Dean Kamen's Sterling engine?

Here's one link from 2013- [http://www.greentechmedia.com/articles/read/nrg-
energy-deplo...](http://www.greentechmedia.com/articles/read/nrg-energy-
deploying-dean-kamens-solar-smart-in-home-generator)

------
gonyea
Uh, wat. Honda engines are insanely efficient. I doubt this guy knows anything
that Honda/Toyota doesn't.

Honda could easily give you a 100mpg car, if it weren't for those meddling
kids at the NHTSA. Damn them and their stupid, heavy airbags|crumple
zones|roll cages.

~~~
jackmott
Removal of that weight would not be enough to hit 100mpg, as evidenced by the
fact that steady state cruising does not get you 100mpg

~~~
gonyea
I forgot that this was Hacker News, where "Serial Entrepreneurs" moonlight as
leading experts in automotive engineering.

~~~
WayneBro
Right, so you're an expert in automotive engineering then?

~~~
gonyea
Expert? No. But I did work with many industry experts while at Honda. I've
heard plenty on the topic of engines/mpg.

Thanks for playing!

~~~
WayneBro
Oh, so you're not an expert at all by your own admission, but you won't listen
to anybody else who is also not an expert.

I'm so sorry to inform you of this but, you actually lost the debate here.

~~~
gonyea
Weak straw man. You're terrible at making arguments.

Shoo.

~~~
WayneBro
Replying to every little rebuttal that I make only makes you look worst.

Shoo yourself.

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swampthinker
Alright, someone who knows more about this topic tell me the catch to this.

~~~
CapitalistCartr
Without knowing the test conditions, torque and other performance results, the
lone number of fuel milage is worthless. Stirling engines are usually big,
heavy suckers, better for fixed installation than vehicles.

~~~
Vendan
meh, totally false. There have been prototype cars before that use stirling
engines, the main flaw has been slow start times and poor speed change (it
takes a while to heat up, and for changes in heat to take effect). Making it a
hybrid solves both of those problems!

------
jackmott
Since no article has mad it clear, what is providing the heat source here for
the Stirling engine? Is he pumping the heat from a standard gasoline engine to
the stirling engine, is that the idea?

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dmolony
That was a lovely bed-time story. Unfortunately, that's all it was.

~~~
aplummer
Can you please explain why?

~~~
khedoros
They probably mean that it's like the stories about 100x battery capacity
improvements that end up as a 20% capacity boost in actual products that
appear on store shelves. Prototypes are always more impressive than marketable
products.

In his case, maybe there are acceleration/deceleration issues, maybe the
engine would be cost prohibitive for manufacture, or maybe he'll have to
modify the vehicle itself to achieve the 100mpg number. The point is that
there's likely to be some constraint that makes it impractical.

As an extreme example: [https://en.wikipedia.org/wiki/Pac-
car_II](https://en.wikipedia.org/wiki/Pac-car_II)

There's a reason that we aren't driving hydrogen fuel cell cars with 12,600
MPGe fuel economy.

------
CapitalistCartr
He made a hybrid with a Stirling engine, hence the 200-year-old technology
part of the clickbaity headline. It looks fascinating. Unfortunately, the
article is almost completely number and depth free.

~~~
carn174s
Yes, that's because Fox News.

...at which point, you might ask yourself "Fox News? On _MY_ HN?!"

~~~
fabled_giraffe
Note to others- he wrote that because the original link on this post was
foxnews, but the new link is more well-written and from KHOU, a CBS affiliate.

------
re
The source article is much better: [http://www.khou.com/features/san-antonino-
man-has-engine-tha...](http://www.khou.com/features/san-antonino-man-has-
engine-that-gets-100-mpg/242673922)

The DigitalTrends rewrite omits a lot of details and doesn't add anything.

~~~
DrScump
Attention dang: an appropriate replacement?

~~~
dang
Sure, we changed to that from [http://www.foxnews.com/leisure/2016/06/15/man-
builds-100mpg-...](http://www.foxnews.com/leisure/2016/06/15/man-
builds-100mpg-engine-using-200-year-old-technology/). It has an annoying
autoplay video, but if the article is better that's enough.

------
hugh4
An engine doesn't get 100 mpg, a vehicle does.

Attach it to a normal-sized vehicle and get 100 mpg under realistic driving
conditions, and I'll be impressed. ('til then I'll be internet-snarky!)

~~~
emptybits
The fifth paragraph addresses the significance of your point.

I'm skeptical, but I applaud him for making public a very specific and short-
term goal that we can all watch: coast-to-coast USA on 40 gallons of fuel in a
small SUV.

~~~
developer2
>> coast-to-coast USA on 40 gallons of fuel in a small SUV

Without having a source, I suspect a caveat wherein he will plug in to fully
recharge the electric battery every X hours, which would be _far_ less
impressive.

Now, if this is cross-country, on a single 40 gallon tank, without plugging in
to recharge, in an SUV that is not gutted to reduce the vehicle's weight...
that would be impressive.

~~~
emptybits
> > Without having a source, I suspect a caveat wherein he will plug in to
> fully recharge the electric battery every X hours, which would be far less
> impressive.

FTA, FWIW: "McDowell is using a Stirling engine, coupled with thermopile
technology to make it possible to drive a Hybrid electric car and never have
to stop to charge it."

~~~
developer2
Ah, thanks for that. I read the article fully, but apparently missed or forgot
about that line in the first paragraph.

My intuition was that the Stirling engine would _partially_ recharge the
battery while it runs. If it can truly keep the battery fully charged, that is
quite awesome. Time will tell. :)

