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Hemmings Motor News Blog

Hemmings Motor News has been around since 1954. We're proud of our heritage, but we're also more than the Hemmings full of classifieds that your father subscribed to. Aside from new editorial content every month in Hemmings, we have three monthly magazines: Hemmings Muscle Machines, Hemmings Classic Car and Hemmings Sports and Exotic Car.

While our editors traverse the country to find the best content for those magazines, we find other oddities related to the old-car hobby that we really had no place for - until now. With this blog, we're giving you a behind-the-scenes look at what we see and what we do during the course of putting out some of the finest automotive magazines you'll ever read.

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22 comments

The Car With the Rooftop Exhaust System

Posted November 25, 2008 12:01 AM by dstrohl

Is the exhaust system really optimally placed underneath the car? Think about it - heat rises, and excessive heat, as from hot exhaust pipes, damages paint, undercoating, fiberglass, even sheet metal. Plus, the potential for damage from road debris is greater underneath the car, and should an exhaust pipe become crimped, it'll choke the engine.

So why not put the exhaust pipes above the car, as Sbarro did with the 1978 Windhound, built on a Mercedes G chassis? I mean, other than the visual obstruction and the potential for burning yourself, it's an ideal location!

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#1

Re: The Car With the Rooftop Exhaust System

11/25/2008 1:42 PM

I don't know about you, but if I was a pedestrian walking past your car at idle, I certainly wouldn't want a faceful of hot exhaust gases and pollution smack in the eye!!

Would you?

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#2

Re: The Car With the Rooftop Exhaust System

11/25/2008 11:03 PM

Ha ha ha ha ha ha ha ha!

So many bad ideas and so little time to point out what is wrong with them!

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#3

Re: The Car With the Rooftop Exhaust System

11/25/2008 11:06 PM

I am of the opinion that (in the developing countries at least), the exhaust pipe should be placed directly infront of the front wind shield, so that driver (who are not conscience about pollution they are creating) will always be careful about polution and engine condition.

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#4

Re: The Car With the Rooftop Exhaust System

11/26/2008 2:03 AM

Why not insulate the pipes. Run them to a sterling engine and recover some of that lost energy.

Brad

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#5
In reply to #4

Re: The Car With the Rooftop Exhaust System

11/26/2008 3:00 AM

Ha ha ha ha ha ha ha ha!

So many bad ideas and so little time to point out what is wrong with them!

Sorry UV, but I just couldn't resist!

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#6

Re: The Car With the Rooftop Exhaust System

11/26/2008 11:35 AM

I'd love to have that jungle yacht. Looks like I'd have a little trouble swinging it into the driveway though.

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#7
In reply to #5

Re: The Car With the Rooftop Exhaust System

11/26/2008 11:52 AM

No problem rcapper,

I've never understood why we use an alternator when we waste so much heat from an IC engine. Drop 20 to 40 lbs and 2-5 % parasitic load. The Stirling was just to show a alternate idea. (pun intended)

Brad

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#8

Re: The Car With the Rooftop Exhaust System

11/26/2008 2:13 PM

I'm going to point out one of the bad ideas, though it is neither in the vehicle design, nor in the suggested use of a heat engine to recover exhaust energy elswhere in this thread.

"Think about it - heat rises . . ." This is simply not true. Yes, heated AIR rises due to density change relative to the unheated surrounding air - but within the pipes, this is of no consequence. I once worked for a man who tried to explain how to solder electrical connections, and wanted me to hold the soldering iron on the underside of the printed circuit board based on this belief (all through-hole components, back then). I gave him my best withering look, and asked how heated air was to get from the lower surface out to the edges and back again to help the process go more quickly (as he claimed that it would), and comprehension finally dawned. I never again heard him try to convince the technicians to use this incredibly clumsy idea [imagine trying to do it with today's fine-pitch surface-mounted components and multi-layer boards!]. Back in the 1940s, when he learned to solder, applying a blowtorch flame from beneath a pipe fitting may have been advantageous, but he'd never thought about the physics involved, despite having earned two college degrees in the sciences afterward.

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#9

Re: The Car With the Rooftop Exhaust System

11/26/2008 2:22 PM

Should route exhaust inside car to keep drive warm.

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#10
In reply to #7

Re: The Car With the Rooftop Exhaust System

11/26/2008 2:31 PM

Congratulations, you partly answered why a sterling after engine is a bad idea. The additional weight, including the controls and torque motor or however you might arrange to put what power you were able to extract from waste heat into the power train in a useful manner, would in all likelihood wash out the energy you could capture. In a practical world the Carnot efficiency is proportionate to the temperature differential due to energy leaks so what you could extract is dubious.

However there are many "alternatives". Paste thermopiles all over the engine and exhaust. Put a turbine in the exhaust.

The reality is that the IC engine does a reasonably good job of getting a large portion of what's there out and what is left is hardly worth messing with via other means than making the IC engine more efficient.

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#11
In reply to #10

Re: The Car With the Rooftop Exhaust System

11/26/2008 4:52 PM

Thermopiles, last I knew, were very low efficiency.

A turbine in the exhaust causes back pressure, lowering efficiency.

You still need the windings in any case to convert the motion to electricity.

12 volt thermopiles are starting to be made more for portable coolers/refrigerators. A forty deg F drop in temp advertised. I have no idea what the reverse output would be. May have to tear one apart and find out. I suspect that the weight savings may be moot. The parasitic load is a different story.

Brad

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#12
In reply to #11

Re: The Car With the Rooftop Exhaust System

11/26/2008 6:20 PM

See, now you're thinking in the right direction! They are pretty much all bad ideas for one reason or another.

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#13
In reply to #9

Re: The Car With the Rooftop Exhaust System

11/26/2008 9:55 PM

I hope you mean EXHAUST PIPE. Otherwise, you will have to practice breathing CO, CO2 and what not!

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#14
In reply to #12

Re: The Car With the Rooftop Exhaust System

11/27/2008 3:54 PM

Not All rcapper. That is a limiting thought process. There is a way, technology or mind set may not be ready for it.

Here is a far ahead thought. Carbon nano tubes attached to piezo crystals lining an over sized exhaust. on the inside. The sound wave pulse is the power source. The scavenging action of the pulse would need to be completed before the start of the piezo action.

Brad

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#15
In reply to #14

Re: The Car With the Rooftop Exhaust System

11/27/2008 10:00 PM

I don't know guy, you're just one step away from putting a propeller on top of the car to harvest the "free" energy from the wind.

All the energy comes from the IC engine. The most ahead thinking, IMHO, is to work the best conversion in the first conversion. Every layer away you get infers inefficiencies going both directions (30%*30%=9%) which is like rowing further down stream in order to row upstream.

And the other reality with which you have to contend is the economics of adding additional systems that are expensive, complex and require maintenance $$$.

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#16
In reply to #15

Re: The Car With the Rooftop Exhaust System

11/27/2008 11:37 PM

Sorry rcapper no such thing as free energy. Even a bolder on a cliff takes a push to start and that does not include all the processes it took to get there. One can make use of energy when one can recognise the potential and reasonable extraction.

The propeller on the roof of a car is only useful to test a second propeller on the roof as a standard to limit changing conditions from run to run.

The exhaust pulse generator would not work because soot in the exhaust would clog it.

There are several brake threws in mechanical engineering that could lead to small efficient (as in more efficient than piston engines) turbines for cars.

Many things that would lower our energy consumption are not in the best interests of industry. Texas Instruments in the early 90's developed a dirty silicon solar cell. Very inexpensive, made from sand and just efficient enough to run the average US house by covering the roof of the house. This was announced in TI's internal newspaper with many details. Many months later when TI employees tried to find out more they were politely and firmly told to drop it.

If the product was a failure then it had failed after working systems were being prepped for production. If a patent issue, some entity holds the key to cheap house based energy.

Over course there are two sides to every coin and then there is the edge.

Brad

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#17
In reply to #16

Re: The Car With the Rooftop Exhaust System

11/28/2008 12:05 AM

UV,

I like your thinking and I too am tired of the naysayers.

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#18
In reply to #17

Re: The Car With the Rooftop Exhaust System

11/28/2008 5:56 AM

Well then if you're so tired please let me know when you have a great success. No matter how "open minded" you believe you are, nothing is going to happen because you aren't actually going to make any of your ideas a marketable product. There aren't any people who are actually making products that would be making any of your ideas just because they are "naysayers" or to stupid or unimaginative.

I have over the years developed real products that are out there in the real world that have and are saving millions of btu's of real energy on a daily basis. Measurable documented energy savings in the real world. Because someone and because I had the imagination to do so.

And because I didn't waste my time sitting around making lofty suggestions in the hope that someone would open their mind and save us all with my wonderful ideas.

I'm tired of all these "naydoers"! People that just talk and want to accuse of others of being negative when in fact they have accomplished nothing but make unworkable suggestions from the sidelines.

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#19
In reply to #18

Re: The Car With the Rooftop Exhaust System

11/28/2008 9:33 AM

Well said rcapper - GA!!

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#20
In reply to #18

Re: The Car With the Rooftop Exhaust System

11/28/2008 11:48 AM

Touche!

Did your products fall from the sky then or did they not start with some thinking? It appears that you had some benifit that others might not have. Even just the ability to make things happen is a gift.

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#21
In reply to #1

Re: The Car With the Rooftop Exhaust System

12/03/2008 4:37 PM

It is not unusual at all for Diesel trucks & Tractor Trailer rigs to exhaust from vertical pipes, or smoke stacks. Reasons for that are fairly obvious. Years ago I remember reading of a Beech Bonanza that had achieved from exhaust pipe redesign enough thrust to increase the speed of the aircraft by 3 miles per hour. At 60 miles an hour a small wind powered generator may well be practical for battery charging of a battery powered car. The point at which a system or device becomes practical depends on a variety of factors and the overall use of the machine. In one case the design is practical, and in another it simply isn't. Electroman is absolutely right that the car pictured would be obnoxious in a city environment.

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#22
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Re: The Car With the Rooftop Exhaust System

12/03/2008 5:25 PM

"At 60 miles an hour a small wind powered generator may well be practical for battery charging of a battery powered car."

Not true. A recent thread has explored this in considerable detail, and the multiple losses involved in this concept guarantee that it will always be impractical. ANY loss in getting the motor power to the ground, converting relative wind into mechanical energy [via turbine, blades, sails, fan - it does not matter which], getting that into an alternator or generator and converting again into electricity, changing electrical power into a form suitable to charge the batteries, the system's less-than-unity charging efficiency, storage losses, bearing friction, and resistance in the wires and other components absolutely guarantee that you will lose on the overall result: you'd have been better off to simply leave the batteries' energy where it was and use it to power the car directly. Period.

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