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Heated intake air and fuel

Plumbing exhaust gasses to run through the intake manifold
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Here's one for you.

A couple of years ago my father and I were given the task of moving an old bulldozer (D2?). Of course the easiest way to move it was to start it and drive it. But it hadn't been started for ages. It had a petrol V-twin starter motor with a clutch to get the big diesel spinning. To aid starting in cold start conditions the exhaust for the petrol engine went through the inlet manifold of the diesel. Initially (until the diesel had been started quite a few times) the only way to start it was to drip petrol onto this hot exhaust pipe, instantly evaporating it and providing a slightly more explosive charge than the diesel alone.

The point is that the hot pipe in the inlet manifold completely evaporated the fuel without ever igniting it, and it did it quickly.

I propose a radiator style device in the inlet manifold of a carby or TBI car (with exhaust running through it) that completely evaporates all of the fuel. Providing man-sized fuel economy gains and much less toxic emissions from the engine.

Obviously outright power would be lost through reduced charge density and the airflow restriction, but when the average faimily car only need 17hp at the wheels to cruise at 100km/h, the drop from ridiculously overpowered (220hp) to needlessly powerful (170hp) isn't that great.

thoughts?

Ben

BLSTIC, May 20 2008

Boiled Gasoline Engine Boiled_20Gasoline_20Engine
same idea, ish [afinehowdoyoudo, May 20 2008]

[link]






       While it's ideal to have your fuel well mixed with your intake air, I don't think it's ideal to have you intake air hot. Maybe you can mix the fuel and air, then cool it back down again?
phoenix, May 20 2008
  

       Maybe try renaming the idea?.. to reflect the fact that the heat is meant for the fuel, not the intake air. Maybe redundant with link?
afinehowdoyoudo, May 20 2008
  

       I can't actually see a problem with having hot intake air, aside from the reduced power output. You would need a higher manifold pressure for the same power, reducing pumping losses.   

       I'll rename it, but the same theory applies to port fuel injection, with the hot air aiding vaporisation (and so fuel consumption and emission).   

       I don't think the boiled gasoline is nearly the same idea, but the author hints on it by mentioning mixing it in the carby (ever heard of the pogue carbies?).   

       I guess one way to prove the idea would be to wrap a fuel line around the exhaust in order to boil the fuel. I have some experimenting to do when I get a car I can experiment with.
BLSTIC, May 20 2008
  

       [copro wonders why his turbo-charged car has an "intercooler"]
coprocephalous, May 20 2008
  

       That's because Copro's car is geared at the other end of the balls-to-the-wall performance and fuel efficiency scale to a car fitted with this idea.   

       Fuel efficiency and performance aren't completely at odds, but sometimes (ie intake temperature) you need to make compromises.   

       Ever wondered what the winter setting on all those carbied cars actually did? Drew air from near the exhaust manifold so it would vaporise better. There are two reasons they didn't do this all the time: vapor lock and performance. I have also seen a partially melted air filter.
BLSTIC, May 20 2008
  

       //That's because Copro's car is geared at the other end of the balls-to-the-wall performance and fuel efficiency scale to a car fitted with this idea//
My one-and-a-half-tonne car does 0-60 in under 9 seconds, but my mpg indicator is currently sitting comfortably past the 50mpg mark.
What would I have to trade using this idea?

sp."ridiculously", "device"
coprocephalous, May 20 2008
  

       Yeah I'm using a laptop with an oversensitive mouse touch pad (and I don't know how to adjust it). It is easy to accidentally put a letter in the wrong space and then not notice where it is.   

       I have always spelt ridiculous wrong...   

       What kind of car do you have? What kind of technology does it use (apart from the turbo)? And what fuel are you running it on?
BLSTIC, May 20 2008
  

       Sub-two litre 16 valve, six-speed box, running on diesel.
I should have said the 50+mpg was on Imperial gallons, but you wrote "petrol", so I guess we're on the same side of the Atlantic.
50+ on weedy US gallons would've been seriously impressive.
coprocephalous, May 20 2008
  

       40+ mpg ain't nuthin' to sneeze at.
FlyingToaster, May 20 2008
  

       Yeah. Considering my car averages about 25-30usmpg (I think, 7l/100km anyway) on the highway. It weighs in at 1550kg (3200lb?) and has a 4 litre petrol engine. It's a seriously good highway cruiser, even if it does use a tad too much fuel (around town fuel economy gets to 17l/100km).   

       Diesels have always been more thermally efficient at light loads. It has a lot to do with the expansion ratio (or geometric compression ratio) advantage they have over petrols. They would also probably not benifit nearly as much from a heated intake in normal running.   

       Just for reference, what is 10L/100km in your mpg?
BLSTIC, May 20 2008
  

       23.52145833333333333333...   

       and kudos to M$ Calculator+
FlyingToaster, May 20 2008
  

       Is that U.S. mpg or normal mpg?
BLSTIC, May 20 2008
  

       //Just for reference, what is 10L/100km in your mpg?// In Imperial gallons is about 28.25mpg.
I get between 5.3 and 6.5.
coprocephalous, May 20 2008
  

       [BLSTIC], are you proposing that evaporating the fuel will result in more complete combustion, and thus better fuel economy?   

       As I understand it, modern engines are able to burn almost all the fuel they consume, so you can't significantly improve efficiency by dialing up combustion.
FishFinger, May 20 2008
  

       [BLSTIC], I think you may have been a bit impatient on starting the old D2. "Quickly" is not something that even applies. You're used to starting a car, where you can't run the starter motor for more than a few seconds. On the bulldozer, you start the pony motor, get the diesel turning over, then wander off and find something else to do for anywhere from 10 minutes to half an hour. When you come back, the diesel should be warm - cooling lines warm to the touch - then you open up the fuel valve for the diesel. If it's not warm yet, wander some more.   

       I wouldn't expect a D2, in cold weather, long neglected, to be fully awake in less than a couple of hours.
lurch, May 20 2008
  

       Who promulgated the idea that somehow the major inefficiency in I.C.E.s was getting the fuel to vaporize? Heating the air/fuel mixture is baked (numerous ways) to improve emissions (not power) and heating the intake on hard to start engines is also well baked (in a narrowly avoided pun). This idea genera is misguided in failing to realize that the combustion chamber is usually (especially at full load) hot enough and turbulent enough to vaporize and distribute even a solid stream of fuel injected directly onto the piston crown. ARGH!
WcW, May 20 2008
  

       <Runs into pun that [WcW] just swerved round without signalling>   

       OUCH !   

       The charge cooling provided by the fuel absorbing energy as it converts from droplets to vapour is actually useful, as long as it doesn't cause icing in the intake. No need for preheating until that starts to happen - that's why piston engine aircraft have a CARB HEAT lever for use on circuit and approach.
8th of 7, May 20 2008
  

       I believe it was the p55 mustang that lacked such provision forcing the pilot to occasionally manually advance the timing to the backfire point to de-ice the carb throats.
WcW, May 20 2008
  

       No, that was ice accumulating in the throat of the external air intake, not in the carb itself. The C-47/DC-3 could suffer the same problem under some conditions.   

       Most were eventually equipped with heater kits as a retrofit. The backfire is produced by losing some height, revving the engine and then leaning the mixture right out. The problem with the Merlin fitted to the P-51 is that the backfiring can blow up the supercharger, which is unpleasantly loud and expensive.
8th of 7, May 20 2008
  

       Leaning the mixture does make more sense and it doesn't look like they had a timing control in the cockpit (start lever?) so it would have to be the mixture knob. cheers!
WcW, May 20 2008
  

       FishFinger   

       Although all of the fuel is burnt in a modern engine, a lot of the fuel is still burning when the piston reaches bottom dead centre, and small amounts when it reaches the cat converter. The idea is to get the burn over and done with faster. You end up with higher combustion pressure (and so temperature), less ignition advance is required, and lower EGT. Which is surprisingly enough what happens with direct injection, high swirl heads, etc. All technologies aimed at improved combustion.   

       Lurch, don't think for a second that we weren't there for 45 minutes (cranking for perhaps half to three-quarters of that) before using petrol. It should be noted that that particular dozer now starts with around 10 seconds of cranking.   

       Cold weather doesn't exist in far north Queensland (Australia).   

       I find it hard to believe that combustion chambers are hot enough to vaporise a solid stream of fuel. Otherwise annular discharge carburettors (which are proven to provide gains in power, economy, and driveability) would be of no benifit. They might vaporise it enought that something can be burnt, but the BSFC (fuel used per power unit produced) would be horrible.   

       I hope everyone reading this realises that I am quite happy to acccept the power loss caused by a device such as this, in exchange for fuel economy.
BLSTIC, May 20 2008
  

       Dudes, Smokey Yunick did this back in the 80s in either a Pantera or a Fiero, I can't remember. He preheated the intake air with the exhaust to 425 degrees, and atomized the fuel. It ran like a bat out of hell, and I believe, was just as hot. He wrote about it in Hot Rodding or Hot Rod. He said it would cook the head in no time in traffic, I think, but the efficiency was amazing. Safety engineers still have hair standing up on the backs of their necks...
plynthe, May 21 2008
  

       Yeah, he also went to the trouble of patenting a whole engine design.   

       He started out with some kind of 3cyl engine, used a suck through carbie turbo system with multiple exhaust fuelled heaters, and got huge efficiency gains and thanks to the turbo, no power loss.   

       His engine was called the adiabetic (sp?) engine, and to add confusion he called the turbo an exhaust driven homogeniser.   

       However I don't think any alloy headed engine is capable of running at the coolant temperature required.
BLSTIC, May 21 2008
  

       // adiabetic //   

       "adiabatic"..... the Carnot cycle.   

       In theory, if you make your block and head from ceramic - which can withstand the temperature - then you can do it; but you still have the problem of erosion of the bore contact surfaces, because of the high temperatures and the fact that hydrocarbon lubricants won't function at those temperatures.   

       Making the system of refractory metal, thin walled, with liquid metal cooling, would be the next option but it doesn't address the lubrication problem.   

       Get the materials science right and it can be done, but a gas turbine is probably a better option.   

       If yu build a 2-stroke engine, you could cast the cylinder and head as a single piece - no head gasket, no seals to fail - and with total loss lubrication, you might get away with it.
8th of 7, May 21 2008
  

       I believe the "faster burn" that everyone is looking for has a technical name. Hmm... Knocking , Pinging, no... Ah yes: detonation! Burn the fuel faster and the engine needs to turn faster. The complete elimination of waste HC has been the goal of automotive designers since the days of zero overlap camshafts. A basic understanding of resonance and the dynamics of an engine whose load varies wildly and you realize that 0% HC loss is impossible in an ICE. Since nowadays a 15% increase in fuel economy can well yield a more than 15% increase in sticker price don't for a moment imagine that the designers and engineers at automotive firms don't lie awake at night puzzling over new ways to improve combustion efficiency. I have read many of Smokey Y.s books and never was related to any technique other than smart manifold design. 425 degrees on one side of a manifold does not equal 425 degrees on the other side where 450hp worth of fuel is being vaporized.
WcW, May 21 2008
  

       sounds like this is a job for a Crower cycle engine (addition of a passive water>steam stroke)
FlyingToaster, May 21 2008
  

       finally a voice of reason.
WcW, May 21 2008
  

       //finally a voice of reason//
What the hell is that doing in here?
There really is no call for that sort of thing.
AbsintheWithoutLeave, May 21 2008
  

       //What the hell is that doing in here?//   

       well, I do want to add an oxygen concentrator on the front end, if it's any consolation.
FlyingToaster, May 21 2008
  

       [BLSTIC], you needn't rename your idea just cause I suggested it.. I thought you really meant to heat only the fuel and not the air.   

       [WcW], I believe that the faster burn = better efficiency idea has merit. Just because an engine can burn most or all of the fuel that goes through doesn't mean its making the best use of it. Think of the fuel that is still burning near BDC, or that burns in the catalytic converter. Ask yourself why engine power, efficiency, and exhaust temperature all rise as the mix is leaned out. Doesn't make any sense in the context of the "IC-engine-burns-real-good" theory. As for knocking, pinging, aka detonation: yes too much pressure is bad, but if detonation can be made to occur reliably and the amount of fuel reduced then the engine will run just fine.. on less fuel.
afinehowdoyoudo, May 22 2008
  

       actually there is a massive difference between a 'normal' burn speed and detonation.   

       For arguments sake we will say the flame speed that we call detonation is 1000fps. Then the flame speed in most cars ranges from 100-200fps.   

       We can burn the fuel a lot faster before it gets to detonation, even if the difference isn't as big as I stated above.   

       Some basic maths for people:   

       An engine running at 3000rpm has 750 power strokes per minute, or 12.5 per second (per cylinder). Each stroke lasts about 0.08 seconds. However you want peak pressure at about 14* after TDC (or thereabouts), which gives you about 6 milliseconds to get all of the fuel burnt, from the time the piston is at tdc. Not much time really... Hell even the full 80 milliseconds (for the whole stroke) isn't very long.
BLSTIC, May 22 2008
  
      
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