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TOPIC: Hot air box over exhaust Manifold to assist groove to vaporize fuel

Hot air box over exhaust Manifold to assist groove to vaporize fuel 24 Jul 2020 06:39 #1

  • neil
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This is a hot air box I made years ago (had trouble finding it!) fitted to a inline 6 cyl motor. It was easy to make and was secured with threaded rod protruding from threads in the cast iron exhaust manifold and two tags at the top that went under some of the tappet cover bolts. It was not sealed that well but getting 180 degrees Fahrenheit was easy. The hot air supply was drawn from towards the back of the motor and I simply plumbed that into the air cleaner.
Another interesting and probably not related matter (but might be cos we don't know much about why 100mpg was possible with vaporization systems) is that I was heating the intake air to get a "fast burn" using propane as the fuel (LPG has been very popular here). I was following the idea after seeing two different chemical equations for propane.
The "slow burn" equations main difference was that it needed more fuel to get a complete burn, by going to a fast burn the chemistry actually changes and less fuel is required. It was also said extra power would be made in the "fast burn" mode?? Perhaps petrol vapor enjoys something similar?

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Hot air box over exhaust Manifold to assist groove to vaporize fuel 06 Aug 2020 08:23 #2

  • neil
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I have been giving this more consideration and will be looking at how to integrate hot air into a petrol powered, grooved vehicle.
Is anyone else interested in channeling in some warm air down the intake?
What if it is as simple as getting 3 inch flexible ducting and connect it to the inlet of the air filter and have it draw from behind the motor?
Even a mild increase in temperature might be the factor that gets the fuel vaporizing ;working with manifold vaccum, atomisation of injectors and .....of course the groove.
Thats a fourth factor that might make things much more interesting....

So I'm just bringing these comments from Greg back to this subject for ease of following. I have failed in how to connect a link so if anyone else knows how to, please feel free.
Neil - you said "For density of air the calculation is P1 times V1 over T1 equals P2 times V2 over T2." That's a balance equation - one side has to equal the other, so the variables have to be adjusted accordingly. That's what I was demonstrating. or trying to. We know atmospheric pressure and can infer the relative pressure (or measure the difference), we can assume a volume of air, we know the air temperatures. all my math proved is that the density of the air warmed to 70degrees in the hotbox was significantly (13 times!) LESS dense than the theoretical intake air at Standard Temp and Pressure, the point being you CANNOT take pressure out of the equation...and that it's probably the wrong equation to be using. Like Ron has pointed out, it fails to take Mass into account. I think PV=nRT (the Ideal Gas Law) might be the better one...n is molar mass. Mass Air flow sensors "measure" Mass of air in grams/sec, and some of them measure temperature too. Manifold Absolute Pressure sensors help the computer use that equation, and then it's reaction and instrumentation error get tweaked by the result from the oxygen sensor
Greg, Are you saying that warming the air to 70 degrees decreases its density by 13 times? If so please confirm. For clarity I am sticking with about 20% decrease in density which I consider negligible in comparison to benefit of; if it gets fuel vaporisation over the line.
I don't understand why you included manifold vacuum in your equation either.

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Hot air box over exhaust Manifold to assist groove to vaporize fuel 06 Aug 2020 11:27 #3

  • GregK
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It's winter in Australia- your fuel consumption is up/mileage is down, right neil? air temps are cooler, making air more dense. higher density air means that more fuel is being consumed to maintain 14.7:1. further, with denser air, it's harder for the engine to push a vehicle through the thicker air, so still more fuel is getting consumed.

By all means, Neil, give it a go. reusing the waste heat radiated by the engine is an idea many others have experimented with before, but I have faith you can achieve a different result because you're tenacious.

I was trying to show you that regardless of units, your math doesn't work; disregarding pressure won't get you any closer to a correct result either:
Vacuum is negative pressure...and you're continuing to disregard the Ideal gas law PV=nRT. outside the manifold is atmospheric pressure, usually used as the reference for the amount of vacuum. a running engine develops 18 or 20" of vacuum below atmospheric pressure. your pressure times volume divided by temperature only determines the weight of the air (number of moles) times a constant. ignore pressure like you did, and you have a ratio of volume over temperature...liters per degree C for instance.

How about this experiment: blow up a balloon, neil. use your lung power or a pump - doesn't matter. tie the end, and weigh the balloon. got it? that's your molar mass, the n in PV=nRT.
now put that balloon in the fridge or a freezer. come back in an hour or 2. what's happened to the balloon? It will have decreased in size - the volume will have shrunk. Temperature and Volume will have decreased, yet there is still the same amount of air in the balloon - there is more mass per volume unit, meaning it's more dense AND because that volume of air is smaller, it's not exerting the same pressure on the envelope of the container it's in, the balloon, so it will have shrunk.
the same works in the other direction: if you're able to inflate a balloon with air at room temperature, and then heat the air inside the balloon, the balloon will increase in size, possibly to the point that the balloon can't hold it anymore (pop!). (ever seen a hot air balloon flying? it's mass and pressure and volume changes from the addition of heat energy that create the forces to lift it from the ground)

Please let us know how you get on with your experiment

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Hot air box over exhaust Manifold to assist groove to vaporize fuel 12 Aug 2020 11:55 #4

  • GregK
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If you're still following along Neil, I tripped across this webpage in my bookmarks that might help you get some of the math together in your head pertaining to stoichiometry and the universal gas law and equivalence:
Here

Note that it references octane, but our gasoline today (regardless of whether it's evaluated at AKI or RON/MON) is not 100% octane (note the indications of ethanol content or "enhancement" in the fuel you buy - as much as 10% in some places), so the example is from the perspective of laboratory perfection or the ideal. From there comes the disclaimer "Your Mileage May Vary" (along with other factors - we don't tend to drive on test tracks at speeds lower than the speed limit without traffic)

The tack I've taken with significant effect on my own daily driver (beyond the Groove and the associated modifications discussed here on this forum) is water vapour induction on the intake. water displaces air in the intake, but at ignition, the steam expands in greater proportion than fuel. so while it may seem that you get more power from less fuel, the oxygen sensor's signal to the computer controlling fuel delivery must be modified so that the extra oxygen in the steam is compensated for/mooted. I've got my system set to consume about 200mL of water for every 900km I drive (thats about a 68L tankful for me right now, combined city/highway driving). That bit of water has gained me an extra 100-150km range out of my tank of fuel in real-world driving.

with your oxygen sensor disconnected, I expect you plan to tune fuel delivery with the potentiometer attached to the signal wire of your MAF sensor, correct? Why not simply increase the amount of exhaust gas recirculated into the intake with an electronic hack? Maybe this guy can help you get pointed in a direction that works for you/your ride:

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