Pressurising fuel link

[Stuart]

I was sent this link yesterday regarding pressurised fuel & how it increases mpg.
I'll put it out for discussion
http://m.instructables.com/id/Increase- ... air-Disso/

[coachgeo]

Very interesting. For diesel ??? different issues.

1. Moisture from compressed air Good or bad

Im sure there are others

[tappy]

Sounds like an airlock waiting to happen in a diesel engine.
If you pressurise the fuel tank enough that it does absorb more air, then when that pressure is released the air will come out of solution.
So long as the fuel stays under pressure until it gets into the injector then I guess it might be OK?

[alexanderfoti]

I think its pointless. Once the fuel gets to the injection pump it will be presurised anyway, to about 10-15 times the pressure its incoming at, I dont think its a linear change, rather absolute. If you put it at 100 psi at the inlet, it will still only be 120 psi at the outlet.

[Stuart]

It's about adding air to the fuel & injecting less of it, not adding pressure overall.

[alexanderfoti]

Oh, then I completely missed that! On a diesel it runs with an excess of air most of the time anyway, so adding more into the fuel wouldn't help would it?

[Stuart]

Easier to do on petrol I suspect but it would make the burn lean? But this guys talking at microscopic level. I'm not convinced. I'd like to see it proved lol.

[sbrumby]

Quite crackpot, and quite dangerous. Here is my maths or math for those across the pond. A cars tank roughly 2 cubic feet. So 2 X 144X12 = 3456 you may have noticed he does not mention PSI unless i missed it but one picture shows 5psi so 3456 X5= 17280 divide buy 2200 lbs per ton = 7.85 tons. Your tank would look like a football.

[coachgeo]

Quite crackpot, and quite dangerous. Here is my maths or math for those across the pond. A cars tank roughly 2 cubic feet. So 2 X 144X12 = 3456 you may have noticed he does not mention PSI unless i missed it but one picture shows 5psi so 3456 X5= 17280 divide buy 2200 lbs per ton = 7.85 tons. Your tank would look like a football.

In the discussion on the indistructable page psi is mentioned alont. Along with the built in venting he felt 5ps1 was minimal and safe. Alot disagree about many things in that discussion. Interesting read.

[BertTrack]

The idea as i understood is that the higher pressure leads to more air being dissolved into the fuel. When the pressure drops of the fuel (after injection) this air comes out of the fuel and helps the evaporation of the fuel.

It's a principle we see happening at work. We put vessels with solvent (oktene) under nitrogen pressure of 40 bars. First time we do, the system will add extra every now and then until the amount of dissolved gas matches the given pressure. Same when you take the pressure off.

In carburated engines it won't do much because of the float reservoir.
In injection engines it might do something. Probably more noticeable if your injection system isn't exactly squirting well.

As for diesels: It should do something. Diesel fuel also needs to evaporate before it ignites. Increasing the surface will help evaporation and having air bubbles coming out of the liquid increases the surface.

But it's not free energy.

The energy needed to evaporate has to come from somewhere. So the air has to be compressed etc etc. Waste of time/money/effort imo.

Running on fuel fumes is something i like more. No more wasting energy in evaporating fuel just before you burn it.

[tappy]

Quite crackpot, and quite dangerous. Here is my maths or math for those across the pond. A cars tank roughly 2 cubic feet. So 2 X 144X12 = 3456 you may have noticed he does not mention PSI unless i missed it but one picture shows 5psi so 3456 X5= 17280 divide buy 2200 lbs per ton = 7.85 tons. Your tank would look like a football.

Pressure x volume does not equal force, it equals work. For force you want pressure x area. So assume the 2 cubic foot tank 8" deep that gives a roof or floor area of 432 square inches. At 5psi that's 2160lbf, or about 1 tonne. Your point still stands - it's a lot for a fuel tank to resist, but it'd give up WAY before 8 tonnes!

[coachgeo]

The tank is vented though right? if not a fuel line or something will blow off first. As mentioned earlier much of this has or is being hashed/discussed on the instructable site. Nothing wrong with discussing it here as well just look thru that too. That way those who do that will be more informed in their responces here.

[sbrumby]

Discusion is one thing danger is another.