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Old 01-09-2017, 03:16 AM   #2 (permalink)
redpoint5
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Hi and welcome to the forum. I like that you are involved in improving fleet efficiency because it has the potential to make a big difference.

You probably already know this, but I'll state it for the benefit of anyone else that doesn't; heat is what powers an internal combustion engine. Burning fuel creates hot gases that want to expand, and this exerts pressure on the pistons to move.

1. HHO (2 hydrogen and 1 oxygen molecule burn to form heat and water) merely replaces some of the diesel that would be used to generate the heat needed to move the pistons. The reason this isn't efficient is because hydrogen costs more per BTU than diesel. In fact, commercial hydrogen is derived from petroleum products. In other words, to get hydrogen, you have to remove the carbon from petroleum, and that takes energy. What you are left with is less energy than if you had simply burned the petroleum in the first place.

I'll stop here and say go for it if there is little to no risk. I would caution that you should not rely on any measurement devices that the HHO suppliers might provide you. Do your own measurements with your own gauges and factor in all of the expenses to determine the true cost per km driven.

Natural gas is promising because it's the cheapest cost per BTU at the moment. It may even promote combustion efficiency when used in combination with diesel, however I'm no expert on the subject.

2. Unfortunately, improving engine efficiency often entails boosting top end power. As you point out, this means you must somehow limit output power, possibly through tuning, or risk placing undue stress on the drive-train. De-tuning may also undo any efficiency gains.

3. I don't know enough about water injection to have a strong opinion about it. It does seem there is potential for boosting efficiency, but then you have yet another tank to fill. BMW has implemented water injection, but the engine has to be designed for it. You can't just take a normal engine, inject water, and expect efficiency gains. The gains come from boosting effective compression ratio (either through a higher compression ratio, or from increasing turbo boost).

4. Aerodynamics will likely be the best bang for the buck. These improvements are a 1-time fixed cost. Everything you mention should help; some things more than others. Vortex generators likely won't be much help. They improve efficiency by keeping airflow laminar (attached to the surface). If you were to place a vortex generator at the very back of a trailer for instance, it would be pointless (and actually cause more drag) because there is nothing for the air to attach to beyond the end of the square trailer. It's no substitute for having the proper shape to begin with.

5. I'm not familiar with how hydraulic fans work, but electric fans are not very efficient. Electric fans require mechanical energy from the engine to turn an alternator to make electricity, which is then turned back into mechanical energy when the fan is on. It's not efficient to change forms of energy, so it's best to directly use mechanical energy to turn the mechanical fan. If the hydraulic fans are like power steering in that they always pump even when not needed, then maybe electric fans would be more efficient.

Power steering might benefit from not running the pump all the time. Steering is rarely needed, so eliminating a pump that is always running should improve efficiency.

I'm guessing the APU you're talking about is for the refer. Does that mean the cab gets cooled by the APU, which must run at all times anyhow? That sounds efficient, though negligible.

6. I have zero knowledge about the risk / reward of running super singles. My guess is that some routes with lower risk of blowouts, or lower costs when a blowout occurs, are worth running super singles. Risky routes, or those which have a high cost if a blowout occurs might not recover those costs in fuel savings. You'll probably need to trial this. Perhaps there is data available to help you make the decision?

Suggestions

Only test 1 modification at a time and record as many of the variables as possible. If more than 1 modification is done at once, there is a risk that 1 of the mods produces a large gain, and another mod causes a small loss. That loss would be masked by the larger gain of the other mod, and not only could you be getting better efficiency, but then you have the expense of implementing the mod that negatively affects economy.

Focus on aerodynamics, and then rolling resistance. The majority of fuel consumption is spent overcoming aerodynamic drag, so this should be the main focus, especially since buying a fairing is much cheaper than modifying an engine, supporting another fueling infrastructure, and maintaining all that equipment.

Now I'm curious, do they make TPMS (Tire pressure monitoring system) for tractor/trailers? It seems important for fuel efficiency, safety and avoiding blowouts. I would think they could have a decent ROI.

The best ROI might be in the driver. I've always wondered if there was some way to incentivise drivers to be efficient. It seems crazy to me that most drivers are paid by the distance they travel. This would give them incentive to drive faster but perhaps it's more profitable to have a faster turn around time? There has to be a trade-off between fuel consumption costs and being able to make more runs with a truck.
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Last edited by redpoint5; 01-09-2017 at 03:25 AM..
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