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Student 07 · 12-17-11, 11:46 AM

Hi,

When I last posted I didn't want to get into the engine mods too much because I thought it would be more appropriate for the eco modder forum. But, in hindsight I probably should have been more specific.

I am referring to volumetric efficiency. A normal automobile engine flows only about 80% of the calculated amount of charge. With certain modifications it is possible to have an engine with a volumetric efficiency exceeding 100% at a certain speed. These modifications are usually performed on a racing engine which doesn't require the wide power band that a normal automobile engine does.

I am paraphrasing from a book published by HP books called Turbocharging written by Hugh MacInnes (page #6).

It is possible to optimize an engine’s performance for a generator, since a generator usually stays at a certain RPM. It would be possible to tune the intake and exhaust, port size, valve size etc., to get maximum power at that specific RPM.

If you're talking about the efficiency of converting the energy in fuel to heat, I would agree with AC Hacker that you are generous. For example: a 5hp motor running for one hour would require one gallon of gasoline (114,000btu), but only produce 12,000btu (at the radiator). >10%

If you're talking about the engines ability to convert fuel energy to power you are also correct. One gallon of gasoline contains 36.6kW of energy, a 11hp motor using one gallon per hour, would produce 8.2kW for the hour.

As you say the majority of the energy (heat) is going through the exhaust (a turbocharger recovers some of this energy), there are also numerous other residual losses.

I have had turbocharged vehicles before and it is possible to get plenty of power out of them

. For the generator, it might be a little counterintuitive, but a larger motor may be better. It would have more than enough hp so it could be geared to operate at a lower speed, which should make everything last longer. A large motor operating at a low speed shouldn't use more fuel than a small motor operating at a high speed.

Engine modifications aside: I don't see a co generator being cost effective, unless the motors are much more efficient or it uses a much cheaper fuel source. I don't think a generator would ever be competitive with grid electricity, so the electricity that a co generator produces has to be thought of as a "bonus".

Maybe it is more effective as a heat source. I may need to go back and check my math for the heat output. ~5hp =12,000btu, but over time it may be cumulative and the btu/h may be much higher. More research,

Thanks for the feedback everyone.

12-17-11, 11:46 AM	#6
Student 07 Helper EcoRenovator Join Date: Dec 2011 Location: Gresham OR Posts: 35 Thanks: 0 Thanked 3 Times in 3 Posts	Hi, When I last posted I didn't want to get into the engine mods too much because I thought it would be more appropriate for the eco modder forum. But, in hindsight I probably should have been more specific. I am referring to volumetric efficiency. A normal automobile engine flows only about 80% of the calculated amount of charge. With certain modifications it is possible to have an engine with a volumetric efficiency exceeding 100% at a certain speed. These modifications are usually performed on a racing engine which doesn't require the wide power band that a normal automobile engine does. I am paraphrasing from a book published by HP books called Turbocharging written by Hugh MacInnes (page #6). It is possible to optimize an engine’s performance for a generator, since a generator usually stays at a certain RPM. It would be possible to tune the intake and exhaust, port size, valve size etc., to get maximum power at that specific RPM. If you're talking about the efficiency of converting the energy in fuel to heat, I would agree with AC Hacker that you are generous. For example: a 5hp motor running for one hour would require one gallon of gasoline (114,000btu), but only produce 12,000btu (at the radiator). >10% If you're talking about the engines ability to convert fuel energy to power you are also correct. One gallon of gasoline contains 36.6kW of energy, a 11hp motor using one gallon per hour, would produce 8.2kW for the hour. As you say the majority of the energy (heat) is going through the exhaust (a turbocharger recovers some of this energy), there are also numerous other residual losses. I have had turbocharged vehicles before and it is possible to get plenty of power out of them . For the generator, it might be a little counterintuitive, but a larger motor may be better. It would have more than enough hp so it could be geared to operate at a lower speed, which should make everything last longer. A large motor operating at a low speed shouldn't use more fuel than a small motor operating at a high speed. Engine modifications aside: I don't see a co generator being cost effective, unless the motors are much more efficient or it uses a much cheaper fuel source. I don't think a generator would ever be competitive with grid electricity, so the electricity that a co generator produces has to be thought of as a "bonus". Maybe it is more effective as a heat source. I may need to go back and check my math for the heat output. ~5hp =12,000btu, but over time it may be cumulative and the btu/h may be much higher. More research, Thanks for the feedback everyone.