I have had engines I referred to as "cold blooded" before, generally because they were built so heavily that it took forever (one was over half a god damn hour) for them to warm up to peak operating temperatures, and you got no power or reliability out of them until then. These engines pissed me off. If you want one, look for a small displacement (less than 300cc) "universal Japanese model" motorcycle from the 70's. There are lots of other places too, but that is a reliable, inexpensive source.
Pressure and heat are very closely related. A diesel works by creating enough thermal energy through pressure on the fuel to cause it to spontaneously combust, which vastly increases the temperature, which increases the pressure enough to drive the pistons through their power cycle. Replace the pressure induced heat with an electric spark and you have a gasoline engine. The thermal energy is still the integral part of the operation of the engine.
As far as no byproducts, the only way you are going to ever end up with no physical byproducts would be a 100% efficient nuclear reaction (again, good luck with that), during which you would expect large quantities of some form of energy, most likely thermal energy, electromagnetic radiation, and light. No harmful byproducts, on the other hand, could be as simple as water, in the case of hydrogen power, but is likely claimed to be water and CO2 for this stuff. In reality, there would be some carbon monoxide and nitrous oxide too, just because that stuff gets everywhere, and unburned hydrocarbons.
The idea that there would be no heat from this fuel source's combustion is silly at best, and certainly wouldn't be a selling point as a gasoline replacement even if true, but the idea that it burns much cleaner than petroleum based fuels is both likely and laudable. If the whole thing isn't a sham, which is possible.