Wednesday, September 3rd, 2014

The Life of A Fuel Molecule

fuel injector

Fuel Injector

Life is a paradox! Everything real and alive, as well as things that we deem inanimate has a goal to fulfill in its lifespan. A molecule of fuel has but one goal to be performed; that is to be allowed to unleash the energy that it holds within itself. That energy is to be harnessed by us to power, light and sometimes to destroy things in our world.

This particular molecule is deemed to be joined by millions of other fuel molecules to be compressed in a cylinder with 14.7 molecules of air so that a spark can ignite it and unleash the power to push a piston downward in the bowels of an engine. This is what we mechanics call combustion.

Unlike every action film that we have watched, gasoline does not explode, it burns. But when combined with air and the physics of atomization a highly unstable and violent vapor does exist and that is very explosive. That is exactly what happens in every cylinder of every internal combustion engine.

As with everything in life, there is the right way, the wrong way or the best way to achieve any goal. This is what this article is all about, the best way to exploit as much energy from that single molecule as efficiently as possible.

In the history of internal combustion engines fuel and air are funneled into the combustion chamber in a varying number of ways and under varying conditions. In the very beginning the fuel was almost just dropped into the carburetor bowl where it was drawn into the intake manifold by the vacuum generated from the pistons while on their downward stroke. The atomization process was haphazard at best as the fuel molecules just collided with the air molecules during their journey into the combustion chamber.

As vehicles evolved so did their need for power and the fuel delivery systems became more and more exacting. In the 50’s it was found that water molecules injected into the intake manifold just under the carburetor created a wonderful homogeneous mixture that traveled and ignited well. Water injection went by the wayside because it was just one more fluid that needed to be checked and it tended to freeze in the Snow Belt.

The next step was to introduce pressures to help get the fuel into a gaseous s state. Most carbureted systems ran very well on 4 psi. As systems improved and more miles per gallon and power were demanded those pressures have increased dramatically. Initially the early throttle body injection systems ran well on pressures of 9-12 psi. Ported and synchronized injection systems started at 35psi and the Vortec engines demand 64psi to start and 55psi to run. This brings us to the new “Gas Direct Injection” systems known as GDI, which need a mad crazy 2200psi to run. Yes that is 2200 pounds and this is not a misprint. Repairs and services for these systems will be astronomical if abused with cheap fuel and or poor maintenance schedules. Also, these systems are already out in the field and are not in only high end vehicles; many economically based 4 and 3 cylinder vehicles are already using these systems so be educated when looking for new vehicles.

Dirty Combustion Chamber

Dirty Combustion Chamber

Up until the ported injection fuel designs, the fuel and air travelled together from the top of the intake manifold to the combustion chamber. Then the fuel route became separate and was atomized with pressure and mixed with the air in the combustion chamber above the valve faces. With the development of GDI the fuel is now deposited directly on the top of the piston below the valves.

The question is what kind of maintenance is required to make these different systems work the most efficiently? Imagine this; sitting on top of a water slide or watching a bob sled navigating its course. In your mind’s eye do you see how slick the ice is and how polished the walls are and how smooth the turns are? Now imagine the same course with clumps of debris stuck in the course and those smooth rounded turns with right angles and junk deposited in the seam of the wall and the bottom of the tube. How many seconds will be lost in that race? That is exactly what the inside of your intake manifold looks like. Without periodic cleanings and clean air filters the amount of air that can get to the combustion chamber is not only restricted, the velocity of that air is diminished and the atomization of the fuel and air is diminished. And as I said in the beginning of the article; that’s what makes cars blow up!

Come ask us about our fuel services, ask us about how we can increase the efficiency of your engine, and increase your miles per gallon and how we can give you an extended warranty on your engine for as long as you own it.


Gregg’s Automotive Maintenance & Repair Center

236 S. Tamiami Tr.
Punta Gorda, Fl. 33950
Auto Repair, A/C Repair, Oil Change, Brake Repair & Transmission Services