Hey there Veggie Faithful! Been kind of boring around the veg industry lately, and I know I have not helped that much since I have not been on here. Well the economy is flat, business is flat, and hasn't been much excitement. I am not much of a conversationalist, can only really talk about techy geeky car stuff, so here is some techy geeky car stuff, er Truck stuff covering questions MANY of you have asked me over the phone. Basically What is a "Powerstroke" and what is the best year to convert. So follow along if you dare, this was supposed to be a quick down and dirty 1 pager that turned into a 7 page document that I finally had to end because I was using way too many electrons to write it. I digress-
Brief History So without going into too many boring details, but confusing all the same, “Powerstroke” is the Ford name for the engine developed by International, using State of the Art (for 1993) Caterpillar design Diesel Injection Technology known as HEUI, or Hydraulically actuated Electronically controlled Unit Injector. This basic HEUI architecture was available in Ford F-250 through F-750 series trucks, and E series Vans from 1994 through 2007. In 2008 Ford again Jumped ahead of the competition in technology by going to Common Rail Injection (not new) using Piezo crystal injectors developed by Bosch. The use of the Piezo injector was the first by a Domestic automaker in any application, and had been previously used ONLY on high end European diesels. More on that later.
HEUI Hydraulically actuated, Electronically controlled, Unit Injector. So what exactly does that mean? It means that from 1995 through 2007 ALL Ford light and medium duty diesel trucks did not have an injection pump. None, nada, zip. This is in fact one of the HUGE factors in favor of using a Powerstroke for biofuels. It is impossible to cause a catastrophic failure by breaking the injection pump because it does not exist. Each Injector is in fact its own Injection Pump. Although the design changed a bit between the 7.3 and the 6.0, the basic concept is the same. Each unit injector basically has two sections- One for fuel, and one for high Pressure engine Oil. Unless there is a mechanical failure the two fluids should never contact each other. The fuel provided by a low pressure fuel pump(~55psi), and the Engine Oil is delivered by a High Pressure Oil Pump(HPOP). The HPOP uses low pressure crankcase engine oil and pressurizes it to between 500 and 3000psi based on the duty cycle of the IPR(injection pressure regulator) that is controlled by the PCM(Powertrain Control Module). The delivery path to the engine for the fuel varies based on year with 3 primary designs we will discuss in later segments. But once the fuel reaches the engine itself, the rest is all the same. The engine is a V-block design with two cylinder heads and 8 cylinders. On the Left(Drivers) side you have cylinders 2,4,6,8 from front to back, and the right(passenger) side is numbered 1,3,5,7 front to back. In each head there are 4 large round holes that feed all the way down to the combustion chamber in almost a reverse cone shape. Those are the injector cups where the injectors are positioned in the head with the tip actually protruding into the top of the combustion chamber. Also in each head are two passageways that run the length of the head. And here is reason #1 why these engine make such excellent conversion candidates. The fuel rail is inside the head, and the fuel system is a deadhead design, meaning there is no return from the engine. That means the fuel moves relatively slowly through the head until it reaches the injector. During that time the oil is picking up heat directly from the motor. Some may argue this point but I have tested it over and over again. So long as the engine is up to operating temperature it is IMPOSSIBLE to get cold oil to the injector. Of the two passages in the head- One is for fuel, and the other is for high pressure oil. Reason #2 that the Powerstroke makes a great conversion candidate . Precise fuel pressure is rather unimportant. Again, yes I said Precise fuel pressure in NOT important. The fuel pressure only needs to be enough to promote proper filling of the injector fuel cavity. Regardless of year, anything south of 50 psi and you may not get complete injector filling under load, anything north of 100 psi and you run the risk of interfering with correct injector operation. That leaves us with a nice liberal 50psi window for fuel pressure that will have no effect whatsoever on performance, power, emissions, mileage or anything else. This is PART 3 of why Powerstrokes make such great conversion candidates. Fuel pressure requirements are very non-specific, More than enough, and less than too much. Where the magic happens is with the High pressure oil. Both the 6.0 and the 7.3 have a 7:1 intensifier piston that multiplies the pressure of the high pressure oil by 7 and transfers it to the low pressure fuel to create a maximum injection pressure of 21,000 psi for the 7.3 and 26,000 psi for the 6.0! That is a max of 3,000psi of HPO for the 7.3 and 3,770 for the 6.0. So to recap, high pressure engine oil pushes on a piston that then pressurizes and injects the fuel into the cylinder. So the viscosity of the fuel does not change the injection pressure at all in this type of system. It could be solid Crisco in the injector and it will still be delivered to the cylinder. However the ability of the injector to refill after that initial injection is a whole other story. Now that you know the basics of HEUI injection, we can cover the three basic generations of Powerstroke.
1994.5-1997 In 1994 you could get 3 different diesel options for your Ford. There was a 7.3 Non turbo Indirect injected (IDI), a Turbo IDI, and the coveted 7.3 Powerstroke Direct Injected Turbo Diesel. As previously mentioned in 1993 Caterpillar developed the HEUI injection system, and International, under license from Caterpillar created the Powerstroke engine for Ford. The International version was known as the T444E. International used their old 7.3 IDI engine as the starting point for the new DI 7.3, and carried over some of the same features such as the Water to oil heat exchanger mounted on the drivers side. This advanced engine at the time quickly became backbone of the Light and medium duty diesel market powering not only Ford Trucks and Vans, but Ambulances, Service vehicles, Busses, Box trucks, and Millions upon millions of vehicles.
FUEL DELIVERY The challenge In converting these years of Powerstroke is in the fuel delivery system. They use a two stage mechanical lift pump mounted in the engine valley between the heads. Fuel is fed directly from the tank to the low pressure side of the pump, then into the Fuel bowl where it passes through the filter, and back to the high pressure side of the pump, out the back and to the rear fuel ports on the engine. The return is fed out the front fuel ports, through the regulator attached to the side of the fuel bowl, and back to the tank. From a performance standpoint this is a great setup as it is a true regulated return. But from a conversion standpoint it creates several issues, Such as cross contamination, long purge times, lift pump reliability and the fact the the regulator recirculates a small amount of return fuel back into the fuel bowl. DFA solves those issues by simply eliminating the mechanical lift pump in favor of an electric one and updating the fuel system to mimic that of the 1999 and newer Powerstrokes, Or basically a deadhead design. It is a bit more work and cost, but reliability goes up, purge time goes WAY down, and cross contamination is eliminated and we still use the OEM fuel filter for the diesel.