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Throttle Body Fuel Injection - An Economical Performance Option
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 The first step towards installing...  The first step towards installing any fuel injection system that requires a return line is to figure out how you’re going to plumb it back into the gas tank. There’s only one line coming from the stock tank on our ’68 Chevy, and it’s 5/16-inch.  Instead of modifying the stock...  Instead of modifying the stock sending unit, I got one for a ’71-’72 Chevy from Brothers Trucks that has a 3/8-inch fuel feed line and a 1/4-inch vent line.  Then I removed the 1/4-inch...  Then I removed the 1/4-inch line, opened up the hole in the sending unit, and soldered a 5/16-inch line in its place. Note that I directed the return line away from the fuel inlet pickup point to help reduce turbulence at the inlet caused by the returning fuel.  With the new sending unit...  With the new sending unit in place, I decided to use the stock 5/16-inch hard line as the return since it runs from the tank up to the firewall. Since the original connection used a flare nut to connect to the line on the stock sender, the tubing was already flared on the end which allowed me to use a piece of tubing to mate the two ends. Normally, I wouldn’t prefer this method as it means having a short piece of hose in the cab, but since the feed line on the new sender will require the same connection, I made the concession to do the same on the return line. This kind of connection is fine as long as both ends of the hard line have a sufficient flare or swage on the end to keep the hose from sliding off the end once clamped in place.  I bent up a new 3/8-inch hard...  I bent up a new 3/8-inch hard line with a flare on both ends to run from the sending unit down under the cab of the truck. Here, you can see the use of a flaring tool to put the proper flare on the end of the hard line to prevent the hose from sliding off the end of the line.  Two short lengths of hose...  Two short lengths of hose are used to mate the sending unit to the new feed line (top) and the return line. The other issue that could come to bear is the addition of added electrical draws from a switched key source. Back in the day, our trucks had extra fuse panel outlets for a heater and maybe a radio, but that was about it. Start adding the necessary components for a fuel injection system and you might find yourself without a proper source to draw power, so that is something definitely worth consideration. Once these two items are sorted out however, it’s fairly straight forward to install the necessary components to get that antiquated carburetor out of the way in favor of a modern fuel injection system. And speaking of easy, remember the geeks I mentioned earlier? Well, they’ve taken the guess work out of programming a modern EFI system by inventing an ECU that does the guess work for you. Using a handheld programmer, all you have to do is enter a few parameters regarding your particular engine setup and then simply hop in your truck and drive away. Yes, it’s that simple. The ECU takes over from there and learns the necessary driving parameters based on the inputs of the various sensors installed. Using information gathered from the vacuum signal, O2 readings, TPS location, and engine speed, the ECU determines the changes necessary to maintain roughly a 14:1 air/fuel ratio throughout the engine’s load and power band. Pretty neat stuff ain’t it!? So instead of a roughly idling, hard starting, fuel guzzling carburetor, you’re left with a finely tuned Swiss watch of an induction system. Oh, and I almost forgot one of the most important aspects of adding an EFI system—the fuel mileage. When I first got the ’68 up and running in its latest incarnation, I was pretty excited at what the five-speed transmission and 3.73 rear ratio would yield when it came to highway gas mileage. Once I crunched the numbers, however, I was left wanting a bit more. Based on my initial calculations, the stock 307 with a 650 carb was good for about 13 mpg on the highway, cruising at about 65 mph. Not too bad for a big, heavy, longbed truck, but not exactly an ideal daily driver status. With the new Holley Avenger EFI setup, however, I’ve bumped that number up to a much more economical, wait for it…18 mpg! Ok, so that doesn’t seem like much, but a quick calculation says that for every twenty gallons of gas, I’m getting an additional hundred miles of out it. And at nearly five bucks a gallon, that’s pretty darn good! CCT  From there, I ran 3/8 fuel...  From there, I ran 3/8 fuel injection hose to the prefilter, pump, and post filter, then onward to the throttle body. Note that the inline pump and fuel line is clamped to the framerail using rubber coated clamps. The POS terminal on the fuel pump will connect to the green wire on the main wiring harness while the NEG terminal needs to be connected to a good chassis ground source.  With the fuel lines run, it’s...  With the fuel lines run, it’s time to install the throttle body. Holley provides a heat insulator gasket to use between the intake manifold, in our case a Weiand Street Warrior, and the throttle body. In our case, the linkage I built for the original Holley carb mated right up to the throttle body, making for an easy install. Some applications, however, will require the use of the ball and bracket adapters provided with the kit.  Next up, the vacuum advance...  Next up, the vacuum advance from the distributor is connected to the ‘spark’ vacuum source on the throttle body, while the MAP sensor is attached to the full manifold vacuum port on the right side of the throttle body as close as possible. Note that the MAP sensor is mounted in such a way so that the vacuum port on the sensor is pointed at a downward angle above the vacuum source to prevent any moisture from collecting in the sensor itself. At this point, the fuel lines are connected to the throttle body as well.  Back under the truck, it’s...  Back under the truck, it’s time to install the wide band oxygen, or O2, sensor. Holley provides a weld-in bung to be installed as close to the engine as possible. If your truck has catalytic converters, this will need to be installed between the engine and the cats. First, a 7/8-inch hole was drilled at a downward angle on the passenger-side exhaust pipe...  …before the bung was TIG welded...  …before the bung was TIG welded in place and the O2 sensor installed. Do not weld the bung up with the O2 sensor installed! The pigtail on the end of the O2 sensor gets connected to the pigtail labeled WBO2 on the main harness.  Back up top and it’s time...  Back up top and it’s time to mount the ECU. This should be installed in an area that is not prone to being hit by water or road debris, far from the exhaust, and away from spark plug wires, CD ignition boxes, or other “electrically noisy” devices as possible. The preferable location is in the passenger compartment, but given the tight confines of a pickup truck, the engine bay can be okay as well, given the previous warnings are heeded.  Now it’s time to uncoil that...  Now it’s time to uncoil that snake and start hooking stuff up! It’s pretty straightforward once the harness is laid out in the engine compartment. We started with the two ECU connectors…  …then moved up to the connections...  …then moved up to the connections on the throttle body. From left are the throttle position sensor (TPS), manifold air temperature sensor (MAT), manifold air pressure sensor (MAP), and the idle air control (IAC) connectors. That gray connector on the bottom…  …mates to the INJ-labeled...  …mates to the INJ-labeled connector on the main harness.  The last connector on the...  The last connector on the bunch mates to the coolant temperature sensor (CTS) that needs to be installed in an engine coolant passage. Note that there are also connectors that allow the connection of both a fuel pressure and an oil pressure transducer. These are not necessary and can be left disconnected if not applicable to the particular setup (ours were not).  There are six loose wires...  There are six loose wires in the harness that also need to be tended to. From left is a red/white wire that connects to a 12V switched source, a green wire for the fuel pump, a white wire that us not used, a solid red wire that needs to be connected directly to 12V battery power, a black ground wire, and a yellow coil wire. There are specific instructions on where to connect the yellow wire given each particular setup (standard canister-type coil, non-HEI). For our system, it goes to the negative terminal on the coil to provide engine speed input to the ECU.  The main power harness is...  The main power harness is then connected to the ECU (top connector) and directly to the battery. Note the fused connection built into the main power harness.  With all the necessary connections...  With all the necessary connections made, the wiring harness can be tucked up against the throttle bod, clear of the throttle linkage.  Using a spacer, we were able...  Using a spacer, we were able to retain the dual snorkel '69 Camaro air cleaner from the previous carb setup, which helps hide some of the wiring and totally hides the throttle body. A careful eye is needed to even notice the fact that our little '68 307 has been brought into the 21st century!
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The Thinker??? - Haul Monitor
Ryan talks about the friendly badgering that goes on around the shop and overcoming obstacles that seemly pop up out of nowhere during a project....
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