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The Purple Pig Gets MSD Electronic Fuel Injection - The Atomic AgeFrom the September, 2012 issue of Rod & Custom By Kev Elliott
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[1] While there was absolutely... [1] While there was absolutely nothing wrong with the 4160-style Quick Fuel four-barrel that has been on the engine since it was built, we’ve been keen to install EFI on one of our projects for a while now. I say I’m a points and carburetor kind of guy because in my mind I figure if they go wrong I can fix ’em at the side of the road. However, they both require fiddling with to get an engine to run right, and my attitude may have more to do with my reluctance to accept change than any rational reasoning! I drive a late-model truck most days, and have yet to futz with the ignition or fuel delivery systems, so I figured maybe it was time to jump into the 21st century with one of my projects. A meeting with Todd Ryden from MSD Performance at the beginning of the year resulted in a conversation about the company’s new Atomic EFI (electronic fuel injection) system. Before long, we were discussing stopping off at MSD’s facility in El Paso, Texas, en route to the Lonestar Round Up in April, to swap out the four-barrel carburetor on my Project Purple Pig ’49 Chevy for the new Atomic. This would provide some real world data and a great comparison between the carb and EFI out on the road. Well, best laid plans and all that, while the ’49 did get to EL Paso, it was on a trailer. I got it driving the weekend before our intended departure, but wasn’t comfortable driving it almost 3,000 miles across the desert and back with no testdrives apart from a few laps around the block. So, unfortunately, the comparisons will have to wait for when I re-install the carb and do some testing. [2] Here’s what you get in... [2] Here’s what you get in the Atomic EFI kit: the throttle body (TB) with integral ECU, throttle body harness, power module (PM), power module harness, handheld monitor, O2 sensor and harness, 4-foot CAN extension, and gaskets. In the bag are a coolant temp sensor, O2 bung and plug, PM mounting hardware, grommets, and a 4G micro SD card. The benefits of EFI include faster startup, better driveability, cleaner idling, and potentially more horsepower. Right away, after our install, the improvement in startup was evident, with absolutely no need to touch the gas pedal, even on cold starts. The Atomic EFI is designed to bolt on to any square-bore, four-barrel intake, including common 4150 and 4160 designs, and will therefore fit any engine for which such an intake, or adaptor, is available. It shouldn’t be installed on engines making less than 100 or more than 525 hp, though there’s an optional high-horsepower pump kit that will support 620 hp. It also cannot be used in dual-quad applications, or with any power adders or alternative fuels at this time. That’s not to say MSD won’t alter this in the future. It can, however, be used with returnless fuel systems if required, though you’ll need the Master Kit, which includes a pulsing fuel pump, fuel filter, and fuel lines. The ’49 already has an Aeromotive pump-in-tank fuel system, with a return line, so we only required the throttle body kit. While on the subject of fuel delivery, MSD recommends you don’t use hard lines for your entire fuel system. Factory EFI systems have suppressors built into the ends of the fuel rails to counteract the pulsing of fuel in the lines, and rubber hoses tend to do a similar job. While our Chevy has hard lines under the car, braided line is used from the tank to just ahead of the rearend, and from the bottom of the firewall up to the regulator, which should suffice. Plus, as it’s a return system, pulsing is reduced anyway. [3] To simplify the installation,... [3] To simplify the installation, we’d welded the wideband O2 bung into the driver side exhaust, just below the header flange, prior to our visit to MSD. We also installed the sensor, though it should be noted a vehicle shouldn’t be driven with the sensor installed and not hooked up. What makes the Atomic EFI so user-friendly is the fact that it is a direct swap for a four-barrel, with the throttle cable and kick-down or TV cable simply swapping over from one to the other, and there are only eight wires to connect. The Atomic requires a 12V square-wave signal to use as a trigger. This is the same signal that most aftermarket tachometers require and is provided by a typical CD ignition, such as an MSD 6A. Also, MSD’s Ready-to-Run distributors or their HEI Module all provide a 12V square-wave signal through a separate tach output wire. The Atomic also has the capability to control ignition timing. This requires an MSD Ignition Control as well as one of their standard distributors. While at MSD, they converted our regular HEI distributor to work with the Atomic by replacing the control module with one of their HEI modules. This module is available separately. You may wonder how much current this system takes to operate. If you have two engine cooling fans and both are on, the fuel pump is at full capacity, the injectors are at their maximum, and the input voltage is around 10 V, the system can draw as much as 30 amps. Normal operation is approximately 14-18 amps. Note this is with two fans, it’s not the EFI alone that’s drawing this current. When our single fan switched on, we noticed the engine stumbled a little at idle, though with the alternator disconnected it was fine. This pointed to the fact that our alternator isn’t rated for a high enough output (plus it was running at idle speed), and considering the Chevy has an electric brake booster, an air ride system, A/C, and electric exhaust cutouts, along with the usual electrical systems in a car, we’ll be sourcing a 140-amp alternator in short order! [4] We routed the wiring for... [4] We routed the wiring for the O2 sensor alongside the brake lines, ensuring they were as far as possible from the exhaust and steering. The connection was made on the inside of the chassis and secured. The wiring from this connector was then routed discretely up to the power module, which we’d mounted behind the dash. The main appeal of this system for us is that not only was the install easy and straightforward, but come time to start the engine for the first time, there’s no throttle configuration to contend with, and no fuel map tuning. Simply input some basic engine data into the handheld controller, then let the system self-learn. The throttle position sensor (TPS) is an automatic self-calibrating, non-contact sensor integral to the ECU, which itself is integral to the throttle body, reducing wiring. As well as the TPS, the MAP, IAT, and fuel pressure sensors are also all incorporated into the throttle body, meaning the only sensors that require connecting are the coolant temperature and O2 sensors (both are supplied with the kit). The latter is the only fabrication required for the entire install, as the O2 bung has to be welded into the exhaust system. If you want to find out more about the Atomic EFI, check out the product-specific website at www.atomicefi.com, which not only has all the details you could wish to know, but also a forum, answers to frequently asked questions, and even an install video showing a returnless fuel system install. Meanwhile, here’s how the MSD crew set about converting the Purple Pig.  [5] Once at MSD, Erik Brock...  [5] Once at MSD, Erik Brock wasted no time in wrestling with the Purple Pig. Goodbye carb, hello EFI!  [6] Though the carburetor...  [6] Though the carburetor has been removed, everything else can be reused with the Atomic EFI; vacuum lines, throttle and TV cable bracketry, fuel lines, and even the HEI distributor, though this requires some simple modification. The Atomic requires a 12V square-wave signal to trigger the EFI. In most cases, a common CD ignition is used, but we installed one of MSD’s HEI modules. The new module has a dedicated 12V signal wire to trigger a tach or an aftermarket EFI system.  [7] The base of the Atomic...  [7] The base of the Atomic TB is drilled and tapped for vacuum take-offs; the one on the left here (remember, the unit is upside down—it’ll be the one nearest the number one cylinder once installed) is ported vacuum, while the two on the right, plus two more on the rear of the TB, are manifold vacuum.  [8] The TB bolts directly...  [8] The TB bolts directly in place of the carburetor, and is supplied with all the linkage bracketry just like a carb. Note how the Lokar throttle and TV cable bracket bolts on just as it did before.  [9] The only modification...  [9] The only modification we had to make was to replace the set screw (arrow) with a longer version on the cable bracket mount, as the TB has a slightly different shaped base than the carb.  [12] Backtracking slightly,...  [12] Backtracking slightly, the control module in our HEI distributor was removed …  [13] … and replaced with an...  [13] … and replaced with an MSD version. This internal two-pin connector was hooked up …  [14] … before the module was...  [14] … before the module was mounted. The orange, black, and red wires are grouped in a sleeve and plug into to the distributor cap. Another black wire in the sleeve runs from the connector on the cap and grounds to the intake manifold. The end of the black wire shown has yet to be connected to the distributor base plate. We’ll explain the gray wire’s destination shortly.  [15] Three wires from the...  [15] Three wires from the ECU feed into this connector. The yellow wire is a tach output used when an MSD ignition unit is installed, so the Atomic can control engine timing. It can otherwise be used as a 12V square-wave trigger to a tachometer. The orange wire is an A/C kick-up wire, which compensates for the added load on the engine from an A/C compressor. Neither of these wires were connected at this time. The white wire is the tach input wire for the EFI, supplying the rpm signal from the distributor or ignition box.  [16] The gray wire from the...  [16] The gray wire from the tach connects to the white wire described in the previous caption, and is supplied with a spade connector installed.  [17] However, for a neater...  [17] However, for a neater appearance and to simplify the wiring, Brock pulled the white wire from the connector and installed the gray wire directly into it. This requires a special tool. It also means the distributor cannot be totally removed from the engine bay in the future without cutting the wire or removing the orange and yellow wires inside the car. We can live with that.  [18] The red “wire” exiting...  [18] The red “wire” exiting the TB is actually a sleeve covering violet and green wires, which are for a magnetic pickup in an MSD distributor when the Atomic is controlling timing. We didn’t use these. The larger braided harness from the TB is the CANbus harness, which connects to the power module using a six-pin connector. This mustn’t be cut, and MSD offers extensions if needed.  [19] The new water temperature...  [19] The new water temperature sender (supplied) was installed and connected using the dedicated connector on the smaller braided TB harness, feeding directly into the ECU.  [20] The ’49 Chevy has this...  [20] The ’49 Chevy has this removable panel at the top of the driver side of the firewall. Not only does it make access to the rear of the dash easy, but provided a perfect mounting position for the MSD power module. The individual wiring harnesses were routed up the side of the firewall and through this stock access hole. I’ll source the correct rubber grommet at a later date.  [21] From the inside the PM...  [21] From the inside the PM is mounted like so. The harness on the right is the main PM harness, the CAN port on the far left is for the handheld controller, while the remaining CAN port is for the TB harness. The PM is rubber mounted, though I elected to use bolts rather than the screws supplied because the backside of the mount is visible.  [22] The PM harness uses this...  [22] The PM harness uses this large connector. All the wires are pre-connected at this end, requiring routing and terminating at their intended destination. The instructions denote which wire goes where. The large red wire is the main power feed and should be wired to the battery positive, while the large orange wire is for the fuel pump, rendering the existing wire and relay obsolete, as the PM will now control the pump.  [23] Brock is fastidious when...  [23] Brock is fastidious when it comes to wiring, and I’m sure my unfinished dash wiring was unbearable for him to work amongst. Here he’s connecting the fan wiring from the PM inside the car using proper factory-style connectors. The harness includes wiring for two fan circuits, though the Chevy only uses a single fan. They both switch the ground circuit of a fan relay.  [25] The inlet and return...  [25] The inlet and return lines were a direct swap over, being -10 AN fittings, but the outlet required a -6 AN hose from the regulator to the throttle body.  [26] The Atomic TB uses MSD-machined...  [26] The Atomic TB uses MSD-machined -6 AN inlets, which accept these push-lock fittings. The fuel rail is integral to the TB, and with a single fuel line it can be routed to either the front or back fitting.  [27] We rigged up a push-lock...  [27] We rigged up a push-lock hose using 90- and 45-degree fittings to fire up the engine, though I’ll replace this with a braided hose to match the rest of the fuel system.  [28] With everything connected...  [28] With everything connected and wired correctly, we were ready to fire the engine.  [29] The instructions detail...  [29] The instructions detail the configuration and initial setup, which are all done using the handheld controller. Prior to startup it is necessary to input some engine parameters.  [30] It was immediately obvious...  [30] It was immediately obvious to Brock, once he’d run through the initial setup, that the TB wasn’t getting full throttle, so the cable was adjusted accordingly.  [31] The fuel pressure regulator...  [31] The fuel pressure regulator was set at 45 psi, using the Allen adjuster on the top of the regulator. The handheld controller displays fuel pressure, eliminating the need for a gauge.  [32] The final adjustment...  [32] The final adjustment to make prior to startup was to set the throttle blades. The instructions cover this procedure. Once the engine is started and at operating temperature, the Idle Air Control can be monitored on the handheld controller and the blades re-adjusted to help with additional airflow at idle if needed.  [33] Though the instructions...  [33] Though the instructions are easy to understand, and the whole Atomic EFI installation isn’t overly complicated, it was reassuring to have the guys at MSD handle the install, while, for once, I stepped back and just had to photograph the procedure!
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