In this chapter, I cover a complete throttle-body EFI installation, the MSD Atomic EFI system. With the information in this chapter, you will be able to install this or any similar throttle-body system. And by the conclusion of the chapter, you will know the time, tools, and expertise required to complete the task. Could those magazine ads really be true? Is it really possible to convert to EFI so easily and quickly?
This Tech Tip is From the Full Book, EFI CONVERSIONS: HOW TO SWAP YOUR CARB FOR ELECTRONIC FUEL INJECTION . For a comprehensive guide on this entire subject you can visit this link:
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When I walked the floor at SEMA (Special Equipment Manufacturers Association) in 2011, and again in 2012, one throttle-body-based EFI system really stood out to me: the MSD Atomic EFI system. When CarTech commissioned me to write this book, I absolutely wanted to include this system. So, what was it about the Atomic EFI system that stood out? Well, first and foremost, the ECU is built into the side of the 1,000-cfm throttle body so you don’t have to find a location for it or even mount it.
This product category is growing so incredibly quickly that numerous new examples have likely come to market by the time you have this book in your hands. Other products may be improved. Regardless, the following installation overview is absolutely representative of this category of product. The installation is accomplished by mounting the throttle body to where your carburetor once sat. In addition to the TPS and IAC, the IAT, fuel pressure, and MAP sensors are also built into the throttle-body assembly and all are pre-wired to the ECU. Not only does this mean fewer connections need to be made, the harness itself is more compact and less laborious to install. If wiring isn’t your thing, the Atomic requires fewer electrical connections than any other EFI system that I’m aware of.
The Atomic EFI system includes an outboard module that needs to be located under the hood or under the dash: it’s your preference. The included harness is plenty long for either choice. MSD calls this the power module, which has a number of outputs:
- Electric Fan 1:low current, designed to drive a relay that powers the fan directly
- Electric Fan 2: low current, designed to drive a relay that powers the fan directly
- Fuel Pump: high current, designed to drive the fuel pump directly (20-amp capability)
In addition, the included handheld controller plugs into the power module.
MSD elected to use CANbus (controller area network) technology between the throttle-body assembly and the power module, as well as between the power module and the handheld controller. Again, this greatly simplifies the installation by reducing the number of wires required between components as a single CANbus cable connects the throttle-body assembly to the power module.
The ECU being integrated into the throttle body is the first thing that caught my attention, and likely the first thing that will catch yours.
When MSD representatives gave me the lowdown on the unit, the following things stood out that I thought enthusiasts would appreciate.
PWM Fuel Pump Output
The thing that caught my eye about the fuel pump output is that it has a built-in PWM with three possible settings, depending on the fuel system you elect to use:
- Pulse Width Modulated: returnless system with no regulator
- Non-PWM with Regulator: return-style system with a regulator
- PWMwithRegulator: return-style system with a regulator
I’m really fond of using PWM to manage the speed of the fuel pump for a number of reasons. If you elect to use a returnless system with no regulator with the Atomic EFI system, you must locate the fuel pump in the fuel tank and it must be designed to be submerged in fuel. As discussed in Chapter 2, this keeps the pump cool and prevents premature failure of the pump. Furthermore, if you’re that guy who refuels 50 miles after the “low fuel” light comes on (guilty . . . ), the purpose of locating the pump in the tank to begin with is defeated. Be honest with yourself here.
Allowing the ECU to also manage the ignition timing is the icing on the cake. At the time of this writing, the Atomic EFI system is one of only a few entry-level EFI systems to offer this.
The Atomic handheld controller is compact and easy to use. It’s chock full of terminology that any enthusiast familiar with carburetors already understands including idle advance, total advance, pump squirt, and power valve enrich.
The Atomic EFI system has a nitrous input that can be used to retard the engine timing when the nitrous is engaged. Obviously, the engine management feature must be utilized for this feature to work. Adding a 125 shot of nitrous to a 300-hp naturally aspirated engine would be a heck of a lot of fun on the cheap.
MSD Atomic designers and engineers are constantly refining the company’s products. At the time of this writing, the following apply.
You need adequate vacuum for an EFI system to operate optimally. If you have a big ol’ lumpy camshaft with no vacuum at idle to speak of, many entry-level throttle-body-based EFI systems are incompatible. According to MSD, if the lobe separation angle (LSA) is less than 108 degrees or if the duration is longer than 250 degrees, the Atomic EFI is not suitable for your application.
Sure, who doesn’t love the sound of camshaft cut on a 108-degree LSA with a bunch of lift and duration? Although that may get attention when you idle into the cruise, it’s the wrong grind for an entry-level EFI system such as the Atomic.
The maximum horsepower the system is currently capable of supporting is 625 hp when used with the correct fuel system components. In addition, the injector size cannot be upgraded from the stock size (80 lbs/hr at 60 psi).
The Atomic EFI system is compatible with power adders of any type. According to MSD, due to the increased fuel requirement on boosted applications the maximum horsepower that the TBI is capable of supporting can be 20 to 30 percent less.
Because the system cannot add the fuel required of a nitrous system, a wet nitrous kit must be used and the fuel system must be designed accordingly.
The MSD Atomic system is not compatible with dual-throttle-body applications, nor it is compatible for marine applications.
It is not UL approved.
MSD Atomic EFI System Installation
So, it’s time to get down to brass tacks and see if the Atomic EFI system delivers what it promises. Before beginning a similar installation in your own vehicle, you must have an 18-mm bung in the collector of one of the headers for the oxygen sensor. If you do not already have one, you need to install one before the installation begins.
It is preferable to locate the oxygen sensor upstream of the collector-to-exhaust junction. This prevents unmetered air passing the oxygen sensor in the event of a leaky collector gasket, which can provide erroneous feedback to the ECU and throw off the A/F mixture as a result. Any capable exhaust shop can do this and the bungs (and plugs) are readily available at any speed shop.
I did something here that you are not likely to do. I chose the system first and then had to find a vehicle that allowed me to illustrate a typical installation. You already have the vehicle and you’ll choose the system to best suit your application. But my task was easy enough. I found Keith Kanak and his 1964 Chevelle with one phone call.
A 383-ci small-block Chevy from Beck Racing Engines is installed in Keith’s Chevelle. It has 10:1 compression and makes approximately 500 hp at the flywheel. The ignition system consists of only a Mallory HEI distributor with vacuum advance (basic enough) and the specs on the camshaft in the 383 are within the guidelines of the Atomic EFI system. In addition, the Chevelle has A/C, has been on The Power Tour multiple times, and Keith drives it everywhere. Long before I met Keith, I spotted this extra-clean Chevelle at a car show just a few miles from my home. Incidentally, Keith had been considering an EFI conversion for some time. Perfect.
I think it’s fair to say that most enthusiasts considering an EFI conversion like this one want to do it as inexpensively as possible. To illustrate this, I’ve split the install in the Chevelle into two stages. Stage 1 is the least expensive way to complete the conversion.
In addition, I’ve elected to use a factory-style fuel tank and not a custom-built EFI-specific fuel tank. Most owners also choose to use a stock tank in an effort to keep costs down.
In Stage One of the installation, we use the existing ignition system and have the Atomic perform fuel metering only. In Stage Two, we install a new ignition system and configure the Atomic to manage the ignition timing as well as fuel metering. You will learn whether or not this additional cost yields better results.
Here is an overview of the two installation stages:
Stage One: Add EFI, Utilizing the Existing Ignition System
The electrical system is the backbone of any EFI installation. Before adding a host of new electronic components to Keith’s Chevelle, we need to determine if the electrical system is up to the task. If not, we’ll optimize it.
1. Optimize Electrical System
When Keith popped the hood of the Chevelle, the first thing I noticed was the run-of-the-mill CS-series alternator and 10 AWG charge lead. Keith did have the engine grounded properly, which was a welcome sight. In addition, the Chevelle has a mechanical fan, which Keith intends to keep as it works perfectly, even in the summer in Phoenix.
So, is the alternator capable of handling the additional load of the MSD Atomic EFI system and electric fuel pump?
I used my Fluke DMMs and accessories and a Snap-on MT3750 Charging System Analyzer to perform all measurements. These are excellent tools and provide excellent data. If you don’t have access to such an analyzer, many well-equipped auto service centers have one on hand. Before taking the first measurement, I already knew that at a minimum we’d have to upgrade the wiring to the charging system to get all of the performance the alternator is capable of.
Using the procedure outlined in Chapter 2, here are the steps we used and our readings:
Record the resting voltage of the battery with the engine not running: 12.4 volts. (In most cases this denotes a partially charged battery. However, this vehicle has a red-top Optima battery. Here in the desert, it is all too common to see this particular battery resting well below 12.6 volts, so don’t read too much into that.)
Start the engine and bring the vehicle to operating temperature.
Turn on all of the accessories, including the high-beam headlights, A/C, electric cooling fan(s), audio system at a common listening level, etc.
After the engine has reached operating temperature, record the voltage at the battery: 14.0 volts
Record the output current of the alternator: 30 amps.
Load the alternator with the carbon-pile load in the Snap-On analyzer to determine how much output the alternator is capable of at 800 engine RPM.
Record the voltage at the battery: 12.0 volts.
Record the output current of the alternator: 61 amps.
This leaves us with 31 amps of reserve that can be used to power the EFI system and fuel pump. Even though this should be plenty, I know we can improve upon it and I’m going to show you how. We elected to upgrade the charging system accordingly.
This vehicle has a stock ammeter in the cluster and Keith wanted to retain it so I kept the stock wiring configuration for the charge lead. The ammeter in the Chevelle has a shunt wired in parallel so it was possible to keep it. In many cases, you are not able to retain the functionality of a stock ammeter when upgrading the charging system, especially when upgrading the alternator to a higher-output unit.
In short, I upgraded the charge lead, the return path of the alternator, and the return path of the battery. While I was at it, I assembled some new battery cables to replace the ones that were an eyesore to an otherwise clean engine bay.
Because of the wiring scheme of the Chevelle and the fact that we were retaining the ammeter, I elected to use 8 AWG wiring for the wiring upgrades to the alternator (I normally use 4 AWG). All parts were obtained from CE Auto Electric Supply.
Assessment After Charging System Upgrades
After the upgrades were finished, we again used the procedure outlined in Chapter 2 to take new readings to see the fruits of our efforts. Here are the steps and our readings:
Record the resting voltage of the battery with the engine not running: 12.4 volts.
Start the engine and bring the vehicle to operating temperature.
Turn on all of the accessories, including the high-beam headlights, A/C, electric cooling fan(s), audio system at a common listening level, etc.
After the engine has reached operating temperature, record the voltage at the battery: 14.4 volts.
Record the output current of the alternator: 36 amps.
Load the alternator with the carbon pile load in the Snap-on analyzer to determine how much output the alternator is capable of at 800 engine RPM.
Record the voltage at the battery: 12.0 volts.
Record the output current of the alternator: 72 amps.
Charging System Results
Our efforts paid off and we got a substantial improvement. Let’s consider our results as percentages in the charts below.
Now, these numbers alone don’t tell the full story as accessories respond to power, which is the product of voltage and current. So, let’s compare that in the charts below.
This “free power” was simply the result of wiring the alternator correctly and with the correct gauge of wire, eliminating the voltage drop caused by resistance in the process. I’ll take those gains all day long and I’m confident that this alternator now has enough reserve to power the ECU and fuel pump.
Disconnect the negative (-) battery terminal before proceeding.
2. Install Fuel System
Keith had recently replaced the 50-year-old fuel tank in his Chevelle with a new factory replacement tank from Impala Bob’s. He added a -6 male bung to it before installing it, anticipating that he would be upgrading to EFI at some point down the road. He capped it in the meantime. That paid off in spades for us here.
Before choosing the exact components for this system, we first determined the size of line required based on the chart on page 24 in Chapter 2. Because MSD recommends a 3/8-inch inside-diameter (ID) fuel line to the inlet of the throttle body, this is what we came up with:
We used push-lock–style hose and fittings for this installation to keep cost down and reduce installation time. It is worth noting that MSD specifically points out that hard fuel lines are not compatible with the Atomic EFI system. We elected to run a return-style fuel system, as we’re using a fuel pump that is not located in the fuel tank (see Figure 2.6 on page 22). We chose components from Holley for this fuel system.
Holley has a document on their website called the Holley Fuel System Selection Chart that makes it easy to determine the correct components for any fuel system. Also, Holley now offers EFI fuel system kits on their website, which include a pump, pre-filter, post-filter, regulator, lines, and fittings.
In Keith’s Chevelle, it simply isn’t possible to mount the tank and pump rearward of the fuel tank. So Keith fabricated a really slick bracket to mount the pump and pre-filter to just forward of the tank, which is equipped with a pick-up to supply the pump. Keith mounted the assembly to the floor of the trunk just forward of the tank.
Although the exhaust doesn’t run particularly hot in this area, Keith is in the process of modifying the over-axle assembly to relocate this part of the exhaust. This ensures the heat from the exhaust isn’t an issue.
We found a nice place inside the frame rail just behind the front passenger wheel to locate the post-filter.
Okay, now that a bunch of the hard work is complete, it’s time to remove the carburetor and install the throttle-body assembly. Once the installation is complete, you have to look closely to see that this isn’t a carburetor.
We located the regulator along the firewall, behind the inner fender and as far away from the headers as possible. This mounting location doesn’t satisfy NHRA regulations for fuel system components. That’s not an issue with this Chevelle, but it may be for you, so be sure to take the rules of any sanctioning body into consideration when choosing a place for the components.
The feed and return lines were then routed along the frame rails and up to the throttle body and regulator. We anchored these with Adel clamps and cable ties to keep everything secure and out of harm’s way.
Although the vent tube is hard to see, it is located to the left of the return, about an inch higher.
The return line and feed lines are now connected to the regulator and throttle body, respectively.
Now that all the fuel lines are connected, we elected to connect the existing linkage to the throttle body. As the throttle body is nearly identical in this respect to the carburetor, this took all of two seconds.
3. Install Atomic EFI Components
Next, we located the CTS in the intake manifold. You may choose to locate it in either cylinder head as well. Either way works. We elected to put the CTS in the manifold to avoid the possibility of breaking off the plug in the head when trying to remove it, which is all too common. If the plug breaks off in the head, it makes for a long day to remove it.
It is necessary to drain the top 1/3 or 1/2 of the radiator before doing this so that the level of coolant in the radiator is below the location you choose for the CTS. After draining the coolant, we marked a location on the manifold, and drilled and tapped the hole without removing the thermostat housing. The CTS included in the Atomic EFI is a 3/8-inch NPT thread, which calls for a 37/64-inch hole. Any real car guy has both in his toolbox!
We used plenty of grease on the drill bit and tap to minimize the amount of shavings that fall into the water passage. I also held the shop vac while Keith drilled. After the tapping was done, we vacuumed the inside of the water passage to get every last shaving out. This was actually quite simple.
Next up is the oxygen sensor. Keith already had an 18-mm bung welded into the collector on the passenger-side header for a handheld wideband A/F meter, so this was greatly simplified. MSD, as all others, recommends that you locate the oxygen sensor in such a way that it is mounted at an angle of at least 10 degrees above horizontal.
The Chevelle is equipped with a Mallory HEI distributor with vacuum advance. I’m a huge fan of vacuum advance for street-driven vehicles because it promotes lower engine temperatures at idle and increases fuel economy and throttle response, all of which provide better drivability.
We connected the vacuum advance to the base of the throttle body, which has three ports on the front. Two are manifold vacuum ports and one is ported vacuum. We connected the vacuum advance to the manifold vacuum port on the driver’s side.
The power module is the remaining component of the Atomic EFI that needs to be installed. It can be located either in the passenger compartment or in the engine compartment. We chose a location just inside the passenger side of the firewall.
This leaves everyone’s favorite part: the electrical connections. The connector on the throttle body includes the connections to the tach output of the ignition system (we use this in the first stage of this installation only) and the A/C compressor for the fast idle input. (Figure 5.36 shows the specifics.)
The power module includes the connections to the fuel pump, battery, and switched ignition. Figure 5.36 also shows the specifics for the wiring from the power module.
Even though this Chevelle doesn’t have electric fans, your vehicle may. The power module requires relays to operate electric fans, so Figure 5.45 illustrates how to wire them properly.
If you have a pair of electric fans, each controlled by a relay, you’re well advised to have each relay independently controlled by each of the fan outputs as illustrated in Figure 5.44. This allows you to set one fan to come on at a lower temperature and the second to come on at a higher temperature only when it’s necessary. This reduces fan noise and strain on the electrical system when you’re cruising around. (The connection to the switched ignition is not shown.) Be sure that you connect the switched ignition input to a point that measures +12V with the key in the RUN and START positions.
It’s important to note that the BATTERY (+) and BATTERY (–) connections connect directly to the battery positive and negative, not to the stud of the starter, the fuse box, etc. (See Chapter 2 for more details.)
4. Get It to Run!
At this point, you need to do a few things before you can start the engine: flush the fuel system, set the fuel pressure, configure the Atomic EFI, and adjust the throttle blades. Reconnect the negative battery cable before proceeding.
Flush the Fuel System
This ensures that any debris in the lines is flushed into a catch can and not into your new components. Simply disconnect the inlet to the throttle body and place it into a catch can. Then temporarily disconnect the pump from the power module, and power the pump directly from the battery via a jumper. Repeat this process for the line from the throttle body to the regulator (at the regulator) and the return line (at the tank).
After flushing the fuel system, re-connect all fuel lines and tighten the fittings accordingly. Then pressurize the system via the jumper to the fuel pump to check it for leaks. Check all fittings, including the ones under the vehicle. Address any leaks before proceeding.
Set the Fuel Pressure
I used the 1/8-inch NPT port in the regulator for this. MSD recommends between 42 and 48 psi of fuel pressure. I again used the jumper to connect the fuel pump directly to the battery as we adjusted the regulator to 46 psi. After setting the fuel pressure, check all fittings for leaks.
The Atomic EFI actually has a fuel pressure sensor built into the throttle body and the results are displayed on the handheld controller. You can use this to set the fuel pressure as long as you use a jumper to run the fuel pump continuously when doing so. The particular unit we installed displayed approximately 2 psi greater fuel pressure on the handheld than on my trusty Fluke 87.
Configure the Atomic EFI
Here, we simply configure the Atomic EFI to work with the engine combination in the Chevelle. Using the handheld controller we access the INITIAL SETUP menu.
This entire process takes just minutes to complete.
Here are the data items that you enter:
NUMBER OF CYLINDERS
Stock= Less than 210 degrees of duration
Medium= 211 to 230degrees of duration
Large= 231 to250 degress of duration
FUEL PUMP TYPE (more accurately, fuel system type)
- Returnwith a regulator
IDLE RPM TARGET: Input the RPM at which you’d like the engine to idle at operating temperature
REV LIMIT: Set a high-speed rev limiter
TIMING CONTROL: Choose Disabled for now
Once you’ve input the basics, you need to input the following in the ADVANCED SETUP:
FANS: Set the ON temperature for each electric fan
A/F TARGETS: Set the target A/F ratio at idle, cruise, and WOT
TIMING CONTROL: You address this in Stage Two
PUMP SQUIRT: Leave the factory setting for now
POWER VALVE ENRICH: Leave the factory setting for now
Adjust the Throttle Blades
The final step before attempting to start the engine is to set the throttle blades. This process is done based on the camshaft in the engine. According to the Atomic installation manual, the Chevelle’s camshaft qualifies as Large so we set each of the throttle blades at “11 ⁄2 turns from the point at which the blades first move.”
Start the Engine
Now it’s time to start the engine. Keith turned the key from the RUN to the START position, and the engine started immediately, and I do mean immediately. Nice!
Take a Test Drive
Before going for a drive, we allowed the engine to reach operating temperature and made a few final adjustments to the throttle blades and Idle RPM Target setting on the handheld. We also verified that the alternator was indeed producing enough current to keep up with the demands of the ECU, fuel pump, and injectors as we estimated it would. No problem.
After we were happy with the idle, it was time for a victory lap. We took ours on a 119-degree day in June, which just happened to be a record for that day in Phoenix. The Chevelle ran flawlessly. I held the handheld controller and monitored the A/F ratio as the Atomic was mapping the fuel tables to hit the pre-programmed targets. Wow, this process is fast, so fast that it’s hard to detect that it’s even happening.
The Chevelle never ran anything but smooth from the time we pulled it out of the shop until we returned, but it continued to get progressively smoother with each additional mile. Keith had a big smile on his face and was very happy with how the Chevelle ran.
Keith drove the vehicle for a bit. Its engine was equipped with the existing Mallory HEI distributor. He noticed that the Chevelle tended to surge between 2,500 and 3,000 rpm at a steady speed after he had driven it for a few weeks. Keith had slightly changed the A/F targets in the Atomic’s fuel map to the following in an effort to resolve this:
In addition, he increased the fuel pressure by 2 psi. Neither resolved the problem. After discussing this with him at length, I asked him to provide these details on the specifics of the timing in the engine:
Initial: 16 degrees
Total: 32 degrees
Vacuum Advance: 10 degrees
Timing All In: by 3,000 rpm
We decided to get together the following week to analyze the problem. In preparation, Keith installed a second bung in the exhaust so that we had a convenient place to connect my Innovate LM-2 handheld wideband oxygen meter.
After driving the vehicle 30 miles to my place, Keith took me for a ride and it ran perfectly. According to the Atomic handheld, coolant temperature was 200 degrees F and incoming air temperature 108, which is to be expected on a 108-degree Phoenix evening. Try as he may, Keith was simply unable to get the Chevelle to surge or exhibit any problems. It ran perfectly at any speed and any RPM.
We decided to move forward with our original plans to collect some data in hopes that we could replicate the problem. To that end, I wanted to monitor some things over time as Keith attempted to replicate the problem. These included the A/F ratio and the fuel pressure (so we could rule out a fuel delivery issue).
Yes, the Atomic handheld provides real-time data on both. However, datalogging the above as Keith drove the Chevelle allowed us to closely analyze the data after the drive in an effort to pinpoint the problem. I typically assume ESO (equipment smarter than operator) until I find otherwise. Acquiring data is an excellent way to remove the guesswork and get down to solving the problem and that’s just what we intended to do.
We connected my Fluke 87 DMM/ Fluke PV350 and Innovate LM-2 wideband oxygen meter. Both the Fluke 87 and the Innovate have datalogging capability. The Fluke 87 datalogs via the MIN/MAX mode. You simply press the MIN/MAX button to begin datalogging and press it again to end datalogging. Then, pressing the MIN/ MAX button repeatedly allows you to scroll through MIN(minimum), AVG (average), and MAX(maximum) readings during the time lapsed. The Innovate LM-2 datalogs via the internal SD Card by pressing the RECORD button once to start the datalog and a second time to stop the datalog.
In the time it took us to connect the equipment, air temperature dropped to 95 degrees and coolant temperature dropped to 180 degrees. We didn’t make it too far before we noticed the Chevelle running differently in the cruise area and sure enough it surged just like Keith had reported. The cause was immediately obvious on both the LM-2 and the Atomic handheld. The A/F ratio was jumping up and down from 12.0 to 16.0 as Keith held the throttle at a constant RPM between 2,500 and 3,000. The Chevelle ran perfectly under nearly every other condition, including WOT.
While driving around, fuel pressure was rock solid at 47.8 psi on the Fluke, even when the Chevelle was surging. At WOT, the log in the Fluke showed that fuel pressure dropped to 45.8 psi (a decrease of only 4 percent), which is perfectly logical considering how much fuel the engine is consuming. The fuel pressure remained sufficient with this nominal 4-percent drop. This data allowed us to rule out a fuel delivery issue. We didn’t need to make a log with the LM-2 as the problem was obvious. I think it’s worth mentioning that the Atomic handheld displayed similar data, so a passenger paying very close attention should be able to obtain similar information.
I’m not an expert in tuning but you don’t need to be one to install and set up one of these systems. That’s why I took on this project and documented the process. My buddies Bill Surin and Frank Beck are both excellent tuners and excellent resources. In the following days, I discussed Keith’s Chevelle with them and came to the conclusion that the likely cause of the surging was too much ignition timing, too lean of a mixture, or both.
Frank recommended we lower the target A/F ratio in the cruise area to 13.5:1 and disconnect the vacuum advance of the distributor and report back. Guess what? This solved the surging immediately.
Reducing the amount of vacuum advance (the Mallory canister is adjustable) and slowly leaning the mixture to achieve the best fuel economy without surging was the next move. As I suspected earlier, all of the installed components were indeed working properly.
Fuel is an important aspect that must be considered because it is somewhat inconsistent from one gas station to another. In addition, some brands of fuel use detergents or additives while others don’t have the same chemistry. These inconsistencies can certainly play a role in drivability of an aftermarket EFI system. I recommend picking a brand of fuel and sticking with it. When possible, refill at the same station. That way if a problem does arise, you know that it is less likely to be a result of fuel inconsistencies.
With the surging issue behind us, we elected to proceed to Stage Two (configuring the Atomic to manage the ignition timing). This allows us to easily tune the timing and A/F at a cruise via pressing buttons on the handheld controller to achieve our goals.
Stage Two: Add Complete Engine Management
In this stage, we upgrade the ignition system so that the Atomic system can also manage the engine timing. This allows us to use the Atomic to its fullest capabilities. This upgrade permits complete control of the ignition timing parameters via the handheld, automatic timing retard when coolant temperature and/or intake air temperature reach a certain point, and automatic timing retard when a nitrous system is engaged.
1. Upgrade the Ignition System
The Mallory HEI Distributor needs to be removed and a completely different ignition system installed for us to allow the Atomic to manage the timing. The distributor needs to be matched to the requirements of the Atomic EFI system because it acts as the trigger for the ECU and the ECU in turn triggers the ignition system. Fortunately, the Atomic system has been designed to interface with all MSD Pro-Billet (magnetic trigger) or MSD Ready-to-Run distributors. Either way, you need an outboard ignition box. (MSD provides excellent diagrams for either scenario on their website.)
Keith’s Chevelle is the exception rather than the norm because most of the cars I see at the cruises have one of the above distributors and a 6AL ignition box. We elected to use an MSD Pro-Billet distributor and referred to Figure 5.50, which is printed in the Atomic EFI installation manual.
In addition, you need an adjustable rotor and the balancer must be degreed. If your balancer isn’t degreed, you can use timing tape (MSD PN 8985). Finally, you need a timing light.
We elected to use the following ignition components from MSD:
The Digital 6AL ignition box has a detachable plug and this greatly simplifies installation and troubleshooting. I wish all ignition boxes had this. In addition, the rev limiter of the Digital 6AL doesn’t require pills, is right in plain view, can be adjusted with a screwdriver, and has a water-resistant cover. I’m also a huge fan of MSD’s HVC series of coils (see chart on page 89).
The HVC coil has more than double the output current of the Blaster 2 and double the output power. I’ve had really good luck with MSD’s HVC and HVC II coils and I enthusiastically recommend them both. Sure they’re a bit more money, but well worth it.
The installation of these components is really simple and most enthusiasts have experience with all of them. The most difficult part is installing the distributor, which really isn’t all that difficult. I have to give MSD props here for the incredibly well-written installation manuals. If you follow them step-by-step, you simply cannot get lost.
If you’ve already got an MSD Ready-to-Run or Pro-Billet Distributor, a CD-style ignition box, and a coil, you save a bunch of time at this stage.
Position the engine at 15 degrees BTDC on the compression stroke before proceeding regardless of whether you remove your existing distributor or replace it altogether. Pull the driver-side valve cover and note the position of the number-1 exhaust and intake valves to determine advance. The compression stroke occurs after the intake valve event and both valves are fully closed during the compression stroke. I typically use a 27-inch-long-handle 1/2-inch ratchet with all the spark plugs in to turn the engine over; just like you see the guys do in the pits of any Top Fuel team.
You may elect to mark the orientation of the rotor before removing the distributor, especially if you want your existing plug wires to go back on the same way they came off. You can now remove the existing distributor.
On small-block and big-block Chevys, I typically orient the cap so that the number-8 and number-1 terminals are at the very front and point the rotor at the number-1 cylinder when installing the distributor, but that’s personal preference. It’s another excellent trick I picked up from Frank Beck.
Lock Out Distributor
Because the Atomic EFI ECU controls the timing, it’s necessary to lock out the distributor, thereby eliminating any centrifugal and/or vacuum advance. This process is outlined fully in the Atomic EFI installation manual as well as in the distributor manual so I’ll not repeat it here.
Install Adjustable Rotor
Install the adjustable rotor in place of the rotor provided with the distributor. Two screws anchor it in place. Phase the rotor by retarding it by 15 degrees. Note that the MSD rotor has up to 20 degrees advance or 20 degrees retard and the rotor is marked accordingly. To retard the rotor, you move the rotor in the opposite direction that the distributor rotates. Think about that for a second and it will absolutely make sense.
Use red thread locker on the set screw for the rotor; you do not want it to come loose.
You may now install (or re-install) the distributor in the engine. Ensure that the rotor ends up pointing at the number-1 terminal of the cap. On small-block and big-block Chevys, it can be an arduous process to get the rotor pointing exactly where you want it because you most likely have to manually rotate the oil pump driveshaft to permit it.
The Chevelle didn’t disappoint, and we spent a few minutes with a long flat-blade screwdriver getting the shaft exactly where we needed it to be. Leave the hold-down clamp just loose enough to move the distributor to set the timing.
Install Ignition Box
Keith constructed a small steel plate for the ignition box that allowed us to mount it up high on the passenger side. This plate also permitted us to use the rubber isolators on all four corners of the box.
We chose a location on the firewall toward the driver’s side of the brake components to install the coil. This location permitted us to use the rubber isolators on the HVC coil on all four corners, which are an integral part of the mounting scheme of this (and the HVC II) coil.
This is actually very simple and not much more is involved than installing the ignition box on its own (see Figure 5.50 for more details). Notice that the distributor’s magnetic pickup plugs into the red pigtail on the ECU and not into the matching input of the ignition box as you may expect. This allows the distributor to trigger the ECU and in turn trigger the ignition box via its points-style input. This is accomplished by connecting the yellow wire from the ECU to the white wire on the box.
We elected to cover all of the wiring in split-braide tubing, which was the most time-consuming part of the wiring job. The HVC coil includes a pigtail with a Weatherpack plug on it. It also includes the mating connector for the harness from the ignition box. We used both.
Once all of the components were mounted, I had all of the wiring completed in less than one hour. While I worked on the wiring, Keith grounded the coil to the firewall via the included ground lead, fabricated a plug wire between the coil and distributor, and connected all the plug wires as before.
2. Set Up Atomic EFI to Manage Timing
Now that the ignition system is installed, we’re minutes away from firing the engine. Before doing so, we need to make a few changes via the handheld controller. We use it to calibrate the timing settings. The process is covered in the Atomic EFI installation manual, but you should follow these steps to perform the initial setup:
Turn the ignition ON
Using the handheld controller, select INITIAL SETUP
- Select TIMING CONTROL
- Exit INITIAL SETUP
- Select ADVANCED SETUP
- Select IGNITION TIMING
Select IDLE RPM: Set the RPM at which the advance begins to come in—think centrifugal)
Select TOTAL RPM: Set the RPM at which all of the advance is in
Select IDLE ADVANCE: Set the initial timing
Select TOTAL ADVANCE: Set the total timing
Select VACUUM ADVANCE: Set additional advance for idle and cruise, based on vacuum via the MAP sensor
We chose the above timing settings (to start, at least), based on the original ignition curve of the Chevelle.
Lock the Timing via the Handheld Controller
Next, cycle the ignition key OFF and then back ON.
Once back ON, go to ADVANCED SETUP, select IGNITION TIMING, and then select LOCK TIMING.
This allows you to lock the timing in the ECU to 15 degrees BTDC. Locking the timing in the ECU allows you to set the distributor properly after you’ve started the engine.
Start the Engine
Have your timing light connected and ready. Keith turned the key and the Chevelle cranked for a few seconds and then came to life.
Once the engine is running, rotate the distributor so that you read 15 degrees BTDC on the balancer and then tighten the hold-down clamp to lock it in place.
Exit the LOCK TIMING screen via the handheld controller.
The Atomic EFI is now managing the timing as you’ve programmed it. This whole process took Keith and me about 5 hours and that included taking all of the photos you see here. This was an incredibly easy upgrade and MSD’s instructions were very well written.
After buttoning everything back up, reinstalling the air cleaner, and putting the tools away, it was time to take the Chevelle for a spin. For now, we left the target A/F ratio in the cruise area at 13.5:1. The Chevelle ran perfectly and climbed through the RPM smoothly.
We pulled over and I nudged the target A/F ratio in the cruise area to 14.0. We drove it some more with the same results.
I then nudged the target A/F ratio in the cruise area to 14.1 and we drove it some more. It surged the slightest bit at first and then settled in nicely very shortly.
Overall, Keith and I were very happy with how the Chevelle ran.
The best fuel economy comes with the A/F ratio closest to stoichiometric and the most timing you can get within the cruise area. Each engine combination is a little different in this regard, and Frank always tells me, “Give it what it wants.”
Allowing the Atomic to manage both engine timing and fuel metering makes it extremely easy to arrive at this for any applicable engine combination by making changes on the handheld, even while the engine is running.
After driving the car for a few weeks with the ignition upgrade, Keith was very happy with the overall performance of the system. He made a few tweaks to fine-tune the drivability.
So, was the ignition upgrade worth the cost of the components? Absolutely, and I do mean absolutely! Being able to manage all of the ignition parameters and all of the fuel metering parameters from the handheld controller couldn’t be simpler. This allows you to quickly fine-tune the system to work optimally with your combination. Finally, you can make very fine adjustments to the total timing in the quest for the best performance.
Any EFI system is only as good as the weakest link. The combination of parts we chose for Keith’s Chevelle were instrumental in delivering the exact kind of performance expected from such an EFI conversion. I’m blown away by how easy this conversion was and how well it performs. More important, so is Keith.
Written by Tony Candela and Posted with Permission of CarTechBooks