EFI Swapping A Dragster With A Holley Sniper Stealth 4500: Part 2

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EFI Swapping A Dragster With A Holley Sniper Stealth 4500: Part 2


Making the decision to move from a carburetor to electronic fuel injection (EFI) for grassroots bracket racing is a big deal, but the parts you actually need really aren’t that exotic at all. We’re using a Holley Sniper Stealth 4500 EFI system to convert a big block dragster over to fuel injection and in this article we’re going to look at what type of ignition you need, the benefits of the Sniper system, and how it worked at the track.

The Holley Sniper systems boast an impressive array of features that can work with a variety of engine applications. To bring the Sniper to life a user just needs to follow the installation instructions, but they also need to make sure their vehicles fuel system and ignition system are right for EFI. In the previous article, we looked at the fuel side of what the Sniper 4500 requires, this time around we are going to examine what kind of ignition system a user needs when they add a Sniper 4500 to their engine.

EFI Ignition Basics For Drag Racing

The basic ingredients that are needed for an internal combustion engine to function are fuel, air, and spark, so having plenty of power in your ignition system is vital. There are a few different types of ignitions that are commonly used in drag racing applications: captive discharge (CD), inductive coil, and magneto ignitions. A CD style ignition fires off a large amount of energy quickly, the inductive coil system uses a lower amount of energy but it will discharge it longer, and a magneto ignition provides a hot spark at a constant rate.

One of the best things about the Sniper system is the fact you don’t need a fancy ignition system or power source. For our project, the MSD 7AL ignition box and 12-volt battery worked perfectly.

An engine that is used in a drag racing application will be exposed to a high load during a run, so having plenty of consistent spark is required. Mathew Lunsford from Holley talks about why you need that strong spark to light off the combustion process in a high-performance engine.

“Engine output only happens if the fuel is ignited – so making sure there’s enough spark energy to consistently fire the spark plug through the different loads of drag racing is important. If the spark cannot jump the gap between the electrode and the ground strap of the spark plug, the result may be a short duration misfire or cylinder that can never recover as fuel is still being introduced. Either of these problems will throw the balance of the engine off and can make a big difference in ET and performance at the track.”

 The main thing to look for in an EFI ignition system is one that matches the potential of the engine. – Mathew Lunsford

A Millijoule (mJ) is the unit of measure for spark output an ignition system can produce. The greater the output of Millijoules at the spark plug, the more cylinder pressure the spark plug can endure and still produce ignition inside the cylinder. What that means is as an engine increases in performance potential, so does the amount of Millijoules the ignition system needs to produce for it to function correctly.

“The main thing is to make sure that the spark energy is matched to the power potential of the engine. You don’t use an MSD 6 box on a high boost/horsepower engine because it may not have enough spark, so you would use an MSD Grid, MSD 7 or even the MSD 8 box because of the energy at the spark plug they can produce. In general terms, you cannot put too big of an ignition system on an engine but you can put to small of an ignition system on one for sure,” Lunsford explains.

Ignition And The Sniper System

Keeping things simple is one of the biggest attributes the Sniper system has to offer, it makes the process of completing an EFI swap a task that most racers can do. What helps make that possible is the fact the sniper system can be added to an engine to deliver fuel only while using the vehicle’s current ignition system. The Sniper system only needs an RPM signal that can be provided from the tach out of the CD ignition box, which means the ignition system that ran the engine when the carburetor was in place can still be used.

So, will your ignition work with a Sniper 4500 system? Lunsford explains the three main “puzzle” pieces that are needed to make an EFI ignition system function.

“The first thing you need is a way to get the RPM signal to the EFI system, in this case, we’re talking about the Sniper 4500. A locked-out MSD Pro-Billet distributor with a phase able rotor, Holley EFI Dual Sync Distributor, Sniper EFI Hyperspark Distributor, or an MSD crank trigger can all do this. You also need to have a CD ignition box that can communicate with the EFI system. Any CD box that takes a 12-volt square wave trigger can do this so most, if not all, ignition boxes on the market are capable to work with the Sniper system. The ignition box must also be appropriately matched to the horsepower output of the engine, this is critical for everything to work. Finally, a coil driven by the ignition box needs to be used. Different resistance coils react differently, so it’s best to match the coil to the specific ignition box being utilized.”

The dragster’s original MSD ignition products were more than capable of working with the Sniper 4500 to provide the required spark to the engine.

The Sniper system has the ability to do more than just control fuel only, if a user desires they can give the Sniper full timing control over their engine. While this isn’t a requirement for the Sniper system to work, it does give a racer a much larger toolbox full of tuning options.

With the Sniper system, you can program a timing curve that matches the engine better. -Mathew Lunsford

When the Sniper system has full timing control enabled you can use the built-in launch retard that functions off of the release of the trans brake, a specified amount of time, or a preset RPM level. The advanced tables in the Sniper software allow you to take advantage of a throttle stop by removing timing for a certain amount of time during a run. If you want to use a power-adder, the full-timing control function let’s use the Sniper’s boost and nitrous functions.

Lunsford provides more detail as to what advantages the full-timing control function adds to the Sniper system.

“Basically allowing the Sniper to take care of timing introduces a way to have ideal timing during all conditions with full timing control at different RPMs and load amounts. With a traditional mechanical advance, the only variable for the ignition control is centrifugal force which is directly correlated to RPM that the distributor is turning. At times you may have to compromise with higher initial timing to meet the wide-open throttle timing with the mechanical weight, cam shape, and springs in a traditional mechanical advanced distributor. With full timing control, you can use the Sniper software to build a 31×31 table (961 cells) that has different values for different RPM and load of the engine.”

When the full-timing control ability of the Sniper system has been selected, it uses the RPM signal along with the programmed timing values to send a signal through the points output wire at the correct time to meet the commanded ignition settings. At that point, the coil that’s driven by the ignition box will provide the distributor spark during the combustion process. The MSD Pro-Billet distributor, Holley EFI Dual Sync Distributor, Sniper EFI Hyper Spark Distributor, and MSD Crank Trigger kit all can provide the Sniper system with an RPM signal to engage the full-timing control function.

The dragster we used for the EFI conversion already had an MSD 7AL ignition box, MSD Pro-Billet distributor, and MSD Pro Power coil. For the installation of the Sniper system, all we did was tap into the tach signal to provide the Sniper with an RPM reading and that was it. The rest of the ignition system remained connected as it was when the dragster used a carburetor and we didn’t have to make any additional changes to get the Sniper system to function as it should.

Advantages Of Sniper 4500 At The Track And Testing

The technology that’s packed into the Sniper 4500 might seem a little intimidating, but as we talked about in the first article Holley makes setting up and using the system easy for anyone. What it takes to tune an EFI system is very similar to tuning a carburetor, the biggest difference is how precise you can be with EFI tuning.

The Sniper system has the ability to bring more consistency to a race car, something that every bracket racer highly covets. Lunsford talks about how the Sniper system can unlock more consistent runs for any vehicle as conditions change during a race day.

“With the Sniper system, you can program a timing curve that matches the engine better. This allows you to taper ignition timing out of the engine above peak power/higher RPM if desired. You also will know the timing is going to do exactly what you have programmed in the EFI, it doesn’t matter if that’s at the release of the transbrake or five seconds into a run. You can program different timing offsets based on the temperature of the engine coolant so you can try to keep the output of the engine consistent as the engine heat soaks. There’s also the ability to have the car leave softer to reduce inconsistencies at the launch and then have full-timing come in after a certain time from launch to allow the car to have some MPH out the back.”

The handheld screen for the Sniper mounted perfectly right behind the driver and can be accessed to turn on any function needed.

After we went through the setup wizard and got the car started it was time to get a feel for how the new system would work and we were very pleased right from the start. When you first power on the Sniper it requires you to go through the setup wizard and answer some basic questions about your engine, such as displacement, target idle speed, style of camshaft, and if you have a power-adder. From there, the setup wizard works its magic and creates a base tune map from all of the data that Holley has collected from other engines. After that, the ECU will begin to tune on its own and you don’t have to do anything else for the base tune-up.

The first thing we had to do was ensure the car would move on its own without any system issues and that test was passed with flying colors. We also did a quick two-step and transbrake test before our trip to the track so we could confirm everything worked, and once again the Sniper delivered without any issues.

We loaded the dragster up and headed to National Trail Raceway in Hebron, Ohio for some late season testing. Rick Doerr, the driver of the dragster, noticed some differences in how the car ran and behaved before it even turned the tires for a burnout.

“Before we installed the Sniper system on the engine it would really struggle to start at times and just didn’t like to run when it was cold. I would have to really let the car warm up before I could drive it to tech or it would have a hard time running correctly. It would also want to hesitate when I would try to do a burnout or when I left the line even after we tried tuning on the carburetor. Now the car fires right up and runs without any of the issues it had before.”

The best run the dragster had ever made before the conversion to EFI was 8.494 at 151 MPH. We took the dragster out for some testing before the conversion and it ran in the 8.50s with a best pass of 8.516 at 146 MPH with a 1.20 60-foot and 5.288 in the eighth-mile at 126.92. We didn’t make any adjustments to the car at all during that test session so we could get a good feel for what it was doing before the swap.

For the first run on the car, we didn’t want to make a full pull so we could be sure everything was functioning under a load. The first 200-foot pass netted a 1.30 60-foot time, not far off the last 60-foot time the car ran previously. On the following pass, Rick made a half-track run and that produced a 1.29 60-foot time and ET of 5.386 at 128 MPH. The third and final pass of the test session Rick made a full quarter-mile pull and ran an 8.435 at 158 MPH with a 1.26 60-foot time and 5.366 eighth-mile time. During the testing we didn’t’ make any adjustments to the tune-up at all, this was all accomplished through the Sniper’s self-learning functions. The timing was locked in at 12-degrees, just as the engine builder set it when he assembled the engine. This is what makes the Sniper system so easy to use: you don’t have to make any adjustments to the timing unless you want to.

We loaded the car up happy with the results since the car ran better plus it was able to remain consistent during the test session. Overall the switch to EFI with the Sniper Stealth 4500 EFI system was surprisingly painless and easy. We now have a solid baseline with the car going into the 2020 racing season that we can use to make adjustments for consistency. Not only did the dragster perform better, but the testing data also shows the car was able to stay relatively consistent without any adjustments. The 1/8-mile e.t. tells us the car should lay down consistent times within a few hundredths on each pass, and that’s pretty good without any tuning. With some additional tweaks, we should be able to make this dragster run nearly dead-on its dial-in every pass.

If you’re on the fence about making the switch to EFI due to how indicating it is you can rest easy, the Holley Sniper Stealth 4500 EFI system really works as advertised and is worth taking a look at if you want to improve your race car’s consistency at the track.



DragzineDragzine – EFI Swapping A Dragster With A Holley Sniper Stealth 4500: Part 2

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