The idea of developing a vehicle that’s easy to drive on the street while being capable of laying down fast ETs at the strip has been the goal of countless hot rodders for decades. However, the approach has traditionally been fraught with compromise. The “analog” nature of carburetors, in particular, often requires constant adjustments to extract the full potential from an engine combination in both scenarios. But as Holley Performance’s Ryan Witte explains, an electronic fuel injection system can dramatically improve this situation.
“The ability for an EFI system to self-adjust is a real game changer in that regard. If you’re running a carburetor on a naturally aspirated engine and you want to switch between fuels, for example, you might have to change jets and mess with the distributor to adjust timing. It can get messy and a bit cumbersome. But with EFI, those adjustments are either automatically compensated for or can be changed in just a few seconds using software. No fuss, no muss.”
Aftermarket EFI systems like the Holley Dominator or Terminator X offer the ability to save custom tunes that can be called up as needed, effectively creating custom “presets” for the fuel system that can be tailored to specific situations.
“Once you know what your settings are for your street setup and strip setup, you can swap between them whenever you want,” Witte notes. “With a system like the Dominator, you could even set it up so you can switch between tunes on the fly using a physical two-way selector switch in the vehicle.” An EFI system’s ability to automate and react to incoming data can also make life much easier for those running power adders.
“With a nitrous car, there are some real quality-of-life improvements,” says Witte. “With an EFI setup, your nitrous system is integrated into the operation of the fuel system – it’s not a separate system that needs to be managed independently. You’ve already got fuel injectors delivering fuel to the engine, so when I turn on the nitrous, I can simply tell the injectors to spray more fuel – I don’t need separate jets, plates, nozzles, or other components in the nitrous system to handle the fuel. And if you want to change the fuel for your nitrous system, you can do that without touching anything mechanical – you just hop on the laptop, call up the tune in the ECU, and make the change. The same goes for the timing: I can tell the system to move the timing wherever I want it to be when the nitrous is on, and it’s automated as part of the EFI system’s operation based on how you’ve set up the tune.”
Shop Holley EFI Kits and Components Now
DIFFERENT NEEDS FOR DIFFERENT SITUATIONS
You may be asking yourself, “OK, that’s cool, but my carb is dialed in, and I’m happy with how my car is running. Why would I need the ability to switch between a street tune and a drag strip tune?” As Witte explains, it ultimately comes down to what you’re leaving on the table.
“Because fuel injection is constantly adjusting on its own as the car runs, it can maximize the efficiency of the engine in various situations. If you’re at wide-open throttle, the ECU can do what it’s tuned to do at wide-open throttle, and if you’re cruising, it’ll adjust accordingly – all without any manual intervention. A lot of people who run carburetors end up making adjustments to improve drivability while cruising or to enhance wide-open performance, but what they don’t realize is that one affects the other. With EFI, that doesn’t happen.”
With Holley’s EFI software, users also have the ability to adjust nearly a thousand different points across the engine’s operating RPM range. This allows you to precisely tweak settings to your preference, anywhere you need to, without inadvertently compromising the fuel system’s behavior elsewhere.
Witte says that when it comes to differences between street and strip-specific tunes, the engine combination plays a crucial role in the strategy.
“With a naturally aspirated car, there would probably be very little that needs to change unless you’re switching between two different types of fuel. You might have your timing dialed in a little higher for your street tune to make it cruise a bit nicer – or vice versa, depending on how you’ve set up your car.”
He also says that supercharged setups are similarly straightforward. “One good tune could likely handle both scenarios. But if you wanted to be extra safe, you could pull a little timing and add a little fuel in the boost areas for the street tune. That would reduce the risk of damaging something.”
Turbo setups are where things start to get interesting, though. “Here you’re not as focused on the fuel and spark because those things are automatically adjusted for varying boost levels,” he points out. “What you’re adjusting is how much boost you’re making. That’s something you could set up to switch between tunes on the software, or even control manually with a switch or dial. You can also choose how quickly you want the boost to come in to help dial in your launches, and the EFI handles the rest.”
With throttle-by-wire engines, the EFI system can even adjust throttle sensitivity, which can improve both street drivability and traction at the drag strip. “With the LS and other late-model engines, you can change how quickly the throttle reacts, and how it reacts based on the throttle pedal’s position. It’s really straightforward – in the software, it’s a line that you adjust. You flatten it out to slow down the system’s reactions. It’s similar to the differences in throttle behavior between Normal and Sport drive modes in today’s high-performance cars.”
Systems like the Holley Dominator EFI also offer transmission control right out of the box, which can further adjust the powertrain’s behavior for different types of driving. “Here, you might set it up for softer shifts earlier in the rev range with your street tune,” Witte suggests. “Then when you go to the track, you max everything out, making it shift as hard as it can at more aggressive shift points.”
PLAN OF ATTACK
Witte tells us that establishing a clearly defined game plan ahead of time is key to creating an effective dual-purpose fuel system setup.
“Any time you’re making the switch to EFI, you’ve got to figure out what your needs are because that will determine the hardware required to get there. Do you need transmission control? Do you need boost control? Are you running two different types of fuel? Defining those things before you make a purchase really helps a lot.”
Once the necessary hardware is installed and functioning properly, he says the best way to tackle a new dual-purpose setup is to start with the drag strip tune.
“Your idle and basic operating parameters are going to be the same for both, so you can create a baseline tune that you’ll use for both the street and track tunes. With that baseline, it should be starting, idling, and cruising well. Once you’ve got that squared away, focus on the race tune and the outer boundaries – basically, how much power you can safely make. Once you’ve established that, you can decide how much you want to back it off for the street tune. Over the past few years, I think a lot of people have discovered that a thousand-horsepower turbo LS can be a real handful to drive on the street. Having a tune that’s designed to make it easier to wrangle can make it much more enjoyable to drive.”
Using that 1000hp turbocharged LS as an example, he suggests dialing things back during initial testing for the street tune. “Turn it all the way down and test it. How does it feel? Is it fast enough for the street? Odds are, even on the wastegate, it’s going to be pretty lively for street use. You can always dial things up from there to find the balance that feels ideal.”
With a nitrous setup, Witte recommends dialing in the naturally aspirated tune first. “Full throttle on a naturally aspirated engine is just full throttle – it wants the fuel and timing that it needs. Once you’ve got the naturally aspirated tune sorted, the part that’s really track-specific is related to activating the nitrous and tuning for it.”
Holley EFI software offers a section dedicated to nitrous tuning. Parameters include how much fuel to add and how much timing to remove. “There are two ways to do the timing part,” says Witte. “You can either just set the value you want – ‘I want ten degrees of timing, and that’s it’ – or you can set up an offset to the main spark table based on either RPM or time since the nitrous was activated.”
From there, you can also adjust how the nitrous is implemented. “You might want to delay the nitrous coming on, or only have it on for a certain amount of time, or both. You can also make it progressive, so when you turn it on, it ramps up based on the parameters you set instead of giving you all of it all at once. These adjustments are about dialing the system in for the amount of traction you have to work with more than anything else. The fuel and timing are about keeping the motor safe – if you get those wrong, you’re going to have a bad day.”
When it comes to refining the tunes, there’s always room for subjective improvement.
“You’re never done,” Witte says with a laugh. “You know you’ve reached a good point when the car runs how you want it. And that’s why it’s important to have a goal in mind when you start working on this. Once you’ve achieved the first goal, set a new one and start working toward it. When refining the track tune, the ETs will usually guide the way – how quick or fast did it go? Use one of those as a metric to determine if the changes you’ve made are improving performance, and then optimize the tune with that metric in mind.”
