For decades, companies like DiabloSport and Superchips have been helping enthusiasts unlock horsepower, drivability, and efficiency gains from their late-model vehicles with the pre-programmed calibrations in handheld tuners like the inTune i3 and F5 Flashpaq. But while the engineering behind adjustable features like throttle pedal response and speed limiters is relatively straightforward, the performance gains that these development teams have found – even with 87-octane fuel in naturally aspirated applications – can seem like black magic.

To get a better sense of how this dark art works, we went straight to source for the lowdown on calibration development and some insight into the differences between low-octane, high-octane, and custom tunes.

Unlocking Performance Potential

While the specifics tend to differ from one platform to another, Michael Litsch of DiabloSport tells us that when it comes to creating an aftermarket calibration for a vehicle, there are a few fundamental parameters that engineers will often look at during the early stages of development.

“Some of the core elements that we’re going to change in almost any application are things like commanded timing at part-throttle and wide-open throttle, with a stronger emphasis on wide-open throttle because that’s where you’re going to find those power gains. We’re also going to optimize the fueling; we’ve found that most factory calibrations run much richer than they need to, so there’s often a bit of power to be found there as well. And we’re also going to take a look at things like the catalytic over-temperature protection strategy – if it’s overly aggressive, sometimes we can pull back on that a little bit to keep it from dumping fuel constantly while still keeping things safe.”

But while higher output figures are always welcome, Jacob White of Superchips also notes that there are often other ways of improving real-world performance that aren’t necessarily reflected in peak power numbers.

“These days we often see factory calibrations that utilize a lot of torque management. In those situations, the calibration is actually limiting the amount of torque that the engine will deliver in different situations. So even in low-octane tunes where we might not have a lot of room when it comes to how much timing we can add, we can often still unlock a lot of power that the factory calibration just isn’t allowing you to utilize. And that’s going to yield better throttle response, more linearity in the torque curve, and better overall drivability.”

White explains that these torque management strategies are often developed with the specifics of the federal testing procedures for fuel economy and emissions in mind, and those strategies don’t necessarily translate to an optimized driving experience out in the real world. Accordingly, the development team at Superchips looks for these trouble spots in factory calibrations and corrects them while still maintaining 50-state emissions compliance.

“And these are power improvements that you’re more likely to notice on a day-to-day basis, too. You might not feel a big change at wide-open throttle, but in everyday driving situations those low-end torque gains really make a difference.”

Understanding Octane Tunes

Where applicable, handheld tuners like the i3 and Flashpaq include a pre-programmed calibration for use with low-octane fuel as well as another pre-programmed calibration that’s designed specifically for use with high-octane pump gas. While there are performance improvements to be had with either calibration, Litsch says that the parameters that engineers focus their optimization efforts on tend to vary between the two.

“With something like an 87-octane tune, which we typically offer for truck and SUV applications, the main difference is that we generally don’t modify the spark tables – the factory spark tables are typically designed for fuel that’s even lower than 87 octane because they have to account for those situations. We find that there’s rarely room to add timing here, so the performance improvements usually come from those other tweaks we can make – dialing in the fueling, optimizing throttle response, adjusting torque management and, in applications where we have control over it, optimizing transmission shift behavior. Fueling is a big part of it – getting rid of that overly-rich air/fuel ratio and dialing it in to something much more sensible will naturally allow the engine to make more power.”

White also cites fuel efficiency improvements as another benefit that can be had with low octane pre-programmed tunes.

“Those federal testing procedures we talked about earlier can affect a vehicle’s real-world fuel economy, too. These calibrations are designed around those testing procedures, and the criteria of those tests generally does not reflect how these vehicles are actually used out in the real world. So even with 87-octane tunes, we normally do see some fuel economy improvements alongside the performance improvements because we can design the calibration around how the vehicle is actually going to be operated.”

He also cites the recent influx of factory turbocharged engine combinations as another “lever to pull” when it comes to extracting more performance even when low octane fuel is involved.

“It’s something that can make a significant difference. With the 3.5-liter EcoBoost V6 in a Ford F-150, for example, we have this additional variable with the boost involved. A factory calibration might make, say, 18 pounds of boost, and in our tune we can ramp that up to 20 pounds of boost while keeping all of the factory safety parameters in place. So while our max gains with a naturally aspirated 6.2-liter Chevrolet V8 might be 40 horsepower, we could see as much as 95 horsepower in that 3.5-liter Ford EcoBoost.”

Shop DiabloSport tuners here.

But Litsch is quick to point out that while DiabloSport offers pre-programmed low-octane tunes in applications where the factory has designed the engine to be compatible with that type of fuel, many of today’s high-performance muscle cars and sportscars require the good stuff right out of the gate. In those situations, DiabloSport won’t try to reengineer things to make the engine run on a lower octane fuel than it was originally designed for. And besides, high-octane tunes give calibration engineers more opportunities to find additional performance.

“In naturally aspirated engines we mainly look to the timing for additional power gains over a low-octane tune, but the optimization strategies are otherwise very similar between low- and high-octane pre-programmed tunes here. With turbocharged engines, we can go further because the higher-octane fuel gives us more headroom to add boost. So there’s going to be some changes to the airflow tables and the commanded boost tables, along with changes to the fueling in order to support the additional airflow that we’re bringing in. And we tend to optimize supercharged applications for high-octane fuel in much the same way that we would with a naturally aspirated engine.”

Going Custom

Along with the included pre-programmed calibrations, DiabloSport handheld tuning devices also give enthusiasts the ability to install custom-built tunes on their vehicles. In contrast to the pre-installed tunes we’ve discussed here, a custom tune is a calibration that’s been tailor-made for a specific vehicle and its particular combination of parts. While there are typically additional performance benefits to be had with a custom tune on any vehicle, Litsch says that stepping up to a custom tune is effectively a requirement once certain engine modifications have been made.

“There isn’t a hard rule here because it’s application-dependent, to a degree – with some Ford Mustang applications, if you put a cold air intake on it, you need a tune that’s matched to that intake or the engine just won’t run right. So in that case you absolutely need a tune that’s designed to account for that specific cold air intake.”

But in most other cases, builders can go a few steps further before a custom tune becomes a necessity.

Shop Superchips tuners here.

“There are mechanical changes where it's effectively required. If you change the camshaft, for example, you’re going to need a custom tune no matter what – there’s no pre-programmed tune on the planet that’s going to run it. But there are also situations where you might not need a custom tune to get the vehicle to run acceptably, but you’re leaving performance and drivability on the table if you don’t go that route. While you might be able to get the car to run alright with long tube headers without a custom tune, it will certainly run better with one.”

Litsch adds that the majority of DiabloSport customers who run custom tuning are doing so with vehicles that have basic bolt-on upgrades like cold-air intakes and cat-back exhausts. “It’s a situation where they’ve decided to seek out a custom tune to find a little more power and dial in the car just a little bit further. Drivability is a big part of it, especially for the folks who have done a few modifications to the engine. If your airflow tables aren’t dialed in and the fueling isn’t right where it needs to be for that specific combination, you can wind up with drivability issues because the calibration doesn’t know what to do with the parts you have. And that’s a big part of the benefit of going with a custom tune.”

DiabloSport handhelds have a built-in data logging feature which calibration techs use to determine how to develop a tune that’s customized to a particular vehicle. “With our products you simply plug in the device, hit record from the data-logging menu, and start driving the vehicle around. In most cases the calibrator that you’re working with will give you a set of driving instructions. For example, they might ask you to start logging before you start the vehicle so you can record a cold start, then let it idle for a few minutes until it gets up to temperature, and then go drive for a few minutes at different speeds and different throttle positions. They will then create a custom calibration based on that data, and they’ll ask you to run through that same data logging process again to make sure the new calibration is functioning as expected. And once they’re happy with everything they’re seeing in the logs, you’re good to go.”

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Both Litsch and White also urge those who are new to the tuning game to reach out to their support lines with any questions they might have.

“Our support line is in-house and specific to tuning – it’s not a general tech line,” White points out. “So the folks on the other end of the line are well-versed on this subject regardless of whether you’re working with a Superchips, DiabloSport, or Edge device.”