When upgrading your fuel system, remember it’s a “system”

By Staff Writer
Jul 14, 2022 | Sponsored Content, Fuel system, Deatschwerks | Posted in News and Notes | Never miss an article

Photography Courtesy DeatschWerks

Sponsored content presented by DeatschWerks.

One day we may just plug our cars into the dryer outlet for max performance, but for now there’s still plenty of power (and cool noises) to be had from internal combustion engines. And a vital part of making that combustion as efficient as possible for max performance is a fully optimized fuel system.

And they key word there, of course, is “system.” Upgrading fuel delivery is rarely a single-part endeavor, and while that can place some additional burden on your wallet and shop time, taking a more holistic approach to your fuel upgrades can pay off in better performance and better control over that performance.

We recently had to take such a look at the fuel system in our 1991 Toyota MR2 Turbo. We’d eventually like to run it on E85 for ethanol’s superior tendencies, particularly with turbocharged engines, but we also don’t want to lose the ability to run pump gas when E85 isn’t as convenient.

[E85 Ethanol Fuel: How to Corn Your Way to More Horsepower]

So we talked to an expert. Dakota Bowman is one of the tech geniuses at DeatschWerks, a full-line supplier of fuel system components. Luckily, Bowman says, technology and manufacturing quality has caught up to enthusiasts’ desires to increase performance.

Ethanol requires a lot more flow volume than gasoline, which means larger injectors, more pump volume, and generally more capacity than a pure gas system,” Bowman explains. “And in the past, it was sometimes tough to find an injector that could effectively ‘downsize’ the flow for normal gas. But with modern manufacturing and materials, it's much easier for larger injectors to act as smaller injectors when they need to.”

The takeaway message when sizing injectors: Size for your highest-power scenario. To find our upper end, we input our MR2 Turbo’s specs and horsepower goals into DeatschWerks’ fuel injector calculator.

Assuming a goal of 325 crank horsepower–say, about 280 wheel horsepower–on E85, the calculator says we’ll need injectors capable of providing 633cc/min. of fuel. Using the same target power with gasoline requires only 487cc/min. of fuel.

Since we want to run E85 when it’s available, we’ll look for injectors in the 650cc/min. range. These will provide plenty of headspace for E85 and can also be dialed back by the ECU when gasoline is being used.

But you also have to supply fuel to those injectors, and here’s where we start talking in terms of systems rather than individual pieces.

High-flowing injectors require more flow from the fuel pump. In the case of our MR2, the fuel pump calculator on DeatschWerks’ web page tells us that our reasonable power levels are easily attainable, even with the brand’s most modest pumps. Get up into the realm of 500-plus horsepower, however, and fuel requirements become heartier.

While pumps of any capacity are available with a click, Bowman reminded us to not neglect the wiring going to that new pump. “Especially if you’re modifying an older car, where the wiring harness is starting to dry out, we recommend that everyone upgrades the fuel pump wiring when upgrading a pump,” he explains. “A truly high-volume pump can draw as much as 15 amps of electricity. Do you really trust 30-year-old wire originally designed for half that capacity?”

Speaking of 30-year-old parts on the car, that spiffy new fuel system is also going to need proper pressure control. For us, that meant the original fuel system that was designed around 30-year-old power levels, when 200 horsepower was considered a lot. That’s likely not enough for today.

The actual fuel lines probably have enough physical capacity to feed the engine what it needs,” Bowman says, “but condition should definitely be taken into account, particularly with older cars. In regards to E85, we kind of use the rule of thumb that anything from the mid-1990s on is probably E85 compatible, but ’90s cars are now 30 years old, so you’re probably going to be replacing supply lines based on age alone.

But really,” he continues, “if you’re upgrading injectors and pump, your original fuel pressure regulator is probably not going to cut it at increased power and flow levels. Some gains are possible on newer cars with stock pressure regulators, but remember, those cars are designed to operate within a fairly narrow range of variables.

Maybe they can compensate fine for altitude changes, or temperature, or gas quality variances, but if you’re trying to take an engine and add 30 or 40% more horsepower via boost or parts changes, you’re going to quickly find yourself outside the range of what your stock bits can compensate for. So a high-quality regulator is a key to getting a properly metered fuel supply.”

The true benefit of ungraded fuel system hard parts is only going to be as good as the software controlling them, he adds: “The hard parts alone aren’t always going to make a difference. What matters is how they’re being controlled. The point of upgrading is giving yourself reliable, high-quality parts that are going to work exactly the way you want them to, exactly when you want them to, for a long time. But controlling them all comes down to proper tuning.”

For this reason, Bowman recommends that you always pair fuel system upgrades with the best quality tune you can manage. For some cars, this means reflashing the factory ECU using a system like HPTuners or some other software package that can crack the factory encoding and reprogram the stock computer.

For other users, particularly owners of older cars with more limited onboard control systems, this also means making the decision to moving to a standalone ECU. The good news: Aftermarket ECUs are becoming more and more affordable all the time, and any modern standalone is going to be orders of magnitude more powerful than a factory computer from even a decade ago.

[How to make the move to an aftermarket ECU]

But the point to all this is that your fuel system is a true system. Upgrading a single part ultimately does very little to affect the whole process. When undertaking fuel system upgrades, remember that you’re likely starting down a path of holistic change before true gains can be realized.

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