DI Fuel System – Problematic?
This was a reply to a customer a couple of weeks ago asking which injectors he should run in his Whipple truck. He was told by another tuner that the “had” to run ID1050’s and a triple pump Fore Fuel system at minimum, which is probably something that lots of you have heard regurgitated all over the internet by a bunch of people that don’t know what they’re talking about. So, here’s the truth. Spoiler alert…. you don’t need a $4k fuel system to run E85 on your Whipple’d F150.
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When we tune these trucks, we use the DI system to its fullest capacity. Because we are able to do that, you don’t need to run massive port injectors to run E85 and make power. A lot of other tuners don’t know how to use all of the capacity the DI system has to offer. My guess is that is because it’s a very complex and difficult system to understand and it’s very complicated to adjust it to get the most out of the system. When tuned properly, the stock DI system is capable of supporting around 500 whp on its own when running E85. Whereas if the person tuning your truck doesn’t know how to open up the system to extract maximum capacity from it, they will be lucky if they can support 300 whp on E85. Because of that, we don’t need to run massive port injectors to support higher power numbers.
My preference is always to use the Whipple injectors. Whipple injectors are dual-cone spray pattern and spray directly on the back of the intake valves which means they have much better fuel atomization, because the fuel vaporizes instantly when sprayed on the back of the hot intake valve, and that in turn means less fuel puddling on the walls of the intake port. When fuel puddles on the intake port walls, we call that “wall wetting” in tuner land, and it’s something that we try to avoid if possible. All of that basically means you get a smoother running engine and all-around better performance.
Any of the high-flow/larger injectors like ID1050 or FIC1000 have a single, pencil-like, spray pattern that sprays onto the divider between the valves in the cylinder head. That area is not nearly as hot as the intake valves. So, the fuel doesn’t vaporize instantly like when sprayed on the valves and at lower port velocities a lot of that fuel will stay on the wall of the intake port (wall wetting) instead of being pulled into the combustion chamber, meaning the combustion chamber has less fuel than what the PCM has calculated it needs to inject and the mixture will be slightly leaner than desired. Then when a high port velocity condition occurs, like transitioning to WOT, all of that excess fuel on the port wall gets sucked into the combustion chamber, causing over fueling (rich mixture) during that transition and can cause the throttle transition to feel “soft” or like there’s a dead spot. We call that “poor fuel metering” in the tuning world and it basically means that the engine will not run as smoothly or consistently as it could with an injector that provides better fuel metering.
In a purely racing environment, big injectors are typically worth the trade-offs that come with them. When an engine spends more time at WOT than it does at idle, the requirements you have for how that engine runs can be very different. However, 90% of these trucks see way more street miles than track miles, and nobody likes to deal with a street truck that doesn’t want to idle smoothly, has odd feeling throttle transitions, or gets poor fuel economy. The problem is that everyone thinks that if they spend $1000+ on injectors that they should magically be perfect for their application, and most of the time they are not.
There’s a reason why Whipple used the injectors they did. Because they have to pass CARB and EPA testing, and you can’t do that with an injector that sprays fuel all over the intake port and causes fuel metering from one engine cycle to the next to be all over the place. That’s also why if you look at Injector Dynamics website all of their injectors are listed for racing or competition use only. They say that because they’re not dumb, and they know the design limitations of their injectors.
It would be great if we had high-flow dual-cone spray pattern injectors, but those don’t currently exist. So, you have to choose the best compromise for your particular situation. On my personal trucks I run E50 with Whipple injectors and a JD Stage 2 fuel system. My 2025 is on a 3.25 pulley and my 2022 has our 8-rib kit and what would be the equivalent of around a 3.5 pulley and both trucks still have plenty of headroom in the fuel system. If at some point I decide I want to make more power and I exceed the current fuel system capacity, I’d likely upgrade the DI pump to extend the headroom, rather than installing larger port injectors. Neither of my trucks are race-only vehicles and I value a smooth-running engine more than anything else. So, I’m going to use the Whipple injectors as long as possible. In my opinion, until you’re making over 1000 whp, there’s no reason to install larger port injectors than the Whipple Stage 2 injectors and the way that we tune these trucks is what allows us to use the Whipple injectors to make the power that other tuners tell you that you need to buy $1100 injectors and a $3k fuel system to make. That’s simply not true, and I’m not going to force our customers to spend $4k that they don’t need to because I’m too lazy or too dumb to learn how something as important as the direct injection system functions. So, be aware of that when or if you talk to other companies. They’re going to tell you that you HAVE to run a $4k fuel system, and if they tune your truck that might be true, but not when we tune your truck. I’ve spent 100’s of hours learning how to tune this system to extract everything out of it that’s possible, and I choose to use that time investment to save our customers money.
Ken Osborne – Owner Oz Tuning, LLC.
