Advanced Tuning & Injector Technology
"We’ve always appreciated stock fuel injectors for their reliability and consistent performance under heightened fuel demands. By upgrading the low-pressure fuel system and modifying the high-pressure fuel pump (HPFP) with a cam that enhances its stroke, we managed to elevate fuel rail pressure close to 3500 psi. This tactic effectively increased the lb/hr flow rate of the injectors, which follow a Bernoulli-like principle: higher pressure equals greater fuel flow.
Manipulating the start of injector timing was key to accommodating our E85 and 25+ psi boost needs. However, upon deeper analysis, we realized optimization was still amiss. Our developed software visualized the piston's position relative to injector timing across the RPM range, revealing fuel injection occurring while the exhaust valve was open and extending well into the compression stroke. The result? Injector pulse widths surpassing 7ms at 6000 RPM.
Enter XDI Injectors, offering a 50% increase in fuel delivery. This upgrade allowed us to refine injector timing, syncing it closely with the closing of the exhaust valve and optimizing initiation during the intake stroke. The outcome was not just theoretical; we observed tangible improvements. Keeping boost levels, timing, and AFR constant, we escalated from a 7.51 1/8th mile at 91mph to a 7.38 1/8th mile at 93mph. This breakthrough signifies not only a present win but the potential for future enhancements, ensuring our capacity to meet increasing air demands. We're thrilled to see what lies ahead with this upgrade, truly a game-changer in fuel injector technology!"
"Pushing our record-setting car to new power heights brought an unexpected challenge: a decline in the transmission's shift speed and consistency. Ahead of Drag Week, we dove into upgrades, starting with a Sonnax zip kit in the valve body, designed to stabilize pressure with enhanced seals and valves. The impact was immediate, slashing our 2/3 upshift time from 0.7s to 0.4s. We hit Drag Week confident but quickly faced transmission flares, ending our hopes for a 10-second E.T average.
The following eight months were a deep dive into the transmission's nuances and countless calibration refinements. We emerged with an intimate understanding of the TCM system, its data sources, and how they intertwine to forge swift, consistent shifts. The result? We transformed erratic .4-.7s shift times to a steadfast .1s! This precision not only safeguards the transmission by minimizing heat from clutch slippage but also ensures smoother handling and repeatable drag strip performance. We're now proud to extend these services to all GM 6-speed 6L45/50 transmissions.
Our ECM calibration journey also brought insights into mitigating Low-Speed Pre-Ignition (LSPI). Extensive oil testing and data analysis revealed that engine temperature and load were primary LSPI catalysts. By adjusting the transmission's upshift points and widening the gap between upshift/downshift points, we effectively reduced LSPI incidents. These discoveries underscore the intricate relationship between ECM and TCM calibrations and their collective role in enhancing engine health and performance."
Introduction
Here is an overview of our daily-driven 2014 ATS+4. We put this car together just as a reliable driver—maybe run mid 12s—and just enjoy it. Things, as they do, kept progressing, but the main heart of the car hasn’t changed.
Teaser
- We have 35k miles on this build, with 25k of those miles on our XDI injectors.
- The car ran 11.77 @ 117 mph in the ¼ mile using the same tune we daily drive year-round in Michigan.
- Averages 21–22 mpg on full E85. Only maintenance has been spark plugs once, plus regular oil changes.
Below, we’ll dive deeper into the parts used, lessons learned, and what we might do differently for our next build.
2. Engine Components & Strategy
2.1 Overview of Engine Goals
We wanted an engine that combined good reliability with affordability. At the time, we were between garages and had ZZP build/install the long block. It’s a fairly basic build using their components, and as of this writing, I have nothing but positive feedback on what we received.
2.2 Short-Block & Internals
- Pistons: ZZP pistons (4302 forgings). We like that we can run a tighter piston-to-wall clearance, ideal for a year-round driver. Our end-gap measured .023–.025. (In our other car with JE pistons, we set them at .029–.031.)
- Rods: ZZP rods. They appear physically more robust than Molnar rods, though we use Molnar in other builds as well.
- Crank: Stock.
- Balance Shafts: Retained, since we don’t spin above ~6700 RPM.
Lessons Learned: The short block has been extremely solid. I wouldn’t change anything—just a basic forged engine build that’s worked great.
2.3 Cylinder Head & Valve Train
- Springs & Retainers: ZZP springs and titanium retainers. They add spring pressure, which helps control the valves under higher cylinder pressures. They aren’t cheap, but until a beehive-style option is found, these have proven effective—even on stock cams.
- Camshafts: ZZP fuel cam (a stock cam reground to ~30% more stroke on the fuel lobe). We haven’t upgraded the HPFP, yet we haven’t run out of headroom.
- Valves: Stock. They’ve been perfectly fine.
- Head Studs: ZZP 8740 studs. With this turbo size, they’ve been sufficient; no issues so far.
Lesson Learned: We plan to add a ported head and stronger studs in the future, but that’s for performance expansion, not reliability concerns.
2.4 Turbo Setup: Z54
- Turbo: Z54 (ZZP’s version of the BW 6758), featuring a journal bearing instead of the lightweight turbine. Given its cost and potential output, it was ideal for our goals.
- Manifold: Stock GM.
- Downpipe: ZZP catted.
Lessons Learned: For the cost, we wouldn’t change a thing. Our Z54 has outperformed similar 20G, MHI, and Z57 setups. If budget allowed, we’d consider a BW supercore or ZFR. We actually have a BW supercore ready, but can’t justify swapping it out yet since this setup runs so well.
(Call-out): Looking for custom injectors or advanced calibrations? Our Tuning Services can help with bigger turbos, fueling needs, etc.
3. Fuel System Upgrades
- Fuel Pump: 5th Gen ZL1 pump. Contrary to popular belief, this is the same pump used in later ZL1 and CTS-V models. Our version doesn’t require extra lines for the aux side, making installation easier.
- Fuel Cam: As above, we’re using the ZZP intake cam with an enlarged fuel lobe. Perfect for our current power level.
- Injectors (Stock): Initially ran these on full E85 for ~9k miles. Combined with the fuel cam and ZL1 pump, we could push to ~400 HP levels. We were cautious about aftermarket injectors at that time.
- XDI Injectors: Once XDI released LTG injectors, we gave them a shot. After dialing in the tune, they became a no-brainer upgrade. We dropped 0.3 seconds in the ¼ mile and still have plenty of headroom—where stock injectors were nearly maxed out.
- Flex-Fuel: ZZP flex fuel sensor. If E85 is accessible, use it! It makes better power than race fuel, costs less than 87 octane, and lowers LSPI risk.
Promoting Our Injector & Tuning Business: We spent lots of time perfecting injection timing and rail pressure to optimize fueling on Gen V platforms. XDI injectors are now almost plug-and-play. Still, fine-tuning fuel pressures and pulse width is critical—especially on bigger turbos and E85 setups.