The LS vs Coyote Engine Debate: Maximizing Performance on E85

For decades, the battle between General Motors' LS platform and Ford's Coyote engine has defined the American performance landscape. Both powerplants represent engineering peaks from their respective eras—the LS with its lightweight, pushrod simplicity and the Coyote with its modern, dual-overhead-cam sophistication. But as alternative fuels reshape the industry, a new question emerges: which engine is better optimized for E85? With ethanol's higher octane rating and unique combustion properties, the answer depends on how well each platform adapts to this fuel. This guide breaks down the technical nuances, component requirements, and real-world performance gains for both engines running E85.

The LS Engine Platform: Proven Simplicity

General Motors introduced the LS family in 1997, and it quickly became a benchmark for V8 performance. The engine's architecture—cast-aluminum block, six-bolt main bearing caps, and deep-skirt design—provides a rigid foundation that handles significant power. The pushrod valvetrain keeps the package compact and lightweight, contributing to its popularity in engine swaps and dedicated performance builds.

Key LS Design Characteristics

What makes the LS so adaptable to high-performance applications, especially with E85, starts with its fundamental engineering choices:

  • Aluminum block and heads reduce overall weight, improving vehicle balance and thermal management under high load.
  • Deep-skirt block construction supports the crankshaft securely, reducing flex at elevated RPM and power levels.
  • Six-bolt cross-bolted main caps resist crankshaft walk under extreme combustion pressures common with high-octane ethanol blends.
  • Hydraulic roller camshaft reduces friction and allows aggressive lobe profiles without excessive valvetrain wear.
  • Distributorless ignition with individual coil packs improves timing control critical for E85 tuning.

Aftermarket Ecosystem

The LS aftermarket is arguably the most extensive of any modern engine family. Companies like Summit Racing and Texas Speed offer everything from complete short-block assemblies to standalone fuel-injection systems. This breadth of support means that sourcing E85-compatible components—injectors, fuel rails, pumps, and lines—is straightforward. The LS platform's popularity also means tuning support from reputable calibrators like HP Tuners and Holley EFI, which offer robust E85-specific tables for fueling and spark advance.

The Coyote Engine Platform: Modern Technology Meets Muscle

Ford launched the Coyote 5.0L in 2011 as a clean-sheet design intended to replace the aging Modular V8. Unlike the pushrod LS, the Coyote uses twin independent variable cam timing (Ti-VCT) and a four-valve-per-cylinder head design. This architecture allows the engine to breathe efficiently across a wider RPM band, delivering impressive specific output from the factory.

Key Coyote Design Characteristics

The Coyote's technological sophistication presents both advantages and challenges when optimizing for E85:

  • Dual overhead camshafts with four valves per cylinder improve volumetric efficiency and allow precise control over intake and exhaust events.
  • Ti-VCT system adjusts cam timing independently on intake and exhaust cams, enabling broader torque curves and higher peak power.
  • Plasma-transferred wire arc cylinder liners reduce weight and improve heat transfer compared to traditional cast-iron sleeves.
  • Forged connecting rods in Gen 2 and later provide strength for boosted applications, though fuel-system upgrades remain necessary for high-ethanol blends.
  • Direct injection introduced in Gen 3 complicates E85 conversion due to high-pressure pump limitations and injector flow constraints.

Aftermarket Ecosystem

While not as expansive as the LS market, Coyote aftermarket support has matured significantly. Ford Performance offers a full line of crate engines and control packs, and specialty shops like Livernois Motorsports provide fuel-system upgrades and custom tuning. The Coyote's integration with Ford's OEM electronics can pose challenges for standalone tuning, but solutions from companies like Holley and Powerteq are bridging the gap.

Understanding E85 Fuel: Chemistry and Practical Benefits

E85 is a blend of 85% denatured ethanol and 15% gasoline, but the actual ethanol content can vary seasonally and regionally. Ethanol has a research octane number of approximately 109, compared to 91–93 for premium pump gasoline. This higher octane rating allows for increased compression ratios, more aggressive ignition timing, and higher boost levels in forced-induction applications.

Thermal and Combustion Properties

Ethanol's latent heat of vaporization is significantly higher than gasoline's. This means that as the fuel vaporizes in the intake port or cylinder, it absorbs more heat, cooling the charge air. The resulting denser air-fuel mixture supports higher power output. However, ethanol also has a lower energy density by volume—about 33% less than gasoline—requiring proportionally more fuel flow to achieve the same power level.

Fuel System Demands

Because E85 requires roughly 30–40% more fuel volume than gasoline for stoichiometric combustion, fuel-system capacity becomes critical. Standard OEM fuel pumps, injectors, and lines designed for gasoline will often be undersized for E85 operation. Upgrading these components is non-negotiable for reliable performance on high-ethanol blends. Fuelab and other aftermarket suppliers offer dedicated E85-compatible pumps and regulators to address this requirement.

Optimizing the LS Engine for E85

The LS engine's relatively simple fuel system and robust bottom end make it well suited for E85 conversion. The pushrod architecture allows for larger fuel injectors and high-flow fuel rails without complex disassembly. Here are the critical modifications for a reliable E85 LS build:

Fuel System Upgrades

  • Larger fuel injectors: For naturally aspirated LS engines targeting 500–650 horsepower, injectors sized at 60–80 lb/hr (at 3 bar) are typical. For forced induction, 100–160 lb/hr injectors may be necessary.
  • High-pressure fuel pump: A Walbro 450 or dual-pump configuration is common for E85 builds, ensuring adequate flow at full throttle and high RPM.
  • Fuel lines and rails: Stainless steel or PTFE-lined hoses resist ethanol's corrosive effects better than rubber. Larger diameter lines (typically −6 or −8 AN) reduce pressure drop.
  • Fuel-pressure regulator: A return-style regulation system maintains consistent pressure across the injectors, improving tuneability and idle quality.

Ignition and Tuning Considerations

E85 requires approximately 25–30% more ignition advance at low loads and slightly less at high loads compared to pump gas, depending on compression ratio. The LS engine's coil-near-plug design supports the precise timing control needed. A custom calibration from a tuner using HP Tuners or Holley EFI is essential to adjust the volumetric efficiency tables, spark advance maps, and fuel target tables specifically for ethanol.

Additional LS-Specific Modifications

  • Camshaft selection: A cam with 112–114-degree lobe separation angle works well with E85, as the fuel's burn characteristics benefit from shorter overlap. A 220–240-degree duration (at 0.050) is common for street/strip builds.
  • Compression ratio: With E85, compression ratios up to 13.0:1 are feasible for naturally aspirated builds without detonation, compared to 10.5–11.0:1 on pump gas.
  • Intake manifold: LS3-style or aftermarket composite manifolds with larger plenum volumes help supply the increased air demand when running higher compression and more aggressive cam timing.

Optimizing the Coyote Engine for E85

The Coyote engine presents a more complex conversion path due to its variable cam timing and, on Gen 3 models, direct injection. However, the rewards in terms of throttle response and power density are substantial when the fuel system is addressed properly.

Fuel System Upgrades for Gen 1 and Gen 2 Coyotes

  • Injector sizing: Gen 1 and Gen 2 engines use port fuel injection, which simplifies injector upgrades. Sizes of 52–80 lb/hr are common for naturally aspirated builds making 450–550 wheel horsepower.
  • Fuel pump: The OEM pump in Gen 1 and Gen 2 Mustangs can handle moderate E85 blends (up to E50), but for full E85, a dual-pump return-style system from companies like VMP Racing is recommended.
  • Fuel line and rails: The returnless OEM system must be converted to return style when fuel demand exceeds the factory pump's capability. A fuel rail with standard −6 AN inlet and crossover ports simplifies the installation.

Gen 3 Coyote Direct Injection Challenges

The Gen 3 Coyote (2018+ Mustang GT) uses both direct injection (DI) and port fuel injection (PFI) in a dual-fuel system. The DI system operates at pressures up to 3,000 psi, and the high-pressure fuel pump cannot flow enough volume for full E85 operation above moderate power levels. The solution involves adding supplemental port injectors or replacing the entire fuel system with a high-flow inline pump and aftermarket DI injectors. This adds cost and complexity but allows the Gen 3 engine to exploit E85's full potential.

Cam Timing and Tuning

The Coyote's Ti-VCT system requires careful recalibration for E85. Ethanol's slower burn speed benefits from increased cam overlap at certain RPM ranges, but the optimal timing differs from gasoline. An experienced tuner using software like HP Tuners or SCT can adjust the camshaft timing tables to maximize torque across the RPM band. On Gen 3 engines, the DI and PFI blending strategy must also be recalibrated, which demands deeper access to the ECU's control logic.

Additional Coyote-Specific Modifications

  • Cold-air intake: A high-flow intake reduces restriction and helps the engine breathe against the increased fuel volume requirement.
  • Exhaust system: Long-tube headers with 1.75–1.875-inch primary tubes improve scavenging and support the higher exhaust flow from the increased airflow through the engine.
  • Oil cooler: Ethanol combustion produces more water vapor than gasoline, which can lead to oil dilution in short-trip applications. An external oil cooler helps maintain oil temperature above the condensation point.

Comparative Analysis: LS vs Coyote on E85

Power Potential

Both engines respond strongly to E85. On a naturally aspirated build with similar displacement and compression, the LS typically offers a 5–10% peak power advantage due to its lighter valvetrain and lower parasitic losses from the pushrod architecture. However, the Coyote's better stock cylinder head flow often yields a wider torque curve, particularly in the 4,000–7,000 RPM range. With forced induction, the gap narrows significantly, as both platforms can produce well over 1,000 horsepower with appropriate fuel system upgrades.

Fuel Economy

E85 yields lower fuel economy than gasoline in both engines due to its lower energy density. However, the LS's shorter, more efficient combustion event at low RPM tends to produce slightly better economy in cruising conditions compared to the Coyote, which requires more fuel enrichment at high load to manage its higher-revving nature. Expect a 20–30% reduction in miles per gallon on E85 for both engines compared to standard fuel.

Cost of Conversion

The LS engine's simpler fuel system and massive aftermarket support make it the more cost-effective platform for E85 conversion. A complete fuel system upgrade for an LS can range from $800 to $2,500, depending on injector size and pump configuration. For a Gen 1 or Gen 2 Coyote, the cost is similar, though the return-style conversion adds $300–500. Gen 3 Coyotes are significantly more expensive, with supplemental port-injection kits adding $2,000–$4,000 to the build, not including tuning costs.

Reliability and Maintenance

E85 is corrosive to fuel-system components not designed for ethanol, particularly rubber seals, fuel hoses, and aluminum fuel rails with insufficient anodization. Both engines require ethanol-compatible components to avoid long-term damage. The LS's lower rev limit (typically 6,500–7,200 RPM in street builds) places less stress on valvetrain components compared to the Coyote's ability to rev past 7,500 RPM. However, the Coyote's timing chain and tensioners are more robust than early LS timing chain setups, which can stretch under high load.

Applications and Use Cases

Street Performance

For a daily-driven street car, the LS engine with a mild cam, 12.5:1 compression, and a simple E85 conversion offers excellent throttle response, good low-end torque, and reliable cold-start behavior. The Coyote is equally capable but requires more attention to cold-start tuning, especially in colder climates where ethanol’s lower vapor pressure can make starting difficult. Both engines benefit from E85’s knock resistance, allowing drivers to run aggressive timing without fear of detonation.

Drag Racing

In quarter-mile applications, the LS engine’s torque advantage off the line and lighter overall weight often translate to lower elapsed times, all else being equal. The Coyote’s higher-revving powerband can compensate with faster shifting at higher RPM, particularly in cars with gearing optimized for 7,000+ RPM operation. Both platforms see significant gains from E85 with proper fueling, and many champion drag cars run both families successfully.

Road Racing and Track Days

The Coyote’s dual-overhead-cam design provides the RPM headroom needed for road courses where sustained high-speed operation is common. The LS engine’s compact size and lower center of gravity offer chassis packaging advantages. On E85, both engines run cooler intake air temperatures, reducing the risk of heat soak during extended track sessions. However, the increased fuel consumption on E85 may require larger fuel cells or more frequent pit stops.

Conclusion

The LS and Coyote engines each bring distinct strengths to the E85 conversation. The LS platform excels with simplicity, cost-effectiveness, and a proven aftermarket ecosystem that makes E85 conversion straightforward for builders of any skill level. The Coyote responds with greater refinement, a wider powerband, and a technological suite that rewards patients and careful calibration.

For most enthusiasts, the decision hinges on the vehicle platform and personal preference. If you own a GM vehicle or are performing an engine swap into a lightweight chassis, the LS is the pragmatic choice. If you are building a Ford Mustang or appreciate the challenge of extracting maximum efficiency from modern valvetrain technology, the Coyote offers a compelling path forward. In both cases, E85 unlocks performance gains that pump gas simply cannot match, making the investment in compatible components and professional tuning a worthy endeavor for any serious build.