Introduction:
Are you ready to kick those Stromberg carburetors to the curb and embrace the sweet symphony of Dell’Ortos (Dellorto)? Curious about the love story between Lotus and Dellorto, or just looking to level up your carburetor knowledge with a bird’s-eye view of how Lotus used Dellortos over the years? Well, buckle up and read on—because things are about to get fuel-injected with knowledge (figuratively, of course)! This document delves into the various Dellorto carburetors employed on the iconic Lotus Esprit from 1977 to 1992. Most of these carburetors belong to the DHLA 45 series, with one notable exception: the DHLA 40H, which made its debut between 1980 and 1987.
To set the stage, imagine yourself in the mid 1970s: the Lotus Esprit S1 is unveiled, captivating car enthusiasts with its futuristic design. Under the hood, however, lies a crucial question—how to maximize performance and efficiency? Enter Dellorto, with their groundbreaking DHLA carburetor series, providing not only the needed power but also the finesse Lotus demanded for their engineering marvel. This partnership would go on to define an era of precision and performance. This document delves into the various Dellorto carburetors employed on the iconic Lotus Esprit from 1977 to 1992. Most of these carburetors belong to the DHLA 45 series, with one notable exception: the DHLA 40H, which made its debut between 1980 and 1987.
Purpose: The goal here is to identify which Dellorto carburetors were used on specific Lotus Esprit models and years, along with how to distinguish them based on tags, part numbers, and unique markings. Additionally, this document aims to discuss the significance of progression holes in influencing emissions, throttle response, and adapting to modern fuel types. The goal here is to identify which Dellorto carburetors were used on specific Lotus Esprit models and years, along with how to distinguish them based on tags, part numbers, and unique markings. Additionally, this document aims to discuss the significance of progression holes in influencing emissions, throttle response, and adapting to modern fuel types. It will also explore the interchangeability of these carburetors between models, highlighting which configurations may be compatible or require modifications.
Background on Dellorto and the Lotus Esprit
A Brief History of Dellorto
Dellorto began producing side-draft carburetors in the 1960s, aiming to outperform Weber in both design and performance. Their reputation in motorsports grew because they offered a blend of simplicity, reliability, and adaptability. Unlike many competitors, Dellorto carburetors excelled in providing consistent fuel delivery under high cornering loads, making them ideal for racing applications. Innovations such as the refined choke mechanism, refined progression circuits, and superior machining precision helped Dellorto capture the attention of performance enthusiasts and professional teams alike. Dellorto also integrated modular design elements that allowed for easier servicing and adjustments.
Another key advantage was their willingness to adapt designs to manufacturers’ needs. For example, Dellorto’s collaboration with Lotus led to custom carburetors optimized for both naturally aspirated and turbocharged applications, featuring enhancements like additional progression holes and seals for turbo setups. This flexibility and technical superiority set Dellorto apart from Weber and solidified its reputation among performance enthusiasts.
Why Lotus Chose Dellorto?
Lotus didn’t pick Dellorto carburetors for their Esprit models by accident. They chose them for their superior airflow, precise fuel atomization, and tuning flexibility—essential traits for engines that needed to sing as well as scream. Compared to the Weber DCOE, the Dellorto DHLA series brought smoother progression (thanks to their refined progression circuitry and additional progression holes) and better adaptability to high-performance setups. It was like giving a naturally gifted sprinter the perfect pair of running shoes.
But the relationship wasn’t just about performance—it was also about partnership. Dellorto was more than happy to roll up its sleeves and collaborate on custom configurations for Lotus. Need progression holes tailored to the quirks of the Lotus 907 engine? Dellorto delivered. Planning to strap on a turbo and wondering if the carbs would panic under pressure? Dellorto sealed their DHLA carburetors tighter than a drum, ready to handle boost without a single hiccup.
This willingness to customize fit perfectly with Lotus’s obsessive focus on lightweight, high-performance design. Together, they created a harmonious balance of precision and power that made the Esprit a legend.
Why couldn’t we get Dellortos in the USA?
The Dellorto DHLA 45E didn’t make it to U.S.-market Lotus Esprit S1 and S2 models, mostly because it couldn’t pass the emissions gauntlet Uncle Sam laid out in the 1970s. While it was thriving in Europe, tuned for performance and a bit of flair, the U.S. demanded all sorts of emissions wizardry like EGR systems and catalytic converters, and the 45E wasn’t up for the job without some major—and costly—tweaks. Lotus, being the scrappy underdog they were, went with Strombergs for the U.S., which got the job done but weren’t exactly setting enthusiasts’ hearts on fire.
The Lotus Esprit’s Engine Evolution
The Lotus Esprit relied on three major engine variants during its carbureted years:
- 907 Engine: Naturally aspirated. Used in the Esprit S1 and S2.
- 910 Engine: Turbocharged variants introduced in the 1980s.
- 912 Engine: Naturally aspirated. Both standard and high-compression versions powering later Esprits.
Dellorto Carburetor bodies used on the Lotus Esprit:
The following are all spin-offs (variations) of the original DHLA 45. The base DHLA 45 was never used on the Esprit from the factory.
- DHLA 45E: Lotus-specific, featuring six progression holes.
- DHLA 45D: Enhanced for high compression, one variant with power jet circuit.
- DHLA 45M: Turbo-pressurized, one variant with power jet circuit.
- DHLA 40H: Turbo-pressurized
Summary of Dellorto Variations on Lotus Esprit Models (1976–1992)
1976–1987 Naturally Aspirated Models
The naturally aspirated Lotus 907 and 912 engines from 1976 to 1987 utilized the DHLA 45E carburetor in various configurations. Early versions, such as those used on the 907 (S1, S2), featured no power jets and relied on simple but effective tuning with chokes sized at 36 mm. As the 912-engine evolved, power jets were introduced in the high-compression variant (1985–1987, Spec 10 Euro) to ensure adequate fueling at higher RPMs, reflecting the engine’s increased performance demands.
1980–1987 Turbo Models:
Turbocharged Lotus 910 engines in this era showcased a shift to specialized carburetors capable of handling pressurized systems. Early versions used the DHLA 40H for UK and export models with standard compression, which lacked power jets but included 36 mm chokes. By 1986, high-compression variants adopted the DHLA 45M, featuring tailored airflow with smaller 35 mm chokes but still no power jets. The USA-specific 910 models, however, used the DHLA 45M with a 110-size power jet to meet higher fueling demands under boost and stricter emissions regulations, demonstrating regional adaptation in carburetor design.
1988–1992 Naturally Aspirated and Turbo Models:
The final phase of development saw naturally aspirated 912 engines adopt the DHLA 45D, equipped with a 70-size power jet and larger 37 mm chokes, reflecting the demands of the high-compression 10.9:1 engine. Meanwhile, turbocharged 910 engines continued with the DHLA 45M, maintaining the same setup as earlier models but without power jets. This period solidified the separation between naturally aspirated and turbocharged carburetor configurations, with each optimized for their respective engine designs and performance requirements.
Through the years, Dellorto carburetors evolved alongside Lotus engines, showcasing increasing specialization, regional tuning adaptations, and engineering innovations to meet the unique demands of both naturally aspirated and turbocharged systems.
So, what does the Power Jet System do?
The power jet circuit in Dellorto carburetors provides additional fuel at high RPMs and under heavy engine load. It operates independently of the main jet and is designed to enrich the air-fuel mixture at higher engine speeds when the demand for fuel increases beyond what the main circuit can supply effectively.
- Location: The power jet is located in the carburetor body and is typically activated when the throttle is wide open, and airflow through the carburetor reaches a certain threshold.
- Purpose: It ensures the engine receives sufficient fuel at high RPMs to prevent lean conditions, which can lead to poor performance, detonation, or engine damage.
- Independent: Unlike the main jet, which works across a broader range of engine speeds, the power jet specifically targets high-RPM operation.
- Turbo Applications: In turbocharged engines, the power jet is particularly useful to compensate for the increased air pressure under boost, maintaining the correct air-fuel ratio for optimal performance and engine safety.
Conclusion and Closing Thoughts
Dellorto carburetors weren’t just a choice for Lotus—they were a necessity. Over the years, these carbs evolved to meet the specific demands of Lotus engines, from the naturally aspirated 907 to the turbocharged 910 and high-compression 912. The DHLA series introduced technical innovations like precision progression holes, sealed designs for turbo applications, and power jet circuits tailored to deliver additional fuel under heavy load or boost conditions.
Lotus’s original design intent was for the DHLA 45s to be used across the board, and the Strombergs fitted to U.S.-market cars were simply a compromise to meet emissions regulations of the time. If you’re a U.S. owner still running Strombergs, it’s time to let go of “good enough” and recapture the performance gains Lotus originally envisioned. Ditch the Strombergs and step up to the Dellortos—it’s not just an upgrade; it’s the way your Esprit was meant to run.
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