Short answer

Designers should prioritize the optimization of fuel injection timing and the use of multiple pilot injections to ensure smooth and stable engine operation during cold starts, thereby improving user experience and perceived vehicle quality.

Field: Human Factors
Source: Nottingham ePrints (University of Nottingham) (2013)
Method: Experimental investigation
Evidence: Strong effect

Adjusting fuel injection strategies and glow plug temperatures significantly improves the cycle-by-cycle stability of diesel engine combustion during cold idling, directly impacting noise, vibration, and harshness (NVH) and enhancing consumer perception of vehicle quality. This human factors research insight is drawn from a 2013 study published in Nottingham ePrints (University of Nottingham). Using Experimental investigation, researchers explored how this design variable affects real-world outcomes. The key design takeaway: Designers should prioritize the optimization of fuel injection timing and the use of multiple pilot injections to ensure smooth and stable engine operation during cold starts, thereby improving user experience and perceived vehicle quality.

Study

Human FactorsHigh ImpactStrong effect

Optimizing Diesel Cold Start Idle for Improved NVH and Perceived Quality

Nottingham ePrints (University of Nottingham) · 2013

Key Findings

01Shorter separation between pilot injections and between pilot and main injections improves combustion stability.
02Increasing the number of pilot injections stabilizes combustion across various cold soak temperatures.
03Higher glow plug temperatures (up to 1200°C) did not achieve stable combustion on their own.
04Increasing main injection quantity can stabilize combustion with fewer pilot injections, but may require additional ancillary devices.

Application

Design takeaway

How to apply

When designing or calibrating engine control systems for cold start conditions, implement algorithms that precisely manage the timing and number of pilot fuel injections to achieve a target level of combustion stability.

Project actions

01When investigating engine performance, consider the user's perception of quality as a key performance indicator.
02Focus on the transient phases of operation (like cold starts) as these often reveal critical design challenges.

Method & Evidence

AimHow do fuel injection strategies and glow plug temperature influence the cycle-by-cycle combustion stability of a diesel engine during cold idling conditions, and what is the impact on NVH and perceived quality?

MethodExperimental investigation

ProcedureA single-cylinder HPCR DI light-duty diesel engine with a low compression ratio was tested at temperatures ranging from 10°C to -20°C. Various fuel injection strategies, including the number and timing of pilot injections relative to the main injection, were explored. The effect of different glow plug temperatures was also investigated. Combustion stability was assessed by analyzing indicated work output and heat release characteristics. High-speed imaging of ignition in a combustion bomb was used to support the interpretation of engine results.

ContextAutomotive engineering, specifically diesel engine cold start performance.

Variables

IV["Fuel injection strategy (number of pilot injections, separation time between injections)","Glow plug temperature"]

DV["Cycle-by-cycle stability of indicated work output","Heat release characteristics","Noise, Vibration, and Harshness (NVH)"]

CV["Engine compression ratio","Ambient temperature","Engine speed (idle)","Fueling levels"]

Strengths & Limitations

Strengths

+Experimental investigation under controlled cold conditions.
+Focus on practical user-relevant outcomes (NVH, perceived quality).

Limitations

The complexity of real-world cold start conditions (e.g., varying ambient humidity, battery charge) may not be fully replicated in a simplified experiment.

Reliability & validity

The use of high-speed imaging and detailed analysis of indicated work output and heat release characteristics contributes to the validity of the findings. Reliability would be enhanced by repeating tests under identical conditions and ensuring consistent engine operation.

Think critically

To what extent can NVH improvements during cold starts compensate for other potential quality issues in a vehicle?

Design Principles

"Engine stability during critical operating phases, such as cold starts, is directly linked to user perception of quality and refinement."

The initial moments of a vehicle's operation, particularly after a cold start, are critical for user experience. Unstable combustion leads to noticeable NVH, which can negatively influence a consumer's perception of a vehicle's overall quality and reliability. By understanding and manipulating combustion characteristics, designers can create a more refined and positive user experience from the very first moment of operation.

What This Means for Your Design

Making small changes to how fuel is injected right before the main fuel injection can make a diesel engine run much smoother when it's cold, reducing annoying noises and making the car feel better built.

How to use in your project

1.Use this research to justify design choices aimed at improving user experience through technical performance enhancements, such as reducing NVH during specific operating conditions.

Add to My Project

Quick Cite

Paragraph starter

Research by McGhee (2013) highlights that optimizing fuel injection strategies, specifically the timing and number of pilot injections, is crucial for stabilizing diesel engine combustion during cold idling. This stabilization directly impacts noise, vibration, and harshness (NVH), thereby enhancing the consumer's perception of vehicle quality.

Source

Nottingham ePrints (University of Nottingham)

Factors influencing cycle-by-cycle combustion characteristics of a diesel engine under cold idling conditions

journal · 2013

View source

Questions About This Research

What does the research say about optimizing diesel cold start idle for improved nvh and perceived quality?: Designers should prioritize the optimization of fuel injection timing and the use of multiple pilot injections to ensure smooth and stable engine operation during cold starts, thereby improving user experience and perceived vehicle quality. Evidence: Nottingham ePrints (University of Nottingham) (2013).
Why does "Optimizing Diesel Cold Start Idle for Improved NVH and Perceived Quality" matter for design?: The initial moments of a vehicle's operation, particularly after a cold start, are critical for user experience. Unstable combustion leads to noticeable NVH, which can negatively influence a consumer's perception of a vehicle's overall quality and reliability. By understanding and manipulating combustion characteristics, designers can create a more refined and positive user experience from the very first moment of operation.
How can designers apply this research?: Designers should prioritize the optimization of fuel injection timing and the use of multiple pilot injections to ensure smooth and stable engine operation during cold starts, thereby improving user experience and perceived vehicle quality.
What were the main findings?: Shorter separation between pilot injections and between pilot and main injections improves combustion stability.. Increasing the number of pilot injections stabilizes combustion across various cold soak temperatures.. Higher glow plug temperatures (up to 1200°C) did not achieve stable combustion on their own.. Increasing main injection quantity can stabilize combustion with fewer pilot injections, but may require additional ancillary devices.
What research method was used?: Experimental investigation.
How strong is the evidence?: Evidence strength is rated Strong effect, based on a 2013 journal from Nottingham ePrints (University of Nottingham).
What should I do differently in my next project?: When designing or calibrating engine control systems for cold start conditions, implement algorithms that precisely manage the timing and number of pilot fuel injections to achieve a target level of combustion stability.
What are the limitations?: The study was conducted on a single-cylinder engine, and results may vary for multi-cylinder engines. The investigation focused on specific engine parameters and may not cover all potential influencing factors.