Stop / Start Fuel Saving and Emissions Reduction - Jury Still Out

The Jury Is Still Out On Stop/Start

Like it or not, though, this technology is here to stay.

As a fuel-saving and emissions-reducing technology, auto stop/start technology has been widely adopted by all of the major OEMs. It has gained a following similar to that of the hybrid, but it has not necessarily been well-received by everyone in the enthusiast communities. Most of the complaints come from “old-school” gearheads, and revolve around concerns over accelerated wear of the starter and internal engine components.

As for the general motoring public, it seems their biggest concerns are the perceived delay on restart and the learning curve of getting used to the vehicle “dying” at a stoplight in the first place. Like it or not, this technology is here to stay. The OEMs are using it as another way to improve their advertised MPG ratings, and to reduce their overall fleet carbon emissions in an effort to meet tougher regulatory requirements around the world.

Auto stop/start is considerably more complex than just shutting off the engine at a red light. It involves input from several sensors, and only occurs when a set of predetermined conditions are met. This helps to prevent engine wear and maintain passenger comfort.

Like many other emissions-related functions, auto start/stop relies on the vehicle being at operating temperature, and in closed-loop status. When the driver comes to a complete stop, a battery sensor confirms that the battery voltage and condition is sufficient to restart the vehicle. The ECU then shuts off the fuel supply and the power to the ignition system, stopping the engine. The braking system is integral to this function, as the ABS sensors must register a complete stop, and the brake-pedal sensor/stoplight switch must report that the driver is depressing the pedal.

Once the engine shuts down, the “auxiliary” electrical system takes over, maintaining lighting, the HVAC system and driver conveniences such as radio, navigation and hands-free phone interfaces without any power interruption. In order to achieve instant readiness for the power steering and automatic transmission during the repeated on/off cycles, many of these systems utilize electrically operated motors rather than belt-driven pumps. This increased electrical load during “engine-off” operation requires the use of an AGM or enhanced flooded battery, and some manufacturers also use a small auxiliary battery (similar in size to a powersport battery) as extra reserve power.

When the light turns green, the driver releases the brake pedal, initiating the restart sequence in as little as 0.3 seconds. The starter engages, the
engine comes to life, and the commute can resume. Starters designed for stop/start duty are engineered specifically for this purpose. While they’re built for repeated cycles, the additional cycles are actually less intense than the initial cold start, because the engine is already at operating temperature, and easier to crank over. Engine wear is kept to a minimum with the application of friction-modifying coatings on bearings, as well as surface hardening of traditional “wear” components such as cam lobes and lifters. Additionally, the oil doesn’t have time to drain back into the pan during an average stoplight cycle, as it would sitting overnight in your driveway.

For the few people who still have the pleasure of owning a stick-shift, stop/start works with a manual transmission too. With the transmission in neutral, and your foot on the brake, releasing the clutch pedal will initiate the shutdown process. As a grumpy, middle-aged car guy, I’m still not convinced that this technology is for me. As someone who appreciates the engineering and functionality of the system, I am convinced that many of our preconceived notions of auto stop/start are wrong. I’m also convinced that the addition of new and redesigned components to accommodate stop/start functions will lead to new opportunities for the aftermarket as these vehicles age out of their warranty periods.

You May Also Like

Tool Intel – Understanding Air Tool Fittings and Couplers

Why don’t air tools come with fittings installed? Here’s why customers need to buy what they actually need.

Your customers may be using air tools in a variety of circumstances for an even wider variety of jobs. Here's how to help them understand why they need to buy the right fitting for the application.

View Full Diagram Here

There are multiple different sizes and styles, and what one shop uses may not be the same as another. The size and style affect the volume of air they can deliver, a critical point because air tools require a specific pressure and volume for proper operation, and restrictive fittings can limit their performance. Here’s a look at the most common sizes and styles found in most automotive shops, and how you can identify them.

Read the April Digital Edition of Counterman

The April issue contains article designed for technical training, management efficiency and store profitability.

ASE Education Foundation Seeking Outstanding Instructor

Nominations are being accepted for the 2024 Byrl Shoemaker/ASE Education Foundation Instructor of the Year award.

Why Does Engine Coolant Need Replacement?

Two specifications can be used to justify replacement — the condition of the additive package & the freezing point.

Gaskets vs. Seals

Whether your customer asks for a gasket or a seal, you know one thing: They’re trying to stop a leak.

Gaskets and Seals

Other Posts

Collision Repair in the Age of ADAS 

In this video, discover how modern collisions impact a complex array of sensors, actuators, and electronic safety systems.

Electronic Stability and Traction Control

Their components work together seamlessly to help keep the vehicle under control.

Electronic Stability and Traction Control
Check the Part: Return Guide for CV-Joint Kit

Dorman offers these three tips to help to determine if it’s a valid warranty claim.

CV Joint Kit
Selling the Complete Brake Job

These simple guidelines will help you ensure that your customers have everything they need.

Brake Job