Let's say that you are driving a Diesel Multiple Unit^† with either mechanical^* (ie an actual gearbox with multiple ratios) or hydraulic (ie two or more torque converters) transmission. When you move the “go faster” lever to a higher notch, what exactly is being commanded? Possibilities that I can think of:

• Higher mass flow of fuel into the engine cylinders, whatever happens after that, happens
• Engine governor set to a higher rpm, whatever happens after that, happens
• Something else

This weirdly specific question does relate to query put to me on behalf of a client, but I'm not being paid to solve it.

^† My question is specifically about DMUs—and not locos—examples of the kind of train I'm interested in include: Class 150 Sprinter and Class 172 TurboStar

^* although unusual, and for a long time considered obsolete, there are still mechanical transmissions for this application in production. For example the Voith DIWARail pack for small railcars, derived from a bus power pack, and I believe that ZF offer a similar solution.

Let's say that you are driving a Diesel Multiple Unit^† with either mechanical^* (i.e. an actual gearbox with multiple ratios) or hydraulic (i.e. two or more torque converters) transmission. When you move the “go faster” lever to a higher notch, what exactly is being commanded? 

Possibilities that I can think of:

• Higher mass flow of fuel into the engine cylinders, whatever happens after that, happens
• Engine governor set to a higher rpm, whatever happens after that, happens
• Something else

This weirdly specific question does relate to a question presented by a client, but I'm not being paid to solve it.

^† My question is specifically about DMUs — and not locos — examples of the kind of train I'm interested in include: Class 150 Sprinter and Class 172 TurboStar

^* Although unusual, and for a long time considered obsolete, there are still mechanical transmissions for this application in production. For example, the Voith DIWARail pack for small railcars, derived from a bus power pack, and I believe that ZF offer a similar solution.

Let's say that you are driving a Diesel Multiple Unit^† with either mechanical (ie an actual gearbox with multiple ratios) or hydraulic (ie two or more torque converters) transmission. When you move the “go faster” lever to a higher notch, what exactly is being commanded? Possibilities that I can think of:

• Higher mass flow of fuel into the engine cylinders, whatever happens after that, happens
• Engine governor set to a higher rpm, whatever happens after that, happens
• Something else

This weirdly specific question does relate to query put to me on behalf of a client, but I'm not being paid to solve it.

^† examples include: Class 150 Sprinter and Class 172 TurboStar

Let's say that you are driving a Diesel Multiple Unit^† with either mechanical^* (ie an actual gearbox with multiple ratios) or hydraulic (ie two or more torque converters) transmission. When you move the “go faster” lever to a higher notch, what exactly is being commanded? Possibilities that I can think of:

• Higher mass flow of fuel into the engine cylinders, whatever happens after that, happens
• Engine governor set to a higher rpm, whatever happens after that, happens
• Something else

This weirdly specific question does relate to query put to me on behalf of a client, but I'm not being paid to solve it.

^† My question is specifically about DMUs—and not locos—examples of the kind of train I'm interested in include: Class 150 Sprinter and Class 172 TurboStar

^* although unusual, and for a long time considered obsolete, there are still mechanical transmissions for this application in production. For example the Voith DIWARail pack for small railcars, derived from a bus power pack, and I believe that ZF offer a similar solution.