 EMD's mechanically assisted turbocharger eliminated the need for the pair of Roots blowers and also integrated the turbocharging function from two (Elliot) or four (AiResearch) smaller add-on turbochargers into one much larger, turbo-compressor (turbocharger) with intercooling.The introduction of the EMD-type turbocharger was successful and all subsequent GP series were offered with this turbocharger, although not all models within a series were offered with turbocharging (e.g., the "38" sub-models within the "40 Series" were Roots-blown).Units built for the Great Northern Railway were equipped with high short-hoods and were set up to run long-hood forward with a single control stand.