The lineage of the Railfan often involves the polarizing topic: Which builder makes the Best Diesel Locomotive. Well railfans, hopefully this will be the path to set this argument free, so we can move onto other topics like: Evil-Digital vs. Film!

Here is how the Engines were analyzed:

Thermal Efficiency

This realtes to how much energy is lost from the engine to the Traction Motor. late Model DC-motor units are 83% efficient, while newer AC-motor units are in the low 90% (depending on who you ask!)


The number One job of the Locomotive is to Pull. So, its only fitting the ability be measured in terms of Adhesion, or how much Locomotive weight is transfered into Pulling power.

Train Power

The final sub-category, and the trickiest to explain/understand (trust me, this ain't rocket science!). CTE (Continuous Tractive Effort) is the benchmark that defines the pulling power of the Locomotive @ the rails. CTE basically says, this is the maximum continuous pulling force this locomotive can sustain indefinitely @ a certain MCS (minimum Continuous Speed). So, whenever we see CTE listed...it should have a speed reference close by. CTE varies highly from locomotive, but also individual locomotives of the same design. A few alterations with Ballast, etc. can change the CTE@MCS dramaitcally. The Train Power equation is CTE/(2000*MCS). This gives us a score from 0-10, 10 being the highest. Currently, only a few Locomotives are scoring over a 7...which is a relatively GOOD score.

The final Performance Score is:

(10*(Thermal Efficeincy%*100)+(Adhesion%*100)+Train Power)= Performance Score.

So, here are the results for the AC Locomotives.

Locomotive Builder Score TEff% AdH% TrP
AC4400CW GE 100.87 92 35 8.82
AC6000CW GE 96.11 92 40 8.29
ES44AC GE 94.22 96(est.) 35 8.11
SD70ACe EMD 92.56 92 35 7.99
SD90MAC EMD 89.24 92 35 7.67
SD70MAC EMD 87.01 92 33 7.45
SD90MAC-H EMD 86.73 92 40 7.35
SD89MAC EMD 82.56 92 35 6.99
SD80MAC EMD 78.86 92 35 6.60
SD60MAC EMD 77.82 89 30 6.59