Sherman M4A2 Detroit Injectors

[Tony Smith]

And don't forget, too, Malcolm, that despite the presence of the Exhaust Valves in the head, the 6-71 is still a 2 stroke engine and the liners (specifically the port shapes and heights) control the timing of the Intake Cycle and cylinder scavenging, in much the same way as a camshaft controls valve timing.

Over the many years of the GM/Detroit Diesel engines, a wide variety of liners were developed to give different operating parameters, just as many 4 stoke engines had a range of camshafts for differing applications. The 6-71 has been used in Trucks, Earthmoving Plant, Locomotives, Boats, Gensets, Waterpumps (and even Tanks!). Each application had a unique need for power, torque and rpm range. The port shape in the liner is modified to optimise engine output to application.

[Malcolm Towrie]

Originally Posted by Tony Smith

And don't forget, too, Malcolm, that despite the presence of the Exhaust Valves in the head, the 6-71 is still a 2 stroke engine and the liners (specifically the port shapes and heights) control the timing of the Intake Cycle and cylinder scavenging, in much the same way as a camshaft controls valve timing.

Over the many years of the GM/Detroit Diesel engines, a wide variety of liners were developed to give different operating parameters, just as many 4 stoke engines had a range of camshafts for differing applications. The 6-71 has been used in Trucks, Earthmoving Plant, Locomotives, Boats, Gensets, Waterpumps (and even Tanks!). Each application had a unique need for power, torque and rpm range. The port shape in the liner is modified to optimise engine output to application.

Ah, yes, good point, Tony. So I should have said above that it’s effectively the ignition timing the varying injectors types can change.

Talking of 2-strokes, we have these two tanks and a bunch of military vehicles with Detroit 6V53’s, also 2-strokes. I knew they should all idle around 500 rpm, but it always sounded to me like they were idling way too fast. My light bulb moment was when I remembered that they were firing twice as fast at 500 rpm as the old rumbly 4 stroke gas engines I was used to!
Great old engines. We’ll never see the likes again.
Malcolm