G-226 fuel economy stats

It would seem that A-C was trying to better themselves in fuel economy on the G-226 engine from 1957 (the first D-17) to 1967 (the first One-Seventy).  Using Nebraska Test data, it has been documented that a D-17 gas made 52.72 belt HP at 1650 RPM and burned 4.535 GPH of fuel in November of 1957 at 62 degrees F air temp. So, ten years later in October with 75 degree F air temp, the new One-Seventy delivered 51.46 PTO HP at 1624 eng RPM's (540 pto speed) while only burning 3.986 GPH fuel. I calculate if the engine was tested at 1650 identical RPM as the D-17 engine, the fuel rate would be 4.049 GPH and HP to be at 52.28.  By raising the compression from 7.25 to 1 (M code) to 8.0 to 1 (Z code) the fuel consumption was reduced by 1/2 gallon per hour, (approx 11%) to develop nearly the same HP !! I think this is pretty remarkable considering the One-Seventy had a hydraulic system that was flowing 8 more GPM continuously than the D-17 did !!  Also, in recent information seeking, the compression increase wasn't the only thing different. The One-Seventy Zenith carburetor venturi hole was only 11/16" diameter versus the D-17 Zenith venturi of 13/16". All the air and fuel that enters into the engines cylinders has to pass thru this size hole. So, the fuel economy is better with a smaller venturi and the engine still makes equal HP.  Fascinating !!

Back in 1977, I sold a customer a nice low hr'd 7030 with a factory air conditioned cab. He traded me a D-21 series2 platform tractor. Both tractors were actually in the 135 HP range. After the first springs use, I asked him one day how he was getting along with the 7030. He said: " it's a really nice tractor, but just doesn't have the power of my D-21".  I knew his tillage practices and asked him what gear he was pulling his 22 ft tandem disc ? He said low 4th high button. And, I said you pulled the same disc with the D-21 in 5th gear, right ??  He said yes.  Well, he used to pull the disc at 6.3 MPH with 50% rear rubber and now he was pulling the same disc at 6.8 MPH with 80% rubber in a nice quiet cab. Yeah. In his mind the D-21 will always be king. Nothing would ever change his mind.

Barometer reading of 29.025 for the D-17 and 29.140 for the One-Seventy.

Gee Doc both low pressure days, do you know the altitude where these tests were in Nebraska or the closest airport? Just curious as I have never considered altitude when reading these h.p results. Thanks

Lincoln KLNK sits 1219 feet above sea level. Correcting for the unusually LOW pressure on these two test days brings the actual air density to over 2000 foot elevation. Thinner air equals less hp, but still the fuel burn on the 170 is quite an improvement! Also I would guess for sure the manufacturer’s advertised their hp corrected for a standard day (59* and 29.92) at sea level, as all engines are on planes and jets.

DrAllis wrote: ...D-17 gas made 52.72 belt HP at 1650 RPM and burned 4.535 GPH of fuel in November of 1957 at 62 degrees F air temp. ... 75 degree F air temp, the new One-Seventy delivered 51.46 PTO HP at 1624 eng RPM's (540 pto speed) while only burning 3.986 GPH fuel. ... By raising the compression from 7.25 to 1 (M code) to 8.0 to 1 (Z code) the fuel consumption was reduced by 1/2 gallon per hour... The One-Seventy Zenith carburetor venturi hole was only 11/16" diameter versus the D-17 Zenith venturi of 13/16"... ...  Fascinating !!

This is good stuff!

Question: Do these engines have the same spec camshaft?

The compression ratio improvement is obvious, but the reduced venturi diameter is not. Perhaps the smaller venturi produces improved atomization of the fuel? I'm just guessing.