6MT Uphill Fuel Consumption Test; BSFC
Thread Starter
|
Member
Joined: Sep 2020
Posts: 39
From: Anchorage
6MT Uphill Fuel Consumption Test; BSFC
Owning a 6MT Fit, I was curious what the most efficient zone of the rpm range was the most efficient when operating at a significant load. (driving uphill or accelerating quickly) So I did a test using my scangauge. (which is calibrated and verified accurate after each fillup)
I conducted the test on a one mile stretch of a 10% grade. I drove up the hill with the cruise set to 40 mph a total of 4 times, twice in 4th gear at 2400 RPM, with and without defrost on 2, and twice in 3rd gear at 3150 RPM with and without defrost on 2. Even with the cruise set to 40, the car only tried to maintain 39 mph up the hill. Ambient temp was 26F/-3C. No wind, precipitation, or traffic. Headlights were turned on for all runs. I didn't have the AC button pushed, but it was probably on along with the defrost anyway. Engine fully warmed prior to test start.
I reset my current trip on the scangauge at a certain driveway, once the hill started, then switched to gauge to look at AVG and LOD. (AVG is average mpg for the current trip, LOD is the percentage of available engine power utilized at the current RPM). Then at a certain street where the hill nearly ended, I would cancel the cruise and note the AVG at that point in time. Then I'd turn around, go back down the hill in 3rd gear at 50 mph (off throttle), then turn around beyond the base the hill to repeat. I used the resume button to be as scientific as possible.
Test 1: 4th gear, 2400 rpm, 39 MPH, defrost on 2: 23.7 MPG (LOD: 69-75)
Test 2: 3rd gear, 3150 rpm, 39 MPH, defrost on 2: 21.1 MPG (LOD: 47-57)
Test 3: 4th gear, 2400 rpm, 39 MPH, no defrost: 24.4 MPG (LOD: 59-66)
Test 4: 3rd gear, 3150 rpm, 39 MPH, no defrost: 21.5 MPG (LOD: 43-52)
Judging by this test I would say it's better to drive in the mid 2000s of the rev range at 3/4 throttle than to drive in the lower to mid 3000s at 1/2 throttle.
I wouldn't feel comfortable taking the hill in 5th because it would be very near full throttle at only 2050 or so rpm and that's probably not good for the engine, 4th should be perfectly fine though.
If I can find a mile long stretch of road that sustains a 4-7% grade, I'd test out 1900 rpm vs 2500 rpm to see which was better. I'd also like to do speed tests to see which speed is best, from 25 up to 65. I believe that 25 mph in 6th gear gives the best MPG (only 1200 rpm and LOD stays under 30, so nobody freak out), because the instant readout on the scangauge tends to read 55-65 on apparent level ground while traveling 25 mph in 6th.
I conducted the test on a one mile stretch of a 10% grade. I drove up the hill with the cruise set to 40 mph a total of 4 times, twice in 4th gear at 2400 RPM, with and without defrost on 2, and twice in 3rd gear at 3150 RPM with and without defrost on 2. Even with the cruise set to 40, the car only tried to maintain 39 mph up the hill. Ambient temp was 26F/-3C. No wind, precipitation, or traffic. Headlights were turned on for all runs. I didn't have the AC button pushed, but it was probably on along with the defrost anyway. Engine fully warmed prior to test start.
I reset my current trip on the scangauge at a certain driveway, once the hill started, then switched to gauge to look at AVG and LOD. (AVG is average mpg for the current trip, LOD is the percentage of available engine power utilized at the current RPM). Then at a certain street where the hill nearly ended, I would cancel the cruise and note the AVG at that point in time. Then I'd turn around, go back down the hill in 3rd gear at 50 mph (off throttle), then turn around beyond the base the hill to repeat. I used the resume button to be as scientific as possible.
Test 1: 4th gear, 2400 rpm, 39 MPH, defrost on 2: 23.7 MPG (LOD: 69-75)
Test 2: 3rd gear, 3150 rpm, 39 MPH, defrost on 2: 21.1 MPG (LOD: 47-57)
Test 3: 4th gear, 2400 rpm, 39 MPH, no defrost: 24.4 MPG (LOD: 59-66)
Test 4: 3rd gear, 3150 rpm, 39 MPH, no defrost: 21.5 MPG (LOD: 43-52)
Judging by this test I would say it's better to drive in the mid 2000s of the rev range at 3/4 throttle than to drive in the lower to mid 3000s at 1/2 throttle.
I wouldn't feel comfortable taking the hill in 5th because it would be very near full throttle at only 2050 or so rpm and that's probably not good for the engine, 4th should be perfectly fine though.
If I can find a mile long stretch of road that sustains a 4-7% grade, I'd test out 1900 rpm vs 2500 rpm to see which was better. I'd also like to do speed tests to see which speed is best, from 25 up to 65. I believe that 25 mph in 6th gear gives the best MPG (only 1200 rpm and LOD stays under 30, so nobody freak out), because the instant readout on the scangauge tends to read 55-65 on apparent level ground while traveling 25 mph in 6th.
Last edited by Chugiak76; Mar 27, 2021 at 07:41 AM.
Member
Joined: Dec 2020
Posts: 141
From: Las Vegas, NV
"When To Shift Gears For The Best Fuel Economy" - Engineering Explained
Basically, an engine is the most efficient (work done per fuel consumed) when load is high and movement is low (low RPM).
Obviously, up to the point where it isn't overloaded. Personally, I let it rev a bit higher if climbing a hill, even if it costs a bit more in gas.
Basically, an engine is the most efficient (work done per fuel consumed) when load is high and movement is low (low RPM).
Obviously, up to the point where it isn't overloaded. Personally, I let it rev a bit higher if climbing a hill, even if it costs a bit more in gas.
Thread
Thread Starter
Forum
Replies
Last Post