garciapiano
Veteran Member
Hi there,
I'm of the opinion that the best fuel economy is to be had at the tallest gear possible at any given speed, to not lug the engine, thus maximizing mechanical work done during the combustion cycle. This effect is well-documented for naturally aspirated gasoline engines, but I'm not entirely sure if it applies to the TDI. Intuitively, high-load, low RPM is hard on the engine's internals, and there are some questions as to whether it is smart to do in a turbocharged engine.
Normally, when driving in low-load situations (such as on a flat city street) I make it a point to get into 4th or 5th if possible.... Typically I will shift in tandem with every 10 MPH gain. E.g., I'm going into 2nd at 10-15mph, 3rd around 25-30 mph and 4th around 35-40 mph and 5th around 45-50 mph. This pattern seems to line up nicely with the gear ratios of the trans. I accelerate smoothly and shift around 2300 RPM, effectively keeping me around 1800 RPM on average. I make it a point to rev out the engine hard every so often so it's not like I'm babying it.
Recently I've been experimenting with driving around in taller gears/lower RPMs just for the sake of fuel economy. I only do this with the oil at full operating temp to prevent any wear that would occur under the higher load. E.g. going into 4th at 30 MPH, and 5th at 40 MPH. I think the synchros are a little less happy to shift at these RPMS, but effectively I'm trying to model an eco-tuned automatic.
I have no way of metering actual live fuel consumption so I'm curious if anyone has any anecdotal or hard data they can provide regarding this. I have looked at the BSFC chart but really, once I'm at highway speeds I'm generally driving around where the BSFC peaks for the 1.9 TDI engine, in fuel/mph around 1900 RPM. In general, I tend not to exceed 70 MPH in the TDI, and drive around 65 MPH most of the time on the highway.
I'm of the opinion that the best fuel economy is to be had at the tallest gear possible at any given speed, to not lug the engine, thus maximizing mechanical work done during the combustion cycle. This effect is well-documented for naturally aspirated gasoline engines, but I'm not entirely sure if it applies to the TDI. Intuitively, high-load, low RPM is hard on the engine's internals, and there are some questions as to whether it is smart to do in a turbocharged engine.
Normally, when driving in low-load situations (such as on a flat city street) I make it a point to get into 4th or 5th if possible.... Typically I will shift in tandem with every 10 MPH gain. E.g., I'm going into 2nd at 10-15mph, 3rd around 25-30 mph and 4th around 35-40 mph and 5th around 45-50 mph. This pattern seems to line up nicely with the gear ratios of the trans. I accelerate smoothly and shift around 2300 RPM, effectively keeping me around 1800 RPM on average. I make it a point to rev out the engine hard every so often so it's not like I'm babying it.
Recently I've been experimenting with driving around in taller gears/lower RPMs just for the sake of fuel economy. I only do this with the oil at full operating temp to prevent any wear that would occur under the higher load. E.g. going into 4th at 30 MPH, and 5th at 40 MPH. I think the synchros are a little less happy to shift at these RPMS, but effectively I'm trying to model an eco-tuned automatic.
I have no way of metering actual live fuel consumption so I'm curious if anyone has any anecdotal or hard data they can provide regarding this. I have looked at the BSFC chart but really, once I'm at highway speeds I'm generally driving around where the BSFC peaks for the 1.9 TDI engine, in fuel/mph around 1900 RPM. In general, I tend not to exceed 70 MPH in the TDI, and drive around 65 MPH most of the time on the highway.