My MIL is turning 90 next month and I thinking about which car to take to make the 1000 mile trip, if and when they lift the stay at home orders. I'm tempted to take the Fiesta just for grins to see if I can make the trip on $30 of gas. Gas is currently $1.35 at Costco here. It's actually got pretty comfortable seats and a good radio, offset by a lot of road noise. But I was wondering whether its a good idea to run this little 3 banger ecoboost at 75 mph for hours on end?
I found a website that you can calculate hp requirements for a given speed and vehicle parameters. I input a drag coefficient of .38, 23 sq ft of frontal area, 2900 lbs loaded. It came back with the following HP numbers
50 mph = 11.8 hp requirement
75 mph = 31.7 hp
120 mph = 115 hp
Given the engine makes 126 hp before deducting transmission losses and it probably can't do 120, this is theoretical calculation is still probably ball park..
Then I calculated specific fuel consumption using the above info and knowing that the car gets 70 and 39 mpg at 50 and 75 mph respectively (I kid you not).
I got 0.0605 gallons per hp-hr at 0.0600 gallons per hp-hr at 75 mph. Perhaps plausible.
So 32 hp equals 25% of maximum output. Doesn't seem like its stressing the engine too much, but it does seem like 75 mph is the tipping point where the engine starts to sound like its working hard. And this is flat land hp, hills (and wind) will require more hp.
How much is too much in pushing an engine?
I found a website that you can calculate hp requirements for a given speed and vehicle parameters. I input a drag coefficient of .38, 23 sq ft of frontal area, 2900 lbs loaded. It came back with the following HP numbers
50 mph = 11.8 hp requirement
75 mph = 31.7 hp
120 mph = 115 hp
Given the engine makes 126 hp before deducting transmission losses and it probably can't do 120, this is theoretical calculation is still probably ball park..
Then I calculated specific fuel consumption using the above info and knowing that the car gets 70 and 39 mpg at 50 and 75 mph respectively (I kid you not).
I got 0.0605 gallons per hp-hr at 0.0600 gallons per hp-hr at 75 mph. Perhaps plausible.
So 32 hp equals 25% of maximum output. Doesn't seem like its stressing the engine too much, but it does seem like 75 mph is the tipping point where the engine starts to sound like its working hard. And this is flat land hp, hills (and wind) will require more hp.
How much is too much in pushing an engine?