They can be, but manufacturers choose to up the HP instead, thus it nullifies any gas saving DI can bring.
Increasing horse power and torque, especially low-end torque, will net fuel savings. The problem is the person behind the wheel who has a lead foot and wants to take advantage of the additional power instead of the fuel savings.They can be, but manufacturers choose to up the HP instead, thus it nullifies any gas saving DI can bring.
Increasing horse power and torque, especially low-end torque, will net fuel savings. The problem is the person behind the wheel who has a lead foot and wants to take advantage of the additional power instead of the fuel savings.
Horsepower is torque times RPM. Actually, the formula looks like this:Since manufacturers only provide peak HP, we can only speculate if there are any gains elsewhere on the HP/TQ curve.
Please don’t try to teach me about torque and power.Horsepower is torque times RPM. Actually, the formula looks like this:
View attachment 208216
For the Honda Odyssey:
The GDI version makes 262 lb-ft. of torque and the MPI version 250 lb-ft of torque. And that's the peak torque at around 4K RPM. That won't make a dent in fuel economy.
However, for lighter vehicles like sedans and compacts, it does. Take something like a 2008 Sonata with a 2.4L MPI vs. 2011 Sonata with a 2.4L GDI. The first will get 30~32 Highway MPG, the second will get 36~38. Go up to the revised 2.5 GDI/MPI, and real world Highway MPG is now over 40. It's not earth shattering, but the improvement is there, at the expense of long term reliability.
If I recall correctly all things being equal, power increases about 3% for every point increase in compression. So a 10:1 engine that produces 200hp will make about 206hp at 12:1. I believe efficiency increases are on the same order.DI engines can also run a higher compression ratio on the same octane fuel, contributing to better fuel economy.
If I recall correctly all things being equal, power increases about 3% for every point increase in compression.
So a 10:1 engine that produces 200hp will make about 206hp at 12:1. I believe efficiency increases are on the same order.
Mitsubishi was the first production car with DI in 96/97. Many companies used the Mitsubishi GDI system under license.
More like a brain fart. Thanks for correcting.Efficiency increases, both power and decrease in fuel consumption. This is the beauty of efficiency.
A typo? From 10:1 to 11:1 will make from 200 HP to ~206 HP (3 %) and from 10:1 to 12:1 would
result an improvement from 200 HP to roughly 212 HP. Two points make 2 x 3 % = 6 % (12 HP).
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Mitsubishi was the first production car with DI in 96/97. Many companies used the Mitsubishi GDI system under license.