Like mentioned, The BFSC is for WOT only.
It has nothing to do with varying part throttle conditions.
It has nothing to do with varying part throttle conditions.
Brake Specific Fuel Consumption Question
- Thread starter Hokiefyd
- Start date
- Status
In a three dimensional BSFC map it is plotted for different torque levels, which require different throttle openings.
- Joined
- Sep 28, 2002
- Messages
- 39,798
Originally Posted By: oilyriser
In a three dimensional BSFC map it is plotted for different torque levels, which require different throttle openings.
Not challenging you, but out of my ignorance, why wouldn't (or couldn't) it just plot different states of WOT and the varied torque levels that the engine produces at that point?? Just trying to index your statement here.
In a three dimensional BSFC map it is plotted for different torque levels, which require different throttle openings.
Not challenging you, but out of my ignorance, why wouldn't (or couldn't) it just plot different states of WOT and the varied torque levels that the engine produces at that point?? Just trying to index your statement here.
I have nothing meaningful to contribute to this other than my TL starts getting worse mileage below 45mph in 5th which is around 1,500rpm. I always figured a vtec motor on the small cam would get better and better mileage as speeds fell off but that isn't so.
Originally Posted By: Gary Allan
Originally Posted By: oilyriser
In a three dimensional BSFC map it is plotted for different torque levels, which require different throttle openings.
Not challenging you, but out of my ignorance, why wouldn't (or couldn't) it just plot different states of WOT and the varied torque levels that the engine produces at that point?? Just trying to index your statement here.
That would be a regular torque curve. With throttle partly closed, you get another torque curve below the first one, with a different shape. If you run the engine from zero to redline, at different throttle openings, and measure the amount of torque and fuel flow rate at each point, you can multiply torque by rpm to get power, and divide that into the fuel flow rate, and get the specific fuel consumption for each point.
Originally Posted By: oilyriser
In a three dimensional BSFC map it is plotted for different torque levels, which require different throttle openings.
Not challenging you, but out of my ignorance, why wouldn't (or couldn't) it just plot different states of WOT and the varied torque levels that the engine produces at that point?? Just trying to index your statement here.
That would be a regular torque curve. With throttle partly closed, you get another torque curve below the first one, with a different shape. If you run the engine from zero to redline, at different throttle openings, and measure the amount of torque and fuel flow rate at each point, you can multiply torque by rpm to get power, and divide that into the fuel flow rate, and get the specific fuel consumption for each point.
Originally Posted By: BuickGN
I have nothing meaningful to contribute to this other than my TL starts getting worse mileage below 45mph in 5th which is around 1,500rpm. I always figured a vtec motor on the small cam would get better and better mileage as speeds fell off but that isn't so.
That's not to far off of normal. Peak economy speed is usually about 35 to 45 mph for a wide variety of cars.
It's a bit faster than I would have guessed for a TL, but then if they kind of stuff were guessable to a high level of accuracy, they would lay off a bunch of test engineers.
I have nothing meaningful to contribute to this other than my TL starts getting worse mileage below 45mph in 5th which is around 1,500rpm. I always figured a vtec motor on the small cam would get better and better mileage as speeds fell off but that isn't so.
That's not to far off of normal. Peak economy speed is usually about 35 to 45 mph for a wide variety of cars.
It's a bit faster than I would have guessed for a TL, but then if they kind of stuff were guessable to a high level of accuracy, they would lay off a bunch of test engineers.
On the SL2 motor, you can trace the WOT line from 1200 RPM all the way to 4500 RPM, and it runs along the 275 g/kWhr BSFC line. So, keeping the engine in this area gets you pretty close to the minimum fuel consumption regime where it drops below 250.
Best BSFC occurs at 2500 rpm, which corresponds to 72 mph in 5th gear. Unfortunately, the motor puts out 43.6 horsepower at WOT at this point. If you throttle it back to 15 hp, you muddle the BSFC up to 325 g/kWhr, which is 30% higher than the best it can do. However, if you pulse and glide around 70-75 mph, using near WOT, you could keep the engine running in the lower BSFC regions, and get more mpg out of the car.
Best BSFC occurs at 2500 rpm, which corresponds to 72 mph in 5th gear. Unfortunately, the motor puts out 43.6 horsepower at WOT at this point. If you throttle it back to 15 hp, you muddle the BSFC up to 325 g/kWhr, which is 30% higher than the best it can do. However, if you pulse and glide around 70-75 mph, using near WOT, you could keep the engine running in the lower BSFC regions, and get more mpg out of the car.
- Status
