Anyone have BSFC data or estimates for stock L24 @ 5600rpm

[240260280z]

Looking for BSFC to improve a calculation's accuracy. Any data or estimates is most welcome.

Right now I am using 0.4 at 5600 but I feel it may be too low.

[ozconnection]

Willing to share your investigation? Might turn out some interesting perceptions.

[240260280z]

I will do when ready. It is only 1/2 done. Should be a cool tool once finished.

[steve91tt]

I don't know much about BSFC (Brake Specific Fuel Consumption?). I did a quick google search but did not fully understand what I was reading. Is this the fuel consumption per horsepower at WOT?

[240260280z]

BSFC is rate of fuel consumption divided by power made.

It varies with rpm.

The theory states it is supposed to be peak at maximum torque.

For a 4 cycle motor, it is supposed to be ~ 0.37 to 0.45 pounds of "standardized" gasoline per hour per horse power (according to wiki).

My problem is that for my HP calculation for an L24 @ 5600, I need to set Ve at 1 (complete filling and burning of exactly 2.4 litres of fuel) and a BSFC of 0.40.

0.40 seems to fit between the 0.37 to 0.45 but I have checked other peoples calculations on line and they typically use 0.50 to 0.55 for BSFC. As well if the L24 is 0.4 at 5,600rpm then it should be even better at max torque (4,400rpm).... which "feels" a little optimistic to me at this point in my model development.

I am OK with the 0.40 as per the Wiki range, but I need a sanity check

Edited September 11, 2011 by Blue

[LeonV]

BSFC is rate of fuel consumption divided by power made.

It varies with rpm.

The theory states it is supposed to be peak at maximum torque.

For a 4 cycle motor, it is supposed to be ~ 0.37 to 0.45 pounds of "standardized" gasoline per hour per horse power (according to wiki).

My problem is that for my HP calculation for an L24 @ 5600, I need to set Ve at 1 (complete filling and burning of exactly 2.4 litres of fuel) and a BSFC of 0.40.

0.40 seems to fit between the 0.37 to 0.45 but I have checked other peoples calculations on line and they typically use 0.50 to 0.55 for BSFC. As well if the L24 is 0.4 at 5,600rpm then it should be even better at max torque (4,400rpm).... which "feels" a little optimistic to me at this point in my model development.

I am OK with the 0.40 as per the Wiki range, but I need a sanity check

BSFC would be at its minimum at max torque, not maximum. For those unfamiliar, think of it as the inverse of engine efficiency (proportional to torque), which is maximum at peak torque. As far as a good number, let me get back to you tomorrow, Blue, and I'll try to come up with something.

[240260280z]

Thanks! I look forward to your data.

Yes I mis-wrote max/min..... and in re-reading I also wrote "burning of exactly 2.4 litres of fuel" you know what I meant.

I wish the edit time limit was extended to 1 month as 1 hr is not enough for my mistakes to be corrected.

Edited September 11, 2011 by Blue

[Phred]

I have some numbers from a SCCA legal ITS 240Z. BSFC is not a hard fast number, and will/can vary depending on the state of tune. Other variables which can effect BSFC are the mechanical efficiency, or internal frictional loss of rings, bearings, etc. Also note, max torque@RPM varies with cam timing and length of intake tract, and size of header tubes/length.

These are an average of two ITS 240 engines:

4750 RPM - .59 BSFC ( 169 lb/ft. @ 153 hp )

5000 RPM - .55 BSFC ( 166 lb/ft. @ 158 hp )

5250 RPM - .56 BSFC ( 163 lb/ft. @ 163 hp )

5500 RPM - .56 BSFC ( 157 lb/ft. @ 164 hp )

5750 RPM - .55 BSFC ( 151 lb/ft. @ 165 hp )

Have fun!

Phred

[240260280z]

Thanks Phred,

It is great to get data!

Unfortunately I must have an error in my calculator as I need a Ve of 1.5 to get 164hp at 5600rpm... I'll double check. I am amusing

RPM 5600

Vol 2.4l

Fuel Air Ratio 12.6:1

BSFC 0.56

Ve tweaked to match HP to real world

Philip

[240260280z]

Checked and fixed. I had a typo in a metric conversion.

At 5600 for 164hp I estimate a Ve of 1.08 (8% over filling of chamber) which seems reasonable.

BIG THANKS!

[LeonV]

Excellent data, Phred!

Philip, are you keeping in mind the differences between brake and wheel horsepower? Stupid question, just making sure.

[240260280z]

Yup... I am just modelling the motor for now... it will eventually expand to model carb piston height and needle taper at RPM along with real fuel flow measurements.

One of the areas I want to explore is when should the carb piston hit the roof and go from CV to non-CV mode. This will in turn lead to spring exploration and piston mass exploration.