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Author Topic:   E-TEC LOAD Function, and other topics

jimh posted 02-25-2013 01:05 PM ET (US)
I recorded the following data about my boat performance with my E-TEC engine:
LOAD SPEED MPG
96   41.7  2.0
58   40.5  2.1
39   31.3  2.5
The LOAD data is a measure of throttle position, from 0 (closed) to 100 (fully open). From the data for speed and fuel economy, I can deduce the fuel flow rate in gallons per hour:
LOAD SPEED MPG  GPH
96   41.7  2.0  20.85
58   40.5  2.1  19.28
39   31.3  2.5  12.52
From the boat speed data I can impute the horsepower being produced. It has been suggested (and a lot of empirical data seems to confirm) that a reasonable approximation of horsepower can be calculated using boat speed if the weight and hull remain constants by the relationship of speed (S) to power (P) as
S1/S2 = (P1/P2)^0.5
This relationship is suggested by George Crouch, a naval architect, for moderate speed planing hull boats. It says that speed increases with the square root of power increase ratios. Using this relationship, the horsepower can be calculated as a function of the boat speed as long as you know the horsepower and speed at one point. For the LOAD = 96 data I assume the engine produced its rated power, which is 225 HP. For the other throttle settings I will calculate the horsepower, using the boat speed and the relationship suggested by Crouch.
LOAD SPEED MPG  GPH    HP
96   41.7  2.0  20.85  225
58   40.5  2.1  19.28  212.2
39   31.3  2.5  12.52  126.7
Now that I have the fuel flow and horsepower, I can compute the brake specific fuel consumption or BSFC. BSFC is measured in lbs per HP hour. I use 6.25 lbs as the density of the gasoline fuel.
LOAD SPEED MPG  GPH    HP     BSFC
96   41.7  2.0  20.85  225    0.579
58   40.5  2.1  19.28  212.2  0.568
39   31.3  2.5  12.52  126.7  0.617
Using the measured value for LOAD and the imputed value for HP, I try to develop a relationship between LOAD and HP. First I test to see if the relationship is linear, that is if one could say
HP = C x 225 x LOAD/96
Using the data at LOAD=39, I find C is 0.563.
Using the data at LOAD=58, I find C is 0.943.
I rearrange the data as follows
LOAD HP Percent of rated HP
100 225 100
96 225 100
58 212 94.3
39 127 56.3
Or more clearly
LOAD Percent-HP
39 56.3
58 95.3
96 100
100 100
If you plot this relationship it looks like a curve that is similar to
Y = X^0.3
or about that shape. I am having a bit of a math-moment, and I can't quite fit my data to a particular curve. I think the relationship of HP to LOAD is generally an exponential relationship with the exponent less than 1.0. If someone sees a good curve fit or a general relationship for HP as a function of LOAD, please comment. Thanks.
jimh posted 02-25-2013 01:24 PM ET (US)
On a slightly different topic, the BSFC calculations tend to show that the engine is not quite as fuel efficient at moderate throttle settings as most people think. Because the horsepower is imputed from other methods, I really don't know if the horsepower values I have used are very accurate. They are probably not accurate enough to make a basis for computing the BSFC to three decimal places, or to one-percent accuracy. Because the imputed horsepower is based on my boat's speed, there could easily be some other influences affecting the boat speed, and this would, in turn, affect the calculated horsepower and the BSFC.
By the way, in comparing the BSFC at full throttle of the E-TEC to two other engines, using their rated horsepower, and fuel flow rates measured by the manufacturers in boat tests, I found that the BSFC values I calculated with my data for the E-TEC were in the ballpark. I found some data for a VERADO 225 and for the new HONDA BF250. I particularly wanted to compare to the new HONDA because it was being reported as having great fuel economy. The BSFC values I calculated were
E-TEC = 0.579-lbs/HP-hour
VERADO = 0.638-lbs/HP-hour
HONDA = 0.57-lbs/HP-hour
For the curious, the data for VERADO and HONDA was taken from reports at
http://www.mercurymarine.com/engines/engine-tests/boat-house-bulletin/ ?ID=898&65411.45238359878
--and--
http://marine.honda.com/pdf/props/ BF250%20Sea%20Chaser%20250%20LX%20Solas%203%20Blade.pdf
The BSFC calculations seem to suggest the VERADO is the least fuel efficient at wide-open, and the HONDA the best, with the E-TEC very close to the HONDA. It did not surprise me that the VERADO liked to burn more fuel, but I have to say I expected the HONDA was going to be even more fuel efficient compared to the E-TEC. The data suggests there is not much difference. Of course, this is at maximum throttle. No one I know spends much time there, probably less than one-percent of their engine operating time.
jimh posted 02-25-2013 02:39 PM ET (US)
ASIDE: I imagine that some readers are probably wondering what the purpose of this thread might be. Let me offer some thoughts on that.
By consolidating all of this data into one article, I manage to collect and organize it. Before writing this, the data was scattered around, and much of it was on four or five sheets of scrap paper that would eventually be discarded. Getting all the data into one organized collection has some value in preserving the data.
I have been thinking about how the LOAD value might be used to approximate horsepower for some time. By actually writing down all this data and describing the various methods, it helps me to think more clearly about the problem.
I really do hope someone reads this and has some suggestions for a curve-fitting for the data. I have been stuck on this for a day or two, and by asking for help I was actually hoping someone might help.
Bringing up a topic like this for discussion often leads to other people contributing ideas that can lead to a solution or new insight. That is a great outcome. I see this happening in a lot of discussions. A participant, not necessarily the originator, says something that sparks a new idea or approach.
jharrell posted 02-25-2013 04:17 PM ET (US)
There won't be a good curve fit for throttle to horsepower as an ICE has varying efficiency throughout it's power-band bad on many variables.
You can always try some standard curve fitting from Wolfram Alpha though:
http://www.wolframalpha.com/input/?i=curve+fitting
Here is your data plotted with quadratic fit:
http://www.wolframalpha.com/input/ ?i=quadratic%20fit%20%7B%7B0%2C%200%7D%2C%20%7B39%2C%20126. 7%7D%2C%20%7B58%2C%20212. 2%7D%2C%20%7B96%2C%20225%7D%2C%20%7B100%2C%20225%7D%7D&lk=2
Here cubic:
http://www.wolframalpha.com/input/ ?i=cubic%20fit%20%7B%7B0%2C%200%7D%2C%20%7B39%2C%20126. 7%7D%2C%20%7B58%2C%20212. 2%7D%2C%20%7B96%2C%20225%7D%2C%20%7B100%2C%20225%7D%7D&lk=2
dgoodhue posted 02-25-2013 05:14 PM ET (US)
Load is a little more complex than just throttle position. I am not sure how E-Tec are fueled. If it map (manifold air pressure) based the load is basically the measure of pressure. If it uses a air flow meter, load is probably calculated (estimated) from throttle position and measured air flow.
jimh posted 02-25-2013 10:06 PM ET (US)
In this discussion, LOAD is throttle position. LOAD is a data value the engine sends to my engine data display. I am interested to see if there is any relationship between the value of LOAD (throttle position) and horsepower.
Thanks for the curve-fitting and the link. I will see if I can find some more data points to refine the relationship.
jimh posted 02-25-2013 10:45 PM ET (US)
I don't know much about the fuel mapping in the E-TEC. I do not think there is any sort of mass air flow sensor in the intake air path. I know the E-TEC engine management module (EMM) receives input from:
--crankshaft position sensor; EMM uses this signal to identify crankshaft position and speed, generate a tachometer signal, and control fuel and ignition timing
--throttle position sensor; receives a voltage signal from the EMM. As the throttle lever is rotated, the EMM receives a return voltage signal through a second wire. This signal increases as the TPS lever is advanced.
--barometric pressure sensor; supplies the EMM with barometric pressure reading to compensate for changes in altitude and air density.
--exhaust pressure sensor; [monitors exhaust pressure during all running conditions to compensate for engine loads.]
--air temperature sensor; monitors the air temperature at the throttle body
--engine temperature sensor; monitors cylinder head temperature.
--knock sensor; detect the presence of knock (pre-ignition or detonation) during the combustion cycle. When knock is detected, the EMM temporarily increases fuel flow and retards ignition timing for the affected cylinder.
dgoodhue posted 02-27-2013 10:06 AM ET (US)
I would guess its using manifold pressure with the barometric pressure. One major issue I see with trying to come up a curve for load to hp is that engine Volumetric Efficiency (VE) curve isn't linear. Your ETEC will most likely have hump in the middle of he RPM range. The Honda wih its V-Tec will have probably have two VE curves due to the variable Valve timing.
jimh posted 03-02-2013 10:08 AM ET (US)
Oops--I had the wrong information (above) on the exhaust pressure sensor function. Fixed it.
Re "manifold pressure"--I don't see a sensor in the E-TEC for manifold pressure.
I will try to collect more information about engine speed, boat speed, and LOAD readings. With the limited data points I have now the fitting of a curve is a bit problematic.
On a corollary topic, I do find having the LOAD data is very useful in getting the engine set up for optimum fuel economy. I typically know that best fuel economy is going to be around LOAD = 40. I usually set the throttle to that position, then I adjust the engine TRIM. Also, I can read the engine TRIM setting to one-percent, that is, one count in one-hundred. I usually know the TRIM setting for optimum fuel economy, too. With these two parameters I can generally set trim and throttle very easily to position where the fuel economy has been optimum. When trim and throttle are set, the boat speed usually falls into a very narrow range, and in a moment the fuel economy usually returns to optimum.
jimh posted 03-04-2013 08:07 AM ET (US)
Re manifold pressure and how it would be used in a two-cycle engine like the E-TEC as part of the fuel control system: there really is not a manifold for the air path into the combustion chamber for a two-cycle engine. The air flows through the crankcase. The pressure in the crankcase varies markedly. When the piston is moving upward in the cylinder there is negative pressure in the crankcase; then the piston is moving downward in the cylinder there is positive pressure in the crankcase. There are one-way check valves ("reed valves") in the air path that allow air to be drawn into the crankcase when there is negative pressure, and do not permit air to escape when there is positive pressure. As far as I can tell from the technical literature of the E-TEC in the service manual, all the sensors are listed and there is no sensor listed for "manifold pressure." At first glance by me, a non-expert, I don't see how manifold pressure would be employed as an input to the fuel control system.

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Author	Topic: E-TEC LOAD Function, and other topics
jimh	posted 02-25-2013 01:05 PM ET (US) I recorded the following data about my boat performance with my E-TEC engine: LOAD SPEED MPG 96 41.7 2.0 58 40.5 2.1 39 31.3 2.5 The LOAD data is a measure of throttle position, from 0 (closed) to 100 (fully open). From the data for speed and fuel economy, I can deduce the fuel flow rate in gallons per hour: LOAD SPEED MPG GPH 96 41.7 2.0 20.85 58 40.5 2.1 19.28 39 31.3 2.5 12.52 From the boat speed data I can impute the horsepower being produced. It has been suggested (and a lot of empirical data seems to confirm) that a reasonable approximation of horsepower can be calculated using boat speed if the weight and hull remain constants by the relationship of speed (S) to power (P) as S1/S2 = (P1/P2)^0.5 This relationship is suggested by George Crouch, a naval architect, for moderate speed planing hull boats. It says that speed increases with the square root of power increase ratios. Using this relationship, the horsepower can be calculated as a function of the boat speed as long as you know the horsepower and speed at one point. For the LOAD = 96 data I assume the engine produced its rated power, which is 225 HP. For the other throttle settings I will calculate the horsepower, using the boat speed and the relationship suggested by Crouch. LOAD SPEED MPG GPH HP 96 41.7 2.0 20.85 225 58 40.5 2.1 19.28 212.2 39 31.3 2.5 12.52 126.7 Now that I have the fuel flow and horsepower, I can compute the brake specific fuel consumption or BSFC. BSFC is measured in lbs per HP hour. I use 6.25 lbs as the density of the gasoline fuel. LOAD SPEED MPG GPH HP BSFC 96 41.7 2.0 20.85 225 0.579 58 40.5 2.1 19.28 212.2 0.568 39 31.3 2.5 12.52 126.7 0.617 Using the measured value for LOAD and the imputed value for HP, I try to develop a relationship between LOAD and HP. First I test to see if the relationship is linear, that is if one could say HP = C x 225 x LOAD/96 Using the data at LOAD=39, I find C is 0.563. Using the data at LOAD=58, I find C is 0.943. I rearrange the data as follows LOAD HP Percent of rated HP 100 225 100 96 225 100 58 212 94.3 39 127 56.3 Or more clearly LOAD Percent-HP 39 56.3 58 95.3 96 100 100 100 If you plot this relationship it looks like a curve that is similar to Y = X^0.3 or about that shape. I am having a bit of a math-moment, and I can't quite fit my data to a particular curve. I think the relationship of HP to LOAD is generally an exponential relationship with the exponent less than 1.0. If someone sees a good curve fit or a general relationship for HP as a function of LOAD, please comment. Thanks.
jimh	posted 02-25-2013 01:24 PM ET (US) On a slightly different topic, the BSFC calculations tend to show that the engine is not quite as fuel efficient at moderate throttle settings as most people think. Because the horsepower is imputed from other methods, I really don't know if the horsepower values I have used are very accurate. They are probably not accurate enough to make a basis for computing the BSFC to three decimal places, or to one-percent accuracy. Because the imputed horsepower is based on my boat's speed, there could easily be some other influences affecting the boat speed, and this would, in turn, affect the calculated horsepower and the BSFC. By the way, in comparing the BSFC at full throttle of the E-TEC to two other engines, using their rated horsepower, and fuel flow rates measured by the manufacturers in boat tests, I found that the BSFC values I calculated with my data for the E-TEC were in the ballpark. I found some data for a VERADO 225 and for the new HONDA BF250. I particularly wanted to compare to the new HONDA because it was being reported as having great fuel economy. The BSFC values I calculated were E-TEC = 0.579-lbs/HP-hour VERADO = 0.638-lbs/HP-hour HONDA = 0.57-lbs/HP-hour For the curious, the data for VERADO and HONDA was taken from reports at http://www.mercurymarine.com/engines/engine-tests/boat-house-bulletin/ ?ID=898&65411.45238359878 --and-- http://marine.honda.com/pdf/props/ BF250%20Sea%20Chaser%20250%20LX%20Solas%203%20Blade.pdf The BSFC calculations seem to suggest the VERADO is the least fuel efficient at wide-open, and the HONDA the best, with the E-TEC very close to the HONDA. It did not surprise me that the VERADO liked to burn more fuel, but I have to say I expected the HONDA was going to be even more fuel efficient compared to the E-TEC. The data suggests there is not much difference. Of course, this is at maximum throttle. No one I know spends much time there, probably less than one-percent of their engine operating time.
jimh	posted 02-25-2013 02:39 PM ET (US) ASIDE: I imagine that some readers are probably wondering what the purpose of this thread might be. Let me offer some thoughts on that. By consolidating all of this data into one article, I manage to collect and organize it. Before writing this, the data was scattered around, and much of it was on four or five sheets of scrap paper that would eventually be discarded. Getting all the data into one organized collection has some value in preserving the data. I have been thinking about how the LOAD value might be used to approximate horsepower for some time. By actually writing down all this data and describing the various methods, it helps me to think more clearly about the problem. I really do hope someone reads this and has some suggestions for a curve-fitting for the data. I have been stuck on this for a day or two, and by asking for help I was actually hoping someone might help. Bringing up a topic like this for discussion often leads to other people contributing ideas that can lead to a solution or new insight. That is a great outcome. I see this happening in a lot of discussions. A participant, not necessarily the originator, says something that sparks a new idea or approach.
jharrell	posted 02-25-2013 04:17 PM ET (US) There won't be a good curve fit for throttle to horsepower as an ICE has varying efficiency throughout it's power-band bad on many variables. You can always try some standard curve fitting from Wolfram Alpha though: http://www.wolframalpha.com/input/?i=curve+fitting Here is your data plotted with quadratic fit: http://www.wolframalpha.com/input/ ?i=quadratic%20fit%20%7B%7B0%2C%200%7D%2C%20%7B39%2C%20126. 7%7D%2C%20%7B58%2C%20212. 2%7D%2C%20%7B96%2C%20225%7D%2C%20%7B100%2C%20225%7D%7D&lk=2 Here cubic: http://www.wolframalpha.com/input/ ?i=cubic%20fit%20%7B%7B0%2C%200%7D%2C%20%7B39%2C%20126. 7%7D%2C%20%7B58%2C%20212. 2%7D%2C%20%7B96%2C%20225%7D%2C%20%7B100%2C%20225%7D%7D&lk=2
dgoodhue	posted 02-25-2013 05:14 PM ET (US) Load is a little more complex than just throttle position. I am not sure how E-Tec are fueled. If it map (manifold air pressure) based the load is basically the measure of pressure. If it uses a air flow meter, load is probably calculated (estimated) from throttle position and measured air flow.
jimh	posted 02-25-2013 10:06 PM ET (US) In this discussion, LOAD is throttle position. LOAD is a data value the engine sends to my engine data display. I am interested to see if there is any relationship between the value of LOAD (throttle position) and horsepower. Thanks for the curve-fitting and the link. I will see if I can find some more data points to refine the relationship.
jimh	posted 02-25-2013 10:45 PM ET (US) I don't know much about the fuel mapping in the E-TEC. I do not think there is any sort of mass air flow sensor in the intake air path. I know the E-TEC engine management module (EMM) receives input from: --crankshaft position sensor; EMM uses this signal to identify crankshaft position and speed, generate a tachometer signal, and control fuel and ignition timing --throttle position sensor; receives a voltage signal from the EMM. As the throttle lever is rotated, the EMM receives a return voltage signal through a second wire. This signal increases as the TPS lever is advanced. --barometric pressure sensor; supplies the EMM with barometric pressure reading to compensate for changes in altitude and air density. --exhaust pressure sensor; [monitors exhaust pressure during all running conditions to compensate for engine loads.] --air temperature sensor; monitors the air temperature at the throttle body --engine temperature sensor; monitors cylinder head temperature. --knock sensor; detect the presence of knock (pre-ignition or detonation) during the combustion cycle. When knock is detected, the EMM temporarily increases fuel flow and retards ignition timing for the affected cylinder.
dgoodhue	posted 02-27-2013 10:06 AM ET (US) I would guess its using manifold pressure with the barometric pressure. One major issue I see with trying to come up a curve for load to hp is that engine Volumetric Efficiency (VE) curve isn't linear. Your ETEC will most likely have hump in the middle of he RPM range. The Honda wih its V-Tec will have probably have two VE curves due to the variable Valve timing.
jimh	posted 03-02-2013 10:08 AM ET (US) Oops--I had the wrong information (above) on the exhaust pressure sensor function. Fixed it. Re "manifold pressure"--I don't see a sensor in the E-TEC for manifold pressure. I will try to collect more information about engine speed, boat speed, and LOAD readings. With the limited data points I have now the fitting of a curve is a bit problematic. On a corollary topic, I do find having the LOAD data is very useful in getting the engine set up for optimum fuel economy. I typically know that best fuel economy is going to be around LOAD = 40. I usually set the throttle to that position, then I adjust the engine TRIM. Also, I can read the engine TRIM setting to one-percent, that is, one count in one-hundred. I usually know the TRIM setting for optimum fuel economy, too. With these two parameters I can generally set trim and throttle very easily to position where the fuel economy has been optimum. When trim and throttle are set, the boat speed usually falls into a very narrow range, and in a moment the fuel economy usually returns to optimum.
jimh	posted 03-04-2013 08:07 AM ET (US) Re manifold pressure and how it would be used in a two-cycle engine like the E-TEC as part of the fuel control system: there really is not a manifold for the air path into the combustion chamber for a two-cycle engine. The air flows through the crankcase. The pressure in the crankcase varies markedly. When the piston is moving upward in the cylinder there is negative pressure in the crankcase; then the piston is moving downward in the cylinder there is positive pressure in the crankcase. There are one-way check valves ("reed valves") in the air path that allow air to be drawn into the crankcase when there is negative pressure, and do not permit air to escape when there is positive pressure. As far as I can tell from the technical literature of the E-TEC in the service manual, all the sensors are listed and there is no sensor listed for "manifold pressure." At first glance by me, a non-expert, I don't see how manifold pressure would be employed as an input to the fuel control system.