SDS Engine data

[BowansReward]

Hi, I've ran a speed test on my DF115, trying to work out the optimum cruising speed. Looking at plaining speed over fuel used. The results I'm getting back do not add up against the actual performance that I whiteness while cruising.

Basically. I run the engine at a given rpm. Record the fuel used & note down my speed. Fuel used (over a hour period) divided by speed = Fuel used per Knot (distance). Then repeat the exercise at a higher rpm until the optimum run speed is determined.

The SDS manual says that a fuel injection (time period of 0.2 seconds) unit is measured at 0.000001 litres.
Using 1 second x minute x hour x No. cylinder x Fuel used
5 x 60 x 60 x 4 x 0.000001 = 0.072 litres per hour for each unit of injected fuel

Using the Speed (kts) divided by ( 0.072 litres x Fuel inject units ) this SHOULD give the fuel used per knot (distance)

The figures that I come up with are well below what I know I use for an hour run at a given speed!

Please could anyone tell me where I'm going wrong in my calculations?

Am I missing another variable in fuel consumption?

Thank you Dave

[Murray]

How accurate is your measured distance and speed? You heading with or against a current? Headwind or tailwind? With or against the tide? How do you know all your injectors are supplying .000001 L/burst? I wonder how Suzuki came up with 0.000001L, real world testing or a calculated number based on orfice size and fuel pressure I’d be interested to know the percentage difference between your actual vs your calculated theoretical.

[BowansReward]

I'm doing my test runs in an enclosed harbour within a breakwater. Testing on a calm day with minimal wind. Running for a mile & turning round and a second run in the opposite direction (through my own wake). There is some tidal movement, but the 2 directions should balance this out. This gives a good aggregate speed at the tested rpm. No indication on SDS readout of problems with the injectors, but my maths is too good a performance! Using around 25% of the fuel I know I use at these speed.

How would I measure orfice size & fuel pressure?

I've taken the Suzuki value from their diagnostic manual, so have to trust that value! I have no way to question it?

The only other way that I can see to measure performance is to buy & insert a fuel flow meter on the fuel in pipe?

[Moonlighter]

I have a 2010 DF115 on my 5.5m Aluminium cuddy cab. Boat/motor/trailer all up weighs about 1250kg or so in ready to fish trim.

Because I have my engine hooked up to the NMEA2000 network, I know where the sweet spot is for economy, and its from 4100-4500rpm. For about 2.4 km/litre. Economy doesn’t actually change much up to 5000rpm, but past that it decreases steadily.

For the last 2 years I have also had a Simrad GO7 xse on my network and it has a TripIntel function that records all trips, distance travelled, fuel used and fuel economy. It also keeps long term statistics and shows that average fuel economy over that time is almost exactly 2km/litre.

If you really want to get your economy accurately measured you should connect your engine up to the NMEA2000 network then you wont need to do any of this manual calculation. Read the sticky thread in the top section on this forum for details on this.

You will be amazed to see how much fuel economy varies even at steady throttle settings due to wind, waves, wakes, turns, temperature and other factors. There are so many of these variables that your manual calculations that dont take them into account will never be accurate.

[BowansReward]

Hi Moonlighter,

I'm already onto what you've suggested and waiting for a SMIS cable to arrive in the post. Over the last weeks I extended my SDS port from the engine through to a switchable port next to the helm. In one switch setting I can connect my laptop to run diagnostics in the other it will connect the SDS to my NMEA2000.

That is why I was able to run the logger on my laptop & measure my fuel usage! I'm still annoyed that the results I've got don't add up. Even with the inaccuracy I can see the fuel consumption fall off as I hit 4000rpm when the boat starts to plain. Fuel consumption at 5000rpm (per knot) is lower than harbour speed of 2000rpm.

Very interested to see all the extra data the SMIS will bring to my chartplotter.

[Moonlighter]

What year is your engine? You need to match the engine year with the correct interface cable software or it doesnt work properly.

again, suggest you read the sticky thread at the top of the forum it gives lots of details and saves us answering questions here that are already answered there.

And, if you dont set it up and configure it properly you will have problems. You need a Suzuki C-10 gauge or Lowrance/Simrad display on your N2K network to do the setup/config, it cant be done with SDS software.

All this is explained in the sticky thread.

[BowansReward]

My DF115 is 2013, I've matched the cable I've ordered to this.

I'm not sure what needs setting up?

my nmea2k device is a Garmin 922sx chartplotter

[Murray]

I'm doing my test runs in an enclosed harbour within a breakwater. Testing on a calm day with minimal wind. Running for a mile & turning round and a second run in the opposite direction (through my own wake). There is some tidal movement, but the 2 directions should balance this out. This gives a good aggregate speed at the tested rpm. No indication on SDS readout of problems with the injectors, but my maths is too good a performance! Using around 25% of the fuel I know I use at these speed.

How would I measure orfice size & fuel pressure?

I've taken the Suzuki value from their diagnostic manual, so have to trust that value! I have no way to question it?

The only other way that I can see to measure performance is to buy & insert a fuel flow meter on the fuel in pipe?

I was just pointing out some of the variables that your calculations couldn’t account for. Please post your real world results once you have your Garmin setup, I’d be interested in seeing the difference between the theoretical vs real world. To me it’s like the stickers on new vehicles, the manufacturers post an estimated fuel efficiency but rarely you achieve those results.

[BowansReward]

Hi Murray,

Question on that: surely the data that the ECU passes to my chartplotter is the same data that I was collecting on my laptop?

[Murray]

One would think so as far as engine data is concerned. The big variables would be GPS data that your laptop can’t integrate into the fuel consumption calculation. I don’t have any fancy electronics in my boat nor do I have a need for it. All my boating is in a small freshwater lake.

[Moonlighter]

My DF115 is 2013, I've matched the cable I've ordered to this.

I'm not sure what needs setting up?

my nmea2k device is a Garmin 922sx chartplotter

Read the sticky thread and you will find out!!

[2014DF25ARS]

How do you know how many "fuel inject units" you are using at a given speed? Does the SDS s/w show you this number?

I have a Suzuki LMF-400 display connected my engine, along with a water speed wheel. I believe you can get speed from either a wheel or a connected GPS receiver. With the speed input, the LMF-400 displays real-time MPG, which is quite interesting to watch. My boat's top speed with a 25 HP motor is approx. 29 MPH. When I'm cruising at 23-24 MPH, around 2/3 throttle, I'm getting 15-16 MPH. When I speed up to WOT, my fuel economy drops to about 11 MPG. My numbers do line up with the "****en rule" I've heard: that an outboard motor will burn approximately HP/10 gallons of fuel at WOT. So my 25 HP motor burns about 2.5 gals/hour, and I would expect your 115 HP motor to burn about 11.5 gals/hour at WOT.

[BowansReward]

How do you know how many "fuel inject units" you are using at a given speed? Does the SDS s/w show you this number?

I have a Suzuki LMF-400 display connected my engine, along with a water speed wheel. I believe you can get speed from either a wheel or a connected GPS receiver. With the speed input, the LMF-400 displays real-time MPG, which is quite interesting to watch. My boat's top speed with a 25 HP motor is approx. 29 MPH. When I'm cruising at 23-24 MPH, around 2/3 throttle, I'm getting 15-16 MPH. When I speed up to WOT, my fuel economy drops to about 11 MPG. My numbers do line up with the "****en rule" I've heard: that an outboard motor will burn approximately HP/10 gallons of fuel at WOT. So my 25 HP motor burns about 2.5 gals/hour, and I would expect your 115 HP motor to burn about 11.5 gals/hour at WOT.

This is the kind of information I am looking for. I am not a mechanic? So the injectors are used as required? I can't see a parameter that would track this. List below!

Again though. If not all of the injectors are used the calculation figure drops & the result is even more inaccurate!!

I'm not sure what WOT stands for?

ENGINE SPEED ***
IGNITION TIMING
MANIFOLD ABSOLUTE PRESSURE
MANIFOLD ABSOLUTE PRESSURE
MANIFOLD ABSOLUTE PRESSURE
BAROMETRIC PRESSURE
BAROMETRIC PRESSURE
BAROMETRIC PRESSURE
CYLINDER TEMPERATURE
CYLINDER TEMPERATURE
INTAKE AIR TEMPERATURE
INTAKE AIR TEMPERATURE
BATTERY VOLTAGE
FUEL INJ. PULSE WIDTH
INJECTED FUEL AMOUNT ***
FUEL PUMP DUTY
IAC VALVE DUTY
NO. OF MAP SENSOR FAILURE
NO. OF CKP SENSOR FAILURE
NO. OF IAC VALVE FAILURE
NO. OF CMP SENSOR FAILURE
NO. OF CTP SWITCH FAILURE
NO. OF CYL. TEMP. SNSR FAILURE
NO. OF IAT SENSOR FAILURE
NO. OF EX. TEMP. SNSR FAILURE
NO. OF FUEL INJECTOR FAILURE
NO. OF OVER-REVOLUTION
NO. OF LOW BATTERY VOLTAGE
NO. OF LOW OIL PRESSURE
NO. OF OVERHEAT(GRADIENT)
NO. OF OVERHEAT(TEMP.)
CAUTION SYSTEM NAME (1)
ENGINE SPEED (1)
MANIFOLD ABSOLUTE PRESSURE (1)
MANIFOLD ABSOLUTE PRESSURE (1)
MANIFOLD ABSOLUTE PRESSURE (1)
CYLINDER TEMPERATURE (1)
CYLINDER TEMPERATURE (1)
INTAKE AIR TEMPERATURE (1)
INTAKE AIR TEMPERATURE (1)
EX-MANI TEMPERATURE (1)
EX-MANI TEMPERATURE (1)
FAILURE TIME (1)
ELAPSE OF TIME (1)
TOTAL OPERATION TIME (HRS.)
TOTAL OPERATION TIME (MIN.)
0-1000 RPM
1000-2000 RPM
2000-3000 RPM
3000-4000 RPM
4000-5000 RPM
5000-6000 RPM
ABOVE 6000 RPM
ELAPSE TIME FROM REMINDER CANCEL
NO. OF OIL CHANGE REMINDER
COMPENSATION FACTOR (ZONE 1)
COMPENSATION FACTOR (ZONE 2)
COMPENSATION FACTOR (ZONE 3)
TIME OF LAST O2 FEEDBACK
EMERGENCY STOP SWITCH
CTP SWITCH
NEUTRAL SWITCH

[BowansReward]

Just found this in the SDS manual:

Fuel Injector pulse width / (uS)
Injection time duration for each cylinder per 1 time

SDS readout on this parameter (while idling):
FUEL INJ. PULSE WIDTH 3680 µs

3680us = 0.003680 sec per cylinder per 0.2 sec
or 0.01472 per 0.2 sec for the engine

Going back to my previous calculation I think I need to record this parameter and adjust my formula to:

Using 1 second x minute x hour x No. cylinder x Fuel used x Pulse Width(observed in micro-seconds) = flow rate

5 x 60 x 60 x 4 x 0.000001 x (pulse X 1000000 x 4) = Flow rate

Using the Speed (kts) divided by (Flow rate X Fuel Inject Units) this SHOULD give the fuel used per knot (distance)

I will have to repeat my speed trial logging:
RPM
FUEL INJECT PULSE WIDTH
FUEL INJECT UNITS

[Moonlighter]

WOT = wide open throttle.

I understand that this may simply be an academic exercise for you, and thats all well and good.

But once you get the engine hooked up to the network, it is going to give you the answer anyway.

Depending on the display being used, the engine fuel flow data is used by the display, in combination with speed/distance data it gets from either its internal GPS receiver or another receiver on the network to calculate mpg in real time. Some displays also take that further to combine it with fuel capacity data to calculate distance to empty etc.

So bear in mind that the two packages - the SDS software on one hand, and the Suzuki engine interface (SMIS) software on the other, are designed for different purposes and therefore read some common and some different engine data items from the ecu.

SDS therefore does some (lots of) things that the SMIS cant, and vice versa. SDS cannot, for example, configure the Interface to set network engine instances nor can it be used to set up vessel parameters. SMIS is required for those tasks. SMIS is limited in its diagnostic capabilities to showing fault codes.

So you are kind of trying to get something from SDS that its not really designed to give.

Regarding fuel data, SMIS also allows for user calibration to fine tune the accuracy of the system calculations.