-----Original Message-----
From:David
I became concerned about the fuel transducer specs taken from Navman's
website:
Flow Rates Max 400l/h and Min of 25l/h
25 l/h is about 5.5 gph which equates to about 100 horsepower. In a
diesel you need two transducers: one for the feed to the injector and
another for the return. The difference is your fuel consumption. I
emailed Navman to ask them if their system would work with less than 100
horsepower engines and they emailed back that the diesel system has been
withdrawn from the market.
REPLY
The problem is transducer accuracy. Most transducers will have a fixed
amount of slippage not to mention inertia. That tiny amount of error
becomes a bigger percentage as the total flow is reduced. In addition to
that turbine or paddle wheel style transducers have a certain amount of
internal friction. The only way to overcome that is to spend a lot of
money on extremely low friction shafts impellers etc. That drives up
the cost.
So a low cost transducer is more likely to be inaccurate. A company I
worked for delved into designing such systems and we also built
calibration test meters for Ford Aerospace production lines. At low
speeds you can end up with a fuel gain instead of a net consumption if
the transducers are not matched and calibrated.
Now that we have electronic controlled injection it is much easier to
count injection pulses for a total count of fuel amount used. The
assumption being older style engines needing the more expensive analog
metering will gradually disappear.
Regards
Arild
-----Original Message-----
From:David
I became concerned about the fuel transducer specs taken from Navman's
website:
Flow Rates Max 400l/h and Min of 25l/h
25 l/h is about 5.5 gph which equates to about 100 horsepower. In a
diesel you need two transducers: one for the feed to the injector and
another for the return. The difference is your fuel consumption. I
emailed Navman to ask them if their system would work with less than 100
horsepower engines and they emailed back that the diesel system has been
withdrawn from the market.
REPLY
The problem is transducer accuracy. Most transducers will have a fixed
amount of slippage not to mention inertia. That tiny amount of error
becomes a bigger percentage as the total flow is reduced. In addition to
that turbine or paddle wheel style transducers have a certain amount of
internal friction. The only way to overcome that is to spend a lot of
money on extremely low friction shafts impellers etc. That drives up
the cost.
So a low cost transducer is more likely to be inaccurate. A company I
worked for delved into designing such systems and we also built
calibration test meters for Ford Aerospace production lines. At low
speeds you can end up with a fuel gain instead of a net consumption if
the transducers are not matched and calibrated.
Now that we have electronic controlled injection it is much easier to
count injection pulses for a total count of fuel amount used. The
assumption being older style engines needing the more expensive analog
metering will gradually disappear.
Regards
Arild
