Fuel Economy

Vehicles powered by Nissan six-cylinder SD diesel engines.

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dyepro
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Fuel Economy

#1

Post by dyepro » 6 years ago

The sd33 engines in my boat are supposed to be getting 3 imperial gal per hour at 2800 RPM after a few test trips it is using about 4.5 gal per hour. I am still resurrecting the boat after being stored a long time an likely abused before that. When I first got her running and replacing one seized motor with a good used one I did the fluids and filters but that's about it.
Now I am going to go ahead and do a fuel system clean with lubro-moly diesel purge and give the crank case a clean with seafoam. I'll change the filters and fluids again and adjust the valves. Any other "tune up" ideas with fuel economy in mind?
Thanks in advance for any good ideas.

plenzen
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#2

Post by plenzen » 6 years ago

Where did you get the number specs for that flow rate ?
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
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dyepro
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Location:Vancouver

#3

Post by dyepro » 6 years ago

I have a spec sheet that came with the original stanpower (sorry if I spelled that wrong I don't have it n front of me) engine/drive package.
My fuel economy is pretty terrible though it's costing me $125 for a little over a two hour trip @2800rpm.

plenzen
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#4

Post by plenzen » 6 years ago

That may very well say Simpower which is the company that I used to work for back in the 70's.

How many hours on those engines ?
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
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dyepro
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#5

Post by dyepro » 6 years ago

The hour flock on the boat says 1500 hrs and I replaced one with a low hour used engine I was told only 20 hrs but in any case it is a low hour engine from the looks of it.
Any idea what I should be getting as far as gpm?

plenzen
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#6

Post by plenzen » 6 years ago

That is kind of hard to say

There are a lot of factors here to consider.
Although 1500 hours on a marine diesel is not a ton we have to consider how it was maintained during that period of time.
I think you mentioned it was beat up a bit when you got it.
How efficient is the hull of the boat. Moss, barnacles,etc etc.
How big are the wheels you turning? Are they perhaps tad too big and your working the engines too hard. ( everyone wants or wanted more speed so,,,,,,,,, you don't get something for nothing )
A marine engine works harder, much harder than any automotive engine.
A generator running at full load would be about the only thing that may work harder.
How far have you got the throttles pushed to get the 2800 ?
How much smoke ?
White or black
Are the injectors dribbling or leaking
Condition of the fuel pump(s)
How much blow by on the 1500 hr engine compared to the newer one
More smoke ?
Do you have more throttle input on the 1500 engine compared to the newer one to achieve the same results.
Did the spec sheet say what the original prop size of the boat was ?

Also

Back in the 70's the diesel fuel itself produced more power just from how it was made. There have been many changes to diesel fuel formulation over the years the biggest is the reduction in sulpher content.
You are no doubt burning winter diesel right now and perhaps at the beginning of May when they start shipping summer diesel it will pick up a bit.
The new rules in Canada ( 2011 I think ) is that there must be 3% ( IIRC) bio content in diesel.
Because of the colder climates here ( in the rest of Canada not tropical like the west coast ) the bio portion gets cloudy and waxy quicker than just the summer formula. Therefore, the summer fuel will have up to 5% bio in it from May to October which ( so I am told ) balances to 3% +/- over the year.
Winter diesel is much lighter with the addition of more kerosene etc to keep it flowing in the cold and the cetane level drops as well with these additives. There is some debate that the refining process is different and I tend to believe that. In Canada you don't get a choice of diesel fuels like you can in the US. It's just DIESEL fuel. My personal experience with my SD 25 is I pick up approx 5-7 mpgs (imp) in the summer.
Heavier the fuel the hotter the flame generally.
I know long winded to get here but,,,,,,,,,,,,,,,,,,,
Spec sheets printed in the 70's for fuel blended/refined/formulated (whatever ) then will not necessarily equate to what is available now.
Add to that the hours on the engines, how big the props your swinging, the condition of the hull etc an extra gallon per hour may not be all that unreasonable.

IMO that is.

Just as a thought here you may want to look at getting some Cetane booster and try that.
Stanadyne Performance Formula is a quality product and, with the ULSD your using, and the old pumps, an additive such as this is recommended to keep the seals from dying ( which they eventually will ). There are a few other products out there as well. Power Service makes a pretty good one but the fuel injection rebuild places here all send a bottle of Stanadyne home with a freshly serviced pump. I think that Fred Holmes out there does as well.
I use it every tank even after the rebuild.

See here: http://www.stanadyne.com/view.php?id=45

HTH

Paul
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

dyepro
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Location:Vancouver

#7

Post by dyepro » 6 years ago

I did re wheel but my intention was only to get to the factory specs of a max of 3200 rpm at wot. The props that were on the boat were letting me go to 4000 which is the governened speed if I'm not mistaken. Also I went to a stock volvo prop rather than the aftermarket ones that were on there.
I agree with you on the stanadyne product many years ago it was explained to me that it the only additive produced by an actual pump manufacturer.
I'm just trying to do what I can cause $125 for a 2 hour trip is just crazy. I could be running big v8 gas engines at that price and be going Mach 1.
The whole idea of having the sd33 is economy

TOYoung
Posts:16
Joined:7 years ago

Re: Fuel Economy

#8

Post by TOYoung » 6 years ago

dyepro wrote:The sd33 engines in my boat are supposed to be getting 3 imperial gal per hour at 2800 RPM after a few test trips it is using about 4.5 gal per hour. I am still resurrecting the boat after being stored a long time an likely abused before that. When I first got her running and replacing one seized motor with a good used one I did the fluids and filters but that's about it.
Now I am going to go ahead and do a fuel system clean with lubro-moly diesel purge and give the crank case a clean with seafoam. I'll change the filters and fluids again and adjust the valves. Any other "tune up" ideas with fuel economy in mind?
Thanks in advance for any good ideas.
I'm curious what kind of boat, displacement, length of the waterline, etc, are you running? Seems like a lot of fuel unless you're pushing a pretty big hull at planing speeds.

What speeds do you attain running at 2800 rpm's or your cruising speed?

I have an SD22 in a full displacement sailboat hull that weighs 15,000lbs. I burn a little over a gallon an hour running at 6-7 knots.

My SD22 has the mechanical governor that limits it to about 2600 rpms.

As well as hull condition(bottom growth), the wrong prop size and or pitch can be a problem. Have you hauled the boat lately?

plenzen
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Location:Cochrane Alberta Canada

#9

Post by plenzen » 6 years ago

I would try putting the finer/smaller props back on and try that at the same RPM. You'll be a tad slower but not working as hard and just see.
( that may be why they were there in the first place )
If the old ones were allowing 4000 rpm at wot and these ones are only allowing 3200 it sounds like your working the engine(s) harder.
Nothing has changed with the governor(s), only the load on the engine.
(governed speed I think was 44 or 4500)

Also:
A total of 3 imp gals ( 13.6L ) over 2 hours based on $1.50/L is about 20.00 difference or 10.00/hr.
The price of diesel is very high now as well.
That difference may be more out there as diesel costs are higher in the YVR area with the carbon tax/transit tax etc etc etc.

I would disagree with you on the V8's burning less at a higher speed though, although that disagreement is based from the old carburetor days. Plus you would have used 3 of those engines by the time you hit 1500 hours.

As Tom asked you as well.
What speed are you trying to attain ?
Speed = $$$'s
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

dyepro
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#10

Post by dyepro » 6 years ago

Thanks for the replies guys!
With those old props I was only getting about 8-9 knots at 2800 the design of them was quit a low blade volume where as the orig volvo props were of the big elephant ear design so the aftermarket props had a lot of slip. The new props get me to 12 knots at 2800
I'm not a speed freak at all but I want to determine the best speed/rpm/fuel$$ ratio for this boat.
Also we commute to our cabin on gambier island. That's it, no pleasure cruising so it's always a set distance.
It's a big heavy 10000lb tollycraft 26 semi displacement hull with volvo out drives.
I'm still testing what works here and it looks like I've got a lot of testing to do still.

plenzen
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#11

Post by plenzen » 6 years ago

What was your fuel consumption with the old props at the same RPM, or did you test it with those ?
Retired Pauly
Problem with being retired is that you never get a day off.
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asavage
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#12

Post by asavage » 6 years ago

I know next to nothing when it comes to boats and props, but 4000 RPM seems pretty damned high for sustained operation of an SD engine.

An LD or CD, sure, but an SD?
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

plenzen
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#13

Post by plenzen » 6 years ago

Your right AL and the engines were not meant to be run at 4000 rpm continuous.
Someone "re-wheeled" the boat to a finer pitch/diameter prop and was allowing the engines to work less at a specific RPM.
I suspect trying to gain some economy, or maybe an economical trolling speed for fishing but not certain).

Down side is a higher RPM at WOT.

The stops/governor were set at WOT ( no load. in neutral, whatever ) to 44 or 4500 RPM. (may have been as high as 4700 but I cant recall specifically, but that is the ballpark)

The boat was then equipped with a specific prop ( pitch/diameter etc) to allow only 3200 ( in this case ) at WOT, to allow for the proper amount of fuel to achieve that.

4000 continuous would most likely cause failure, but, with little or no load at that speed would also cause glazing of the cylinders and not able to carry a load when asked to do so.

This may be the case here as well. Cylinder glazing may be a problem.

IMO of course

run a generator on standby for weeks or months/years at a time with no load and when asked to work a lot of them just lay down. Same thing here I think.
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

dyepro
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#14

Post by dyepro » 6 years ago

Hi everybody, thanks for the input.
To clarify nobody is running my engines at 4000 continuous that was reached during a test to determine some perimeters. I can't trust the props that were on the craft when I got her. They were aftermarket units rather than stock volvo ones and were an inefficient blade profile that allowed for too high an rpm and fuel economy issues due to slip.
I did the calculations and test flew some props before buying the new ones. My new ones have returned me to the factory specifications of 3200 rpm at WOT. That has to be the baseline to start from. Now I am trying to determine the best rpm range etc for efficient fuel economy. Speed is a byproduct of this process but is not my main concern. I simply want to know fuel usage vs. rpm.. The factory spec is 3 gal @ 2800 rpm (which is the max I ever run) Correct me if I'm wrong but shouldn't I get that performance rate regardless of weather it is in a frame, truck or boat whatever. The fuel usage is determined mechanically by the inj pump based solely on rpm. The amount of work done (speed) varies with load but the fuel consumption should be constant based on rpm.?

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