View Full Version : Slow speed low fuel consuption correct?

03-19-2005, 12:02 PM
I noticed yesterday when panicking after realising i was low on fuel that the slower you go the less fuel you use. "Well duh!" You may say to me but i was not aware this was the case the 1/3 was optimum (which it seems to be)

I thought the endurance ratings, 6000 miles at 12 knots ect, were the best settings. Like in a car, going 10 miles an hour is worse then doing 40 miles an hour, but 100mph is worse then 40 also.

Anyone know for sure the truth on this? I noticed if you go slower then 1/3 then range drops again, so it isnt just set to the slower you go the better fuel, it is optimised for 1/3 (or there abouts)

Thanks for any info. ps its not a complaint, im just fascinated by it all.

03-19-2005, 12:08 PM
i manice to get back to wilhelmhafen..with slower speed..range increases with slow speed.. http://forums.ubi.com/images/smilies/blink.gif

03-19-2005, 12:10 PM
Ya I checked this out as well. 1/3 was what I used if low of fuel.
I do feel bad though because we only have so much time and to cruice the ocean blue at 1/3 is going to take up my in game time.

03-19-2005, 12:37 PM
The reason 10 mph in a car is worse than 40, is that even though you burn less fuel to operate at 10 mph, it takes you so long to get there, you use up more overall. The ranges listed in the specs seem to be based on the "Ahead Standard" setting. Personally, it looks to me like "Ahead 1/3" is more efficient. In a VIIB, I get 12-13 knots at standard, while 9-10 knots at 1/3, but the range increase is much larger than 30%.

03-19-2005, 12:54 PM
~Yeah i understand the reasons, and i know that 1/3 is most efficient in game, what im asking basically is "is this correct?" I would think the range they gave you in the info for subs 6000 miles or whatever was at optimum speed. I wouldnt think 1/3 ahead would get you any further fuel wise. I would think it would take longer AND use more fuel!

Good to see you all have the same experience though http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif @ kiwi i just use slow on the way back if i am low, usually you can get there and back without going so slow, because you run out of torps first. Just use 1/3 for emergency fuel saving on the return leg http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

03-19-2005, 12:57 PM
Ya I highly advise for each sub/engine combo you get you check with navigator and get range at current speeds downpat.
I usually start at 5 knots on diesel and go up every 2 knots to get ranges all way to flank every new engine/sub I upgrade or start with.

03-19-2005, 01:06 PM
As Olebass was saying, manually setting knots is a better way of tweaking the 'milage' of your boat. I play around with it knot by know until I get enough for there and back again, along with a resonable patrol amount, and then a small reserve for chasing down that fat tanker ....

03-19-2005, 01:23 PM
I just upgraded from the Type IIA to the D and the range is a lot better for those patrols around Great Britian. I used to set speed to 2/3 at about 7 knots to get there and back in the IIA. With the IID I found I can go standard speed and get to where I want to go with a whole ton of fuel to spare...total range to partol grid is about 1200 Km or so...max range at standard speed (10km/h) is about 8000Km! Thank God for those new fuel tanks almost doubles the max range according to the manual! http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

03-19-2005, 01:27 PM
Wait to you Upgrade to A Type VII. The difference between the VII and II is like Night and Day.. Sucks Took me so long to get one, I should of stayed in a Type IIA until I had enough renown for the VII. BUT NOOOOO, I had to try the IID.

03-19-2005, 03:44 PM
In short, yes: there is a medium optimum speed for cars, planes, boats, you name it.

You could easily determine the most effecient speed if you had the "km per speed" graph.

And you could get that by multiplying the curves of Horsepower vs Speed, and GallonsPerHour vs Horsepower.

So when you're going slow, you're using a some fuel to go slow. At a higher optimum speed, the engine is operating at a more efficient speed per GPH. And again at flank speed you have to overcome a water resistence that rises as the cube of your speed while burning a lot of fuel you don't go very far.

I really would like to see a curve of fuel consumption per km vs speed in km/h. It'd look like a U that climbs very steeply after the dip in the middle.

03-30-2005, 11:02 PM
Ocean currents dont seem to be adventageous to our sub nor hurt our sub's efforts to proceed so seems thats not in the sim. With that in mind seems the best way to save fuel is to do 1 knot. Of course this isnt fun. 1/3 speed is bets bet I agree. Its the best I can use.

03-31-2005, 05:43 AM
Hi all,
Admittedly i'm no expert in the field but these are my thoughts and experiences :
1. I know from experience, (having owned 2 diesel cars over the years), that the power vs revs graph is a squashed omega shape (for want of a better description) highest power in the mid 2000 rev range, and best fuel consumption at the same point
2. Revving higher than the mid 2000 revs range, seriously knocks the fuel economy.
3. Any sea going vessel after a certain speed, requires much higer power outputs for each 1 knot extra speed
So therefore it is reasonable that the fuel economy is seriusly improved at the lower speeds IMHO... http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

03-31-2005, 07:03 AM
also at 1/3 - slow you are only usng one engine, which also helps w/ fuel issue!

also cycle D. engs w/ elec engs to extend range -

in a type IXB and having to go to bottom tip of africa from brest isnt to much fun! there really isnt enough fuel to make it there and back...

03-31-2005, 07:24 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by aquasal:
also cycle D. engs w/ elec engs to extend range <HR></BLOCKQUOTE>
Don't do this, when you resurface the other engine will start to recharge the batteries again. The energy doesn't come from nothing and your fuel consumption could even become worse with this procedure.

03-31-2005, 08:03 AM
It's a submarine. Isn't it meant to go about its business under water ? I dive to periscope depth and thus use the batteries. When they're down I surface and charge batteries to max and dive again. I always return home with just one third of my diesel wasted and always plenty left for emergencies.

04-06-2005, 11:30 PM
Topic moved to Com. Help April 7 2004.