I did that but Midway was full of Japs...?!

I know this thread is old, but I just can't see why people keep having problems with fuel usage. I haven't once run out of fuel whether it be with stock SH4 and patch 1.4 or with TMO for version 1.4. I think it is easier to monitor fuel in SH4 than it ever was in SH3. :D When I first started SH4, I was kind of annoyed that the stock game didn't include a "range at current speed" order button (now I think it is useless anyway). I was still able to find the sweet spot for my sub to give me the best fuel economy.

I think its because the basic game model is flawed. Sure, the US submarines averaged only 8-10 knots an hour on their trips, but thats because your spending roughly 10-20 days submerged. 10-20 days submerged knocks down your overall surfaced speed. Taking into account a low submerged speed means that the submarines were traveling faster than 10 knots while on the surface.

Also there is no individual engine controls, all four are running all the time, sucking up precious fuel. You would think there was no meaning behind an order "Two engine speed (80-90)", incidently this equates to about 14 and 1/2 knots. It means ONLY two engines are running, not four, and those two engines are at 80% rated load and 90% rated speed.

Personally, I use unlimited fuel, it's more realistic. However, I do conform to usual submarine movements and don't go racing all over the Pacific at 20 knots either. I'm usually cruising at about 14-15 knots, I'll go slower while in storms. No sense in pounding the boat to pieces.

Flawed reasoning on several levels
 

First of all several modders have investigated fuel range in the simulation and came up with small adjustments but found that fuel economy in the game is close to real. Top fuel economy in the game is at about 9 knots in every sub but the Sugar boats. Ranges are darn close to actual ranges expected in the real subs. You're way off base there.

The second place you're off base is in strategy. Spending 10-20 days submerged during a cruise is just plain folly. During the war, Admiral Lockwood would yank your sorry posterior out of that sub so fast nobody would know you were ever there. Submarines are surface ships which can submerge when absolutely necessary and for as short a period of time as possible. Their normal configuration is at 9 knot cruising speed covering the largest number of square miles they can in search of targets. The absolute necessity of every second of submergence must be accounted for.

That is why this thread has been buried so long. The questions and basis for unlimited fuel are long since discredited. With that in mind the "unlimited fuel" option wouldn't be there if it was not ok to use it. Just don't go around pretending it's more realistic.

do not forget in RL the US fleet submarine, unlike the german version, has no direct link from the diesel engines to the screws. US fleet submarines ran on electric power much like diesle locomotives 100% of the time to power the screws. all the engines on a fleet sub did was to turn electric generators to either or both charge the batteries and turn the screws.

also fleet subs if i remember correctly had a small tertiary engine just to charge the batteries over a longer period of time. but i am not sure about that.

I got round it by setting the diesel to infinite. Yeh its not realistic... but neither is what is expected!

That is why it is called a game. If it were a true simulation we would all stink like hell!:up:

You don't?:p

Biggest factor on fuel usage is co-efficeint of drag. Not being sure how they modeled fuel usage, ie: distance to time ratio or others it's hard to say how fuel usage is calculated.
When you first start out of port you're heaviest, full fuel, full stores, etc, here your drag is highest, as you lose weight your drag is theoretically lessened, think of it as thrust to weight ratio, my thrust hasen't changed but my weight has.
Granted there are going to be variables, some planned, some not; which will affect your consumption rate.
As to running while charging the best example is using your vehicle air conditioner. In general terms you'll increase your fuel consumption as the compressor draws a load from the engine.
Here again there will be variables involved.

Now!!! for running on the surface majority of the time.
Depending on the sea state you may not save as much as you think.
Running submerged may offset the effects of drag during high swells. Staying as close to the surface would be practical, as depth increases so does density, hence drag increases. Also staying in warmer thermals also would be more benefical than cooler layers, being that warm is less dense than cool.
So on and so forth, your mileage may vary.

I need to relay some info here....I recently started a new carreer and loaded up the newest TMO 1.5, RSRDC & PE2...I have always been very fuel conscious, but on my first patrol, I went to Guam out of Pearl (and man did I hit the jackpot BTW, lots of ships in port) and after sinking around 30 tons, headed home with 2/3 of a tank. Should be plenty right?....Wrong....I fell short by about 900 miles. I could not believe it. The seas were calm too. So I reloaded the most recent save and tried again at ten knts all the way home. Well..almost home..still about 500 miles away and out of fuel. I was pissed! So I tried to reach Midway and fell short about 150 miles. I ended up going to (can't remember the name) the closest port in Austrailia and then on to Brisbane to fill up again. From there I thought sure I could get to Pearl. Nope....after a little over halfway there, I could tell I was not going to make it so I changed course for Midway and BARELY made it. I have heard about currents being modeled accurately in the game, but currents that strong? There was something funny going on there! I have never seen or heard anything like this before and I've logged many patrols and carreers in this game. I don't know how reliable the "miles at current speed" report is, but according to it, I should have been able to sail about 14,000 miles. Comments?

@buffalo
 

Regardless of the sea state the greatest drag on the batteries is the drag of the electrics if you have to recharge your batteries. Part and parcel of the yo-yo strategy is having fully charged batteries almost all the time. This will always extend your range assuming you are optimized at 9 knots cruise speed.

Every time you submerge you lose. You lose ground traveled at a couple knots instead of 9. You lose square miles searched by radar and visually while you are on the surface. This means fewer square miles searched and targets not found. Then when you surface, you get lousy fuel economy at any speed while you bring your batteries up to full charge. Submerging is a lose, lose, lose proposition.

Submerging should only be done to save your life or cost the enemy his. Then its duration should be as short as you can make it. Every second your first thought should be "How quickly can I return to the surface? What can I do to be able to surface sooner?"

Exactly. A submarine has the ability to submerge for short periods of time and needs to be run like that. It is not a submersible that has the ability to surface for short periods of time. Best to keep surfaced and rolling, submerge only as necessary.

I do :oops:
(Sink like hell, that is)

There are no currents int he game. Rough weather decreases your range (it takes a higher propulsion setting to maintain the same speed in rough weather then it does in calm weather.

I have noticed mods which change the floatation model do not get as much range as the stock game. By lowering the boat in the water so less keel/prop is exposed in high waves, code sensitive to how much hull is submerged is activated reducing your speed and efficiency. For this reason alone (although there are many others) I do not use mods which effect the boyancy model. I'm willing to live with the look in order to get the historical speeds, dive, surface, and ranges the game was coded with (which is well proven.) Been playing the game for a year now and never had had to set infinate fuel or install any propulstion or battery mods. I've also never failed to get to and from a mission based on fuel. The stock game gives missions based on the performance the coders built into the stock model.
-Pv-

I agree 100%, being surfaced is much more practical than being under, but you can't effectively generalize it, there are just too many variables involved.
An example would be in rough seas, you loose about a 1/4 to a 1/2 your screw efficiency, spinning your wheels if you will.
If your only driving the boat half the time you're not making the progress you calculated for at the speed/rpm. You've wasted more fuel that it would have taken to move on batteries then recharge on a time/distance scale.

The charging system is actually quite efficient, you don't loose alot of torgue using a motor/genertor charging setup, the drag is negligible on the shaft rpm.

This being only a game I stay afloat alot of the time, even in rough water, and i dive to PD at flank speed with my attack scope fully extended, the boy's love it:p:p:p:p