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I had the same problem last night and figured two things out:
1. If you do not disengage silent running, you will use up greatly more fuel, even on the surface. Disengage silent running. 2. Also, the engines are much more efficient if, once you have charged the batteries, you turn off the battery charger. Your mileage may literally vary. |
On the surface, applied physics would seem to indicate that running submerged on batteries would have less overall range than running on diesels alone, but this is not neccesarily the case.
While it's true that the energy in the batteries used for submerged travel is not "free" and has to be gotten from fuel reserves and that the fuel-diesel-battery-motor energy chain is not 100% effecient, it's still possible for battery / electric engine use to increase, not decrease the range of the submarine. I will try to explain using the most extreme case of diesel/electric mixed propulsion. Version A: A stopped sub with 0% charged batteries will run the diesel engines strictly as a generator to charge the batteries. Once the batteries have a charge, the sub uses its electric motor to move 10nm. Version B: A sub uses its diesel engines to drive 10nm. Which version uses more diesel? You may be tempted to say Version A uses more diesel fuel since the recharging, eletric motor process has more steps and thus more chances for energy to be lost due to heat, friction, 2nd law of thermodynamics, etc but it is not neccesarily the case. It is because the diesel engine does not have the same effeciency at all RPM! It is possible to charge the batteries at the RPM that is the most effecient for the diesel engine while maybe the best RPM for the diesel engine/ boat hull is not so effecient for the diesel engine. The convoluted fuel-engine-battery-motor process, despite having more steps CAN (in theory) be more fuel effecient than the diesel engine alone because of the variable effeciency of the diesel engine under various loads. Now I am completely uncertain about the following two concepts: 1. Were real life WWII submarines more effecient under mixed diesel-electric propulsion compared to pure diesel? It's theoretically possible but was it actually the case? Unknown. I thought German U-boats benefit from the mixed propulsion. 2. Are WWII submarines as modeled by the game (vanilla, modded?) more or less effecient under either method? Again unknown. MORE INFO AND CITE: http://www.ossapowerlite.com/tech_li...efficiency.htm Not all of the points made in this article apply to WWII submarines as they are designed, but there are plenty of valid points made that do. |
I don't think the game is quite as energy taxing as theory, but to make things even simpler:
-> The slower you go and the calmer the weather, the more range you will have be it battery or diesel. -> The more time spent fully surfaced the better as this is where drag is lowest in WWII boats. -> A bad storm can cut your surfaced range by 1/3 for the life of the storm. Anything over 8 m/sec wind adds significant loss. -> Recharge at the slowest surface speed possible so you spend the least amount of vulnerable surface time with a depleated battery. -> Silent running prevents your crew from performing maintenance or repair and reloading torps. This costs you in being prepaired for battle and a weakened ship and crew. -> Battle Stations improves crew response to damage and better all around command responses/targeting/sighting/sensing. The tade off is it tires out the crew very quickly and increases the noise level of the boat regardless of Silent Running. -> Return to port once in a while and purchase better crew to improve efficiency in all aspects of operating the boat as well as stamina. Conserve aggressively while you can so when the tactical situation requires it, you can spend what you have saved with equal aggression. -Pv- |
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I haven't tested this in the game but I'm sure others can chime in. |
Reality vs The Game
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But in the game I doubt it. I'd stick with the simple rule that it takes more energy to get from A to B on batteries then on Diesels. |
I've given all of the recommended conservation methods a try without much success. Topping off at Midway, 10 knots in passable weather, slower during heavy seas, shutting off the battery after recharge, diving only when threatened by aircraft. It may be due to game setup or the interaction between some of the mods and that setup or it may be that there is more heavy weather encountered than historically, but a Gato sub just won't go the distance that it went according to the books. A nominal 11,000 nm was expected from a Gato. I've kept track on a couple of missions and I get closer to 8000. I have know idea how low this would drop if I was less obsessive fuel conservation.
So I operate the boat as if I was trying to conserve fuel (even to the point of making hard decisions about whether to chase a convoy or follow a ship I've crippled) but when I come close to empty and I'm still 1000 nm from Midway I send for help. Rather than a flying boat, CinCPAC sends me a smart technician who knows how to open the save games files and reset the fuel to "unlimited". I then proceed to return to base so that I can continue my career. |
See what you get without the mods.
-Pv- |
Are you guys all using a Realistic Range Mod? [Due to computer limitations, I'm still on SHIII for the time being so excuse my relative ignorence]
If so, then there is no way that a Balo or any other class of Submarine is going to make it as far as the historical record shows they did. Silent Hunter III and IV use a Flat Earth model which means your quickest route to the Bungo Straits is to have a waypoint at Pearl and a waypoint at Bungo. In reality, the shortest route is to leave pearl, cross the dateline around 30N and then actually come along the coast of Japan. Just a theory, I don't have a copy of SHIV to test it on. But that maybe the source of your woes. |
If you're using Trigger Maru, you get a button in the navigator commands to estimate your range at the current speed. This makes it pretty easy to find the most fuel-efficient speed to travel at. (SH3 stock had this, but they removed it for some reason in SH4 -- but the code to do it is all still there. Go modders!)
I'm pretty sure my testing for whatever sub I have at the moment gave 2/3rds as the most efficient (I didn't test particular speeds, only the standard settings). Just enable a small amount of time compression (to reduce the time it takes for your boat to stabilise at a new speed), and then set a speed, check your estimated range, set another speed, check range again, etc. I haven't had significant problems with the range of my boat for some time, though early on I did end up stranded on a few occassions. |
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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.
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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
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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!
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That is why it is called a game. If it were a true simulation we would all stink like hell!:up:
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You don't?:p
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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?
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