A sub question...

I may be wrong (my wife says I usualy am) but i think they only ran with dessels on the surface and electric under the water.

Dave is correct....Thats why in sub movies there is always a big fuss over the batteries and their condition.

Later in the war they came up with positionable exhaust snorkles that could be put in the up position so the subs could run faster just under the under water.
Real sneaky like.

Dave and Papa Echo have got it right Lizardqing2.
The Type V11 U-Boat has two exaust ports near the back of the boat above the waterline[when surfaced]one Port and the other Starboard.Diesels were only used on the surface and when the Alarm was sounded the engine room crew would have to close both the inlet and outlet valves before the ballast tanks were flooded.
If the diesels were left running under the surface they would suck in all the air within a couple of minutes.
Papa Echo mentioned the snorkel sytem which allowed U Boats to run on diesels just under the surface,the snorkel device had both the air intake and the exaust outlet within the same housing.
The Germans also came up with a U boat design that used some sort of closed peroxide engines called the Walter engine i think,which allowed the U boat to run under the surface without having to surface to charge the batteries.
The Walter engines proved to be unreliable and dangerous so they were never widely produced. J.S.

Thanks for the anwers, thats what makes this forum great.

The Germans are back at it and have recently produced a closed-system boat roughly following the Walter design.

QUOTE: [i]The Germans also came up with a U boat design that used some sort of closed peroxide engines called the Walter engine i think,which allowed the U boat to run under the surface without having to surface to charge the batteries. The Walter engines proved to be unreliable and dangerous so they were never widely produced. J.S.

A further sidebar:
You may have heard reference in books or movies to the "main induction" valve ... this is the large pipe that draws air into the engine room for the diesels, and which is closed for diving.

This is the valve that got stuck open and sank Squalus off New England, which in turn led to the first successful deep water rescue from a submarine using Momsen's diving bell.

Some skippers left the main induction shut all the time, allowing the engines to draw air down the conning tower and through the boat to vent it for the crew as well.

JS is right albout the Walther engine. Designed to run on hydrogen peroxide, the chemical proved too unsafe to handle underwater and the designs were not mass produced.

Regards,
Bruce

Thanks for the additional info Bruce. Always good to find out how something works.

Cool info indeed! Thanks guys!

BUT! Bill the Cat was never a u-boat captain no matter what you have heard!

Just another tidbit .. Nuke boats always exhaust through snorkel mast.. Surfaced or Underway ..It's their only diesal exhaust. system, Same system is used to "ventalate "the boat with fresh air while submerged.
Diesels are used on Nukes to charge batterys the same way "Smoke Boats do" ..
Batterys are a back up to Reactor when Reactor is SCRAMED or shut down...
Early Nazi Snorkel systems were a death bell to any Boat using it.. The Uboats would broach and leave a huge wake and smoke/ condensation trail.. Easy for aircraft to spot even at night..

And yet another bit of trivia relating to the term "SCRAM". In the olden days of nuclear power development, the control rods were raised and lowered by a pulley system. The system used ropes and in case of super criticality (the reactor might be getting out of control in other words) the final line of defense was a guy stationed at the ropes with an axe to cut them which would allow the control rods to lower killing the reaction and thus saving the reactor core. This individual was called the Super Criticality Reactor Axe Man and is where the term SCRAM comes from. Whenever a reactor is shut down by the immediate lowering of the control rods it has been scrammed. (But not by a guy with an axe any longer, we've come a little bit out of the dark ages)