Anti syphon valve

[MAURICE]

Hi
I understand the purpose of the anti-syphon valve is to stop water syphoning back into the engine when the engine is switched off.
Can water enter the engine through the exhaust when the engine is running?
the engine was at cruising revs at the time and I wouldnt of thought that it would be likely.
What are your thoughts
stranger things do happen at sea

 

[ccscott49]

Ask Depsol about this, he lost an engine because (it was claimed) water came back up the exhaust. It is possible, but unlikely in most circumstances, if you have a water trap silencer and a decent size of rise in your system, highly unlikely.

 

[aztec]

water can't get into the engine thu' the exhaust valve when the engine is running. unless the water pressure is greater than the pressure of the waste gas (not likely) under such conditions the engine would have already stopped due to excessive back pressure. if there ain't no room to get the old out... there ain't no room to get the new in! if some one has told you that this can happen, call them a dick head.

the only possible way for water to enter the combution chamber is with the intake charge air, or through a cooling leak, or if the engine uses exhaust gas recirculation, and i've yet to see that on a marine type engine, but who knows.

good luck, steve.

ahh say what you like.... what's done is done!

http://homepage.ntlworld.com/s.amos/index.html

 

[ccscott49]

Volvo are obviously dick heads, because thats exactly what they said to Dom, (DEPSOL), when his engine self distructed! I said at the time they were full of shit, but they insisted and got engineers to back them, they said it got in, depite baffels a TURBO and the valves! So I wouldn't be too quick to call anybody a dick herad if I were you!

 

[aztec]

they need to go back and look at boyles law! if they don't uderstand the basics of why/how i/c engines work, how the hell can they be egineers?.. bloody fitters more like, ah new bits... bolt them on then!

by the way, ask the same people why it is that you can safely back your car down a slipway, and not suck up water through your exhaust pipe.
and have a look at landrovers etc, whole engines can be run submerged, as long as the intake recieves air via a snorkle.

sorry, personal experience of "marine engineers"

regards, steve.

ahh say what you like.... what's done is done!

http://homepage.ntlworld.com/s.amos/index.html<P ID="edit"><FONT SIZE=-1>Edited by aztec on 29/07/2002 11:00 (server time).</FONT></P>

 

[ccscott49]

yes, I agree, but Boyles law? anyway it wasn't the fitters, it was Volvo themselves and they brought in some high powered consultant engineer typoes and metalurgists! I'm also an old Diesel man, from way back, and up to date, I said at the time they were wrong, but he still had a great deal of trouble. Like I said they insisted it had come back through the turbos' spinning at christ knows what revs, a bunch anyway! Thats all folks!!

 

[aztec]

ok, 'nuff said, then. i still think that they're full of crap. just reinforced my opinoin of volvo.

seems to me that these engines are unsuitable for a marine application anyway!

chers, steve.

ahh say what you like.... what's done is done!

http://homepage.ntlworld.com/s.amos/index.html<P ID="edit"><FONT SIZE=-1>Edited by aztec on 29/07/2002 11:08 (server time).</FONT></P>

 

[MAURICE]

I agree that it seems very unlikely as more boats would suffer as a result and engine makers would have realised many many years ago and installed them with this in mind.
My engine is a volvo 2030 which has now been repaired, fitted to a Bavaria 34

 

[summerwind]

Just have to agree with aztec. It would have to be one hell of a wave to force water against the exhaust pressure of a running engine.

I could understand seawater getting in if you were sailing and didn't have enough lift in the exhaust system. In time, with sufficient heel etc, it could be that sea water could fill up the exhaust system and then the engine AND assuming that engine and most of exhaust system is below later line. The anti-syphone valve wouldn't stop that. Could even assist the process, maybe? But seawater getting in against a runing engine - no.

 

[andyball]

but if you gave it lots of revs, then closed the throttle quickly,maybe even shut down the engine?....combined with water over the exhaust outlet,and perhaps a few knots astern....? I'm not sure.

I always thought that when tackling water deep enough to cover the exhaust in a car,you should avoid suddenly closing the throttle to avoid sucking water in. (mind you, I "learnt" that so long ago, I can't remember where from, so it could be cobblers.)

 

[ccscott49]

It's not cobblers, when wading a vehicle in the army, we were taught the same. When wading for a long period, especially with diesel engines? we had to put extensions on our exhausts to keep them above the water, so just maybe!