Exhaust Water Depth Limit

As long as it is getting fresh air, it will run until you dont want to be in it anymore. To the roof and then some. I would guess that at a certain depth, the water pressure would be too great, but who would ever be 20+ feet under the water.
 
I've had my exhaust under 18"-2 feet with no issues. can't say much else, except I would guess it depends on engine size?

Why do you care though?
 
Like Metal said.. the engine will run as long as its getting air (snorkel) most air intakes are mounted to the "grill area" so if your air intake is under water... your engine isnt getting air. If you have a snorkel, it raises your air intake as high as the snorkel.
 
If let the engine stall for any reason, it creates a vacum when you try to crank it back. This in turn, sucks the engine full of water. As I stated before, why would anyone want to be 20+ feet under the water. The pressure will be too great at a certain point for the back pressure of the exaust to keep it out. If your engine is worn out, and has poor compression, it may not take much water. This is another reason to keep you RPM's up when you cross deep water. There is a pretty good chance that your engine would stall, even with a 10 mile snorkle, if you try to drive to France. Is that what you are asking????
 
Rich said:
I've had my exhaust under 18"-2 feet with no issues. can't say much else, except I would guess it depends on engine size?
Why do you care though?
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Reason I was asking was I was just curious cause I have heard that ehxaust snorkels are neccesary for deep water but then others say its not neccesary, I mean eventually I'd like to have my jeep in water up to my chest while im driving but thats a while down the road.

JSEsterly said:
Like Metal said.. the engine will run as long as its getting air (snorkel) most air intakes are mounted to the "grill area" so if your air intake is under water... your engine isnt getting air. If you have a snorkel, it raises your air intake as high as the snorkel.
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Yea I understand the intake needs to be snorkeled but I was refering to exhaust snorkels for while your actualy driving where people rout their exhaust up high.
 
MetalMangler said:
If let the engine stall for any reason, it creates a vacum when you try to crank it back. This in turn, sucks the engine full of water. As I stated before, why would anyone want to be 20+ feet under the water. The pressure will be too great at a certain point for the back pressure of the exaust to keep it out. If your engine is worn out, and has poor compression, it may not take much water. This is another reason to keep you RPM's up when you cross deep water. There is a pretty good chance that your engine would stall, even with a 10 mile snorkle, if you try to drive to France. Is that what you are asking????
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Yea I realize that if you cut off the engine the motor would flood but I was thinkin more along water comin in while your driving, but I guess thats not an issue
 
So if the engine stalls and the exhaust is under water it would be better to get towed out of the water rather than trying to start it up and drive out?
 
I'm just talking out my ass here... but wouldn't this differ dramatically w/ engine and exhaust size? AKA if you hasve a small 2L w/ exhaust that is a bit too open (say 2.5") then the exhausting pressure is pretty weak, esp at low idle... but a bigger motor/smaller pipe would be much higher pressure, and less of a problem?I say this only b/c on the 4x4Wire Toy board i've seen guys mention problems w/ stalling underwater unless they keep it well gassed....
 
figure 15psi of pressure for every 33 feet of water (1 atmosphere=33 ft of water=15 psi) so as long as your exhaust pressure is over 15psi, you can drive through 33ft water without worry of water backflowing up the tailpipe. However if your timing is off a little the exhaust valve may still be open on the piston downstroke causing a bit of a vacuum in the tailpipe yet it shouldnt be long enough in duration to allow the water to reach the engine.
 
wouldnt it also depend on your RPM's and exhaust size/flow??


like 2" exhaust at 3K RPM's makes 1.5 times the pressure of 3" exhaust at 3K, so alot less water would get in, correct?
 
Seriously, this would depend on the vehicle and driver. You could have a million answers to this.
 
It should be a calculatable value, physics and laws of fluid flow. Unfortunatly, i have to stay up almost all night tonight to change over to night shift, so if i get bored.......what engine/exhaust setup are you running?

Tony
 
I give up. After looking around, I dont think it's as much the water making it to the engine as it is the backpressure getting too high for the engine to expell all the exhaust gasses. Just remember that if your engine does die whilst crossing water, DO NOT try to restart it, that is where it will draw the water into the engine.

Tony
 
Damn Ricky, you've really made people rack their brains on this one. I've got to give my 3 cents though, since i go to carolina and all, haha. After about 5-8 feet of water, most engines will not be able to produce enough pressure to keep the water from coming in the exhaust. I dont know what the guy with the 33 feet of water was talking about. that's nuts. And everybody who mentioned rpms and exhaust diameter, that's where the trick is. big motor, high rpms, small diam exhaust = lots of backpressure and deeper water. the exhaust "snorkel" serves 2 purposes. one already mentioned is the vacuum created with the engine starting, and the other is the strain on the motor to push exhaust through several feet of water. you're going from near free flowing exhaust to really insane backpressure if it's deep, so it's gonna screw with your hp, rpms, and whatever else that is probably important to get you out of the water. it's all common sense man, but wont your feet get wet??
 
the 33 feet came from a simple pressure conversion. 1 atmosphere is equal to 33 feet of water. therefore at 33 feet of water you will experience 1 atmosphere of pressure which is 14.7 psi. when the exhaust leaves the valve it expands into the header thus experiencing a pressure drop, the bigger the pipes the greater the pressure drop. since ehaust leaves the engine in pulses, the lead end of the exhaust will still have some pressure to it, while the tail of the pulse will be at a vacuum, the deeper the water the harder it is for the plses to overcome the water pressure. I had forgotten about the expansion after the valve, What are you studying at State? Just wait till fluid flow, its actually pretty interesting, at least where i learned it was.

Thanks
Tony
 
Deuce 40s said:
Damn Ricky, you've really made people rack their brains on this one. I've got to give my 3 cents though, since i go to carolina and all, haha. After about 5-8 feet of water, most engines will not be able to produce enough pressure to keep the water from coming in the exhaust. I dont know what the guy with the 33 feet of water was talking about. that's nuts. And everybody who mentioned rpms and exhaust diameter, that's where the trick is. big motor, high rpms, small diam exhaust = lots of backpressure and deeper water. the exhaust "snorkel" serves 2 purposes. one already mentioned is the vacuum created with the engine starting, and the other is the strain on the motor to push exhaust through several feet of water. you're going from near free flowing exhaust to really insane backpressure if it's deep, so it's gonna screw with your hp, rpms, and whatever else that is probably important to get you out of the water. it's all common sense man, but wont your feet get wet??
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Yea man, I hate wet feet, lol but yea I think I got the idea now, my main concern was just since my jeep is runnin dump pipes like right out from the headers weather or not it was gonna be able to push it all out under water, cause like the first thing im gonna do when I finish the jeep is go drive it off the boat ramp in my neighborhood to make sure I waterproofed everything ok.


redjp said:
the 33 feet came from a simple pressure conversion. 1 atmosphere is equal to 33 feet of water. therefore at 33 feet of water you will experience 1 atmosphere of pressure which is 14.7 psi. when the exhaust leaves the valve it expands into the header thus experiencing a pressure drop, the bigger the pipes the greater the pressure drop. since ehaust leaves the engine in pulses, the lead end of the exhaust will still have some pressure to it, while the tail of the pulse will be at a vacuum, the deeper the water the harder it is for the plses to overcome the water pressure. I had forgotten about the expansion after the valve, What are you studying at State? Just wait till fluid flow, its actually pretty interesting, at least where i learned it was.
Thanks
Tony
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Yea well I'm a slacker studying Buisness simply cause I hate math and all enginering is is Calculus and physics, plus I have absolutly no idea what I want to do after college, lol.
 
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