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  #11  
Old 08-22-2013, 10:11 AM
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Pretty sure FAE blows engines. This is why Correct Craft is installing them on some models.
http://www.planetnautique.com/vb3/sh...signed-exhaust
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  #12  
Old 08-22-2013, 10:15 AM
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Quote:
Originally Posted by Traxx822 View Post
Correct me if I am wrong but something as simple as running 25mph and pulling the throttle back to idle and just slowing down can add back pressure enough to cause damage.

I just blew out an exhaust gasket that was brand new couple weeks ago. If it wasn't from back pressure I don't know what could have caused it.

Jim is right, 2, 3"-4" exhaust outlets run into a 2 1/2" single outlet is going to be more restirctive.
.
I think if throttling back from slalom speeds 30-36 would cause head gasket problems - more members would be reporting problems.

Correct me if I am wrong... head gasket failures are almost always due to 3 things... overheat, defect in gasket, or improper installation.
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  #13  
Old 08-22-2013, 12:43 PM
Quinten Quinten is offline
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I can understand that it will cause damage.
When you put something in the exhaust of a car the engine will block and turn off when it is full with gasses, after clearing the exhaust it will run again. And the pressure the engine will build is enough to blow a pato out of the exhaust.

For instance by a boat, there is probably a reason that the exhaust is above the water line when on speed.
With the FAE this is constant under water so at idle it can build up pressure because of the water.
When on speed it will suck the air and water and gasses out of your exhaust cause the venturi effect. This will not set any back presseru on the engine but I think it will suck on the engine to get more of it. Maybe this will cause the damage off that engine.

This is what I'm thinkin, so you can discuss.
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  #14  
Old 08-22-2013, 01:06 PM
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Quote:
Originally Posted by Quinten View Post
I can understand that it will cause damage.
When you put something in the exhaust of a car the engine will block and turn off when it is full with gasses, after clearing the exhaust it will run again. And the pressure the engine will build is enough to blow a pato out of the exhaust.

For instance by a boat, there is probably a reason that the exhaust is above the water line when on speed.
With the FAE this is constant under water so at idle it can build up pressure because of the water.
When on speed it will suck the air and water and gasses out of your exhaust cause the venturi effect. This will not set any back presseru on the engine but I think it will suck on the engine to get more of it. Maybe this will cause the damage off that engine.

This is what I'm thinkin, so you can discuss.
How is the FAE any different than a sterndrive in the case of the exhaust routing and back pressures?
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  #15  
Old 08-22-2013, 01:24 PM
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I was asking questions on the FAE thread about performance and changes the restrictions would cause without any real answers. I havent seen any dyno type results either. fact is, exhaust tuning makes HUGE differences to Hp/Torq output from these small blocks. My experience is more cars and LS motors with Blowers, but the cam profile definately should be mated to the exhaust (and several other variables obviously). Is this simply like adding a catback? Not really as that is designed to free up restriction, adding some ponies. I cant see how this doesnt reduce power incrementally, but Im willing to listen. Could it cause the bearing to spin, or rod to throw? Probably not on its own, but it could have accelerated an existing issue IMO.
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  #16  
Old 08-22-2013, 01:24 PM
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Quote:
Originally Posted by CantRepeat View Post
I would say it was installed incorrectly. Did anyone retorque the bolts after the motor was ran to temp?
That I am not sure. I think it was a combination of back pressure and a cheap exhaust gasket, not the head gasket as mikeg said, but CR, do you think that's viable that the combination of those things caused it? It happened right after throttle down and idle, went to speed back up, gasket was blown.

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  #17  
Old 08-22-2013, 01:46 PM
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There is no way the FAE caused the failure of a rod or bearing. As mentioned the back pressure is nil while under way with the FAE. I don't want to get all scientific and what not (Civil Engineering Degree lots of fluid mechanics) so lets just keep it simple. Will some back pressure be created by reducing the output are from the 2-1 when compared to the original specs without FAE, indeed. At rest there is no question the air flow is restricted a bit. Is this enough to cause harm to an engine? Give you performance issues? I would think you would see way more engines blown up if it did. Fact is it doesn't. I am speaking here in regards to a standard 5.7L V8. Is the restriction enough to cause noticeable performance differences? I would say if you hook the boat up to a machine and read its values there would be a definite difference in air flow and back pressure at rest/idle, but it would end up within the acceptable level. Also now stick that same boat into the water and the results will also differ. Now lets talk about when you get under way..... that back pressure is actually reversed and in simple terms. The flow of water passing the FAE now pulls the air flow through like a vacuum sucking exhaust out while moving thus increasing air flow. This helps compensating for the 2-1 reduction at higher speeds when more air/exhaust is being pushed through from the engine and being "sucke out" at a faster rate by the FAE. The open air without the FAE does not have the same effect while on plane.

Maybe some of the engine gurus can chime in, but these engines all have computers scanning and using all the data making tiny adjustments to optimize performance. I am thinking the small reduction the FAE causes at rest would be able to be compensated for by the computer. Kind of like operating a boat at high altitudes. Just because you are way up high doesn't mean you recode you entire engine. It makes the adjustments to perform at the consistent level its at. This is all just my pure speculation on the computer adjustment stuff.

I have logged over 2000hrs on my personal boats, all of which had FAE with ZERO performance issues. ALL 5.7L V8's. 750 out of the 1100 alone on my current Indmar LTR with FAE. I think your dealer is just looking for "an out". Anything that is aftermarket or added on to something will always be the first thing they blame.
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  #18  
Old 08-22-2013, 01:52 PM
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Quote:
Originally Posted by Traxx822 View Post
That I am not sure. I think it was a combination of back pressure and a cheap exhaust gasket, not the head gasket as mikeg said, but CR, do you think that's viable that the combination of those things caused it? It happened right after throttle down and idle, went to speed back up, gasket was blown.

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I stand corrected..
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  #19  
Old 08-22-2013, 01:53 PM
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I s ure hope my engine doesn't blow up tomorrow on me after all that typing cuz I would go insane. Time to knock on some wood or something
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  #20  
Old 08-22-2013, 02:27 PM
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Quote:
Originally Posted by markmcfarland View Post
Watch the video on their website. The shape of the exhaust creates a vacuum as water passes by. If the boat is not in motion ie revving engine in neutral them there may be some back pressure then. If you look at their graph on back pressure not until almost wot does the back pressure with an fae exceed one without. Back pressure only gets to around the 2 psi range. Running an engine on a hose will not simulate the vacuum that is created from the water passing by. There is another thread on here that says what this is called. It is something like "the vermillion effect". I know that's not the right word but its something like that.
I believe the word you are looking for is Venturi Effect .
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