Reversion????

[Will]

What is reversoin? http://www.checkmate-boats.com/infopop/emoticons/icon_confused.gif

[Will]

What is reversoin? http://www.checkmate-boats.com/infopop/emoticons/icon_confused.gif

[175checkmate]

I might be wrong but reversion is when during the cam rotation event, if there is too much seperatio in the duration (lobe seperation) water is pulled in to the engine from the cooling water going out the exhaust.
Its sort of a very sort vacuume pulse.
I think.

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1975 Checkmate Tri-mate 2, 2.4 200+

[Will]

That doesn't sound like it would be very good at all on an engine! http://www.checkmate-boats.com/6/ws/,s,8626072361/Graemlins/Eyecrazy.gif

[175checkmate]

I agree, It would make for a bad day.

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1975 Checkmate Tri-mate 2, 2.4 200+

[Z06]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by 175checkmate:
I might be wrong but reversion is when during the cam rotation event, if there is too much seperatio in the duration (lobe seperation) water is pulled in to the engine from the cooling water going out the exhaust.
Its sort of a very sort vacuume pulse.
I think.

http://www.checkmate-boats.com/6/ws/,s,8626072361/avatars/rooster_3.jpg


1975 Checkmate Tri-mate 2, 2.4 200+<HR></BLOCKQUOTE>

Having a rough day? Enough typos man? Sorry to be picky, I just find it funny...

separation
vacuum

Sorry again... http://www.checkmate-boats.com/infopop/emoticons/icon_rolleyes.gif

~~~~~~~~~~~~~~~~~~~
Chevy Corvette Z06
Chris.Ellard9@sympatico.ca
http://pub37.ezboard.com/bchevycorvettez06personalforum
http://www3.sympatico.ca/christine.ellard/checkmatelogo.jpg

[vinny p.]

Reversion by definition is the drawing in or drawing back of water into the engine through the exhaust valves. This is caused by a combination of-- too short of an exhaust system and valve overlap.
First valve overlap. Every cam has valve overlap. Some more than others. Valve overlap is determined by 2 things on a cam shaft. Lobe separtion and duration. In a 4 cycle motor, at the point between the exhaust stroke and the intake stroke, the exhaust valve does not completely close before the intake valve begins to open. As the piston is beginning its' downward travel sucking in the air fuel mixture, it also sucks in some exhaust. This is also called scavenging. Being that marine engines have wet exhaust systems, it is here that it becomes possible to draw water into the engine. What dictates the amount of reversion in a cam profile is the lobe seperation and duration of the lobes. Lobe seperation is the distance ( measured in degrees ) between the 2 lobes. Duration is how long the valve is held open. So, as the lobe seperation is decreased( lobes are closer together), and duration is increased ( valves are open longer ), the possibility of reversion increases.

To compensate for this, aftermarket exhaust companies manufacture their risers to mix the water with the exhaust gases as far back as possible. In full dry systems, they don't mix at all. The further back the 2 mix, the more reversion would be needed to suck back in the water.

[175checkmate]

Vinny, Yep I knew it was something like that. And yes Z, funny stuff. I guess I need to wake up prior to typing.

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1975 Checkmate Tri-mate 2, 2.4 200+

[85diplomat]

Technically, "scavaging" is a little different.
"As exhaust moves down the exhaust pipe, the enertia of the exhaust, leaves a vaccuum behind it. This vaccuum can be used to pull fresh air/fuel into the combustion chamber when the intake valve starts to open. This enertia can also leave vaccum in the exhaust tube after the exhaust valve closes. This can suck the exhaust into the exhaust system making it more effecient. This effect only takes place, however, in systems that utilize headers designed with the correct length and diameter tubes."

(quoted from Small Block Chevy Marine Performance, by Dennis Moore)
A great reference by the way.

17' checkmate "Cheap Thrills"