CCPerformance

LOL,

Sorry Blue Thunder I just can't buy that one. Static & effective CR are two differant animals. If your valvers were as bad as you said, what water was there was likely squeezed right past them. Additionally, you're accounting for some unknown amount of water increasing the effective CR, yet this "water" would also have several other effects on the combustion process:

1) cool the mixture, effectively canceling or eliminating preignition / detonation

2) increase the perceived octain of you fuel, also countering detonation effects. (this has been done in big turbo application for 20 some years)

3) Most importantly - you are NOT encountering "reversion" at 4500 rpm. Once you reach a certain rpm say 1500 - 2000 ish, the exhaust gases are no longer being pulled backwards. If you were getting water in that cylinder at 4500 RPM it was coming from a leaking exhaust / manifold riser gasket or crack, leaking head gasket, cracked head / block, etc., etc,

Or quite possibly you just had a failed exh valve. Was it Inconel or good stainless or just std junk GM stuff. How many hours? I think you'll learn more when you tear that motor down. Thats my .02 cents...

blue thunder

Yes you are right CC.... failed exhaust manifold causing water infiltration. This makes the water mixture in the exhaust closer to the valves and caused reversion of fluid into the cylinders. I had an unknown valve composition, so they may have started tuliping as well. I believed this to be causing what I said....detonation. There were other strange things about this motor. High valve spring tension (unknown exact values) are one. That may have also started the malay.

Reversion is an interpretive word CC. The amount of reversion on an engine with a cam sporting a low LSA is often controlled by how far away from the valves the water mixes with the exh gas in the manifold. If the gas/water mixes sooner in the manifold due to reasons other than LSA, and gets sucked into the engine, it is still reversion. Just a different variable changing. I guess I am missing your point entirely. Seems simple to me.

If you think an uncontrolled amount of water in your combustion chamber is going to cool the chamber, you went to a different school of hard knocks than I. Pressure creates heat no matter how you slice it. More pressure creates more heat. Whether you choose to call that type of heat "detonation" or not is up to you. It has the same result either way. Your points 1 and 2 are incorrect with uncontrolled amounts of fluid mix in the chamber. Pressure creates HEAT!!! That is what I was suggesting.

Static CR is your base measure and relates directly to the effective CR with a given fluid/vapor concentration, within a given system (ie. engine). Change any variable (increase the fluid/vapor volume) and you create more heat. More heat creates all bad things mentioned.

Have you learned enough yet?

BT

Vinny P

WOW.......This one is getting deep. I am going to let you 2 guys argue this one out. Interesting reading from where I am sitting!!

CCPerformance

Hey BT:

I guess were going to have to agree to disagree on a couple things and I may need some more schooling.

First, to say that any pre-mixing of water is reversion is a little mis-leading. Were arguing semantics. I think you would agree that the condition Black Hawk was referring to was the traditional definition of reversion, i.e. water was being pulled back into the cylinder as a result of ineffective manifolds or cam lobe center choices, etc. You now acknowledge that your situation was reversion as a result of a water "leak". In my school, A water leak is completely different than a reversion issue. A leak is merely equipment failure. You can't tune for it. Changing valve springs, valves, cams or installing 10 foot tail pipes is not going to correct that problem.. If you’re mixing water any closer than say a stock Merc manifold or a Gil manifold as a result of a bad gasket or crack that is a "leak". That leak will likely occur at any rpm as where traditional "reversion" is an idle type situation hence you test for it at idle and the so-called Merc fix of increased idle.

As for CR, I agree that any obstacle in the chamber has the potential to increase pressure and or heat. But you must also recognize that adding 20 or 50cc of cold water is much different than adding 20 or 50cc of piston dome or decreasing the chamber by that amount. Also water in a cylinder with a narrow lobe centerline with questionable valve seal is not the same either. Hell for that matter you can build a motor with a static CR upwards of 10 to 1 that runs on pump gas given the right cam choice. If you think you had a marine motor taking on water in such severe heat & detonation that it snapped a valve head off then I doubt anyone can convince you otherwise. Perhaps you know best.

Thanks

blue thunder

Actually CC, the original question was "what is reversion". Technically, reversion is "when something goes back to where it came from"... in our conversation this thing was cooling water. In low LSA instances and internal leaks in the manifolds, water can get sucked back into the engine. This is at least an iterpretation of reversion.

Our conversation, symantics aside, was more focused around the affects of reversion on the internal operation of an engine. If I read you description correctly of the ill effects of reversion, you said valve train rust and hydraulic lock. Now I've never heard of hydraulic lock in a reversion case. Reversion in our definition only occurs when an engine is running. I suppose hyd lock happens in a running engine in extreme cases... maybe even did in my case. The other item, valve train rust... well rust is a static kinda thing as well, so I still haven't learned a different way than I proposed, on how reversion is bad to a running engine.

I guess you are saying reversion is good on low LSA grind marine engines because the reversion of water helps super chill the fuel charge? Well CC, we will have to agree to disagree on that one too. I would say in this case, you clearly know best.

BT

CCPerformance

Your missing the point BT. In that the initial post was as follows:

When they say water reversion with HP500's are we talking about the exhaust manifold(GIL) cooling water getting back into the engine or is it water from outside the exhaust pipe that makes its way into the engine? It is said that the cam lobe centerline has alot to do with this reversion...true? If this subject has been already been beatened to death sorry I've been busy............gofast

And the subsequent definition was as follows:

Reversion means that water is being sucked into the motor from the exhaust. This can be caused by too much cam overlap, too much duration, too short of a riser, etc...

I made the assumption you were referring to "reversion" resulting from a cam issue as in the case of a HP-500 or an equivelant cam situation. Therefore your detonation and valve issues seemed rather extreme.

Also what I meant about your definition of reversion was rather that I thought it was too all inclusive. Sure, any water "reverting" back into the motor could be considered "reversion". By the same token, one squirting a garden hose in the exhaust would also be classified as reversion. In the context of the initial post I think all would agree that reversion would be defined by any water being being sucked into the cylinder as a result of intake/exh pulses. Assuming the mixing is done as it was intended at least aft the riser.

Whereas in your application it appears water was leaking before the mix, perhaps in the manifold or in the riser gasket. Therefore the water was falling or leaking into the cyl, not being sucked back from the tailpipes as in the case of a normal reversion. Normal being at least as far back as a stock Merc set-up. I don't care what cam/lobe center you choose there isn't one in existance that will prevent water from getting in your cylinder in the situation you described, even if it were dry tail pipes.

Hopefully that makes a little more sense.

fili

that would be over the transom headers right .

seafordguy

no. Plenty of dry pipes that exit through the transom.

just so you’re aware this thread is just shy of 2 decades old. Feel free to start a new thread with your questions if you need to….