<VV> Water Injection Re: Cracked Pistons

[frankcb at aol.com]

Jim,
    Are you sure that the water FLOW from your water injection system reached the combustion chamber even BEFORE it was needed to forestall detonation??  This can be a problem especially with pumps that are located relatively far from the injection point.  That's why I recommend keeping the water line up to the injection point pressurized with water using a "water hammer arrestor" with electric shut-off valves..  
    The other possibility is that not enough water was injected when it was needed.  Do you have a gauge or meter that shows the flow rate of the water as it's being injected??  You could, of course, increase the actual flow of water by simply using a slightly larger nozzle if you can't change the flow control mechanism.
    
    Frank Burkhard
    Boonton, NJ       


-----Original Message-----
From: James Cuneo <jamescuneo at hotmail.com>
To: virtualvairs <virtualvairs at corvair.org>
Sent: Wed, Jan 22, 2014 11:50 am
Subject: <VV> Cracked Pistons


Guys,I need some help from you engine gurus out there.I have cracked 3 pistons 
in the #5 cylinder in the past four years. 2nd time I thought it was a 
coincidence that it was the same cylinder, third time, now I wonder what is 
happening in #5 that sets it apart from the others.What I have:2G rochester carb 
modified.F/B turbo on 140 heads. Clarks Hi Tech pistons D cut to 8.25 crCrank, 
flywheel, Pressure plate, rods, pistons balanced.TB20 otto cam329 turbo 
dist.Wide band o2 sensor, cruise afr 14.5, boost afr 12.0SafegardWater 
injectionSecond time this happened was just last august so I recently installed 
water injection. Was doing a tuning run last Sunday when after a 5 second run at 
10psi I felt the piston give way. Safegard indicated no knock. I had done a lot 
of homework on water injection and was sure this would be the cure to this 
problem, it was not. Spark plugs all appear dark brown, #5 a little lighter 
brown in color. Piston failure mode is a crack forms in land between 
 #2 ring and #3 oil control ring, then travels to oil return slot in #3 
groove.Questions: 1. what is unique to #5 cylinder running hot, lean? I can 
imagine the hot air off the turbo being distributed there. 2. Is there a better, 
more appropriate piston to be using?I have decided to replace all 6 pistons with 
new. It appears there are only 2 choices of forged pistons easily available, 
Clarks brand and Sealed Power, which one?I appreciate all and any advice.Thanks, 
Jim Cuneo39 year corvair owner, Journeyman auto mechanic, FAA Airframe and 
Powerplant mechanic, Farm/ Industrial equipment mechanic.







 		 	   		  
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