06-26-2009, 08:01 AM #1
What causes valve failures on Inconel Valves?
Can someone tell me if a lean condition on a SC boat will fail the piston or valve? Just curious as my RRFPR came from a boat the dropped an aftermarket valve. Usually pistons fail the top lands in blower motors, from my experience. Just want to confirm that my RRFPR is good, as I'm not seeing fuel pressure rise with iboost increases (higher RPM).
06-26-2009, 08:11 AM #2
If you are not seeing fuel pressure rise with boost rise, you have a problem.
06-26-2009, 08:23 AM #3
06-26-2009, 08:32 AM #4
06-26-2009, 08:35 AM #5
I added a walbro fuel pump to my conversion just to be safe. To many friend of the forum had issue's with the stock fuel pump taking a snooze a high RPM's and not doing a good job. It is only $75 bucks.
06-26-2009, 08:54 AM #6
Usually a valve fails from 1 of 2 things: either the pison hits the valve due to the valve not being able to close fast enough (valve springs too weak for the rpm), or the retainer/keeper fails and the valve drops into the cylinder (which then gets smacked by the piston).
A bad seat can also cause valve failure as hot gasses slip by the edge of the valve and errode the valve away.
06-26-2009, 09:33 AM #7
I would say that your RRFPR had nothing to do with the valve failing in the other motor. A few on here now have had issues with the RRFPR not rising. I personaly think it is not able to function at 70psi even with a walbro fitted to my ski I am not seeing a proper rise. R88
06-26-2009, 09:48 AM #8
I had the stock Seadoo pump flow tested.@ 70PSI+ The flow gose way down and the amp draw goes way up. As for a the valve breaking. It is possible to go lean enough to get the exsast valve too hot (1800 deg +) and the head breaks off.
06-26-2009, 09:55 AM #9
I've seen the posts of a Rrfrp not rising. Was hoping to try it again with a SC that is not skupping and bleeding off vaccum. I believe I'm on the edge of needing a rrfpr with 42's on my setup depending on who i talk too close enough not to damage anything when I can't get above 7700 anyway. Should have my x-charger tonight and possibly test it this weekend to verify adequate pressure.
Have my gauge remotely mounted to my hull to watch fuel pressurw.
06-26-2009, 10:00 AM #10
- Join Date
- Jun 2009
To answer your question about a lean condition damaging a valve or a piston, the answer is yes. An engine running too lean, especially a supercharged engine causes cylinder head temperatures to rise. This can cause problems with piston because as temp rises, oil can thin and the result is all of the problems that arise from not enough lubrication. The valve is a little more complicated. As the cylinder head temperature rises, the environment where fuel and air mix gets hotter as well. Gasoline, like all fuels, has a flash point or temperature which it will spontaneously (without spark) ignite. The higher the pressure, the lower the temperature required to spontaneously ignite the fuel. The supercharger, depending on the RPM, puts as much as 8 PSI in the manifold. However on a naturally aspirated engine, the manifold is in a vacuum state or -PSI. All of this translates to an engine which will detonate at a lower temperature. Detonation occurs on the compression stroke of a 4 stroke engine, when the valves are closed. Premature detonation causes a unique situation where a gas is attempting to expand, in an environment that is getting smaller. Thus pressure goes way up. The weakest point will fail and often it is the valves.
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