07-27-2007, 11:42 AM #1
Piston wash: Tell me what you think?
Here's the latest look at my piston wash, after about 1 hour of running. Looks a little rich to me. How much should I come in on the hi's? Left to right is PTO, CTR, MAG.
I'm still having some trouble with the motor. The engine started shutting down, like it was running out of gas. But it only took 6 gallons to completely fill it. Pulling all the way to 6,000 rpm before falling on its face. Was running flawlessly for the hour, before starting to do this. This was the same symptom I was experiencing before I holed the MAG piston last week.
One of the few things I hadn't done yet was moving the fuel pump down low, so I did that this am. Previously I had the 65 liter pump mounted in the stock location under the F/A.
07-27-2007, 12:22 PM #2
Im gonna take a stab at it an say that pto (1st pic) looks to be lean, almost as if its gonna burn a hole in the middle. You can kinda see were its starting to form. The middle (top rite pic) looks to be rich, an the last pic looks like it needs to be richend up a tad.
07-27-2007, 12:42 PM #3
Do you have that yellow fuel line on the pulse? xlint and I have a theory that maybe the fuel lines are collapsing at WOT. This is not proven just a theory. But the pulse line should be reinforced rubber.
07-27-2007, 01:19 PM #4
Yes, I am running Tygon as pulse line. I think I'll switch that.
How does my wash look?
I can't see how 15 gallons per hour through 1/4" hose would cause it to collapse under the suction. I do agree that it's flexible enough that it might degrade pump performance if used as pulse line.
I'm also running the "clunks" on my pickup hoses. Any opinions on those?
07-27-2007, 01:26 PM #5
The clunk looks good. Do you have a vac pump to see how much suction it takes to collapse the fuel line? Your wash look a little rich but I would leave it for now. Lets get you nose over at WOT fixed.
07-27-2007, 01:36 PM #6
Ok, I just hooked up some new Tygon to a MightyVac. Begins to oval at 27 in Hg. Not flat, but beginning to restrict.
Old Tygon fared less well. 18 in Hg. It definitely gets soft with use. And it loses it's pretty color!
If I hadn't been sleeping in Calculus class I could probably relate those vacuum #'s to flow rates, right?
07-27-2007, 01:40 PM #7
Also the fuel flow in the system is more than 15 gal per hour. The fuel pump is returning all unused fuel to tank so I would guess its closer to 70lph.
07-27-2007, 01:42 PM #8
07-27-2007, 01:51 PM #9
IMO, all three cylinders look rich. But what people forget, is that piston wash is an "average" of all throttle postions that you have been in recently. To get WOT wash, you need to do lots of WOT running. As soon as you start doing midrange cruising, you are now going to see evidence of that on the piston domes. It is very possible to be dangerously lean on top, but rich in the mid and vice versa. Just keep that in mind. I also notice that the edge of your "wash" is not crisp, which make me believe even more that you have different mixtures at different throttle positions. Also, no tygon for pulse line. It needs to be the reinforced black rubber.
07-27-2007, 02:02 PM #10
I will switch the pulse line to reinforced rubber before I go out again.
As an experiment, I took a 5 gallon gas can and a length of used Tygon equal to the total run of hose in the fuel system. Used a head of 4'. Started a siphon, and timed it. It drained the whole tank in just under 10 minutes. Equates to 115 liters/hour.
What does this prove? That I watched too much Bill Nye the Science Guy as a kid, mostly. Also proves that the unemployed have too much time on their hands... But I think it also proves that the hose won't collapse under the draw of 70 liters/hour, either.
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