Engine failure – again
09-13-2010, 07:27 PM
#46
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09-13-2010, 08:08 PM
#47
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09-20-2010, 09:43 PM
#52
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Having spoken to even more gurus since my last post - including those with unimpeachable credentials - we have concluded that I was running all the tunable parameters at or slightly beyond acceptable limts, i.e. timing (35 BTDC), plugs (NGK 6 heat range), fuel (91 octane), AFR (13.2 at 6000). But the catalyst that led to the eventual failure was inadequate cooling in the left bank, which occurred because the heat exchanger to heater control box 3" hose had come adrift, allowing the cooling air to bypass the cylinders more than usual. I noticed this before leaving home but didn't bother to fix it, since I didn't think I'd need cabin heat. The demands of Road America might have eventually caused a failure anyway, but this lack of cooling caused two of the left bank's plugs to self-destruct. We will rebuild the same engine and tune accordingly, adding data logging of AFR and CHT.
09-20-2010, 09:56 PM
#53
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Then, I would say that very little has actually been learned here.
You may have been running at the very outside edge of what is allowable... And you popped it......twice. Richen it up a tad, back off the timing a touch, and put some better gas in the tank when you're tracking the car. For goodness sake, we're not racing for money here, we're doing track days. put it on a dyno, and richen it up, I'm guessing you will NOT see an output decrease. Then Max out the torque curve with the ignition timing NTE 35' and you're done.
Or you can continue to reinvent the wheel and hope for better luck this time. I'm sure the heat issue contributed, but you were flat running it too ragged, and you got caught. Please don't advertise for others to follow in your footsteps.
You may have been running at the very outside edge of what is allowable... And you popped it......twice. Richen it up a tad, back off the timing a touch, and put some better gas in the tank when you're tracking the car. For goodness sake, we're not racing for money here, we're doing track days. put it on a dyno, and richen it up, I'm guessing you will NOT see an output decrease. Then Max out the torque curve with the ignition timing NTE 35' and you're done.
Or you can continue to reinvent the wheel and hope for better luck this time. I'm sure the heat issue contributed, but you were flat running it too ragged, and you got caught. Please don't advertise for others to follow in your footsteps.
09-20-2010, 10:26 PM
#54
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Not sure there's a revelation here. Seems to me that Steve nailed it the first go. I'd say he retains his "Guru with unimpeachable credentials" status.
I'd question how much effect the heater hose, or lack thereof had. There are a lot of track cars running all variants of heat, no heat, backdated, semi-backdated, etc. As Ryan said, you were running the ragged edge, and that is truly what cost you here.
I'd question how much effect the heater hose, or lack thereof had. There are a lot of track cars running all variants of heat, no heat, backdated, semi-backdated, etc. As Ryan said, you were running the ragged edge, and that is truly what cost you here.
09-20-2010, 10:28 PM
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Please read carefully - I said "tune accordingly". I've already said in an earlier post that I would back off the mentioned parameters. All the good advice has not fallen on deaf ears.
