strange piston failure?
Thread Starter
Staging Lane
Joined: May 2017
Posts: 66
Likes: 0
It is likely that the temperature is adjusting the threshold for poor fuel behavior under certain conditions.
You are missing some critical components for temperature control:
1. EGT reference (gauge)
2. Control system (water injection)
3. Economy/Efficiency traps (coatings on the piston, valve, tubes which demonstrate desirable thermodynamic properties) blankets, wraps, shields
The efficiency features trap the heat for when the engine is making low power (cruise) which improves economy. The control system dumps the efficiency (ruins the economy) by injecting water (or methanol) when you see the EGT climbing too high for safe max power. EGT rate and peak are affected by location (probe install spot) so this location dictates how high the EGT is able to rise on the gauge.
To put it another way, when things get too hot, it doesn't matter what your timing is or air/fuel ratio, the 93 octane just explodes violently and damages parts. This is for any engine. Even if you dyno the vehicle or engine, you can't predict what the steady state variables are going to wind up at until you test it in the application at it's worst case scenario. For example if I was trying to build and sell a boat application engine with long-duration WOT, I would need to put the engine in an actual boat and run it at wide open throttle and find out where all the variables settled at, as many as I could. Then adjust the engine or engineering to compensate for variables that do not meet my criterion for safety factor.
You are missing some critical components for temperature control:
1. EGT reference (gauge)
2. Control system (water injection)
3. Economy/Efficiency traps (coatings on the piston, valve, tubes which demonstrate desirable thermodynamic properties) blankets, wraps, shields
The efficiency features trap the heat for when the engine is making low power (cruise) which improves economy. The control system dumps the efficiency (ruins the economy) by injecting water (or methanol) when you see the EGT climbing too high for safe max power. EGT rate and peak are affected by location (probe install spot) so this location dictates how high the EGT is able to rise on the gauge.
To put it another way, when things get too hot, it doesn't matter what your timing is or air/fuel ratio, the 93 octane just explodes violently and damages parts. This is for any engine. Even if you dyno the vehicle or engine, you can't predict what the steady state variables are going to wind up at until you test it in the application at it's worst case scenario. For example if I was trying to build and sell a boat application engine with long-duration WOT, I would need to put the engine in an actual boat and run it at wide open throttle and find out where all the variables settled at, as many as I could. Then adjust the engine or engineering to compensate for variables that do not meet my criterion for safety factor.
All our stuff I tune locally is 93 only and we typically dont run more than 14 degrees ever once full boost hits. Buddy's got a 5.3 @17psi 93 only and hes at 12 degrees peak and I start pulling timing aggressively once the IAT's get to 122*F. You have much more cushion for error on pump gas, especially if the AFR varies, if you keep the timing down.
All our stuff I tune locally is 93 only and we typically dont run more than 14 degrees ever once full boost hits. Buddy's got a 5.3 @17psi 93 only and hes at 12 degrees peak and I start pulling timing aggressively once the IAT's get to 122*F. You have much more cushion for error on pump gas, especially if the AFR varies, if you keep the timing down.
another thing that seems to have helped is pulling about 1.5* around peak torque. A gentle taper out and back in over like 1500 rpm.
timing mark just below the curve is what I aim for.
We hear alot about pulling timing at peak VE, but lets not forget also about the RPM advance curve, which tells us that sometimes at very LOW rpm there might be very small numbers. I've seen some negative numbers in the OEM maps. It is not uncommon to see 5* at 800rpm with some load.
It may also help to think of engines which require 93 and ping when 87 is used. Some engines will ping with 87 no matter how much timing we use because of the compression ratio, the number 87 and 93 are directly set because they are run in a test engine with specific compression ratios. A 0-octane (zero octane) fuel also exists: n-octane, which gives us the standard (or a place that starts at 0 on the octane scale so we can refer to 87 or 93 or 112 for example). An engine can fall between those two extremes: able to resist pinging on 87 with special timing maps, and yet also capable of using more timing with 93 and knowing the difference in the computer by sensing a knock condition and switching maps.
It may also help to think of engines which require 93 and ping when 87 is used. Some engines will ping with 87 no matter how much timing we use because of the compression ratio, the number 87 and 93 are directly set because they are run in a test engine with specific compression ratios. A 0-octane (zero octane) fuel also exists: n-octane, which gives us the standard (or a place that starts at 0 on the octane scale so we can refer to 87 or 93 or 112 for example). An engine can fall between those two extremes: able to resist pinging on 87 with special timing maps, and yet also capable of using more timing with 93 and knowing the difference in the computer by sensing a knock condition and switching maps.
Ill be honest, once I pull it at peak torque I never put it back lol. Too scared since I only tune on the street and don't have a Dyno to look for MBT. I will play with timing and AFR at the track some but that's about it.
That's what I thought when I saw the first picture but the plugs tell a different story. Most pistons show some peppering with detonation but I haven't burnt up enough to be an expert lol
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Verdad Gallardo I've seen a turbo LS blow two pistons apart on the dyno because of a boost leak. Good fuel, good timing, just too much hot air. Sad part was he knew the coupler was toast but didn't realize how important boost leaks were (or how important they are not to have).
you know know the dirty word
you know know the dirty word
TECH Apprentice
Joined: Sep 2006
Posts: 328
Likes: 3
Can you clean the threads off? It looks like in the 1 pic you have several turns of color in the threads. You typically only want 1 full turn of color....I don't know how those champion plugs relate to 7s, but they those threads also confirm too much heat in the chamber.
Thread Starter
Staging Lane
Joined: May 2017
Posts: 66
Likes: 0
Can you clean the threads off? It looks like in the 1 pic you have several turns of color in the threads. You typically only want 1 full turn of color....I don't know how those champion plugs relate to 7s, but they those threads also confirm too much heat in the chamber.
