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airtite
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« on: October 02, 2013, 12:51:36 AM »
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OK so I made quite a serious mistake somehow which has meant me sourcing a replacement block for my car, block is being shipped and I need to make sure that whatever the issue was it doesnt happen again. Car is a 2004 audi s4 with a pes g4 supercharger with a 7 psi pulley and supporting mods, bosch green 440cc injectors, devils own non progressive WMI running a single d03 nozzle pre charger. The car has been running as is for the last 10000km with no issues, I then went and had a couple of runs againest a new 3l supercharged s4 and the standing starts were a mess due to my clutch slipping, we then did a highway run from 3rd gear and once in 6th I lost power and saw smoke behind me slowly glided to the shoulder with the car stalling to the find the following the next day.  Now I can understand why a piston would melt BUT what doesnt make any sense is that the damage is ONLY on pistons 6,7,8 and only on the one bank, everything else is in perfect condition with no heat damage to either the piston crowns or head. Any ideas? |
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ddillenger
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« Reply #1 on: October 02, 2013, 08:32:42 AM »
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Were you logging AFR? Which bank gets fuel from the rail first?
I'd bet that bank was running lean.
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vdubnation
Turboman
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« Reply #2 on: October 02, 2013, 08:56:29 AM »
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airtite
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« Reply #3 on: October 02, 2013, 11:40:59 PM »
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Were you logging AFR? Which bank gets fuel from the rail first?
I'd bet that bank was running lean.
while I was tuning the afr on both banks was the same, that bank is the one furthest from the inlet into the fuel rail though.. |
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airtite
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« Reply #4 on: October 02, 2013, 11:42:16 PM »
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nope not the PES tune BUT I am pretty sure I did something wrong in my tune to cause this. I am just trying to figure out why the rest of the pistons are fine and only the last 3 on the one bank... |
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ddillenger
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« Reply #5 on: October 02, 2013, 11:45:18 PM »
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nope not the PES tune BUT I am pretty sure I did something wrong in my tune to cause this. I am just trying to figure out why the rest of the pistons are fine and only the last 3 on the one bank...
You should have had a wideband installed in bank 2. You ran out of fuel and ran lean. It's no coincidence that the last 3 cylinders to get fuel were the ones that burnt up. |
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« Last Edit: October 02, 2013, 11:47:32 PM by ddillenger »
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airtite
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« Reply #6 on: October 02, 2013, 11:49:55 PM »
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You should have had a wideband installed in bank 2. You ran out of fuel and ran lean. It's no coincidence the last 3 cylinders to get fuel burnt up.
I would agree with you if the damage to the piston was more extensive ie in the center of the piston and not just on the intake side and bear in mind I had driven the car to red line lots more than just this one time over the last 10000km. last logged run  |
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ddillenger
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« Reply #7 on: October 02, 2013, 11:51:04 PM »
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How were you logging wideband?
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airtite
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« Reply #8 on: October 02, 2013, 11:56:55 PM »
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these logs were from the lambda values
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ddillenger
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« Reply #9 on: October 02, 2013, 11:58:02 PM »
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So the B6 s4 has wideband o2's. What pump were you running? What was it rated at? How many miles on it? Flow rate plummets as pressure increases, but I'm sure you know that.
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airtite
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« Reply #10 on: October 03, 2013, 12:05:19 AM »
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So the B6 s4 has wideband o2's. What pump were you running? What was it rated at? How many miles on it? Flow rate plummets as pressure increases, but I'm sure you know that.
stock pump, 4bar fpr... honestly it looks more like detonation at that edge of the piston more than running lean to me but if that was the case I would expect to find the same damage across the board but it just doesnt make sense that its only those last 3 pistons, which then lends credence to a fueling issue. |
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ddillenger
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« Reply #11 on: October 03, 2013, 12:21:50 AM »
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I think you should have been requesting more fuel anyway, but it's irrelevant for the conversation at hand.
PES blower with a smaller pulley (High IAT's, super inefficient, undersized for the 4.2 to begin with)
Stock fuel pump (I tuned a B6 S4 with a stage3 2.7T, stock pump couldn't keep up over 4500rpm, it went really lean)
High compression
Lack of proper monitoring
Everything that I see points to bank 2 being starved of fuel and running lean. This is a fairly common failure to see when the hardware's not right.
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« Last Edit: October 03, 2013, 12:24:25 AM by ddillenger »
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airtite
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« Reply #12 on: October 03, 2013, 12:32:08 AM »
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I think you should have been requesting more fuel anyway, but it's irrelevant for the conversation at hand.
PES blower with a smaller pulley (High IAT's, super inefficient, undersized for the 4.2 to begin with)
Stock fuel pump (I tuned a B6 S4 with a stage3 2.7T, stock pump couldn't keep up over 4500rpm, it went really lean)
High compression
Lack of proper monitoring
Everything that I see points to bank 2 being starved of fuel and running lean. This is a fairly common failure to see when the hardware's not right.
To battle IATs I had implemented the WMI and looking at the EGTs it didnt go above 825C, I agree about the blower being undersized for the 4.2 fair enough but like I said car was running really well up until this point with multiple runs right into the redline. |
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ddillenger
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« Reply #13 on: October 03, 2013, 12:38:00 AM »
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This is just my interpretation of the evidence provided. Unless you were logging when it happened, it's all just speculation anyway.
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airtite
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« Reply #14 on: October 03, 2013, 12:40:21 AM »
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This is just my interpretation of the evidence provided. Unless you were logging when it happened, it's all just speculation anyway.
yup you are right, will just have to put it all back to together and do some more extensive logging to ensure I dont break it again... |
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