Melted Pistons - Help
May 12, 2004, 03:46 PM
#47
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Originally Posted by lilgsx
Did you guys read the 720 degree temps in the Downpipe! Frist off the EGT probe needs to be 3 inches away form the head. So 720 degrees C at the down pipe would have the EGT at the combustion chamber well over 1100 degress C. Think about this once it hits the O2 housing it has a chance to expand and cool down. It cools even more when it hits the downpipe. Why do you think our o2 sensors are heated.
thats what i was saying, but i thought the difference was onley about 200 degrees or so difference. but they still would be too high. i think we know heat caused this, just whether it was detonation or else.
May 12, 2004, 04:01 PM
#48
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o2 Sensors
My o2 sensor is heated because Mitsu. wants to play closed loop fueling way before the motor is at a thermal steady state. How...because I feel this (on a stock CPU) when my water temp. guage is still showing an engine warmup and the car has a few herky jerkies at a very steady load. Annoys the crap outta me, but oh well...
good luck on finding the root cause of the problem!
j.
good luck on finding the root cause of the problem!
j.
May 12, 2004, 07:08 PM
#49
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alot of people will mount the egt sensor in the downpipe, as would I, however i would mount it right behind the turbine in the o2 housing, i know the old 4g63's had a boss there were you could drill.
the reason? well if it breaks after the turbo not to much is gonna happen but if it breaks before the turbo, your FUC*ED
the reason? well if it breaks after the turbo not to much is gonna happen but if it breaks before the turbo, your FUC*ED
May 12, 2004, 07:25 PM
#50
If you say starting at #1 there was no damage, down to #4 cylinder the most damage, I would be thinking along the lines of fuel starvation. As the fuel goes down the rail, each injector has less fuel available. Your pump sounds more than adequate, but maybe you went leaner as you went down the cylinders due to fuel pressure falling off. The amount of fuel into the cylinder is related to how much fuel pressure is available, the cc of the injector, and injector pulse.
May 12, 2004, 08:49 PM
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Fuel pressure was logged at max 4.6 bar at 1.65 bar boost and 3.0 bar at idle with vacuum off. injectors are 700 cc injectors.
Originally Posted by projekzero
thats a good observation 92tsi, id agree, check your fuel pressure and volume
May 12, 2004, 10:49 PM
#53
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so you are telling me that a egt should be in the downpipe? So in other wards take the instructions and throw them away and then tune your car to 900 degrees C EGT temps int he down pipe. Hummmm no your whole Engine would be FUC*ed. May the turbo would be ok. Thank god you put it there.
May 12, 2004, 10:56 PM
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Originally Posted by Predator67
Fuel pressure was logged at max 4.6 bar at 1.65 bar boost and 3.0 bar at idle with vacuum off. injectors are 700 cc injectors.
that looks the be correct. I would like to see injector duty cycle also. I do not think you were near maxing them out.
We are just getting bits and peices of info here. We need the full log of the run then we can give you some type of real hard answer.
May 12, 2004, 11:23 PM
#55
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Originally Posted by jcnel_evo8
This is probably not a new idea, but what about the oil squirters on the bottom side of the piston? Would clogging one of those allow a heating condition severe enough that the piston has a hard time shedding heat?
Later,
jcnel.
Later,
jcnel.
May 13, 2004, 06:42 AM
#56
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Having an Ultra lean condition in that chamber shows the evidence hence melted piston. Go over all fuel parameters starting with f-pump,injectors,spark plug heat range, Are you injectors blue printed? Injectors can vary greatly with distribution if not blue printed. Do you have a flash? If so who's is it?
May 13, 2004, 08:12 AM
#58
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Prob is that i can convert the log to an image (stupid jap software only works for that particular laptop).
Anyway the injector voltage seems constant all the way with no suddenly surges or peaks .
Anyway the injector voltage seems constant all the way with no suddenly surges or peaks .
Originally Posted by lilgsx
that looks the be correct. I would like to see injector duty cycle also. I do not think you were near maxing them out.
We are just getting bits and peices of info here. We need the full log of the run then we can give you some type of real hard answer.
We are just getting bits and peices of info here. We need the full log of the run then we can give you some type of real hard answer.
May 13, 2004, 08:26 AM
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I have heard of similar problems like this in the DSM's.
Are you using the stock fuel rails? #4 is the furthest away from the fuel rail inlet, right? I am wondering if you having problems keeping the volume of gas to the injecters the same accross all of them. If one injector goes lean, then it would more than likely, be the one furthest from the fuel rail inlet. That could easily cause the pre-ignition that started the damage that lead to your melted piston
With those big thirsty 700cc injectors I wonder if you need a larger fuel rail to handle the extra flow.
just my $0.02
Are you using the stock fuel rails? #4 is the furthest away from the fuel rail inlet, right? I am wondering if you having problems keeping the volume of gas to the injecters the same accross all of them. If one injector goes lean, then it would more than likely, be the one furthest from the fuel rail inlet. That could easily cause the pre-ignition that started the damage that lead to your melted piston
With those big thirsty 700cc injectors I wonder if you need a larger fuel rail to handle the extra flow.
just my $0.02
