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Melted a piston - unsure why.

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Old 06-29-2018, 09:07 PM
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Default Melted a piston - unsure why.

Hello, new to the site and I need some help. I have a single turbo 78/75 billet camaro, 3 bar factory computer setup. Had the car running 3-4 months now on 6#, and then 9# and all was well. Turned it up to 11# and melted the top edge of #1 piston and it blew down through the side of both rings and through the whole piston.

timing was 11* through peak tq up to 5k then ramped up to 14* to shift point.

Iat was 102 at the start of the pull and ended at 152*
11.2 afr but it did creep to 11.5 around 6,000 rpm and the. Start to go back to 11.2 at shift point.

Pump gas 91 octane, 3Ē exhaust dumped, 2.:5 hotside

did it do it because it went slightly lean coupled with high Iats? Help me out here. Will post a picture tonight. 9.8:1 comp
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Old 06-29-2018, 09:08 PM
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Originally Posted by 99camaroturbo View Post
Hello, new to the site and I need some help. I have a single turbo 78/75 billet camaro, 3 bar factory computer setup. Had the car running 3-4 months now on 6#, and then 9# and all was well. Turned it up to 11# and melted the top edge of #1 piston and it blew down through the side of both rings and through the whole piston.

timing was 11* through peak tq up to 5k then ramped up to 14* to shift point.

Iat was 102 at the start of the pull and ended at 152*
11.2 afr but it did creep to 11.5 around 6,000 rpm and the. Start to go back to 11.2 at shift point.

Pump gas 91 octane, 3Ē exhaust dumped, 2.:5 hotside

did it do it because it went slightly lean coupled with high Iats? Help me out here. Will post a picture tonight. 9.8:1 comp

also my first thought was an injector, since it hurt #1 piston but not 7, had them flowed and #1 injector is flowing 9cc more than #7, so Iím at a loss.
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Old 06-30-2018, 06:38 AM
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I don't see anything wrong with the info you've given so far. What intake, plugs etc? What do the other plugs look like?
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Old 06-30-2018, 03:47 PM
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Default High EGT = Piston Damage

Hi 99, LOW Spark Advance (11* ) AND TOO MUCH fuel (11.2 AFR) will melt a piston VERY FAST.
Similar to a Diesel when it too is over fueled.

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Old 06-30-2018, 04:08 PM
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Hey guys, thanks for the replies. Iím running br7ef plugs, and factory ls1 intake and rails. Iím skeptical that too little ignition timing could have caused this, but Iím not a professional tuner. Iím not sure what to think here.
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Old 06-30-2018, 04:46 PM
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Originally Posted by pantera_efi View Post
Hi 99, LOW Spark Advance (11* ) AND TOO MUCH fuel (11.2 AFR) will melt a piston VERY FAST.
Similar to a Diesel when it too is over fueled.

Lance
Completely disagree. You need low advance at peak torque, especially on 91 octane, it melted a piston I.e. the combustion temps were too high.....I think 11 psi, 91 octane, 15 degrees and 11.5 AFR on 91 octane, I'm not surprised it blew. Too lean and too much timing for that boost and octane.
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Old 06-30-2018, 05:40 PM
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Meth injection would help. Yea i agree i think thts to much timing at tht octane and boost.
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Old 06-30-2018, 05:53 PM
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SBE ls1?
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Old 06-30-2018, 08:11 PM
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Yes stock ls1, I should also mention it bent the connecting rod slightly, so Iím certainly leaning towards detonation. 14* at 11# is too much for 91 octane? The internet sucks, I sure see a lot of conflicting information and it makes it very hard to decide on who to believe. Iím trying to stay away from meth, I might buy a Garret intercooler to help.
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Old 06-30-2018, 08:14 PM
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Do you think it would be fine at this level of boost with a 10.9/11.0 afr?
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Old 06-30-2018, 08:37 PM
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Originally Posted by 99camaroturbo View Post
Yes stock ls1, I should also mention it bent the connecting rod slightly, so Iím certainly leaning towards detonation. 14* at 11# is too much for 91 octane? The internet sucks, I sure see a lot of conflicting information and it makes it very hard to decide on who to believe. Iím trying to stay away from meth, I might buy a Garret intercooler to help.
Every one on the internet has hero times and cuts 1.2 sixty foots on bolton's. I usually shoot for 11 or 12 degrees at 12 psi on 93 octane. Haven't blown anything up and we beat on stuff. Your 150+ iats weren't helping. I start pulling timing over 120 degrees. I'm probably conservative to some, but my stuff doesn't blow up.
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Old 06-30-2018, 10:07 PM
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With only 91 octane, you would really benefit from water/meth. I run 18* @13-14 lbs on 93 with 50/50 water meth with no knock. This is on a gen 4 SBE. My compression is only 9.6 to1 though. I think your a full point higher .I’m able to do this because of the water lowering combustion temps. Also my IATs are low. 25* over ambient.
Buddy of mine has a 99 c5 with a vortech 15*@10lbs boost running 93 with an alky control 100% meth

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Old 06-30-2018, 10:57 PM
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Low timing and rich mixture melts pistons. Low timing builds heat in the cylinders. I run 19į timing and any lower than 11.7afr and I get a rich miss. What does the plug show? Excessively rich will burn between the rings, lift lands, and melt the heads, pistons and burn gaskets.
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Old 07-01-2018, 11:36 AM
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Iats a pretty high and 91 pump prob the issue. 93 pump and I run 16-17* at 10psi and spray 50/50 or wiper fluid and a FMIC.

Sounds like your intake cooling is not up to the task. My IATs are in the 90-115* range with 80+ outside temps before the meth even kicks on.
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Old 07-01-2018, 12:42 PM
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And when you're IATs are too high.....you end up with detonation or preignition.....that could have been prevented..... with a richer mixture or less less timing depending on if it was detonation or preignition.
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Old 07-01-2018, 01:03 PM
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Default High EGT = Piston Damage

Hi Loud Mouse, yes YOU are correct AND a measurement of EGT is easy.

NO AFTERCOOLER ???

This too ADDS EGT increases.

SURE detonation can be a result of a bad tune AND the added information provided by the OP points to that broken piston, NOT a MELTED piston. ( OP's Question)

BUT/INSTALL an EGT Gauge.

A HIGH EGT is a result of a too low Spark Instant.

WHAT is your EMAP at 11 .lbs ?

WHERE is your EGO/UEGO sensor located ?

MY tune target is from .866 -.902 Lambda AND finding the lowest EGT, found with CORRECT Spark Advance.

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Old 07-01-2018, 01:43 PM
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I didnít change my timing from 6# all the way up to 11#, so if itís because it was undertimed, why didnít it hurt anything when it was only on 6-8#? Plugs I canít tell, they are old. Will do some checking with a new set. I also believe it was from 91 and high iats, but here also , I literally have to pick who I believe and hope it works. 19* on pump gas 91 sounds a little silly unless itís kind 4# to me...
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Old 07-01-2018, 02:15 PM
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U running a intercooler setup?
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Old 07-01-2018, 03:28 PM
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Originally Posted by brandon6.0 View Post
U running a intercooler setup?
yes, cx racing but I have poor flow through it I think
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Old 07-01-2018, 04:18 PM
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+1 for ddnspider....
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