Ideas as to what happened?

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Oct 19, 2005 | 10:54 AM

BLWNZ

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Ideas as to what happened?

These pistons are out of a buddys VR6 turbo. the car has Ross pistons and cunningham rods. This is the second piston that the edge is burnt and pitted . He runs 28lb of boost and 18 degrees of timing and the car is 9.1 comp. This happened a year ago at less boost but the same cylinder. Also the plugs in these cylinders look great with no signs of detonation.

Oct 19, 2005 | 11:16 AM

Zombie

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the ross pistons in my 89 supra looked the same after running it hard. We suspect that I was detonating it lightly for a long period of time and it just got hot.

Oct 19, 2005 | 11:30 AM

BLWNZ

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Did the plugs look ok becouse these were perfect maybe a little rich if anything.

Oct 19, 2005 | 01:09 PM

hellbents10

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To rich fuel igniting around the ring lands.

Oct 19, 2005 | 01:16 PM

V6 Bird

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Quote:

Originally Posted by hellbents10

To rich fuel igniting around the ring lands.

I was going to say something similar but the the extent of too tight of ring gap on the top and 2nd rings.

Mike

Oct 19, 2005 | 07:47 PM

SleeperSupra

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I would invest in a wideband.

Oct 19, 2005 | 08:04 PM

LASTLS1

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Too lean! Cylinder temps too high.

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Oct 19, 2005 | 09:17 PM

SleeperSupra

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It ran lean. You can see the damage from it detonating around the top edge of the piston and the damage from the heat around the ring land. An air/fuel ratio of 12.0 is kind of pushing it. I like to stay safe around 11.6-11.8 to 1. Timing makes power not running on the ragged edge of being lean.

Oct 19, 2005 | 09:28 PM

#10

SleeperSupra

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Kind of like this...

Ran it lean and the plugs looked perfect.

Attached Thumbnails

Oct 20, 2005 | 07:42 AM

#11

V6 Bird

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Quote:

Originally Posted by BLWNZ

Did the plugs look ok becouse these were perfect maybe a little rich if anything.

Have you cleaned that piston at all or is that how it came out of the motor?

If you havent cleaned it, then it was running lean. Ive never ran a turbo car anywhere close to 12:1 much less a nitrous car. With that kind of boost psi you generate alot of cylinder heat from cylinder pressure. Extra fueling to the tune, woudl actually make more power too. Keeping the egt's down and allowing for a cooler charge to ignite and make power with.

Mike