1.6 Crate Motor-Blown head gasket @10PSI? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-23-2008, 12:51 AM   #1
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Default 1.6 Crate Motor-Blown head gasket @10PSI?

Had my Greddy turbo w/ fully programable ECU on the Dyno today. Eddy Current type dyno. So held it at 3k, then 3500, then 4k rpm to dial in the EFR to 12.7. Temps are good, making about [email protected] 4k. Go up to 5500 RPM and can't get more than 4PSI. No knocking, temp rock stable (fan on huge radiator).
Trying to see why no real boost, so squeeze the hose to the wastegate and boost goes up to 10PSI, efr to 13, then shut it off to see why the wastegate must be openig to soon.

Let the whole thing sit for an hour to cool off so I can play with the actuator rod. It has no preload, so I adjust the rod in some. We fire it back up, bring it up to 5k rpm and we are making 5PSI, efr is 12.8, timing is 20 degrees. Starts to puff out the pcv vent, so we drop it to idle. It idles poorly. Shut it off and pull out the plugs. #4 plug has eroded its tip some and porcelain is pitting.
Leak test shows a blown head gasket. Water in the oil.
This was a brand new crate motor.
Any thoughts?
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Old 09-23-2008, 01:31 AM   #2
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#4 plug has eroded its tip some and porcelain is pitting.



uhh ohh. sounds like detonation to me, Imma say that you killed the rings on cylinder 4
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Old 09-23-2008, 01:38 AM   #3
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"timing is 20 degrees."

wtf????
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Old 09-23-2008, 02:17 AM   #4
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12.7, 12.8, 13 afr to lean.......
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Old 09-23-2008, 02:42 AM   #5
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20 degrees _AT 5500rpm_ (not idle) is reasonable if I understand this correctly. Check the MSPNP default map: 19* AT 5200rpm and 128kPa. Other than that, too lean for sure.
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Old 09-23-2008, 03:10 AM   #6
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Sucks to hear that man, was the motor properly broken in? And may i ask why you went with a crate motor?

A friend of mine lost the rings on his crate motor with only 20k miles on it. It was boosted with a good tune (Clint @ Gashead Motorworks, well known miata tuner in Houston) and was broken in very carefully NA. Idk, i just don't trust these crate motors, besides they are damn expensive.
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Old 09-23-2008, 09:21 AM   #7
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That is crazy.
I guess I would be swapping in a gasket, and inspecting the head to see if it was their fault.
The faster the better.
Good luck.

I know your sick!
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Old 09-23-2008, 10:17 AM   #8
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Thought my numbers were pretty safe, and never heard a single knock. Think the plug got damaged once the coolant got into the cylinder. Will be pulling the head today to see the total damage to the top end.
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Old 09-23-2008, 10:40 AM   #9
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Your probably doing this anyway. But if the plug had some porceline break off. check the walls for damage.
This happened to a chevy we had once. It scared the walls up, and fouled plugs.
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Old 09-23-2008, 03:58 PM   #10
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Luckily no porcelain broke off, but the prong on the plug was missing the last millimeter or 2. Let you all know what we find.
I am suspecting that the timing was more advanced than we think (static plus ECU MAP value) such that we thought the Cam sensor was installed @TDC, but may have been elsewhere. No one seems to remember who checked with a timing light when we first fired it up two weeks ago, so may have just detonated the poor thing to death and didn't hear the pinging over the racing exhaust.
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Old 09-23-2008, 08:35 PM   #11
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is this a mazda crate motor? is it equal to stock? what kind of compression ratio?
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Old 09-24-2008, 12:37 AM   #12
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Yes the crate motor is from Mazda and is stock compression. Pulled the head and luckily only some minor blow through of the head gasket between the cylinders and no head warpage or hard parts damaged. Definitely looks like we had some "extra" static timing on board which explains the entire Snafu.
Since I have the head off, considering advancing the exhaust cam timing a bit to decrease overlap when I button it back up.
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