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Blew it up today...


cygnusx1

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The NYZCC went out to run with the Porsche Club at Lime Rock Park today. I was pushing 18psi and running a tune that was somewhat un-tested over 6000rpms. Well, playing with the P cars, I had to reach into the 6k's a few times and eventually she popped. Flooded a cylinder or two with coolant. I got right off the track and rolled it to the paddock. Trailered it home. Time for a fixer upper. It was running so fast, handling great, all it needed was a fast driver....and a proper dyno tune. Ah well, what do you expect from a 160k+ mile junkyard motor running 18psi with a shady tune at the top.

 

 

 

 

 

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Sorry you blew it up, Dave. Tracking a car is a boatload of fun, but it will find the weak links right quick. I hope it's an easy fix.

 

Nice vid. LRP looks like a fun track. Lots of guardrail though!

 

jt

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JT - you are correct!

 

I tracked Joe's (RAGS) yellow turbo car and it taught me a few things for the day. Turbo cars are much harder to drive and 30-40 min sessions expose ever weak point in a cars build. It was still a fun day and glad the group of guys really enjoyed themselves.

 

Dave - are we talking full rebuild here? The car did look like it was running great for the day cause I couldn't find you all day! ;)

 

The July event will be fun!

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Yeah it was fun, one of the Porsche guys asked about the car because it was outrunning him on the straight. I waved most of them by because it was my first time in the solo run group and I didn't want to get in the way. I figures I could try to catch them or at least keep them in sight to learn their lines. Yeah Joe caught me with the LS1 Z, but he didn't pass me, so we could let some Porsches by. Then the motor popped and he went by me as I pulled over for pit lane.

 

Clive, I didn't see you all day! On a 1.5 mile track we must have been equally slow!

 

Motor is coming out and full rebuild will occur. Nothing fancy, just a clean stock rebuild, maybe a hotter turbo cam or a 280Z cam, turn the boost back to 16psi, and FINALLY get a real dyno tune.

 

 

I should also say that if you are using my tune, rest assured that it has survived and evolved fairly heavy street use for about 3 years. 30 minute track sessions do not compare to street use. The engine is used in a MUCH different way.

Edited by cygnusx1
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So I pulled off the top half of the motor today. #4 and #5 had some fire ring push out, and #4 had a shatter in the fire ring that exposed the nearby coolant passage. The head, block, and pistons look great so far. Tomorrow I'll pull out the lower end and take a closer look. I still can see crosshatch on all the cylinder walls. With a caliper I measure 3.387 +/-0.003 but I am getting a bore gauge tomorrow to check them all the way around.

 

What I found amazing was that the exhaust side of the turbo had about 3/8" radial play in it! The turbo was spooling fine and making its setpoint of 18psi with no strange sounds. So far the turbo looks fine and I already have a rebuild kit for it on the bench.

 

Plan:

 

-"A" N/A E31 Cam conversion, externally oiled

 

-Full bottom end rebuild with new OEM turbo pistons

 

-Rebuild turbo

 

-Dyno tune

 

-Maybe replace the 15 year old radiator, pro actively.

 

 

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Sorry to hear about that Dave..It sure brings back memories of my brand new engine going boom due to lack of oil pan baffles. Who woulda thunk an extra 12" of rear track would allow for higher G turns?!! I hope you get it sorted.

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Dave, if you haven't already thought about it, you might consider adding a knock sensor. I used the factory turbo sensor with this: KnockSense It comes with a red LED that lights when it detects knock. It also has an output for the ECU. I had initially tuned without the sensor listening for knock with my ears and taking a few more degrees out for safety. After adding the knocksense I found that there was still occasional detonation, especially in the 5k rpm range.

 

If you use MS2/extra, there is an option to retard spark when knock is detected and then return it when it stops. I figured it was cheap insurance, as well as another cool feature :) The knock retard can also be seen in the MLV logs so you can see exactly at what rpm, advance, and AFR the detonation occurs. It takes some more of the guessing out of tuning.

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Little by little I make headway. I finally got the motor on a stand and pulled the oil pan to the sound of clank, clink. Yep, #4 and #5 pistons decided to cross dress, so they removed their skirts. I suppose JB Weld is not the right solution here, so I guess I'm definitely buying pistons too. :mellow:

Edited by cygnusx1
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I've only been inside a few engines. But that doesn't look like factory honing crosshatch, does it? It looks more like someone honed a worn engine with one of those ball honers.

 

Just wondering. I thought that detonation led to broken ring lands and that broken skirts was more a fatigue/high rpm problem. Maybe your oval bores led to the piston skirt breakage.

 

Thanks for the pictures.

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