Brand new build, rear iron cracked during break-in. What happened!?
 

My freshly built engine cracked the rear iron during break-in. What happened?! S4 turbo block with S5 turbo rotating assembly. All used but VERY clean parts. Large street port, BNR stage 4 turbo, 4x ID1000s, MS2, etc, etc. Ran beautifully for ~4 days, put 100+ KMs on it. I added a bunch of fuel to the map (figuring it would be safer) and just started getting very slightly into some power/throttle. It went REALLY rich (maybe I should have left the map alone?), and the rear iron immediately cracked at the upper dowel. Luckily I happened to stop at a store soon after, and noticed a growing puddle of oil under the car. Still runs well but gushes out oil from under the filter pedestal between the rear housing and iron.

Any idea what could cause this? Boost controller was disabled. I was at under 10psi, under 6k RPM, maybe ~60% throttle.

2nd tow home with dead engines this year :(

https://cimg6.ibsrv.net/gimg/www.rx7...7ff054ec13.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...a886c39649.jpg
https://cimg8.ibsrv.net/gimg/www.rx7...6449271245.jpg

what pump are you running?

Sounds like detonation...did you verify timing?

If it wasn't too bad, you may only need a rear iron. But if it detonated real bad, you're most likely looking at a new rotor and iron (maybe housing and center iron too if it threw a apex seal)

Sorry to say it.

+1 what ECU are you running. timing really needs to be checked on all four wires, to verify the ecu is set right.

broken iron is kind of pointing toward the spark happening at a very wrong time, like 180, or 90 degrees off. its the only way to get enough force to break the engine like that, without adding dowel pins incorrectly

Without logs if someone were to tell me I'd let them know that A: they were making more than 10 psi - small dowel engines with knock events break dowel lands around the ~300 ft lbs mark in my experience, may vary for others. and B: breaking an engine in means no boost at all. Not because boost in and of itself is a death sentence or even bad for breaking in an engine, but you're in the exploratory phase of the rest of the engines systems and being in boost gives you less time to catch and fix a problem.

That said, get logs if you can, post em up. I'm sure there's more to the story that you may or may not know.

i just assumed he meant Megasquirt 2.

What ignition system, stock FC or four individual coils?

(This is important)

Yes Megasquirt 2 and all stock FC ignition system. The previous engine broke 5 of 6 apex seals simultaneously earlier this year (but took 7+ years of abuse before that). I have a feeling something has gone fucky with my ignition that has taken out 2 engines in a row.

I'm pretty sure this is the point where it broke: https://i.imgur.com/ohPOSGG.jpg

See the 'flutter' in RPM, that's when the motor bucked, it went super rich, and right before the oil trail on the road started

I totally forgot to double check ignition timing before starting to drive on the new engine. I went out the other night with a timing light and confirmed that I was about 6 degrees advanced. So in boost I was near 18-19 degrees instead of the 12-13 that was set in the map. Is that enough on its own to cause this?

There is a way the FC ignition can fail, whether internal to the trailing coil or a fault in the engine controller, where the "flop" transistor doesn't work and it fires the wrong trailing spark plug. This will cause engine-stopping detonation at part throttle on an N/A engine, in a turbo engine under boost it is deadly.

interesting. is there any way to test for that? should I just swap the coil to be safe? or just bite the bullet and go to independent coils...

Not zeroing out the timing on the MS2 after rebuild engine install would be a good candidate for a failure especially if the timing was advanced...... assuming that you don't have a mismatched crank pulley on the rebuild.

Another notable mention I ran across was this. From "Shainiac"
"I had a high-RPM/load misfire that cracked both front and rear irons when I was on MS2. I believe this was from having the spark plug wires zip tied together and getting a crossfire that fired 60* advanced.

Gleaseman had the same issue multiple times and I believe he had the same conclusion, also on MS2 I believe.

Are your plug wires touching at any point?"

I'm not saying the MS2 doesn't have ignition trigger issues (it does, and I wont touch them on boosted engines) - and all due respect to both Shainiac who's built a wicked car, and to Gleaseman who has actually built me a killer 3 rotor turbo manifold for a project - but those conclusions don't make any sense. Spark triggering from proximity to another wire has nothing to do with the brains behind whats commanding the coil to dwell and then collapse the field (fire). That said: the MS seems to have far too many faults in its ignition control makeup to warrant trying to pinch pennies by using one in this day and age. In my opinion and no disrespect to the OPs choices.

I'd also still like to point out again that on a 'break-in' that there shouldn't have been a condition that caused this failure anyway. This isn't to beat a dead horse but to make sure that folks that are building their own rigs don't think that 'break-in' means immediately boosting without doing THOROUGH checks on every system - including timing, oiling, fueling, etc. - Break-in at a mellow pace is what catches these faults even though an engines internals are capable.

Since you are a ecu / rotory expert, what are these megasquirt igition trigger issues exactly ? The stock 24/2 nippon-denso CAS on these are problematic on a few different ecu platforms and car models using them like supras, mr2's. I believe the original poster is using a 36-1 toothed wheel / hall sensor crank trigger.

Wires are definitely zip-tied together, you really think that could be it? I don't think that changed at all in the 6+ years with the last engine though. Something changed that has now eaten 2 motors in a row...

I had put probably ~120 kms on with no boost, and it really didn't seem like there was much to 'test' - the setup was pretty much identical to the previous engine, I just replaced broken parts with the same parts but not broken. nothing really changed, and it all worked before.

It was running great, making ~105-110 compression across all faces. Not a drop of oil/coolant/etc. I really saw no reason to continue babying it just for the sake of babying it.

And I like megasquirt! :P maybe it is time to look at other options though...

Yes, the full function engineering 36-1 wheel and hall sensor, I should have mentioned that

I'm no expert ....I'm a guy like you trying to piece info that is plausible and maybe help out. Personally I wouldn't take a chance on inductive cross-fire and separate or cross ignition wires at a 90 deg. angle. A couple of other things I would do is reload the firmware and tune back into the MS and eliminate the possibility of firmware corruption. Which firmware are you using, the latest 3.4.4? As Dguy mentioned if there was a code break in the firmware and trailing wasn't toggling at the right time in FC igition mode....that would be bad thing. I would also go to the megasquirt site and make a post so the developers could verify the rotory code.

you should for sure re route the wires. they may have been fine when they were new(er), but maybe not now.

the google search term is "inductive cross fire" you either want the wires to be separate, or they should all cross at 90 degree angles. interestingly the stock T2 setup crosses the wires, the FD has them all separate

sorry never answered this. pump as in fuel pump? it's an AEM 340

Sure, but again you're calling it break-in and timing lockout would be one of the post break-in 'boost prep' procedures. Just calling a spade a spade, hope you get it figured out!

no worries. yeah, i meant fuel pump. i saw your injectors and was wondering if your detonation was due to running out of pump, but it seems like your timing was the issue.

i just want to see you figure it out and get your car running well.

Can confirm, this has happened to me.

Didn't realize it until it killed a *second* engine.

So is it an ECU issue or a fault in the coil itself? Do I just need to replace the coil?

This issue probably did kill 2 engines on me as well - one broke 5 apex seals back in April and this one broke the rear iron recently.

I was running an MS2 as well.

I gave up after the second engine failure and bought an R32 GT-R, and that was in 2009... I figured out the coil problem when I took the coil off of that car to fix another car that wouldn't run. My FC has been sitting ever since.

Mine did sound suspiciously like yours - first engine lost compression on one rotor and then lost it on the other rotor while limping it home, had zero compression on either rotor. Second engine cracked housing.

I don't know if I can say for sure that the issue was the bad coil or that the megasquirt killed the coil or what.

Wow, almost exactly the same, except I lost both rotors at once on the first engine. Ugh, sucks not knowing the cause for sure.