Burnt valve at 20 psi?
 

So I was doing some pulls from 4-6k and all of a sudden I got a misfire and the car barely ran. Drove it to my destination and got it towed home. After cylinder 2 had 0 psi of compression I pulled the head after verifying timing was good and found this
https://cimg7.ibsrv.net/gimg/www.mia...c88f14a977.png
The valves were supertechs maevn ss valves. engine drove fine for 33k miles at 14-16psi but after 1k miles at 20psi I melted a valve from the looks of it.
Was this just me being ignorant using ss valves at that high of boost or could my ignition retard on decel be a culprit, or maybe too optimistic of ignition values in peak torque? The pistons have no signs of detonation. I know it cant be valve float due to the dual spring setup I have with the titanium retainers to pair.
Magically only the valve is damaged and the head is a little warpped I have overheated this engine pretty bad like 3 times so it could've been due to that. But the turbine of my EFR has no damage and neither does the cylinder wall or pistons. So I see this as a win given I was about to put the car away for winter anyways. What are your thoughts about this failure?

Check injectors while you have it torn down. A lean cylinder could do that. I'd actually think too retarded timing would be the culprit, not too advanced. Too retarded means high EGTs and can melt stuff. Too advanced is usually detonation and speckling on pistons.

What fuel are you running?

this exact thing happens too often on the n14 mini cooper engines, always because of carbon build up - direct injection, letting the valve get too entirely too hot for too long. Not to mention stock timing is pretty retarded in boost. Id assume a lean injector if nothing else, it obviously had too much heat somehow. Wouldnt hurt to get injectors flow tested.

running pump e80

pump e80, you might be right from 4500 rpm at 20psi I taper from 11* to 9 at redline

It is a self tune I made that I thought was conservative. Maybe too conservative. I also hope its not my injectors as i bought brand new idx1050s to compliment 20psi Should I upload a picture of the table for comparison?

attach your tune and a log and we can maybe help you, otherwise we're making guesses.

Running lean seems most likely to me, but I agree with curly that we'd need to see log & tune.

--Ian

This is the current tune and a log from doing some highway pulls and lower speed street driving. I can get the log from when the valve went but my car is sitting on my hoist at work rn and would have to grab that log tomorrow.
Had to zip the log file, it was auto logged by the ecu so its a bit long

I figure targeting .82 lambda is safe for higher boost. I also am taking out timing while vvt is advanced in that rev range, maybe I take out or lower the ignition trim on the 4d/vvt ig trim table? Again I have no professional experience with tuning so please critique away

Glancing at those logs two things jump out to me. You're hitting close to 90% duty cycle on your injectors at a few points. You're around 20 PSI at 0.849 (12.48 AFR). I'm cherry picking the worst case, but there are a few points throughout that log that are similar.

Second, and I'm confused by this more than anything, you're lambda goes to 10 on decel. Personally I would expect that to cap out around 1.3-1.4. Any chance your O2 gauge is not calibrated correctly or something?

Also, your voltage seems to be around 13.5 V at cruise and drops pretty consistently down to 13 V during pulls which could be messing with your injectors/coils if the voltage correction on those isn't dialed in.

As always, take it with a grain of salt, just point out things that jumped out to me.

The lambda value going to 10 on decel is a product of the link can module from what I can see. It calibrates itself everytime it warms up after starting from what i understand, and this only started happening after I was done going through 3 innovative lambda controllers and switching to the link can module. I am aware of the voltage drop, I am using a parts store alternator that has been covered in oil due to my boundary oil pumps inability to keep my front main from spinning (I'm going to try and hold it with retaining compound next time, during install I was able to snugly push said seal in without tapping it with a hammer, so I'll try to address that as well. I had a genreral understanding that 12.4 afr wasnt super lean but ill be more dilligent keeping it at low 12s. I got my injector voltage correction numbers from injector dynamics and the dwell table for my r8/gti coils was something I whipped up from some online research.

The high lambda values on decel is normal for some of the CAN based modules.

12.4 AFR is very lean on boost. Low to mid 11s would be more like it at your boost level.

Gotcha, my AEM gauge tops out around 18-20 AFR so I'm not used to seeing anything much over 1.4. I'm with redursidae on this one as well. I'd expect to see closer to mid 11s, which I believe is what your second lambda target table is close to (whichever one wasn't active during these pulls).

I'd probably point to a combination of what I mentioned before. Here's another point I randomly grabbed that shows a big voltage dip and the car going really lean as it gets into boost. You're also running 0.866 lambda around 240 KPA here, probably due to letting off the throttle a bit, but that's still 60% throttle and 240 KPA.

https://cimg4.ibsrv.net/gimg/www.mia...8451026329.png


I'm also curious that it looks like it was an intake valve that melted? I would've expected the exhaust valve, but I guess if the cylinder is leaning out any valve is fair game.

ETA - I'd be interested to see what the logs look like before and when the valve went.

In addition to all the tuning/software advice, have you checked valve lash? The time the valve spends closed against the seat is crucial to keeping the valves cool enough to live. Those VVT heads are solid lifter, so they do need to be clearance checked now and again, especially after a few thousand miles on a new valve job and new valves.

Apologies if this is redundant, but for anyone who finds this thread later on; valve clearance is meant to largely to allow the valve to expand during operation, and leave just a hair for an oil film, this is why exhaust valve lash is always larger than intake, the valves run hotter and expand more. Its possible that valve didn't expand enough at 14psi to get to negative lash (where the valve held open when it should be shut) but at 20psi, combustion temps increased enough that the valve expanded to the point that it doesn't contact the seat. That is ultimately what burns valves. Few years ago I got a Yamaha motorcycle real cheap bc someone didn't check valve lash for 38k miles (interval was ~15k?) and the valve looked exactly like that.

What's the lash on the rest of the exhaust valves measure out at?

I guess I never thought to check the lash, I already gave the head to my machinist so Ill ask him to get pre measurements before taking it apart.

It is the exhaust side that went, Maybe I need to add more grounds in my circuits because my head unit is reading 1v higher than the ecu usually. Currently without most of the harness plugged in I dont think my ecu is getting enough grounds for it to power on properly and grab the log. I also know my tps fuel enrichment might not have been on point as well as enrich on decel

The answer is not "more grounds", but one, solid, reliable ground.

--Ian

This. And double checking sensor negative wires are routed to sensor ground, not chassis/battery ground.

Might want to fix your ethanol mix as well. You currently have a linear line from 0% blend @ 0% E to 100% blend @ 100 %E. I'd expect you to need 100% of your "E85" tune at around 75-80% blend, with most of it necessary by E60. Try 80, 100, 100 in the last 3 cells of your multi fuel blend table.

Your boost control tables are also referencing boost pressure, which is weird. Typically this is TPS. As boost goes up, so does duty cycle, which makes boost go up...which makes duty go up...etc. You're getting wildly fluctuating boost as a result, which probably makes it difficult to tune. You could use this Y-axis to help regulate boost, like if it goes up too high, duty decreases, to help keep you at your target boost. But again that's not how it's set up currently.

I see quite a few lean spots in lower RPM, a lot of the fixes others have suggested and my own may help. You don't have CL lambda enabled above 13psi or 30% TPS, feel free to enable that up to ~28psi and 100%TPS, widebands don't care what throttle or boost you're at.

Finally the machine shop is working on the head. Interestingly enough only the intake valves on 2 and 3 were tuliped and had zero lash. The lash on the burnt up exhaust valves were fine, guides are a little out of spec so I'm getting the bronze ones from fab9. Interestingly enough he also said the valves were not stainless (magnet stuck to it) and that they were only 1mm oversized even though I know I ordered the 2mm stainless from fab 9 when I originaly put it together so idk what happened there. Going to richen up the tune under boost and wait for my inconel fm intake valves to come in. Curious if I somehow got bad valves or something because cylinders 1 and 4s lash were fine on the intake side and I have the supertech dual spring/ti hardware package and was only revving to 7.5k so I know float isnt an issue. So I guess all inconel valves, bronze guides for the exahust, and 1 valve seat aint the worst thing.