Anyone else ever BREAK a valve???

[Catbox_95]

I've gotta say, this is a first. When an engine loses compression, a few things come to mind but never this! Anyone else ever have this happen? Oh yeah, and I really like the way they built a turbo engine with valves that have raised numbers stamped on them, perfect for creating detonation!

 

[el aguila]

Yes it's happened.

Watch your EGT's to avoid things like this. I'm willing to bet you were WOT when this happened.

 

[psychlow]

That is a burned valve. The point of failure is usually the hottest point, so it likely wasn't the letters that caused the damage.

 

[Defiant]

^ ^ ^ That's burned. These are broken, and what happens. Interesting that they're all #4

 

[Defiant]

Oh, and numbers have been forged onto valve faces since the poppet valve was made viable. It's not a source of hotspots.

 

[el aguila]

It's not a source of hotspots.

He's right. Now had there been an extreme amount of carbon there, that could cause pre-ignition or detonation.

 

[TSIfreek]

I agree on a burnt valve from not enough fuel and to much boost. You can see how the bottom of the valve is eroded from the extreme heat. The end burned off becuse its the thinist part of the valve and will get the hotest.
You see this all the time in race motors. You are lucky you shut it down before it burned completly thew and started melting the valve stem. Valve breakage happens after that from the valve not being able to withstand the spring seat pressure and just breaks off and by by head.

 

[Catbox_95]

Yeah, what you guys said makes a lot of sense. I did shut it down right away to avoid more damage, good thing. I've heard that an air/fuel gauge is more important than an EGT gauge. Is this true? It would seem to me that it is true, since EGT is a delayed result of air/fuel ratio, which is monitored immediately.

Yes, I was at WOT, 15 psi, and a little lean (I have an air/fuel gauge, just need to pay closer attention to it!)

 

[psychlow]

Normal A/F gauges are not good monitoring devices for tuning, unfortunately. They don't have fine enough resolution, so the difference between a tuned engine and a dead one can still show the same reading.

If you want a good A/F gauge, you'll need a wideband.

 

[Catbox_95]

Is there a less expensive way to tune A/F ratio without going with a wideband? How do you guys tune?

 

[psychlow]

Eventually, I plan on getting a wideband, but until then, I tune by way of a logger combined with more old school ways (a vacuum gauge, reading plugs, etc).

The logger lets you check for things like knock and monitor fuel trims and oxygen sensor data, while reading the plugs will tell you if you're running too hot. If you look in a Chiltons or Haynes manual, there's usually a plug reading section in the very back of it.

I tend to start off with a very safe tune, then lean it until I get 1-3 counts of knock; then I back it down for a safety net.

You can also get a good idea how well you're tuned at part and mid throttle by the amount of vacuum you have.

 

[killab443]

ive broken a valve straight off in my 6 bolt that jumped like 4-5 teeth.
http://dsmtuners.com/forums/showthread.php?t=106696