Blown Dyno Engines

[woollymoof]

I assume there are some of you out there that have blown engines on the dyno.

Under what circumstances has this happened?

- Holding the engine at 12500 RPM for an hour?
- Uneven charge distribution causing detonation?
- Internal mods gone wrong?
- Too much advance causing detonation?
- Etc?

[woollymoof]

I assume there are some of you out there that have blown engines on the dyno.

Under what circumstances has this happened?

- Holding the engine at 12500 RPM for an hour?
- Uneven charge distribution causing detonation?
- Internal mods gone wrong?
- Too much advance causing detonation?
- Etc?

[Marc Jaxa-Rozen]

Not on the dyno, but we had an exhaust valve go ballistic on our CBR's #2 piston while revving without load, a couple of weeks before Detroit...

http://www.overdrivegraphics.com/damage1.jpg

http://www.overdrivegraphics.com/damage2.jpg

http://www.overdrivegraphics.com/damage3.jpg

We didn't exactly have time for a full investigation but it looked like there just wasn't any coolant flow in the head- either a messed-up water pump or thermostat. While starting out we also had repeated backfires due to vacuum leaks, which probably didn't help the valve any.

Man I sometimes feel bad for those poor FSAE engines http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Igor]

Intake valve on an R6 broke in half at 15000rpm while that's below redline. Our electron microscope photo analysis of the fracture area showed that it was a production fault and we got a free new engine :-)

Igor

[Charlie]

We've had a few failures. One was a slipping adjustable cam gear on the exhaust side. make sure you have those things tight http://fsae.com/groupee_common/emoticons/icon_wink.gif I won't even use one on the exhaust cam anymore too risky. We've also locked up an engine with a seized rod bearing. I believe it happened because the pistons were hitting the cylinder head. Make sure you check more than just valve clearances. http://fsae.com/groupee_common/emoticons/icon_redface.gif

[woollymoof]

what do the other team members think of blown engines? Do they accept it, ie shit happens? Or, do they start a witch hunt?

[Denny Trimble]

As long as our guys investigate failures to learn the root cause, and admit to any mistakes they've made, we don't have any problems. It's a learning process. But, there have been a few "infallible" people with endless excuses who never owned up to their mistakes, and that builds animosity quickly.

[Charlie]

Hmm you would have to ask them. http://fsae.com/groupee_common/emoticons/icon_wink.gif I'm sure at times they've been pretty questionable about whether its worth doing the internal modification thing. Of course sometimes I have been as well.

We've always been very cautious about the engine we run at competition. In 2003 we changed to a stock F4i for Endurance because our 'race' engine was running roughly and compression was low. In 2004 our 'race' engine sat out because we didn't have much running time on it. Even though I gave it a clean bill of health, I knew our guys would not be comfortable with it and I didn't push the issue. It's only a couple HP. We did run an F4i that I had apart and replaced the transmission in and modified cam timing, but no other internal modifications.

[RagingGrandpa]

A few years ago our team was stratified into the vehicle/chassis guys and the engine guys, called 'DTC' - destroy the chassis. The internal competition may sound healthy, but really just made for alot of people who didn't like eachother. Didn't work out so well.

In the last two years we've all been friends again, and it's working increasingly well. Engine guys have done builds forgetting to install oil pickups (don't do that), badly aligned timing (or that), forgotten/improperly seated wrist pin clips (really sux), and after it's all fubar, you have to realize that the guys are now better for it and will do a more careful job than anyone else on your team next time . It costs money and will ruin a few days, but patience really works better than the blame game.

And I'm not convinced these engines lead a horrible life. Making sure there is always oil pressure and a working cooling system, as long as the engine was built correctly, our high compression 'race' engines last. Sure we spun a ton of bearings in earlier years, but that was while we knew oil pressure was dropping to 0 in fast sweepers. No suprise there.

$0.02

[woollymoof]

I'm just trying to get a feel for dyno's and engines and what can go wrong. There are some things that I am just uneasy with, particularly, how long would any of you feel comfortable holding an engine at say 12500-13000 RPM for mapping?
What happens when a rod launches through a block? Does hot aluminium and oil spray everywhere at sonic speeds? Do the engines stop immediately forcing anything they're attached to (dyno) to stop immediately as well?

[BryanH]

Hold?
I do all full load mapping by way of acceleration runs. Transient fuel + ign is very diff. to steady state. ideal situ is gear compensation for fuel on some engines. Calculate most used acc. rate then dyno at this rate.
Bryan Hester

[RagingGrandpa]

Well we start with steady state and then do pulls to get final power numbers to look at, but with steady state it's not uncommon to be holding the engine at RPM's above 10,000 in 500rpm increments for 20-30sec apiece. Like I said, if our motor is built properly, on the dyno with no sideload and excellent watercooling, it doesn't care.

And from our last explosion, I can tell you that supersonic chunks of aluminum was definately not the case. There was no loud bang when it went, we only noticed tons of water gushing everywhere. The engine kept running actually, sounded OK with 3 cylinders running and the 4th rod just swinging around. No abrupt siezure. The aluminum bits were tossed about the dyno cell, but weren't embedded in walls or anything. It's like a bullet without a gun barrel, the explosion has nothing to contain it so things don't get going that fast.

[woollymoof]

Halfast
When you start off with a new engine setup will you go straight to full load transient mapping with power runs? What if the engine runs horribly lean on the first run and destroys itself? I assume you set the map do a power run, set the map, do a power run etc etc.

[BryanH]

Kirk,I use a Dyno Dynamics chassis dyno.
Full load ign is set at least 5 degrees less than factory specs (or best guess!). I start by locking dyno at 1/2 max engine speed and having a look at full load A/F, and then altering all rpm maps from 50 to 100% to get 12:1 starting point.You only need to hold full load for <2sec. At this point I then take note of the power reading while holding full load for 2 sec, drop load and reduce overall timing by 2deg.,take another full load power reading which should be lower. If its not keep reducing timing until power does drop. Make sure water temp is approx the same at start of each test.
I set horizontal plot to rpm and r/h vert. plot to A/F 10:1 to 20:1. Set a reasonably fast acc rate. Start acc run at approx 40% max rpm and WATCH A/F ratio plot, If it starts to run up beyond 13.5, back out of the run, If the power curve drops off back out of the run. What happens next gets a little too complex to put into a post here, but I will add that multivalve engines designed for road use usually make best power around 13:1 right through the rpm range but some factory race engines will want to run much richer from their torque peak and beyond
Bryan Hester

[Trans Am]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by woollymoof:
I'm just trying to get a feel for dyno's and engines and what can go wrong. There are some things that I am just uneasy with, particularly, how long would any of you feel comfortable holding an engine at say 12500-13000 RPM for mapping?
What happens when a rod launches through a block? Does hot aluminium and oil spray everywhere at sonic speeds? Do the engines stop immediately forcing anything they're attached to (dyno) to stop immediately as well? <HR></BLOCKQUOTE>

As long as the engine has some load at that RPM I have no problem holding it there as long as I need to. If anything feels wrong I head back to idle. by feels wrong I mean too much power, to little power, incorrect sensor readings, etc. it's better to take a look at what's wrong first, before the failure occurs. This method saves alot of headaches.

In my 5semester with UW-Madison working on dyno testing there has been only a few incidents. All attributed to human mistakes in some type.

[ozzy]

Our engine guys recently melted out aluminium muffler. Noticed that it had started to get 'a bit' louder and shut it off. Went into the cell and found a molten pool of aluminium on the floor. The exhaust header temps were being logged at the time, and had peaked at 1200 degrees C http://fsae.com/groupee_common/emoticons/icon_eek.gif.

[Chris Davin]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by ozzy:
Our engine guys recently melted out aluminium muffler. Noticed that it had started to get 'a bit' louder and shut it off. Went into the cell and found a molten pool of aluminium on the floor. The exhaust header temps were being logged at the time, and had peaked at 1200 degrees C http://fsae.com/groupee_common/emoticons/icon_eek.gif. <HR></BLOCKQUOTE>

With EGT's that high, I'd be worried about melting more than the muffler! It might be time to do a "just in case" rebuild on that motor.