F4i Engine Failure

[schmason]

This is what happens when an F4i is held for too long at 14500 rpm. we (UWA) entered the meelup hill climb on sunday with our 2006 car and lunched the engine on the first timed run of the day.
http://i4.photobucket.com/albums/y119/schmason/Picture077.jpg
http://i4.photobucket.com/albums/y119/schmason/Picture079.jpg
http://i4.photobucket.com/albums/y119/schmason/Picture078.jpg

[schmason]

This is what happens when an F4i is held for too long at 14500 rpm. we (UWA) entered the meelup hill climb on sunday with our 2006 car and lunched the engine on the first timed run of the day.
http://i4.photobucket.com/albums/y119/schmason/Picture077.jpg
http://i4.photobucket.com/albums/y119/schmason/Picture079.jpg
http://i4.photobucket.com/albums/y119/schmason/Picture078.jpg

[Pete M]

Cool... Hey, if you don't blow up or otherwise damage an engine, you aren't trying hard enough.

By that measure, we were trying pretty hard a few days ago... We just don't need to ring the neck off ours to do it (turbos are awesome like that). http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Mike Claffey]

Thought I should add that it was second quickest in the practice session to cars that were built for this sort of thing and had enough gears for speeds above 130km/h.

[Brett Neale]

Heh nice work boys... Keep in mind the F4i's are out of production! There's one less engine in the field. That woulda made one hell of a noise...

[Pete M]

Ouch... so you were sitting on your (above stock?) rev limit in top gear for extended periods of time? Well, just subtract a few seconds from the period of time before failure and get the motec to drop your rev limit 1,000 rpm if you sit there for that long. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Erich Ohlde]

is it just me or did u have a little pre-ignition going on in that blown up cylinder?

[Poe]

pre-ignition doesn't break valves...

[VFR750R]

Appears to have broke the piston first...not real common. Usually valvetrain is the weakest link in the system, especailly when max RPM is being exceeded.

[Poe]

If that was the case then it could break valves. Is it odd, though, that the hole is in the middle of the piston from detonation?

Are the valve springs broken, or just out because there isn't any more seat pressure to hold the keepers?

[VFR750R]

My guess would be failed pin bosses, and/or wristpin clip coming out allowing pin to move over and fail pin boss still holding pin. After a few cycles like that, which with the piston being thrown up at TDC knocks valves off stems during overlap. The hole in the piston is from the small end of the rod once the pin came out.

[Pete M]

Nothing on that engine looks like detonation or pre-ignition related damage... The thing just bashed itself whilst moving at a few hundred strokes a second.

You can probably tell what happened to cylinder 2 by looking at the others. Cylinder 1 looks to have been bashing in the squish area, just not to the point of failure.

[Wesley]

I don't think the wrist-pin can back out within the bore - not enough room if I recall correctly. (which I may not)

It looks like you dropped a valve, and as it bounced around inside it smashed the rest of them up so they broke off as they tried to reseat, and got smashed into place by the approaching piston.

The amount of chipped up aluminum in the chamber suggest the valve head (probably the leftmost exhaust, by the looks of it) bounced around for a good bit before being lodged there.

It's hard to believe there wasn't any preignition though, but the piston crown is a really weird place for it to start. I would expect the valve relief eyebrows to be melted off first, not the rounded part of the piston. Though I guess if it was starting from the sparkplug (which is likely, it being steel) it would impact the piston crown first.

I think the valve head may have just punctured the crown and contacted the wrist pin enough to crack the shoulders for the pin bore, so it separated on the next induction stroke.

I don't know, but I think post-mortems are fun! Even though it means you blew up something expensive.

Don't know if we put up our post-california explosion pics, that was an impressive piece of work.

[Lexusteck]

Hey Erich, did you photograph the dyne motor failure this summer. Looks kind of familiar. http://fsae.com/groupee_common/emoticons/icon_frown.gif

[Bill Kunst]

Is it me, or does cylinder one have aluminum on the exhaust valves?

[Pete Marsh]

It is a bit hard to see from the pics but the rod and piston, indeed the entire reciprocating assembly is still fine. The reason the hole is in the middle of the piston is it is thick enough elsewhere to ram the valve down a port instead. The damadge to no.1 is due to ingesting bits of no.2 that were blown into the intake system. Same for the oil in the other cylinders.
14500 rpm is the stock bike rev limit but we do run less piston to valve clearence than the bike. The engine has done more than this before and was actually at 14300 rpm when it blew. It blew right on a large bump in the road and our feeling is the sudden MAP change from the throtle moving on the bump plus possibly some unfortunate timing of an extra vertical G or so took it over the edge.
There is no sign of detonation and the engine is not knock limited on 98 RON anyway, this is not a factor.

Pete.

[neil trama]

That was a valve failure probably caused by valve float.
The damage in adjacent cylinders is schrapnel from the second failure i.e. piston material.
Neil