Thrown Rod at Daytona

[jgparker]

Well, after 5 years, and 30 plus racing weekends, my 2.8 let go at the PCA club race this weekend at Daytona. Some of you may remember my build documented here based on the pre-release version of Wayne's book in 2003.

Clearly a thrown rod on #3. Looks like the rod bolts let go. The mistake I probably made was using stock rod bolts and stock rods on a engine I was running up to 7500 RPM. Anyway, let me know if you all are interested in me documenting the dissection and rebuild as it progresses.

Thanks,

JP
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[Jerry1]

Yes Post progress, sorry to hear about the motor

[kilodawg]

Gee Jonathan I'd like to come by and watch when you get started....

[cgarr]

So what happened to the car behind you?

[Grady Clay]

JP,

Yes, we all should be interested in the diagnosis.

Not exceeding 7500, the engine should last decades with your use. I suspect you may find an oiling issue and not a random bolt or rod failure. What is the condition of the big-end rod bearing? Other bearings? Signs of detonation?

Best,
Grady

[jgparker]

Hey Kilodawg, I can always use an extra set of hands. I'll let you know when I'm ready to start the tear down. Let's talk at the Panamera launch at POM on Wednesday.

Hi cgarr, fortunately no one was behind me. Good puff of smoke, but no real oil loss, which is good, because it was right at the kink. I'll post the video shortly.

Grady, I would have assumed that stock rods and bolts were OK at 7500, but Dayton, I'm at 7500 for a looooog time, and who knows, maybe I down-shifted to early a couple of times. Hopefully it will be obvious when I pull it apart. I haven't seen the big end bearing yet, so I can't speculate on an oiling issue. Oil pressure was OK up to that point.

So, I have to ask, how could detonation cause rod bolt failure?

Thanks,

JP

[jgparker]

Here is the final lap. May be some clues in the audio. Power was a little low the last time past start/finish. Seemed to start going bad at turn 1, and was gone before the kink.

[davidppp]

Good post.

I'll take $100 on lube failure.


Kind regards
David

[billybek]

That motor didn't seem to protest too much before it just quit....
It looks like you had some pretty fast company out there.
Subscribed...

[lucittm]

Magnesium case?

Just curious.

Mark

[Walt Fricke]

A race mechanic once told me the rod bearing progression is: some loss of power, followed by an increase in oil temperature, followed by BANG. Sounds reasonable: bearing starts failing, more internal friction = loss of some power. More friction = more heat in the oil. And, of course, the BANG is self explanatory as the extra heat and friction get to be too much for the rod bolts.

Of course, the trick is to recognize "some" loss of power. Or at least catch it at the rising oil temp phase. I've never been able to do either.

A friend had Carillos lose a bearing (a bit of O ring in the crank oiling passage). Things got so hot that when he shut off the motor, it could not be turned over again. The rod big end was all blue. But it didn't break. There is a loss of power for you.

Walt Fricke

[MBEngineering]

HI Walt Fricke
a rod a bit like this??



this had oil feed in to the engine prob's.

regards mike

[T77911S]

i dont know if it was just the VD, but there is a strange sound just after you passed the exit to pit lane

sorry about the loss. but i did enjoy the VD.

any other good incar vd's out there?

[racing97]

Characteristically if a person where to shift just a little before he brakes a Daytona into turn one, especially one, but really any other turn as well he would be using the engine as a brake commonly referred to as "back holeing". The boxer style motor is very vunerable to this situation. Carrillo rods Tia rods all help the situation as well as more bearing clearance but will not prevent it totally as a Carrillo rod and a Porscche rod are essentially made of 4340and the Carrillo is a little more refined utilizing a SPS bolt which is in mass more robust. the Tia rods probably eleminate the issue as they sling a signifficantly reduced mass over TDC during the exhaust stroke with no load on the piston, which is essentially what kills the rod bolts and even a Carrillo won't take the deformation of the big end unless there is more bearing clearance built in to the package.

regards

[Steve@Rennsport]

I saw a lot of "using the engine" to slow the car instead of using the brakes, and that puts very large tensile stresses on the rods and bolts. Long term deformation of the big ends and bolts will trigger a failure and its exacerbated by the heavy OEM rods.

While using better rods (Pauter, Carrillo, Arrow, Pankl: 4340 or Titanium, etc) will certainly make a big difference in durability, none of these are totally bulletproof when the engine is operated in such a fashion,...

JMHO, we don't recommend using stock rods when expected peak RPM's will be over 7300 due to excessive bearing loads.

I'd be curious about how many hours on the engine before this happened.

[BReyes]

Sorry to hear that. Appreciate your sharing the causes/ refurb again. Your 03 build was couple years before my first in 05.

Seen a 911 turbo that threw a rod at Daytona, and this same cause cited. Seems like over revs mentioned is issue, and very interested in learning if it was an oil starvation issue.

Must be awesome to run at 7500 ( much of banking and down the front straight)? What about the gearing on your car? Is it the same gear set you run at Sebring?

Regards,

[jgparker]

Hi all,

The engine probably had about 50 hours of track time.

Steve, You're right, I've always been engine breaking, but I'm also been giving it everything I can from the stock S brakes. One of the groups I run with limit me to stock brakes, which are not great. If I shouldn't be engine braking into the brake zone, I'll stop. It's a lot of work and seems to bias the brakes to far back anyway. Also, if I should reduce it to 7200, that's easy. Live and learn.

I plan to pull it apart this weekend. I'll post the pictures as I go. Hopefully we'll find something useful. Want to help kilodawg?

Thanks,

JP
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[ninesixfour]

Holy closing speeds! Subscribed.

[jgparker]

Hi All,

OK, I cracked the case today, and have some very interesting clues, but no smoking gun. I have about 80 pics, but I'll only post the most relevant ones. First, The shaft to the oil pump was sheared. Did this happen post rod-throw or was it the cause?



Second, one of the rod blot nut was unscrewed, not sheared or stripped. Did it unscrew first, or after the bearing failed and the big end overheated?



the rod bearing was gone, ground to smithereens. The bearing surfaces were heated, but all the other bearing looked OK.



and from the rod cap, it's clear one bolt let go before the other.



From my uneducated view, I would think the rod bolt stretched or the nut started to come loose, and everything else followed. I did use red lock tight and a calibrated torque wrench.

More pictures are here:

Photo Album 2009I

Any Opinions?

Thanks,

JP
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[cgarr]

What oil temps did you normally run? Did you notice anything prior like oil pressure or temp change?