Xu10J4 Goes Bang

[petert 586]

Whilst I was away last weekend, my son raced at Wakefield. He reports the car had been off song all day, culminating with zero oil pressure in the last race of the day. You can see in the data (oil pressure vrs RPM) he looses oil pressure in Turn 10, then it returns (about 10 psi less) two gear changes later down the main straight. Unfortunately the damage was done and it is no more.

 

The culprit turns out to be the long oil return pipe. It fatigued around the small hole, broke off completely, then floated around in the sump. It probably jammed shut one of the trap doors in the sump, starving the pickup of oil. You can see how long the accumulator lasted (not very long).

 

Unfortunately I forgot to turn on "Engine Protection" in the software, which would have minimised the damage. The nitrided crank is toast, as are three conrods. I haven't stripped the head yet, but valves have touched pistons on two of the three damaged rods. I fear the worst there.

 

After nine years of racing it's been an ultra reliable engine, but I never would have seen the broken tube coming. Be it a warning for all. They must vibrate like crazy at 8000rpm. Best to cut them off. That's the end of wet sump racing for me. Next engine will be dry sumped.

[JeffR 51]

Sorry to hear about the failure Peter, and as said you wouldn't factor pipe fatigue in to cause such damage. Were they your forged rods too?

 

I have a spare J4RS crank if needed.

[petert 586]

Yes, goodbye Wossner rods. Luckily I have plenty of cranks.

[wicked 103 3 Cars]

Wow.. that's bad luck; you do everything to overcome the oil issues and then the stupid pipe breaks...

 

Will the new engine be the same spec, but dry sumped, or are you take it to the next level (if possible?)

Edited July 10, 2015 by wicked

[Anthony 1,003]

That's pretty bad luck.

 

I'm almost surprised that the resulting damage wasn't worse, as if I'm reading that graph correctly, that's nearly 10 seconds with zero oil pressure whilst at high revs! Guess your son didn't see the oil pressure light in the heat of the moment?

 

Still, nine years is a pretty good innings and hopefully the damage aside from the rods and crank won't be too bad so that the majority of the engine can live on in the next incarnation

[petert 586]

I'm amazed he didn't see the row(s) of red LED's. He claims it happened on the entry and he was committed. Yes, it's 10 seconds. The shape of the oil supply data is not consistent with previous data suggesting it was starving prior to the corner. The next engine will be basically the same. Maybe a bit more rev range. I'll see what happens when I strip the head. Ideally it needs to be around 190-200hp at the wheels. In the meantime, I'm dry sumping an otherwise std XU10J4 for the final round.

[rallyeash 155]

To be honest out on track I completely forget about the dash board sometimes!

[petert 586]

Bad news from the engine reconditioner this week. I was hoping to re-use the pistons in another block. Unfortunately one of the pistons has collapsed, probably from detonation. You can't see it with a naked eye, but it's now 2.5 thou undersize. The crew thought it sounded a bit lean, so they richened the top end slightly, which improved things. Unfortunately the damage had already been done.

[petert 586]

More bad news. I finally got around to stripping the head yesterday. Five broken valve springs, a combination of inner and outer, all on the inlets. No wonder my son said is "down on power".

Edited November 12, 2015 by petert

[aldworth33 45 1 Cars]

Nasty, never seen valve springs break