Who can tell me...

[Silver Fox 43]

What's caused the pitting on the side of this piston.

All 6 pistons have the same markings just on the top section between the crown and the first compression ring, no pitting on the crown of the piston, or the head chambers. Also no markings on the spark plugs or the head gasket, and the compression rings are bound in the groove by small shards of aluminium, therefore I had no compression and no engine running.

Caused me to change my engine on Friday afternoon for an early Saturday start at the track, turned the key and had it running again with the old engine around midnight.

[BM WORLD 1285]

is that caused be detonation (pinking) ??? guess

[Silver Fox 43]

Seems to be the general consensus, but why none on the crown or plugs, they're the normal place?

[Silver Fox 43]

Guess I should elaborate a bit.

Put the new motor in last weekend and took it to the dyno on Wednesday. Had a full remap and didn't miss a beat, so went down to Hampton Downs early Friday morn for some fun. First lap just after the biigggg sweeper it started blowing huge clouds of oil smoke out the exhaust, so by the time I notced it, the engine had started missing and farting and I pulled over and got towed back to the pits. Didn't even complete the first lap.

Got home and took it apart yesterday and found cup fulls of oil all thru the breathers and intake manifold, the E28 has small return holes in the head, and the centrifugal forces kept the oil in the head up against the breather outlet. When I started using the throttle in the sweeper it caused maximum vacuum and sucked all the oil thru the intake.

Lesson is, if you have a race engine with the same configuration, use a catch tank from the top breather and send the oil back to the sump via the dipstick hole, and block the breather hole in the intake side.

But why is the detonation on the side of the piston?

Edited January 19, 2010 by Silver Fox

[3series 0]

speaking from a guy that knows bugger all about reconditioning engines: did you give it plenty of km's running it in before taking it on the track?

Edited January 19, 2010 by bmw3

[Silver Fox 43]

Nothing to do with running it in Andy, solely due to the sweeper at Hampton, I believe somewhere around 15 cars have done their motors on that corner so far.

[CamB 48]

Detonation affects the side doesn't it - its the part of the piston under lateral load? Either way, looks like a less severe version than this (picture #1)?

http://www.mr2.net/d796env_pistondamage.html

Did it go lean???

[Silver Fox 43]

Just had a thought, so don't laugh.

Is it likely that the volume of oil in the cylinder was protecting the top surfaces and the only place the detonation could arc was on that skirt surface, does that make sense?

The detonation was caused by the high compression due to all the oil in the chambers by the way.

[Silver Fox 43]

Thanks Cam, I have none of the marks in the ring groove, and am in the process of cleaning and reassembling at the moment. Am able to reuse everything at this stage thankfully.

[BM WORLD 1285]

i have had both my m5 engines go at that track (head gasgets), also on a remapped ecu , i wonder if that big uphill climb is quite a load on the engine running at max revs for a long time under load . extra hot , running lean etc .

but they where old engines with possibly the original 25year old head gasgets . but i think this track is a lot harder on the engines due to the hills etc

Edited January 19, 2010 by Brent HARTGE535i

[*Glenn* 855]

I'll see what Ewan @ Engine Rebuilders & Lynn Rogers have to say today Dave. I'll email the pictures. Have you got one of the top of a piston & combustion chamber as well ? The piston you showed me on Monday had absolutely no damage on the top at all from what I could see.

Edited January 19, 2010 by *Glenn*

[*Glenn* 855]

Lesson is, if you have a race engine with the same configuration, use a catch tank from the top breather and send the oil back to the sump via the dipstick hole, and block the breather hole in the intake side.

Don't run a sealed catch can though Dave. It must breath... either to the original breather hose fitting or fit a small breather filter on the top of the catch can, or you will end up pressurising the sump.

[Jamez 2147483647]

Nothing to do with running it in Andy, solely due to the sweeper at Hampton, I believe somewhere around 15 cars have done their motors on that corner so far.

Everytime I have taken my 325i round it lacks power on the sweeper then smokes the hole way up the straight but the 333i with the S50 and standard E34 sump setup has had no problems at all.

Good luck with finding the problem and solution.

[*Glenn* 855]

Everytime I have taken my 325i round it lacks power on the sweeper then smokes the hole way up the straight but the 333i with the S50 and standard E34 sump setup has had no problems at all.

Good luck with finding the problem and solution.

E30's could also suffer from this problem as well, as basically its the same as Daves