1266 replies to this topic

[Doctor Ed]

Agreed, but you don't know if the engine failed at peak output. It's certainly looks like a common lspi failure

Vocky's implication is the failure is peak hp related, and has labeled the pistons 350hp limited.

[fezzasus]

Agreed, but you don't know if the engine failed at peak output. It's certainly looks like a common lspi failure

Vocky's implication is the failure is peak hp related, and has labeled the pistons 350hp limited.

Very strange failure in that case. I would expect thermal fatigue which wouldn't originate from the ring pack

[BadCop]

Link to your "A20NFT" build vocky? There is more than one strange thing...

[vocky]

just google LNF piston failure, plenty to keep you busy

[fezzasus]

FYI. There are two engines being used as benchmarks for severe LSPI engines; the Ford 2.0 Ecoboot and the GM LNF. LSPI is considered to be caused by ejection of fuel/oil mixture from the top ring crevice into the combustion chamber and as a result, the pre ignition event tends to occur from above the ring zone leading to failures like those. This has been tested with chamfered edge pistons which show negligible LSPI events in comparison.

 

I'm certain these failures are caused by LSPI. Failures due to high thermal load don't originate from the ring pack. Running an all magesnium containing oil (no calcium) will help mitigate against LSPI, as will running high EGR and running the engine rich.

[vocky]

Could it also be the mapping above 350bhp which makes LSPI more likely ?

 

 

[fezzasus]

Could it also be the mapping above 350bhp which makes LSPI more likely ?

 

 

 

 

In short, yes. If it extends the low RPM, high BMEP region. I suspect there's more temptation to use this area when the car has more power as there's less reason to downshift. Ford have developed a shift algorithm to drop down a gear in their automatic boxes when LSPI is detected, however it's so much more powerful that knock (and earlier, often before TDC) that you can still get significant damage.

 

Biggest recommendation I can make is to use a Dexos1; 2015 lubricant, they're the only oil on the market with LSPI testing (in the LNF) at the moment. When API SP/GF-6 comes out, that will have another (but milder) LSPI test. Nothing else does and typical oils are very prone to it.

[BadCop]

LNF?? Has nothing to do with A20NFT.

[Doctor Ed]

So vocky... What you've posted is an LNF piston (A20NHH or similar)? Explains why it looks different to the LDU (A20NFT) pistons I've seen. Feel free to correct me, but I think the LNF pistons et.al. are just regular cast, and the LDU is a hypereutectic (semi forged) piston. LDU / A20NFT pistons look decidedly different

[BadCop]

I have never seen a A20NFT (LHU) Piston fail even over 400 bhp in race condition. 8 out of 10 cars finished 24h Nordschleife with Stock A20NFT engine. None of those Z22SE or Z20 engines would survive 24h full throttle at 400 bhp - not even with uprated internals The piston vocky posted is the Opel GT / Insignia LNF engine - which is crap. And has nothing to do with A20NFT.

Edited by BadCop, 14 August 2016 - 12:09 PM.

[vocky]

So vocky... What you've posted is an LNF piston (A20NHH or similar)? Explains why it looks different to the LDU (A20NFT) pistons I've seen.

Feel free to correct me, but I think the LNF pistons et.al. are just regular cast, and the LDU is a hypereutectic (semi forged) piston. LDU / A20NFT pistons look decidedly different

 

 

I have never seen a A20NFT (LHU) Piston fail even over 400 bhp in race condition.

8 out of 10 cars finished 24h Nordschleife with Stock A20NFT engine.

None of those Z22SE or Z20 engines would survive 24h full throttle at 400 bhp - not even with uprated internals

The piston vocky posted is the Opel GT / Insignia LNF engine - which is crap.

And has nothing to do with A20NFT.

It has become quite clear to me that you both have not got a clue

 

Here is the engine code from the Astra J VXR engine, which the damaged piston came out of, quite clearly an A20NFT

 

I wil leave your thread alone from now on

 

[BadCop]

No it isn't. The numbers on the inside of the piston you posted is a A20NHH one. Not a forged A20NFT one. And I think you know it - as you were talking about a LNF yourself

Edited by BadCop, 14 August 2016 - 01:57 PM.

[Doctor Ed]

How do I not have a clue?? You're just some guy on the internet I've never met, photo bombing a thread with limited/no supporting info. If you have a point to make, involve yourself in a bit of discussion, establish and validate your point with atleast a bit of info. I think I'm allowed to pose a few objective questions within the limits of the paucity of info you've provided There's 100 reasons to fcuk a piston, and that is an oddly fcuked piston. More to the pint, It' looks different to the A20NFT pistons I've seen, and your referring back to the LNF is just muddying your point further. You come out of the box and say it's a hp related failure like they're some glass ceiling. If it's a case of lspi, then it's relationship to peak hp is tenuous, and if it's a peak hp related failure then it's a freaky looking break, and deserves s bit of explaining. If you're not interested in actually discussing things, what's the point of bringing it up?

[Doctor Ed]

And fwiw i do realise I've written LDU instead of LHU, but stupid edit-lockout prevented me going back and correcting it.

[Doctor Ed]

I have never seen a A20NFT (LHU) Piston fail even over 400 bhp in race condition. 8 out of 10 cars finished 24h Nordschleife with Stock A20NFT engine.

To be fair, I doubt cars in the 24hr are running around at low rpm/high bmep cruise, pinging their tits off with lspi. It's an interesting conundrum the lspi thing throws into the mix, and even oems are really struggling. Certainly makes things you take for granted on modern pfi engines suddenly seem rather important again. For eg I was in 2 minds how I was going to set up my pcv breather system, but PI makes it a no brainer to port. That, and the 5000km oil change is back. Takes me back to the old days when I'd take my first car (carby with mech ign advance) around the back of the local football field carpark, and pour a bottle of redex straight into the intake to 'de-knock' it. Lol. Pity vocky has deleted his pic of the failure.

[Doctor Ed]

Agh, edit-lockout again... ...seems I deleted a bit I wrote about tune that I didn't mean to... Normal pfi tuning would tend to call tuning rich on full noise 'safe' from a combustion perspective, but has a tendency to carbonise the piston crowns. I wonder if that's a contributing issue to some tuned motors... Ie running them rich up the top, getting things carbonised, and contributing to lspi down low. Vockys piston for eg was well and truly carbonised as if the tune was quite rich. Pity vocky has deleted his pic of the failure

[fezzasus]

I have never seen a A20NFT (LHU) Piston fail even over 400 bhp in race condition. 8 out of 10 cars finished 24h Nordschleife with Stock A20NFT engine.

To be fair, I doubt cars in the 24hr are running around at low rpm/high bmep cruise, pinging their tits off with lspi. It's an interesting conundrum the lspi thing throws into the mix, and even oems are really struggling. Certainly makes things you take for granted on modern pfi engines suddenly seem rather important again. For eg I was in 2 minds how I was going to set up my pcv breather system, but PI makes it a no brainer to port. That, and the 5000km oil change is back. Takes me back to the old days when I'd take my first car (carby with mech ign advance) around the back of the local football field carpark, and pour a bottle of redex straight into the intake to 'de-knock' it. Lol. Pity vocky has deleted his pic of the failure.

Haven't seen much indication that LSPI will reduce ODI from any of our, industry testing or oem discussions. Adoption of RDR may stall increasing ODIs though

Edited by fezzasus, 14 August 2016 - 08:49 PM.

[Doctor Ed]

Dodgy Bros rivnut tool. Bangs in M6 steel nutserts with breaking a sweat. Reloads are a little tedious, but it's tolerable doing half a dozen at a time.



Anyway, banged in a few of them between renovating stairs and picking up the kids, and got the surge tank and filter/reg kinda sorted out. It's all pretty tight, so tough getting the hoses flowing nicely. Fortunately the 200 nylon hose turns a pretty nice radius. Also, it seems I need a 45 -6 for the reg output hose. No biggie, and nice to see it'll all more or less line up how I'd imagined.

[fezzasus]

Why not use two 90 degree fittings rather than bend the hose?

[Exmantaa]

Should that surge tank/pump not be mounted vertical?