Ok, thanks. Yes, all worked fine with the old pistons and 380hp, but my power target is now 500+hp so I want to play safe. But one new problem had appeard. The piston wrist pins seems to be quite loose on the "new pistons", they fall out by it's own weight. Is that a problem?
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Those woodpecker pistons are not good.
Those sharp edges can create hotspots and reduce knock threshold, costing you power.
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Ok, we decide not to use the new pistons either. ... Luckily my friend had a set of stock pistons lieing alround so we maybe use them, I hope. There is a markin on the pistons that is different from the old ones. My stock AAN- and the cleaned pistons has a markin like this + 05.12 and the third set has this - 05.10. The size is the same on all 80,98.
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So, anyone know something about the markings on the stock pistons? What does this stand for?
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Originally posted by Thuppu View PostOk, we decide not to use the new pistons either. ... Luckily my friend had a set of stock pistons lieing alround so we maybe use them, I hope. There is a markin on the pistons that is different from the old ones. My stock AAN- and the cleaned pistons has a markin like this + 05.12 and the third set has this - 05.10. The size is the same on all 80,98.
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The block/bottom end is now almost done. Need only to find seals for the turbo oil feed and return...
The rod bearing clearence's was all good, between 0.038-0.050.
Also the piston rings was good, all between 0.3-0.4mm, no need to adjust.
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I got the head yesturday. Only one small crack in 2:nd cyl, from ex-seat to sparkplug hole. No problem with that.
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The stock pistons is good for 600+hp. Of course the first weak point is the rods, 400hp/500Nm is quite safe max for them.
Well, no one like cracks in the head. In reality a crack like this does not matter, it can get worse but not necessarily. Propably most 2.2T heads had cracks and sometimes they look like this: Klick!
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I don't think the cracks is reliant of the boost and power you use..? It's how you use the engine, if you turn off the engine right after heavy use without any idling and if your after run cooling system is broken... I always run the engine with light throttle or/and let it idle for few minutes after heavy driving.
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There is a difference on how much hp the engine is running in a sense of a more aggressive map, a higher cylinder pressure and combustion chamber, Engine gets stressed more at 2bar than 1.4. Also there are other factors that you may not be able to judge at any point (ie is the PCV system working adequately before any wear and damage occurs?, are the knock sensors sensing properly? etc)
yes, pretty much everyone does that and most have a proper map on the car as well. However I5 engine's weak point are those cracks. AND once there, only one thing can happen. As more Kms gather up, the crack will get bigger. Id hate to spend any money on a head to be serviced knowing that it is already weakened by a crack. I would rather spend a few extra $$ to get it fixed.
According to JP, the best way to avoid cracks or reduce the risk of having one is to polish that area as i mentioned.
Our cars dont need a turbo timer, they do need a nice thermal switch to make the after run pump keep the engine cool after switched off, and that feature is not so much for the head but for the turbo. Everything helps as you mentioned as well, but all im doing is stating my opinion. I dont do well with cracks, that's all and if id already spent 500 or 1000euro on a head rebuild id want it to be crackless.
Everyone has their own views though, so i hope it runs ok and troublefree
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