Piston failures

Discussion in 'Workshop Forum' started by speedy fiat, Dec 29, 2019.

  1. Simon Oaten

    Simon Oaten Daily Driver

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  2. speedy fiat

    speedy fiat Daily Driver

    Location:
    United Kingdom
    I finally managed to get hold of a set of forged pistons and rods after much searching. I often forget that this is a near 30yr old engine that was only sold for a few years and then not in great numbers. Lots of sites say they had the relevant bits for sale but in reality didn't have the stock, or it was laughably expensive. I've ended up with 'Wossner' pistons sourced from Italy and 'Maxspeeding' rods sourced from Poland. The rods are Chinese made and depending on where you look are either '...really quite good and excellent value', or '...Chinese crap'. The latter tends to come from seemingly ill educated opinions based on dubious stereotypes, as I couldn't find any reports of failure due to quality issues, happy to be shown otherwise before I actually install them in the engine. The block has just been dropped of to be sleeved and bored as it was already at the max over size. Should get it back in a couple of weeks.
    Apart from the reported piston issues the other reason for forged rods and pistons was that I can safely raise the rev limit on the engine to help address the poor gearing of the standard gearboxes.
     

    Attached Files:

    Dr.Jeff likes this.
  3. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Looks great. I believe these pistons and rods are for the Uno Turbo block? I'm curious, are the pistons specifically designed as "turbo" (boost) application items? Naturally if they are for a UT then I assume so.

    I'm with you on the whole China product opinions issue. Just like every part of the world, there are all levels of quality made in China - from some of the best to some of the worst....as I said, just like everywhere. Frankly, in general I've found better quality coming from China than I have from the USA. Furthermore most of the products that are claimed to come from other countries are in fact actually manufactured in China. The point being that the country of origin is not a valid basis to make any quality assessments. Price is also not a valid indicator of quality. That is purely a function of the sellers level of greed. And regarding opinions in general, the strongest ones often come from less knowledgeable people. So I rarely follow them, but prefer to look at the facts - evidence based or scientific results.

    Keep us informed.
     
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  4. speedy fiat

    speedy fiat Daily Driver

    Location:
    United Kingdom
    Yes, the pistons are specific to the 1.4 Uno Turbo and very early Punto GT. The rods appear to have the same dimensions as several variants of the SOHC engine and so are not specific to the Uno turbo
     
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  5. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Is it possible to get a rough comparison between these aftermarket turbo pistons and stock 1500 SOHC (non-turbo) pistons? I don't mean the overall size (that is different), but any specific design features. For example turbo pistons typically have the ring grooves moved lower to increase the top landing thickness, and thicker crowns. Does anything stand out to you with these? I'm just curious, the stock SOHC pistons have rather tall top landings already compared to more modern pistons so I wonder just how different the turbo pistons really are (aside from being forged).
     
  6. Rupunzell

    Rupunzell Bernice Loui

    Location:
    California
    Repeating an endless droning about Saab's turbo engine management. Having looked at Saab's Tronic-5 turbo engine management system, this is what is required to produce a reliable turbo engine. While the engine internals must be up to the torque demands of a turbo engine, making a reliable turbo engine at any reasonable boost is NOT simple.

    From fuel delivery, detonation sensing and control, ignition control, turbo boost sensing and control, temperature monitoring and corrections for compressed air_ambient air temperature_engine coolant and a long list of other engine management demands. Once can upgrade the engine internals, that alone will not produce a completely reliable turbo engine, proper engine management is a major aspect of turbo engine reliability and function.

    About the Saab Trionic-5, This became the basis for nearly every production and motorsport turbo engine produced.
    Read and look over how this turbo engine management system works. This will give an idea of what is required to make a reliable turbo engine.. It's a LOT more than fueling correction or ignition control.
    http://4saab.com/T5Suite/Trionic5.pdf

    Piston failures in turbo engine are often the result of detonation, stronger piston, con-rod and such alone will NOT cure the root problem of poor turbo engine management.
    Oh, by the way, Fiat Turbo Uno engine block is different than the normally aspirated engine block which has Siamesed bores for rigidity, turbo block does not for enhanced cooling. This is why the turbo blocks have smaller bores than the non-turbo blocks among other differences.

    Bernice
     
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  7. myronx19

    myronx19 True Classic

    Location:
    Toronto, ON Canada
    Actually - the 1300cc Mk1 Fiat Uno Turbo engine block isn't much different than a regular 1500 block. Yes, it has a smaller bore and has additional galleries for oil/water feeds to the turbo (and mounting bosses), plus sprayers on the connecting rods and main journals for the piston bore and piston underside - but the Mk1 is a siamese design. It is quite similar to a regular 1500 otherwise.

    This is my Uno Turbo block (1.3L) - The Mk2 1.4L is different.

    upload_2020-2-7_21-37-0.png
     
    Last edited: Feb 8, 2020
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  8. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I believe the earlier reference was about the thickness of the blocks between the cylinder bores. Compare these two blocks, your 1.3 Uno Turbo (top) and a stock 1500 SOHC:

    upload_2020-2-7_21-37-0.png IMG_0768.JPG

    Stands to reason that a engine with higher pressures and temperatures (i.e. a turbo) will benefit from more meat and cooling passages in between the cylinders. I'm sure it might be dependent upon how much boost it is subjected to, the overall design and function of the cooling system, the management of charge temps, and several other significant factors. So it seems the larger bore, thinner inter-cylinder block could be fine with a small low-boost turbo and appropriately designs supporting systems.
     
  9. speedy fiat

    speedy fiat Daily Driver

    Location:
    United Kingdom
    I should get mine back from having the block relined next week and so will post a picture of a 1.4 turbo block. I'll also have the pistons back and so can show the differences between the standard 1500 and turbo pistons
     
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  10. lidox19

    lidox19 Daily Driver

    Location:
    Cheltenham UK
    This is a 1.4 Punto GT block.
    Punto GT Block.jpg
     
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  11. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Not only does it have more material in between the cylinders, but those coolant passages connecting to the head look to be much larger overall.
     
  12. Brad Garska

    Brad Garska True Classic

    Location:
    Saline Michigan
    The difference of material that is between the cylinders is due to the bore size 86.4 vs 80.5. This adds ~6mm more thickness. The bore to bore center lines are the same - the crankshafts are interchangeable. 1.3 stroke is 63.9 (same as 1.5 X1/9) and 1.4 is 64.7 often used in X1/9s to increase displacement.
     
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  13. Simon Oaten

    Simon Oaten Daily Driver

    except:

    the 1116 / unoT / PuntoT - have water around all the holes, while the 86.xx blocks are "siamessed".....

    the German? chap with the turbo x19 racecar - used a 1300cc (86.xx) block for his turbo race engine
     
  14. speedy fiat

    speedy fiat Daily Driver

    Location:
    United Kingdom
    I don't have any stock 1500 pistons, but attached is a picture of an Uno turbo forged piston next to the old caste ones I was using. You'll see the obvious damage caused most likely by historic poor engine management, primarily detonation control. Going for forged rods and pistons wasn't in direct response to the engine management issues (that would be an expensive waste of time, that fix requires a decent ecu, etc) but to allow a higher rpm to be used and as a general precaution as a result of a 70% power hike.
    In response to a question I asked myself about the quality of forged 'Max Speed' rods the engine shop which relined my block said that they are good stuff, and they are highly regarded for their work
     

    Attached Files:

  15. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Thanks. They appear to be very similar to one another in terms of what makes a "turbo" piston (other than the material structure), such as the ring landing heights. But then they would because they are both for a Uno Turbo.
    I was looking at the stock (NA) 1500 pistons and they are also rather similar to these in general design (again, aside from being cast). Older engine designs like ours had rather robust pistons with thick rings, tall landings, and heavy crowns. So in that aspect maybe they might be a little more tolerant of a low boost application (with a conservative tune).
    Not the best image for this purpose but here is a pic I found of the 1500 pistons for comparison. You can see how the ring landings are similar to yours:
    12250 (1).jpg
     

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