3 rings in the original pistons | FerrariChat

3 rings in the original pistons

Discussion in '308/328' started by derekw, Dec 21, 2020.

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  1. derekw

    derekw Formula 3
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    Sep 7, 2010
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    Derek W
    Hi all, has anyone tried using only three rings in the Borgo pistons? Four rings is a very dated idea and research has shown that the single second ring is sufficient, acting as an oil scraper ring. My thought is to use a standard chrome plated compression ring and a Napier style scraper ring in the third groove so that the second groove can be an accumulator space.

    http://blog.wiseco.com/2nd-ring-purpose-and-function-explained?hs_amp=true

    I have found a supply of Mahle rings which would fit and are very reasonable, £150 for all rings with the scraper ring from another set included in that cost. I could get two scraper rings but it seems overkill and only likely to add unnecessary drag.
     
  2. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    So if you leave the 2 nd ring gap empty the compression blow past is going to fill the space with gunk then, or blow crap into the sump and bugger the oil up. Not too keen on the idea myself
     
    thorn likes this.
  3. JCR

    JCR F1 Veteran
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    Mar 14, 2005
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    You should PM smg2. Get modern pistons and rings. The Borgo are archaic.
     
    ragtop1 likes this.
  4. derekw

    derekw Formula 3
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    I can get modern forged pistons with rings for $1000 but it is a waste when these pistons are like new and the liners too. My question after Mike’s comment is, in a 3 groove piston, where does the gunk that gets past the top ring go and would a greater volume under the top ring cause more blow-by. It might. I also wondered about the distance to the scraper ring reducing the lubrication of the top ring at the top of the stroke, but the original two scrapers had the same effect.

    I could use the top two grooves or even put in all 4 rings but I thought there would be some experience out there on dropping one scraper ring. I will ask someone I know in the industry as they may have an idea or know someone who does.
     
  5. ferrariowner

    ferrariowner Formula 3

    Feb 21, 2014
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    Ron
    Order modern replacement pistons from JE. I would not leave rings out.
     
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  6. BigTex

    BigTex Seven Time F1 World Champ
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    The OEM pistons have worked, all this time.

    To me, I would rebuild as original, or sell as a complete set, and go with the modern JE design and modern ring technology.
     
    ferrariowner and 430tdf like this.
  7. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    As you go from the top ring down to the bottom ring, the pressure behind the rings decrease. The top ring is subject to the highest firing pressure and this pressure gets behind the ring in the groove and pushes the ring out so it seals against the liner, the second ring is subjected to a lower pressure due to the sealing by the top ring- hence the second ring is not pushed as hard on the liner as the top one. If it has 3 comp rings and u leave one out you subject the lower scraper ring to extra pressure and i suppose you could get blow past, yet some pistons only have 3 anyway.
    I used to work on Sulzer engines with 900 mm pistons, you could only carry 1 piston ring up the stairs as that heavy, i could not stand up trying to carry 2. Yet these rings used to break at times.
     
  8. GordonC

    GordonC F1 Rookie
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    Aug 28, 2005
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    Gordon
    Back in 2016, Stevel48 posted a Ferrari document from 1983, the Technical Introduction to 308QV - it highlighted and compared all the changes to the just-introduced QV version of the 3.0 V8. While it's written for the US version, 99% applies to all the QVs. Page 6 details the new pistons - forged aluminum, with 3 rings - 2 compression, 1 oil ring. It's a really detailed document - click the attachment below to download and view:

     
  9. derekw

    derekw Formula 3
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    Total Seal came back to me and said use the top two grooves so that’s what I’ll do. A couple of sources I found say the second ring contributes only 15% of the compression so by extrapolation the third ring only contributes about 2% (but drags as much as the other two) so I’ll go with 3 rings.
     
  10. smg2

    smg2 F1 World Champ
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    I don't understand the false economy here. If these engines were easy to strip down and replace pistons, I'd say, give it a shot and see. The old 4 ring design has been changed for lots of reasons. Weight, drag, skirt etc...

    Good rings are $300-400 a set.. so why throw them on pistons they are not actually designed for?

    You're probably not the first to use less rings though. Interesting experiment.
     
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  11. Dancia

    Dancia Rookie

    May 15, 2015
    35
    I'd like to hear about how things fair over time. I'm not to adventurous on this things anymore.

    It does seem like a funny gamble to try to prove ... I'm not sure what.

    I think the risk outweighs the gains (which may be only theoretical or minimal) unless you weigh in curiosity. And don't mind pulling it apart again. And spending the time and money.

    A wise man once inscribed in his book about racing ALFA Romeos "Don't try and reinvent the wheel, the work has been done".
     
  12. derekw

    derekw Formula 3
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    I don’t think there is any risk here. Total seal said that many old engines had 3 compression rings and have converted to two without issues. I may still go for new pistons to get the higher CR and just sell the std pistons with all four new rings for someone who wants to stay with original performance.
     
  13. daytonaman

    daytonaman Formula Junior

    May 1, 2007
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    howard pigdon
    Superformance UK has what you need off the shelf
     
  14. derekw

    derekw Formula 3
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    Yes, I use Superformance a lot but will get pistons directly from the manufacturer as it costs less than half. I may get a liner from them as I have 7 spare liners at 82mm so will go with those if I source new pistons. Unless someone wants to swap a used liner for some parts they need.
     
  15. thorn

    thorn F1 Rookie
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    Aug 7, 2012
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    What's the theoretical reason to delete 1 ring?
     
  16. derekw

    derekw Formula 3
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    The additional sealing provides less benefit than the additional friction loss and liner wear.
     
  17. jdjagguy

    jdjagguy Karting
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    Sep 11, 2007
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    I have a NOS liner for a QV if that will work for you. Contact me for further detail.
    Richard C
     
  18. derekw

    derekw Formula 3
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    Thanks, I’ll PM you Richard. Are you the Maserati author? If so, do you know the funny story of the Benz aero engine in your car?
     

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