9A-ABF comparison

Discussion in '16-valve' started by Golfsburg88, Apr 25, 2010.

  1. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    Ah, it's only 90 mm bore spacing on the later engines. I suppose that they did this to stick them in the transverse engined cars? Or, to save tuppence on the block, head, manifolds and crankshaft? Shame they did not keep the 95 mm centres!
     
    Last edited: May 8, 2010
  2. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    Still can't really understand why VAG produced two almost identical engines, with different rod lengths?

    Bit like, I don't understand why they fitted a back-to-front clutch, in the early Gtis, when a conventional clutch would have fitted easily?
     
  3. A.N. Other Banned after significant club disruption Dec 5th 2

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    They produced the engines at different times though, one as a development of the other.

    I'm sure I heard the explanation once. Was it to do with emissions?
     
  4. danster Forum Addict

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    As with all things modern. They have to make them crud. So by adding the heavier tallblock to the lardy mk3 16v gti they could just about make it understeer as well as the vr6!:lol:
     
  5. SkyRocketeer

    SkyRocketeer Forum Member

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    I'm guessing the 9A/6A was the first production 2.0l valver block, which is simply an evolution of the 1.8 block. Perhaps the engineers decided on the next round of designing (or next evolutionary step) to increase the deck height, to afford longer rods, and all the advantages associated with it.

    Out of curiosity, what deck height & rod length do later blocks have, say for the 20v and FSI engines?? If they stuck with the longer rod length then it suggests that it was an evolutionary step, rather than an engineers whim.
     
  6. A.N. Other Banned after significant club disruption Dec 5th 2

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    There were big delays IIRC before the Mk3 GTI ABF 16v came out. I think the engineers were told to come back with 150 brake.

    Somewhere in the mix is the evolution of the 6A block from late '80s to ACE. Late 6As had crank sensor castings (not drilled) and wide block skirts, like the ACE.
     
  7. LeftcoastTigger Paid Member Paid Member

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    9A-ABF Block comparison

    Relative to the above discussion, the American site "panic Tech Papers" includes an article entitled "Connecting Rod vs. Stroke Analysis" at http://victorylibrary.com/mopar/rod-tech-c.htm

    Likewise, header manufacturer Jere Stahl and associates post their conclusions under "Rod Length Relationships" at www.stahlheaders.com/Lit_Rod Length.htm

    John C Erb, former chief engineer of oem piston manufacturer United Engine and Machine, and associates have authored a series of technical articles on combustion chamber shape, piston design, and squish, the latter titled "Magnificent Quench" at http://kb-silvolite.com/article.php?action=read&A_id=39

    LeftcoastTigger
     
  8. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    Bit pi**ed off now, I did not need to spend hours doing the sums.

    I sent this to danster yesterday, and I am dead chuffed that my theory appears to be correct!

    I did point out that all other things had to be equal, for what I posted to be a definative comparison. There is a lot more to it than my simple approach. But, it does show that rod length can make a difference to how an engine might perform. I am of the opinion, and always have been, that oversquare short rod engines produce more power because the piston accelerates away from TDC so rapidly that the speed of the mixture is so high that the momentum in the mass of mixture keeps it rushing in, even when the piston is slowing down. It can't brake so quickly. So it fills better.

    What do you recon.?
     
  9. infinity

    infinity Forum Member

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    just to add another couple in the mix, an engine which is almost identical to the 9a/abf in dimensions,

    Technical overview of the Clio RenaultSport 197



    Engine
    Induction capacity 1,998cc
    Bore x stroke 82.7mm x 93mm
    4 in-line cylinders with 16 valves
    Compression ratio 11.5:1
    Max. power kW EEC (hp DIN) 145 (197)
    Max. power 7,250 rpm
    Specific power output 100hp/litre
    Max. engine speed 7,500 rpm
    Max. torque Nm EEC (m.kg) 215 (21.9)
    Max. torque (rpm) 5,550
    Specific torque 108Nm/litre
    Injection - Multipoint

    Con rod details

    Engine Type: F4R
    Rod length C/C: 144.00mm
    Small End: 21.00mm
    Big End: 51.60mm

    Engine - 2.0L Duratec ST - 173PS

    * Displacement (cc): 1988
    * Bore: 84.8mm
    * Stroke: 88.0mm
    * Fuel type: Unleaded petrol, 95 (RON)
    * Max power: 127kW
    * Max power: 173PS
    * At engine speed: 7000rpm
    * Max torque: 196Nm
    * Max BMEP: 12.2bar
    * At engine speed: 5500rpm
    * Compression ratio: 10.2:1

    139mm con rod
     
    Last edited: May 9, 2010
  10. infinity

    infinity Forum Member

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    the latest gen of civic engines appear to have 86mm bore and stroke
     
  11. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    So, it appears that good power can be obtained from an undersquare/short rod engine.

    Read somewhere, probably on here, that, when VW brought out the 16v engine, engine tuners said that getting big power out of them would be a problem due to the poor shape of the inlet tracts, or was in the exhaust tracts?

    So, anyone got cross sections of the heads on all these engines?
     
  12. Brookster

    Brookster Paid Member Paid Member

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    Brian G has done a cutaway thread.

    http://www.clubgti.com/forum/showthread.php?t=193826
     
  13. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    Iv'e seen Brian's threads. My machine usually falls over when I try to load them. How does he do it?
     
  14. A.N. Other Banned after significant club disruption Dec 5th 2

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    FWIW, another update:

    Code:
    [B]Engine   Bore Stroke Rod length Compress Deck height*  Comp height  BHP     NM   Characteristics[/B]
    
    9A        82.5 92.8   144mm      10.8:1   220mm         302mm        134     186   More power
    ABF       82.5 92.8   159mm      10.5:1   236mm         ???mm        150     180   More torque
    Type-R    87   84.4   153mm      11.7:1   223.9mm       ???mm        246     217   "No torque!"
    Clio      82.7 93.0   144mm      11.5:1   ???mm         ???mm        197     215   French!
    Duratec   84.8 88.0   139mm      10.2:1   ???mm         ???mm        173     196   F*rd!
    Civic     86.0 86.0   ???mm      11.0:1   ???mm         ???mm        197     188   
    306 GTi6  86.0 86.0   ???mm      10.8:1   ???mm         ???mm        167     193 
    
    * Crank centre line to deck
     
  15. A.N. Other Banned after significant club disruption Dec 5th 2

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    Peugeot 306 GTi-6/Rallye added above, at a square 86 x 86. These engines and the 150/155bhp predecessor engine both lack low down torque, though the 6-speed first gear doesn't help.
     
  16. brutalmk2-16v Forum Member

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    Nissan Pulsar gti+gtiR are also 86x86
     
  17. Golfsburg88 New Member

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    The short rod in the earlier 2.0's 9A blocks tend to put more pressure on the wall, ABF with the 159 supported a reliable long life motor than the 9A and the KR
     
  18. Dave

    Dave *Very Smart* Pedantic Old Fart Paid Member

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    I understand about the side pressure reduction, I mentioned it in post #46.

    Below is not 16v I know, but still the long vs short rod theme at VAG:

    What I was getting at, was that Audi first produced the 3A 8v engine with 144 rods, and used it for five years from 1988 to 1992. (The 3A led to the 16v 6A and then 16v ACE) For 3 years, from 1990 to 1992 they also built the AAD 8v engine with 159 rods. From 1993 on all 2.0 L 8v used 159 rods.

    So, for three years, they were building two identical engines, except for rod length. All other major parts were identical: Heads, cam, valves, injection, etc. The only difference was the exhaust manifold! And, the AAD only had a catalyst, but the 3A was available with or without. I think Chris Eyre's mention of emissions may be the right track as to why?

    (As a side line: I was looking at the reverse clutch system on Mk2 Gtis. Looks like VW are not to blame. I recon it came with the engine when they bought Audi from Merc? So, we can blame Merc for that!)
     
  19. LeftcoastTigger Paid Member Paid Member

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    Toyota has released two versions of their 1.8 litre I4, see http://www.sandsmuseum.com/cars/elise/thecar/engine/toyota.html for basic information, viz

    A 1ZZ 1794cc model with 79.0 x 91.5 bore/stroke and 146.65 rod, quoted as producing 145bhp @ 6400, 125lb/ft @ 4200 with 10.0:1 compression

    And the 2ZZ 1796cc version with 82.0 x 85.0 bore/stroke and 140.15 rod producing 190bhp @ 7600, 133lb/ft @ 6800 with 11.5:1

    Assuming identical deck heights, at 1.60:1 and 1.65:1 respectively their rod length to stroke ratios appear pre ordained by the piston compression height, deck height, and stroke dimensions rather than desired torque characteristics

    The latter appears principally due to completely different cylinder head designs, compression ratios, camshaft events, manifolding, and mapping

    Perhaps VAG originally intended raising hp, torque, and rpm to emphasise performance, believed the rod length/stroke ratio change advantageous, then aborted the programme due to promising 5 valve results

    Lastly and relative to engine architecture, does any member have access to the engine reconditioning data sheets available through established National reconditioning groups, for instance the American Engine Rebuilder Association's AERA RRO-SIS database?

    These databases contain virtually every conceivable dimension required to identify and machine all basic components, describe updates and prudent "in house" modifications, and may include both oe casting and part numbers
     
  20. infinity

    infinity Forum Member

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    wasn't the ABF detuned as it was a bit close to the top of the range VR6??
     

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