Squish,valve shrouding & V.E. in1.9 Mi16
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  1. #1
    1000+ Posts pgti6's Avatar
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    Default Squish,valve shrouding & V.E. in1.9 Mi16

    Along with an increase in compression, what is the best way to improve air/fuel burn & flow through the Mi16 1.9l head-ie: volumetric efficiency?

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    [The low emission XU9J4Z engines (our Oz versions-cat equipped) have a lower piston crown height compared with the non-cat engines. The piston sits 040'"- or 1mm further down the bore-hence the 9.7:1 compared to the 10.4:1 comp ratio of XU9J4's.]

    I'm aware that the inlet cam was also retarded with the 'Z' engines (although this isn't an issue in my situation as I have adjustable cam gears}.

    In reference to the lower comp engines, what is the safest minimum squish distance between the piston & head? Component expansion & piston-head collisions are what's at issue here.

    I've read that .035" minimum squish seems possible using standard components up to 6500rpm. What about 7500 (which these engines can handle comfortably)?

    The cylinder head is recognised as one of the best flowing N/A heads around but can still be improved with porting and bigger valves.

    Could the gains from the bigger valves be somewhat compromised by their proximity to the bore causing partial shrouding?

    Comments from those experienced in this area of engine performance gains appreciated.

    Jeff
    Track car-Steel Grey 405 Mi16 2.2 litre


    405 Track car build thread moved to-
    http://forum.205gtidrivers.com/index...ic=143279&st=0

    Lap times-
    Sandown 1 27.9
    Phillip Island 1 53.8

    Previous Frenchies-
    1988 205Gti
    1998 306 GTi6
    1997 306 N5 sedan
    1996 306 N3 XT hatch
    1976 Renault R16TS manual in Avocado
    1976 Renault R16TS manual in Trak Yellow
    1975 Renault 5 Guernsey, Channel Islands
    1972 Renault 4 Guernsey, Channel Islands

  2. #2
    1000+ Posts PeterT's Avatar
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    Default

    secret squirrell stuff.........the inlet cam is advanced on a Z engine.

    '92 205 Mi16
    '90 Mi16x4

  3. #3
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    From "Four Stroke Performance Tuning" by A. Graham Bell:

    Good solid motor with steel rods can run with a minimum of 1.0mm of squish.
    Valve to piston vertical clearance 1.5mm minimum.
    Diameter of valve cut-out in piston to be a minimum of 3.0mm greater than the valve head diameter (in a road engine, to allow for carbon). Race engines can get by with only 1.25mm.

    Rick

  4. #4
    1000+ Posts pgti6's Avatar
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    Default

    Apologies for the delay in replying.

    Rick, I picked up a copy of that book this week-very informative. It should give me much of the info I was after.

    Thanks too, to PeterT for sharing a few 'squirrel secrets' offline.


    Jeff
    Track car-Steel Grey 405 Mi16 2.2 litre


    405 Track car build thread moved to-
    http://forum.205gtidrivers.com/index...ic=143279&st=0

    Lap times-
    Sandown 1 27.9
    Phillip Island 1 53.8

    Previous Frenchies-
    1988 205Gti
    1998 306 GTi6
    1997 306 N5 sedan
    1996 306 N3 XT hatch
    1976 Renault R16TS manual in Avocado
    1976 Renault R16TS manual in Trak Yellow
    1975 Renault 5 Guernsey, Channel Islands
    1972 Renault 4 Guernsey, Channel Islands

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