Quoted compression ratio
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Thread: Quoted compression ratio

  1. #1
    Member martook's Avatar
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    Default Quoted compression ratio

    Evening, Playing around with the idea of increasing the measly 8.0 to 1 compression ratio of my 850cc Floride motor by fitting a 750cc R4 head, (same size valves just needs the ports opened up) so I measured the combustion chamber volume (25.3cc) the manual has the Floride motor at (27.3cc), I thought I was on a winner here, fed all the data into the online calculator & it came back with: std motor 7.6 CR - 750 head on 850 motor 7.9 CR.
    Renault quote the CR for the 850 motor as 8.0 but its NOT. I guess the next step is to knock 40thou off the head.
    Cheers
    Brian

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

    Hi,

    I fed the figures into my own spreadsheet and it came out to 7.99:1. That is using bore as 58mm and stroke as 80mm and a compressed head gasket thickness of 1.1mm. That is a guess but taken from R8 gasket thickness.

    Then with the 750 head figures you supplied it works out to 8.49:1. Whichever, it sounds low to me because I would have the head skimmed to at least a 9:1 or little higher. I have no experience on these little engines but from what I've heard they were tough enough to power millions of cars.

    Not sure what calculator you used.

    Regards, Frans.
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    Young enough to do it anyway.

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    Default

    Well, the competition engines (R1063 cars) ran pretty well at Le Mans and long distance rallies like Rome-Liege-Rome. On the Mille Miglia, Redele and others won their class for quite a few years. For the Mille Miglia, he did 1,000 miles in 14 hours or something like that, so you'd imagine he wasn't below 5,000 rpm very much of the time.

    The engines had LARGE Solex carburettors and big manifolding.

    You could of course lash out and go to 904 cc as well as attending to the inlet and exhaust ports. Does yours have the Dauphine Gordini manifolding?

    All good fun.
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    JohnW

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  4. #4
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    Default Go Big Block

    Why stuff around with a few HP

    Go Big Block

    http://speedhunters-wp-production.s3...3-1200x800.jpg

    da.jpg

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    A genuine Floride motor should be a Dauphine Gordini motor with a 4 speed gearbox.

    I endorse Johns words re R1063.

    There is a Dauphine in our club that appears to be, and is stock standard including the 3 speed gearbox, but has gained heaps of extra go just with port polish and carefull matching, and working on, all of the original components. Plus the guy that drives it will out drive all similar and some bigger engined cars. It is not about sheer HP but the challenge of getting more from less. He sold an R8 Gordini to buy this car. Even the paint and interior are orginal. A more powerful motor only allows you to accelerate faster and go up hills quicker and if you are just out touring in an open top car, and sticking to the speed limit, do you need to go any quicker? I don't think so.

    When on a Foride Caravele Rally in France I often travelled with a guy and wife in an original Floride. My wife and I drove a late model Caravelle complete with two barrel down draft carby. The only time the Caravelle showed up the Floride was on long hills. On the the rest of the trip it performed well enough to drive at the speed limits which is all both of us should need to do.
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  6. #6
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    Oh please don't Caravellize the Floride. There are too few of them left in an original state.
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  7. #7
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    Afternoon, Frans - Thanks for pointing that out, I did the calculation using the same figures as you using an online tool, did it again with a different one & got the same figures as you, happy now I know Renault hasn't fudged the figures.
    John - yes it's a gordini motor.
    Sunroof - I am aiming to keep it as original as possible keeping in mind it's 59 years old & some parts are unobtainable, I have been replacing the rusted chassis & sills & adding reinforcing so the weight has increased a bit & would like to increase the motor output to compensate.
    Cheers,
    Brian
    2008 ford Mondeo 2ltr turbo diesel + 6 speed alsin g/box
    1979 cx c-matic
    1977 cx 5 speed
    2000 peugeot 306 convertable
    1978 peugeot 604 sl
    2005 c5 (wrecking)
    2003 c5 auto (wrecking)
    2001 c5 5 speed
    1960 Renault floride under restoration

  8. #8
    Too many posts! JohnW's Avatar
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    All good. Original Florides are a bit thin on the ground.

    I suggest you PM Sunroof and get in touch with the very smart owner of the Dauphine that he mentioned! You can do plenty without getting extreme and altering the appearance of the engine bay, and of course you do want it road-drivable not track-competitive!

    Are you already a member of our Renault 4CV Register of Australia? We cater for all the 4CV derivatives and have lots of knowledge. You mentioned Frank, my predecessor as National Coordinator. Frank has a 904 cc Gordini motor in his 4CV and it does go pretty well....

    Cheers
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  9. #9
    Member martook's Avatar
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    Yes John, signed up late 2018, Frank has been very helpful & found a set of the brackets that hold the backrest to the base on the floride seat, still looking for a set for the other seat, the previous owner or the previous previous owner appears to the lost them when he had the seats recovered.
    Cheers,
    Brian
    2008 ford Mondeo 2ltr turbo diesel + 6 speed alsin g/box
    1979 cx c-matic
    1977 cx 5 speed
    2000 peugeot 306 convertable
    1978 peugeot 604 sl
    2005 c5 (wrecking)
    2003 c5 auto (wrecking)
    2001 c5 5 speed
    1960 Renault floride under restoration

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