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Thread: Max Speed Vs. RPM

  1. #1
    Veteran blair's Avatar
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    Default Max Speed Vs. RPM


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    Stock bigport running twin webbers.
    S series Diff (3.9's)
    running less than 20deg locked advance... thinking of upping to 30 now that ive sorted a bit of cooling (carbs were tuned for 32 a long long time agooooo)

    what would you expect in each gear? and at what rpm?

    80 is the most i pull in second and thats at just over 6k according to my super sweet jumpyaround stock tacho...

    and 3rd just feels like poo above ~120 ( 5k?)

    and it honestly feels like it doesnt wanna pull past that/i dont wanna push past that... would this be alot to do with the timing @ those revs?

    opions please.

  • #2
    Veteran Rice86's Avatar
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    sounds still like standard

    just get a better diff ratio?..
    dose

  • #3
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    not allowing for my diff ratio compensation at 8000 RPM or so I get the reported following :

    1st- 50km/h
    2nd- 105km/h
    3rd- 150km/h
    4th-?? havent found a long enough stretch of road, I have had the needle hit the dash before on a somewhat short stretch though
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    Senior Member doony's Avatar
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    i remember my stock bigport and stock t series would pull similar figures to samQ's

    dont think i got that much out of 2nd though maybe 100 or so.

    this was at 7,900rpm or whatever the standard redline is for bigports.
    but it pisses me off when people assume your hooning cos your car is loud, has bald tires, a roll cage, fresh bake and dinted bumpers!!
    Or driving in a wolf pack.

  • #5
    Moderator Sam-Q's Avatar
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    yes I must say my tacho I know isnt tottaly acurate, it shows around where 8200RPM should be when I bounce off my 8600rpm limiter.

    Now all I need to do is find a very long quiet stretch of road, on private property of course
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    Hey guys,
    Here is a spreadsheet I made to caluclate revs and speed. You can change around the gear ratios, final drive etc and see how it might affect your shift point.

    http://duivesteyn.net/rob/t50_3pt9.jpg

    edit:
    Sorry thats just a pic...
    Here is the spreadsheet
    http://duivesteyn.net/rob/t50_ratios_2.xls

  • #7
    Veteran hao.'s Avatar
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    ^ genius! thanks man.

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    Moderator Sam-Q's Avatar
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    interesting, that really shows how big a gap there is between 1st and 2nd. This is why a more peaky engine with a high power can be slower without the right ratios to back it up.

    Now I wonder what would get a higher top speed for many of us 4th or 5th gear?
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    thats an awesome spreadsheet man!! good work.

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    ok so i thought 6500 sounded hot with induction...

    just took it to 7500 at 95kmish

    had a grin on my face for about 5minutes!!!

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