CC : increace in BHP and Torque

Discussion in '8-valve' started by Dub Nutta, Apr 11, 2005.

  1. Dub Nutta Forum Member

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    I am currently running a 1.9 8v and am planning to rebuild it with some ARP bolts and get some work done to up the rev limit. options are 1.9 or 2l with standard pistons or 2l with the 1.9 pistons which would give 2032cc. IIRC 50cc increace will equate aproximatly to a 1BHP gain, does anyone have a similar forumle for torque increase.

    I am undecided wether or not to stick with the 1.8 crank as it does keep the motor nice and revy and I would imagin lower the rotating mass of the crank?

    I have heard that newer VW's (95>?) have forged cranks, what would early engines have then? Is there an advantage from changing to a forged crank.

    Also earlier rods without the oilway down the centre are going to be stronger or are later rods constructed in a different way. I would imagin S3 rods are stronger than DX Mk1 1.8 rods?

    Any tips on building a strong bottom end without the expense of aftermarket components much apreciated.
    Edited by: Dub Nutta
     
  2. DEX

    Dex Paid Member Paid Member

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    the 50cc = 1bhp is complete rubbish - ignore it.



    what is the current bore? 83 or 83.5mm?


    a std vw crank, especially if u have it balanced and knife-edged, will be plenty strong enough for 200bhp


    if you are staying 8v then there is no real benefit to keeping the short stroke - you are as well to get the longer 2 litre (or even diesel) crank and make your power from the torque rather than the revs.


    out of interest what gearbox do you run?
     
  3. chrismc Forum Junkie

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    If you want an 8v to be revvy, then id stick with a standard crank & 83mm pistons...1870cc? IIRC

    Spend some time/money on balancing/lightening it all & use the ARP rod bolts & a lightened flywheel...

    To make use of the increased revs available you really need to go for a Pack D race head & hot cam.. :)
     
  4. Dub Nutta Forum Member

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    I picked up a fresh 2Y with a Quaife a few months back and haven't used it yet as the cars is in bits. gona be a bit taller than the 1.6 GTI box I used to run but will put a 4.2FD in it once I start running 8K+

    I think the bore is 83.5 but not 100%

    Might go for a decent big valve head with all the trimmings and keep the revs down to about 7400 for the time being and save up for some steel rods and forged pistons and the 4.2 FD at a later date.


    Once it comes back from being painted I expect it'l all go out the window and i'l jsut throw the 1.9 back in as it was!
     
  5. VR6Will Forum Member

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    what is it digi or k-jet?

    im running a 2l short block! its nice and revy motor with loadsa torque, im not too sure about the short vs tall block debate, there is however loadsa stuff on vwvortex.

    a standard vw crank should be plenty strong enough, if however you do decide to have a 2l tall block, i'd fit a knife-edge diesel crank, ;).

    Apparently stock vw bolts should also be strong enough, i did however fit arp rod bolts just to be on the safe side, dont wanna hit 8k and for a rod to come through the block [8(]

    Definately go for a big valve head, have you though about x-flow?

    4.2FD might be a bit overkill, the 1.6 GTi box would have only had a 3.9FD, i had a 3.9FD fitted to my ACD box, (same ratios as 2Y but has a slightly longer 5th) and its fine!
    Edited by: oakgreen88
     
  6. Dub Nutta Forum Member

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    Planning to run it on ITB's have thourght about X-flow but with the hassle finding a head, converting to mechanical lifters and clerance issues I don't think i'l bother. I've taken the rain tray out so there is plenty of room for the bodies to breath and aslong as the manifold is heat wraped and a heat sheild fitter I can't see there being any issues, the scuttle is a natural high pressure area on the car once aerodynamics come in to play.

    4.2 will be about right as it's a pure track car and won't be hitting much more than 130 even at Snetterton i don't think.

    has anyone got any info on how big you can go with valves in a std head on the std seats.
     

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