Is it worth going Crossflow?

Discussion in '8-valve' started by madasafish100, Dec 14, 2010.

  1. mr hillclimber Club GTI Supporter and Sponsor

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    I will check properly in the new year... my machinist is in a "slip and slide in the snow" area!
     
  2. Whittle Forum Member

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    42mm and 35mm will definatley fit;

    [​IMG]
    [​IMG]
    [​IMG]

    Theres not much space in the middle but who cares.

    However, just because they phyisically fit, doesnt mean there wont be lots of shrouding (particuarly on the inlet valve)

    im not saying there WILL be shrouding, im hoping someone more knowledgeable can enlighten me/us!?
     
  3. madasafish100

    madasafish100 Forum Member

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    So is that on the std valve seats? Is this your head in the pics, didn't think you had the valves yet?

    I'm surprised they fit on the std seats as I went to see an engine builder this avo and he was pretty sure that you wouldn't get bigger valves on the std seats. Especially on the exhaust.
     
  4. Whittle Forum Member

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    No its not mine, i was just doing research

    He doesnt say what seats he is using, but theres no way they can be stock!
     
  5. danster Forum Addict

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    No chance it is on standard valve seats.

    This really is very simple guys. 40.5mm is the inlet valve seat OD so a 40.5mm is the largest optimised size of valve on std inlet valve seats.

    The std exhaust seats are 34mm OD but pushing the valve size to the outer extremities of this is not a good plan due to the heat involved, a 33.5mm valve is a possibility.

    This is exactly the same as the counterflow hydro head stuff.

    There are folk looking into this at manufacturer level at the moment. It would be best to hold off for a while till a bit more information has been compiled.
    For road use the 40.5 and 33.5 valve sizes will be fine. And a fast road 2.0 is not going to rev high enough to justify a solid lifter conversion.

    I would seriously stop worrying about the ultimate power figures you expect. Have you all got optimised transmission ratios and lsd diffs fitted? This will make far more of a difference than larger valves to how quick your car goes.
     
  6. Whittle Forum Member

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    Horsepower = Girls [:D]
     
  7. shaz8389

    shaz8389 Forum Junkie

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    Torque > horsepower
     
  8. wippy748s Forum Member

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    I shall get him to dig out the dyno results and get him to bring them to work tomorrow, there was massive ammounts removed from the inlets which worried me from the start, in fact so much they were welded cut and rewelded again, it is 45mm from the butterflies all the way down to just before the valves, if we can get down the unit at lunch tomorrow i will get some pics, i think he has the flow bench readings somewhere too.

    he would like it to make peak around 6.5-7k but obviously would like it to hold on a bit over that and would ideally like 170ish bhp, it has double valve springs but i am not used to the cross flow so could these be standard ?, it has solid tappets which the same bloke who did the head made himself so they are a bit of a unknown too, if i can remember rightly it made 147bhp but will check the printouts to see where it made this

    what would be the best way to go increasing the cr, if you think it would benifit running higher than the standard pistons will cope with then for the sake of a few more i guess it would be worth getting some forged pistons

    your a star and any help would be much appreciated, i have tried everything i can mapping wise but i am as far as i can go.
     
  9. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    A well sorted fast road 8v gives a very nice drive but...
    Seriously though,
    Assuming dyno's numbers suggested in this thread are absolute, which they are not, would you not be better off just simply installing a std ABF engine on either digifant , Kjet or otherwise?
    Remember engine performance "gains" do not occur at only one point and it does become expensive to make an 8v engine breathe air and homogenise fuel to form efficient combustion. This range for the desired level of efficiency will be compromised by, vehicle use, cams, compression, fuel economy, fuel quality. In my opinion and based on actual testing work shared here, the money spent on modifying a 2.0 8v will result in near partially optimised standard ABF performance. Some of the money saved from just installing a standard ABF unit can be, in the future, used to make the 16v even faster.

    The money spent on building a 160bhp@6000rpm and 150lbft@4000rpm 8v would result in a 190bhp@6600rpm and 160+lbft@5500rpm 16v motor, and that is not throwing all the tricks at the valver. Both engines if fitted to a MK1 on appropiate gear ratios will make a very quick car with the valver having a distinct edge.
    We can work with the physics but we cannot change it.
     
  10. wippy748s Forum Member

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    this is the dyno plot , the dotted run is the first one and the solid one is the last before we run out of time

    [​IMG]
     
  11. Mike_H Forum Addict

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    Bigger valves on both sides more than doubles the cost of the head, unless you've got a good mate with a machine shop. Inserting bigger seats costs about 100 for 4 valves, as it needs to be done to v. tight tolerances, and normally needs liquid nitrogen. Then you've got the cost of the valves on top of that. Unless you're tuning for full race power, then you're better off spending the money elsewhere.
     
    Last edited: Dec 23, 2010
  12. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    wippy748s
    The curves closly resembles a factory Digi ABF curve.
    [​IMG]
    The dip post 4500rpm suggests there are issues holding back the torque after this point to what I percieve to be 5700rpm. Then due to the work done to the head the torque drops off more 16v like (slowly) from 5700-6800rpm.
    Not sure based on the design of the engine if further mapping between 5700-6800rpm would increase the torque to target 170PS.
    Dips and troughs aside, if that curve correlates to anything I have tested and tuned, I would imagine that engine will pull the vehicle quite strong though.
     
  13. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    STD breakers ABF vs Wippy Mod 8v X flow

    The plots from above where combined on a common spreadsheet.
    The assumpsion here, both dynos are reading or estimating the clutch power and torque the same and the result is compartive.

    [​IMG]

    We see here the modded X flow is just about matching the used ABF engine for torque. The range of torque is limited compared to the std 16v and its low down response sub 3.K will be compromised.

    Assuming the dip is fixed posted 4500 rpm this is what the new torque curve would be projected to look like.

    [​IMG]

    The second hand ABF 16v engine can be further improved without expensive add ons and that was proved on another vehicle tuned to 167lbft and 180+PS

    So based on this exercise the question to the OP is it really worth it?
     
  14. Mike_H Forum Addict

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    Note how the 8v has much more torque low down... NOT :lol:
     
  15. Brookster

    Brookster Paid Member Paid Member

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    :lol:

    Note From Dan to Santa !

    Please can i have 8 more Valves for Christmas ;)
     
  16. Admin Guest

    8v's been there done that wasted loads of money on them...
     
  17. danster Forum Addict

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    Good to see you chose a poorly setup engine for the comparison there. And possibly poorly built too by the sounds of the miss matched parts. :clap:
    I am sure there are equally as many dogs of 16v engines out there that folk have got it all wrong when planning and building them.

    Have a look at GeorgeHH's plot and do the same comparison. Very little cash spent on that.
    And that is just thrown together with less than a few hundred quid of parts. ;)

    How much is your MS conversion coming in at? How much for all the time optimising the map? These all need to be taken into consideration as real life factors. You lads that have all the experience of building and setting up MS need to realise that a lot of folk do not have the skills to do the same, so will be paying for that too.

    And still no mention that a lower final drive will make more of a difference than any engine tuning. :lol:
     
  18. bens_cab Forum Junkie

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    Danster with the megasquirt you just need to fit it toyotec then has a word with it and its all sorted perfectly running car lol
     
  19. Brookster

    Brookster Paid Member Paid Member

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    Think i forgot to mention in my Build Thread about the 3.94 final drive and Quaiffe Diff ;)

    They all just like to wind you up Danster don't bite at them :thumbup:

    There a MK2 *stra 8V Turbo in the ESC Series running 10's on Megasquirt interesting 8V for you to look at !

    http://www.eurosportscompact.co.uk/entries2010_detail.php?escID=78
     
    Last edited: Dec 23, 2010
  20. danster Forum Addict

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    Heck I know it is all banter. But unfortunately others may not and get drawn in to thinking it is not worth while.
    I suppose if all one is concerned with is blasting down the 1/4 mile strip then the added weight over the front wheels that the 16v gives is something to consider.
    Folk that want to go round corners quicker may look at other factors.
    Class limits too are something that I consider when suggesting an engine choice.
    A lot of rally classes will mean you jump up to the next class with a 16v. 1.6 8v is in with 1.4 16v engines. And also 1.6 16v is in with 2.0 8v. And on that note let me see any VW 2.0 16v perform well against all the others out there. No chance. ;)
     

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