2.1 8v

Discussion in '8-valve' started by newkid, Jul 11, 2012.

  1. newkid

    newkid Forum Member

    Joined:
    Nov 17, 2006
    Likes Received:
    0
    Location:
    Toton, nottingham
    I'm thinking of going down the 2.1 8v route. Is there a definitive guide on whats needed etc. Is it a diesel crank thats required? If so which one? Are there any block modifications required to get it all to fit correctly etc.
    I already have a 2e bottom end in my golf but also have a ported and polished head with a 272 cam to go on it. Then ported and polished inlet and throttle body eventually.
     
  2. Vdub_Matt Forum Member

    Joined:
    Jun 4, 2012
    Likes Received:
    0
    Location:
    Plymouth
    can you not just get it rebored at an engines a slap bigger piston rings on ?
     
  3. Hotgolf

    Hotgolf Paid Member Paid Member

    Joined:
    Apr 23, 2004
    Likes Received:
    362
    Location:
    Smelly Cornelly
    Diesel crank and 83.5mm pistons to do it properly, or just machine the std pistons to suit to get 2042cc. A knife-edged crank and turned down int. shaft needs no clearence mods, where as a std crank and shaft need a little bit of fettling to clear the rods, but nothing major.
     
  4. newkid

    newkid Forum Member

    Joined:
    Nov 17, 2006
    Likes Received:
    0
    Location:
    Toton, nottingham
    which diesel engine crank is it i would require? Also how much would need skimming off the int shaft?
     
  5. i_am_me Forum Member

    Joined:
    Jun 23, 2012
    Likes Received:
    0
    Location:
    riby
    i always wondered about this.
    from what i was told a while ago you can put a derv crank straight into a 2.0 bottom end with stock pistons and it will up the capacity.
    ive never been sure of this and would like some more info about it before trying it and finding out it doesnt work lol.

    basically is it possible to drop a derv crank in a 2.0 bottom end with a mk2 digi head without anything breaking?


    also is a digi head better than a mk3 8v head?
     
  6. Hotgolf

    Hotgolf Paid Member Paid Member

    Joined:
    Apr 23, 2004
    Likes Received:
    362
    Location:
    Smelly Cornelly
    If you use the stock pistons as they are, they will stick out of the top of the block an extra 1.35mm over standard. If you're brave enough to try this carry on, although I think you'll find some piston to head contact lol.
    Seriously though, the crank drops in no with little problems that can't be over come with common sense. The std. pistons will need to be machined to suit.
    Personally I like using the non-trigger wjeel tdi cranks fromthe earlier engines like the 1y/1z because they are symetrical. Easier to machine and balance up if you're into that type of thing. If not the later trigger wheel crank will do just as well
     
  7. i_am_me Forum Member

    Joined:
    Jun 23, 2012
    Likes Received:
    0
    Location:
    riby
    if i did it would it be ok to use a head spacer to drop the compression?
    mines at 12 bar already so it will need dropping a bit.

    also when you say the piston will stick out 1.35mm more do you mean it would be above the face of the block?

    as a side thought would a spacer plate be ok to give enough clearence for the pistons?
    two birds one stone kind of idea lol
     
  8. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    148
    Location:
    Southwest
    If you go to a true 2.1 and overbore to 83.5mm the std type MLS gaskets have an 83.5mm bore also, so you cant really have the pistons more than flush, tho Martin may have done them where they just clear...which means a massive squish clearance of 66-68 thou of the gasket thickness...almost double the ideal clearance.

    Dont use spacer plates...you'll have massive squish clearance again...it's even wrong on turbo conversions but people do it.

    There is an 85mm Cometic gasket available which will cure that issue, but not cheap. As Martin said, sticking to the std bore wont be an issue, you'll get the benefits of the extra torque the longer stroke will give...though small for the effort...but it wont be a true 2.1.

    You could go 83mm to make it 2066cc and use a std MLS gasket.

    With an 8v tho it'll be massively undervalved for the capacity...ported or not...tho on either bore size...82.5 up, you'll have plenty of room for big valves.

    A std digi head is'nt better no...though you'll need to match the head & inlet manifold depending on the car/injection system...MK2 digi & MK3 arnt the same.
     
  9. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    For someone who does not like the "nah mate yah wrong" attitude, explain how this is "wrong" in turbo applications. If you do have expereince with force inducted applications, can you state the undesirable effects so called less than ideal OEM squish would cause to the combustion process and how do some manage to migitage the undesireables? By "some" I do mean not only VW but modified + boosted Nissans, Mitsubishi, Toyotas, Honda etc.

    This is not indended to have a go at you personally, but would like more technical detail as to why you would have such an opinion.
     
    Last edited: Jul 12, 2012
  10. mitlom

    mitlom Forum Member

    Joined:
    Jun 20, 2006
    Likes Received:
    95
    Location:
    Ripley, Derbyshire
    My understanding of the squish zone is to compress/force the air/fuel mix towards the spark plug and while doing so it causes more turbulence within the mixture which in turn promotes a faster flame front propogation. Without this feature, in an engine designed for it, you would get a slower burn rate and the opportunity for detonation would therefore increase. Some engines are designed with port geometry that generates a far greater amount of tumble and swirl which in basic terms has a similar effect. This is a very simplistic view as there are other things that can effect it if my memory of fluid and engine dynamics is correct....need to dig out all my Uni notes and refresh my failing memory ;)

    I suspect what MrHillclimber was eluding to was that the engine type being discussed has geometry designed to work with a squish zone and by eliminating this by use of stacked gaskets or spacer plates may introduce a propensity for detonation, which is not a good thing. Clearly this does not mean that all engines require a squish zone as indicated above. HTH :thumbup:
     
    Last edited: Jul 13, 2012
  11. Mike_H Forum Addict

    Joined:
    Oct 16, 2004
    Likes Received:
    17
    Location:
    iQuit
    You can build a 2.1 8v if you want, but I think there are better ways to spend your money....

    For example, in the engine department, stand alone management to get the best out of the 2.0 with cam and ported head, or a 2.0 16v conversion instead of the 8v.

    In a fast road state of tune, I'm struggling to see a big advantage from an extra 60cc (if you stay standard bore) compared to all the aggro you have to go to to achieve it. I think there's better ways to get another 5 bhp. On a higher spec engine that breathes better, then the cost of getting more power elsewhere might change the balance.

    Did my old Jetex exhaust die yet?? [:D]
     
  12. newkid

    newkid Forum Member

    Joined:
    Nov 17, 2006
    Likes Received:
    0
    Location:
    Toton, nottingham
    You put a good point across with that Mike. The effort involved in the little power gain seems like one of them things you do to say you've done it etc.
    The main reason i considered this route was to save ripping out wiring etc and have a quick engine swap again due to time restrictions.
    Quite what engine swap I'll do yet I'm not too sure. Would like a VR6 but from what i can gather a good mildly tuned ABF can perform in the same kind of way? I'll see what mine performs like when I've put this head etc on it before making a definite decision.

    The old Jetex is still going with no signs of failing yet. It must be getting on for 12 year old now?
     
  13. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    Turbocharging was mentioned as per my quote.
    The lack of squish/quench would not be the root cause of detonation and yes can sometimes lead to improper or poor combustion. If the squish clearance was increased, there are the chances, the remaining end gas in the pockets of the squish zone can cause localised hots spots auto ignite, which can lead to PI and possibly DET if control parameters are not calibrated to mitigate . To reduce in cylinder heat you may need to calibrate more fuel to cool the cylinder (away from max torque AFR for that engine) or back spark timing off away from MBT to reduce the cylinder pressure and in turn manage in cylinder heat heat. This reduces optimum engine torque and increases BSFC. Alternatively you can coat the top of the pistons (expensive) to minimise hot spot generation.
    It is something many of us turbo guys have to think about when stacking MLS jobs or spacers ( as per VR6T) are used or in the case of my JDM competition using a thicker gasket from the likes of HKS, Tomei etc.

    How this relates to the "2.1" 8v?
    A NASP engine is likely to suffer more performance loss with incorrect quench area because of the actions that would have to be taken to protect the engine than a turbo charged vehicle and of course there would be differences between those engines that tumble the mixture in as per 16v and those that swirl i.e. 8v.
    This topic could also be an area of research if there was enough time and resource i.e. what levels or quench are required to support optimum combustion and torque development or at what quench clearance does combustion, BFSC start suffer and so on.

    ....DOE anyone?


    I also agree it would be not be best to simply add gaskets with a fixed thickness to deal with the concerns stated above re pistons sticking out 1.35mm on a "2.1" and agree either a custom head gasket job, that would maintain OE squish unless alternative squish is suggested with supporting fact, or with the comments from cerips.

    Mike H also make a good suggestion re the whole "2.1" idea.
     
  14. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    Newkid, Have you considered optimising you existing 2E w/head and 272 cam with any SEM controller. It still would mean some minor wiring changes.

    Here is a similar spec'd engine that was recently tuned.

    Before with Digi controls

    [​IMG]

    After with SEM (Megasquirt)
    [​IMG]

    You can use any SEM by the way and deliver the same performance increase.

    That flat torque is the same as an semi stdish ABF digifant just that it occurs from much lower engine speeds.

    This can also be an option.
     
    Last edited: Jul 13, 2012
  15. mitlom

    mitlom Forum Member

    Joined:
    Jun 20, 2006
    Likes Received:
    95
    Location:
    Ripley, Derbyshire
    Eddie maybe I'm getting confused or you are about what I posted....I was saying that you need the
    squish/quench and that by increasing this it could introduce a detonation failure mode.

    You say the lack of squish/quench would not be the root cause of DET and then in the next sentence appear to say that if this squish region is increased it could cause DET due to localised hot spots but that this could be eliminated by decreasing the in cylinder temp by adding more fuel or retarding spark by means of the calibration....surely this means that it would be the root cause?? I'm not meaning to pick holes but rather just asking for clarification as I'm a tad confused and it's been a few years since my Auto Eng days at Uni and my days at Dunton.....
     
  16. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    No it is fine. If I was not clear then I am happy to explain.

    I said the endgas can cause pre ignition (PI) which can lead to detonation. PI is not detonation.
    To reduce the chances of hotspots you can add more fuel richer than max torque lambda and cool the cylinder/piston crown down. If the cylinder pressure is already very close to knock you can reduce timing and further increase BSFC. You can see how this would have more adverse effects on a NASP swirl type engine than on a turbo unit that may have already twice the torque as a base NASP unit with a spacer.. I am assuming all cases would be fitted with an adjustable SEM of some sort and are setup up away from det.

    Make sense?
     
  17. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    No it is fine. If I was not clear then I am happy to explain again.

    I said if the quench area is increased as in the use of a spacer, thicker gasket etc, endgas can cause pre ignition (PI) which can lead to detonation. PI is not detonation.
    To reduce the chances of hotspots you can add more fuel richer than max torque lambda and cool the cylinder/piston crown down. If the cylinder pressure is already very close to knock you can reduce timing and further increase BSFC. You can see how this would have more adverse effects on a NASP swirl type engine than on a turbo unit that may have already twice the torque as a base NASP unit with a spacer.. I am assuming all cases would be fitted with an adjustable SEM of some sort and are woulod be calibrated up away from det to produce a torque curve without failure.

    Make sense?
     
  18. mitlom

    mitlom Forum Member

    Joined:
    Jun 20, 2006
    Likes Received:
    95
    Location:
    Ripley, Derbyshire
    Yeah basically the same as what I said....that having a larger than optimal squish/quench zone can cause DET, but as you correctly say that the DET would be caused by the PI....whatever way you put it the end result would be DET unless you calibrate it out.
     
  19. Mike_H Forum Addict

    Joined:
    Oct 16, 2004
    Likes Received:
    17
    Location:
    iQuit
    I think the difference is more marked on a higher spec engine - like Hotgolf's mad 2.1 16v lumps. On a fast road spec 8v I'd expect it to make less difference. Both myself and G60KG have got around 10% more power going to a megasquirt ECU from Kjet in my case, and digifant in his case. Totally up to you which way you want to go with it though.


    It was late 2001 I scrapped the Alfa 75 and bought a Golf, then I think it was March 2002 I put that Jetex on my golf, and probably 2003 I welded up the rear hanger (badly) when it broke. I fitted the exhaust lying in the street in Edinburgh, in March, with a hangover, while up north for a Rugby international. Wasn't the most fun job I've ever had to do, but at least it wasn't snowing... just a light dusting of hail at one point [:D]
     
  20. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Joined:
    Jul 26, 2006
    Likes Received:
    3,320
    Location:
    Creating Pfredstarke
    [
    I not sure it is the same sentiment as we maybe coming from different schools of thought on the topic.
    Hotspots do not always lead to PI, PI does not always lead to detonation.
    Also there are different levels of det. Some intensities that the engine will tolerate and others that can be very destructive. So not all detonation leads to failure either. Det events, once detected, either when mapping or in service, should be acted on by cutting back spark on the calibration a few degrees of BLD or by the use of a robust knock feedback system, much out of the scope of most DIY tuners.
    During mapping (after market devices) you tend to calibrate the engine away from knock as listened to in det cans under both steady state and transient conditions so the chances of PI promoting a destructive det reduced and you get whatever torque/tractive effort for that setting and condition.
    Having mapped quite a few engines now including 4 cylinders 2.0litres with 500PS + with thicker head gaskets, I am yet to have an engine fail in service because of increased quench from OE settings. In fact there have been times the reduction in CR and the corresponding increase in quench in such a case raises the border line det levels of the engine to above MBT, allowing more torque for a type of fuel RON.
    So regarding spacers used on NASP motor converted turbocharged (eg 16vT, VR6T etc)the engine will be more inefficient yet certainly more powerful than 'stock' compared to one converted with more expense pistons maintaining the OEMish quench area.

    Regarding the OP "Newkid" on pistons that protrude 1.36mm above deck on a "2.1", I would say it would be safe to machine to crowns to maintain OE clearances to std MLS gasket thickness, or use a custom spacer to maintain the OE clearance w/o piston machining.

    But then again do consider what a custom calibration can do to what you already have 2E w head and 272 cam. This may well exceed your expectation without swapping to 16v fury.


    As always discussion like this is good thing...:thumbup:
     
    Last edited: Jul 14, 2012

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice