Section : Engine

2.5PI Engine Internals

Posted By : Mark Stradling, 25-Apr-2005, 10:46am

• 2.5PI Engine Internals

  Posted By : David Thompson, 25-Apr-2005, 05:54pm

  The 2.5l and 2l have different cranks and pistons (the 2.5 is basically a stroked 2l). In addition the combustion chambers are deeper on the 2.5l to give the correct compression although I believe that you can use a late (domed piston) 2l head on a 2.5.
  
  Also watch out for long and short rear on the cranks. The long one uses a recessed flywheel.
  
  With regard to how much power a standard con rod will take that really depends on how many revs you intend to use, the actual use you intend for the engine etc. They should take 200 BHP if you crack test, balance and shot peen them. Don't forget that it's more likely that your rod bolts will let go so make sure you use Cosworth (available from Burton Power) or ARP. Also a contributing factor to bottom end reliability is to ensure all rotating assembly is balanced and blueprinted.

  • 2.5PI Engine Internals

    Posted By : David Rumens, 25-Apr-2005, 06:39pm

    Yes you can use the 2 litre domed piston head on the 2.5 litre engine.
    
    

    • 2.5PI Engine Internals

      Posted By : John Davies, 25-Apr-2005, 10:30pm

      It's not that you 'can', that's why they exist.
      
      For the GT6 Mk111, Triumph rationalised their range and realised that a dome would allow the 2.5 head to be used on 2000/GT6 engines without the expence of milling off height. However, use a domed piston with a 2.5 crankshaft and you have a 2.5's cylinder with a 2 litre chamber. The CR rises to, from memory, about 13.
      
      I'll do the equation another tiem, it's late.
      
      JOhn
      
      

      • 2.5PI Engine Internals

        Posted By : Mark Stradling, 27-Apr-2005, 10:54am

        My cunning plan is to strap an Eaton M45 supercharger off of a Mini to a GT6, swapping to electronic fuel injection in the process - so nothing too ambitious!
        
        If the internals of the 2.5PI are _basically_ the same as the smaller engines, then they should be able to take the same BHP as the 2.5PI produces without any major worries.
        
        For this combination a head/piston combination that lowers the compression ratio is actually a plus.
        
        By the sounds of it, 150BHP shouldn't be too much of an issue (for the engine - 50% extra over a stock GT6 will obviously require serious attention to the drive train).

        • 2.5PI Engine Internals

          Posted By : Jonathan Binnington, 27-Apr-2005, 06:09pm

          my suggestion for uprating the transmission is to swap from the gt6/vitessse gbox to the bigsaloon/tr6 gearbox
          
          not an overnight swap but perfectly doable and cheaper than a T5 or type 9 swap
          
          jonath