K24 Test Engine Part 4
Those of you that have been following our endeavours with the K24 engine will remember that we are currently at 272hp and 200ftlbs, and although we have carried out a number of changes above the head gasket, the bottom end remains completely stock with the exception of a PRB oil pump.
By our calculations the stock RBB head is just about ‘tapped out’ at this power level with respect to airflow, so the time has come to swap the RBB cylinder head for the better flowing PRB head which is commonly found on the K20A2 engine.
Whilst we were swapping the head, we took the opportunity to fit some more suitable valve springs for the cams as the previous tests were carried out with the factory PRB springs. You can purchase the very same springs from our website here:
After recalibrating fuel, ignition and cam angle in the Hondata Kpro the results can be seen in the graph below:
PRB head in blue
As at end of our part 3 test shown in red
Not too bad but our calculations would lead us to believe that the additional airflow from the PRB head should result in more power than this. After some head scratching we decided it was time to revisit the trusty inlet manifold parameters. A small change in plenum volume resulted in nearer what was expected, see below:
It’s worth pointing out that if the compression was raised to something more suitable, we would expect each of the current changes to net larger power increases, and from here on in to get to the magic 300hp will become increasingly more difficult.