with the ITR head (coded as a PR3 head like the b16a and b17a and is just a b16a head that has been ported by Honda), you would have a different flowing head (60% less drag than the b18c1 head) with a higher head volume.
The ITR head volume is 42.7 cc compared to the GSR head at 41.6 cc...
If you have GSR pistons,.. this larger head volume would lower your static CR to 9.6:1....
The ITR head uses a single stage intake manifold (IM) and the intake port is a larger with steeper valve angles. It has less aerodynamic drag from having less internal surface area than the GSR head and GSR 2 stage IM. Therefore the flow quality is much better on the ITR. The intake port angle of approach into the combustion chamber is less vertical (you'll hear people say : less of a
"straight shot" into the chamber than the GSR head). The GSR head's ports are said to be "straight shot" or more vertical or steeper). The ITR head will make more top end power at the sacrifice of some midrange, since it has these characteristics compared to the GSR head attached to the GSR 2 stage IM.
This changes, however, when you add a single stage IM and bigger cams however on the GSR head...
Lower head volume in the GSR head....finds that it works well with dished pistons in FI applications whereas the ITR head's larger head volume works well in N/A high hp motors using domed pistons that fill in the volume. :wink:
Ok... Here is a stock (unported) Civic b16a head (so it's not really an ITR head but you get the idea) compared to the GSR b18c1 head on a flowbench which only measures flow quantity and does not account for
flow quality:
Notice that the unported b16a (PR3) head is the same in terms of flow volume compared to the unported b18c1 (P72) head...and it's not as dramatically better as people make it out to be. However the ITR head (a ported b16a head with "intake port bowl-blending" and modified valve angles) compared to a ported GSR head shows it's advantage at the upper rpms.
of course, you can have the GSR head ported & polished to flow better than an ITR head and use the Skunk2 single stage IM made to fit onto the GSR head to get the same effect of having less surface area and flow drag leading to better flow quality and more power at the
upper rpms.
The ITR and GSR have the same identical rod ratio and so the port sizing for headporting would be similar. They both like long duration cams for N/A packages for the same reason....
PR3 : 89-91 JDM B16A EF8/9, 96-00 OBD-2 Integra Type-R (JDM ,Euro, Asian, USDM)
PR3 - J00 or J51 : 92 JDM Integra B16A EF8/9
an ITR head is a ported B16A head from the factory. So they are the same head but the ITR one has had better intake valves, stiffer springs, bigger cams, bigger LMD's, bigger ports, steeper valve angles, some bowl blending work done from the factory.
Ways to identify an ITR/CTR head
* the green paint by the distributor
* thinner ITR intake valve
* minor port work by the valve seat in the ports
* dual valve springs on both sides, notice yellow paint on intake side, blue on exhaust side
* lost motion assembly has a blue dot