CTR and ITR Pistons

[IntenseDriving00]

Does anyone know the compression ratio if I was to install CTR Pistons in a GSR or ITR Pistons in a GSR. I was told that if I was to install CTR pistons in a gsr the compression would only raise to 10.8:1 and that ITR Pistons would only raise the compression ratio to 10.4:1? Thats just what I was told from a guy at a machine Shop. Is that right I hear different stories from different people.

[2ndGenTeg]

CTR pistons in a B18C = 11.8 +
USDM ITR pistons in a B18C = 10.8-10.9
JDM ITR pistons in a B18C = 11.3-11.4

[cashizslick]

that's interesting, the ctr pistons make higher compression

[ChrisCantSkate]

cause its designed to be in a b16, not a b18. different bore x stroke

[ebpda9]

if thebore is different how are you gonna use the pistons ? :crazy:

[IntenseDriving00]

Between the B16B, B18c5, and B18c1 the block height is exactly the same the rods and the pistons on the ctr and the itr r exactly the same as well as the block height. The only difference is that the CTR pistons have a higher c/r than the ITR. The rod bearings on the CTR, ITR, and the GSR r the same width so all you have to do is change the pistons. The GSR's c/r is 10.0:1, CTR is 10.8:1, and the ITR is 11.1:1...also remember that the CTR is still a 1.6 while the itr and gsr is a 1.8. You can still use the CTR pistons but the c/r will be higher than the ITR that is what I found out. I also found out that having CTR Pistons with CTR Cams in a gsr will bring the C/R to about 12.2:1 or so and the ITR with CTR Cams will raise it to about 11.7:1. I called Inline Pro and they informed me about it the C/R for that set up.

[2ndGenTeg]

With a shorter stroke, you have to use a higher domed piston to get the same CR. Remember what CR stands for- compression ratio. If the stroke is shorter, the volume in the combustion chamber with the piston at TDC has to be less to accomodate the difference- hence the higher dome on the CTR piston. Since the pistons are interchangeable, swapping the same piston into an engine with a longer stroke results in a higher CR. This is also why the ITR pistons starts with a higher compression in its stock motor and ends with a lower CR in the same motor, when compared to the CTR- the ITR has a longer stroke.

Keep in mind this also changes with the head you use, since the combustion chambers have different volumes from one head to the next. Finally, which cam you use has no impact on the CR.

[Dr Drew]

The B16 and B18C5 heads are the same core. They have about .2 less CR than a C1 head in the same given application because there is more combustion chamber volume. Cams have nothing to do with the static compression ratio. Although, a longer duration cam such as the B16B cam (243 degree) will bleed off more compression at overlap than a cam with less such as a B16A or a B18C1 with 230 degrees. That is one reason that higher compression goes hand in hand with long duration cams. Effective CR varies under engine load and RPM.