a ek9-r only has 10.8 compression while dc2-r has 11.1

but when you put ek9-r pistons in a dc2-r, the compression goes up to 12:1+

i thought the ek9-r is pretty much a destroked dc2-r? what makes the difference in compression?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EG type GTR &raquo;</TD></TR><TR><TD CLASS="quote">a ek9-r only has 10.8 compression while dc2-r has 11.1

but when you put ek9-r pistons in a dc2-r, the compression goes up to 12:1+

i thought the ek9-r is pretty much a destroked dc2-r? what makes the difference in compression?</TD></TR></TABLE>

The CTR uses different pistons than the ITR.

 

compression heights are different, rods are different lenghts and cranks

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EG type GTR &raquo;</TD></TR><TR><TD CLASS="quote">i thought the ek9-r is pretty much a destroked dc2-r? what makes the difference in compression?</TD></TR></TABLE>

It is, but in the process of destroking, the rods also must be changed. Otherwise the piston height will drop away from the head & compression will be WAY low. Since the rods & pistons must be different, Honda had the option to choose exactly how they wanted to do things (rod-stroke ratio, compression height, wrist pin location, etc). You'll have to ask them why they decided to choose that particular compression ratio though...

Does anybody know the rod lengths for both of these motors (B16B & B18C-R)?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EG type GTR &raquo;</TD></TR><TR><TD CLASS="quote">but when you put ek9-r pistons in a dc2-r, the compression goes up to 12:1+</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">The CTR uses different pistons than the ITR.</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Freshazzburu &raquo;</TD></TR><TR><TD CLASS="quote"> </TD></TR></TABLE>

What is this face for? The original poster sounded as if he didn't understand why CTR pistons yielded higher compression in a B18C5, because he "thought the ek9-r is pretty much a destroked dc2-r". From reading this comment, it isn't clear whether he was/is aware that the pistons in the CTR are not the same as those in the ITR, and quite clearly, this is why they yield a higher compression ratio.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">What is this face for? The original poster sounded as if he didn't understand why CTR pistons yielded higher compression in a B18C5, because he "thought the ek9-r is pretty much a destroked dc2-r". From reading this comment, it isn't clear whether he was/is aware that the pistons in the CTR are not the same as those in the ITR, and quite clearly, this is why they yield a higher compression ratio. </TD></TR></TABLE>

That was my uncertain face LOL. I didn't know if you read past him saying what i quoted that's all. &lt;-- i can use that face now

 

The increased compression is the result of a longer stroke.

Static CR is the ratio between cylinder volume and combustion chamber volume. Both the B16B and B18C-R have the same combustion chamber volume, but the B18C-R has greater cylinder volume, thus yielding a higher static CR.

The CTR piston has a larger dome, which means that when you put CTR pistons in a B18C, you are effectively reducing combustion chamber volume at TDC. This is why putting CTR pistons in a B18C yields a higher CR. However, the larger dome on the CTR piston is not enough to compensate for the greater cylinder volume of the B18C, and that is why the CTR has a lower static CR than a B18C-R despite the fact that the CTR piston has a larger dome.