Were still awaiting official confirmation on just what block the 1.5T uses, but based on preliminary information it seems to be shared with the L-series.
JeffX from TOV spoke with Honda engineers at the Civic launch a few weeks ago, based on his conversation and observations he wrote:
"the tag on the side of the engine was obstructed so I don't know if it's called an L15 or whatever but it is clearly based upon the geometry of the L15, using the same stroke, same bore spacing, etc. It is a completely different engine from a parts perspective though. [email protected], 162 [email protected]"
Granted the observations of one man, no matter how reliable they have proven to be in the past, are not conclusive. So we went looking for something to somewhat substantiate his claims.
We found it after looking for and finding a full technical breakdown of the 1.5T as used in the not-for-here Jade RS which debuted back in May of this year.
The paydirt comes from the bore and stroke, the 1.5T is listed with a 73.0 mm x 89.4 mm bore x stroke. Comparing those with the Honda L Engine Wikipedia page we find only one engine that fits the criteria. The L15, just like Jeff said.
Now the L15 has a long and storied history within Honda, having been around in some form or another since 2001. We believe the most logical block choice is the L15B Earth Dreams which debuted with the latest GK5 Fit.
There are other derivatives of the L15 that live in the SE Asian HR-V and Jazz, but the L15B with its status as global engine seemed most appropriate.
None of this is terribly scientific or official, but it does come based on good information and a willingness to connect the dots. Remember where you heard it first, the 1.5T is an L15 at heart!