d15b usualy refers to the JDM 1.5 liter with the vtec p08 head or the later 3 stage vtec head.
D15b1,2,6,7,8, refers to the USDM varients found from 1988-95.
all made varying power due to intake/cam/ECU/exhaust and intake manifolds/pgmfi system/ and overall "factory tuning" they all had the same head(pm3 or pm6 cast) except for the 8v varients(which would effect power output) found in 88-91 "econo" models.
*see below (taken from SOHCHonda.com archives)
-D15B1
1.5 8V SOHC PGM-FI 1493
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'88-'?? Civic (note, there has been found to be a 16v late 91 model year d15b1 stamped motor. i know because i have one)
-D15B2
1.5 16V SOHC PGM-FI 1493
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'88-'91 Civic DX/LX (USDM)
-D15B6
1.5 8V SOHC PGM-FI 1493
[email protected] [email protected]
'88-'89 Civic/CRX HF (USDM)
-D15B6
1.5 8V SOHC PGM-FI 1493
[email protected] [email protected] '90-'91 Civic/CRX HF (USDM)
-D15B7
1.5 16V SOHC PGM-FI 1493
[email protected] [email protected]
'92-'95 Civic DX/LX (USDM)
-D15B8
1.5 8V SOHC PGM-FI 1493
[email protected] [email protected]
'92-'95 Civic CX (USDM)
all use the same bottom end however from the crank up to the deck (except for the pistons in the 8v motors which saw that some came with 2 valve reliefs pistons and other 16v reliefs depending on how honda felt the day of production.)