My Si has a DX motor!
 

I think I posted about this when my timing belt was changed a couple of
years ago; the short version was that my usual mechanic told me after
he'd finished the work that he thought my 90 CRX Si had a 1.5L engine
instead of the usual 1.6, because the timing belt for a 1.6 didn't fit,
but the belt from a 1.5 did. He claimed to have called a friend at a
Honda dealer who told him that 1.5L engines had been installed in some
Si models. I asked around, but was never able to find anyone else to
confirm this, and since the car was running well, I eventually just
chalked it up as a curiosity.

Fast forward to several weeks ago, when I had (among other things) what
I thought was a leaking rear main seal looked at, but which turned out
to be a leaking oil pan gasket. In the process of trying to confirm
where the leak was actually originating, the dealer where I had the work
done cleaned off a fair amount of the gunk that had accumulated on the
various surfaces of the engine.

Yesterday I was poking around under the hood while attempting to change
a burned-out low beam, when I happened to shine a light on the front of
the block, and there it was, plain as day: D15B2, otherwise known as the
motor used in DX models. Sis of this vintage are supposed to have a
D16A6. The difference is a longer stroke, slightly higher compression
ratio, and, depending on who's counting, between 15-20 horsepower.

I bought the car from an Acura dealer in 1992 with roughly 20K miles on
it. I have no idea whether they knowingly sold me the car with a DX
motor, or whether it came to them that way and nobody noticed it before
it went out on the lot; it's not exactly a difference that's easily
spotted visually unless you examine the stamp on the block. But either
way, I'm not too pleased. I've been thinking more and more about an
engine swap lately, but the reality of taking that path is that it'll
cost a lot more for me to do that than it would to be patient and keep
my eyes open for a reasonably clean, non-riced CRX that's already had a
B16 swapped in by someone who knew what they were doing.

Dave