I resently blew my 91 b18a engine and bought a new engine but this one says it’s a b18a1 dose this mean one is from japan and which one is which
jdm engines are not labeled with numbers and i dont think the b18a is in japan, only the b18b which is b18b1 here i believe, b18a1 is usdm
so then both are usdm? why the difference in numbers??? no difference then, eh? there is one less smogg “thing” on the b18a1 intake manifold too.
b18a is obd0 (90-91) and b18a1 is obd1 (92-93) the b18a1 has 10hp more if the obd1 ecu, b18a1 intake and exhaust manifold, and b18a1 cams are used…b18a = 130bhp, b18a1 = 140bhp
I have both OBD-0 and OBD-1 B18’s in my garage right now. I took some measurements and made some observations…
OBD-0 and OBD-1 intake manifolds have the same size runners, 1-15/16" across. So, I doubt the IM will make a difference.
The OBD-1 head has intake ports that are 3/16" larger than the OBD-0 head. That is a big difference. Also, the OBD-1 cams are different.
The OBD-0 has different exhaust manifold than the OBD-1.
His motor having one less emission “thing” on it is probably because it is missing the EGR???
It’s my opinion that most of that extra 10 hp is made withing the head and exhaust of the OBD-1 motor. Maybe the OBD-0 IM and ECU are slightly different than the OBD-1 parts, but I can see clearly that a OBD-1 motor will make more power with a OBD-0 IM and ECU.
My 91 has the B18a1 and it’s the original motor. :shrug:
my 90 has a b18a1???
every 90-91 teg i saw had a b18a…my part cars are 90’s and they have the b18a…i know about 6 guys with 90-91 tegs, all say b18a on the block…me, my brother and one of buddies have 92 tegs, and they are stamped b18a1 (well my former engine, no longer have a b18a1)…and i saw somewhere that that’s how the codes work, seeing as the b18a1 would be the second generation of b18a…they couldn’t call them both plain and simple b18a if they are not the same thing? if somebody else has heard of the same thing, let me know…im not saying i know for sure thats what it is, but i saw with my own experience, and in general on the net saw something about this a few months back
All 90-93 blocks should say B18A1. I have a 90 B18A1, a 91 B18A1 and a 93 B18A1 sitting in my garage. Basically, 90-93 blocks are the same. The 10hp more 92-93 motor has it’s changes mostly within the head, IM (supposedly) and the exhaust (definitely)
what the hell is a b18a? lol…i swear i seen many of them…i didnt get it either…weird…
I just went out to my garage and confirmed that both the 90 and 91 B18A1’s are stamped as “B18A1”. They have “90” and “91” date codes on their heads. The 90 Teg was a unmolested, perfectly stock AT car that was never swapped in any way.
I thought I’ve seen B18A also before. It may be possible, but officially I think you they are all B18A1. I think for these motors, B18A1 only represents the block, and not the generation of motor.
sorry my bad…i know i saw the b18a before though…dunno what’s up with that, thanks for correcting me guys, i sounded like an ass there for a while 
well thanks for the info i think that the one i got is a newer one, idk. i am gonna get new pistons, cams, im & exhaust anyway, but this will forever make me say wtf.
you’re not alone. but good luck with your projects dude, can’t wait to see how it turns out :rockon: i got a little project of my own coming along, crVTEC…which means i will have a p8r head for sale this winter :bowdown:
I’ve seen this too. It’s what happens when the 1 gets covered with all of the engine grime. Both of mine did that. 
man i just got owned…holy shit i just sounded totally n00b right there, please forgive me lol…been coming on this site for like 5 years, only been a member for a few months…=P