I am currently doing an FE engine swap- I am replacing a carbed 1987 Honda 1.5 L CVCC 9.2:1 compression ratio with a carbed 1987 Honda CVCC 1.3 liter 10:1 compression ratio (it came stock with this high compression ratio- and there was no recommendation for premium fuel).
So- I have the choice of using the 1.5 liter exhaust manifold (the top on in the pic) or the 1.3 liter manifold.
The 1.5 liter manifold is internally divided into 4 runners for the first 3-4 inches and then each pair converges and finally the two converge just above the cat.
The 1.3 liter manifold is not internally divided so that two ports immediately converge and then of course both sides converge. The area of the 1.3 runners is a little smaller than the 1.5 runners as well.
I would guess that Honda sized the manifolds according to best performance, but which do you think I should install for the best FE?
By the way- the 1.3 liter did not come with an oxygen sensor- hence there is no hole in the manifold for one.
1.3 no internal dividers
1.5 internally divided for the first few inches
Which should I install for FE?
I know the 1.3 will keep the exhaust flow faster because its passages are smaller, but the 1.5 has the internal dividers that may act like mini headers... so it seems almost like a tie- anyone out there ever seen an HF manifold to tell me how Honda designed those? How is the VX manifold set up?
if theyre interchangeable and from the same year, i would imagine that honda would have looked into this. they also would have saved money by only using 1 manifold on 2 engines. which would seem to point to the idea that honda did look into it, and thought it best to use a different design for each engine. unless you get some good opposing info i'd keep the 1.3 manifold on the 1.3 engine