d15 to d16 manifold question

[Shawk]

I swapped from a d15 non vtec to a d16 vtec, the manifold went from 4-1-1 to 4-2-1 but I'm using the 4-1 manifold right now because I don't have a down pipe for the 4-2.

How much does this effect my performance? the d16 is running at about 160-170 compression (108k on d16,) and it just seems no better than the d15 non vtec I just had in.. and driving it on the highway I could not pass 170 km/h with my foot completely to the floor for a good 5 minutes.. I could get to 220+ km/h with the d15... and it had 350,000 clicks on it and horrible compression.

I'm getting a Header soon but I was just curious if this is my main problem right now performance wise. Thanks.. sorry if covered already.

 

[rocknwood]

Hey, here is my experience on this one: '93 Civic DX hatch (D15B7) with a '92 Si (D16Z6) ex. manifold made a noticeable difference. I also had the entire Si exhaust on this DX with a cone filter on the other side. The DX and Si hatchs have about everything lining up identical, so you can swap away with better flowing parts. If you were to lay all these exhaust parts side by side, all openings on the Si are a larger diameter. In my opinion, just buy the header, and put it on. Then get ready to experiment. I have built a couple '92 Si's that will fly with that D16Z6, and still get 40 mpg on the highway.

 

[meanmugen]

what ecu are you running? did you wire for vtec?
Nevermind