I recently did a swap on my 2000 civic si and put in a B18C JDM GS-R motor using my old B16A2 ECU, after about 6500RPM the car slows down considerably. I had a couple trannys put in as well as some gears swapped out when my tranny was having problems but i dont think it could be gear ratio's, i think its the ECU making it run lean or rich, if anyone has any ideas or suggestions please post, thank you.

 

chip ecu

 

Your using the b16a ECU on a GSR? The GSR has a dual stage intake manifold controlled by a secondary runner in the manifold. They are opened by the ecu. There is a sensor under the Intake manifold that controls this. If your using the GSR Manifold you have to use the GSR ECU or they wont open creating a restriction in air flow.

 

Thats what they tell me, i actually hooked up a p72 obd1 with a mugen chip today and it didnt help the long range after 6500 but the guy at the shop drove my car and said i had an ls tranny which has long gears so thats why it slows down after 6500rpm?