Hey guys, would a B18B1 stock ECU adjust for forged 9:4 compression pistons. The stock compression on a B18B1 is 9:2. I assume the ratio change is negligible also considering the stock pistons had built up carbon adding to compression anyway. I thought i'd ask some pro's on here before I start the car, run lean and hate myself. I am trying to avoid a tune and drive the car for a bit.

 

No, the stock ECU cannot adjust for increased compression. Idle and light part throttle operation will likely be ok to drive and the stock ECU closed loop operation will add fuel to compensate enough to keep the engine out of danger, but it cannot alter the fuel and ignition maps for full throttle operation.

So, take it real easy until you can get it tuned.

 

Thanks JRCivic1, In that case I'll probably only start it and let it idle for a bit to somewhat break in the piston rings.