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Ed Wright · 07-06-2008, 07:33 PM

Art, your air/fuel ratio will look extrememly lean at lower RPM, due to fresh air being pulled back in the collector during overlap. You need to put a muffler, or at least 18" of collector extention to know what the actual air/fuel ratio is at idle, on the converter, and launch. Once you get that dialed in you can remove it to race it. Be sure, if you are going to run it in closed loop to set the min RPM for closed loop fuel corrections higher than the RPM you will stall it on the converter. Otherwise the ECU will be pouring the fuel to it down there to try and correct what it assumes is an extremely lean air/fuel sistuation with the exhaust extention gone. If you can put a bend in the extention, that would be even better for the initial low RPM air/fuel tuning. I no longer run my FAST in closed anyway.

Good luck, Ed

07-06-2008, 07:33 PM	#5
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 389 Times in 168 Posts	Re: ECU Help??? Art, your air/fuel ratio will look extrememly lean at lower RPM, due to fresh air being pulled back in the collector during overlap. You need to put a muffler, or at least 18" of collector extention to know what the actual air/fuel ratio is at idle, on the converter, and launch. Once you get that dialed in you can remove it to race it. Be sure, if you are going to run it in closed loop to set the min RPM for closed loop fuel corrections higher than the RPM you will stall it on the converter. Otherwise the ECU will be pouring the fuel to it down there to try and correct what it assumes is an extremely lean air/fuel sistuation with the exhaust extention gone. If you can put a bend in the extention, that would be even better for the initial low RPM air/fuel tuning. I no longer run my FAST in closed anyway. Good luck, Ed __________________ Ed Wright 4156 SS/JA