ZR-1 Net Registry Forums - View Single Post - For tuners, a Holy Grail of Injector voltage Offset

Marc Haibeck · 11-24-2013

I think that a large factor in bank to bank difference in fuel trim at idle is the use of headers. With headers only two cylinders per bank fire across the oxygen sensor. Maybe because the system has only half of the normal gas samples, the average is not as accurate. The OE manifolds have the primary tubes shaped so that the gas from each of the cylinders jets across the oxygen sensor. The deflectors can be seen if the heat shields are removed from 1990 - 1992 OE manifolds. I observe bank to bank difference of up to 15 fuel trim counts on about half of the engines that have headers and no other modifications.

I have observed that when warmed up from cold, as the coolant temperature goes past 170 degrees, about half of the totally stock engines will swing in and out of learn mode at low loads. If the engine is run at full load to 7000 rpm in second gear a couple of times the system will stay in learn mode. I have not observed any effect on drivability on an engine that is switching in and out of learn mode. It may be important during an emissions test.

11-24-2013	#50
Marc Haibeck Join Date: May 2007 Location: Addison IL Posts: 252	Re: For tuners, a Holy Grail of Injector voltage Offset I think that a large factor in bank to bank difference in fuel trim at idle is the use of headers. With headers only two cylinders per bank fire across the oxygen sensor. Maybe because the system has only half of the normal gas samples, the average is not as accurate. The OE manifolds have the primary tubes shaped so that the gas from each of the cylinders jets across the oxygen sensor. The deflectors can be seen if the heat shields are removed from 1990 - 1992 OE manifolds. I observe bank to bank difference of up to 15 fuel trim counts on about half of the engines that have headers and no other modifications. I have observed that when warmed up from cold, as the coolant temperature goes past 170 degrees, about half of the totally stock engines will swing in and out of learn mode at low loads. If the engine is run at full load to 7000 rpm in second gear a couple of times the system will stay in learn mode. I have not observed any effect on drivability on an engine that is switching in and out of learn mode. It may be important during an emissions test.