EZ Boy
08-12-2008, 07:40 PM
http://autospeed.com/cms/A_3022/article.html?popularArticle
Getting Rid of the Oxy Sensor
As was said above, in closed loop the ECU watches the output of the oxy sensor and actively keeps the mixtures at 14.7:1. That precludes tuning them to a leaner value unless you fit programmable management and completely discard the factory system. However, it’s quite possible to unplug the oxy sensor(s) and then tune the complete load range to whatever mixtures you want.
That’s a pretty radical idea and a few things need to be kept in mind. Firstly, the ECU will log a fault code and in many jurisdictions the car will be illegal. (However, in many others it won’t be!). Secondly, the missing oxy sensor may well cause the ECU to automatically go to very rich mixtures – but that’s OK, because you’re about to change them anyway!
Re-mapping the mixtures of a car that no longer has the oxy sensor input can be done with an interceptor or ECU software re-map. You’ll probably run around 14.7:1 at idle but at light loads you can run quite a lot leaner than this with no engine misbehaviour. How lean you can go depends on a host of things including gearing, engine combustion efficiency, etc, but certainly ratios of around 16:1 are usually quite tolerable. In some cars, at light loads you can go as lean as 20:1. You can even enact your own lean cruise mode, by watching carefully the load at which you’re travelling at 100 km/h (or whatever) and then leaning out a little at just these load sites. Too much and you’ll get a flat spot, but again with careful tuning, it’s possible (especially when it’s being done on the road) to go leaner by at least a ratio and sometimes more.
Taking this approach means you can set total engine mixtures from as lean as (say) 16.5:1 to as rich as 12.5:1, depending on the load and rpm conditions. Significantly, the car will spend most of its time at the leaner-than-standard mixtures, making a real and measurable difference to fuel economy.
I thought about doing this a while ago, perhaps not removing the oxy sensor so much as some sort of electrical bypass so the car thinks it's still in start up as the sensor isn't returning a signal to the ecu.
Anyone already tuned this way?
Getting Rid of the Oxy Sensor
As was said above, in closed loop the ECU watches the output of the oxy sensor and actively keeps the mixtures at 14.7:1. That precludes tuning them to a leaner value unless you fit programmable management and completely discard the factory system. However, it’s quite possible to unplug the oxy sensor(s) and then tune the complete load range to whatever mixtures you want.
That’s a pretty radical idea and a few things need to be kept in mind. Firstly, the ECU will log a fault code and in many jurisdictions the car will be illegal. (However, in many others it won’t be!). Secondly, the missing oxy sensor may well cause the ECU to automatically go to very rich mixtures – but that’s OK, because you’re about to change them anyway!
Re-mapping the mixtures of a car that no longer has the oxy sensor input can be done with an interceptor or ECU software re-map. You’ll probably run around 14.7:1 at idle but at light loads you can run quite a lot leaner than this with no engine misbehaviour. How lean you can go depends on a host of things including gearing, engine combustion efficiency, etc, but certainly ratios of around 16:1 are usually quite tolerable. In some cars, at light loads you can go as lean as 20:1. You can even enact your own lean cruise mode, by watching carefully the load at which you’re travelling at 100 km/h (or whatever) and then leaning out a little at just these load sites. Too much and you’ll get a flat spot, but again with careful tuning, it’s possible (especially when it’s being done on the road) to go leaner by at least a ratio and sometimes more.
Taking this approach means you can set total engine mixtures from as lean as (say) 16.5:1 to as rich as 12.5:1, depending on the load and rpm conditions. Significantly, the car will spend most of its time at the leaner-than-standard mixtures, making a real and measurable difference to fuel economy.
I thought about doing this a while ago, perhaps not removing the oxy sensor so much as some sort of electrical bypass so the car thinks it's still in start up as the sensor isn't returning a signal to the ecu.
Anyone already tuned this way?