Hi all, I own an euro F355 gts 2.7Mo with the following mods: K&N panel filters Tubi exhaust headers Tubi exhaust Main Test pipes Secondary test pipes The car runs perfect in my opinion. Two days ago I made a 200 mile trip in cold rainy weather, about 32ºF. I wasn´t too hard on the throttle, in fact I was very light on it. I cruised the whole trip at about 80-90 mph. The car ran perfectly with all fluids working at thermostat temperature. I got home and parked the car in the garage. Next morning when I went in the garage I noticed the inner of the exhaust tips were light grey/whiteish. Searching in the forum this can be caused by two things usually: running lean or shot cats. As there are no cats I may assume the car is running lean. O2 sensors are just a couple months old. Nothing has been done to the car lately. I´ve noticed that when starting the car in this cold weather a lot of vapor comes out of the exhaust and the water drips that come out are black. Could it be possible that the condensated water could wash the inner parts of the exhaust so much? Does the better flowing intake/exhaust system make the car run lean? Thanks
On the highway the inlet doesn't make any difference. You have a combined restriction of the air cleaner and the throttle plate. If the inlet is less restrictive the throttle plate closes a bit more to get the same manifold pressure. At full throttle the intake will allow more flow and can cause a lean condition, but at cruise no difference. The exhaust modifications will reduce restriction and can cause a lean condition, in particular pulling the cats will reduce a lot of backpressure and that will cause a lean conditon. Need to get it tuned.
Modern cars run O2 sensors so they can get feedback on the mixture. The perfect air fuel mixture for complete combustion is 14.7 to 1. O2 sensors monitor the oxygen in the exhaust and constantly adjust the mixture to this perfect mixture to minimize emission and provide good fuel economy. This changes when you approach full throttle, then the maps take over and the mixture is increase to somewhere in the 12 to 1 to 13.3 to 1 range. Bottom line is that at light throttle openings it normal to be lean i.e. 14.7 to one, this will give you the tailpipe color you saw. Cheers Jim
