Here's the story. I pulled the exhaust off of my car at the manifold to fix an exhaust leak. When I looked inside the manifold, everything was white. The O2 sensor was white as well. I haven't noticed it eating up coolant, the level seems fine. I also haven't noticed any kind of white smoke. The car does pull off amazing fuel mileage though which makes me think it's running too lean. I'm just wondering what might be causing this. If anyone has any input let me know. The car is an S4 NA with the 6 port actuators removed and wired open. That may have something to do with it.

 

A light tan/white color is normal from what I've seen. Especially so if you have your airpump & ACV still hooked up. The air pumped into the exhaust ports will lean out the gas mixture, and produce lighter colored deposits on the manifold walls.

Then if you spend a lot of time cruising in closed loop, then the engine will be metering around 14.7 AFR most of the time. This will also contribute to lighter colors, since you're not always running the car at full throttle. You need a wideband gauge to know if you're running lean when it counts (at WOT). But really, it's unlikely that an NA is going to be leaning out. They're rich from the factory.

 

The air pump on my car is long gone, but I do daily drive it. It sees alot of cruising. I was wondering if having the aux ports wired open all of the time would cause it to run leaner than normal too. I also remembered I need to change the fuel filter. I'm looking at getting a megasquirt this weekend. Then I can monitor things and make tuning adjustments. It sucks having such an early fuel injection system that you can't monitor with a scan tool.

 

Wiring open the aux. ports won't make you run lean. It'll actually be more likely to make you run richer than normal below 3800 rpm, since intake air velocity takes a hit. I don't know much about the megasquirt, but if it has an RPM controlled output, use it to activate an emissions solenoid that'll direct air to your actuators. You can use a small electric air pump as a source. It's a lot better than killing your bottom end, and making your car slower with the ports stuck open.

 

race gas can turn your exhaust parts white too, lol. what kind of mileage are you getting?

 

I haven't been running race gas, but sounds like a fun idea. The car will get damn close to 30mpg on a trip. Probably somehwere around 26mpg just bumming around. I live in the country though, and I DRIVE my car. I'm just paranoid I guess because it is my DD. I don't really care if it blows, but I'd prefer it didn't. I'm also used to piston engines, and usually when you see that colour in the exhaust it means trouble. I guess I'll just drive on and see what happens. There is alot of black on my exhaust tips though, so it's probably fine.