What would cause black oil in a tuned engine

[Rawze]

(04-30-2018 )Chamberpains Wrote:  ...a 435ST CM870 engine.
...
I have no need for more power and fuel mileage is the goal. Will advancing timing affect fuel consumption and possibly clean up the fuel burn? Which inturn will keep my oil clean longer?

On my old car with the 350 Chevy engine in it, I used to have 2 notches marked on the distributer. One for fuel mileage, and one for power. It is nothing new, guys used to do things like that all the time on older cars.

Yup. Within reason, the more you advance the injection timing on just about any piston type engine ... car, motorcycle, truck, even a lawn-mower, the higher the fuel mileage will get.

The trouble is that at some point, it becomes A RISK OF CAUSING DAMAGE due to high detonation and other things if it is not kept well in check.

This guy sums it up quite nicely about too much timing advance at 6:48 in the video ...
https://youtu.be/sATO6kfi_VY

In his video he sets it to +12 degrees. -- Back in the day on those old 350's, Most of the guys I knew used to set em to +14 to +15 for maximized fuel mileage, and down to +6 to +8 for when they needed a lot of power so that the engine would run a little cooler internally and to reduce internal friction.

I know lots of guys who use advanced injection timing settings and set them close to the upper edges of safe levels,.. but still end up loosing the engine. This is because you cannot predict a bad spray pattern on an injector, or other fuel related problems in the cylinders that can send it over the edge. What good is it when you save some fuel if it costs you a re-build?.

Lastly, injection timing settings also go hand in hand with fuel air mix, power and torque, rpm, intake temps, compression ratios, and about 200 other factors.

Here is an example of someone adding too much injection timing to an ISX even when it had a decent tune in it ...
http://rawze.com/forums/showthread.php?t...7#pid13847