I noticed that when I down a very steep street and I compress at very low speed ( 5 to 15 mph) there is a blue cloud of smoke when I give some throttle after. Never when I drive normally and even if I abuse the gas and compression . and it never happen on a non sloped street

 

Blue smoke indicates oil burning. Hopefully somebody else can chime in on as to why it only happens on sloped streets.

 

Deceleration like this draws minute quantities of oil into the cylinder where it will burn. I recall the break-in instructions for my Triumph motorcycle years (and years!) ago specified to periodically sharply close the throttle to draw some oil up into the cylinders to help the pistols wear in.

If visible smoke, though, you may have valve stem problems allowing oil to enter the cylinders.

-- Chuck

 

but why it only happen in a sloped street. even if i slow about 75 mph to 0 without using brake in a normal steet, no smoke come out. it happen may be 5 time this summer in 1600 miles

 

My guess is that a sloped street puts more load on the engine, ie vacuum

 

Sucking it through the PCV. It is quite common for S2000s on the track, especially AP1s. This past weekend there was a downhill right hander that required a hard brake right before, I was filling a catch can every session. Lots of S2000s were blowing smoke, including me.

 

If you are using the engine to slow the car (low gear) ---> pulls more oil across the piston oil rings. Then, when you accelerate this pulled oil will burn and cause big smoke out the exhaust.

 

I am actually betting the oil is pooling by the PCV due to the extreme slope. His decel is causing a bit to be pulled through due to vacuum pressure.

 

Very possible it is a PCV issue. Blue smoke typically = oil.