Nissan 200SX Club - South Africa

Okay lets see if we can get this sorted for once and for all. if you install a dump valve in a standard setup (CA) the air intake is calculated at the MAF which is located at the very beginning of the system, then if you dump that air which had already been accounted for the management system will fuel for that air as if it is there which results in temporarily over fueling causing a little black smoke puff when shifting (which looks tappet). and if you don't use a dump valve and boost over 0.8bar its hazardous to your turbo.

however i have seen motors even a CA without a MAF!? just a pipe between the turbo and the air filter. How does that work?

Management that uses a map sensor instead of a maf.

Where is the map sensor located then vs. the maf location

Twakkie wrote:Okay lets see if we can get this sorted for once and for all. if you install a dump valve in a standard setup (CA) the air intake is calculated at the MAF which is located at the very beginning of the system, then if you dump that air which had already been accounted for the management system will fuel for that air as if it is there which results in temporarily over fueling causing a little black smoke puff when shifting (which looks tappet).

yes

Twakkie wrote:and if you don't use a dump valve and boost over 0.8bar its hazardous to your turbo.

I know the members on this forum strongly believe that to be the case. There is lots of internet debate on this topic, I disagree that it is a problem at all, 0.8 - 1bar is not high boost. The turbo will be fine at these levels as it is not true surge, and surge is the killer. Having said that I will always recommend a recirculating BOV to somebody. IMHO of course.

Twakkie wrote:however i have seen motors even a CA without a MAF!? just a pipe between the turbo and the air filter. How does that work?

They run a MAP sensor as apposed to a MAF sensor.

Depends on the management but it takes a vacuum / boost from the manifold.

So dumping air doesn't affect it.

bah, beaten to it by a damn dirty rat

Bwahahaha.

AAA shot oaks!!

I know the members on this forum strongly believe that to be the case. There is lots of internet debate on this topic, I disagree that it is a problem at all, 0.8 - 1bar is not high boost. The turbo will be fine at these levels as it is not true surge, and surge is the killer. Having said that I will always recommend a recirculating BOV to somebody. IMHO of course.

agree with daniel, imho the use of a bov on a street turbo setup is very much over rated.. i personally never use them, can honestly say never noticed reduced turbo life because of a little reversion.. far more important to make sure you dont overspeed a turbo, or push it into surge due to mismatch..

Ok I heard what everyone said but run a dump valve and recirculate it. If you dont want to do that then change the management and run a map sensor.

Better lag and turbo life when running a BOV. Low or high boost. Think to yourself - 80000rpm+ then getting stopped and back spun. Then stopped and spun the other way.... umm bearing life/ seals? thrust collars? So do it right or risk it... really your gamble with a couple of grand it could work or it couldn't.

Hope that helps... but as even veilside says: "We do not fit unnessesary equipment like BOV to our race cars but then again the turbos don't last that long due to it. But on a race car that is acceptable"

Think to yourself - 80000rpm+ then getting stopped and back spun. Then stopped and spun the other way....

thats a little bit of an exageration bud.. no ways in hell that the reversion will stop the impeller, never mind spin it backwards on gearchange or even on deceleration..