dump to atmosphere valves kill cats ????

[mikeyg1981]

okay im having an arguement about dump to atmosphere killing cats but my mate says the dump valve is activated when the throttle is shut of so it shouldnt over fuel ! as the ecu registers the tb shutting so cuts the fuel . ive been told loads of times on here that they kill cats any one got some technical knowledge i can shove in his face ? oh he has a focus rs

[Stu]

Both are right depending on your car. With a map sensor it works on air pressure in the system so can sense if the air is purged at any point so the ECU will cut fuel on lifting off. On a MAF equiped car like the 200SX once the air is in the system there is no way of the ECU knowing if it's left before the cumbustion chamber so it still throws in enough fuel to burn with the air already in the system.

[Stu]

After a quick check it looks like the Focus RS also uses a MAF sensor so yes, a dump to atmosphere BOV will likely cause damage to his CAT. :nod:

[bkvj]

it took a couple of seconds for me to understand...a kitty cat? what does that have to do with a BOV?!

but yeah, you got your help:)

[mikeyg1981]

cheers stu

[manic_mechanic]

PPC has a buyers guide on the Focus RS this month and they state that atmospheric BOV's make that car run shite, and bugger its cat up............

[dannyb1986]

they also put the engine light on,i worked on a focus rs the other day and he had fitted a dv and it had put the engine light on.