Atmospheric DV....again

[andycupra]

I don't really get it? the air has already been measured and the recirc port is the other side of the MAF so how can it measure it?

And how can air dumped back the other side of it be measured as its behind not infront of it?

yes, so the quantity of air entering the system was measured by the maf, the recirc keeps the air in the system so the quantity measured by the maf remains correct.
If the air is dumped externally, then there would be less air in the system than the maf measured and the ecu has assumed the air has been re-used. If you dump the air externally then more air will pass through the maf than would be in the system so the maf would at certain points indicate more air than is the case.

Im not sure of the details, but i thought the worry was therefore rich running during the dumping phase, which could in turn lead to lean running over-all?

The fact that some seats have thrown up fault codes for dumping externally worries me, as im sure there is a parameter that needs to be breached for the code to log, and so those that have not experienced a code may well be running within parameters bt not 100% correctly.


I cant say i totally understand it all, but seems to be why run the risk for a stupid whooshy sound.

 

[Steely]

i was always lead to believe it was the MAP (manifold Absolute pressure sensor) that detected the lack of recirc boost,

as you drop off the accelerator, negative pressure (vacuum) in the manifold which suppliles both DV and brake servo (due to the inlet butterly closing), the map will detect the drop off boost by a spike of positive pressure in the charge pipe/intercooler, , if it cant detect this spike (atmos DV), it thinks theres a boost leak,

as mentioned the MAF has already metered the air so atmos dumping will make the system think its lost some volume,

I might be wrong!, but it dones seem logical,

 

[level_lewis]

metered air

Because the engine knows how much air at that many revs is going to be recirculated... so it over fuels to compensate... if that excess boost does not return to the engine... you will end up running rich and loose performance...

I read somewhere on here that the older ECU's didn't have much of a problem running fully atmospheric DV... but the later models are a bit picky

I've got a 2005 ibiza cupra and when i run fully atmospheric its almost cuts out on idle

 

[leon cupra r]

I've got a 2005 ibiza cupra and when i run fully atmospheric its almost cuts out on idle

Is that right? surely on idle the DV should be closed so no air would be escaping anyway?

 

[level_lewis]

yeh but i was boosting and then come off the revs and it almost cut out because it prepared fuel for air that wasn't there... sucks i like the sound of a good DV... but not at the cost of performance

 

[ForgeMotorsport]

http://jonnyjetta.blogspot.com/

have a read on the split R , most issues are down to incorrect set up ..Twin psiton wont work , been there done it