SameerP

the obvious question for me is for the big turbo A4 owners...is something like these BOV's going to be a good idea with a T28 or GT25 turbo'd A4 which is producing 23+psi peak, and spiking up to perhaps 26psi?

The idea that the valves remain partially open at idle was like a light-bulb going off in my head. Makes me think that the hi-boost shredding of many BPV we see here would be negated by the atmo bleed.

Cheers,
Sameer

wnut

what adaptor are u talking about? there is no adaptor. the H-25 from turboXS is made for the 1.8t just like the forge valves are. you just need to plug up the pipe the re-routes the air back into the intake.

it's pretty much plug - test - and play.

DABearS4

Thanks for the info! Now my S4 will be perfect!

DABearS4

<ul><li><a href="http://www.turboxs.com/type-h_blow_off_valve.htm">from turboxs...</a></li></ul>

zapco98

back into the system. For example, once it passes through the MAF - its now being compressed by a turbo, but does the ECU know how "much" air is going to be coming back on an off throttle situation? I am not sure the Motronic system is smart enough to calculate turbo 'efficiency' - but hey, who knows... The reason I don't think so is that from swapping to K04s, I have had no such issues, and the volume of air being recirculated has definetly changed from what the K03s used to do. Also have to keep in mind, that with a BPV, you're recycling "Hot" air - so that may be a slight performance hindering issue - probably not too noticeable, but for the one who wants 100% performance, that .1% is everything I guess.

I just don't think the ECU is smart enough to know how much air should be coming back, I mean when you're at different throttle positions at different RPMs, the compressing of the air's efficiency is always changing so the amount of air bled off is a constantly changing factor.

wishbone

The number one reason most people on this board attack BOVs is because they feel that any car that runs a MAF will run rich. When you vent air that you have already metered into the atmosphere your vehicle will dump too much fuel into the engine. How is this circumvented? Does this not happen?

Do you plumb the BOV directly to the manifold or do you still use the advanced electronic controlled S4 system for the BOV control (valve N249)..

thanks

wishbone

If it's compressed it still has to come through the MAF and it will get metered. As air passes through the MAF the vehicle knows how much is entering the system and will provide the fuel necessary. Even if it get's compressed, the air still has to pass through the MAF, it has to get that air from somewhere? The ECU knows the ammount of air in the system and as you open the throttle plate it will provide the fuel necessary.

TRM

indirectly anyway.

nyet

"this is probably what is happening to those of you that are trying BOVs and the engines run very rich at idle and very poorly, but smooth out when driving at higher rpm....the piston is probably open at idle."

I assume he means that the bov's are open for a short enough time during PROPER operation that the car does not run rich for a significant amount of time, unlike at idle, where running rich for an extended period will throw dtc's and result in a rough idle.

zapco98

seconds, once you get back on throttle, I don't really see that the air 'dumped' will increase the volume of air that may already be in the airbox - you know what I mean? For instance, say you have an open intake like an Evo or something(I know they're not "better" than stock, but for example) and you dump the air back in to be "metered", its now in the engine bay for the most part - the sensor isn't measuring air going backwards through the MAF, so I still don't think it matters...