Blow off valve - MY09 WRX

[Ben-O]

Hi there

I have a '09 WRX, I bought a TurboXS hybrid blow-off valve, once installed, I tend to get a lot more backfiring. Why is this? Is it a problem?

[Turboesky]

photo of install?

[Ben-O]

www.flickr.com/photos/lynoliver/16543737487 (https://www.flickr.com/photos/lynoliver/16543737487)

[Turboesky]

Is it possible when decelerating it is drawing in air in that the MAF can't see? Where does the valve release to?

[skinkis]

WRX runs an AFM I assume?
So by venting to atmosphere, you will get incorrect readings, it will therefore not run as well as before.

[n1ghth4wk]

Will run slightly rich on vent if it's to atmo. Big explanation somewhere but cbf digging it up. Only backfiring when you release the throttle yeah?

[protecon]

Will run slightly rich on vent if it's to atmo. Big explanation somewhere but cbf digging it up. Only backfiring when you release the throttle yeah?
The way I understand it, air that is passing through the AFM is "lost" in the system when vented to atmosphere before the TB - plumb-back recirculates back into the intake after the AFM, keeping it accounted for.

[ZAK]

Venting to atmosphere is gay as aids anyways, plumback FTW

Here's a thorough explanation;

Most factory turbo cars run some form of MAF sensor (usually found directly after the air filter box), some use a MAP (manifold absolute pressure) sensor or even a combination of both. These sensors are used to determine the amount of air the engine is using so it can deliver the appropriate amount of fuel. In a car with a MAF sensor, when a BOV vents, air is escaping from a closed system. This air has already passed through the MAF sensor and has been measured, and the computer doesn't know that this air never made it to the engine. This will cause a brief rich mixture as the computer will still deliver the correct amount fuel dosage based on the amount of vented air. There are two stages to a BOV venting, as initially it is evacuating the pressure from the inlet pipes and intercooler, which usually takes less than a second (depending on your inlet system). Then once the pressure is released, the valve stays open to allow the turbo to freewheel, thus reducing compressor surge and the associated thrust and torsional loads. It is mainly during this free-wheeling stage that causes the over-fuelling problems, since the turbo is basically pumping air through the MAF sensor and out to the atmosphere through the BOV, which accounts for the majority of air that escapes the system. The resulting rich mixture is what can sometimes cause backfiring and a puff of smoke in some cars. The severity of these effects usually depend on the state of tune of the engine. In cars that are modified (say with full exhaust, pod filter, a little extra boost etc) but still using the factory tuning, it is not uncommon for the ECU to compensate for the extra airflow it sees by running rich for engine protection. On a WRX for example, mildly modded engines can be running as rich as 10:1 with the factory ECU. It is this poor state of tune that can cause backfiring when an atmosphere-venting BOV is added.

[Ben-O]

Can it do damage to the car, running rich?

[skinkis]

It won't be doing you any favours.

[ChrisGTR]

Has anyone actually clicked the link to see the install photo? It looks plumbed back to me

[huggy_b]

Has anyone actually clicked the link to see the install photo? It looks plumbed back to me
It's a hybrid - so it's 50 return : 50 to atmosphere

[Brett Allan]

Can it do damage to the car, running rich?

If you want to keep the BOV, you can get the car tuned to suit

[ChrisGTR]

It's a hybrid - so it's 50 return : 50 to atmosphere
Ahhhh I see. Yep, that'll be his problem then

[Greg Rust]

It was loud as fuck on Sat night cruise.

[Ben-O]

I was told it needed 2 b a hybrid

[huggy_b]

It was loud as fuck on Sat night cruise.

You can mod them to be 100% to atmosphere.


I was told it needed 2 b a hybrid

Not sure who told you that, but I politely disagree.

To be honest, unless you've done some major work to the car, you don't need to change your factory BOV. I had my 2012 at 300awhp and only changed it because I didn't like the plastic BOV sitting on my fancy pants Process West Intercooler - I didn't need to change for functionality.

Get a plumb back if you really want (I used a Turbosmart Kompact), but I'd sell the hybrid one off personally.

[Greg Rust]

But it looks like this now so is that different to what you had then

https://scontent-lax.xx.fbcdn.net/hphotos-xpf1/v/t1.0-9/10428659_547288155413942_7126386043475086081_n.jpg ?oh=df16a61e0e70525920331b68a72065cb&oe=5570ED29

https://scontent-lax.xx.fbcdn.net/hphotos-xpa1/v/l/t1.0-9/1654465_547288058747285_2823739336234268515_n.jpg? oh=b5a3a87170e6dc1a12bd19aaf35f39ed&oe=5588DF91

[Ben-O]

Took those photos before I put the blow off valve back on. It didn't fit after I had the car tuned, had to move some cables and stuff out of the way. It used to backfire before I had the top mount fitted, but wasn't until the BOV was removed that I realised that was the part making it backfire.

do love the sound of the backfire and the BOV but want to make sure it is not damaging the engine in any way.

[Ben-O]

The tune I had done before already had the BOV on there, and my mechanic, Maximum Motorsports seemed to think there was no problem at all with the BOV being on there.

[n1ghth4wk]

Won't cause a catastrophic failure. Small touch of excess fuel will cool the cylinders slightly. Might wear out the headers if anything (not the the extent of antilag). Not really any different to cars popping flames on limiter etc. If you're that worried go for a mafless tune or recirc it 100%.

[Ben-O]

Thanks for everyone's help I really appreciate it

[Greg Rust]

Hey are you talking about the loud crack from the exhaust during a full throttle gear change?

if so that's pretty normal (and sounded great on Sat night) for a turbo car, you'll have to take me for a blast on the weekend to confirm?