maybe someone can shed some light on my issue, my wideband gauge is showing me kind of lean, the air here is much cooler now but wondering if me messing with my BOV screw yesterday could have caused me to go lean ? i wouldn't know why it would do that but just wondered why it's showing me going lean, hits 12.8 or so at WOT, before would stay in 11's. i tightened the screw/allen wrench. it has more of a flutter sound now, i want to get back under the car and change it back to see if it goes back to how it was but im on a trip and unfortunantly i just messed with it yesterday when i was changing my oil. thanks if anyone can help.
__________________

 

From what I read from VW 1.8 turbo and also wrx owners, yes it will cause your car run leaner. I could be wrong though. Bump for more info.

 

I am sure someone will correct me but I can't see why adjusting the BOV should affect WOT operation - deceleration sure when it vents.

If you are running lean, it seems to me you either have more air or less fuel. Is it possible you introduced a leak when you were adjusting the BOV - can't believe there would be an injector problem, the coincidence would be too great.

 

SS box sets FI by boost level and RPM. There may be a slight change in FI at a given RPM because you changed the BOV blow-off setting, but inconsequential. Mainly, at low RPM you're not going to get much boost anyway because the blower is turning slowly. The big danger for you is lifting off the pedal at high RPM and boost. The BOV won't open as promptly leading to surge that can damage the blower very quickly. The flutter you're hearing is the warning signal--back pressure fighting against the spinning of the blower blades. They get crushed into the walls of the blower breaking off tiny metal chips that get into the bearings.

 

+1..flutter is BADDDDD . Tightening up the screw will close the BOV sooner and it does throw off the tune...More in the lower and middle rpm's I would think .

 

Could it change my miles per gallon also, I used to get over 27 mpg and now I'm getting like 23im rollinf down the highway right now, I know this may sound stupid but it has me concerned

 

Lots of things can affect MPG but not the setting on the BOV. That only affects a tiny slice in time when you're transitioning from 5 mm to 4 mm vacuum or in reverse--depending on the setting and has negligible affect on A/F. Most of use have about 4-7 threads showing. I've got 6 I believe. My BOV closes and opens at ~4mm vacuum. MPG is affected by the way you drive, weather, octane, your state of tire alignment or misalignment, newness of your spark plugs, and wear on your engine. If your A/F is dipping into the 10s during boost, that also wastes gas. I've got my boosted A/F in the 11-12 range when above about 3500 RPM.

 

Have you checked your O2 sensor only you have different AFR numbers than before and also significant loss in MPG

 

It could be the bov fluttering, i know mine did at low rpm increases

 

ok, i got the car up on a handicap ramp curb and a truck stop in memphis tn, (dont ask) and was able to reach the bov and had the tools with me, im on a business trip from destin florida to kansas city mo, unscrewed the nut and backed out the screw with an allen wrench, no more flutter, air fuel now will go to about 12.3 or so under WOT, before when it was fluttering it would go to 12.9 or so, haven't gotten on it too much since i just spent 15 hours driving, and the car was tuned with temperatures around 85-90 and temperatures now are 40. im going to calibrate the wideband tomorrow morning and see what it reads out under WOT. i will update everyone tomorrow. thanks for the help so far. car is still fast though

 

If you tuned at 85 degree's and are in 40 degree's now , it may run a little leaner also . Your not to far from me, being in KC . I got a brother that live there

 

how far are you from kc ? i'll be in town all week, im actually about 90 miles southeast of kc, clinton mo to be exact.

 

Can someone explain how colder air would affect the A/F ratio.. Colder air is denser but the MAF and o2 sensors would sense denser air and call for more fuel to maintain a reasonable constant A/F ratio at whatever it is set at! The colder air would contribute to higher combustion product and more power output .

 

Yes ..for cruising, But once you go to WOT and boost . The tune is set with the SS box . I live in Omaha Nebraska . 100 degree summers and -10 winters . Ive never logged and compared WOT runs from season to season and couldnt tell you how much it effects it , but Im sure it does

 

AHH... alittle further than I though...Im up in Omaha..couple hours to drive

 

That's correct. Under boost, the SS box completely takes over for the ECU and specifies a fuel pressure and injector on-time for each psi of boost vs RPM on a continuous 3 dimensional map. This is called going from the normal "closed loop" of the ECU and O2 sensors to "open loop" of the SS box's own programming. When colder air is provided during open loop, there's no way for the SS box to know that or adjust for it. If you have an aggressive tune for hot weather, you're going to have a very lean situation in cold weather.

I think it's best, if you don't want to retune your car 2 or 3 times a year, to tune it perfectly for cold weather (say 40-50 degrees). Then, in hot weather it's a bit richer which will prevent detonation that would ordinarily be promoted by hotter intake temps and a hotter engine. I had mine tuned at about 50 degrees, but have yet to drive the car in really cold, sub-20s weather. I'm curious just how lean it's going to get up here in New England in January.