I would like to tune out the rich dip that I get when going to WOT. I know that the ECU needs to enrichen the fueling when there is a significant increase in TPS. But my AFRs drop into the mid 10's when first going to WOT and between gears when getting back on the throttle. The rich dip lasts approximately 2-300 rpm before my curve settles at 11.0-11.2. Makes for nice fireballs on occasion. I have also tuned my buddy's 05 Evo and his ECU does not do this. His car transitions into open loop fueling at WOT smoothly with NO rich dip. I have played with the asynch_rpm table and the lean spool enable rpm (dropped it to 2250), but it made no difference. BTW both my Evo and my buddy's both have lean spool enabled. The big mod difference between our 2 cars is that I have a Buschur head and his is stock. We both have cams and a stock turbo.

 

bov

 

If I do a 3rd gear pull from a slow roll, this rich dip occurs. In this situation my BPV is not doing anything. GST - could you elaborate on your thoughts?

 

Sorry I should have been more specific, I was on the dyno from 10am to 2am yesterday/today and was still recovering when I posted the OP.

I've seen that rich dip happen a bit and it almost always went away after crushing the OEM bov or using a aftermarket stronger bov.

I believe they quickly open right at peak boost then shut down again.

 

Is it because it's VTA? Does the same thing happen if you're recirculating?

 

I usually burn down evos that are VTA on the factory ECU.

(not really but I do avoid them like the plague)

 

Agreed!!! It SUCKS!!!

 

I have noticed this a lot recently, and i cant seem to tune it out which leads me to believe the BOV is leaking. I am pretty sure i can hear it recircing air when the window is down

 

My BPV holds tight with 25 psi of pressure testing using compressed air and a leak checker. I compared my open loop fuel map to the OEM map and my buddy's map. I think part of the dip is an open loop tuning issue. I just flashed a leaner map in the 2500-3000 rpm cells. The other dips between shifts are just the ECU enrichment when going WOT between gears. I'm not sure it is a good idea to eliminate that.

 

A gradual increase in pressure will have a different affect on a BOV in comparison to a fast spooling turbo so if it can't be tuned it's something mechanical and the most logical would be the BOV.

 

If the BOV/BPV is cracking open with the initial boost hit before shutting close, then that would definitely create a momentary rich condition. Of course, this is impossible to tune with my Samco BPV which is already running the stiffest spring. However, I do not believe that is the case in my situation.

 

I get the same dip using a Tial BOV with a stiff spring. I also get a lean hump imediately after that's about half as large but lasts twice as long.

It seems to be acceleration enrichment as it only lasts about 0.5 seconds. Does it with and without "lean spool" enabled.

Yes, you can "tune it out" on a 3rd gear roll by leaning out the RPM where boost hits, but it leaves a hump in the map that shouldn't be there. On top of that, it won't fix that fact that if you hit the throttle above the boost threshold (like you would when you drive normal), you still get the dip as boost hits.

 

I have the same issue with no BOV at all, HKS hard pipe kit and no tracable leaks.

 

you could try switch bov with your friend and test it out. that way you could isolate the issue.