Not sure, I'll get back to you.

 

Mivec?

 

nope just the old 03.

 

I maintain that the bov isn't reacting proper. Do you have a dedicate bov vac line? With no leaks? How much vac at idle an how much at cruise overrun ? What hot side on the green?

Edit didn't see ya say 'ill check'

 

Another bump for drivability tuning tips.

I get mild bucking on the street, but it's really bad on track (road course) at high rev's and mid -> lift throttle.

VIII, totally stock intake, 9DV w/ dedicated line, stk 9.8 turbo, 3-port on tephra v7, TX-264 cams, exhaust.

 

For those running TephraV7 what is your TPS vs. WGDC setting? Mine has the WGDC matching TPS (0/0, 10/10, 25/25...).
How about timing in the region that bucks? Mine's in the low 3X deg range.

 

Attaching two log files that I believe capture the event.

Looks to me like the BOV is opening to soon/easily as I see Airflow jump significantly while backing off throttle.

thoughts?

 

Bump for log review

 

Please look at the log

 

been busy, ill try and take a look tomorrow.

i run stock cams so very little of what i do will apply tho

 

Bump for log review

 

Anyone get to the bottom of this? I assume iacv settings may come into play as well as the bov

 

Honestly. Its the bov. To stiff you get flutter. Too loose it wont hold your boost. Buy a bov thats adjustable. I use the turbo xs rfl. While its a lil ricey. It also lets you stack washers in it to "tune" it proper. No matter what its going to do it with a stock turbo running high boost. Also notice it happens at high load. Like uphill in 5th gear at less then 4k. But you can make it live able by messing with the bov. The # 1 cure ive found is buy a bigger turbo

 

yeah, if it happens at slight throttle lift, its the dv. when the dv opens, the charge piping rapidily depressurizes. most people have their dv installed in push mode, so once the pressure drops, the dv closes. pressure rebuilds, and the dv opens again. the vacuum signal can also contribute. its basically an overreactive poorly damped feedback loop. i've tried three different well designed aftermarket dvs, and while i was able to adjust where it happens and lessen the severity, i was never able to completely eliminate it.

some dvs like the synapse and tial qrj can be operated in pull mode where opening depends almost entirely on the vacuum signal. this can help but in my experience, its not a perfect solution.

a dv with a more progressive opening to allow better control over charge pipe pressure reduction would be ideal, but in my conversations with synapse a few years ago, they were either uninterested in the idea, or they felt it couldn't be done. wasn't clear on which it was.

the maf does seem to be strongly affected by the reduced or reversed air flow caused by the dv opening, and for many people, switching to sd helps a bunch.

 

I don't have this problem anymore after tuning the synchronic as I specified here:
https://www.evolutionm.net/forums/ev...g-results.html

although, I think all of my problems were at highway speeds so maybe it's irrelevant.