is this a bad wastegate???

[FTC]

about midway(3500-4000RPM) through each gear my car has a big surge, or stutters if you will. it only really happens at WOT, it stutters and then accelerates like a bat outta hell to the top of the gear. there is no KR that i notice on the SM, so ive been reading the it might be the wategate so maybe one of the gurus could help diagnose this. still gotta figure out whats making the turbo spool slow toooo. i dont thik its the DS header cause im told thta it was fixed, but u never know right.

 

[scottyb]

What kind of boost? Does it reach max boost at this time or before? Does it return to that boost after the "stutter"?

 

[FTC]

it happens around 10-11 PSI then continues to climb till 15-16 after the stutter, then shifts gears.

 

[scottyb]

Well, with the info so far, I'd say that it is not the wastegate. I suggest giving more info like your setup, scanmaster readings, fuel pressure, etc.

 

[FTC]

well i think i found it, the down pipe was loose and rattling around, so i tightened it back up and the o2 readings came back.

 

[TurboRegal84]

The downpipe has nothing to do with O2 Readings, or feeding the computer false information because it is after the O2 sensor.

What are the plugs gapped at?

 

[FTC]

well took it for a "test run" tonight and the stutter is still there. but for some reason the o2's are pretty good, even though it was stated that it has nothing to do with the DP. im not sure what the plugs are gapped at but i think 0.35. havent changed plugs since i bought the car.

 

[scottyb]

Spring Cleaning

 

[Weazel]

FTC, my car seems to be doing the same thing. I will hopefully have DirectScan up soon, and will record some runs. If I figure anything out I'll let you know. It feels like mine has a little more lag, and the boost is more erratic, since I monkeyed with the wastegate.

 

[UNGN]

What type of downpipe or wastegate are you running? What other mods do you have?

 

[Chris McDade]

Thats alot of boost creep you have. I would check all the vacum lines. It also sounds like your running way rich. What do the plug look like? If your running rich it's loading the car up on the low end of each gear and clearing it up at the top of each gear ( buring more fuel ) thats way it runs better at the top of each gear.

02 cent worth

good luck.

 

[FTC]

i have a bowling grrens DP and the wastegate is stock but the rod is adjustable. the o2s are liek 400-600 at idle and go up to 750-800 at WOT. with no KR. i also installed an autometer boost gauge recently that indicates i only hit around 12 PSI max, while when i was relying on the stocker it showed 15-16 PSI max. i have the boost gauge vac line tee'd. another thing that i found weird is that my car idles in closed loop when i thought the thrasher are supposed to idle in open loop, and i took off the SM and hooked up a snap on scantool and it sai that the timing was advanced 50 degrees!!!!!!!! this is all at idle. so im gonna try change the chip and see what happens, change the o2 sensor, and change plugs. i doubt its a spark problem tho cause when i pulled a plug it was very clean.