DKneble
15+ Year Contributor
- 123
- 0
- Mar 13, 2006
-
Phoenix,
Arizona
Went out tuning last night to get ready for going to the track this week and having some issues. Running on 110 octane. Basic setup is 6 bolt built 2.0 motor, gt35r with supporting mods, 850s, SMIM, SBR boost controller, etc
Did some third gear pulls and logged on DSMLink. Acceleration seems unsteady especially right when nearing 24-26 psi which is at 4800 rpm in third. The car bucks a little, not crazy but its noticeable, and then above 5500 rpm it feels like every once in awhile it misses. Looked at the logs and the boost fluctuates when this is happening just before it evens out at 26 psi, basically a zig zag for about 800 rpm on the log. Also the air/fuel starts a nice little zig zag between about 10.5 and 10.9 but the AEM wideband holds pretty true at 11.1.
Then comes the weird thing, put the car in second and do a pull and it seems like its missing and bogging everywhere and constantly trying to catch up to itself. Feels like a horrible boost leak but...
Did a boost leak test to 40psi and found something I haven't found before. Once the pressure got up to about 24psi it had enough force to rotate the crank to a point where I was losing boost through the motor. Enough flow to actually start spooling the turbo. I have 284 cams and 1mm oversized valves in the head, is this normal??? i can rotate the crank to a different point and it will hold boost fine and I found no leaks.
And ideas? I'm worried the valves aren't seating right...ugh
Did some third gear pulls and logged on DSMLink. Acceleration seems unsteady especially right when nearing 24-26 psi which is at 4800 rpm in third. The car bucks a little, not crazy but its noticeable, and then above 5500 rpm it feels like every once in awhile it misses. Looked at the logs and the boost fluctuates when this is happening just before it evens out at 26 psi, basically a zig zag for about 800 rpm on the log. Also the air/fuel starts a nice little zig zag between about 10.5 and 10.9 but the AEM wideband holds pretty true at 11.1.
Then comes the weird thing, put the car in second and do a pull and it seems like its missing and bogging everywhere and constantly trying to catch up to itself. Feels like a horrible boost leak but...
Did a boost leak test to 40psi and found something I haven't found before. Once the pressure got up to about 24psi it had enough force to rotate the crank to a point where I was losing boost through the motor. Enough flow to actually start spooling the turbo. I have 284 cams and 1mm oversized valves in the head, is this normal??? i can rotate the crank to a different point and it will hold boost fine and I found no leaks.
And ideas? I'm worried the valves aren't seating right...ugh
