lowrider Posted April 20, 2010 Share Posted April 20, 2010 (edited) Hey everyone, It seems like i have a little bit of boost creep... I just finished up my turbo swap about a month ago. Im using the NA F54 block, with z31 t3, and the stock NA ecu. I havent had a boost gauge when i first got the motor running and semi tuned. Today i borrowed a boost gauge from a friend just to see what boost the car was running. It seems like i have a problem with boost creap in 3rd and 4th gear. As soon as i build boost in 3rd the needle imediatly goes to 7 psi, Then as i get higher in my rpm range it steadily goes to 10 psi. When i stift it drops down a bit, but then goes right back to 10-12 psi. This kinda baffles me since it is the same trim as a stock 280zx's turbo and it still uses the factory wastegate. Anyone care to shed some light on my situation? Edited April 20, 2010 by lowrider Quote Link to comment Share on other sites More sharing options...
yetterben Posted April 20, 2010 Share Posted April 20, 2010 what size exhaust. Quote Link to comment Share on other sites More sharing options...
lowrider Posted April 20, 2010 Author Share Posted April 20, 2010 what size exhaust. Im running a 3" crush bent from the z31 downpipe back. Quote Link to comment Share on other sites More sharing options...
FlatBlack Posted April 20, 2010 Share Posted April 20, 2010 Im running a 3" crush bent from the z31 downpipe back. I'm getting the same on my F54/P79 NA>T with a 3" open exhaust off a 2.5" MSA DP. Creep up to about 11 psi. I know one of my wastegate bolts is really loose, but I'd assume it's because of the open exhaust. Quote Link to comment Share on other sites More sharing options...
lowrider Posted April 20, 2010 Author Share Posted April 20, 2010 I'm getting the same on my F54/P79 NA>T with a 3" open exhaust off a 2.5" MSA DP. Creep up to about 11 psi. I know one of my wastegate bolts is really loose, but I'd assume it's because of the open exhaust. Thats interesting... I knew I coud'nt be the only one experiencing this! I did have a bolt loose on my wastegate actuator but i tightened it before testing the gauge. What im wondering is if the boost is raised if the creep will increase as well. Hmmmm... Quote Link to comment Share on other sites More sharing options...
Pyro Posted April 22, 2010 Share Posted April 22, 2010 Try porting the wastegate exhaust port on the turbo. enlarge the exhaust port a little and smooth out the sharp edges leading to the exhaust output with a die grinder. Quote Link to comment Share on other sites More sharing options...
lowrider Posted April 22, 2010 Author Share Posted April 22, 2010 Try porting the wastegate exhaust port on the turbo. enlarge the exhaust port a little and smooth out the sharp edges leading to the exhaust output with a die grinder. I used the search function (imagine that!) and found a few threads mentioning porting the wastegate port. I figure ill give it a try when i get some extra funds and replace my exhaust manifold gasket. Untill then I plan on just keeping a close eye on the boost gauge. I actually made a Manuel boost controler and increased my boost to 9 psi, and the creep was'nt as prominate as before, Imagine that! Quote Link to comment Share on other sites More sharing options...
Snailed Posted May 11, 2010 Share Posted May 11, 2010 (edited) Yeah, if you raise the boost it shouldn't creep. Exhaust is lazy, it just wants to get out the easiest way possible and on your setup (big exhaust) it's easier to go through the turbine wheel than make a 90* turn into a little wastegate hole. Porting it and radiusing the leading edge of the inlet and trailing edge of the outlet as well as increasing the diameter can all help. If you open up the volute only up until the WG port, that will help too. The best fix is always more boost though Edited May 11, 2010 by Snailed Quote Link to comment Share on other sites More sharing options...
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