Boost dropping off in 3rd gear

[tekdeus]

I was having trouble reaching full boost and the boost was dropping at times. I tested for boost leaks, and found and fixed them all: leaking CT26 57trim compressor housing, pinhole in intercooler, vacuum line popped off under intake manifold. I also shimmed the wastgate with 2 washers, as a fellow member suggested that my wastegate spring might be getting weak.

After all these fixes, I am still having boost in 3rd gear drop off from 15 to 10 psi. I have an Apexi AVCR boost controller. I don't know what to try next?? What else could cause this problem, and why is it mostly in 3rd gear? 2nd gear holds 15psi just fine.

I'd like to race the car in Vegas, but am at a loss on how to fix this one. Thanks

 

[Poodles]

Think it's normal...

 

[CajunKenny]

I'm not farmiliar with your boost controller. Does your AVCR Boost Controller have a gain adjustment?

If so, try raising the gain two increments at a time and see if that helps.

EDIT: I had similar issues because of an exhaust leak. Just a thought...

 

[IJ.]

Might just be pushing the WG Valve off the seat in 3rd.

Adding a few washers will help some, check the AVCR gear settings to make sure it's not pulling boost on purpose.

If you spend time setting it up the AVCR is brilliant but it's easy to lose your way.

 

[tekdeus]

Never had this problem before, and didn't make any changes with the AVCR. But I will have a good look into its adjustments and hope for the best!

 

[suprahero]

Dude.......that's exactly what mine is doing and it's doing it in third gear as well. Aaron told me to check my boost pressure sensor that's mounted on the firewall. I've already replaced the valve with a new MAC valve and it didn't help anything. I've also searched for boost leaks and haven't found any. I'm pretty sure we're having the same problem. Mine boosts to seventeen psi and then falls off to 10, 11, or 12psi and then climbs back up to 13.5psi since that's what the wastegate spring is set for.

 

[suprahero]

Here's my thread on this problem.
http://www.supramania.com/forums/showthread.php?t=78947

 

[suprahero]

Have you found anything out about your car?

 

[NashMan]

most ly what is happen blowing the door open just play wih eh duty on the avcr if this does not fix it shim it or replace spring

 

[tekdeus]

Thanks for the ideas guys. The key was in the AVCR manual! I adjusted the duty a bit, but the feedback setting for each gear was the solution. I simply upped the feedback for 3rd gear from 3 to 7 and it's now holding boost in 3rd. It still fluctuates a bit but I think fine tuning and the self-learning of the unit will smooth that out.

Glad I don't have to monkey with my wastegate!

 

[suprahero]

How much fluctuation are we talking about? Did you try adjusting the gain for third gear any? I'm just wondering if adjusting the gain any will make it spike.

 

[tekdeus]

I didn't see a gain adjust for each gear, just the feedback adjustment. It occasionally fluctuates within 1 psi now, after today's changes.