hrmmm....let me ask you this WT. When you see knock is it while the car is in gear or when you are shifting. The only time I see knock at redline (7600k) is when I shift. Knock is near non-existant until i shift in any gear -- then it's like 195. That can't be real knock since the car isn't in gear....can it??

 

i'm using a buchur mbc and it holds boost great. never drop's psi or spikes... pretty reliable!

 

There is always knock pretty much, but when the knock counts get high enough, the timing gets pulled. I don't know the exact numbers, but here's a rough explanation:

Light knock = timing advances
Moderate knock = timing remains the same
Heavy knock = timing retards

I see knock right now in 4th gear above 5500rpm when my boost is too high in the summer heat. I have 2 recourses: 1) add fuel at those rpms to make it rich enough to not knock (loses power) or 2) lower boost until I can maintain good AFRs without knocking (loses max possible power, but retains solid peak and sustained power through the entire rpm range). When I started out, I would just add fuel to remove the knock, because I was dead set on keeping my boost at or close to 22psi (hard-headed), but then I came to my senses and started lowering my boost to a level that could be tuned properly given the weather conditions. The results were pleasing...

 

Yeah, but are you seeing knock while the car is in gear or when shifting?

 

Uh, in gear of course. I am not concerned about shifting, since the engine is not under load.

That means IN GEAR above 5500rpm at WOT and full boost. I can't tune for knock when not in gear...

 

Exactly, so i'm curious why am I seeing knock only when I shift?? That is why i'm confused too!

 

I have tested my stock DV to just over 20psi and it held without leaking at all (put my hand under and nothing). When I got the car flashed by Al, I had the high performance TurboXS boost controller and boost was bleeding off to 17.5psi by 7k and then stayed that way through 7.5K. This is with it spiking at 20.5psi. I then got the Hallman and it still falls off to 17.5 psi from a 20.5psi spike. I have tried it both connected to the turbo nipple and teed into the DV line with no difference. I have boost leak tested and have no detectable leaks. I also have tried the JDM MR DV and it didn't make any difference. My Autometer phantom guage reads .5 psi higher than shown by the Mustang Dyno. My stock sport meter guage reads a .1 to .2 of a psi lower than the phantom when I convert the measurement.

 

I have similar problem with mine after a reflash. I got the high performance TurboXS boost controller and it tapered down to 14 psi. I finally improve the tapering down to about 2 psi drop at redline. My testing of the mbc has show that the ball spring is great but theres a degree of air leak to the actuator starting at about 15psi. It will cause the wastgate to start slowly open and with the force of exhaust gas pushing on the actuator makes it worst. Alot of boost drops starts to happen at higher rpm not because the turbo cant handle, its because the boost leak into the actuator has more time to buildup pressure and open the wastgate.

First step is to open up your mbc and clean the seat that the ball sits into. Mine was dirty with some black stuff which is causing alot of leak. Use carb cleaner and a Q-tip to clean it off. Make sure the ball and spring is also clean. Put it back to gether the way you pull it apart and make sure you use some lock tight on the threads. Then test to make sure no boost leak until your are geting close to the psi you set at. It would be nice if it dosn't leak at all until the set psi but what can you expect from a metal ball siting on a metal surface.

hope this helps.

 

Thanks for the info, but I no longer have the high performance Turbo XS. My testing was done awhile ago. It somehow walked off my living room floor. I had sealed mine as it was leaking around all threaded areas when I was running 25psi on my Eclipse. Never did open it up to check the spring and ball, but it would hold rock steady on that car with my HKS wastegate and a 1.2 bar spring.

I just tried a regular Turbo XS and it would not boost over 16psi I then hooked back up the Hallman and turned the boost up to so it spiked 22psi. It now only fades off to 19.5 psi at redline