Giving a friend a hand sorting out his X that was previously tuned but is in somewhat of a mess. It's exhibiting a very strange boost profile where is makes only 12psi by 3800rpm and holds it until 5600rpm. After this it will creep all the way up to 23psi. This is with boost control bypassed and the nipple of the compressor outlet pipe connected directly to the waste gate. There are no boost leaks. We haven't started adjusting the actuator to see what difference it make because I think it's odd that it runs such low boost for that much of the power band and then creeps 11 psi up top. The car has all the AMS supporting mods (fmic, intake, 02, dp etc etc). It is running standard MIVEC tables for an EDM RS, which it is.

Any ideas???

 

It's pretty typical that the minimum boost you can run on the WGA can be different the the flow capacity of your Internal Wastegate at different RPM's. I bet if you use the ECU or MBC boost control to set boost at 23-24 psi it will hold that from peak torque to 7k much more evenly.

What octane fuel is going to be used with this setup? Typically the FP Red is best tuned with higher boost levels (25-26 psi on 93 octane) at 11.5 AFR's and then adjust timing down to where it's safe. The lower boost you run on the FP Red, the less impressive the pump gas numbers tend to be due to the restrictive stock exhaust housing.

 

The lower the boost and the more tendency it will have to creep up slightly toward redline.

Here is a small example in an evo 9 we tuned.

Here is a ported fp red with the upgraded 80mm cover @ 20 psi compared to 27.5psi:

 

that's fine, but an 11 psi creep is an awful lot! anyone know exactly what the actuator springs sold with the fpreds for the X are rated at. if i had to guess from the logs, 12psi?

we are experiencing significant creep with the boost controller (greddy profec) as well. hopefully we won't have to go back to the stock bc to try and tame this.

i'm still going to give adjusting the actuator a go as well.

 

unfortunately it's 91 octane, but it can be safely tuned to 25psi. as mentioned above, the creep is present with profec ebc being used as well.

 

Stock controlled ECU boost on the X's are way better than aftermarket boost controllers overall anyway. Grab a boost pill and use the stock system, you won't regret it.

 

Nah my car was night and day difference with the AEM tru boost controller! I use to hold 14psi now I hold 20

 

Well think of boost creep this way:

You can run a 5 psi WGA on that FP Red and it will still creep to that 23 psi, how early you try to open that wastegate won't change the max bypass flow through the Internal Wastegate passage for that turbo and mod combination. If you raised the Boost to 24 psi via a boost controller, you would likely not have any noticeable creep at all since 24 psi of boost is flowing through the turbo and now less needs to flow through the WG side bypassing the exhaust turbine.

The only way to increase flow capacity through the internal wastegate would be to use minimal preload on the WGA so that the opening angle had the largest range of motion. Also porting the internal WG passage to allow more flow would help as well. Porting it large enough to require a larger diameter WG flapper would yield even more flow. Going with a O2 Downpipe combo pipe would likely also help flow, although the increase flow on the exhaust turbine side would likely balance any advantage. An external wastgate would be the best solution, that transformable ATP O2 Downpipe that allows you to use it as an internal or external WG setup looks very flexible.

 

thanks...understanding the cause of creep. what has me puzzled is why when using the boost controller and targeting say 25psi the spool profile is identical to that of not using any. it makes 12psi by 3800 rpm then holds this until 5600rpm and then slowly reaches it's 25psi target by 7400rpm. the only difference is that extra 2 psi up top over spring. we tried everything on the boost controller. the only thing that makes it spool earlier is pulling the hose off the actuator for obvious reasons. have other fpred owners experienced this absolute lack of early torque due to these spool characteristics?