Just thought this was interesting, but I swapped in a JDM S5 TII into my S4 N/A and because it was a budget project, the exhaust setup is currently the stock JDM DP (no cats) to a straight pipe to the stock N/A catback. Also, I just have a cone filter on the AFM.

I hooked up my boost gauge this weekend and have done a number of pulls and in every gear it goes straight to 5PSI and doesn't creep past it all the way to redline.

I am guessing the boost is this low because of the N/A exhaust, but that's probably a good thing because I just have a stock TII fuel pump and stock injectors. Anyway, it still pulls a lot harder than my other two N/A's, but the mufflers are starting to fall apart and it sounds loud and ugly coupled with the straight pipe. Otherwise, seems to be a successful swap and has been running well.

Just thought I would share what I found.

 

From the main cat back, exhausts are the same for all FC's. The mufflers are slightly shaped differently for s4 and s5, but they flow the same.

 

You need a TID is why you are still retaining 5psi on that setup. Note you will jump right to 8 and creep to 11 when you change to a TID with your current exhaust setup. It wont flow enough in 95% of applications to boost any higher. I would not suggest going any higher then stock on the TMIC anyways.

 

wats TID again?

 

Turbine Inlet Duct.

 

TID, according to the FAQ Sticky, is Turbo Intake Duct, but I've known it as Throttle Intake Duct. If I'm not mistake, basically, its the piping that runs from the Turbo/Throttle Body to the Stock Air Filter Box, or really, any Air Filter.

 

Hmm...I thought that stock boost for the S5 was around 8.6psi though? What would be taking away around 3 and a half psi? I am using the stock S5 TID.

 

5.5psi 8psi for enfina if I spelled it right

 

5.5 psi is for a S4 Turbo. 8.6 is about where fuel cut hits on an S5 I remembered as stock boost for an S5 is about 7.5. How come my S5 is only boosting aroudn 5? Is it because I am using an S4 ECU, boost sensor, and MAF?

 

IF you are not using the s5 engine's boost control solenoid, you will still see the stock 5.5psi from the wastegate actuator. Both the s4 and s5 turbos use the same actuator at the same psi. The s5 engine boosted higher due to a comptuer controlled boost solenoid which acted like a boost controller.

 

So I am raising this from the dead, but I am guessing that there is no easy way around this? If it is computer controlled, then it isn't going to work with my S4 N/A ECU?

I would like to bump it up a couple PSI, but does this mean I will need to get some sort of boost controller or is there something else I can do?