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At the risk of sounding like an idiot, where are you guys seeing peak boost in your focus ST. I got my ST stratified tuned and hit peak boost at about 3k rpms and fall flat after a little after 4k. Is this where I should finding max psi? According to the rep I spoke to this is the correct range i just thought it should be pushed a bit more to the right?
 

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The K03 turbo we have starts running out of steam pretty quick. Also what gear are you doing it in?
 

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2018 Ford Focus ST1
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The stock turbo runs out of breath in the upper rev range. Some guys have pre-loaded the stock WGA (@G heinrich I think did so and he could maybe chime in) and gotten a little more boost in the upper range, but from what I've read it quickly starts generating a lot more heat and then the ECU starts pulling timing to reduce knock in the upper rpm range (thus reducing the potential gains of having more boost from the stock turbo).
 

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check out the vdyno thread, the lower part/right axis (dotted line) of the graph charts is the boost:

379359
 

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The stock turbo runs out of breath in the upper rev range. Some guys have pre-loaded the stock WGA (@G heinrich I think did so and he could maybe chime in) and gotten a little more boost in the upper range, but from what I've read it quickly starts generating a lot more heat and then the ECU starts pulling timing to reduce knock in the upper rpm range (thus reducing the potential gains of having more boost from the stock turbo).

Yeah I tighten up my wastegate actuator all the way and then had Brian tune for it. I don't really pay attention that much but I think my peak boost probably does come around 3000-3200 but then it holds it I believe to about 5000 rpms. I peak over 24 PSI when conditions are right. I believe I'm holding about 18 or 19 PSI at redline. I haven't noticed any charge temp increase with this mod. The depo 3.5 intercooler more than compensates.
 

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I haven't noticed any charge temp increase with this mod. The depo 3.5 intercooler more than compensates.
The main concern isn't charge temp, its drive pressure and cylinder temp. It takes a lot of backpressure (thus, heat) to drive a turbo. In the diesel world (where exhaust backpressure sensors are plentiful) it would range from 1.5 to 2.5. So the pressure inside your exhaust pre-turbo is 1.5 to 2.5 times that of the charge air that youre compressing. So depending on engine and turbo, that means at 20psi boost you've got 30 to 50psi of exhaust between the piston and turbo, not factoring the compounding increase of cylinder pressure.

Point is, once youre above the turbo's efficiency range (which we already are in stock form), the drive pressure and cylinder temp skyrocket when you're forcing more boost out above the range. Do a lot of guys do it? Absolutely. Is it good to do? Absolutely not.

I think this is why we dont see any drastic increase in ringland failures when guys go big turbo. Making 400whp with a proper sized turbo is easier on the internals than 265whp on the overspun stock unit.
 
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