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Vitek said:
Correct me if I am wrong, but I heard the boost controllers can only control boost higher than what is automatically produced by turbos. What I mean by that is say you installed downpine and your boost will automatically rise to ~14-15psi compared to a boost with CAT's it will only be 11psi max. But again I could be wrong. If any body can clarify it, that would be great.
Once you put a dp or a hi-flow cat, you will push the turbo 12+ psi (unless you don't push the car at all). A dp or hi-flow cat increase the exhuast flow. And, it will not limit your boost to only 14 or 15psi!!!! There is no limit!!!!You can hit 20+ psi with that. It all depends on what octane of gas and the weather.

If you install the dp /hi-flow cat without BCC or FCD, then, once you hit 14 or 15psi, the stock ecu shuts off the gas.

if you install a BCC or FCD with dp/hi-flow, you will hit 12+psi, 15+ psi and 20+psi..depends.... and, that's the boost controller controls the max. boost you allow. note that BC cannot set a level that lower than what the turbo push (for our stock TT,lower limit is ~0.8bar as MtFujiSupra said " to lower than what is normally produced").

dizzy,
Your case is true only if one of the following is true:
1) you have a ecu upgrade.
2) you don't push your car at all.
3) something wrong w/ your car so that you dont hit 14/15psi at all.

neonafkz,
stock twins w/ 28psi? that's not a good sign......

This is just a basic BPU topic. Please refer to:
http://mkiv.com/faq/faqtt.html#bpu1
It said, "these upgrades are proven (by us naturally!!) to have a high degree of reproducibility from car to car if you install all of the following: " Again , *ALL* of the following... don't just put one by one.... you are going to screw up your twins like someone running 28psi here...

I am out of here.....

MtFujiSupra,
They NEVER say RT cat is legal because not all 100% of cats are passing. If you look at mvp's description, they claim it "should" because its close. I know someone that failed by a hairline with 1st gen RT cat. I had a 2nd gen put on last yr. i havent test yet.
 

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Supra JZA80 said:
Once you put a dp or a hi-flow cat, you will push the turbo 12+ psi (unless you don't push the car at all). A dp or hi-flow cat increase the exhuast flow. And, it will not limit your boost to only 14 or 15psi!!!! There is no limit!!!!You can hit 20+ psi with that. It all depends on what octane of gas and the weather.


dizzy,
Your case is true only if one of the following is true:
1) you have a ecu upgrade.
2) you don't push your car at all.
3) something wrong w/ your car so that you dont hit 14/15psi at all.
Sorry, I do not believe what you say. Going from the stock cats to a high-flow cat (or even a DP) does not magically allow your boost to have no limit. There is no "boost feedback device" that was removed along with the stock cats.

What did change is the backpressure that the engine-managment "expects" to be there, which means the boost goes higher than the 11psi that was designed-for. With the high-flow cat, this can mean just a couple PSI above stock.
 
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