Leaking Boost in Second
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This is a discussion on Leaking Boost in Second within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I recently put in a TXS MBC, and set it to about 13psi, just because I didnt want to over ...

  1. #1
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    Leaking Boost in Second

    I recently put in a TXS MBC, and set it to about 13psi, just because I didnt want to over boost it. Later my friend put nitrous into his 525i and wanted to race me, so naturally i wanted to show him everything the rex was about, so i cranked it up to about 15.5. Everything was good with the boost (killed him) so i set it down back to about 14.5 psi. Then as i was running at WOT in second, the boost would peak at 14.5 and then gradually taper off as the rpms increased, at the redline it must have been down to 12, after i shift into third, it peaks again, and leaks only a little bit, probably about .5 - 1 psi. Can anyone tell me what this could be? I checked all the hoses going to the MBC and everything seems secure. anyone have any ideas?

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  3. #2
    Registered User Trypsin's Avatar
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    Turbo cant keep up, a larger turbo will fix that.

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    you think this means that I'm running rich, as not as much air is getting into the engine? It was running fine before at higher boost too. Doesn't the stock turbo and BC push 14.4 psi?

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    anybody???

  6. #5
    Registered User Trypsin's Avatar
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    Yea, the ECU acctually pulls boost as you get close to redline with the FBC. I am still stock but from what i have read i wouldnt expect more than 12 psi at redline probably less. I have done the free boost mod before but cant remember wht boost was like at redline. All in all the TD04 is tiny and just cant make the boost at redline, the motor gobbles up the air to fast and get out of its efficient range(just makes a bunch of hot air)

  7. #6
    Registered User NJSubieTech's Avatar
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    Ok, heres the lowdown. Actually, the turbo is capable of making around 15 or 16 psi at redline, but the stock ECU is programmed to let it drop off for fuel efficency, because you dont need that boost to make power in 2nd gear. If you have a good EBC, correctly programmed, you should be able to get 15 psi at redline. With my AVC-R, I run about 17 psi peak (4000 - 5500 rpm, which is the range that the stock boost is qouted at 14.3) and taper to about 15.5 from 6000 to redline. This has caused me to get 2 - 3 mpg less that I had before having the boost controller.

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    Joe
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    "Damn.... this car is wicked fast..." ~ My roomate, owner of a supercharged/intercooled 97 Trans AM
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