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Car bogs down under boost - fuel cut?

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Old 10-08-05, 08:54 PM
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Car bogs down under boost - fuel cut?

My car currently has dp, high-flow cat and 99 spec twin turbo modifications and i recently installed a racing beat catback exhaust onto it.

After the catback installation, everytime when i go full throttle, my car will occasionally "bogs down" (1-2 seconds shut off of power) , noticeable at high rpm range (5k onwards).

Is this due to the fuel cut because i am experiencing a boost spike after installing my exhaust? or am i running too rich/lean? i was running on 100 octane+91 octane gas.

If this is due to boost spike, what can I do to prevent this? Am I in a high risk of killing my engine?

Please help and advise. Thank you.
Old 10-08-05, 09:21 PM
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What are the rest of your mods? Stock ECU? I surely hope not with the turbos with the rest of your mods you're running. My experience with fuel cut is an abrupt cut in power, not really bogging down as you described. What boost are you running?
Old 10-08-05, 10:07 PM
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Friend has this problem - very similar. It was fuel cut for him... running over 10psi on a stock ECU with some basic mods. BUT it could also be...

The loss of power over 5k rpms could be a vac leak on your secondary turbo lines. The Stock twins have a boost pattern of 3300RPM for the 1st, 4500RPM transition, and 5400RPM 2nd turbo boosts. If you have a vac leak, this could cause your second turbo to lose power (this happened to me when I had my twins) - I replaced my vac lines and it fixed the problem.

If you have a stock ECU, stick with 10psi. Upgrade to an M2, or something simple and get the pressure reg assembly from 'Walien' to limit your boost spikes. Then you can boost a bit higher...
Old 10-08-05, 10:09 PM
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You don't have a boost gauge? Go get one and let us know what is happening with your boost. I'm guessing you are hitting fuel cut and will need a boost controller or aftermarket ecu.
Old 10-08-05, 11:15 PM
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you have a clugged hf cat
Old 10-08-05, 11:39 PM
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I love the multi flavored ideas and responses...i mean, SOMEBODY has to right. Right?

I say check your grounds as well...my car did that when I first got it, I checked all my grounding points, cleaned them, added a few more, and it went away.
Old 10-09-05, 09:39 PM
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I should of read the whole post lol.

I saw the title and posted.

Like the others have said you probably are experiencing fuel cut.
Old 10-12-05, 12:09 AM
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Hello all, thanks for the reply.

I have a reason to believe it is fuel cut for me as I think I am running lean towards high end.

This only happened after I installed the exhaust, and plus, I checked there's no vacuum leak and I am boosting normal too.

Any suggestion of how I can solve the lean problem?

Thanks!!
Old 10-12-05, 12:35 AM
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upgrade your ECU
Old 10-12-05, 06:02 AM
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Originally Posted by rynberg
You don't have a boost gauge? Go get one and let us know what is happening with your boost. I'm guessing you are hitting fuel cut and will need a boost controller or aftermarket ecu.
Your answer begins with this, a boost gauge.

Until then, I suggest not boosting hard - if your boost increases too quickly, the fuel cut defense won't cut in and then you could blow your motor.

Dave
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