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C7 Straightpipe problem

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Old Oct 5, 2020 | 02:12 AM
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Default C7 Straightpipe problem

We recently straightpiped our c7 and now it has been making this noise whenever we stay at a constant speed. If you give it a little gas it goes away but comes back shortly. Any ideas what it could be?
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Old Oct 5, 2020 | 07:47 AM
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Most likely it’s exhaust drone at a specific RPM. If that’s what it is most likely you will have to deal with it with no mufflers.
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Old Oct 5, 2020 | 08:56 AM
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Most likely lost some power and torque. These motors need back pressure and you've eliminated that with straight pipes. Did you also go to long tubes and cat delete?

Last edited by 99vetteran; Oct 5, 2020 at 08:56 AM.
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Old Oct 5, 2020 | 07:05 PM
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What speeds does this happen?
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Old Oct 6, 2020 | 08:38 AM
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Originally Posted by 99vetteran
Most likely lost some power and torque. These motors need back pressure and you've eliminated that with straight pipes. Did you also go to long tubes and cat delete?
No motors NEED backpressure. Backpressure is ALWAYS a bad thing. If your car makes more power with restrictive exhaust causing backpressure, then your tune is bad for your combination.

Less backpressure can mean less boost on a motor with a supercharger or turbos, but that doesn't mean less power, boost is just stacked up air that is being kept from the engine by backpressure or other restrictions.
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Old Oct 6, 2020 | 08:46 AM
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Originally Posted by Chazz Underwood
We recently straightpiped our c7 and now it has been making this noise whenever we stay at a constant speed. If you give it a little gas it goes away but comes back shortly. Any ideas what it could be?
What you have described sounds like you are hearing the engine going in V4 mode, then (as you said) touching the throttle again will stop the weird noise (going back to V8 mode).
Straight pipe will accentuate the sound of the V4 mode for sure.
T
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Old Oct 6, 2020 | 07:42 PM
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OP, auto or M7? I agree it’s probably V4 mode.
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Old Oct 6, 2020 | 07:59 PM
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if auto, probly V4 mode, yes. look for the light to go on, on the dash, when its in that mode. if you have a stickshift, the car will NOT go into V4 unless you have the mode selector below the shifter set to eco mode. in which case youre probly hearing it drone. fix it by putting a billy boat axle-back on there, imo. it sounds the best of them all =D

i myself just had the mufflers cut out entirely and thats it, i drive like an ******* so its rare i hear it droning.
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