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Old 07-22-2017, 08:52 PM   #1
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Thump sound when blipping/stabbing throttle (Supercharged)

Hey all,

I have a JRSC C30 kit installed on my 2013 FRS, tuned with ecutek + delicious.

After loading my base tune, I have noticed that whenever I downshift (rev match) or blip the throttle, I hear a thumping sound coming from ahead of me.

This occurrence only happens when I blip the throttle. The sound is not an exhaust pop, as it is not a sharp sound. Instead, it is a muted, toned down knocking sound.

The thump is too faint to be recorded on video. This noise happens regardless of the gear (idle, first, second, etc). All the sounds are the same, and it is hard to diagnose what exactly it is.

Despite having received several revision tunes, the sound still persists. I have checked all my hoses, and there seems to be no vacuum leaks or leaks in general. At the same time, my throttle response has become more sluggish ever since installing the kit and receiving the tune.

Anyone else have this issue? I did not have this noise when I was NA, and the issue only arose once the kit and tune were on the car.

Note: I do not experience this sound when the throttle application is gradual, rather than abrupt. The noise seems to be coming from ahead of me in the engine bay, I also hear a vacuum sound simultaneously. Could this just be the intake?

More notes: narrowed down where the sound is coming from. Seems to be coming from the throttle body tube compressing upon sudden load. I have attached a video showing what I mean



Any idea if this is normal? The hoses are completely clamped down and seated properly, yet this still occurs.
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Old 07-22-2017, 08:54 PM   #2
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Well, think about components that are "underneath you" and troubleshoot from there.
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Old 07-22-2017, 09:39 PM   #3
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Edit for words: just attained a video showcasing what's going on. Any idea how this can be fixed? Everything's tightened down.

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Old 07-22-2017, 10:52 PM   #4
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Are you talking about the sudden air induction noise?
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Old 07-22-2017, 11:16 PM   #5
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Quote:
Originally Posted by Summerwolf View Post
Are you talking about the sudden air induction noise?
I'm talking about the compression of the inlet tube. Not sure if its somtehing to be expected or if its irregular.
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Old 07-23-2017, 12:52 AM   #6
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What the heeell i've never seen anything like that but all my aftermarket intakes had aluminum piping. I hope thats a defective tube and not the real deal.

Id contact JR about it for sure.
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Old 07-23-2017, 12:08 PM   #7
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Interesting, I have the same issue. Similar sound. Only difference is that I have an aluminum inlet tube. But sometimes when I blip the throttle, it would make that noise. I know when I would cold start my car on e85, it would make that similar noise also. I data logged on start up one time and it didn't detect knock. I think my issue is different as yours seems to be strictly with air pressure.
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Old 07-23-2017, 01:56 PM   #8
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Quote:
Originally Posted by Cal3000 View Post
Interesting, I have the same issue. Similar sound. Only difference is that I have an aluminum inlet tube. But sometimes when I blip the throttle, it would make that noise. I know when I would cold start my car on e85, it would make that similar noise also. I data logged on start up one time and it didn't detect knock. I think my issue is different as yours seems to be strictly with air pressure.
Interesting. Do you find that your throttle response has become more sluggish since this issue arose for you? Is throttle delayed at all? This seems to be an issue with mine.
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Old 07-24-2017, 12:04 AM   #9
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sorry that I have nothing useful to say, but DAMN that looks crazy lol
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Old 07-24-2017, 03:42 PM   #10
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some updates:

Getting a variety of answers: some say its the silicon inlet hose and it must be replaced with an aluminum one.

Jackson racing is informing me that its the bypass valve, but everything seems to be hooked up properly and clamped down. Anyone else have this problem with the car?

My tuner says its a mechanical issue, but there doesnt seem to be any leaks/issues.
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Old 07-24-2017, 04:34 PM   #11
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I'd definitely listen to JR instead of some random dudes on a forum (like me)

It makes sense that a stuck bypass valve would cause the "vacuum shock" in the intake hose. There are multiple threads online that mention simple tests to see if the valve is working, which might help you.
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