Someone Help, Im going crazy

370guy

Ok heres the deal. My car makes a funny sound under light throttle and low speeds between 2000-3000 RPMs. sounds like a vac leak but I cant find it ANYWHERE. I have a topspeed cat back and Y-pipe with K&N typhoon intakes. Ive even gone so far as to have the flex pipes cut and straight pipe welded in. Nothing works haha. Do short ram intakes make a slight whistle sound?? if so then I wont feel bad, but my concern is its a vac leak somewhere. Someone please help diagnose this its driving me insane haha

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TerribleONE

my takeda intakes on my G37 made a slight whistle sound at very light throttle around those RPMS, however once I got an exhaust I couldnt hear it

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370guy

its very faint, with the radio on you cant hear it. Im about to resonated test pipes so I guess thatll drown out the rest of it haha. I just wanted to see if this was a normal thing with short rams or I have a Vac leak that is impossible to find

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corbin09

The resonated test pipes, or any test pipes at that would make the sound you are hearing more noticeable. It is just a scavenging affect in your exhaust, and on Z cars its normal.

wstar

Yeah I'm on a mostly straight-through exhaust (FI Long Tubes and FI's Catback), and with most of the rear interior stripped out as well. At idle / low-RPM, I can always hear a sound somewhere behind me that sounds sort of like an air leak. Like a tire sitting in the back of the car with a hole in it, or a compressed air hose with a leak, etc. It's normal and nothing's leaking

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370guy

I just wanted to make sure I wasn't going to hurt something with mysterious vacuum leak haha

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Huck

Just turn your radio up so you can't hear it, that solves everything.


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370guy

Thats kinda what Ive been doing, just want to make sure though. Even if I have a Vac leak somewhere would that do any damage?

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Huck

I know absolutely nothing about vacuum lines and leaks, so I can't help you on that one, sorry man. Bump!


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wstar

A vacuum leak will cause all sorts of things to be a little off, but a small one isn't going to cause any sort of catastrophic failure, no. Usually you'll find a vacuum leak under the hood though, not under the car around the exhaust system. There are some exceptions probably, like vacuum lines tied (perhaps indirectly) to lines that scavenge fumes from the fuel tank.

When a vacuum line "leaks" it leaks inward: it's drawing outside air from somewhere it shouldn't. All of the air sucked by the vacuum system ultimately ends up getting burned in your combustion chambers. So if you put two and two together, one way to diagnose a vacuum leak, if you have some idea where it might be in the engine bay, is to lightly mist some starting fluid in the area while the engine's running (preferably cold, so there's not a ton of super-hot metal around the bay). If the vacuum system is sucking outside air through a leak, it'll pick up the starting fluid mist and you'll hear the idle speed change as your engine burns it. Have a fire extinguisher on hand and be careful

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Motordyne

The sound you describe is fairly common with a high flow system on this engine. It can be eliminated depending on the design and the specific combination of parts but its not exactly an easy goal to achieve.

This engines exhaust note is very prone to hissing.