High Pitched Whine When Wot

[suwidji]

Hey all,

So after fitting my fmic, I've noticed a kind of high pitched (sort of metallic whining sound) when i put my foot down. I've checked all connections from the intercooler, and everything is on tight.

It sounds like it's coming from the front of the car, maybe slightly on the turbo side (but not too sure). Any ideas what it could be?

I can try get a video of it, though I'm not too sure how good my phone will be at recording the sound. Car sounds fine when driving normally, and hits my max boost of 10psi no problems (apart from the extra lag expected from installing the cooler). But yeh, the high whining sound kicks in maybe after 3k RPM or so.

Not sure if it's a normal sound after installing a fmic or if i have a leak somewhere :\

[WMDC35]

it must have a leak somewhere

[Ben C34]

Definitely a boost leak

[wolverine]

Did you leave your missus under the bonnet? If not then boost leak.

[StevenCJR31]

^^^ ha ha beat me to it. . . replace "missus" with exwife

[SargeRX8]

Accidentally a supercharger.

[suwidji]

hmmm alright thanks guys.

I'll have to strip it down and check where it could be leaking from.

Are there any cheap ways of testing for where the leaks are, because I don't own an air compressor or smoke machine or anything.

[SargeRX8]

Get a can of start ya bastard and then go around the joints and spray them. Where there is a boost leak, could potentially be a vacuum leak and if thats the case, the spray will get sucked into the engine and it will alter the sound and RPM. I think you can use WD40 but DO NOT HOLD ME TO THAT. Others use butane torches and just piss gas on the joints, same principle, gas goes in alters sound indicates leak. Its gonna be from one of your silicone connectors.

If you've got a pod filter you can quickly jig up a PVC or other material with a tyre valve in it then drop down to the local petrol station, remove the pod and AFM and fit in your jig. Connect the tyre inflator to your valve on the jig and set the machine to a couple PSI then fill it up and listen for leaks. If you don't understand what I mean, basically you want to go to bunnings pickup a 3" diameter PVC end cap or a PVC end cap which will fit in the 3" silicone connector and be air tight when clamped down. Then you want to go to a tyre shop and pick up a tyre valve for a couple of dollars. Drill a hole in the end cap big enough to let the valve slip in and boom away you go. Hell you don't even have to go to the petrol station, you can technically use a bike pump. Just get air into an air tight system and if theres a leak, you'll know about it.

Unless you accidentally installed a supercharger.

[Ben C34]

intercooler hoses wouldn't create a vacuum leak as that part of the system doesn't experience vacuum. The start ya bastard would work around the plenum.

test for boost leaks like described. (I don't think a bike pump would work as there is allot of volume in the system and air does naturally leak past the rings a little)

[AngryRB]

pretty sure the intercooler hoses are under a vacuum, mine have sucked in there share of carby cleaner.. Id suggest some heavy duty clamps, mine have a habit of getting loose over time, b@#tards!

If the engine sounds smooth and isn't stalling then id be checking exhaust side, all bolts on manifold, turbo and dump..

Edited August 17, 2013 by AngryRB

[GTSBoy]

There should not be any noticeable vacuum in any part of the inlet tract (ie in the intercooler pipes) at idle, or even driving. Under mild load there might be a very small vacuum in the cooler pipes, but in those conditions you wouldn't hear any change from a small shot of startysbastard. Under high load there should be some vacuum between the turbo inlet and the air filter (a couple of kPa) and lots of boost in the cooler pipes.

[AngryRB]

im confused now, surely if an engines running then its sucking air all the way from the intake valves to the air filter?

when I sprayed carby on my intake silcon pipe just near the turbo I had a reaction just last week so if there wasn't a vacuum then how can you explain that reaction?

although the EBC takes its reading from the manifold so that suggests its the best place to obtain a reading.

Edited August 17, 2013 by AngryRB

[GTSBoy]

Think about where the throttle is.

[AngryRB]

so if I hook up the boost controller to the outlet just after my compressor will I see a vacuum or zero?

[Sklyn]

Voice 002.mp3

does it sound like this? you can just hear the whine past the engine noise.

Would the experts say this is a leak and I should check as already stated? Which side?

Voice 002.mp3

[suwidji]

Can't seem to download the audio file james. It won't let me...

I saw the how to test for leaks mighty car mods video, and it's how you described using the pvc end cap and air nozzle.

But they use an air compressor to pump air inside. As i said earlier, i don't have access to one, and i'm scared a bicycle foot pump is way too small and will take ages to fill up the intake system.

[SargeRX8]

Think about where the throttle is.

Doesn't make any sense ive got my boost controller after the throttle body between the intercooler and turbo and I get vacuum. If there is no vacuum the you are suggesting that if I seal the pod filter in an air tight container that it will run fine. This isnt the case. The engine is sucking in air all the time when it is not on boost and air like water will take the path of least resistance so if he has a leak anywhere after his intake valves air will come in. my boost controller reads -96. No idea what that means in terms of vacuum but thats greddys display.

[GTSBoy]

Boost controller cannot be connected both "after the throttle body" and "between the intercooler and turbo". It can only be one of those or the other.

It is really very simple. When the throttle is closed, the engine generates a vacuum in the inlet manifold. Yes? We all know this. This is because the engine is pumping away merrily, and the throttle is a serious restriction to flow. There is a very small air flow gap around the throttle and through the idle control valve. So, at idle the manifold vacuum is in the manifold. It is not on the upstream side of the throttle. The pressure in the upstream pipework is not very far below atmospheric pressure. There is very little air flow, so there is very little friction or other causes of pressure drop. So there is almost no pressure change across the air filter, none across the turbo's compressor (it might go up a little or it might go down a little, depending on whether the turbo spinning around slowly is a nett restriction or a nett pump, but that's hardly a significant amount either way) and a couple of cfm of air flowing through 2.5" pipe work and an intercooler is not going to suffer any pressure drop. Hence, the pressure upstream the throttle body should be very nearly 1 full bar, absolute.

When the engine is at full load, the throttle is open, the compressor is spinning at 100k rpm, there is more air being pumped than the engine can suck, so the intercooler piping and the inlet manifold are all at approximately the same positive pressure. Slam the throttle shut and all of a sudden you will have vacuum back in the inlet manifold, and a lot of boost stuck in the inlet pipework that has to come out through the BOV, or dose.

[Sklyn]

ok this should work

[suwidji]

hmmm, maybe not as high pitched of a noise, but yes something similar to that.

Sounds kinda like vibrations off the piping or something.