whistle noise after 4.5k rpm

SG · Post by SG » Wed Feb 01, 2006 10:23 pm

hi, has anyone ever had the problem of a scratchy/whistle noise from the engine after 4.5k rpm? usually more on load?

taken the car to a few guys and the best bet at the moment is the variable intake runner motor isnt behaving properly... (ie opening & closing the stage between long runner (low revs) and short runner (high revs)).
it sounds like after 4.5k the intake runner motor is only opening the 2nd stage half-way creating a whistling noise as the air rushes over it..... if you get what i mean

anyone else had a similar sound/problem like this before?

Nacho · Post by **Nacho** » Thu Feb 02, 2006 12:30 pm

Are you sure it's not your head unit?

Boris · Post by **Boris** » Thu Feb 02, 2006 12:36 pm

so the noise comes after 4.5k and stays till 8k ?
or does it only appear around 4.5k?

jap80x · Post by **jap80x** » Thu Feb 02, 2006 4:56 pm

well your mivec kicks in a 4.5rpm, so it mite be that you are hearing, because it does scream.

EURO · Post by **EURO** » Thu Feb 02, 2006 7:20 pm

jap80x wrote:well your mivec kicks in a 4.5rpm, so it mite be that you are hearing, because it does scream.

kicks in at 5.5

maybe its premature moaning?

SG · Post by SG » Thu Feb 02, 2006 8:33 pm

its definetly not the mivec.. thats more of a ferrari-style roar sound

its more of a 'air rushing really fast past something metallic' sound like a butterfly half open in the variable intake manifold.. or even a split vacuum line.. but its only at 4500 (where the variable intake works) and its only on considerable throttle.... so past 4500 on light throttle (holding it at ~5k rpm, theres no sound...), and if i put the foot down again the noise comes back...

and it always seems to fade out at around 7k (whether air pressure changes so that it cant make a whistle anymore but the problem is still there, or the problem goes away, i dont know...)

-aircon off
-head unit off
-recently rebuilt gearbox with new clutch, new lsd, new flywheel (so none of those)
-all new spark plugs, new thermal intake gaskets (recently before the noise)
-tryed disconnecting new air filter, noise still there (last thing done to the car before the noise)
-tryed disconnecting the motor for the variable intake manifold, noise still there (no warning lights either)
-belts look ok
-alternator not checked
-driveshafts assumed ok
-assumed turbo fairy did not come and install a turbo overnight
-cant replicate noise on idle..

cant really give much more info than that

everything seems to point to the variable intake manifold butterflys atm, but im gonna chuck it on a dyno in a few weeks to see exactly where its commin from if no one else has any ideas

Post by **Bennoz** » Thu Feb 02, 2006 9:26 pm

So you just had an LSD put in??...... they are noisy things!

SG · Post by SG » Thu Feb 02, 2006 10:33 pm

yeah but that was after the noise started

Nacho · Post by **Nacho** » Fri Feb 03, 2006 8:16 am

Maybe valves / valve springs not operating properly when the Mivec cam kicks in? Is there any loss of power that you have noticed?

Boris · Post by **Boris** » Fri Feb 03, 2006 8:45 am

It could be coming from the flex joint in the down pipes / extractors.

BuCkEt · Post by **BuCkEt** » Fri Feb 03, 2006 12:25 pm

Boris wrote:It could be coming from the flex joint in the down pipes / extractors.

My car does this anywhere after 4k RPM. But this only occurs on lift off throttle.

However this is more of a loud raspy noise than a high pitched whistle. Caused by gas finding it's way out of the flex joint just after the extractors.

payaya · Post by **payaya** » Sat Feb 25, 2006 7:44 pm

Have you checked your cats? It sort of explains the more on load, quietens down at 7k as load is less.

SG · Post by SG » Sat Feb 25, 2006 9:29 pm

Nacho wrote:Maybe valves / valve springs not operating properly when the Mivec cam kicks in? Is there any loss of power that you have noticed?

mivec starts at 5800rpm, this start at around 4k...

feels like theres heaps torqueloss before 4k.. and if the variable intake manifold motor is disconnected it still makes the noise. so either the motor is causing the butterflys to be stuck half open, or its not that at all

might be the flex/cat pipes.. havent checked that...
not sure what you mean by the load quietning down in the exhaust the higher you rev

payaya · Post by **payaya** » Sat Feb 25, 2006 9:32 pm

theres more load on an engine at low to mid rpms thats why you probably are getting less of a noise at high rpms.

Go for a spirited drive, get your hand near the exhaust not too close those star far away, get someone to rev the car, is the gas really really hot, more than normal? That usually is a sign of a blocked cat. Also torqueless is also a classic symptom. Does your car feel and sound like its got a 1.5 inch exhaust system?

Take the cat off doesnt look like theres much to it anyway