Cim whistle on acceleration

[Buzzman11]

Hi, I have a Chimaera 500 which runs really well but makes a loud whistling sound on reasonably hard acceleration. Accelerate less or rev in neutral and there's no whistle.

I've checked the intake side (air filter, hose, plenum etc) even with smoke test, for leaks but couldn't find anything wrong and I can't see any visible indication of an exhaust leak.

Any suggestions would be greatly appreciated.

Thanks B

[igiveup]

Check stepper motor, they can whistle.

[ClassiChimi]

My Serp timing belt tensioner has just started whistling but it's obviously constant in noise!
A simple way to check is put a 15 mm socket on the pulley wheel, turn clockwise which will loosen the belt and spin the wheel,
if it's silent move on!
It takes seconds so worth discounting.

[seeby]

Turbo.? They whistle

[Hedgehopper]

Idle adjustment screw on plenum could be leaking air?

[carsy]

Does it still have the throttle heater plate on the underside of the plenum.

If this has been removed to tidy things up, one of the 4 holes will need blanking as it goes straight through into the plenum. The other 3 don`t brake through. If the blanking bolt that is used is too long or short and not flush with the inside of the plenum it will whistle under load.

[QBee]

If you are in't North, it's probably just a butcher's boy hitching a lift on his rounds.
Or the supercharger

[Loubaruch]

I would recheck your exhaust manifold for leaks.

Either use a stethoscope or I find a fine goose feather (down) on a length of welding rod to be very effective.