R33 Rattle Sound When Boost Comes On?

[BDC70T]

This happened also on my 84 mitsubishi starion... foot to the floor, revs increase then juust as turbo spools up a rattle sound emerges...

no change in power or engine noise, just this slight rattle sound??? and the sound then dissapears as the revs increase.

i've got no idea??

anyone else had this?? or even better, know how to fix it?

thanks heaps for any help!!!!!!

[Duncan]

a metallic rattle? probably the motor pinging. Do you have standard computer? is your fuel system in good condition?

[BDC70T]

a metallic rattle? probably the motor pinging. Do you have standard computer? is your fuel system in good condition?

yeh i guess its sort of a metallic sounding rattle...

Standard computer..

No misfiring, so i'm guessing the fuel systems ok..

The only mods so far have been, 3in cat back/ r32 actuator (10psi)/ grounded solanoid wire..

What is pinging?

[Duncan]

pinging is when the cylinder is pre-igniting ie before the spark is due - it will damage the piston since the cylinder fires while the piston is still heading up. Caused by a cylinder running to lean (ie not enough fuel) or too hot, or both.

its just that it can often occur as the car reaches max boost. Make sure your fuel pump is working OK first if its standard computer since it runs pretty rich on its own.

[BDC70T]

pinging is when the cylinder is pre-igniting ie before the spark is due - it will damage the piston since the cylinder fires while the piston is still heading up. Caused by a cylinder running to lean (ie not enough fuel) or too hot, or both.

its just that it can often occur as the car reaches max boost. Make sure your fuel pump is working OK first if its standard computer since it runs pretty rich on its own.

when you say max boost do you mean at like top end revs? cause thats the thing, it only makes the noise coming onto boost, as it reaches top end doesn't make the sound.. its strange, like something is loose but i don't know..

[MBS206]

It's most likely detonating.

They run more aggressive timing as you're building boost.

Get it on the dyno, get it checked.

[BDC70T]

Detonating? i dunno...

It sounds like a spray can rattle, like somethins loose, but only when boost starts to come on, then disapears as revs increase...

but it doesn't happen all the time when i give it, only every now and then...

i dunno? just thought someone may of had same experience..?

[heller44]

Had exactly the same sound. Main fault was the fuel pump trying to run with only ~10v and the diaphram on the fuel pressure regulator torn. Ran rich at idle, but where it needed it most, right in the meat of the midrange, as the turbos were starting to boogie it would rattle like a handful of ballbearings in a big milo tin, after this point it would settle down.

Very easy to spot on a dyno run, if you haven't yet it is real cheap insurance.