knock level with boost leak

[midlife2]

I have been getting higher then normal knock readings for a week or so and on a drive yesterday when boosting there was a noise of a high pitched air, leak and the boost was maxing out at 1.1 bar when it should have been 1.4ish.Is there a easy way to find where the leak would be and would a airleak effect the knock reading?

[Scott.T]

Originally Posted by midlife2

I have been getting higher then normal knock readings for a week or so and on a drive yesterday when boosting there was a noise of a high pitched air, leak and the boost was maxing out at 1.1 bar when it should have been 1.4ish.Is there a easy way to find where the leak would be and would a airleak effect the knock reading?

If you are drawing in un-metered air via a leak you will run lean and could induce knock.

A leak on the boost control side i.e between turbo nipple and boost solenoid or actuator would cause more boost to be generated as the actuator will be seeing less boost and opening later causing more boost to be genrated
.
A leak on the intake on the engine side of the MAF would cause a lean mix and low boost.

I would check the pipes to the intercooler, as one may of spilt or partly blown off.

What MY and intercooler are you running

[midlife2]

Hi i have a 95 sti ra with apexi ecu and front mount, all the hoses look ok On boost is it possible to have un-metered air via a leak etering the system? as you mentioned it would cause the to run lean and could induce knock.

[midlife2]

Could a standard dump valve cause this if faulty?

[Scott.T]

If air is entering the system the wrong side of the maf the fuelling will be off.
If the leak is causing boost to be lost it may be that the map is marginally off at the boost levels you are now running.
The difference between 1.4bar and 1.1bar will put you in a different region of the map at full load, which may not of had full attention of the mapper when setup i.e the timing and/or the fulling may be slightly out.

re : DV - Blank it off for the moment and see what happens.

Crowman had some very strange noises coming from his FMIC when leaking. No leak was found but all connections were redone and problem went away.

[Jolly Green Monster]

Any leak in intercooler or inlet manifold when on boost will actually leak air out not suck air in.. ie. when above atmospheric temp it is under pressure and like a tyre with a thorn in it the air comes out..

this will actually cause it to run rich as metered air is not entering the engine but the ecu is injecting fuel for it.. this can cause higher knock readings as excessive fuel can cause det and also cause bogging / misfire / hessitation which will increase engine noise (which shouldn't be mixed up with knock), also cause the boost to be lower as turbo is producing same boost but some is leaking out the hole.

high pitched noise could be air leaking from pipes or dumpvalve (check jubliee clips are tight on the pipe and not just tight / at their tightest limit).
Uppipe gaskets can buzz making a high pitched noise.. they usually suck in air as the exhaust gas passes causing the gasket to buzz until exhaust gas speed is higher and you then hear the exhaust louder (sometimes noise not obvious to hear).

You are unlikely to hear an induction leak as your filter will drown out the noise.. the boost would be uneffected by running leaner with a leak in the inlet pipe, therefore I would say it is not the issue.

I would say most likely dumpvalve or jubilee clip leak or whistle is actually the turbo blades and the turbo is damaged.

Simon

[Scott.T]

Originally Posted by Jolly Green Monster

Any leak in intercooler or inlet manifold when on boost will actually leak air out not suck air in.. ie. when above atmospheric temp it is under pressure and like a tyre with a thorn in it the air comes out..


Simon

A leak between MAF and Turbo inlet, will though cause it to run lean.
A leak on the fuel pressure reg vacum hose will also cause it to run lean as the reg/fuel pressure will not rise with boost pressure.

[Jolly Green Monster]

Originally Posted by SilverSurfer

A leak between MAF and Turbo inlet, will though cause it to run lean.
A leak on the fuel pressure reg vacum hose will also cause it to run lean as the reg/fuel pressure will not rise with boost pressure.

you won't head a leak on inlet pipe over an induction kit.. a few times i have suspected a leak here and managed to push finger into the split in the pipe under the inlet where it clamps to turbo.. as OP can hear a whistle it seems unlikely to be that.

yes agreed is the vac pipe is off the reg it will run lean.

Simor