the shreksta

iTrader: (20)

my car is making a weird sound from the induction kit when on boost from 4k+ rpm,to describe it as best i can its like the air is being chopped up and the car is slow to rev when its happening

it happens in 3rd/4th and 5th only and only happens when im planting my foot,if i build the boost up slowly it doesnt do it and the normal induction suck sound is fine

any ideas?

its a vf35 with a rcm induction kit and a viper (scoobyworx) inlet pipe and a viper (scoobyworx) induction to intake pipe

car is a wrx blob running 1.45 bar boost on sti engine 354bhp

AS Performance

iTrader: (4)

cavitation..............very common on the 35

the shreksta

iTrader: (20)

any way to stop it as its ruining the cars performance?

Fudgey

iTrader: (1)

Is cavitation the same as surge?

As surge sounds like chatter as the engine ve cannot consume as much air as that is being produced by the turbo.

Headwork and high lift cams may sort it if it is surge.

Off to google cavitation now lol

the shreksta

iTrader: (20)

its almost as the car is being starved

the shreksta

iTrader: (20)

and more to the point can it cause damage?

AS Performance

iTrader: (4)

its an issue pretty specific to that turbo, it to do with the hot side being 'too small' as they were specced to "spool" quickly...............

change down a gear

Fudgey

iTrader: (1)

Has it been mapped recently?

As if it is surging this means that turbo is creating pressureised air that cannot be used by the engine, the result is the air that is not used passes back through the turbine compressor. This is bad as it slows down the turbo compressor, while your still on the gas trying to accelerate.

So it will kind of: go-hesitate-go-hesitate-go etc

Fudgey

iTrader: (1)

So it needs a larger rear housing to slow the turbine wheel alyn?
Or cut back blades (or does cut back blades make it spin faster higher in the rev range? I cant remember lol)

the shreksta

iTrader: (20)

hhmmm how would changing down a gear help? maybe I should look for a new turbo like a vf48 instead

Fudgey

iTrader: (1)

The higher the engine revs the more air it can consume.
Thats why turbos tend to tail off at high rpm. Not because they 'run out of puff' but because the engine ve is greater than the turbo can supply

But the issue your having is that its making more air than the engine ve can consume at lower revs

Dont suppose you have the compressor map for your turbo?

the shreksta

iTrader: (20)

you mean the graph?

XDevil666

Mine kind of does the same with a VF22, makes kind of a howl sound if I floor it at high speeds (around the 100 mark)

Fudgey

iTrader: (1)

No mate, the actual compressor map for your specific turbo

It looks a bit like a thumb print lol, will show how much air it flows at certain boost pressures.

mikescooby

iTrader: (2)

I would contact duncan as he will look into it on his maps

mikescooby

iTrader: (2)

Ive herd that sound before on a uno turbo sounded good. But not doing it any good

XDevil666

It's only like a short squeak noise, I agree I don't think it will be doing my car any good, but speeds around the 100 mark won't be doing my licence any good, so not too much of an issue

But I'm either going to look at making sure I have more airflow at the filter, or putting the original air box back on and seeing if that gets rid of it a bit.