My car is 450bhp+ and has got a fairly small air filter compared to most cossies. Apparently it is a high flow one, was set up using it, and cost a fortune etc etc

Under hard boost it chatters / flutters really bad - i cleaned it to see if it made it better but it didn't...is it struggling to breathe when it chatters? am i best replacing it for a larger one or would it make no difference? - i.e. is it meant to do it

 

It chaters cos the turbo is stalling mate you need a dump valve to to stop it chattering
But they sound gay so get a recirc 1

I prefer chatter mine does it all day long

 

If you run a dump valve it will still chatter a little but will be a little safer

with the dump valve, mine chatters great with or without the dump valve

off as most cossies do

 

sounds like surge to me pal, if its "chattering" at wot

your turbo is making more air than the engine can consume, it needs sorting if thats the case



whats the spec?

 

Is it chattering when you let off the throttle or on throttle

 

it reads like at wot,

 

it chatters when i'm on boost, accelerating, NOT when i release - i've got a dump valve...

 

in that case you have surge which is where the engine cant consume all the air being thrown into it. What turbo do you have, what is the spec of the head and what inlet cam you using?

 

200 long studded block
low comp 7.5:1 accralite pistons
lightened and balanced crank and flywheel
steel conrods
high pressure oil pump
cooper ring head gasket
ported and polished head
double valve springs
bd14 exhaust cam
bd16 inlet cam
swedish inlet plenum
modified throttle body
1000cc injectors
level 8 ecu with pectal baby board
group a induction kit
vernier pulleys
t4 turbo-360 degree thrust bearing with cut back blades
38mm external wastegate with screamer pipe
rs500 intercooler
double capacity radiator
group a fuel pump
modified fuel lines

Could it be running lean when its chatting on boost? will a new filter fix it?

 

Surge.

 

A new air filter will not fix it no. What you have is a cycle of events where the forced air into your engine cant be swallowed and then causes the compressor to stall creating your chattering noise. Obviously the stalling creates less air flow into your engine and you get to the point where your engine does swallow what it is given. Once the stalling turbo can wind itself freely again it will throw more air into your engine and the whole cycle starts again. What you need to do is either run less boost, change the spec of your turbo or cap the boost in the midrange so it isnt making full boost until further up the revs. I have a standard ported head and a gt30 and no surge.

I am not the most technical person on here and someone else will come along and give you a more technical description of what is going on but it wonbt go away of its own accord and has nothing to do with your air filter. You could take your filter off and it will still do it.

 

needs mapping out imo,speak to your tuner

 

As above mate

Im sur Stu @ M Developments done a article on this in a fast ford mate

 

there is a thread on surge somewhere on here. i will try and find it.

Edit: didnt take long to find.

https://passionford.com/forum/techni...ighlight=surge

good technical info and description on that thread