Right... Time rto set a few things straight for you guys.

What "chatter" actually is, is turbo-stall. It is found on most tubo cars not running dump valves and noise-restricting air filters. What it actually is, is when you lift off the throttle or change gear, then throttle butterfly snaps shut stopping the charge air you have already built up from entering the engine via the throttle bodie. This air has to go somewhere, and without a vent (dumpvalve) it is forced backwards through the charge air system and out of the only other exit - the air filter. To get out of the air filter it msut pass thru the turbo. Now the turbo is still spinning away, so the air travels back through the blades, effectively "stalling" the turbine (blades spinning one way, reversed air makes em spin other way) The noise you hear is at this point, and is the charge air being " chopped" by the turbine blades.

With a car running a d/valve, you don't really get this "chatter" as the majority is vented out of the dumpvalve to atmosphere (eg: your Bailey DV24/26 etc, and any one that makes the "p-tish" sound

Re-circulating Dump Valves

No sorry, they don't. As their name suggest's, re-circ d/valves re-circualate the escaping charge air back into the charge air system, usually before the turbocharger, which aids in a tiny version of anti-lag really (by forcing the air back in before the turbo you keep it spinning for when you come back on the throttle)

But this doesn't make a "chatter" noise. In fact it doesn't make any noise, and is virtually silent. Manufacturers use these d/valves for this very reason as regular Joe doesn't want nor is interested in "P-TISH!" or "cha-cha-cha-cha" noises. It also helps in the long run with turbo life.

Which brings me onto the next point - prolonging turbo life. Most say you HAVE to run a d/v otherwise the turbo will explode in millions of bits. Not so. YOu only really need d/v's on cars running fairly large ammounts of boost in ratio to the turbo size (determined by ammount of air the turbo can flow)

Your T3 turbo'd ERST doens't really need a d/v till you running more than 18psi. I would still run one well before this, jsut as it will assist in prolonging the life of your unit.

One last note on chatter. Cossies can chatter, Fiesta turbo's can chatter, but on the whole, Escort turbo's cannot. Why? COs Cossies and FRST's turbo's vent directly into the air filters, where as the ERST's turbo have a metering unit between the turbo and the air filter. With the throttle snapped shut, the flap on the metering unit is also shut, preventing any charge air from exiting back out of the air filter. Cossies and FRST's (as with most turbo cars like this) will chatter louder with the sound-restrictive airbox removed in favour of a cone.

Hope this is of some use to everyone and dismiss a few myths and straighten a few fatcs