Bov And Wastegate

[Goose]

CJF - I'm thinking about fitting mine with an external wastegate as I love the sound of it more than a BOV. Dunno if any of you guys have noticed, on gear changes there is a very faint fluttering sound, this is wastegate chatter, and is *I believe* caused from not quite enough pressure on the wastegate to open it fully, but only partially.

The BOV on our cars is pretty much silent, and although I like the sound of imports fitted with external venting BOV's, I want mine to flutter as opposed to the straight PSSST from a BOV.

Also the best description I've heard of how a BOV works is:- You know when your in an older house, and you have the taps turned on full, and if you turn them off really quickly you hear the pipes in the wall bang and rattle. Imaging the water as air and that turning the taps off quickly is like the throtal body snapping shut, so the same sort of thing 6psi of air, no where to go, bang!! there goes the compressor wheel.

Anyways just my opion on thing.

Happy Boosting!!!

[F6 RAPID]

Essentially, the wastgate (under direct from the boost solenoid and wastegate actuator) bleeds off excess boost - the xr6t is limited to a max of 6psi - as you know. It is a valve-like thing that is situated right beside the exhaust turbine in the turbo.

The BOV vents excessive boost build up between gear changes (what it was meant for). For example, imagine you are motoring along at full throttle nearly full revs, the turbo will be spinning at something like 150,000-200,000 rpm. When you back off the throttle, the turbo is still spinning at these revs but can no longer push air into the motor and the boost builds up VERY quickly in the intake chamber. If this air continues to build, it actually forces back onto the compressor of the turbo and can slow it spinning quite dramatically sometimes to the point of damage. The BOV vents this excess air while leaving the turbo spinning so as to minimise the time taken for it to "spool" back up again when you plant your foot for the next gear.

Does that make sense? Read autospeed, they explain it a little better than me I'm sure.

Didn't you read the rest of the thread Goose??

[bcl]

Goose,

I don't quite know what you're talking about when you refer to the sound of the external wastegate.

If set up correctly (legally) it should not be loud at all. Exhaust gas is dumped with more control and a much larger valve than standard, and it's easier to install different springs to suit your requirement. Done legally the exhaust is re-routed back to the main exhaust, and it should be no noisier than standard.

It is VERY noisy if you (illegally) dump the wastegate gas to atmosphere unmuffled (that pipe is called a grenade ... you'll know why when you hear it). ... especially when you run in excess of 1.5 bar!

Similarly, not sure why you’d get wastegate chatter in this situation. If you are accelerating hard on full boost, and the wastegate is fully open, then change gear (in a manual) the wastegate should close instantaneously, then open back up again when you step back on the gas. I have (many years ago) experienced some chatter when running a Calais turbo with around 12lb boost, and the spring tension was too tight such it forced the wastegate closed when pressure was trying to open it, doing this several times giving a shuddering effect…. But this was on acceleration, not gear change. Actually, one of the reasons why you’d chose an auto over a manual is to keep the boost level up in the turbo during gear change, since the change occurs much faster in an auto.

With low boost levels chatter and other problems should not occur. If so, I’d take the car back. You never know, the turbo wastegate actuator could be faulty, but I doubt it.

bcl

[Goose]

Sorry Turbo 6, wasn't meaning you were wrong, I just mean that as a Layman's terms explanation

[F6 RAPID]

Sorry Turbo 6, wasn't meaning you were wrong, I just mean that as a Layman's terms explanation

Definitely NO offence taken! :D :D :D

[Goose]

bcl - see what you mean about the wastegate shouldn't make noise on gear change, so do you think maybe the noise I hear could be compressor surge from the BOV not working effectivly???

[bcl]

Goose,

Probably. Can't really say. You could isolate the problem by jamming closed the wastegate for a very QUICK test (I've done this before), but this is very risky, you must have a boost gauge, have good throttle control and take extreme care. I doubt you'd do this on a new car (I wouldn't on a new car). As I said, if in doubt, take it back to the dealer. You could contact someone in Ford technical support for advice. Or you can take it to an aftermarket turbo place (e.g NRG or MRT say) and get another opinion, or ask them to pressure test the wastegate actuator for you.

Best advice, under warranty (at least for 6 months), don't fiddle; if you have any queries or concerns go back to the dealer and ensure all communication is documented. That is what warranty is for.

bcl