wastgate chatter

[BlitzBoy]

lol no flammage needed Mark.
I like evidence, never seen broken blades due to pressurised air of a cars turbo system.
OEM BOVs and recircs are designed in mainstream cars as noise suppressants as they stop chatter/compressor surge type noises

[CraigN]

i have seen a snapped shaft on a gt rollerbearing turbo

on a cossie running over 2 bar, but was told the shafts on them are weaker

[TonyC]

Interesting stuff again - this is how it should be: decent discussions. I understand about the loss of presurisation within the inlet system and the negative effect it can have.
But there is a lot of weight in the argument of why the major race teams don\'t use them - they are re-built frequently and long term wear isn;t really a worry for them.
And you must see that if you don\'t vent the inlet when the throttle is shut then that air has to go somewhere?

There is obviously more to this, why do so many technical discussions on turbo\'s advocate the use of a BOV (for road or competition). I don\'t like to copy what another tuner does - I like to understand why and make my own choice.
Have any of you who recommend no BOV got any information on the positives of no BOV, from a clear technical perspective - rather than from a experience/observational perspective.
Perhaps you are right, perhaps with the more modern turbo vanes and designs the backwash of presurised air doesn\'t cause premature wear, maybe it never did - but I\'d like to know more

[CraigN]

i will try and dig up a post from a ford forum i once read from a tuner.

One thing i remember him saying was that BOV\'s can cause overspooling of a turbo should they become stuck open or faulty etc.

Dont quote me on that tho i will try and find the post.

[TonyC]

That would be great, cheers.
It\'ll be something to read as I trundle my way down the path of blissful ignorance

[BlitzBoy]

There is a massive thread on Ausrotary on this from both sides of the fence.
Another thing to think about , Rally teams its all about reliablility that cannot afford to have a turbo go mid stage so surely a cheap BOV in respect of the cost of a turbo they would fit it to prevent this, they dont as they feel it does not contribute to reliability.

[rx7veilside]

go outside of the rx7 market and lots of people run without bovs.the only reason to running a blow off valve or whatever u want to call it is to rlve reverse airflow over the turbo blades perf with or without will be fractional and 99% of us will not notice the performance difference manufacturers cant afford to have warranty claims so they fit bovs to rlve poss stress on the turbo.it wont happen over 1 week or 1 month but stress will occur.rally cars will be stripped and rebuilt far to regular for it to be an issue but road cars are different and i would be apprehensive buying a turbo car that hadnt been running a dump valve.each to his own but i wld rather have a safe car than take a chance to have what soundslike a horse blowing its nose everytime i change gear

[andysmee]

is there any reason you couldn\'t have a more intelligent BOV which releases pressure up to a certain point but maintains pressure below a certain point? You could then balance the BOV lower cut-off point with the point at which the inertia in the turbo causes it to stall (if indeed it does stall)
 
BTW What actually makes the chattering noise?

[sadgoth]

(according to several encyclopedia)Motor sports governed by the FIA have made it illegal to vent unmuffled blowoff valves to the atmosphere.

see here for the pro BOV / CBV arguement: http://en.wikipedia.org/wiki/Blowoff_valve

http://en.wikipedia.org/wiki/Wastegate#Wastegate_chatter_myth

[BlitzBoy]

perf with or without will be fractional and 99% of us will not notice the performance difference manufacturers cant afford to have warranty claims so they fit bovs to rlve poss stress on the turbo.

Dis-agree with the minimal performance difference, Had a single turbo 300zx and it took ages to spool up in gears it had an after market HKS seq BOV fitted, as soon as I disabled it the performance was returned. The 300zx twin turbo had recirc valves fitted as standard due to the MAF system of metering air as not to spoil the tune and to suppress the noise of the turbo chatter this is stated in the Nissan literature no mention of it to protect the turbos.

IMO opinion on modern Single turbo Rexys you dont need a BOV

[MillSpeed]

Until I see back to back quarter mile times proving that an RX7 is quicker without a dumpvalve and conclusive evidence there\'s no negative effects of compressor surge then I\'ll err on the side of caution and keep the dumpvalve.

[BlitzBoy]

Until I see back to back quarter mile times proving that an RX7 is quicker without a dumpvalve and conclusive evidence there\'s no negative effects of compressor surge then I\'ll err on the side of caution and keep the dumpvalve.

well cant prove it on a RX7 but on my single tubby 300zx a few years ago I posted consistant 15.4s as soon as I disabled my BOV my in gear boost response improved and my quarters improved to 14.8s no other mods were made

[MillSpeed]

Daym, that\'s quite an improvement. I wonder if someone would be willing to do a little experiment at one of the drag meets? Say do five runs with, and then 5 runs with the BOV removed/disabled.

[andysmee]

someone must be up for this! would be nice to actually put this to rest. I have a G-Tech Pro if someone\'s willing to try it on the road at a meet rather than wait for the strip

[DRAGON]

"There is a common myth in the automotive world about so called "wastegate chatter", a noise created on lifting off the throttle in a turbocharged car. The sound is commonly described as a chipmunk or a rattlesnake and is often stated incorrectly as being a result of the turbo\'s wastegate closing.

The noise is in fact the air compressed by the turbo passing back through the compressor housing of the turbo after having hit the now closed throttle plate.

A blow-off valve (BOV) will usually eliminate this noise, but in some cases, i.e. where it doesn\'t open fast enough or is setup to only react to high boost, some chatter will remain.

The chatter noise is very noticeable on WRC Rally cars, where no BOV is allowed."