wastgate chatter

Initial-D · January 04, 2007, 01:43:31 PM

Yes you do Laeeq!

Its normal on single setups to get a flutter, even with a dump valve installed and when I was at .8 bar!

CraigN · January 04, 2007, 02:47:05 PM

My cossie never blew up once during my ownership

did do a headgasket tho.

On cossies people tend to install the BOV close to the throttle however on a lot of jap machines i see them installed on the hotside before the intercooler.

Which did you hear was better ?

TonyC · January 04, 2007, 03:09:50 PM

I\'ll have a look at my turbo notes at home and get back to you.
I was joking about the Cossie

I\'ll be racing agaisnt a couple of Escort cossies this year - Damn those things make power!

RAW · January 04, 2007, 04:22:30 PM

mine has always made this noise when you let off the throttle, along with the noise from the dump valve. it only does it at part throttle though-on full throttle eg. a gear change it doesn\'t make any noise and you only hear the dump valve.

i have been to tuners, garages etc and they have never commented on it in a negative way and say it isn\'t a problem. is there any chance peeps could have the noises mixed up? i\'m sure there is a thread on here from ages ago where \'wastegate chatter\' or \'compressor surge\' was actually something else.

i have standard twins btw.

CraigN · January 04, 2007, 04:38:18 PM

compressor surge is something totally different.

This is caused by a restriction of gasses exiting the engine (usually a small turbo exhaust housing) while the turbo is still trying to force air into the engine.

This is very dangerous but is not the same as "chatter" or compressor stalling

TonyC · January 05, 2007, 09:51:41 AM

Ok, the dump valve should help throttle response becuase it prevents the compressor stalling (making the \'chatter noise\').
When you shut the throttle you\'ve got compressed air in the intercooler/pipes leading up to the now closed throttle butterfly. That air wants to go somewhere as it is under pressure, and usually goes back through the compressor blades. This stalls the compressor, puts presure on the wheel and slows it down.
A dump valve allows that pressuruised air to escape, this means the compressor wheel is not stalled by the air and is spinning freely and gently slowing due to the reduction in exhaust gasses spinning the turbine - so when you get back on the throttle the compressor should spin up quicker than if it had stalled and been prematurly slowed by air being pushed back through the compressor - as happens with no dump valve.

The dump valve location does\'t effect the response as such (my mistake earlier), the reason for the different location is heat.
As air is compressed it gets warmer, and looses density. That\'s one of the reasons why we push air through the intercooler -to loose this heat and increase air density again (density is good for power).
If we vent after the intercooler than we are wasting intercooler efficieny). We are forcing the recently compressed and heated air to travel through the intercooler before it is vented. This is air we are not going to use as the throttle has been shut. This is extra heat the intercooler is having to soak up. By venting before the intercooler we are venting the heated air before it reaches the intercooler and therefore we are not wasting intercooler efficieny by having it cool air we are only getting rid of.

If you see what I mean.

It\'s going to be academic for a road car anyway - but it is little details that make up a good circuit car.

BlitzBoy · January 05, 2007, 10:16:37 AM

oh no not this story again about dumpvalves and bovs and recirc valves, not having one of these valves will not break your turbo blades etc, these valves are only fitted by manufacturers as noise suppressors to stop the so called "chatter" noise. Will post a link later from people in the know

BlitzBoy · January 05, 2007, 10:43:29 AM

HOGWASH TO DUMPVALVES

here is a link, take note from RICE RACINGs comments he knows his stuff and is a major tuner in Oz

http://www.rx7club.com/showthread.php?t=495277&page=2&pp=15&highlight=bov

TonyC · January 05, 2007, 11:31:16 AM

Interesting stuff, but why is he banned from the forum? And I\'d need to know who he is to bring credibility to his comments. All I see is one post from a banned user in an internet forum. My reason for considering a BOV is based upon published techincal articles from people who make a living building, designing and installing turbo applications from scratch.
A discussion on BOV\'s always seems to prompt some strong feelings from people (for some reason).
There are applications where a BOV is needed to protect the turbo - usually when you start running high boost or go often from WOT to shutting the throttle down rapidly. From a racing prespective I\'ll fit one for this reason. A lot of turbos/boost levels get away without one. But the mechanics of what the BOV does and what it protects are still valid. It\'s up to the owner of the car to decide if they want to fit one based on the information available.

BlitzBoy · January 05, 2007, 11:42:08 AM

The reason why he was banned is there is a big fight about AI on the forum and other members on there, trust me he knows his sh*t
Tony in the 80\'s Formula One Turbos did not use BOVs, Rally Cars do not use BOVs.
Ask yourself why, the main reason why is the "drop" in performance, the repressurizing of the intercooler and pipes is the main reason as the BOV releases all the pressure that the turbo has built up, so the turbo has to work harder to repressurize therefore time is lost in building up the pressure again so this will cost you time in the quarter mile and Track.
There has been no real eveidence I have seen over the years on all these forums that has shown damage due to not running a BOV, plus a turbo keeps spinning even without a BOV there has been no real eveidence of turbo stall.
If there was Stall then this would hurt performance and Rally cars would run them.

DRAGON · January 05, 2007, 11:50:19 AM

With most tech arguements, you seem to get two distinct perspectives. However I find that the ones who are usually right are generally in the minority, and I think they should be more happy to let the others trundle down the path of blissful ignorance.

BlitzBoy · January 05, 2007, 11:53:20 AM

Just to add I have driven 10k Miles on my turbo no BOV, still like new the blades, my spool up time between gear changes has been practically instant

CraigN · January 05, 2007, 12:08:39 PM

sweet someone who agrees with me for a change

so im not talking complete bollox.

I have some videos of my cossie at the nurburgring.

not only does it sound awesome but as in my previous comment my cars have drven sooo much better without a BOV

rmagictastic · January 05, 2007, 12:29:29 PM

FYI... this fellow who i know http://www.rampage-hks.co.uk/remapping.php

runs a mahooooosive power scoob without any bov\'s etc. and neither do the rally cars that he tunes (as metiond in the page)

Rmaj

sadgoth · January 05, 2007, 12:48:14 PM

one of the arguements I have heard on the competition car front is that Rally cars, 80s F1 cars, etc is that the engines and turbos are rebuilt pretty much every race meet, lets face it if we ran cars for 800 miles between rebuilds we\'d get a little pi55ed off!

I\'m not saying I agree with either side, I would say that IMHO running without a BOV should reduce lag as there is more pressure in the system, however prolonged exposure to excessive pressure agaignst the turbine blades can\'t be a good thing for turbo life. Sounds to me as though we have the classic situation, a product has been developed to reduce engine/turbo wear, but potentially will increase lag and increase response time of the turbo. Like all things I guess, we have to make a compromise between logevity and performance.

That is ONLY my opinion, I am not stating fact so don\'t start flaming me!