Andrew Dixon

You <I>can</I> make this noise (and I did)! Simply remove the dump-vale, and plug the end of the hoses. When you lift off the throttle, the boost blows back through the turbo, stalling it and making the 'chattering' noise.

Does wonders for throttle response, but knackers your turbo and puts a lot of stress on the pipework! Try at your own risk.

I only 'tried' this mod for about 10 minutes, and then put the car back to normal again. Was a wicked 10 minutes though!

A better bet for a 'lift off noise' is a cone-type induction kit which will alow you to hear the standard recirculating dump valve. Or as Richie says a dump-to-atmosphere valve can be fitted (although is said to cause overfuelling on over-run).

A.

steve McCulloch

Sound it way different

You could get a Motec with anti- lag - that would be nice - but your turbo would not last long

You could also go for equal length manifold headers

I would love to fit a Blitz - but unfortunately externally venting dumo valves have the 'potential' to damage your engine and therefore not a very good idea

Shaun

Richard,
Yes you can do it

RichieC,
Sorry mate, your wrong.

Andrew,
Your right............and wrong

Steve,
Trust you to say about anti-lag!!!


That chattering as you put it, is wastegate chatter. It is basically the wastgate unable to make its mind up whether to open or close, and is oscillating with the air!

Having a dump valve or not will not enable or disable chatter, but not having a dump valve will certainly amplify it slightly!

Wastegate chatter is caused by boost and boost only (but I have known it to be amplified slightly with the use of an induction kit). So if you want chatter, whack your boost up. I have chatter on my Escort Cossie (1.6 bar of boost) and John has it on his Westfield (2.0 peak boost). Johns is noticeably louder then mine, but that is mainly down to the fact that his engine is surrounded by a thin plastic shell.

Running the type of boost you boys run on your Subarus, DOES NOT REQUIRE a piston to atmos. dump valve for safety reasons. Regardless wot has been stated or represented, it's not needed unless you run excessive boost (These are REALLY used for there noise generally). Of course you keep the standard plastic one, but that is suffice!

Shaun.

richard.heald

The Subaru (and some other) WRC's make a chattering cound when they lift off the throttle.

What makes this noise and how can I make my MY00 do it!

Richard

RichieC

In a word you cant. That chatter is the wastegate fluttering. What you can do is fit either a Bailey Dump Valve (similar flutter) or even better (but hideously expensive) Blitz Super Sound Blow Off Valve. The Blitz (and there are other Japanese valves around which do the same) comes with interchangable elements in the end to allow you to change the noise it makes when you lift off, one of which is pretty wastegate-ish.

Regards

Richie
PS fit one and do some mpeg of it so we can all admire it

[This message has been edited by RichieC (edited 10 December 2000).]

Diablo

Shaun, not wishing to start an argument here, contrary to popular belief its NOT the wastegate that makes the "chirp- chirp" noise, but blowback through the turbo stalling the turbine.

Andrew is right, although a stalling turbo should make throttle response worse, not better.

D



[This message has been edited by Diablo (edited 27 October 2000).]

Blackscooby

Andrew,

You've just explained why my UK94 pops and bangs on the overrun like its got ALS....Using APEXI BOV and an APEXI Fuel controller to allow it run higher boost (1.3 bar), hence I close the throttle and it still runs rich causing it to pop.

**WHEW** another wierd one explained away !!!

PS Isn't turbo stall a VERY bad thing which is why we've all got Dump Valves / BOV's of various sorts to allow the turbo to freewheel effectivly on closing the throttle. I understood that turbo stall put high stresses on the turbo.

Ta

Mark


[This message has been edited by Blackscooby (edited 27 October 2000).]

Blackscooby

Steve,

How does an external BOV damage your engine ?

Ta ~ Mark

Shaun

Diablo,
Wheres that bleedin Haynes manual!!!!!! Blowback.....I dont wish to know about your past times thankyou!!!!!!

Yes your correct, a stalling turbo could scupper throttle response. But you've got one as standard, so you just need to keep that one!

Andrew Dixon

Although the turbo <I>does</I> stall with no BOV, the pressure in the intercooler and pipework between the turbo and inlet drops away much more slowly than it does <I>with</I> a BOV.

So, when changing gear quickly the engine receives boost straight away rather than having to wait a split second for the boost to build up again. The turbo does need to spin up again but this loss is outweighted by the benefit of keeping pressure.

I am of the opinion that the BOV is there mainly to prolong the life of the turbo and reduce the stress on the pipework.

I understand that a dump-to-atmosphere BOV on a standard Scoob can cause overfuelling on the overrun. This happens because when the BOV operates metered air (that has been sucked past the air flow meter) leaves the inlet system. The ECU has no way to know about this and supplies fuel as if the air was still in the system, hence it runs rich for a short while.

Hope all that waffle makes sense to someone!

Andrew.

MorayMackenzie

Gold stars for Andrew Dixon and Diablo...

The car makes a lovely sound if you run with the BOV blanked off... throttle response is actually improved to... it will, however, subject the turbo to a new series of stresses.


Steve,
Vent-to-atmo bovs can cause problems if your ecu uses the MAF sensor... I don't think your one does. Oh, and using antilag 100% of the time will eat turbos/manifolds, but you can't really use it on the public road anyway, it makes the throttle too sensitive for typical uk roads (trailing throttle to 10 or 12psi over a couple of mm of throttle travel). Antilag can be mapped to be more or less mechanically sympathetic, depending on application and support budget.

Shaun,
At what boost levels am I allowed to consider uprating my BOV? Just thought I'd check... Oh, and while you're here, how much boost should I be running on my car?

Moray

Blackscooby

Moray,

Would mine UK94 use the MAF sensor ?
as I use an APEXi BOV, and have used various none std BOV's for a couple of years with no problems.

Sadly they banned ALS from Hillclimbing at Harewood otherwise I'd have had a crack with it !

Cheers

Mark

Shaun

Moray,

You will never have to upgrade your dump valve........when, sorry IF, you reach puberty boost give me a call.

How much boost should you be running on your car....Hmmmmmmmm, the boost level that is commensurate to your driving and track experience/ability........ZILCH!!!!!!!

Shaun (Make sure you get up abit earlier mate )

[This message has been edited by Shaun (edited 27 October 2000).]

[This message has been edited by Shaun (edited 27 October 2000).]

johnfelstead

There is an awefull lot of bollix and misinformation floating around about dump valves. Must be the biggest single con by the tuning trade in the history of turbo tuning.

The reason car manufacturers fit BOV's is to prolong the life of the turbo, to allow them to get away with selling cars fitted with 300 degree thrust bearings.

Having a BOV on a turbo engine reduces throttle response, it allows boost that would be there to bleed away.

Fitting an aftermarket BOV that vents to atmosphere is bad news on an engine that uses a MAF sensor to meter airflow.

Removing a BOV from the system will give you better throttle response than having it there. Do this with a standard turbo and you will reduce its life.

If you want to run without a BOV to get better response then a good idea is to use an uprated turbo with a 360 degree thrust bearing. (I have run normal 300 degree bearing turbos without BOV's for over 12 months on track days and road without a problem.)

The only time it becomes esential to use a BOV is when you get to using turbos the size of an RS500 full race T4. Anything smaller than that and you do not have any problem whatsoever without a BOV.

No WRC car runs a BOV, WRC spec anti lag systems wont work with a BOV.

Turbo's of the size we use on our subaru's and cosworth's do not suffer from reverse pulses stalling the turbo, thats complete bollox. I have discussed this at length with WRC engine builders and they all agree this is not what happens.

The chatter is the sound of the exhaust gasses passing through the waste gate button in the turbo housing. You need very high exhaust gas speeds to cause the waste gate to chatter, this is something you only start to see when you run high boost. WRC engines run at 34PSI boost at low revs (3000rpm) and this is bled away as the revs rise to stop the air going supersonic as it passes through the 34mm turbo restrictor. This is why the chatter is more noticable at low speed transitions as the revs are lower and the boost is much higher on WRC cars.

The boost curve is far more conventional on my own engine, that gives 26PSI boost at 3300rpm and then only drops 3psi till 6000rpm so i get chatter right accross the rev range.

Do i use a BOV? NO
Do i need one? NO
Does my turbo have a 360 degree bearing? Yes

Blackscooby

John,

Thanks for that....I think I've been had good and proper in that case after spending many hard earned sheckles on an APEXi BOV. I think I'll have words with em on Monday as its got to go back to have the boost controller set back up again. Any views on taking a UK94 with Cosworth Pistons, Group A gaskets over 1.3bar ? Cos I'm arguing with the Co. at the moment about this. They say its not safe. I don't want to slag off the Co. on this BBS ~ it wouldn't be right, but they are in danger of loosing me as a customer.

I'll step down off my soap box now, Sorry for moving off the topic.....

Should have kept with the original Subaru BOV in that case...shame I was mal-informed at the time.

Flip John, 26PSI...I ran mine at something similar for a "while" at Harewood Hillclimb. An engine full of bits shortly followed. I'd be more than interested in talking off-line re obtaining more from my engine and how thats possible.

Cheers,

Mark.

johnfelstead

Mark, my engine is an escort cosworth turbo, not a subaru. 26psi on a cosworth is nothing special.

I am not going to say yes or no on your question with regards to what boost is safe for you. What i will say though is that running an engine that uses a boost controller that increases the boost but does not alter the timing or fuelling is asking for a melted engine. The fact you have group A and cosworth spec components will not save you from this. If you want to run higher than standard boost safely, you need a remap to be safe IMHO, this is hightened if you plan on driving on a track day. Engines that are badly set up can survive in many instances on the road, even with quite poor mapping because you are full throttle for a very short period of time. Take this on track and it will melt!!

I drive a 22B regularly that is running 1.3Bar boost, mapped by BRD, it has a wonderfull delivery of torque up to 6000rpm, very impresive. Above that the boost is bled away as the owner of the car specifically asked for a very safe map for the engine. It would be a significantly faster car if the engine was mapped to keep the boost at higher revs, but this is taking the engine closer to det than the owner was looking for.

I think the point i am trying to make here is that having a proper remap allows you control of how far you wish to stress the engine, and allows you to have some margin in reserve for a bad batch of fuel.

The impreza engine is a weaker engine than say a cosworth, partly due to its alluminium construction. Taking a standardish spec engine above 1.3BAR makes me nervous, doing it without a full remap i would never consider myself.

These are just my own opinions though, i am sure there are people who would disagree.

Blackscooby

Ta John,

Didn't realise you were talking Cosworths here. A mate of mine hillclimbed a Saph Cos 4x4 with a HUGE amount of boost 30+ PSI,
.

I run an Apexi fuel controller to try and map the fuel slightly better but I would agree that this can't be anywhere near as good as a full mappable ECU by MOTEC or some other system.

Have considered trading for a Escort Cos group N machine but I don't know if I could live with one day in day out.

Cheers for your swift response.

Mark.

Shaun

John your a star

Diablo where shall I post the Haynes manual to????

Moray....keep reading

RichieC

Johnfelstead, exactly how I understand it.

Apologies if anyone felt I was talking rubbish, this is what I was told by a WRC Subaru team boss. Ask them "whats that noise" and theyll say "wastegate flutter". Simple as that. Whether or not this is the case, Im not sure however this is how its been explained time after time.

I wasnt aware of this whole blanking off the BOV thing, but this may be a different way of simulating that same noise ??

Pros and cons of doing this - may be worth dicussing more??

As for fitting a cone type filter, makes the standard BOV much more audible as Andrew says but its a different noise....nice though


Richie

WALKER

This is a question that has always had me wondering.
Since i had my first scooby i have been trying to get this noise, its very noticable on the WRC cars.
I have always been led to beleive that it is wastegate flutter, my brother in law had a Sapphire Cosworth and you could hear it distinctivley. No, it wasn`t the dumpvalve, that was a seperate noise alltogether. The car ran a k&n cone filter, Castle performance stage 1 conversion and a bailley dumpvalve. So why would that car produce the sexy WRC sound and not our beloved Scoobys.

The closest i`ve got to it is by fitting a Forgemotorsport dumpvalve. It doesn`t give the wooosh sound, its very, very close to the sound of the WRC `waste gate flutter` that i want.
Many of you will be thinking that all of this is a bit Maxpowerish, but who cares, if you want a few extra noises to put a smile on your face, go for it!

Paul
Wheres me coat, i`m off before i get flamed!

firefox

I get it on mine..

Damn annoying..

J.

Butty

iTrader: (2)

So on closing the throttle, where does the back log of pressurised air go to. Does it simply compress then go through the throttle when it's cracked open again? Does it find gaps around imperfect seals (throttle or reverse through turbo)?

Rob W

Hi Walker,
You say you are using a forge motorsport dump valve, is this a dump to air or one of their recirculating valves?
cheers
Rob

WALKER

Rob

This is a vent to atmosphere, and so far i have had no running problems.
Forge motorsport have a policy where if you get fed up with it in 6 mths time you can send it back and they will refund you the £130-00 it cost in the first place.

Paul

rsquire

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Above that the boost is bled away as the owner of the car specifically asked for a very safe map for the engine.<HR></BLOCKQUOTE>

You bet ya sweet bippy I did.. With you lotta mongrels driving it

Still goes bloody well though don't it..

Richard

Diablo

This is soooo ironic.

ROTFLMAO

I understood it was wastegate flutter as well, but then Mike "Rainbowman" Rainbird came over and aggued at length that it wasn't

Now, I don't claim to be an expert and certainly don't take everything I hear/see/read at face value, cos in my experience EVERYONES an expert but FEW are right

HAve to say that Mike's arguments were very convincing.

Notwithstanding all that, I've got a couple of questions.

1) If its wastegate flutter and only happens at high (as in higher that Scoob levels) boost, why did Andrews car do it?

2) I would not have thought the wastegate would open on lift off/overrun, but thats when the noise occurs.

3) John, I bow to your knowledge, and will you warranty my turbo if I blank my blow off valve off .....lol...

D

johnfelstead

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>I would not have thought the wastegate would open on lift off/overrun, but thats when the noise occurs.<HR></BLOCKQUOTE>

Thats exactly when you get the biggest opening of the wastegate, or should i say, the most agresive opening. This is where the ECU is trying to stop the turbo from producing boost as the throttle is closed and so the waiste gate is banged wide open to dump the exhaust gasses down the wastegate and bypass the turbo.

This is aided by the boost presure building up very quickly in the piping between the turbo and the throttle bodie as the throttle is snapped shut. One of the ways the waste gate is forced open so quickly is by the feed from the outlet of the turbo compresor being fed via a solonoid valve to the diaphram of the actuator. The efective presure that is available to do this is higher without a BOV as the boost is not being bled away via the dump valve.

Thats why, when you take the BOV away, the chatter is greater as the actuator is being fed with higher than normal presures and the waste gate bounces.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>John, I bow to your knowledge, and will you warranty my turbo if I blank my blow off valve off .....lol...<HR></BLOCKQUOTE>

errrmmmm nope Like i say earlier, taking a BOV away and blanking its pipes off will reduce the turbo life (although not by a huge amount), i have never seen this as a problem and always use 360 degree turbos that can stand the presures.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Still goes bloody well though don't it.. <HR></BLOCKQUOTE>

Absolutely awesome piece of kit richard. I drove a really nice STi5 TypeR V limited back to back with your 22B and they were both very impresive. The thing i really like about the 22B though, is the huge torque you have below 6000rpm, masively higher than the STi5. The Sti5 felt a smoother delivery as it was a constant pull all the way to the red line but it didnt pull anywhere near as well at low revs. Basically you have to rev the STi5, your 22B is a grunt monster. LOL

Bailey dump valves. I melted one of them on my westie. LOL
Thats before i dumped BOVS completely on the westie after installing my groupA turbo of course

paul w

John,
'quote' Cars fitted without a bov will have improved throttle repsonse,this explains why my 200sx had superb and instant throttle response compared to the scoob and this also explains why they eat turbo's.it also explains why one my uno turbo's did over 120000 miles on the original turbo,as they have standard bov and decent IHI turbo.

If we want to make the standard bov redundant do we just disconect the vacuum hose or will doing this allow it to leak air under boost and still work slightly off throttle.

cheers Paul

[This message has been edited by paul w (edited 31 October 2000).]

johnfelstead

dont disconnect the vacumn hose!!

That will loose you power as the BOV is kept closed by a spring AND the boost presure.

you need to remove the BOV and install 2 blanking plugs to the hoses.

Also remove the vacumn pipe and blank that at the plenum chamber.

RichieC

How easy is it to source a 360 degree bearing for the standard (WRX) IHI turbo?

What sort of cost is involved in doing this? I would imagine the money comes from the sheer time it takes to remove the turbo??

Also, is the 360 bearing permanently fixed to the shaft as opposed to being held on by a spring clip?

Cheers

Rich

PS Are we agreed yet?? Im convinced