2.0 Turbo - Wastergate Chatter And Dumpvalves

[hexhamstu 9]

so what do fiesta RS turbos have as standard as that makes a chattering noise as standard? ive read all the post but still not sure one what noise a recirculating valve will make? and why pick a DV over a recirculating one?

[sonofsam 5]

A recirculating one shouldn't make to much noise as its not venting into the atmosphere, were as a dump valve is.

As the name suggest a recirc DV will put the vented air back into the system rather than losing it.

[TEKNOPUG 3]

do they vent back into the the intake or the boost outlet?

[sonofsam 5]

 

Air inlet tract it seems, most of the ones i have looked at all have 35mm outlets.

 

On two sample cars where this device was fitted - both were making 1.0 bar boost with a gentle reduction in boost towards the redline. Once the DV30 was fitted, the boost had to be immediately re-calibrated as it would otherwise have risen to 1.5 bar - with no tail off at high RPM. Once the correct 1.0 bar setting was dialled back in (on DPW and MBC equipped cars) turbo lag was reduced and the car felt more sprightly with better in gear acceleration

 

Car in question was a Porsche 944 Turbo.

[Guest rick03054]

They vent into the intake, after the AFM so the air is still metered, but before the turbo, so the air just goes round in a circle through the turbo and it doesn't stall.

[TEKNOPUG 3]

Yeah, that makes perfect sense. If it went back to the boost intake then it wouldn't actually be releasing any pressure and if it vented into the intake before the AFM, it would really screw things up. Looks like it would be pretty easy to mod a atmospheric DV to a ReCirc one.

[sonofsam 5]

Yes it does look easy, maybe the mechanism's may differ though, but there are usually adjustable.

Couldn't on mine as it has perforations all the way round as opposed to a venturi style with one outlet.

Recircs off a scooby are dirt cheap anyway..dont know how well it would perform on a lesser bhp car, guess i'll find out..oneday or another.

[saveloy 8]

One more thing,many a dump valve has been placed as close to the throttle as possible.

This aids throttle response but it does also mean that it sits just after the I/C. So that the dump valve throws freshly chilled air into the atmosphere.

Once the throttle is open again the engine does not benefit from quite the same quality of air.

Best to dump the air prior to the I/C.

[TEKNOPUG 3]

6 of one, half a dozen of the other. Sacrifising power for throttle response and vice versa. Have to wait for Dino's verdict as to which is best....lol

[Sam 4]

http://forums.turbobricks.com/showthread.php?t=11951

 

I been reading up on that myself. I don't think it makes a huge difference either way like teknopug says.

[Henry Yorke 269 3 Cars]

So the conclusion is.... there is no conclusion!!

 

However I think we agree that it is better to run a BOV / Dump Valve (whether it be a recirc or vent to atmosphere) than not.

 

And when it is fitted, popping it before the intercooler seems more logical as you are trying to reduce pressure on the turbine blades, so want to vent the air close to the turbo first and de presurise the intercooler the least to keep lag low

 

The question on Ford wastegate chatter etc is an interesting one. Perhaps this noise is the same as what mine had with the BOV disconnected and it was designed at a time when turbo wear an long life was not considered important. to get the answer to the latter question, we probably need to look at the over paranoid Germanic engineering from the VAG group as if it gave them an extra 1000 miles life in the engine or turbo they would have fitted it whether it lost 50 bhp or not! Any ideas anyone? It is bound to be a recirc if it exists or we would have heard it by now.

 

For the performance question, did the F1 teams of the 80's run them? If it gave them some more power, whether it be 3 bhp or better throttle response, they would have fitted one too.

 

Can anyone confirm the XU10J2TE's boost control setup and how it works; whether it has a recirc BOV and how the boost control solinoid works.

 

As for my skip being quiet, well it is catted and has two silencers (one a Magnex). It does pop a little on overrun but I quite like it quietish! Boost will be tinkered with at a later date though.

[Malachy 0]

the 20v 1.8t vag engines do have a recirc dumpvalve, its actually quite a common failure on them

 

the xu10j2te does not have a dumpvalve from stock, its only running 8-9psi stock though,

the boost controller works by getting a signal from the ecu this then leaks boost to the actuator which is set to 3psi (very low) and opens the wastegate.

 

the ecu signal is determined by a boost map, eg at X throttle and Y rpm the allowed boost will be A

 

hard to explain :/

Edited July 9, 2006 by Malachy

[Sam 4]

Again, theres no such thing as wastegate chatter, the wastegate simply opens and closes to release excess boost (not when letting off!).

 

The BOV opening is going to vent all pressure from the system. The IC will be the same pressure whichever side the BOV is. Most people fit them on the throttle side.

[rich_w 0]

Surely fitting a BOV after the I/C will mean your dumping cool air into the turbo and not uncooled air which would be even hotter by the time it comes out and won't be cooled as much by the I/C?

 

I suppose it depends on how effient your I/C is?

[Sam 4]

Very true, this is why you see most BOV's the throttle side of the intercooler.

[pugrallye 0]

Ford cossies ran a recirc dv as std, couldnt tell you about rs's though as i never owned or worked on one, as far as i know F1 cars never ran any dump valves, but used enormous turbos, external wastegates and 'screamer' pipes (which make the most awesome noise, but would never pass any noise restriction, think it was one of the reasons turbo's were banned).

As it stands in this day and age, only turbo charged cars with roughly T25 or bigger turbos left the factory with dump valves, any smaller and they wernt really necessary, due to obvious tiny boost levels (new golf gti etc doesnt have one as the turbo is diddy)

Also you tend to find once an induction kit or simliar is fitted to a car, whether running a d/v or not the chattering can be heard

Edited July 10, 2006 by pugrallye

[V1 RDE 0]

Well when I blocked off my DV and had no form of 'boost release' at closed throttle, the car felt poor between gearchanges. Took a while for it to build up boost, however it did make that wonderful 'compressor surge' noise, nothing to do with wastgate. Just the air being chopped up by the turbine blades as it travels in the reverse direction and resonates out of the air filter.

 

D/V are definately a worthwhile bit of kit. I ran a DV26 which seemed to work fine, if you don't like the sound get a recirc and plumb it back into the intake. As far a the chav comments go, thats you own personal opinion. I think there cool. If you've heard a RX7 dumping well over bar through a HKS SSQV, you will know what i mean.

[Henry Yorke 269 3 Cars]

the xu10j2te does not have a dumpvalve from stock, its only running 8-9psi stock though,

Speaking to Gav Robinson @ The Derv Doctor on this he reckons they do have a recirc valve (on the 406 SRI's anyway) as he has removed 4 and fitted dumpvalves for customers. He says this is what the pipe where mine dumpvalve is fitted if for.

Anyone got a pic of a 406 SRI standard engine bay?

[sonofsam 5]

Yep agree with that seen loads of pics of 406 sri's with recircs fitted as standard and indeed the take off for it is on that cross over pipe.

Got the pics somewere just cant be bothered to uplaod at this precise time.

Its even mentioned on the wiring diags i think.

[Malachy 0]

thats internesting since on my engine that take off was blanked off.although the engine is from a citroen xantia activa

Edited July 17, 2006 by Malachy

[macaroni 17 1 Cars]

I have an Activa and it is indeed blanked off. Wonder why they used DVs on 406s...?

[sonofsam 5]

Mines a 406 engine and was also blanked maybe only the exec. models got one, will get those pics up later.

[sonofsam 5]

As promised

 

 

[Malachy 0]

As promised

 

 

both are left hand drive maybe a euro thing?

Edited July 17, 2006 by Malachy

[Henry Yorke 269 3 Cars]

So why will the 406 have one and the Citroen not? What are Citroen ones blanked off with?

 

Perhaps it was something discovered over time and applied to the later engined cars to prolong the turbos?