Wastegate and Recirculation Valve how & when?

[gotmeaT-5]

This is going to be dumb to you experts but to us mortals it's not a couple of questions on the Recirculation and Wastegate valves

Exactly how and when do they operate ? I know they operate in a different way to the dump valve and thats as far as it it goes.

When does the Wastegate open ? I'm guessing mine is working as I haven't blown the engine up yet
When and how does the Recirculation Valve work ? Again guess mine works

[princepugh]

The wastegate is essentially a controllable turbo by-pass valve for the exhaust gases - as such, it is used to vent excess exhaust side pressure to control the boost the turbo produces. So, it will be closed at low rpm to get the turbo spinning but will open at high rpm/ throttle to control the boost.

The recirc valve vents boost on the charge side when you come off the throttle, in order to stop the turbo blades stalling, which helps prevent 'lag' when you get back on teh gas. It's called recirculating because it passes the charge back into the air intlet after the MAF.

A dump valve simply dumps the charged air you don't need off throttle to the atmosphere, hence the tshhh!! noise you hear.

I think you can run dump valves quite happily on pre ME7 Volvos but ME7s will use more fuel with a dump valve as it mucks up the fuelling off throttle.

If your wastegate wasn't working then yes, you'd have terrible driveability with typically either very low boost or dangerously high!

If your recirc valve isn't working, you'll hear the shs shh shh blade stall when you come off the throttle. Some difference of opinion as to whether this is good or bad for the turbo but on balance it's probably bad in the long term.

HTH

[t5_monkey]

This is going to be dumb to you experts but to us mortals it's not a couple of questions on the Recirculation and Wastegate valves

Exactly how and when do they operate ? I know they operate in a different way to the dump valve and thats as far as it it goes.

When does the Wastegate open ? I'm guessing mine is working as I haven't blown the engine up yet
When and how does the Recirculation Valve work ? Again guess mine works

get a decent Recirculating Dump Valve upgrade + a K&N or similar air intake and you'll feel like a Rally God every time you go for a drive :)

[gmain1967]

This is going to be dumb to you experts but to us mortals it's not a couple of questions on the Recirculation and Wastegate valves

Exactly how and when do they operate ? I know they operate in a different way to the dump valve and thats as far as it it goes.

When does the Wastegate open ? I'm guessing mine is working as I haven't blown the engine up yet
When and how does the Recirculation Valve work ? Again guess mine works

What year/model is your T5? There are upgraded recirc/diverter valves available, but not for all models. As above, dumpvalves will work on pre ME7 models, but can cause all manner of issues with that model on, due to the use of the Bosch ME7 engine management system. This uses a fly by wire electronic throttle, and coupled to the metered airflow system, means a dumpvalve is a non starter.

All the valves work on the same principle i.e. once a pre determined boost level is reached, the valve opens and either recirculates or diverts the excess boost (usually back into the intake), or in the case of the dumpvalve, to atmosphere, hence the noise.

If you are running higher boost, your valve may not work properly, as it will in effect open too early, and the higher boost will never be reached, requiring an uprated spring.

Hope this helps

PS: I have a pre ME7 S70 T5, and I am just starting to work on the recirc valve setup. I have a Forge blanking plate on order and will be removing the recirc valve. What I do after that, I am still deciding upon, but will initially be running it with no valve in place.

Cheers

[p fandango]

All the valves work on the same principle i.e. once a pre determined boost level is reached, the valve opens and either recirculates or diverts the excess boost (usually back into the intake), or in the case of the dumpvalve, to atmosphere, hence the noise.
thats how the actuator works mate. Dump valves & recirc valves are kept shut by positive pressure from the manifold. So when your on throttle air from the manifold is keeping the valve shut, when you back off the throttle (ie to change gear) there is no opposing air so the valve is forced open by the excess air causing by the momentum of the turbo continuing to spin so it can be let out of the system

[gotmeaT-5]

So unlike the hissing style of valves fitted to Scoobies/Evo's ours don't make noise just sit quietly doing their stuff? The boost level on my 97 855 T-5 will climb to over 12psi on the gauge on the motorways when overtaking the dreaded caravan or trucks playing dodgems, no idea if that's low for a chipped T-5 automatic

[p fandango]

So unlike the hissing style of valves fitted to Scoobies/Evo's ours don't make noise just sit quietly doing their stuff? The boost level on my 97 855 T-5 will climb to over 12psi on the gauge on the motorways when overtaking the dreaded caravan or trucks playing dodgems, no idea if that's low for a chipped T-5 automatic
if its still standard on the valve side of things then the factory recirc valve will just feed the excess air back into the air intake pipe so yes its nice & quiet

standard boost should be about 10psi, so high for standard but low for a remap. I'd look for leaks in the vac pipes to the actuator etc

[princepugh]

If you're chipped/mapped you'll be able to hear the recirc valve doing it's thing when you come off the throttle.

First port of call for boost issues is the TCV/BCS and associated hoses followed by charge pipe inteconnections and wastagate/actuator in my book.

[gmain1967]

thats how the actuator works mate. Dump valves & recirc valves are kept shut by positive pressure from the manifold. So when your on throttle air from the manifold is keeping the valve shut, when you back off the throttle (ie to change gear) there is no opposing air so the valve is forced open by the excess air causing by the momentum of the turbo continuing to spin so it can be let out of the system

Ahem, apologies. I reread my post and can only put it down to early morning/brain fade.... What a load of b******s....! I knew what I meant to say, just got it a bit a**e over elbow. Thankyou pedro for the correct description! Think I'll have a coffee before I try any early morning mechanical speak next time. lol

Cheers

[p fandango]

Ahem, apologies. I reread my post and can only put it down to early morning/brain fade.... What a load of b******s....! I knew what I meant to say, just got it a bit a**e over elbow. Thankyou pedro for the correct description! Think I'll have a coffee before I try any early morning mechanical speak next time. lol
lol no worries mate, hope it didn't come across as if i was trying to embarass you. Can't beat a cup of coffee to wake you up in the morning, especially if its as bad as the one's from our canteen lol

[Al115]

Driving an Evo at the moment. The noise is unreal.... but would be out of place on a Volvo. ;)

Induction noise on T4s/T5s is, however, something I'm a HUGE fan of :D

[gotmeaT-5]

Is there any way of telling exactly how the ECU has been chipped? I know it has as I've had a look so there's definately something gone on inside though I don't think the car is as quick as it could/should be or not as quick as the T-5R whizzing around Great Yarmouth couple of weeks ago and every so often my car seems to drop revs for a brief part of a second

All intercooler hoses have been replaced with Genuine Volvo ones to replace the old split gooey ones that were on along with a full basic service including gearbox flush

[streaky744]

my last volvo (1999 V70 T5 (ME7 engine)) had a dump valve and remap and ran perfect so why are you saying can't put one on an me7 engine? thought quite a few people had.

[p fandango]

my last volvo (1999 V70 T5 (ME7 engine)) had a dump valve and remap and ran perfect so why are you saying can't put one on an me7 engine? thought quite a few people had.
it is quite rare for people to put them on ME7's because they are so fussy, i have heard of a few people like yourself who have done it & been fine, but have also heard of them causing idling issues & CEL light problems