turbo stalling

[brett craig]

Up until today i have quite happily ran my 16T without a recirc valve or dumpvalve, thus stalling the turbo ( for the noise ), this has run 12psi with no problems, question is. now ive had the hlm 304 fitted its running 18psi, is this likely to be to much pressure for a stalling turbo ? if so i'll go back to my recirc valve.

[p fandango]

18psi still isn't alot of pressure in the turbo world so don't think you'll have any issues. Have you noticed any extra lag between gear changes with no valve? mine seems just as quick to spool as before

[t5_monkey]

Isn't turbo stall a turbo lifespan issue more than a performance issue?

[brett craig]

Isn't turbo stall a turbo lifespan issue more than a performance issue?

my worrys about lifespan are snapping a blade off lol

as for lag its hard to tell to be honest, i think theres certainly a small lull in changes but that could be more clutch related than lag.

[p fandango]

Isn't turbo stall a turbo lifespan issue more than a performance issue?

some say it affects both. With no valve its supposed to stall/stop the turbo so takes longer for the boost to spool back up after a gear change. & at high levels with it stalling it can result in too much strain on the turbine & snap the blades off, but as i say i don't think we're running high enough for that to be an issue (only my opinion tho)

[T5frankie]

how would a turbo compresser wheel stall if its spinning at over 100000 rpm between gear changes?

[p fandango]

how would a turbo compresser wheel stall if its spinning at over 100000 rpm between gear changes?

when you back off the accelerator the butterfly in the throttle body is closed, & as you say the turbo is spinning at a high speed (not convinced its that high tho) so the air/boost its producing now has no where to go so backs up in the system & clogs up the turbo stalling it

thats the main reason dump valves are fitting as close to the throttle body as possible, to drain out as much of the stall air as possible

[Alan M]

18psi still isn't alot of pressure in the turbo world so don't think you'll have any issues. Have you noticed any extra lag between gear changes with no valve? mine seems just as quick to spool as before

It depends on the volume of air being moved.

[brett craig]

well now i'm totaly confused.com

[T5frankie]

well now i'm totaly confused.com

a turbo compressor wheel spins up to 20 x or more than the speed of the engine thats why you are supposed to let the car idle(cool down) after any speedy driving as the wheel is stil spinning and it needs to come to a stand still, hence the need for turbo timers which keep the car running after you turn the ignition off, therefore keeping the oil turning

[t5_monkey]

how would a turbo compresser wheel stall if its spinning at over 100000 rpm between gear changes?

If the air pressure is too high you'll get cavitation on the blades when it's spinning that fast ...

you can also get linear airflow shear and all kinds of wierd effects only a really boring £££££££ would understand.

in essence - it makes the blade vibrate and wears the turbo bearings out.

[Flatout Phil]

This is purely anecdotal, but having shunned a DV for years, fitted one to the R which has a very similar config to yours by the sound of it (well, had a blanking plate with no recirc valve). The pressure dump seems to have two effects, one is that power stops the moment the throtte is lifted - less lurchy and more controllable Be interesting to see how a recirc valve woud feel but somehow cant face the prospect of digging it all out when it works just fine. The second is that I feel I can now shift gears faster, and the feel is more progressive. Mainly it makes a right chav noise that really embarrases the Mrs, but me and the kids love it.

[simpT5]

I've been running my ME7 V70 T5 with a k&n 57i filter and with no dump or recirc valve now for about 6 months and it's been absolutly fine, no warning lights or decrease in performance at all.

My boost gauge shows a steady 14psi on full throttle.

The sound that's produced when the turbo stalls as you lift off the throttle is awesome, especially with the filter!

[gmain1967]

when you back off the accelerator the butterfly in the throttle body is closed, & as you say the turbo is spinning at a high speed (not convinced its that high tho) so the air/boost its producing now has no where to go so backs up in the system & clogs up the turbo stalling it

thats the main reason dump valves are fitting as close to the throttle body as possible, to drain out as much of the stall air as possible

As P fandango says, it's the compressed air attempting to go back through the system, but the problem is made worse due to the angling of the turbine fins. These, like a jet engine, are designed to draw and compress air, in one direction only, and face in the direction of air travel. When coming off the accelerator, unwanted boost is attempting to travel against the correct direction of air travel, thus exaggerating the problem, as the fins are against the direction of travel and act almost as a barrier.

This undoubtedly puts stresses on the turbine itself, that it was not intended to see routinely, so my view is that long term longevity could be adversely affected. However, other turbo issues such as lubrication, cooling, play in the shaft etc, will probably have a greater bearing (no pun), on lifespan, than running without a recirc/dumpvalve.

[johny the monkey]

i have seen people on here putting that they have fitted a blanking gasket to get rid of the recirc. I have emailed Rspec about such a gasket and they replied with just a 25mm blanking plug for a turbo pipe, which i dont think is what I want or is what has been mentioned. Could someone tell me were to get one of these blanking gaskets.

[Jamest5r]

Send Brett a pm mate............http://www.vpcuk.org/forums/showthread.php?t=30820