Dump valve/Turbo chatter.

[N1CKY]

Last owner made the car chatter when blowing off air. I think this is destroying the turbo forcing the dumped air back through it. How did he achieve this so i can reverse it ? Did he just fit a really stiff spring in the dump valve ? This is confusing me somewhat. Any info would be appreciated.

Thanks,

Nicky

[grungeisdead]

what make is your dump valve/recirculation valve? where is it fitted in the line? just after the turbo, or after the intercooler?

open it up and check the spring colour, green is the weakest iirc and good to 14psi, ive got a sheet somewhere i can dig out with the forge spring colours on it

[N1CKY]

Its a baily dump valve, I'll check the colour tommorow when im in the garage. And its located after the intercooler, Just before that straight plastic piece that goes to the throttle body. Could the chatter blow oil seals in the turbo ? Its my understanding that the dumped air is forced back into the turbo hitting the turbine blades causing this noise. Im asking because its eaten 2 K03's since iv owned it. Allthough this could be due to the fact i got them from the scrapyard. 


Thanks.

[hayesey]

sounds like you might need a new dump valve.  although where is the vacuum pipe for it plumbed into?  It needs to connect below the throttle plate.

[N1CKY]

Its not plumbed in at the moment because most of the front end is off the car. And i cant remmber where i stole a vaccum from. I'll try and remmember that when putting it together Thanks. Iv got a feeling my spring is too stiff. The guy i bought it was running at 22psi everwhere. And he had lead foot

[grungeisdead]

is the vac connection for after the throttle plate, the one thats at the front of the throttle body nearest the fuel rail? i've currently got mine connected off the brake servo line (which is the same that goes to the FPR & ECU)

[hayesey]

yeah any that connect up underneath the throttle plate is fine.  So the brake servo pipe is fine

[grungeisdead]

sweet, cheers Paul!

[Winston]

Is having no dump valve really that bad for your turbo?

Dump valves are frowned upon on the Renault turbo owners club so ive never bothered, plus I hate the sound of a dump valve!

[N1CKY]

I'm not an expert on turbos but I'm fairly sure cars that come from factory with a turbo have a wastegate to dump unused air. I presume your talking about a renault 5 turbo ? Probably people on that forum think its far to boy racer like to use a dump valve because of the r5 turbo chav history? And they have no use for a dump valve because they dump through a wastegate ? Just my take on the idea.

OT: engine is in now and tidying all the wiring up so it should be back on the road in the new year. I think I want to buy a samco hose kit anyone know where I can buy one ? And what is a sensible level of boost for everyday driving ? I use a turbo valve to ajust boost. So if a kid sits up my arse on the bypass I give that a turn and show them how slow there saxo is

[hayesey]

you seem to be getting wastegates and dump valves mixed up.  They are totally different things and do different jobs.  

Wastegate is to control maximum boost, it allows exhaust gases to bypass the turbine wheel at a set boost pressure.  It's controlled by the wastegate actuator which on older cars is nothing more than a diaphragm and a spring, the strength of the spring and the preload you set it to by adjusting the rod length control the pressure the wastegate opens at.  On more modern cars it is ECU controlled using an electronic valve which opens the wastegate when the ECU sees fit.

A dump valve goes on the boost pipes after the compressor of the turbo.  It is there to stop boost pressure spikes when you lift off the throttle and the turbo is still spinning.  It does two things, one is to stop the compressor from stalling in gear changes so you are on boost quicker when you floor the throttle again as the compressor can keep spinning.  The other is to protect the compressor wheel from boost surges that happen in the high pressure side when you close the throttle suddenly.  This can fatally damage the turbo.  Generally speaking, if the manufacturer of the car the turbo you are using came off saw fit to use one then you should too or your turbo might not last very long.  It can and has wrecked K03 turbos.  If you don't like the noise then simply fit a re-circulating valve which dumps the air back into the low pressure side of the turbo instead of to air, even my volvo TDI engine has one of these, most standard turbo engines tend to.  

[Yoof]

You'll find on a few older LPT (low pressure turbo) applications, that sometimes a dump valve isn't fitted at all. Usually these setups made 7psi, and the negative impact of not having one isn't so dangerous at this level of boost.

However, running a healthy amount of boost, and for the sake of £20-£50 you'd be a fool not to.

[N1CKY]

Thanks for that! Made alot of things more clear

[AlexG40]

you seem to be getting wastegates and dump valves mixed up.  They are totally different things and do different jobs.  

Wastegate is to control maximum boost, it allows exhaust gases to bypass the turbine wheel at a set boost pressure.  It's controlled by the wastegate actuator which on older cars is nothing more than a diaphragm and a spring, the strength of the spring and the preload you set it to by adjusting the rod length control the pressure the wastegate opens at.  On more modern cars it is ECU controlled using an electronic valve which opens the wastegate when the ECU sees fit.

A dump valve goes on the boost pipes after the compressor of the turbo.  It is there to stop boost pressure spikes when you lift off the throttle and the turbo is still spinning.  It does two things, one is to stop the compressor from stalling in gear changes so you are on boost quicker when you floor the throttle again as the compressor can keep spinning.  The other is to protect the compressor wheel from boost surges that happen in the high pressure side when you close the throttle suddenly.  This can fatally damage the turbo.  Generally speaking, if the manufacturer of the car the turbo you are using came off saw fit to use one then you should too or your turbo might not last very long.  It can and has wrecked K03 turbos.  If you don't like the noise then simply fit a re-circulating valve which dumps the air back into the low pressure side of the turbo instead of to air, even my volvo TDI engine has one of these, most standard turbo engines tend to.  

If you haven't already, this should be a FAQ.

[youngprodigys]

i have the chatter - its caused mainly by the location of the dump valve. im moving mine to just after the turbo so the air escapes before it gets back to the blades. currently sits halfway up the pipe from the intercooler.