gareth142185

hi i have a 54 plate wrx with a full de-cat system, a hks induction kit, and a hks blow-off valve i have blocked the blow-off valve off as someone told me that i would get the wastegate chatter if i did? but when i have done this all i get know is a flutter out of the induction kit?? can anyone help me 2 get this sound?

thnx.

GreenDream

You won't get wastegate chatter unless you are running an external wastegate. The sound you are talking about is flow reversal. The charge air has nowhere to go so backs up against the blades of the impellor (think of the sound a fan makes when you blow on it). It's potentially very damaging to the turbo as not only can it break off blade tips, but the shock loads can cause problems with the bearings. I'd think twice before running the car much longer without the dump valve.

T5OLF

iTrader: (4)

The TD range will run fine with no DV many people myself inc run with no DV.

The rookie

iTrader: (1)

Its called compressor stall and it happens when the pressure ratio across the compressor is two high for the flow rate, and its just like an airplane wing stalling, its not good for turbo's but the MHI TD range seem to cope with it OK, to get the noise you need full boost and back of SHARPLY!

Simon

GreenDream

No turbo copes well with compressor stall. Granted the Mitsi range of turbo's are relatively hardy, but you only have to look at bearing damage after compressor shock loads to know that it drastically reduces turbo life.

340BHP-WRX

iTrader: (6)

All the TD range of turbos can cope fine with compressor stall. I'm running an Andy Forrest 20G at 1.55 bar with no dump valve and Andy said he would still honour the warranty under these conditions.

This question has been asked many times on here,basically if you are running any TD range of turbos it'll be fine with no dump valve. VF series turbos are weak in comparison so shouldn't be run without a D/V.

I'm not sure about other turbos though

Mrchips

iTrader: (7)

Yeah TD are a lot tougher because of the conditions they get put through, as they were many for the UK spec.

This is what I have been told anyway.

GreenDream

I was one of the technicians for a very well turbocharger manufacturers for a number of years, and the number of turbos we had back under warranty claims after the end user disregarded their dumpvalves was immense.

When the throttle is shut the shock loads put stress on the impellor which as a result puts immense forces on the thrust bearing. Turbo's are allowed a small amount of side to side play but there should be zero end float, and flow reversal causes this. A 360 thrust bearing can put the problem off for a while longer, but it is innevitable - it will happen. Yes some turbo are more resiliant to abuse than others, but they are all made of the same materials and all wear at the same rate. Manufacturers put a lot of time and money into designing engines, and dumpvalves are there for a reason. Be careful too, as some turbo suppliers will actually void a warranty if the dumpvalve has been blanked off.

I helped design and build turbo for Formula Palmer Audi, Skoda WRC, Mountune and many others and they all still used recirculating valves. higher than standard boost pressures will exacerbate the problem and these guys go into a lot of detail to make sure turbocharger life and efficiency is mantained.

gareth142185

thanks 4 all your replys. it sounds better if i put the d/v back on coz i dont want 2 b buying another turbo just yet

GreenDream

Sorry Gareth, wasn't trying to scare you, but i just wanted to make people aware of the risks that "can" be involved. Doesn't mean it will happen, but it is known.

The rookie

iTrader: (1)

I'm with GD, who I will assume worked for Honeywell (aka Garret) as most other manufacturers (like MHI) use 360 thrusts as standard!

Simon