Adjusting wastegate spring for less boost

[foxdie]

Hi all,

I'm not sure if this has been done, has anyone adjusted / replaced the wastegate spring on the 6A13TT?

I'd like to try and lower the stock wastegate pressure to somewhere around 0.1 bar (1.5 PSI), yes I'm aware it'll make the car flat as a fart, that's exactly what I'm going for as I'm looking at this for a valet mode / anti-joyride feature.

Naturally I will still be controlling boost via ECU control (or hopefully soon an EBC) for those 1.25 bar (18 PSI) TLGP's but the plan is to lock the car down via a hidden keyswitch that sets the WGDC to 0%

[Wodjno]

Wtf ?????

[foxdie]

Wtf ?????

Yeah I know I know, I'm an oddball

[Wodjno]

No.. Not Oddball. If u are, i am also Just something i was discussing as an idea earlier with a club member. But for a totally different reason !! Freeeeeaky

[foxdie]

I've been thinking about this for a long time, I tried detuning my cars boost as low as it'd go for some decent around-town economy, but ultimately it bottoms out at the 0.5 bar wastegate pressure.

Ps. I'm psychic...

[Wodjno]

My idea was for Fuel saving while pottering around. Stopping the little tubs from spooling so quickly low down and then the ECU dumping in loadsa fuel. Decreasing the spring pressure to around 1-2 psi and along with wastegate creep would keep manifold pressure negative. (Hopefully)

[Kenneth]

Before you try this, I would disconnect the wastegate and wedge it open.

Fluids flow the path of least resistance, as soon as the resistance in the wastegate opening (and lets face it, it isn't THAT big) results in flow across the turbine, you will get turbo spooling.

The question is at what point/RPM this happens and if having 'very low' spring pressure will make much difference in the boost level at higher RPMs.

[psbarham]

the other thing to remember is that a weaker spring will result in less seating pressure for the wastegate,

A mate single turbo'd his rx7 and for wet weather use he fitted a 0.3 bar wastegate so it would be usable but it resulted in not being able to make constant boost once the tub got spooling properly.

[foxdie]

Interesting, very valid points, might be worth investigating alternative methods of bleeding boost then.

[Kenneth]

I would be very interested in seeing fuel economy results with the wastegate open or at very low wastegate spring pressure.

I am not convinced that it will improve fuel economy over a well trained right foot as even below positive pressure the turbo is spinning giving possible VE gains and causing potential fuel use if you are a bit too heavy footed. By the time you get to boost, chances are that you have done the damage in fuel use already.

[Wodjno]

Is there anyway that the system could be cheated? By making the wastegate see poisitive pressure below a certain throttle position.

[Wodjno]

Is there anyway that the system could be cheated? By making the wastegate see poisitive pressure below a certain throttle position.

Suppose it would need some kind of lekky pump compressor ? That could be turned of by a switch above a specific throttle position?

[foxdie]

Stop reading my mind Glenn!

[scott.mohekey]

Replace the mechanical solenoids with electrical ones?

[Kenneth]

a vacuum canister which is essentially a reversed wastegate actuator. A correctly sized one would, when activated have enough pull to open the wastegate against the standard actuator.

Would be and interesting job to hook up and control though.

[Wodjno]

Suppose it would need some kind of lekky pump compressor ? That could be turned of by a switch above a specific throttle position?

What about back pressure in the exhaust, say just before the cat converter(for those who have them fitted) A pressure line to fool the wastegate into thinking there is positive pressure in the manifold.Thus opening the wastegate. Above a certain TP it can be cut off via a valve triggered by TP?

[foxdie]

I started looking at 12V compressors like this; http://shop.wiltec.info/product_info...-08ADC-KB.html

Stupidly expensive for a theory.

[Kenneth]

Isn't likely to be sufficient exhaust back pressure to do that, at least not there. If you are flowing enough for that sort of pressure, chances are you are creating sufficient boost.

[Wodjno]

I started looking at 12V compressors like this; http://shop.wiltec.info/product_info...-08ADC-KB.html

Stupidly expensive for a theory.

Yeah we need free pressure

[Wodjno]

Isn't likely to be sufficient exhaust back pressure to do that, at least not there. If you are flowing enough for that sort of pressure, chances are you are creating sufficient boost.

I did wonder what sort of pressure would be there on light throttle.. I suppose it all comes down to the restrictiveness of the exhaust also. So where else can we get some free postive pressure ?

Spare tyre in the wheel well