So I've never been real happy with the spool-up of my car. Lazy to spool,.. and it doesn't set you back into the seat until 3,500 rpm.

Stock turbos,..... (Do88's, GT2 coolers, IPD 74mm plenum, catless exhaust,.... etc)

So I decide to look at the waste gate duty-cycle,.. and the HIGHEST they EVER get is 70%.

In my previous platform we'd have them clamped down at 100% as long as we could without causing a spike.

Should I have my tuner fix this?

Or is there a reason it's this way?

Datazap log.

http://datazap.me/u/duckstu/log-1467...ata=1-10-22-23

 

From AfterSales Training manual:

Control By The Motronic Control Unit ME 7.8.1
Optimum adjustment angles are set by way of functions in
the engine control unit depending on the engine operating
point, so that the target engine torque is reached as
quickly as possible. The optimum vane positions for
maximum efficiency were determined for the complete
engine map as part of extensive application work. The
goal was above all to optimize the response behavior
particularly for dynamic acceleration. Variable turbine
geometry allows a full torque characteristic to be achieved
even at low engine speeds and also provides a wide power
spectrum in the nominal output range.

Diagnosis Of Electric Boost Pressure Adjuster
The electric boost pressure adjuster features an integrated
diagnostic function which transmits a fault to the
DME control unit by way of a corresponding pulse/duty
ratio.
• The nominal mechanical adjustment range or control
range ( R ) extends from 20 % (vanes open) to 80 %
(vanes closed).
• The pulse/duty ratio is approx. 40 % when the ignition is
switched on.
• The pulse/duty ratios 0 % to 19 % and 81 % to 100 %
are special pulse/ duty ratios for diagnostic routines ( D
) and for teaching the adjusting device.

Ie 100% DC was way out of OEM intented operating area. I've played with that a bit, and IMO there is nothing to be gained when going over 80-85% when building spool, except troubles. Spiking is way too easy to achieve.
OTH 70% is at conservative side.

EDIT: When intrepreting OEM datalog DCs, one should read my above text like this: Ie 0% -vanes fully open, boosting at idle- or 100% -vanes fully closed, no boost whatsoever- DC was way out of OEM intented operating area. I've played with that a bit, and IMO there is nothing to be gained when going over 20-25% when building spool, except troubles. Spiking is way too easy to achieve.
OTH 30% is at conservative side.
Reason is that I have a standalone controller, where DCs are reversed from OEM.

 

That's what I thought.

At 2,500 I whack the throttle open 100%,.. and the waste-gate duty-cycle goes from 35% to 50%,.... then slooooowly builds to 70% max.

Of course this means that it takes multiple seconds to build boost from that rpm,.. and even when I hit the throttle from above 4,000 rpm,.. it still takes just over a full second.

This is dreadfully slow by modern standards. When an engine is 1,000+ rpm PAST it's spool-threshold,.. the turbo response should be almost instant. My last car would go from 0 psi to 22 psi in perhaps 1/3 of a second from that rpm.

I was wondering if Porsche did this intentionally,... so as to evoke the lag then hit feel of the early doctor-killer 930 cars? And if it can be fixed so that the car has response like modern cars?

 

Just an FYI, the variable is named in such a way to be roughly related to what the average tuner and car guy will understand, but the boost control on this car is 100% unrelated to any car with a standard pintle valve wastegate of any configuration. The value is related to the angle of attack of the VTG vanes relative to the turbine wheel. I don't think it ever rotates the ring until the vanes are 90 deg incident to the exhaust flow. To do so would add a large restriction with the gas having to make a 90 deg turn before even impacting the turbine inducer.

 

^^^ Good note here, reminded me that in my (standalone) controller's UI 70% DC means that vanes are 70% open and on OEM logs 70% DC means that vanes are 30% open...I had forgot that and thus wrote earlier an bit confusing way.
So Duckstu's "and the waste-gate duty-cycle goes from 35% to 50%,.... then slooooowly builds to 70% max" means that vanes initially open, directing flow to turbine blades thus spooling and then gradually close, directing flow past turbine , thus controlling the boost.

 

Thanks A418 and Pete

So,.. what I;'m hearing is that there is not traditional swing-door waste-gate,.. and boost control is done solely by the vanes?

I had wanted to compare my logs to those others had done,.. but of the 3-4 I was able to find,.. none had logged their WDC's.

Is what I have the best that can be achieved?

I'm not wanting to expend huge dollars in a radical engine displacement increase,.. and so I just want o verify this is as good as it can be before switching platforms.