How to spool turbo sooner?

[Aurélien]

With a Motec Mxx ECU is is very EASY (and inexpensive) to measure turbo shaft RPM, a $250.00 sensor kit, an open digital input, and some machine work on the compressor cover.

Also from our testing and experience airflow has an orders of magnitude higher effect on boost threshold than heat, the heat component of a turbine's 'efficiency' is a small percentage of the total. If you have a VVT system get that intake centerline in the 80's during spool areas.

True !

Do you want to say 80° ( cam phasing ) ?

[Holmz]

I heve retarded the timing and it becomes very lethargic as you would expect. It does nothing to promote spool, or power.
Certainly not on any engine I've ever tried anyway.

The less power it is making, the less ability it is going to have to spool any turbocharger. Theory, practice, obvious.

Power helps spool as power can only be generated by a lot of air flow, which means that there is a lot air flow available for spool.
If you retard the ignition and have an A:F that gives a high EGT - then is the turbo speed less at any given fixed RPM than that seen at max power at that speed?
Some graphs would be good to see.

...
My experience is that too rich mixture kills spoolup. So try to be not too rich during spool up. Even stock EVO9 unit has an feature named "lean spool" to help.

So how does lean-spool work?
And why does a rich mixture kill boost?
Does it alter the EGT?

As written, just more exhaust gasses at higher temperature can spoolup faster. Just let me ask: Do you need rotate turbocharger or make some power ? If you use it as an engine for a car, you schould try to achieve the maximum torq at every point at every boost and every throttle position. Some tuners are too lazy to tune partial throttle and are just tuning the max boost area. My idea is set the lowest boost as possible - tune it for the best result and climb higher and higher with the boost.

Karel it is good to tune at every RPM point and boost condition, as that provides good knowledge of the steady-state conditions at all RPMs... But it is not the same as transient response.
You probably need to start with the steady-state response as you are suggesting, but then build upon that to determine the best approach for transient response to get to the steady-state condition that you have proven is optimal.

[Scott@FP]

With a Motec Mxx ECU is is very EASY (and inexpensive) to measure turbo shaft RPM, a $250.00 sensor kit, an open digital input, and some machine work on the compressor cover.

Also from our testing and experience airflow has an orders of magnitude higher effect on boost threshold than heat, the heat component of a turbine's 'efficiency' is a small percentage of the total. If you have a VVT system get that intake centerline in the 80's during spool areas.

True !

Do you want to say 80° ( cam phasing ) ?

Cam centerline, which is either defined as point of max lift or point between a certain lift such as .050" on open and close flanks, in degrees ATDC intake and BTDC exhaust. Normally on fixed systems intake CL will be between 104-114*, advancing picks up low end (and overlap) and retarding top end.

[jasaircraft]

well, in my experience with rally racing subarus, I've felt (havent measured shaft rpms though) improvement of torque and ergo turbo spool up by having near stoich AFR in the spool up zone, of course having reached mbt first... according to severall lab documents even videos on the web you can see that EGTs are lower either rich/leaner from stoich. So I guess evos lean spool up strategy is just to be near stoich in those areas... of course as my load increases I go for the 13s or slightly richer. Dont have any det issues. Also cheked plugs with no det signs... so we are good.