Syvecs S7Plus - Porsche 997 Turbo - Alpha N

Hey,

I have a few questions for you guys regarding tuning this. My original plan was to tune this car via speed density. Of course I overlooked the fact that the factory MAP sensor is before the throttle body and hence can only read 1000mb and up.

Quick car specs:

Garrett G30-770 turbos, GT3 throttle body, ID1300s.

Now in this scenario I have two options and need some advice.

I have a stock base calibration to start from. I have ajusted the global multiplier to account for the larger injectors. I have adjusted the minimum throttle plate open percentage from 3.7% down to 1.5% to bring the idle down from 1300rpm to 800rpm. I have the car idling but that's as far as I've gotten.

Do I tune this Alpha N with the TPS as my load reference on my main fuel table? I haven't tuned this way before. (I do understand that the map compensation table will handle positive boost)

Or, do I install a map sensor post TB and tune speed density.

Romain from Syvecs recommended tuning alpha N as it produces better results in his opinion.

One concern I have is that my ignition table still uses MAP as load reference, and therefore can't see vacuum. How concerning is this as far as timing goes? How do I calibrate timing in the vacuum areas?

One other question. This car is running a larger gt3 throttle body. Does this need to be calibrated into the syvecs software for all of this to work correctly?

I understand there is a lot to unpack here. I am continuing to deep dive into this, but wanted to post here as this car has thrown me a curveball.

Thanks in advance!

- Ryan

Ryan,

Alpha N with boost comp works quite well in terms of air mass calculation over decent range of operation if you have appropriate compensations for baro, IAT and coolant temperature.

One quirk is exhaust manifold pressure doesn't have a constant relationship with intake manifold pressure, so for example if you hit 20 psi at WOT vs. 30 psi, the MAP comp to fueling will account for the intake side change, but not the exhaust side change, and the likely significant increase in exhaust pressure at the higher boost level will impact engine VE, so it will impact result lambda.

In a standard SD model with MAP as the load axis for the VE table, you end up essentially building the impact of exhaust pressure change with boost pressure change into the VE table by altering VE until fueling is on target.

On the plus side, Alpha N tuning makes for great part throttle fueling accuracy since it accounts for the impact throttle angle has on efficiency.

I add an additional dimension to the fuel model by layering what you have with another RPM vs. MAP table where you enter values as needed to tweak the primary table output to account for the impact exhaust pressure is having. I apologize I don't recall if your ECU can do that, but that's something I do with other ECUs.

Mike,

Thanks for the insight and the response.

I think I may go ahead and give Alpha-N a shot for the experience. For a street car do you feel one way nets better overall results than the other? Moving the MAP to the intake plenum is an easy change if it will give me a better final result. I do have pretty small .62ar turbine housings on the g770s so exhaust backpressure will certainly have a decent impact at higher boost levels. Yeah I believe I can add an additional table to account for exhaust pressure so no issue there.

I plan to road tune this car for now. Then ill get on the dyno after internals, and fuel system upgrades over the winter. Any known differences or quirks to how I would road tune a SD setup?

If you can move the MAP sensor to the intake plenum easily, alpha N + boost comp + what I described in an additional table will provide better drivability via more accurate airflow calculation at various part throttle conditions than you can get with an SD tune that doesn't account for throttle position (other than transient enrichment).

Road tuning SD or alpha N is a bit trickier than a MAF setup, since MAF just requires some steady state, some sweeps, and you're going to be in good shape.

Filling out a full VE or fuel on time table for alpha N or SD involves spending time in a lot more engine RPM/load combinations. It can be done. It's just more time consuming. One trick I use for alpha N is setting DBW up to limit to the value I'm currently tuning temporarily, so I just floor the accel pedeal to tune the 30% throttle row, alter DBW limit to the next row value and repeat, etc. It's much easier than trying to hold the accel pedal perfectly at say 40% throttle while driving, even if you are on a dyno.