Strap in kid’s, this ones gonna be a long one.
Something I’ve played with for a few years, specifically in the late VZ/VE E38/E67 ecu’s is the ability to edit the Pedal to Throttle mapping correlation.
With the arrival of drive by wire, the accelerator pedal was now physically disconnected from the throttle body, so it was now possible for vehicle manufactures to alter the response & power of the vehicle independent of the drivers “demand” (foot), Which is why DBW cars originally copped a bad wrap because people noticed the lack/loss of “feel” from the pedal in regards to throttle response.
So, why did manufactures go to it? With the integration of more safety orientated or performance enhancements like ABS, traction & launch control it was now possible to alter the pedal response to either restrict throttle opening or give more for the same pedal movement, you can start to understand why they did it.
Also when you think about it at the most basic of levels and like everything in life it always comes down to the Dollars, specifically WARRANTIES. If you can reduce the potential for abuse on the drive line, you stand to save a fortune as a manufacturer on potential faults/repairs.
Anyway, on to the cool stuff. What I’m about to show is a couple of examples of power limiting rather then power adding. The reason for this “limiting” is because the setups are both Supercharged V8’s, so there is sometimes a need to limit the amount of boost the blower creates, i.e over-driven blower.
The first car was a VE E3 Clubsport with a stock LS3 Auto, bar a cat-back exhaust with over 140k km’s on it at the time the Harrop FDFI2300 supercharger went on, with further mods to happen at a later stage, I wanted to allow the owner to get used to the power (his dad & my preference). So no valve spring or fuel system upgrades as yet.
After the blower first went on I started by doing some small load testing at various rpm’s to see what the maximum boost was, I expected it would be well over 10psi since the blower originally came off my own Cam’d 6lt ve ute making that.
Since it still had stock headers & cats it made north of that at around 12.5 even with a larger blower pulley fitted to reduce the boost, which is why I moved on to do some testing with restricting the throttle opening. This is done pretty easily in Efilive by adjusting the pedal to throttle mapping.
What you can see above is the factory calibration & how below the 2500rpm row, the values are lower, I can only assume to smooth any large pedal movements at low rpm. The numbers themselves do not correlate to a 1:1 rate to the throttle blade opening.
In the next 2 pictures you can see that at 2600rpm the Accelerator Pedal is at 100% however the Throttle blade opening is only at 69%. This is achieved by modifying the throttle response map.
As expected with the 6 rib drive setup on this car, as the rpm’s started to climb the boost started to drop off. Luckily because the blower was capable of generating more boost then needed, I could tailor the boost curve how i wanted by simply manipulating the throttle mapping, which is why from 4500rpm I start to allow more throttle opening to maintain boost pressure.
The end result was a 130whp gain for on a complete stock LS3 motor/exhaust combo.
The second car is my own VE Ute which got upgraded to the Harrop FDFI2650 with the LSA drive belt setup, this is a more aggressive combination setup with full exhaust, flex-fuel & bigger motor with a Fore Innovations Twin 450 pump setup. All though it does have an aftermarket converter & trans cooler it still has a stock 6l80e.
It had previously ran 10.5 over the 1/4 with a touch over 600whp on pump fuel in 2015, for now I’ve just been filling it up with E85 because it’s not driven on a daily basis.
Since the ute has the same Operating system as the Clubsport it had the same base throttle map configuration. So below power runs were done after severely restricted throttle opening until 6500rpm to get a baseline.
Further playing in the Pedal response map I eventually got to my desired boost to pedal correlation. While also limiting the response at lower throttle movements to make the car easier to drive, since with the larger 102mm throttle it can be very touchy for traction if your not careful.
Throttle limiting in action
APP = Accelerator Pedal vs ETCTP = Throttle Opening %
Couple more tweaks to Pedal Map with the end result being a nice linear power graph