Being that I finally got my car to idle nice and stable without any surging, I am about to take some next steps and try to let her breath a bit more. I have a ported 87mm throttle body on it now, BUT it has been hashed out to death on my forums that the ported throttle body at no spot in its entire length is any bigger than the stock 80mm since it uses the stock butterfly and therefore doesn't flow anymore than stock. I am looking to install a true 90mm throttle body.
Through looking at various tune samples, it looks as though the stock throttle body airflow table for base Whipple tunes is already raised up, presumably due to the huge airpump added just aft of the throttle body which is increasing the effective flow rate of the throttle body. Example at 0.3 volts on the stock manifold/throttle body without a twin screw behind it, the tune says 126 lbs/hr flow for stock, Whipple says 153lbs/hr. Can anyone else confirm this?
This creates a dilemma for me on a base line point to start to increase the throttle body airflow. API, the maker of my throttle body, claims the 90mm TB flows 819CFM at peak, "178CFM more than stock" implying stock is 641CFM. Using STP to convert, 641 / 0.75 = 8,547 lbs/hr. Stock throttle body table is pretty close at 8,412 lbs/hr at peak, seems like their data is lining up.
Overall their 90mm throttle body should flow about 25-27% more at peak, and I am guessing it is a non-linear curve to the flow increase getting closer to 0 volts.
What do you guys think? Take a stab at increasing the Whipple values or maybe just install and see how it acts? Also, I noticed a distinct relationship between the Throttle Body Airflow, Airflow>Electronic Throttle>Desired Throttle both the Large Range and Small Range. ALL three of these tables in a stock NGC3 CAN tune are 100% inverses of each other. Now I assume this should be kept this way, but looking a little deeper and thinking about this, not sure they HAVE to be. Looks like the desired throttle is pedal voltage. Just because I put the pedal to 0.70 volts doesn't mean I want the throttle body to give me 544 lbs/hr of flow, even though at 0.70 volts on the TPS means that's what the throttle body would flow. Maybe at 0.70 volts with my right foot I want just slightly more than idle power, something like 200 lbs/hr, and so should scale the desired throttle this way.
Confusing I know...just thinking out loud.