Tom F&L GoR
Enthusiast
Re: Throttle-Body Controversy! \"What\'s Best\"
Question & Comments
Air velocity was important for carburetors to get the right signal that would meter the proper amount of fuel; too big a throttle bore and not enough fuel was sucked in. Throttle response suffered because the mixture would run lean and even if you richen the jet, the air speed wasn't as high and the intake charge was not as well mixed.
In a fuel injected engine, the fuel is well vaporized for you by the injector nozzle; not only that, the ECU has already figured out how much fuel you need. Airspeed through the throttle body doesn't matter. And regardless of throttle size, the manifold air pressure (MAP) or mass air flow sensor signal is what matters, and for a given load, they won't change.
You might get too large a throttle body so that the throttle position sensor seems to tell the ECU that it's not open very far, while it is actually flowing more air, resulting in a somewhat false signal, but I would expect the ECU learning to eventually factor this out.
So unless the throttle body is the restriction, there won't be a power gain, but I don't see how it can be a torque loss (unless the TPS signal is way off.) Help me out to understand this?
Question & Comments
Air velocity was important for carburetors to get the right signal that would meter the proper amount of fuel; too big a throttle bore and not enough fuel was sucked in. Throttle response suffered because the mixture would run lean and even if you richen the jet, the air speed wasn't as high and the intake charge was not as well mixed.
In a fuel injected engine, the fuel is well vaporized for you by the injector nozzle; not only that, the ECU has already figured out how much fuel you need. Airspeed through the throttle body doesn't matter. And regardless of throttle size, the manifold air pressure (MAP) or mass air flow sensor signal is what matters, and for a given load, they won't change.
You might get too large a throttle body so that the throttle position sensor seems to tell the ECU that it's not open very far, while it is actually flowing more air, resulting in a somewhat false signal, but I would expect the ECU learning to eventually factor this out.
So unless the throttle body is the restriction, there won't be a power gain, but I don't see how it can be a torque loss (unless the TPS signal is way off.) Help me out to understand this?
