Hi !
I have some theorical questions about airflow. I'll be glad to hear for enlightened opinions !
The question : Noise attenuation apart, does the piping going to the airbox play a role on power/torque/efficiency ?
Context : Engine is 1.6L vvti from a 2003 Toyota Corolla (3zz-fe engine). It is already fitted with 1.8L (1zz-fe engine) Intake manifold, throttle body, and injectors (see my presentation)
I like to have an economical car, but I really appreciate small smiple power mods. The last one being taking out the snorkel/piping going to the airbox.
Taking out this snorkel made me think about why it should make the car more powerful and more importantly, why it shouldn't change fuel economy.
Correctly if I'm wrong :
1) Less restriction equals more air equals more power, especially at high revs.
Piping connecting to the airbox is narrowing down to 40mm (see picture), which seems the same diameter than the stock throttle body (3zz throttle body plate is ~42mm). I guess it shouldn't be a restriction in that case.
In comparison, the 1zz throttle body I have installed is ~55mm at the plate. Cross sectionnal area is almost twice at 13,5cm² vs 23,5cm². In this case, the 40mm pipe seems to be a huge restriction, right ?
2) I was concerned about fuel economy, as keeping it low and reliable is my main goal, the rest is just for fun !
I know that air velocity is important in an engine, and I read that longer piping may give an advantage in terms of low end torque, but as we are talking about fuel enonomy, we are definitely talking about very low to moderate throttle input. In this condition, the main restriction would by far be the throttle plate angle ?
-> So let's imagine an hypothetical situation where we are cruising on the highway at constant speed. Our car needs 20hp to overcome friction losses and air resistance. Throttle is open at an arbitrary 20° angle to give the engine sufficient airflow for this power.
I If this piping was really doing an amazing job for airflow, whitout it I now wouldn't have enough air to produce 20HP. No problem, I press more on the throttle to give the engine a little more air.
On the other hand, if the piping was restrictive, even at partial throttle. I now have too much air, too much power, so I let off the pedal to keep a steady speed.
Am I forgetting something that would make this situation unrealistic ?
3) Finally, this problem is more or less the same than "stock airbox vs CAI/SRI" . I read a lot on the topic, but often people doing this kind of mod don't care about their mileage. But I don't see why a CAI/SRI would alter fuel use at partial throttle ? (assuming that temperature variation between stock and CAI/SRI is negligible).
What are your thoughts on this matter ?