Technicals of ICEs

**AeonBlaire** · January 31st, 2008 04:30 PM

Technical question:
Ano ba nangyayari pag apak mo ng accelerator pedal?

A. You invoke a mechanism that forces more fuel (and air) into the engine.
A.1 Gradual increase
A.2 Almost instant increase

B. The accelerator pedal is actually hooked to a mechanism that limits the rev of the engine, kasi by my intuition, ICE's tend to increase the rpm even the initial feed of fuel and air is low.

C. The accelerator pedal is actually hooked to a mechanism that limits the maximum amount of fuel and air that can be pumped by the engine.

D. Something else.

**meledson** · January 31st, 2008 04:57 PM

Akala ko In Car Entertainment.

**Dr.Kamiya** · January 31st, 2008 05:34 PM

Before you can have in-car entertainment, you had to have the internal combustion engine. =D

The accelerator more or less synonymous with throttle. Throttle governs the amount of air, and by a function of that fuel that is let into the engine. Yung revs etc. etc. are just a by-product of this.

Case A is more or less correct, pero instead of the amount of air being a function of the fuel you let in, it's the reverse. The amount of fuel is a function of the amount of air you let into the engine. Conversely, C is also correct. Since the accelerator governs the throttle, stepping off the accelerator also closes the throttle, meaning you stop/limit air, and therefore fuel from entering the engine.

Before the days of electronic fuel-injection, the amount of fuel is more or less linearly related to the amount of air, both being fed into the carbuerator. Because of this linear relationship, old carb cars are often run rich for safety, kaya pag dating sa high-altitude environment (i.e. baguio) minsan nalulunod sa gas.

These days, the amount of fuel needed is calculated by the ECU, by sensing the amount of air coming into the engine via a MAF (mass airflow sensor) or MAP (mass air pressure sensor).

Yun lang po! Basta to summarize: at the very basic level, the accelerator controls the amount of AIR coming into the engine, tapos yung ECU or carb mo na ang bahala sa amount of fuel. More air = more power = more revs. Lahat na ng succeeding driving characteristics ng engine madederive mo dito.

**alwayz_yummy** · January 31st, 2008 05:39 PM

yup--kaya di ako sumabat,e...no subz and amps here

ICE on topic = internal combustion engine, isa sa mga major ko to,e..

teka ha.. tanda ko letter A sagot....

**AeonBlaire** · January 31st, 2008 06:49 PM

Thanks.
I meant A and C to be different, so based on Dr. Kamiya's explanation, C is the answer. Now please let me follow-up and expand.

The amount of pressing on the accelerator pedal (how much you press it)

A. Translates to how fast the engine revs to full rev (and increases torque?), so essentially "ICE's tend to increase the rpm even the initial feed of fuel and air is low."

B. Dictates at what rpm (and torque) the engine stays, and stays that way.
B.1 The carburetor/ECU regulates (up and down cycle) air/fuel intake so that the engine stays at that rpm (and torque).

C. Both actually, translates to how fast the engine revs (and increase torque) to the limit dictated, and the air/fuel intake is regulated (up and down cycle) so that the engine stays at that rpm (and torque).
C.1 Only ECUs can do this.
C.2 Only carburetors can do this.
C.3 Both ECUs and carburetors can do this.

Kasi when the clutch is engaged the tendency is to eventually stop the revolution, due to friction. Thats why sometimes you need to rev the engine first before engaging the clutch, so that the engine has a headstart against the incoming friction, tama ba?

Arrgh when pondering on this topic, it tends to be complicated, kasi may mga issues na lalabas, kaya ung modern vehicles ay dapat talaga ECU.

**4JGtootsie** · January 31st, 2008 09:14 PM

ICE is the engine as a whole. I just get the impression the ICE is just a part of an engine. The fuel system, air induction and advance mechanism (vacuum, electronics,etc) facilitate the increase in engine speed.

The engine should maintain speed (atleast minimum capacity) even if the clutch starts to engage. The sudden load to the engine is obsorbed/desipated by the flywheel, pressure plate and torque converter.

In diesels which is also an internal combustion engine, the pistons, cylinder and turbo acts as an air pump. The increase in fuel injected at an ideal compression ratio will increase engine speed therefore increasing air pumping capabilities.

**niky** · February 1st, 2008 02:24 PM

The classic accelerator pedal is sometimes called the throttle... for good reason. All it does is control the amount of air entering the engine.

The throttle does not directly dictate what rpms the engine runs at. It just lets in more air. The fuel system, whether computer-controlled injection or regular old carburated fuel delivery, reacts by pouring in more fuel. Certainly, when you floor the throttle, the engine will rev faster, but both medium and full throttle will make it rev at the same rate. Maximum engine acceleration (how quickly it reaches full revs) is more a factor of internal friction and inertia than the throttle itself. In other words, the engine only revs faster at higher throttle openings because more air and more fuel give it more power to move its own weight.

The more air-fuel mixture in the engine, the more power it makes. If there is absolutely no load on the engine (let's say it's perfectly frictionless), even with just a tiny bit of air-fuel mixture, it'll rev to redline (a limit imposed by how much fuel the carbs can flow (carburated) or by the computer cutting spark and/or fuel (Electronic) to prevent the engine from blowing up.)

When you put load on the engine, it'll rev slower, so you need to add more air and fuel to keep the revs up. This is what happens when you engage the clutch.

**kinyo** · February 1st, 2008 03:52 PM

Why can't a typical ICE continue to rotate at less than 300 rpm, when it can be started with just a few rpm?

**AeonBlaire** · February 1st, 2008 07:54 PM

Ok. Based on Mr. niky's explanation, the answer is A.

If thats the case, rotational speed is constant behavior and can be ignored. The real equation is that,

How much you press the accelerator pedal can be translated to how much torque/power the engine is producing (na nasa summary din ni Dr. Kamiya), albeit the application of force is pulsing, depending on load.

*kinyo
Because the continuation of the engine's stroke cycles and the amount of fuel/air is partially dependent on rotational momentum, tama ba mga bro?

**4JGtootsie** · February 1st, 2008 08:01 PM

Why can't a typical ICE continue to rotate at less than 300 rpm, when it can be started with just a few rpm?

I think its a combination of rate of compression, friction resistance, inertia, weight and even gravity to reach all cycles/strokes> intake, compression, power and exhaust. The cranshaft will need momentum.

Cranking takes a few rpm(powerfull turns) but it has to overcome all the combinations stated above. Once a four cylinder engine starts to fire 1 piston adds power to the cranshaft every 180 degree turn of the crankshaft or 720 degrees for a full cycle of all 4 strokes or all 4 pistons fired. When i was still in school we were taught the importance of running mates, firing order, 4 strokes and what the piston position based on its stroke. Nakakalito sa start but you really have to learn it especially when you start adjusting valve clearances.