Why do we have a Throttle body?

[nick112207]

Maybe i'm confused and this isnt the same throttle body that i'm used to, but why does the Sky redline have one? i thought the nature of Direct injection means no throttle body. We dont have a space where the air and fuel mix together before they are introduced into the cylinder. i see lots of people doing it. what does it do on this motor?

[shabby]

You need a throttle body, not sure what exactly you're thinking of.

[fr0stb1t3]

In combination with the ECM reducing fuel flow it closes and reduces airflow. The direct injection only handles gas, you have to have control of air too.

[nick112207]

ok then yeah it is different from what i'm thinking. like i said the throttle bodies i'm used to are what they use in atomizing the fuel in the air. in essence how they mix the air and fuel before it goes into the cylinder. but i guess how you are explaining on these cars they are just the air intake regulator (in a sense)

[fr0stb1t3]

Originally Posted by nick112207

ok then yeah it is different from what i'm thinking. like i said the throttle bodies i'm used to are what they use in atomizing the fuel in the air. in essence how they mix the air and fuel before it goes into the cylinder. but i guess how you are explaining on these cars they are just the air intake regulator (in a sense)

But don't quote me on that, I may very well be wrong.

[nick112207]

oh ok. i ask because i saw people doing upgrades and there are people putting on bigger throttle bodies. wasnt sure if it actually had a proven effect that was worth it or what

[fr0stb1t3]

Originally Posted by nick112207

oh ok. i ask because i saw people doing upgrades and there are people putting on bigger throttle bodies. wasnt sure if it actually had a proven effect that was worth it or what

Actually, on ANY fuel injection engine the throttle body controls nothing more than the amount of air entering the engine, the fuel injectors and ECU control the amount of fuel.

The only difference between DI and a standard motor is instead of the fuel being injected into the intake manifold and combining with the air, it is injected (at an extremely high pressure) directly into the cylinder and combined with the air so as to promote a better burn.

Many port their throttle bodies to allow greater airflow and a less restrictive "inlet" into the rest of the motor. By being less restrictive it should also technically lower the temperature of the air entering the engine vs. the stock throttle body due to its lower resistance against the air. This just goes along with most other mods that we currently have: allow the engine to breathe as best as possible.

[nick112207]

alright thanks. just wasnt sure because i saw people with lots of horsepower with the Throttle Body and ones without it

[WishfulThinking]

In theory, they could probably make the engine run without the throttle body, but I think it has emissions side-effects. Combustion chamber pressures and temperatures seem like a funny balancing act to me any more. There have been some interesting engines (read as powerful and/or efficient) that never saw production because of NOx, hydrocarbons, and such.

I remember reading (probably back in the 80's) about a little honda that got great gas mileage, and would actually lowered the ambient NOx in some cities, but it got booted for ... hydrocarbons (I think).

[nick112207]

ok thats what i was thinking. i wasnt sure. i was really just seeing if it was something that is a must to upgrade to get more power or if it was just more of a preferance type of thing

[jus2shy]

The only Direct Injection motors that do not need a throttle plate are diesels, but that's because they are designed to run extremely lean. The new ones have throttle bodies, but their sole purpose is to help optimize the mix of EGR and Fresh air for emissions purposes.

[redhotchillipepper]

Originally Posted by nick112207

Maybe i'm confused and this isnt the same throttle body that i'm used to, but why does the Sky redline have one? i thought the nature of Direct injection means no throttle body. We dont have a space where the air and fuel mix together before they are introduced into the cylinder. i see lots of people doing it. what does it do on this motor?

You are thinking of throttle body fuel injection that was popular on a number of GM products durring the 1980's before the modern engine control modules we have today. Modern cars have multi port fuel injection because it is more efficient than spraying fuel into the throttle body. Instead the fuel is introduced further down line on the intake manifold right before it enters the cylinder on the intake stroke.

[TBlueMax]

The short answer is that GM does not use technology like BMW's "Valvetronic" on either of the Sky's Ecotec engines (2.4 or 2.0 turbo) to eliminate the need for the throttle body.

Read this for details: BMW World - Technology

Perhaps in the future, GM will deploy a similar technology across their engine line-up, but for now, you'll still see a traditional throttle body.


And yes, as previously mentioned, the sole purpose of the throttle body is to regulate the flow of air into the intake manifold. The throttle body does not regulate fuel flow into the engine.