Individual Throttle Bodies

How do ITBs work? From the picture I’ve seen, there is never an intake duct attached or filter for that matter. Can anyone explain this?

They are simply a throtle body for each intake port on the head. They are used mostly for race aplication. Generaly speaking you would not want these on your car. They require a lot of tunning.

But are thet disigned to work without fresh air or do they just suck up hot air from the engine bay. Would I have to make intake ducting? That’s the part I’m confused about.

You could make an intake manifold that bolts up to the ITBs and then you can run a single intake pipe down to where the stock ones goes…but ITB’s would only be used on a full out race car with some major PnP and tuning.

all the street cars that I have seen with them all use custom hoods were the TB’s acualyhave there own holes in the hood.

Basically there is a throttle body for each cylinder. What this does is drastically reduce the distance the air has to travel to get into the engine. Having a long path promotes swirl, which helps low end power. Having a short path lifts high rpm power, at the expense of the low end.

Since the air only has about 8 inches to travel, it really lifts the top end, but makes the car a bit miserable to drive on a daily basis.

They are pretty popular in the UK, and I know of a few people that have put bodies (ITBs) on their RS2000s, and they say that they have to launch at about 4k rpms… Just to get going. A bit silly for a DD if you ask me.

Having a long path promotes swirl, which helps low end power. Having a short path lifts high rpm power, at the expense of the low end.

Promotes swirl? Swirling, like a tornado, would require air to come out while air swirls around the outside. An intake is more like a siphon, air is just drawn into the intake.

it should probably be better described as turbulance as opposed to a swirl. The turbulance is supposed to help with the atomization of fuel if I remember correctly.

At low speeds this is true, but at higher air speeds it throws the fuel too much and it does something (can’t remember what) so that it’s not as mixed.

You all got the point of what I was saying. I’ve always read it as swirl, so yeah.

Its pricey, but here ya go.

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The Skyline uses them in conjunction with turbocharging and has scored some of the best drivability scores in USCC history over the years.

According to Nismo the individual throtle bodies give you quicker responce. I have never owned a set, but I may be designing a new IM now.

When using individual throttle bodies with stacks:
They do give you a quicker response because there is no filter and the piping is shorter. But at higher RPM you lose HP that would be made up from the single tube intake.

See after the draw/intake cycle the valve closes and isn’t opened till the next draw cycle. Between those cycles the air sits outside of stack, then gets drawn in when the valve opens. Reminder: Laws of physics, “things in motion tend to stay in motion. Things at rest tend to stay at rest.” The cylinder can only pull so much air in that time span.

With an intake:
After the draw/intake cycle on one cylinder another cylinder is drawing in air. So you have a continuous draw of air and air that is in motion tends to stay in motion. So the air being drawn in creates a low pressure and draws in more air. Now that you have the air moving, it is now pushed into the cylinder by the air behind it. You get the idea.

So why the slow response with an intake?
Getting that air flowing takes a little time because a low pressure needs to be built up inside the intake. All the available air gets drawn from each of the other intake leads (after the throttle body). Because you have stacks, you create the low pressure from the beginning because the volume of the stack is smaller then that of an intake.

how about ITB’s with a plenum that runs into a single pipe that runs the same route as the stock intake did…with a filter at the end in the bumper…doing that you should be able to run a MAF system still.

So if what you sayis true ( I can not deny, dont know enough about the subject). Then Nismo used themon the GTR’s because they are under boost at wide open throtle. There for negating the penalties of the ITB. Do I understand this coorect?

The fact that they are individual throttle bodies or single doesn’t make a difference. It’s the volume of the stacks or intake tube that makes the difference. The more volume you have the slower the response but can be beneficial at high RPMs.

If you are boosted, like Nissan then the fact that it is one or more throttle bodies makes no difference. That is because the air is already forced into the engine and is not dependant on how open your throttle is. The pressure is already there at half throttle and wide-open throttle.

If you are looking for acceleration, multiple throttle bodies with short stacks is the way to go because you will have more power on the low end. I would definitely consider this if I were doing autocross. If you want High HP and TQ in the long run, use an intake with as many throttle bodies as you want.

I have talked to a couple of people and they are consistant in the fact that ITB are good for the get up and go. As for for your boosted therory you are not fully correct. You have no presure at idle, so there for it would help the turbo car. It would cause the car to get to full boost from a stand still faster.

As for for your boosted therory you are not fully correct. You have no presure at idle, so there for it would help the turbo car. It would cause the car to get to full boost from a stand still faster.

You are right, I didn’t go into enough detail.

So for a turbocharged car:
At stop you have no pressure, but it has an intake tube. Right? So from the throttle bodies all the way to the air filter, a low pressure would need to be created. So this would fall under the N/A engine rule until the turbo kicks in.

How would it get to full boost faster from a stand still? You would need to get more air into the engine first. Because of the tube, regardless if you use one or four TBs, it would take the same amount of time to spool up.

The only reason ITBs with stacks are faster down low, is because there is a smaller volume of air to be sucked in before creating a low pressure.

hmmm… maybe I am miss understanding NISMO… They said the reason that they used the ITB’s on the Skyline is because it has a better responce time. Fuck it… I’m on meds and to groggy to think strait…

I did a few searches on ITBs and came up with the same thing in different forums. ITBs work great for low end power, but on high end they die off. All of them were talking about how long the stacks should be based on what powerband you want.

Only on the sites selling ITBs did they say they are great for low and high end.