Tag Archives: ITB

Thou Shall Not Covet…..

26 Jan


Toda’s ITB Equipped Honda 3.2 liter V6


Adam’s Project Z33: Update – NISMO Garage Door Moulding

9 May

Haven’t done an update on my car in a bit, so figured it was time. Last weekend I actually got to drive the car with the ITB’s! Wasn’t a long drive, only about 20 minutes, but it felt good to take her out for a spin after laying dormant the past 5 months. More to come soon as we get the tuning done, etc. Fingers crossed it nets a gain over what I had previously!

Since Shaun’s car left today and we’ve got more room now, I was able to do some minor work to my car. We’ve actually been doing quite a bit to the car lately, trying to get the ITB setup all done. In preparation we swapped over to the ’07 + radiator support, since it has dual inlets (one per side) to help feed them some cooler air. I also ditched the UTEC in favor of a Haltech. At some point I’ll get to install the cool Racepak dash cluster, but I have a feeling that’s still a few months off right now.

I’ll say this much – I must be a total NISMO whore, because I actually forked over the $ to buy the NISMO lower “guard” for my front bumper. It’s basically a long, $60 piece of what is effectively garage door moulding, that you can buy at any hardware store. Except this comes in a NISMO bag with some sort of certificate of authenticity. I guess that’s so you can flash it to people to prove you didn’t go the Home Depot route. Kwame ordered one up for his car and said I should get one for myself – so I did, without realizing I could have done this way cheaper, but so it goes. I really have no practical purpose for it. As low as my car is, this front bumper seems a touch longer than others, so I just don’t have the issues over speed bumps that I did before. I just wanted some black contrast at the bottom of the bumper. I had a lip on the car this time last year that took me all day to mold into shape, and it looked awesome. But it was too damn low and I kept having to nurse it around. This piece is not nearly as tall, and it’s flexible, so it should do well.

I cannot wait for this phase of things to be done so I can enjoy her again!

Toda Racing NSX Engine

29 Mar

Not sure of the exact specs, (I think this is their GT300 engine kit) but it looks sexy !

How I Spent my Friday Night….

30 Jan

Time to get these things on the car and operational!  The journey begins.  Lots of work still to be done with various aspects of the kit, but I’m looking forward to firing it up. 

My 350Z with ITB's!!!

My 350Z with ITB's!!!

Toda Racing Spec ’02 Honda NSX for sale at Global Auto

30 Jan

Nothing but the hotness…

NA is Dead? Pt. II

7 Sep

In the last segment we looked at the very basics of an Individual Throttle Body setup, and the very basics by which it works.  This time around I wanted to go a bit more in depth and explore the different types of setups out there.  I’m also going to attempt to give some insight into various technical features of each type as well.

Trumpet type – this is the image that most people have in their head when they thing of an Individual Throttle Body.  Each airhorn, or trumpet is responsible for feeding an individual cylinder.   However simple it may seem, the design of the trumpet itself has a tremendous amount to do with the performance that can be extracted from it.  First, there is the length of the trumpet.   Just like in a sealed intake manifold, the shorter the runner, the more top end power the engine will have, and the longer the runner, the more low and midrange power it will have.  Altering the design of the bell also has alot to do with the overall powerband as well.  These are the most simple type out there, as they use a simple butterfly valve to ingest air to the combustion chamber.  There are several key elements in the design one chooses for their trumpet style.  These will vary from engine to engine based on many factors, such as combustion chamber design, valve placement and diameter, cam lobe profile, etc.  The proper taper of the trumpet will give you the best of all worlds – sufficient low speed volume so the car doesn’t become peaky, but providing significant velocity when the valve is fully opened, to mid and top end power.   The trumpet design as mentioned, is highly interdependant on many other aspects of the engine.  If anyone is interested in some helpful math formulas, let me know and I’d be happy to post them. 

The above pictures shows a typical trumpet style ITB setup on a modern V6 engine.  Note the taper of the trumpet that continues to the intake runner itself, providing a balance of low, mid and top end performance.

Slider ITB – Slider style throttle bodies were born out of logical belief that with the traditional butterfly valve style, you are giving up prescious air volume and velocity by having a shaft in the center of the bore.  In a slider ITB, there is no throttle shaft.  Instead, there is a door that slides open and closed to ingest air.  As you can imagine, the packaging requirements tend to make these more space hungry and more expensive to produce.  These are also said to give non linear throttle response, making them difficult to drive at lower speeds, and difficult to maintain a steady state speed.

Typical Slider Type

Typical Slider Type

Roller Style – the roller style throttle body is the third type of individual setup out there.  In this type, you have two barrels, one that rotates inside another.  These are essentially combining the linear throttle progression of a traditional butterfly setup, with the pure flow of the slider type.  As you can imagine, these are the post costly to produce, and leave the least margin for error, as you no longer have the ability to alter runner length, taper,  etc for a given application.  Each component has to be machined on it’s own, meaning it’s got to be perfect out of the gate.  The inner roller uses ball bearings for smooth and linear actuation. 

Get your math right, your patience high, and a bunch of buddies to chip in on a CNC machine, and the roller is clearly the way to go from a packaging and performance standpoint.  But there really is no margin for error.

Here is a very neat video showing a roller throttle body in action on an STi

So, now we’ve seen the different styles of ITB’s out there.  In the next segment, we’ll get a bit more into design considerations of the most popular version, the butterfly style.  This will include injector placement, trumpet location, and what all is needed to actually make one of these setups run a car.

Stay tuned!!!

NA is Dead?

19 Aug

All too often on the web, you see guys talking about making big hp on cars through forced induction. Whether it’s a supercharger, turbo, twin charged, etc., there is always someone pushing the envelope here.  But what about good old fashioned NA power?  No boost, no having to inject various concoctions of combustible chemicals to be able to crank the timing – just plain ordinary air? I think it often gets left by the wayside.

I wanted to start a multipiece series on NA tuning, with particular emphasis on what to many people is the pinnacle of an NA setup – the Individual Throttle Body, or in web language, ITB. Let’s just get a basic understanding of what an ITB is and how it works.

As the name implies an Indivdual Throttle Body (ITB) means each cylinder has it’s own dedicated path for the air to reach the combustion chamber.  The bodies are linked together so that they open and close together, thus allowing the engine to ingest the air required for the combustion process.  There are several benefits that an ITB setup can have over a single throttle body.  First and foremost is cylinder balance.  With a single throttle body, you have little to no control over how much air is ingested into the the combustion chamber for each cylinder.  As a result, you end up with air reaching the combustion chambers in varying amounts, at various speeds, which can leave you with cylinders producing different power levels.  The amount this differs of course varies by the application.  With ITB’s there is no sharing of air.  Each cylinder is afforded unlimited air, and through tuning, the user can ensure that each cylinder is ingesting the exact same volume per air, at the exact same velocity. The second benefit is throttle response. With each cylinder now able to ingest it’s own dedicated stream of air, the combustion process starts quicker, and the engine responds faster to throttle inputs.  Furthermore, because you now have individual paths of air vs a large single path, the volume of air and the velocity that can be ingested into the engine as the throttle plate opens is often more than a single throttle body setup allows.  We’ll go into more detail on this last point in a future installment, as well as determining the right manifold design for a particular application, all with real world testing, graphs, videos and dynos!

As best I can tell, the first production car to use both ITB’s and fuel injection was the very rare BMW M1. This car was manufactured from 1978 to 1981, and used a combination of ITB’s and a mechanical fuel injection system developed by Kugelfischer and Bosch.  BMW still uses ITB’s today on their M series engines.


In the next installment, we’ll look more in depth into various ITB setups as well as design differences, etc. In the meantime, take a look and listen at this clip from Option Video from Japan of a tuned Acura with ITB’s.  If this doesn’t make you fall in love with an automobile, it’s pretty safe to assume you have no soul!