Non K-Series Build: Individual Throttle Bodies

[Mike@ML-Works]

Well guys, I thought I'd keep a blog, journal, thread or source of information about individual throttle bodies (ITB's). This thread will be a journey from the idea, through the development, concepts, fabrication, and tuning - a long journey at that. The intent of this thread is to not only showcase my work, but I hope for it to be an insight into what all goes into developing intakes, many of the same principles transcend to single throttle body designs as well. So lets get started shall we!

ITB's have been a fascinating part throughout racing, and even on some of todays cars. F1 has used ITB's for decades. They are a great source of throttle response, however they do have their drawbacks. For one, they are difficult to tune. Secondly, they often result in peaky motors; meaning they are good for a certain part of the power band and sacrifice everywhere else. This difficulty results from designing the optimum runner length, runner area, taper ratio, etc. ITB's are also vastly complex, many more moving parts than a single throttle body.

There are three types of ITB's, slider type, roller bearing, and the type I am developing (the most common), butterfly valve. Slider's are significantly intricate, roller bearing are usually only good a WOT, which left me with butterfly valve which gives some sacrifice while maintaining good results.

Throughout the years many people have adapted ITB's from bikes and various cars to their engines. In fact, the euro version of my car came with ITB's stock. Now, here are a few reasons why I am not using ITB's from somewhere else to begin with.

• Account for Injector placement - The injector placement and angle can be crucial to the atomization of the fuel. The injection can also affect the turbulence and velocity of the airflow.
• Throttle Body Diameter - Although the usual size is sufficient (42mm-52mm depending on air capacity), I am adapting other elements that affect the sizing.
• Taper Ratio - This is the amount of taper from the top of the end of the runner/velocity stack, to the intake port. The taper is based off of a few figures regarding area, flow rates, Bernoulli principles, and intake valve area/diameter/location.
• Runner Length - Similar to the above problem, just in terms of length instead of taper
• Port area - Similar to the above, just in terms of area.
• Flow rates - Different displacement, different bore/stroke, piston speeds, and other factors will affect the runner length, taper ratio, port area, and overall design of the elements.
• Air Velocity - Just as flow rates affect the overall design, so does air velocity. Too much air velocity and the engine will be peaky or difficult to drive at low speed, not enough and it will choke on the top end. Different designs can increase or decrease air velocity.
• Reflective Value - Pressure waves are created due to reversion. When the intake valve opens this air will come rushing in and then the valve is slammed shut. Thus the air smashes into the valve and reflects back (reversion) and because of this, a low pressure area is created right in front of the valve, which will then suck the boosted air back to that area smashing back into the valve and repeating the cycle exponentially and infinitely.
• Wave Speed - The speed of the waves at different RPM due to reversion. The wave speed and reflective value have to be accounted for when developing runner length, taper ratio, air velocity, and flow rates as well as ECD
• ECD - Effective Cam Duration - The duration that the intake valve is open. Usually subtract 20-30 degrees based on cam design as a valve open .001mm cannot take advantage of a high pressure wave with the valve open at 1mm. ECD affects wave speed, reversion, and over all runner design

As you can see, every piece of information is interrelated and codependent on another factor. This is the difficulty in selecting a manifold, or ITB's. My design is being developed for a certain cam shaft, valve size, and head while considering all the above factors.

Well folks, thats all for now. Check back later for some more progress. Been crunching numbers all week to get a base down before completing the numbers!

Feel free to ask any questions!

[Slowroll90]

subscribed outta curiousity

[Zeuceone]

great info. Looking for to future updates. Keep up the great work.

[NitrousG35]

ITB's would be a major breakthrough for these motors. If that DBW issue can ever be dealt with, this would be an incredible peformance gain. I've seen S200's and they scream with ITB's. Keep us updated on this.

[Mike@ML-Works]

I apologize for not updating sooner, been a busy work week, especially with the holiday.

Injector Theory 101:

So let's discuss some of the key principles in intake design that have to be considered, or overcome. Recently I've been working on the internal runner, or the post throttle body runner which lays between the head and the butterfly valve. This area is critical in its design elements as it is the home for the fuel injectors, and also plays the greatest factor on the flow after the valve.

The injector placement is critical to the trajectory of the fuel, and since each variable affects another variable in this sort of development, you guessed it, the trajectory of the fuel affects atomization. Atomization affects power. Power affects my happiness.

Theres a 101 different ways to place the injector, and each way will have its advantages and disadvantages. The stock location is usually there because thats where it fit the best. However it does tend to go a little beyond that, it is optimized for fuel economy, and just best overall advantage. With individual throttle bodies, or tuned manifolds, placement becomes a little more critical. A close injector may allow for good throttle response, however it may lack the available means for massive amounts of power. A far away injector allows for better atomization, therefore you can run a larger injector and provide for greater power outputs.

The best of both worlds is staged injectors, lower injectors for idle to 4000RPM and another set of larger injectors for 3700-Redline. Notice the overlap between the stage 1 lower injectors and the Stage 2 larger injectors. When switching from one stage of injectors to the second stage there will be a time where there is too much or too little fuel. Too much when they overlap without the proper duty cycle tuning, and too little when the cutoff overlap isn't long enough. But being that I do not want to spend several thousand dollars on a Motec, and staged injectors are really only affective at WOT, we'll let that chapter die for now and digress to the basics. (If you have more questions, feel free to ask.)

Fuel atomization is the key in the game of fuel delivery. Ideally you want the injector right in the center of the runner for optimal atomization. That would be excellent if we didn't have to worry about injector location. So the most realistic placement, and optimal spot to maintain throttle response is to center the injector spray pattern with the centerline of the airflow. To aid in this design, you do not want the injector at an angle greater that 20° to the centerline of the airflow. This will provide the best angle to aid in atomization. (Illustrated Below)



The next challenge to overcome is the centerline of the air/fuel mix and the ports in the head. Ideally, you want to target the center of the port, but the valve stem is in the way. I choose to aim a little lower than centerline of the valve stem. This creates a pocket of vacuum behind the valve stem and will allow for better atomization, as well as introduce the mixture more evenly. The difficulty with manifold design is for both the injector trajectory, and the manifold angle to coincide and be a straight shot to the valve. Avoiding bends is also key, unless the air is spiraling in a vortex. Air travels at different speeds around a curve, and the only way to get the velocity to remain constant is for it to spin one full revolution through the bend.

Luckily for me, my design has eliminated a few disturbances like that through Bernoulli effect. I have also managed to get a straight shot for my injector trajectory. I'll post pics later.

Feel free to ask any questions.

[soxfan143]

Did you say that these ITB's are NOT for the K-Series?

[ImTheVoiceOfGod]

Jesus Mike.....

[Mike@ML-Works]

Originally Posted by soxfan143

Did you say that these ITB's are NOT for the K-Series?

Correct, they're for my car. ML-Works E36 Build

Originally Posted by ImTheVoiceOfGod

Jesus Mike.....

You can just call me Mike.

[NitrousG35]

Nice info.

[mattsbobo]

[Mike@ML-Works]

Well guys, finally an update with some actual pics of design. I've been spending the weekend trying to get something done, unfortunately I've had to alter things in the design multiple times - just tiny little nuances. But without further a due, pics:

[Slipp]

hmm looks cool.
how will you make it?
machine the bottom piece, and each throttle body separate then weld?
or start with a sold stock rect bar and machine as one piece? Alum?

is this something your going to try out on your car?

from this will you attatch some type of air intake to each tb or will you use small filters for each inlet?

[Mike@ML-Works]

Originally Posted by Slipp

hmm looks cool.
how will you make it?
machine the bottom piece, and each throttle body separate then weld?
or start with a sold stock rect bar and machine as one piece? Alum?

is this something your going to try out on your car?

from this will you attatch some type of air intake to each tb or will you use small filters for each inlet?

I'll be machining them on my mill and lathe at work. Some stuff I will use our partner shops CNC mills for.

The bottom flange is separate from the runners. The runners are comprised of three pieces. The injector boss, the flange that bolts to the runner to the main flange, and then the runner itself - those three pieces I will weld together. It will mostly be aluminum. The throttle bar will be T-416 Stainless steel, and the butterflies will be 360brass.

This is something I'm working on for my car. There will be a couple variations. One version will be open trumpets on each trumpet with just filter booties. However, this will be sucking in mostly hot air and will make the engine prone to detonation. The second variation will be a carbon fiber plenum that each trumpet is inside. The plenum will let the air in at the front of the vehicle through a filter to breathe cooler air.

EDIT: Here is an exploded view of the three pieces that makeup the runner weldment:

[Slipp]

ahh very cool.

[Mike@ML-Works]

Well...its 3:30am, I couldnt sleep due to engineering disease*. So heres a little bit more progress.



I have also included an exploded diagram as people on both forums seem to be curious as to how everything goes together. It looks pretty cool exploded if you ask me.



Next up, throttle body design. Goody!

*Engineering Disease - Encountering a challenge or difficulty and not being able to think about anything else until a solution is found.

[Mike@ML-Works]

Throttle body progress! Actually, the throttle bodies are pretty much done. The throttle bodies are 50mm non tapered. The butterfly valve will be made out of C464 Naval brass to avoid corrosion. They are then connected to a throttle bar that will be machined out of T416 Stainless. The throttle bar is guided through each throttle body with the aid of twelve SAE 841 Bronze Bearings for precise throttle control.







The next step is to work on the throttle return spring/lever arms, as well as the TPS location at the end of the throttle bar. I've already designed the throttle return system in CAD, now I need to develop it in Solidworks and add it to the assembly!

[2likru]

its about time someone attempted to do this. btw its a E36 not fa5 I'll still observe.

[KameraBoy]

wow. im definitely in for results. itb's on e36=hot.