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Discussion Starter #1
Well, this pertains to my mustang project, but not to mustangs in general. I have a little project that I am working on adapting BMW M3 individual throttle bodies to my engine. I already have the adapter plates being made that will allow me to bolt them up...that is the easy part:



These are the ITBs in question....as they are installed on a M3, the actuator rods are actually facing inward with the drive-by-wire actuator stepper motors actually in the valley of the v8 with the actuators being pulled inward and downward at a 45 degree angle to open the throttle plates. However, as I am installing them in my v6 the actuator shafts will be on the outside instead of the inside(this is so I can get the best injector angle...not to mention, there is no room in the valley on a 60 degree v6 unlike a 90 degree v8) so now what I have is a need for these actuator rods to be pulled downwards and outwards at a 45 degree angle...if I was going to use the actuator arms in the position they are on the throttle shafts...here is where the problem crops up...I can actuate the OEM arms that way only with dual throttle cables. The way the actuator arms are set up on the throttle shaft, I can unbolt them and move them anywhere I have room on the shafts(and since I will be losing 2 throttle bodies, I will gain more room on the end) and re-orient the arms anywhere I want simply by drilled a new hole in the shaft to attach the arms with...so instead of an outward/downward 45 degree angle I can get a straight outward push...or an outward/upward angled push...or any other type of push. So my conundrum is this: Do I

A. Use dual throttle cables to actuate both banks of throttle plates(attached either at the throttle pedal itself or split like an e-brake or motorcycle cable)
B. Use a bell crank setup like this:



Obviously the bell crank linkage is the better setup...but the goal here is to open both banks of throttle plates at the same rate so the exact same amount of air is entering each cylinder...and that also means I need to be able to open the throttle plates 100%...and I have measured the throw I need to do so...I need 1.5" of throw to go from fully closed to fully open...and I can't just go buying random bell cranks...and most of those available(like the awesome EFI Hardware one above) fail to list their throw. The obvious answer here is to fabricate my own bell crank...which is easy enough...but how in the world do I find the formula needed for the throw? The actuator arm moves 90 degrees from open to closed, so I came up with the formula of (Pi/4)*diameter of the actuator rod attachment points...in the case of 2 inch actuator mounting pattern that yields a throw of 1.57"(a little too much, but a 2" bolt pattern is just an example). Am I correct in this formula? Or is there something I am missing? The resulting number seems to be a logical number to me...but its a complete guess...so it leads me back to the conundrum...should I just use cables? I am ditching the fly-wire-wire portion of this for obvious reasons...I want a mechanical solution.
 

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Man, that’s a long post. I’m not an engineer, mathematician or scientist but I’d probably mock that kind of linkage up in paper.... bellcrank in cardboard, etc. Outside of Kindigit, that’s how it would actually be accomplished.
 

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I could help with the geometry, but I'm getting lost in your description. If you could draw a sketch and post that I'll take a look at it.

I like the bell crank idea as you do need both banks to open the same, and assuming the bell crank acts as a splitter to pull two cables, that seems to make a lot of sense.

An ideal solution might be one that allows you to adjust the attachment point of either the input cable or the output cables in and out relative to the pivot point, which would make the "throw" adjustable. If you can make the total travel a bit more than you need, you can use a spring in out cable where it will stretch for any travel past WOT if necessary.

Phil
 

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On my EFI stack setup, I am using a cable setup. My stack setup has the crank in the middle (not off the side like you're describing), but same concept.

Not sure if this will help, but I bought the Lokar Throttle Pedal...you can adjust the height of the pedal off the floor and the floor acts as the pedal stop. Then you don't need to get a bellcrank with the perfect ratio. As long as it opens enough, you can adjust the pedal throw so you don't open them too much.

Here's a link to the pedal

You'll need to get their cable too.

On thing I noticed as that the firewall flexed quite a lot when using the Lokar throttle (probably because of the pressure needed to open up my throttle bodies), so I doubled the thickness of the firewall where the throttle pedal attaches and it helped a lot. I wouldn't use the Lokar pedal without reinforcing the firewall if you find that it flexes with your setup.

Here's a shot of my stack setup. The bellcrank is in the middle and they use short adjustable shafts to pull in on both sides. I can get a better picture if you need one.
 

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Discussion Starter #6 (Edited)
On my EFI stack setup, I am using a cable setup. My stack setup has the crank in the middle (not off the side like you're describing), but same concept.

Not sure if this will help, but I bought the Lokar Throttle Pedal...you can adjust the height of the pedal off the floor and the floor acts as the pedal stop. Then you don't need to get a bellcrank with the perfect ratio. As long as it opens enough, you can adjust the pedal throw so you don't open them too much.

Here's a link to the pedal

You'll need to get their cable too.

On thing I noticed as that the firewall flexed quite a lot when using the Lokar throttle (probably because of the pressure needed to open up my throttle bodies), so I doubled the thickness of the firewall where the throttle pedal attaches and it helped a lot. I wouldn't use the Lokar pedal without reinforcing the firewall if you find that it flexes with your setup.

Here's a shot of my stack setup. The bellcrank is in the middle and they use short adjustable shafts to pull in on both sides. I can get a better picture if you need one.
It looks like you have roughly the same amount of room between your ITBs that I do(a little more actually), but your throttle plate shafts are far lower than mine...mine are about 3" above the bottom flange...and my TBs taped from the top to the bottom:



As you can see with this picture...by the time I have them installed I wont be able to fit a bell crank in there in the middle...so I will have to move it to the back and actuate the throttle shafts from the end. As for my dual cable idea...if I used dual cables I wouldn't be using a bell crank at all...the cables would actuate the arms directly, but cable stretch throwing off the synchronization is the concern...which is why you always see them with some type of bell crank with direct linkages

P.S. I actually have a Lokar floor-mount pedal and cable sitting on the shelf unused somewhere...I dont want to use that pedal though...its hinged horribly. I was planning on using a standard '69 mustang cable pedal with the Lokar cable....the only question is whether to get a couple more cables or to use a bell crank...but GT289 is probably right...will need to mock it up in cardboard to figure out the throw rather than trying to use math.

Suggestions for making the bell crank? Maybe start with a flanged bearing and add the brackets and throttle drum? Throttle drums are one of those things that no one really sells though...might have to raid a junkyard and find some random throttle body to take a drum from.
 

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+1 on the cardboard mockup, then make the parts from wood to have a working model to proof. Easy to cut a bellcrank from some paneling of thin plywood. Nothing wrong with a cable setup either as quality cables wont give you any stretch grief and should have no more upkeep than linkage, but the cool factor is better with the linkage.
Nice project BTW...
 

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That's a tight fit for sure. What do the adapters look like you're mounting it to?

If you have to build your own rube/goldberg type of setup, McMaster is a good place to start. I bought a stainless steel pulley for something I'm working on...maybe you could find one to modify for your needs. Here's the one I got....they have lots of sizes available.

 

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Discussion Starter #9
That's a tight fit for sure. What do the adapters look like you're mounting it to?

If you have to build your own rube/goldberg type of setup, McMaster is a good place to start. I bought a stainless steel pulley for something I'm working on...maybe you could find one to modify for your needs. Here's the one I got....they have lots of sizes available.




These are the adapter plates(I used Emachineshop's software to design them...port shape is very close as you can see, but a small amount of hand porting will be required to finish them...one plate can be flipped around to fit either side(though driver's side will need to be trimmed at the back). They are being made now and will be back to me within a couple weeks. Thanks for reminding me of McMaster, I had forgotten all about them...I will see if they have something suitable....the pulley you linked is fairly close, but not quite right for a few details.
 

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I'm guessing (and it's REALLY a guess) is that the easiest way will be to use both the cable and the bell crank. The cable, as the easy way to get to the setup and the bell crank to synchronize the two sides.
 

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If you need any type of linkage, these guys will probably have it, or they can make it for you.
 

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Discussion Starter #13
There is another option here I forgot to mention...I could always use a hex-bar type setup like a lot of aircooled VWs/Porches and Indy cars use:



Obviously I would need to design my own for the application, but the same basics should apply. An added advantage is that a hex-bar type linkage could allow use of the stock 6 cylinder throttle pedal assembly.

Here's the info on calculating the length of an arc but, as a thought... why not use an Arduino board and a potentiometer on the throttle to drive the OE stepper motors?

https://theengineeringmindset.com/arc-length-how-to-calculate/
Thank you very much, that will help regardless of which route I go. As for the stepper motors...well, I am trying to get away from the drive-by-wire. I drive a MTX 06 Mazda 6 daily currently...and I can't stand drive by wire with a manual transmission...it leads to stalling the engine accidently when it wouldn't happen with a mechanical linkage...the throttle response is just not what it should be...S197 and s550 mustang guys are always reflashing their ECU because of the throttle response issue stepper motors present(with a few actually taking their pedals apart and physically modifying the contacts). Besides...using Megasquirt, I will already be running a stepper motor circuit for each cam phaser. Now..if I were using the stock Ford ECU, I would certainly go the stepper motor route simply because there would be no other option.(The pot on the throttle would be a simple clever solution though...but the BMW stepper motor actuators even used are like $500 each...so that is another reason to avoid the things like the plague(not to mention being big and bulky...the fit down in a v8 valley well enough...but swing them to the outside and the only place you could mount them is the valve covers)
 

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Fascinating project! What year BMW M3 did those ITB's come from? Inquiring minds want to know... :)

A few years back I was studying the possibility of building a custom ITB setup for my Cleveland using Suzuki Hayabusa ITBs. The project never got off the ground though.
 

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Discussion Starter #15
A 2008 M3 v8 if I remember correctly...though most BMW ITBs share the same bolt pattern...M5 v10 versions curve outward somewhat instead of being perfectly vertical(considered them, but they had an extra hole for the idle bypass I didnt want to fool with(these ones have the hole too, its just in the main body rather than the flange area(cast into the head). Even the I6 throttle bodies are the same as the M3 v8...as long as they are from an E46-up...the ones you want to avoid for ITB projects are the E36 ITBs(those ones are smaller at 42-43mm instead of the 50mm of the later ones...which isn't a problem, but unlike the later ones, the E36 ITBs are joined in pairs...so that means that you are constrained by bore spacing on the engines you can use them on) 50mm is probably a little on the large side for my engine, but I figure it will be ok because the HP/cyl the 3.7L produces is very close to the HP/cyl the 4.4L BMW v8 makes...worst case scenario is that it pushes the powerband higher.....which would be an advantage if I could actually find some good aftermarket cams for the engine...but as is, maybe it will keep the engine breathing easy all the way to redline.

its a shame that Ford pushrod v8 ports don't lend themselves too well for direct-fit ITBs...but you could probably make an adapter plate without too much trouble, though it would probably need to be angled unless you can manage a cross-ram style setup with 2" stacks
 

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There's a simple linkage solution that I describe below. The drawing is a little crude but, hopefully, you get the drift. It consists of 2 flat "arms", slotted down the center, and mounted at the base so they can rotate. In the center is a "pin" that "floats" in the slot (plastic bushings/washers recommended). As one arm (or the other) is rotated, the "pin" drives the opposing arm down, in the opposite direction of rotation. Stick something like this in the center of the installation and attach each side to the outer shafts via bellcranks.

738534
 
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