[Concept] Quad throttle plate (easy ITBs)
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Thread: [Concept] Quad throttle plate (easy ITBs)

  1. #1
    Fellow Frogger!
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    Default [Concept] Quad throttle plate (easy ITBs)

    Introduction
    I've been looking for a way to affordably install quad throttle bodies onto my 206 GTi. After seeing prices on professional systems, I decided I would have to build my own. Butterfly type ITBs would be very difficult to design and build, due to the tricky axle which needs to run between each body. I thought of a way around this, and it turns out so did many racing teams through the years. The slide throttle. BMW used these for racing on their e30 M3. Here is a picture:
    [URL=http://img225.imageshack.us/i/slides1.jpg/][/URL

    Why aren't these stock?
    The reason they aren't used for road vehicles very often is that the overlap of the two circular cutouts as they move changes area in a very non-linear pattern. This gives the accelerator an "on or off" feel. This makes taking off WITHOUT frying the tyres difficult.


    Why use a circle?
    Throttle bodies and intake systems are always circular to allow a vortex to be formed. In the days of carburettors, a vortex was created by having a perfectly circular tube before the carburettor to mix the fuel into the air more effectively. With fuel injectors, the fuel is sprayed in tiny particles, so mixing is not an issue. The use of a vortex actually impedes the flow of air, since centrifugal force increases the density of the air on the outside of the tube, where there is surface friction. A vortex also creates turbulence when it turns a corner, such as in the engine head. That is the reason PSA intakes such as the one in my car change between circles and ovals for the cross section of piping, to stop vortexes and allow laminar flow. The only advantage to circular piping with fuel injection is that it has the smallest possible ratio of surface area to volume, to decrease friction.

    My concept
    My idea is simply using a square pattern for my throttle plate's cutouts, which has the advantage of creating laminar flow, the disadvantage of a slight increase in friction against the sides of the duct, and the huge advantage that the throttle response will be almost perfectly linear, even more so than the stock butterfly valve. Here's my current design, almost ready to send to the CNC machine (which I have yet to find one to borrow, maybe my uni has one I don't know of...)



    Let me know what you guys think, and please tell me if I'm mistaken about something and will destroy my engine by trying this

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  2. #2
    I might be slow... DRTDVL's Avatar
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    How easy is it to get some toyota throttle bodies there?

    i.e.
    http://www.trademe.co.nz/Trade-Me-Mo...-352974918.htm

    http://www.trademe.co.nz/Trade-Me-Mo...-352976683.htm

    http://www.trademe.co.nz/Trade-Me-Mo...-353615123.htm

    http://www.trademe.co.nz/Trade-Me-Mo...-353621738.htm

    Then knock out an adapter plate, really common in the uk and other places to use 2 x bike throttles

  3. #3
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    Personally I have never heard of square throttle plates but am fascinated by your idea and do hope this is a long and technically successful thread.

    There are plenty of clued up race engineer types on here who will have their own slant on this and I will be watching with egar anticipation.

    Good luck
    Graham

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    1000+ Posts PeterT's Avatar
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    This has indeed been done before. I'm not sure who owns this car now. But worth investigating.
    Attached Thumbnails Attached Thumbnails [Concept] Quad throttle plate (easy ITBs)-pug405.jpg  

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  5. #5
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    They are not used on production cars because
    1. They stick. This is improving considering thje surface finishes that are available today
    2. They are very hard to make so they do not leak / suck air. If they leak air around the throttle plate you will never get a consistent idle.

    Even getting individual throttle bodies to not stick due to heat soak and get a good idel is hard.
    Adrian Wuillemin

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    Quote Originally Posted by Blufires View Post
    Let me know what you guys think, and please tell me if I'm mistaken about something and will destroy my engine by trying this
    I don't think you'll destroy you're engine but you could be a safety hazard on the road if the throttle gets stuck open.
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    How will you overcome the friction between the two plates, yet the necessity for an airtight (or near enough) unit? Injector placement will probably need to be post-butterfly (throttle plate?) i.e. in the intake runners to prevent fuel puddling at partial throttle.

    The only advantage to circular piping with fuel injection is that it has the smallest possible ratio of surface area to volume, to decrease friction.
    Very interested in progress updates.

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    Thanks for the encouragement. No progress yet on the build, just design ideas.

    DRTDVL:
    The reason I won't just adapt 4AGE ITBs is because I like to be different, need a project to work on, and do not have the skills or equipment to balance butterfly ITBs. Slides never need balancing. Also $500 is a lot when I could just mill a better (there's no sideways valve at WOT, so no turbulence or obstruction) part out of sheet material.

    There will be a very large spring in the slide to stop a WOT jam, but if it does happen it's no big issue, since there are no motorways in Cairns, I can always just turn ignition off, pull over, unjam, test and go.

    The leakage problem comes from the use of bearings to prevent sticking. I won't need bearings, as I plan to use thermosetting plastic as the material for this. I'll also have an extra aluminium plate bolted onto the bottom to weld the runners onto, and to provide added rigidity to the plastic slider mechanism. Not only is thermosetting plastic easier to mill than aluminium, but it creates a low friction seal on its own (I've seen plastic engines with no piston rings made from this stuff). Also this has almost no size increase with heat, so jamming from the inner plate expanding won't be a problem like it would with metal.

    Now I think of it, I might just make an MDF mould for the parts and go to my old school and injection mould it from plastic, that could prove the easiest way to make it.

    Now I've had a play with unplugging various things from my throttle body to find out what does what, and I was just looking for some advice now on how to mount:
    A. The MAF sensor.
    B. The Idle servo.
    C. The TPS sensor.
    So far I've thought the MAF sensor could go just past the (pod) air filter in the airbox. The diameter of the pipe there will be the same as the original mounting spot, so the velocity to mass ratio should be the same, and retuning of this will be easier.
    I was thinking the Idle servo could stay in the current throttle body, and I could run small vacuum tubes from the outlet of the idle section of the throttle body (it's a 50mm butterfly next to a separate section for idle) into the runners.
    As for the TPS, does anybody have any info on how this works? Is it PWM or 0-5V? Is there a substitute part anybody knows of which would be easier to mount?

    Thanks again for your support, and any information you can provide on the throttle related sensors.

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    Quote Originally Posted by Uffee View Post
    I don't think you'll destroy you're engine but you could be a safety hazard on the road if the throttle gets stuck open.
    Just to harp on the safety aspect again, modifying the intake system is against the ADRs and if you did have an accident that could be attributed to the throttle bodies it could get dicey with your insurer/police... Seeing as you're making them yourself, the buck stops with you as to the safety of the system.

    Take this advice as something to be aware of rather than a judgement on your design/fabrication skills.
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    i am all for a good project, but i would note that if you are just converting from an ITB, you probably arent going to get a lot of extra anything for your efforts, IMHO.

    the toyota ITBs are really cool, but note the injectors sit in the manifold to which the ITBs bolt, so you have to not only fab a manifold, but also the injector bungs have to go in it. just saying...

    jenvey in the UK make a variety of ITBs including duals with the same mount pattern as webers. you can buy a pair of duals for 440quid, which is pretty cheap. add the fuel rails and an air bypass valve and manifiold, and you are still talking <$1000AUD. you still need a manifold of course, but it is pretty cheap for all the hardware, and avoiding a lot of hassle.

    i have seen pictures of MKII jags, i think, using sliding throttle plates just like contemplating, fyi.

    re the potenially liability from an accident caused by your stuck home made ITBs, my feeling is that as everyone is charged for absolutely anything these days, it really wont matter why you drove at full tilt into a bus of crippled brownies, and whether it was your lead foot, or a mechanical malfunction will be rather moot. the important thing is to a) make it so the throttle plate doesnt stick and b) put your foot on the brake and switch off the key!, and c) that wont be a problem as you will of course have taken the opportunity to include soft and hard rev limiters in the electronics, right?

    cheers.

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    I am running stock engine completely at the moment. This is because I didn't want to waste time with non-mods like an exhaust system and an air box with a pod filter. If I'm going to spend money on the engine I want 20KW or more. I'm aware of Jenvey products, but the price is a lot for what you get, and the setup is very complicated (balancing anything isn't fun, propellers, crankshafts, unicycles... throttle bodies can't be any better).

    I'm looking at a cam upgrade (found a 290 degree set for a 307 with the same EW10J4 engine on ebay at ~$550 with postage) as well as this throttle plate.

    The piggy back ECU to get most of the performance out of these modifications would need to adjust the MAF sensor input to the ECU, such that it would acknowledge the extra air it was getting. Would I also need to adjust the ignition timing? I was looking at the Haltech Interceptor for ~$700 with postage, which will do ignition and MAF mapping, but just stumbled upon the Apexi AFC-Neo for ~$450 with postage, which only adjusts the MAF sensor reading, but allows for mapping directly on the unit from inside the car, so I could change to not intercepting the signal at the push of a button. Does anybody have some good alternative suggestions or opinions on piggy back ECUs? Thanks for your considerations.

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    just re the jenvey throttle bodies, i will say that i dont think balancing them is an issue. if you had 2 pairs, that is only two items to balance, and it is only an adjusting screw. i thought you didnt get much for your money when aussie/sterling cross was at 40p, but now it is at 63p, it looks alot different!

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    I've just read a bit, and found that many Japanese race tuners are using a very large (100mm) single throttle body on their inline track engines in favor of ITBs. From all I can find, this give more low down torque but less high end power. This is preferable for track use (greatly differing speeds, whereas rally cars need power mainly in the top end, as their wheels are slipping when traveling slower). I'm starting to think that I'll use a 75mm or 90mm throttle body for/from a V8 holden or ford, and design and build my own tuned plenum (I've looked for these for sale but haven't been able to find one, every pug tuner seems to be looking at ITBs only).

    Again, please give me some feedback on this, as I'm interested to hear from somebody with more knowlege of tuning if this will work/be more effective for a road car.

  14. #14
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    Have a look here:

    I'm building a custom ITB setup for my Alfa at the moment. What I've found is that fabricating anything (mine is relatively conventional) takes a long time, let alone trying to develop an almost completely new setup from plastic.

    If you're set on having the interesting project of the plastic slide throttle, I'd definitely try and make it on the bench and then bolt it up to your car later, otherwise your car might be off the road for a long time!!


    http://www.team-integra.net/sections...?ArticleID=471

    http://www.team-integra.net/sections...?ArticleID=484

    www.not2fast.com/gasflow/Lecture08.ppt


    Best of luck and look forward to updates
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    I might be slow... DRTDVL's Avatar
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    The real advantage from itb as equal airflow into the cyclinders, by changing back to a plenum based I take you will need you have serious think about the plenum design to avoid imbalances, even though your potentially running a much larger throttle you will need to work out fill rates vs flow requirments. Are those jap engines turbo??? Charged (turbo or super) don't have the same flow/velocity imbalances in the cyclinders due to the pressurized intake plenums.

    A friend of mine has just spend the last 2 months redesigning his intake plenum to try and equal out his flow and velocity into each cyclinder of his head. This was done using cad software and cfd software to test the designs, it took a while to get something optimal to conform to his space requirements.

    You will also need to work out your desired runner length for the rpm range your targetting. There is a fair bit of information floatng around about how to best calculate the runner length.

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    Quote Originally Posted by Blufires View Post
    I've just read a bit, and found that many Japanese race tuners are using a very large (100mm) single throttle body on their inline track engines in favor of ITBs. From all I can find, this give more low down torque but less high end power. This is preferable for track use (greatly differing speeds, whereas rally cars need power mainly in the top end, as their wheels are slipping when traveling slower). I'm starting to think that I'll use a 75mm or 90mm throttle body for/from a V8 holden or ford, and design and build my own tuned plenum (I've looked for these for sale but haven't been able to find one, every pug tuner seems to be looking at ITBs only).

    Again, please give me some feedback on this, as I'm interested to hear from somebody with more knowlege of tuning if this will work/be more effective for a road car.
    Over-sized throttle bodies look pimping but kill power. Marginal improvements in throttle response are far outweighed by drastically lower air speeds. When a mate of mine removed his K-jetronic fuel system from his BMW 320 he put a 70-ish mm throttle body (I think it was an aftermarket Integra one?) and it was gutless. Went to a much smaller one and it improved it heaps.

    I reckon the Japanese race cars would be turbo? Thus as the boost comes in at higher RPM it would offset the low air speeds you'd get with an N/A car.

    I was sitting up late one night watching the ITCC and the commentator mentioned that they ran restrictor plates. Although I can't remember the details, it was very small: 30-something mm. Those things make serious power.

    There are calculators on the net to help with throttle size selection. Dai Rally has a good one.

  17. #17
    I might be slow... DRTDVL's Avatar
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    Turbo Cars in nz run a 36mm restictor plate.

    Chez did you friend do anything to improve the airflow into the throttle body?

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    The one I was talking about was a naturally aspirated RB26DE in a touring skyline. Having a large throttle body does reduce the airspeed AT THE THROTTLE BODY. If the intake ports are smaller (they always are, unless you have some awful 50mm throttle body like mine stock), the air will speed up at the ports, just like a hose with a small nozzle. If the throttle body is the same area as the 4 intake ports combined, you will still lose airflow due to fluid loss (friction on the pipe's internal surface).

  19. #19
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    Just a bit of a thread dig, because I'm currently playing with ITB's.
    Did you ever achieve any of this?
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    I'm glad you dug it, Links above by Lunch cutter are fascinating!

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    Quote Originally Posted by DRTDVL View Post
    The real advantage from itb as equal airflow into the cyclinders, by changing back to a plenum based I take you will need you have serious think about the plenum design to avoid imbalances, even though your potentially running a much larger throttle you will need to work out fill rates vs flow requirments. Are those jap engines turbo??? Charged (turbo or super) don't have the same flow/velocity imbalances in the cyclinders due to the pressurized intake plenums.

    A friend of mine has just spend the last 2 months redesigning his intake plenum to try and equal out his flow and velocity into each cyclinder of his head. This was done using cad software and cfd software to test the designs, it took a while to get something optimal to conform to his space requirements.

    You will also need to work out your desired runner length for the rpm range your targetting. There is a fair bit of information floatng around about how to best calculate the runner length.
    I've often wondered why more cars don't use a merge collector design to feed the intake runners.

    If it can be packaged, it allows almost perfectly even cylinder distribution. There was a NA Toyota 4 cylinder that ran one OEM a few years back iirc. Really neat design.

    Last edited by mistareno; 17th May 2017 at 08:47 PM.

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by chez00 View Post
    Over-sized throttle bodies look pimping but kill power. Marginal improvements in throttle response are far outweighed by drastically lower air speeds.
    My EFI fuego went from a sequential twin choke TB (small primary/large secondary) to a large single TB.
    The throttle response was anything but an improvement.
    You could say the accelerator pedal was more like an on/off switch than a sequential device.

    There was little difference to the engine between 5% open throttle and WOT and that 0-5% was a tiny amount of movement with which to gain some sort of drivability. The fuelling map reflected this too.

    I coped mostly, because the car was such a hoony car, but driving in sydney traffic in 1st/2nd gear was painful, especially as the fuego had a heavy cable clutch and such a low first gear.


    Jo
    Last edited by jo proffi; 18th May 2017 at 03:44 PM.

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