Custom Throttle Body

[drivetrainUW-Platt]

Hey,
I'm going to be working on a custom throttle body over the summer and I was wondering if anyone had any advise for me. I'm basically wondering how I should do cable mounts, if I want bearings/busings for the shaft, and if it should be designed for push-pull or just a flexible cable. Also wondering what size bore you would recommend for the 600cc engine
thanks

[drivetrainUW-Platt]

Hey,
I'm going to be working on a custom throttle body over the summer and I was wondering if anyone had any advise for me. I'm basically wondering how I should do cable mounts, if I want bearings/busings for the shaft, and if it should be designed for push-pull or just a flexible cable. Also wondering what size bore you would recommend for the 600cc engine
thanks

[Jay Fleming]

I dont know a whole lot about throttle bodies, but I know that you don't need a real big one. To try and calculate the size, figure out your mass flow rate at the maximum rpm you want to design for, assume the velocity behind the throttle body is probably 30 m/s or so. Then you can calculate the area needed. Depending on what size you have, figure increasing the area by 15% or so because of the area taken up by a throttle blade. I think a slide type throttle body would be easier to manufacture, but if you choose to run a TPS sensor, it may be a little more difficult to rig it up on a slide throttle body. I know this doesn't give much insight, but may help a tad.

[Denny Trimble]

If you build a slide throttle, make sure you don't have problems with it sticking when you lift off the gas at high RPM and present it with a large vacuum. Don't ask how I know...

[drivetrainUW-Platt]

I have never seen a slide TB, just carbs. I was planning on a traditional butterfly type TB.

[Patrick W. Crane]

the slide is nice cause at WOT you can have really nice laminar flow. no butterfly to screw with flow. they are a bit of a pain, but can be pretty trick if done right. denny is right though, they do like to bind. if you could have it slide along some little ball bearings, you could probably get rid of all the binding. also since they can be made to pull linearly, they work great with push pull cables. if you're into them...

[drivetrainUW-Platt]

Carol Smith recommends push pull for a throttle cable, personally I disagree with him on that one, ya they arent gona fail in tension, but theres a lot of resistance in those, so you better have some damn good return springs, they add weight and are only flexible to a certain limit...what we are currently running is a higher end brake cable from a bike shop, It is teflon coated. They buy the cable and casing in bulk so we can get any lenght, its cheap and they return nicely...durablity is lower then with the push pull, but look at a production car, you will see similar cables in there.

[Buckingham]

If "what Carroll recommends" is coming from one of his "to win" books, keep in mind that those comments are geared towards racing circuits with very high speeds and/or banked turns and walls. In those situations a throttle cable failure can be a life or death problem. In addition, a multi-throttle engine would have more throttle friciton, and the heavier push-pull might be necessary to ensure proper actuation of all throttles.