Has anyone "written the book" on throttle body design?

[abneng]

Does anyone have a good reference work for throttle body design? Things like blade geometry vs. airflow rate of change, how bore size and taper affect performance and IAP sensor readings, opening cam theory, etc.?

 

[Lou Scannon]

Anything really good is probably proprietary to the company that wrote it and treated as a trade secret...

 

[EngJW]

I searched one time and found nothing. I needed to design a throttle body and had a drawing of a Zenith carburetor to compare it to. The weird thing about it was the shaft for the throttle was located .030" below the axis of the bore. No one I talked to could explain why. I would have just put it on the axis. The carburetor was used with a mechanical governor so it may have had something to do with the linkage alignment.

A throttle plate is not round if you lay it down on a surface. In the closed position it is tilted about 15 degrees so it has to be machined round in that position so it matches the bore.

That is the extent of my knowledge about throttle bodies. I hope there are some more replies.

 

[Bribyk]

The throttle plate shaft is off center so that vacuum or boost pressure will try to close the throttle plate, rather than open it, in the event the accelerator pedal loses control of the plate (cable snaps, fly-by-wire fails). It closes from pressure due to more plate area on one side of the shaft creating a closing force.

 

[patprimmer]

I totally agree with the last two posts

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[Bribyk]

As far as design, taper angles of less than 7 degrees seem to be the accepted standard (for pressure recovery). For a good compromise between power and driveability, most throttles are sized flow about 80-90% of WOT air at 50% opening angle. This gives a fairly linear relationship between power and pedal position for most driving conditions (of course you can tune this linearity with your linkage angles or cable follower radii) without compromising WOT power too much. An oval plate shape will positively keep the throttle from going past closed and opening the other direction, as opposed to using shaft stops. Most of the bad throttles that I've driven are the result of actuation issues such as excessive friction and deflection, resulting in poor feel and control.

 

[abneng]

Thanks for the input folks. I'm pretty sure I can figure most of it out but didn't want to ignore any reference work if it existed. Thanks again for the time in replying.

 

[PowerTripp]

Are you more concerned with throttle bodies for individual runner throttles, or single throttle plenum systems?

Are you more interested in butterfly throttles, or other designs like barrel, roller, slide, shutter, etc.?

There is a good bit of information available from those who work with each design for racing use, but there is no "bible" of written work that I am aware of.

I have found a few tips and tricks using IR and plenum throttle bodies that make a good bit of difference. But each require a different approach. And what looks good on the flow bench or dyno may not always be best on the street or track.

Blair and assoc. had an article in Race Engine Technology Magazine on CFD of bellmouth design that is interesting. It is available zipped in pdf form at

http://www.profblairandassociates.com/RET_Articles.html