×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Throttle Body design

Throttle Body design

Throttle Body design

(OP)
I was looking at the TB on my 16v 2L which is 64mm - there are aftermarket units that are 68mm available, however I got to thinking that a slide type TB at 68mm might flow more for given cross sectional area open vs a conventional plate style. What are the pros and cons? Why isn’t there more slide type TB used for automotive use?

Thanks

RE: Throttle Body design

They give very little advantage over a slightly larger sized butterfly valve.

They are more complex to make, harder to seal reliably for a stable idle and have much higher friction and potential to stick, making power control difficult.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Throttle Body design

(OP)
Thanks, makes sense, Taking it one step further then.. If the intake manifold is a 70mm bore and the TB is 64mm, what will happen if the bore is opened up to 70mm? I'm guessing low end response would change, would injector size need to be increased to compensate for increased flow? Would this type of change seriously affect the drivability? Is this why it would be presently at 64mm (design compromise)


thanks

RE: Throttle Body design

I don't know without inspecting and testing your system.

If you seriously increase the airflow, you might run out of injector fuel flow.

Increasing throttle bore dia might increase airflow, depending on how restrictive the current one is compared to everything else in the system.

Increasing throttle body size at the numbers you state probably will increase airflow.

It should not prove detrimental to bottom end power.

It will most probably increase inlet tract noise.

It will make the throttle action more sensitive or touchy or snappy.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Throttle Body design

You could effect a modest increase in WOT flow area by thinning the throttle shaft around the butterfly, converting the cross section from two half- rounds to two flattish rectangles,  or two shallow half- ellipses.

A couple of hours attacking the shaft with a Dremel tool should do it.  I'd leave the shaft at full thickness around the butterfly retaining screws, and stake and Loctite them on reassembly.



Mike Halloran
Pembroke Pines, FL, USA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources