Boring out throttle bodies
Many of the newer throttle bodies have somewhat of a ridge.
[img]http://i223.photobucket.com/albums/dd270/mpgchris/StockTB1.jpg[/img]
![http://i223.photobucket.com/albums/dd270/mpgchris/StockTB1.jpg[/img]](http://i223.photobucket.com/albums/dd270/mpgchris/StockTB1.jpg%5B/img%5D){kind=link}
It is believed that by boring this ridge out, thus providing a consistent 58 mm (in this case) flow would increase. I decided to put 2 throttle bodies on the flow bench to find out. One is stock, as pictured above, and one is bored out for a true 58 mm through the entire conduit.
[img]http://i223.photobucket.com/albums/dd270/mpgchris/BoredTB1.jpg[/img]
![http://i223.photobucket.com/albums/dd270/mpgchris/BoredTB1.jpg[/img]](http://i223.photobucket.com/albums/dd270/mpgchris/BoredTB1.jpg%5B/img%5D){kind=link}
Depression ("WC pressure) - Stock cfm - Bored cfm 5 - 202.0 - 192.5 10 - 285.7 - 271.2 15 - 347.1 - 333.3 20 - 398.9 - 382.3 25 - 439.0 - 423.4 28 - 462.8 - 445.4 30 - 476.6 - 461.1 35 - 511.6 - 493.8 40 - 539.0 - 521.2
It would appear that the ridge actually aids flow and is better than a straight through bore.
Mike
Comments
Re: Boring out throttle bodies
Wow, very interesting!
Re: Boring out throttle bodies
Someone is playing with his new flow bench! :D
Re: Boring out throttle bodies
[quote="ssheen"]Someone is playing with his new flow bench! :D[/quote] I even flowed some exhaust pieces to test some concepts.
Mike
Re: Boring out throttle bodies
I'm trying to visualize the air flowing through the TB into your flow bench. A few questions.
How does the intake of your bench match up to the TB? Does the TB "dump" into a large open plenum before the vacuum is measured? Or is it flowing smoothly into a "tube" that matches the ID of the TB?
Re: Boring out throttle bodies
I have a head stand set up with a 3.55" bore. On top of that I used a 5/8" plate with a 61 mm opening. So, more or less, it does dump into a larger opening.
Mike
Re: Boring out throttle bodies
Here is my theory. :D
[url=http://img690.imageshack.us/i/stocktb1.jpg/][img]http://img690.imageshack.us/img690/2217/stocktb1.th.jpg[/img][/url]
In the stock TB, the air flowing through the bore "sticks" to the edge and is pulled toward the outside of the bore, therefore making the "exit" of the TB (entrance to the plenum) wider.
[url=http://img63.imageshack.us/i/boredtb1.jpg/][img]http://img63.imageshack.us/img63/1143/boredtb1.th.jpg[/img][/url]
In the bored TB, the air flow sticks to the entire length of the bore until the very outer edge and THEN tries to make a sharp turn. This bends the airflow at the edge and creates a "pinch point" that would probably be just a little above the bottom of the TB.
Then again, this is just my theory. What do you think?
Re: Boring out throttle bodies
Are you saying I'd get radically different numbers if I discharged the TB into a matched conduit?
Mike
Re: Boring out throttle bodies
I have absolutely no experience with a flow bench, but I would guess so. I wuld think that a "funnel" from the TB to the flow bench would show the biggest gains. However, doesn't the TB dump into an intake plenum when installed on the engine? I'd want to test it in the same way as it'll be used.
Re: Boring out throttle bodies
Usually there is some sort of radiused transition from the throttle body to the plenum, but not always. I think the point is that the two TBs were compared "apples to apples", where the focus is on the difference between the two. Of course, the numbers could change with different conduits etc, but they should change equally for both TBs. At any rate, I was fascinated by the descrepency between a "smaller" opening and a larger straight opening. Along the same lines, I used 5 tubes of epoxy on the Hyundai X Prize head intake ports and managed to pick up a couple of CFM.
Mike