is there a dyno proof floating around showing a tapered tb actually shows gains compared to a non tapered one?

 

I have not seen one on honda-tech yet. I'm interested myself. I sent my stock 2000 Si TB to maxbore for the 67-64mm taper....not sure if it really helped my setup at all. He does good work though.

 

also curious. i suspect it does help a bit to get the velocity up of the air coming in. though i think the effect is minimal, particularly in all-motor applications, maybe a bit more for forced induction. but, i also think the effect of the tapered TB would have the best possible results if matched with an intake manifold that possibly continued the taper down into the throat of the plenum. however, that would be a hell of a lot of machining / boring for a few ponies.

but thats just my .02

 

If a tapered throttlebody improved air velocity entering the plenum, why not extend that taper the entire length of the intake tube?

Also, what purpose, in terms of boundry layer and laminar flow, does a taper serve?

What happens to air charge as it enters a plenum? Does it speed up? Slow down? What exactly does the plenum do?

I think if you examine those three questions you can find the answer you are looking for. I'll check back tomorrow to see how things are going

 

Depends. If the air flow sees a converging taper like in a Tapered TB it can help minimize turbulence.

So if you have a long straight section of intake pipe before the TB, you can probally forego the taper.

Same sort of theory can be applied to intake ports.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Master of the Universe &raquo;</TD></TR><TR><TD CLASS="quote">
Same sort of theory can be applied to intake ports.</TD></TR></TABLE>

Oh noes! The secret is out...

I seem to notice alot of members on this board speaking of increased velocity in the intake tract like its always a good thing. And making no differentiation (sp) between increased velocity in the 1) intake tube 2) plenum 3) runners 4) port entry 5) short side radius 6) bowl 7) throat 8) seat

Despite the attitude that even i have berated him for in the past, MOTU continues to impress me in each cynical ( ) post i read from him.

 

Just send me $1,497.63 check for the hot tip.

Make it out to my favorite charity, Jerry's Kids USA.

 

There must be some benefit to it. I've seen similar designs on some high-end header collectors. My impression was that it was used at that point in the header to help step up exhaust gas velocity as it entered the b-pipe where it would normally slow down due to the larger area...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 00Red_SiR &raquo;</TD></TR><TR><TD CLASS="quote">There must be some benefit to it. I've seen similar designs on some high-end header collectors. My impression was that it was used at that point in the header to help step up exhaust gas velocity as it entered the b-pipe where it would normally slow down due to the larger area...</TD></TR></TABLE>

thats a magnaphone.....

 

If what you were speaking of was a reverse megaphone, that is for amplifying the scavenging affect or "pulling" of the air out of the combustion chamber. In terms of exhaust dynamics, velocity is negligable, mainly because as the gas moves from the combustion event to the tailpipe, it cools by over 1000degF, and as we know from the ideal gas law (PV=nrT), as the gas cools, it looses velocity.

So firstly, we need to know if indeed a tapered throttlebody increases velocity. As the cross sectional area of a tube decreases, pressure increases and that pressure differential causes an acceleration. So does this increased velocity make power?

In terms of straight air dynamics, the plenum simply serves as a controlled volume that separates the air, and fills the runners. As the air from the throttlebody enters the plenum, the air slows down and expands, this time due to the negative pressure differential. While we could limit the size of the plenum to minimize the pressure drop, the size and shape of the plenum is determined not by velocity of air, but by the wave action and Helmholtz resonance, where we attempt to tune runner length, diameter and plenum shape/size to compound the resonance frequencies into charges.

In a forced induction application, any velocity increase due to a tapered throttlebody would be negligible due to the fact that you are already charging the air to much higher pressure levels than any taper can achieve.

In short, a tapered throttlebody has no theoretical advantage on an internal combustion engine. But hey, not all theories translate into real world, so I would be curious to see if there could in fact be a difference in power on a dynometer.

 

Ok, not trying to threadjack but what about taper in ITBs?

Or taper in the runners of a plenum manifold? would there be measureable gains?

I thought I'd ask since you guys seem to understand physics more than most of HT

I have some ITBs that were ported and have a nice gradual taper, just wondering if it actually made a difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IT GUY &raquo;</TD></TR><TR><TD CLASS="quote">Ok, not trying to threadjack but what about taper in ITBs?

Or taper in the runners of a plenum manifold? would there be measureable gains?

I thought I'd ask since you guys seem to understand physics more than most of HT

I have some ITBs that were ported and have a nice gradual taper, just wondering if it actually made a difference.
</TD></TR></TABLE>

Thats not the same deal. Most all ITB's have a taper because the port is smaller than the velocity stack. If there wasnt a taper there would be a huge step at the bottom or halfway down.

 

I was asking about the tapering of intake runners on ITBs and Plenum manifolds having more of an effect than tapering a throttle body on a plenum manifold.

I understand that ITB's are tapered from the velocity stack, but I was really concerned with the actual TBs and runners themselves. Maybe I was showing my ignorance here. I understand that my question wasn't entirely on topic, but I thought it fit to ask about the runners. Sorry if I was out of line.

 

Me thinks: For ITB's I would think that the taper would help some, considering its a straight shot from the velocity stack to the intake port. This is different than the tapered throttle body on a regular IM setup because as 92TypeR pointed out, once it hits the plenum, it expands and slows down. No plenum on the ITB's, so no place to slow down, so the taper would be beneficial. Thats just me trying to think logically, and could be wrong. yes/ no?

 

that's kind of what I was thinking. would tapering the runners on a plenum manifold have more effect than tapering the TB? That would increase velocity in to the ports rather than into the plenum. Am I thinking correctly? or is this just more ignorance on my part? lol

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IT GUY &raquo;</TD></TR><TR><TD CLASS="quote">that's kind of what I was thinking. would tapering the runners on a plenum manifold have more effect than tapering the TB? That would increase velocity in to the ports rather than into the plenum. Am I thinking correctly? or is this just more ignorance on my part? lol</TD></TR></TABLE>

no thats a legitamit question which i would also like to know the answer to.

 

i dont think tapering would hurt much in any case, so i dont see why you wouldnt taper a t-body. in fact stock t-bodies are already tapered as well.

now is there any possibility a taper would hurt performance?

 

I think you got a good understanding of what is happening. The taper on an ITB setup is cricital for accelerating the air into the valve. In fact, velocity stack tuning can amount to some good gains. I would, for obvious reasons, mess with runner length and diameter first, but different length/sized stacks can make a noticeable change in power.

The comment about hurting performance with a taper, sure if the taper was so severe that it actually limited the amount of air into the plenum, think of it as a restrictor instead. But the same can be said for a straight section of tube as well. Just in terms of airflow, your BMEP determines how much air you can consume, so you would never be limited by having too big of a throttlebody, only too small.

There is a lot going on with intake dynamics. Induction tuning is, from my experience, 50% theory and 50% trial and error. The physics behind the madness are all constant. You will always have that on your side. It is the wave action that can be hard to wrap your head around, and the only real way to quantify it is to perform controlled tests.

 

will a 68mm t-body tapered to a 65mm butterfly (65mm matched intake mani) be a restriction on a 1.8L lsvtec? s2s2 cams? peak power 8500?

 

depends on your manifold