A post on "that other MINI forum" :D made me think about this.
I've never seen this defined. If it has please point me in the proper direction.

The math is simple, but beyond my meager skills;


The CFM rate of the motor is something that can be calculated. The flow rate of the TB is also a mathematical known.
Why has no one ever put 2 and 2 together and said " Hey this TB can handle all the flow requirements of this motor" or not.

As far as the "it smoothes the flow" argument that might be valid for NA motors but the SC is pretty much going to devastate air flow.

Personally I'd like to see the math and the answers

 

Here's what you are most likely going to find. The SC is going to grab all the available air it can. You then work backwards identifying the bottlenecks in the system. First would be the TB to SC tube, since the stock unit is fairly oddly shaped, with pinches and angles, it will limit the volume primarily by turbulence. So you have a turbulent flow condition, which is much less efficient than a laminar flow condition. We saw a similar limit in the AGS V.1 tube, which is why V.2 came about, and resulted in a 6.4 HP gain over the V.1 on the same car.

Next step back is the TB itself. Again, flow area is a limiting factor, but your real enemy is going to be turbulence. Significant turbulence has the effect of cutting the flow area down significantly, so your effective flow is reduced. You can overcome this two ways. You can eliminate the sources of turbulence, or you can make the primary flow area larger, resulting in a larger effective flow area. You can also do both, resulting in two sources of gains.

Same principals apply to the TB to filter box tube, and even the filter itself.

Best of the best is to have the smoothest airflow with the largest volume. A lot of people have noted that a larger throttle body results in quicker engine response. This would make sense if you are able to have more available air, and consequently more available boost, quicker due to smoother and larger volumes of air.

Hope this helps out some. I'll work the math out if you like, but I did a lot of the work already, so I just need to dig it up. For a proper sales pitch, see the results here: http://www.m7tuning.com/main.m7/store/10005

 

edited: removed because my post was not relevant to the criteria of the question

 

You change the dynamics of the system when you pressurize it with a turbo before the TB, so then it doesn't become a weak link in airflow. I assumed we were talking SC only MCS's.

 

Will,

Regarding the TB to SC Tube... Does M7 sell just this part, so I could fit my ALTA or a WMS HDI to the throttle body? It seems to me that the logical best approach to this whole beginning of the intake path is to have a sealed intake box drawing from cold air sources, through an improved throttle body, and then through an AGS type TB to SC tube.

 

True. Didn't think of that...removing my first post.

 

OK, this may help.
Let's just stick to ideal flows.No hoses, no curves, no turbulence.
If the TB sat right on the SC would the OEM TB become a limiting factor?

Anything mentioned above actually lowers the requirements of the TB. Any restriction(s) between it and the SC would do so.
Analogy time.
You have a straight tube, think straw. Lets say it provides ideal flow for the requirement. You pinch the straw 3/4ths of the way down and restrict the flow by 15%. The first 3/4ths of the straw still have ideal flow. Making the straw larger from the beginning to the restriction point isn't really going to help flow through the restriction and beyond.

I just want to see proof that the TB cannot flow enough CFM.

 

if you do any electronics, the analogy is perfect.

Almost all our parts will flow more with larger pressure deltas. It's not like the TB will flow up to X CFM and then stop. Drive a larger pressure into it, and get more air through it.

Some testing on TBs using 91 octane showed for a pretty stock car, there isn't much gain to be had. (Pully, plugs and one-ball). I think to get benefit here, you really need head work, maybe a header too. Who knows what I would have seen if I'd been running better gas, and the results weren't skewed by timing retard.

FWIW, with a 60 mm TB with an unmachined inner shaft (an early M7 unit), and the HAI, we loose about 8%-9% of the air pressure at red-line. So that sets the upper limit to what can be achieved with improvements to the pre-SC airpath.

Matt

 

Have a degree in electronics. Don't remember crap. Haven't used it in 18 years

Please clarify that last paragraph. Does the pressure loss indicate the is more flow available?
As in using a lower resistor value so you have a lower voltage drop across r?

 

The 8%-9% pressure drop is due to flowing through the filter, TB and TB-SC tube. Some pressure gradient needs to be there (otherwise no flow), but any improvements would be limited to 8-9% increase in air pressure. But this isn't a small number. Thinking of our cars as a 200 HP motor (there's about 25 HP loss to drive the SC), that's a bit less than 20 HP available to be found, with a perfect air intake path.

And yes, a lower "resistor" value will have higher "current" (read airflow) at the same "voltage" (read pressure drop). Another way to put it is that for peak flow rates, there is less pressure drop before the SC, hence more air density at the SC, and more air stuffed into the motor.

Hope that helps!

Matt

 

Yes it does.

Leaves things a vague about whether or not a larger TB does much though.

I'm thinking "save the money". It's 50% of a set of FSDs. 40% of an overpriced header. 35% of a new head/cam combo

 

it will probably make a difference. But I haven't tested it myself to know for sure....

Matt

 

im boosting over 18lbs with a 17% pulley and all my parts...so i would think something is working right...

 

That is with a stock TB?

 

65mmm, HAI, jcw s/c, jcw head, obx header no cat, borla street thats all my "air moving" components..

 

this is exactly what i've been saying for like 2 years now. ever since the very first AGS thread came about during its first prototype days. i even got a PM sent to me from Randy i believe when i posed this question, and he said they would have a solution for this, which we all know by now they don't. think about it, an HDI with a silicone tube made a little longer (MCSa maybe), going from airbox to 60 or 62mm TB, connected to AGS tube. could be the best possible flow characteristics that we've been looking for.


https://www.northamericanmotoring.co...&postcount=179

 

Wasn't the whole point of the HAI and AGS to reduce the turbulence of the air from going all the way to the back of the engine bay and then coming back to the front, thus reducing air density?

 

The current AGS tube moves the TB, eliminating the TB support braket. It doesn't allow for bolt ups to CAIs that are designed for the stock TB location. But since it has it's own HAI like filter, this is a non-issue.

FWIW, some have said that you can heat the stock TB-SC tube with a heat gun and help out it's original design a bit by opening it up, but I haven't tried. Many have improved it by removing the glue "casting flash" that can impede air flow as it comes from the factory.

And MSFIT, if you open up the head more, you may loose some boost, but gain power. TonyB lost a lb or two of boost with his exhaust, as it allowed for better airflow. Higher boosts are because the head can't digest all the air that it's getting fed.... I'm sure the JCW head is better than the base head, but some of the port/polish jobs out there are flowing quite a bit better than the JCW offering.

Matt

 

Ya I am looking at buying a better head/cam/intake manifold, the people in phoenix (don't remember their name, but isellem was telling me about it) have a nice one that I want. And I see what you mean about the loosing boost...but are you actually like "loosing" the boost or is it just the same boost in the cylinder but not as much backed up air? if that makes sense.....I have a hard time saying what i mean sometimes

 

means less in the intake!

Matt

 

What the Dr said.

An Eaton builds boost based on resistance to flow. Less resistance means you have better flow. Which means you need less boost to accomplish the same amount of air density per cylinder.

I would think, but don't know for sure, that this would also lower charge temps after the SC.

 

Great,
Now after reading this all, all that we need is an astro physicist on the NAM board to clear all this air CFM confusion that everyone has regarding intake and intercooler. Someone go recruit one!

 

I think there's an aeronautical engineer that lurks around here. Maybe more.

Still haven't seen my question answered though?

What does the motor flow and will the TB keep up.

 

400+ CFM at redline. And the stock TB can flow this amount as well, it's just that it may drop some pressure, so you're going to get less air into the motor. Any conductance path will have resistance to flow. If the stock TB is one of the larger contributors, getting an worked over one will help. If it's not, then it won't.

On my car, larger TBs didn't give me anything extra.

Matt

 

Thank you