Stock Throttle Body CFM Flow Question

[MSq5]

The CFM flow rating of intake systems is typically measured at 28" of H2O, which corresponds to 1.01 psi.

Much has been said on this board and others about how much various intakes flow using that standard.

My question is limited to the stock throttle body of the 3.0 TFSI engine and its CFM flow characteristics under that protocol. Has anyone flow bench tested it? I gather that it is 73mm inside diameter and that it is actually smaller than the supercharger intake side, if this is true. How much of a bottleneck is the throttle body? Is it the major bottle neck?

Do we have flow data using this standard protocol on the stock throttle body and what does that data show?

[brs2c]

I have no technical data for you, but running 3.5” all of the way into the supercharger is obviously going to be far better than 3.5” intake pipe>3”TB(with a butterfly valve)>3.5”SC intake. That is a 36% reduction in the opening.


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[JJI]

The CFM flow rating of intake systems is typically measured at 28" of H2O, which corresponds to 1.01 psi.

Much has been said on this board and others about how much various intakes flow using that standard.

My question is limited to the stock throttle body of the 3.0 TFSI engine and its CFM flow characteristics under that protocol. Has anyone flow bench tested it? I gather that it is 73mm inside diameter and that it is actually smaller than the supercharger intake side, if this is true. How much of a bottleneck is the throttle body? Is it the major bottle neck?

Do we have flow data using this standard protocol on the stock throttle body and what does that data show?

Isnt what your describing pretty much what the APR ultra charger does ?


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[MSq5]

Isnt what your describing pretty much what the APR ultra charger does ?


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Thanks, but my question is different. I appreciate your intent. I was purposefully limiting my question to a search for CFM flow on the stock throttle body only, under standard 28" water column testing protocol. I'm looking for the actual bench flow number in CFM at standard pressure.

That number will inform intake air filter flow, air box design, and throttle body tube size and design for those of us using the stock throttle body for whatever the reason may be.

My inquiry is really directed to the underlying issue of the trend toward larger, sometime gigantic multi-pleated cone air filters in aftermarket kits. The more pleats and more surface area you have for the same type of filter element, should produce a higher flow. But, at some point, if the flow capability of the filter is greater than the ability of the throttle body to pass more air, then that "extra" filter flow is purely a marketing ploy and produces no gain.

Knowing the flow rate of the throttle body seems to be an important factor in consumer education and in product selection. If we have the stock throttle body (perhaps because we are still in warranty or for other reasons) it makes no sense to pay extra for a filter that has a higher flow rate than the throttle body can pass through to the supercharger.

Example: Let us assume the throttle body can pass 600 CFM (I don't know what the number is) using the standard pressure protocol. Let us assume that the supercharger can handle that flow and the intake tract and intake valve size will do so and that you can match fuel demand and optimize AFR.

If the filter and throttle body tube can pass only 500 CFM using that protocol, then the system will benefit from a higher flowing filter.

But, if the filter and/or throttle body tube can flow 1,000 CFM and the upstream system beginning with the throttle body, is restricted to 600 CFM of flow, then you would be wasting money by paying extra for the big filter and tube.

Example 2: You can connect a soda straw to a vacuum source and gradually increase vacuum, sucking through that straw. You will reach a point where the flow through the straw cannot increase. The throttle body corresponds to the soda straw. The supercharger is the vacuum source pulling air through the throttle body.

That's what I am looking for regarding the throttle body -- its standard protocol CFM flow rate.

One exception might be use in a high dirt/dust/sand environment. Then, a very dirty filter capable of 1,000 CFM might still flow 600 CFM. That might be important in specialized conditions, like off road rally racing or desert racing or such. Probably not relevant to 99% of us.

Surly, someone has actually bench flowed the stock throttle body. I'm sure the aftermarket intake manufacturers have, but they are likely to be close-lipped about this.

[Bartlett]

This chart might be slightly helpful:



Assuming stock is 70mm diameter, APRs 28% increase in cross-sectional area produces 80mm diameter.

If the open airbox only supports a CFM of 825, and the ultracharger TB restricts it to 775 vs. 600 for the stock TB, then the CFM increased by 175 over stock. The ultracharger TB still has some room before the open intake CFM is maximized. Maybe 82mm. I guess we just need to know what the SC inlet CFM is to determine what inlet size could be a bottleneck. Assuming one has an inlet pipe the same diameter of the APR one, then they could just use their higher flow filter I believe?

Based on the data, the stock TB pipe CFM must be 600 because the open inlet pipe supports 825, but is restricted to 600 with the stock TB.

[MSq5]

This chart might be slightly helpful:



Assuming stock is 70mm diameter, APRs 28% increase in cross-sectional area produces 80mm diameter.

If the open airbox only supports a CFM of 825, and the ultracharger TB restricts it to 775 vs. 600 for the stock TB, then the CFM increased by 175 over stock. The ultracharger TB still has some room before the open intake CFM is maximized. Maybe 82mm. I guess we just need to know what the SC inlet CFM is to determine what inlet size could be a bottleneck. Assuming one has an inlet pipe the same diameter of the APR one, then they could just use their higher flow filter I believe?

Based on the data, the stock TB pipe CFM must be 600 because the open inlet pipe supports 825, but is restricted to 600 with the stock TB.

Thanks. Your post is helpful. read the chart differently and concluded (perhaps wrongly) that APR was flow testing only the filter, airbox (if present) and throttle body tube. That would be setup on a flow bench, but not including the throttle body, itself. They say nothing about the throttle body, itself, or the flow rate through the stock supercharger.

But, if you are right, you are only going to get 600 CFM to the supercharger regardless of higher flow in the filter, airbox, or the TB tube.

That is my very concern about these higher flowing filters ratings. Do they really matter if the TB restricts flow to a lower CFM?

[Bartlett]

Thanks. Your post is helpful. read the chart differently and concluded (perhaps wrongly) that APR was flow testing only the filter, airbox (if present) and throttle body tube. That would be setup on a flow bench, but not including the throttle body, itself. They say nothing about the throttle body, itself, or the flow rate through the stock supercharger.

But, if you are right, you are only going to get 600 CFM to the supercharger regardless of higher flow in the filter, airbox, or the TB tube.

That is my very concern about these higher flowing filters ratings. Do they really matter if the TB restricts flow to a lower CFM?

Glad I could share some insight! Yeah, sadly they did not test the TBs themselves. I wish there was a tuning company that could share some comprehensive, objective results about what mods will do what.

600 CFM max would be with a stock throttle body and APRs open intake setup. But, 775 CFM is achieved with their throttle body. Are you saying that this actually doesn't matter because the SC only can support 600 CFM?

One thing I wanted to do was add a higher CFM filter to my ECS setup. I don't believe the 5" diameter filters that APR and IE use would fit though. Admittedly, this would probably provide only a few WHP from the marginal CFM gain, if any.

[MSq5]

Glad I could share some insight! Yeah, sadly they did not test the TBs themselves. I wish there was a tuning company that could share some comprehensive, objective results about what mods will do what.

600 CFM max would be with a stock throttle body and APRs open intake setup. But, 775 CFM is achieved with their throttle body. Are you saying that this actually doesn't matter because the SC only can support 600 CFM?

One thing I wanted to do was add a higher CFM filter to my ECS setup. I don't believe the 5" diameter filters that APR and IE use would fit though. Admittedly, this would probably provide only a few WHP from the marginal CFM gain, if any.

What I am saying (or trying to say) is that if the stock throttle body can only flow 600 CFM at standard 28" H20 ( we don't really know) or whatever it turns out to be, then a higher flow filter back downstream is being wasted. I'm suggesting that until we have accurate data on the flow characteristics of the throttle body, it's pure speculation that filters claiming higher flow actually make more power.

That's why I'd love to know the flow of the throttle body. This would greatly assist us in determining whether aftermarket vendor intake systems are going to make more power, or whether the claims are just marketing hype.

[Bartlett]

What I am saying (or trying to say) is that if the stock throttle body can only flow 600 CFM at standard 28" H20 ( we don't really know) or whatever it turns out to be, then a higher flow filter back downstream is being wasted. I'm suggesting that until we have accurate data on the flow characteristics of the throttle body, it's pure speculation that filters claiming higher flow actually make more power.

That's why I'd love to know the flow of the throttle body. This would greatly assist us in determining whether aftermarket vendor intake systems are going to make more power, or whether the claims are just marketing hype.

Yeah, I see what you mean. No point in getting a setup for 900 CFM if the TB bottleneck is 600 CFM. I think the only party that would have this data with interest to share it would be a tuning company that doesn't make hardware.

[cuerna]

Interesting info. Do we know the TB
CFM is 600, or not yet?
I have an intake with a 4 in tube and 4 in afe dry filter. Intake makes supercharger sounds great and don't know how much is this intake producing (CFMs)..is there a way to measure CFMs with a diagnostic tool like obd11 ?