Lets Talk Intake Pipe & Air Flow

final5-0 · Sep 6, 2006

I'm gonna paste a sentence Adam put up in another thread where tb size was being talked about. I didn't wanna hijack that thread.

Here is Adam's statement:

To put this into context: 70mm = 2.756 inches. 75mm = 2.953 inches

Here is my Q or topic of discussion if you will ...............

I made a statement on another site saying I did not believe the typical na 302-306 combos seen on these boards needed a cai pipe of 4" id.

If one was forced ... then yes ... a larger id would be needed

anyway ..............

I somehow felt they believed my home made cai of 3" id was not acceptable as nobody else said anything and the thread kinda died off

After seeing Adam post up a 70mm tb is 2.75" id and a 75mm is right at 3.00"id it kinda made me say hummmmmmm

Here is something else that may give some kind of reference.

I know the id of my ProM 80 is very close to being the same id of the pvc pipe I used to make my cai.

My interest is not focused on tb size and I just used Adams statement to kinda set a reference point here in this thread
but
tb size is not something that should be ignored ... for sure

Thoughts ... comments ... or just in general ...................

Tell me what you think ... or know ... about the path of air flow from filter to intake opening

My mind is open here & I look forward to what ya'll got to say

Grady

WHITE94COBRA · Sep 6, 2006

I'm not sure exactly what your asking but it looks like everyone kinda does the same thing in regards to maf, intake pipe and tb. The method seems to be 80mm maf, 3" pipe and 65 70 or 75 mm TB. This puzzled me as well, if the math is correct arent we seeing more incomming air through the maf, then squeezing it into a 3" pipe, and then squeezing it again through the TB? I did mine a little different, I went with the 85mm maf, into the andersons powerpipe which is 3 1/2 or 4", into a 70mm TB; reason being i wanted the tb to be the squeeze point. This is not proven to do anything yet, just my methodology.

VibrantRedGT · Sep 6, 2006

I think we focus too much on MAF and TB sizes. With that said a power pipe is essential for both the MAF and TB. Back in the day I dynoed tested (4) CAI's. The one with the most bends (MAC Kit) made the worst numbers. The one with the least bends made more power (3 Inch PVC). When we trimmed a few inches off the straight shot one it picked up 1.7HP. All tests were done with a Pro-M 75MM MAF and BBK 65MM TB. Conclusion-rerouting air makes less HP. No need to be a genius to figure that one. Fact- 3 or 4 inch straight shot will make more HP period.

Next, the MAF will on take in so much air. However the TB helps pull that air. My take on this is go overkill. A 77 or 80MM MAF and 70 or 75MM TB, no less. So you have a stock intake? Well it doesn't matter if you add the overkill combo, the intake can only handle so much air. Buy it once, go big and don't worry about it.

final5-0 · Sep 6, 2006

VibrantRedGT said:
The one with the most bends (MAC Kit) made the worst numbers. The one with the least bends made more power (3 Inch PVC). When we trimmed a few inches off the straight shot one it picked up 1.7HP.

OK Vibe

At one time, I also had hard data that showed that to be true.

It got lost on a different laptop

never the less ... like you said ... obvious

Grady

final5-0 · Sep 6, 2006

WHITE94COBRA said:
I'm not sure exactly what your asking but it looks like everyone kinda does the same thing in regards to maf, intake pipe and tb. The method seems to be 80mm maf, 3" pipe and 65 70 or 75 mm TB. This puzzled me as well, if the math is correct arent we seeing more incomming air through the maf, then squeezing it into a 3" pipe, and then squeezing it again through the TB? I did mine a little different, I went with the 85mm maf, into the andersons powerpipe which is 3 1/2 or 4", into a 70mm TB; reason being i wanted the tb to be the squeeze point. This is not proven to do anything yet, just my methodology.

You did just as I had hoped for

You got involved in this discussion

I see your point about how the tb is the smallest opening

Glad you posted

Grady

WHITE94COBRA · Sep 6, 2006

Not trying to hijack, but isnt that kinda the same thing i'm doing with mine? everything up to the TB is bigger than the tb size, also with the powerpipe it has a couple bends, however they are completly rounded and perfectly smooth, i'm assuming this is much better than the mac, bbk, or homemade pvc with elbows, since they have sharp corners and joining pieces.

Now the internet myth (I know you love these grady) is that too big a maf, intake pipe, and TB will cause the car to lose power, or better yet lose throttle response? Im my experience with a few different TB sizes, (same maf and pipe) my car did seem slower.. Now before anyone gets into the TB debate this was completly UNTUNED, My best numbers tuned came from the 75mm unit, my best drivability came from the 70mm. But it was the exact same maf and pipe.

Pokageek · Sep 6, 2006

I am getting rid of my mac cai because of Grady's advice cause I think he is correct.

*I have a 90mm lightening maf because it was a good price and I wanted to stay factory->that goes into a 4" pipe..because it has to-->then a 75mm PP TB->75mm elbow->75mm track heat intake.*

We'll see the diference between that and the old set up soon.

WHITE94COBRA · Sep 6, 2006

Interested to see what you find with this...

Pokageek said:
I am getting rid of my mac cai because of Grady's advice cause I think he is correct.

*I have a 90mm lightening maf because it was a good price and I wanted to stay factory->that goes into a 4" pipe..because it has to-->then a 75mm PP TB->75mm elbow->75mm track heat intake.*

We'll see the diference between that and the old set up soon.

final5-0 · Sep 6, 2006

WHITE94COBRA said:
Not trying to hijack, but isnt that kinda the same thing i'm doing with mine? everything up to the TB is bigger than the tb size, also with the powerpipe it has a couple bends, however they are completly rounded and perfectly smooth, i'm assuming this is much better than the mac, bbk, or homemade pvc with elbows, since they have sharp corners and joining pieces.

Now the internet myth (I know you love these grady) is that too big a maf, intake pipe, and TB will cause the car to lose power, or better yet lose throttle response? Im my experience with a few different TB sizes, (same maf and pipe) my car did seem slower.. Now before anyone gets into the TB debate this was completly UNTUNED, My best numbers tuned came from the 75mm unit, my best drivability came from the 70mm. But it was the exact same maf and pipe.

First of all ... I was trying to show that I saw how you did indeed use your tb's smallest opening as the ... your words ... squeeze point

No hijack on your part as I see it

Again ... you are involved in the discussion

I agree with your assumption about smooth bends

Did some flow testing several years ago

Ever seen that convoluted pipe the factory uses
Don't flow all that good
If one was used for a bend ... it would be all the worse

I do have an open mind about tb size
but
I think this part is mostly true .............
Larger should make more peak or high rpm power

Where I am not certain is the part about low to mid range

A thread is now on Corral where this guy says to look at the mag tests to compare
Quite Honestly ... Never done it myself so ... there you have it

Does larger hurt and if so ... is the trade off worth it

I'm so gald you posted your thoughts based from your findings about runnin different size tb's

Grady

WHITE94COBRA · Sep 6, 2006

"Does larger hurt and if so ... is the trade off worth it."

I would think this trade off is worth it if all you were looking for is peak power. For me personally, not so much.

"First of all ... I was trying to show that I saw how you did indeed use your tb's smallest opening as the ... your words ... squeeze point"

I was posting at the same time as you were so I didnt get to read this before My post. Sorry bout that.:SNSign: The best way for me to describe the way I was thinking was saying squeeze point. Should of said restriction point, you can me if you want. This should turn into a very interesting discussion as some of the guru's of flow get in here (tmoss, grnlx).

bimmertech · Sep 6, 2006

least bends is obviously more desireable.

however a theory i heard that makes sense is that you want a funnelling effect to the throttle body. this is "supposed" to increase air pressure as it gets smaller. the end of the pipe in this theory would be the same size as the throttle body.

for instance: conical air filter with a 4.5" opening attached directly to a 4.25" maf that leads to a 4" inlet tube that connects to a 3.75" throttle body.(numbers are for demonstrational purposes only)

i can't say that i agree with that theory, but i sure don't disagree with it.

just my .02

Black95GTS · Sep 6, 2006

final5-0 said:
I'm gonna paste a sentence Adam put up in another thread where tb size was being talked about. I didn't wanna hijack that thread.

Here is Adam's statement:

To put this into context: 70mm = 2.756 inches. 75mm = 2.953 inches

Someone actually listens to what I say!

My thoughts on this come from a fluid dynamics course I took at school. If you do some researching on Bernoulli's laws, you'll find that, in layman's terms, for ideal flow of a fluid through a pipe (air is a fluid!!) you don't want to change the mass of the fluid from one end to the other. IE, don't force it around bends or change the diameter of the pipe.

Did you know... that if you take a fluid through a pipe and force it into a smaller pipe, the fluids velocity INCREASES but the pressure actually DECREASES! So here is where I think the "velocity" argument of the smaller throttle body is total internet BUNK. Who cares about velocity, you want to increase the pressure in the air intake track. Thats what superchargers and turbochargers do!

And because in a NA engine you don't have any means of artificially pressurizing the air intake, then damnit, stick as big a pipe as the intake will allow on there and go to town. Whether or not you might have to work a smidgeon harder on the tune is another thing, but there is no doubt in my mind that matching the throttle body to the intake will undoubtedly increase power.

Ideally, your air inlet will be as straight as possible with the same size pipe for the entire length.

Adam

WhiteDevil · Sep 6, 2006

VibrantRedGT said:
So you have a stock intake? Well it doesn't matter if you add the overkill combo, the intake can only handle so much air. Buy it once, go big and don't worry about it.

I like that response alot. Thats what i always think. I wish i would have known that back when i first started on this stang. But now i always tell people that.

final5-0 · Sep 6, 2006

We all have talked a bit here and there about this stuff in various threads.

I did think it would be interesting to start a discussion where the complete path from filter to intake could be considered.

One thing I remember from several of those threads that most peeps seemed to agree upon was .............

I'll go ahead and be the bad example here

I got an Edel elbow which is only 70mm

If I had a 75mm tb and opened up my RPM opening to 75mm
the smaller 70mm elbow would make the larger tb & intake opening a moot point

Or put another way

The elbow would be a greater restriction than the tb/intake opening.

btw ... that seems to make sense to me

Grady

tjh566 · Sep 6, 2006

All this talk but lets face it on the stock 302 block and internals, maybe with an HCI, Any Intake is gonna add horsepower but the differences between the designs, the number of bends, and length is only gonna net like 2-5hp Crank Max.

frcefedlx · Sep 6, 2006

Just a thought here but wouldn't the gradually tapering down of the inlet tract help to build velocity in the air coming in and stacking up (not much) in the intake plenum so when the intake valve opens that air rushes in for a better cylinder fill. I believe I read something about how that idea aided in creating the stock intake and plenum with the longer runners aiding in torque and shorter runners giving more power up top with a small decrease in low end torque. I would think that giving up some of that velocity in the intake tract with a larger throttle body would sacrifice a small part of low rpm torque production. I would think it more of a trade off, low end torqu or top end horsepower. But there has to be a certain amount of truth to "bigger is not always better".

WHITE94COBRA · Sep 6, 2006

That's exactly what bimmertech was sayin in his thread. The way it was explained look's and sounds right (in theory). Once again I have nothing to back it up with.

BlackVert · Sep 6, 2006

it seems to me that the velocity of the air when it hits the valves is important since the valves are open for such a short period of time. the faster the air is moving when the valve opens, the more air will be able to get into the cylinder.

it also seems to me that the pressure will always be lower on the intake side of the throttle plate, unless the throttle is wide open.

in the case where the fluid is forced through the opening, it makes sense that the pressure is higher on one side and the velocity is higher on the other side. the temp is lower too. but i'm not sure i see how that affects things in a non-forced environment.

obviously, the throttle plate is the device that controls how much air gets through more than anything else. so it seems to me that the goal would be to provide the throttle as much "calm" (i.e.-non turbulent) air as possible so that when the air is allowed through, it can go as smoothly as possible to the cylinders.

when the throttle is wide open, we also want it to be able to provide the engine with as much air as it wants.

so the question for me is: does a funnel-like intake track provide less turbulent air to the throttle than does a uniform diameter intake track?

yellow1995Cobra · Sep 6, 2006

I think Adam ended this discusion.. Good write up.

bimmertech · Sep 6, 2006

frcefedlx said:
Just a thought here but wouldn't the gradually tapering down of the inlet tract help to build velocity in the air coming in and stacking up (not much) in the intake plenum so when the intake valve opens that air rushes in for a better cylinder fill. I believe I read something about how that idea aided in creating the stock intake and plenum with the longer runners aiding in torque and shorter runners giving more power up top with a small decrease in low end torque. I would think that giving up some of that velocity in the intake tract with a larger throttle body would sacrifice a small part of low rpm torque production. I would think it more of a trade off, low end torqu or top end horsepower. But there has to be a certain amount of truth to "bigger is not always better".

what you are reffering to has nothing to do with pre throttle body air flow. you are describing wave tuning.

if huge and straight was good then a throttle body with an air filter directly attached to it would be best, right?(eliminating all variables)

i say we all quit arguing and go buy tornadoes.

Lets Talk Intake Pipe & Air Flow

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