Polished/Port Intake Discussion

You can only force so much air (in a given amount of time) through a hole. Bigger the hole the faster you can move the required air.
I think in a boosted application.....You will need a larger TB to move the air.
Some KBs are running a 100mm TB.

How baby butt smooth you need the 6.1 Intake to be to move the air is another question.
HHP does minimal porting and smoothing on their intakes (for $750!!) and say it flows plenty well stock. I have one and was amazed at how minimal the porting was, it was not even fully gasket matched (which makes me wonder why the intake runner on the HHP head IS gasket matched).
I think that all the excessive porting and polishing work that is done on some intakes (grinding down of the injector boss for example) is very minmal in gains, it just looks more like you got your money's worth.

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I would agree with that. But you're pushing the same volume of air... cubic inches. Your cylinders did not get any larger when you put the blower on it. Your 6.1L or whatever is still a 6.1L. It moves 6.1L through there every 2 rotations whether it's N/A or F/I. It's just that the 6.1L is compressed air (denser) when F/I.

Same volume but there are more oxygen molecules in that space so you can get more hp with more fuel.

So let's assume the TB is the bottleneck and, N/A, it limits flow to X cfm at 6000 rpm WOT.
Your N/A engine always operates at some vacuum. Even at WOT.
Lets say you want to boost to 8 psi in the manifold at 6000 rpm.
The manifold is past the TB on the way from the blower to the cylinder.
If you measure 8 psi in the manifold at 6000 rpm WOT then it doesn't matter. You're past the TB and you have 8 psi boost -- the TB is not constricting anything.

If you can't get 8 psi boost in the manifold at 6000 rpm WOT *then* you might try a larger TB to see if it's the problem (that would be after trying a different pulley or wastegate setting or larger blower).

If flow is the problem then you will have more vacuum (or less boost) in the manifold.

 

You might be right but I'm not buying it.
If you want 8lbs of boost and you get 8lbs of boost in the manifold then a larger TB isn't going to make any difference. Ok, maybe throttle response might be some fraction of a second faster but I doubt it.

 

Remember the TB is the only "orifice" in the system. To me you will get a pressure drop across it during most full throttle conditions, especially during high boost appplications.
I often wonder why no one has set up a system to see what the pressure drop across the throttle body is, this will tell you flow.


Remember the only way to see a benefit from a bigger TB is at wide open throttle.
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Even if there was, why would you care? If you have the desired boost in the manifold.

 

How do you know you have the desired boost in the manifold at all times?
Where is the sensor located for the vacuum/boost signal to the PCM?
Where do people actually plumb in their vacuum/boost gauges?

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Generally the MAP sensor right?

 

Where does the MAP sensor connect for its presssure reading?
Where do people add their own vacuum/boost gauge sensor?
On the TB intake tube or in the intake manifold?

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That I don't know. I sort of remember Ken's was in the TB intake tube?

 

first, compressing the air increases the iat's......hence the need for the most efficient means of intercooling. this all happend BEFORE the tb.

second - you mention cam and large orifice in the same post.....:bigwink:

my boost gauge is tied into the back of the manifold off of the brake booster line.

not always......

map sensor for centri blowers (considering we are talking about 6.1 style intake manifolds) attaches to the back of the manifold. brake boost vac line is where you tie in for the boost gauge. all of this coming from inside the actual manifold....... beyond the tb.

for me......where as the larger tb will allow a n/a motor to draw more air in quicker with a larger orifice, the f/i motor does not need that because the air is being artificially sped up way more than you will see n/a....... large orifice or not.......

yeah, i just like saying "orifice"....lol

 

According to Wikipidea: "An orifice is any opening, mouth, hole or vent, as of a pipe, plate, or a body."

Notice it doesn't say "oriface."

fthththhtfhththt

 

Dang Jon...any talk about a hole and all you can think of is mouth or body..LOL..

Great discussion here...I have been off line for the last 3 days doing computer upgrades at the office...something I hate..:stars:...anyway the discussion here has helped me with some planning.....would like to see hard evidence like dyno or track....