[SC2150]

Originally Posted by axis

Says who?

You do realize that NONE of the ported TB's actually increase the size of the throat. They merely clean up the mouth. The CNC one does make pretty swirls all over the mouth which is suppose to help with throttle response.

The power gains of the VMax patteren ported TB increases the velocity of the flow...thats where the power comes from, not CFM from the blade size. Common misconception in all types of porting. Most hand ported TB's are polished to a high gloss inside the throat, and this causes more disruption of the flow so a loss of power building velocity is the result.:

Re: CNC ported throttle body...

Has been app 9-10 years since Pete developed (we worked in tandem on the project) the first for the LS1 F-body and C5 corvettes, and it took months (we were all hand porting before that with inconsistant results and no real duplicatable power gains except those playing dyno graph games such as test first w/hood closed and heat soaked, then hood open with their version of porting, etc.) and it was a real break-through them. To date it has grown into most GM, some Ford, and working on others now. It takes on average 3 plus months of testing and sacrificing TB's before the final cut & pattern is established. If you cut into the ridge on the bottom, you find flaring and idle issues. If you fill the depressions w/epoxy trying to improve flow then there are driveability issues. You start on a CAD program, but each step must be tested, then document the changes made to that portion of the bore, and the aggressivness and the shape. Then accomidate the thrttle blade shaft as that is a disruption as well.

We tried knife edging the blade, but that affects the off idle transition w/no real gains at WOT. We tried shaving the shaft but that causes mure disruption than leaving it alone (never would have thought that as we did that hand porting for years on the assumption it would help).

And each version of TB and the model of car it is on gives different results. The gen 5 camaro with the LS3 and it has a 90* intake tube only gives 8-12 rwhp if that, yet the corvette w/same motor & TB sees 10-14 plus (some show as much as 16, but not the norm) as it has a pretty straight shot intake tube.

Lots of variables learned in this.

Now, some reading from some of the most respected and knowledgable porting engineers on the planet:

Re: CNC ported throttle body... .

It is not just flow that makes power, you need velocity as well. You can bolt on a 55 gallon drum and get flow beyond anything....but it is how clean that flow is and thats the key to the textured porting and variable pattern.

I will let the testing show, but read this article to understand more:

http://www.popularhotrodding.com/tec...g/viewall.html

----------

This article quotes several of the industries most talented....now most of this is on cylinder heads, but the same principals apply to flow anywhere on the inlet side of an engine.

If your hand ported is highly polished in the bore then that will cause enough disturbance that all things equal in the blade size, the textured TB will make more power.

Darin Morgan is who I trained under:

http://www.chevyhiperformance.com/te...n/viewall.html

Have been doing this for over 38 years and before modern technology showed we were wasting time and COSTING power, we polished all ports after porting. Read this...Rottler recently applied for a patent and this is used in all types of porting, except we still polish the exhaust ports to prevent carbon buildup:

http://www.rottlermfg.com/brochures/...ochure_web.pdf


So much misinformation and misunderstanding on flow & velocity....you can have all the flow you want, but if its disturbed and velocity is lost, so is power.

Summed up pretty good in this paragraph:

CFM and Velocity

Darin Morgan: "Make no mistake, velocity is the primary variable in the design of the entire induction system. I often say that my job title should be Velocity Manager instead of Cylinder Head Designer. Air speed is 10 times more important than raw flow numbers. If you kill the velocity by 10 percent, you will kill almost 40 percent of the wave and ram energy that dynamically fills the cylinder! Raw airflow cfm is an important variable as well; it's just not as important. If you buy a cylinder head that is properly sized for a flow of 400 cfm and your engine is only asking for 350 cfm, you will not only fail to achieve the power potential that the 400 cfm would have given you, you will also fail to reach the power that the 350 cfm would have given you. That's because you killed all the air speed in the induction system. If your engine is asking for 350 cfm and you give it a properly sized cylinder head flowing 350 cfm, your airflow demand is matched and your air speed is matched. You then have a chance of achieving the power potential that 350 cfm can give you.