Why not? Isn't a glass smooth surface exactly what tuners were trying to achieve back in the days of extrude honing heads?
Voodoo Child
- Thread starter Tob
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Why not? Isn't a glass smooth surface exactly what tuners were trying to achieve back in the days of extrude honing heads?
The ridges decrease turbulence. They function similarly to the dimples on a golf ball. That's a very popular comparison to explain how they function.
Like others have stated a "rough" surface will create a turbulent boundary layer that will actually help with flow, and fuel atomization. A golf ball is the most popular way to try to relate to the function. You can also see these items on such things like on Tractor Trailers and air plane wings. Now you can also go too far and cause flow separation which will cause the air to stall.
The air diffusers in this port design I'm sure is for better fuel atomization and vortex control inside the combustion chamber. Trying to position it in such a way that BSFC is closer to being optimized. Positioning the fuel molecules in such a way so the vortex is not positioned directly around the spark plug as large fuel drop lets are hard to ignite and also not to have emissions issue with the fuel droplets falling from suspension. A mixture of both computer modeling and some good ole fashion engine tear down to examine the ash on pistons.
The air diffusers in this port design I'm sure is for better fuel atomization and vortex control inside the combustion chamber. Trying to position it in such a way that BSFC is closer to being optimized. Positioning the fuel molecules in such a way so the vortex is not positioned directly around the spark plug as large fuel drop lets are hard to ignite and also not to have emissions issue with the fuel droplets falling from suspension. A mixture of both computer modeling and some good ole fashion engine tear down to examine the ash on pistons.
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I wanted to take another crack at this question. The car in the clip is the one Jamal was tearing it up with at the powertrain reveal.
http://blog.caranddriver.com/listen-to-the-ford-mustang-shelby-gt350r-revved-in-anger/
Pure ****ing hellfire!
epper:
TOB, One of the best articles I have ever read.................. Thanks for the hard work and your dedication...........................
I wanted to take another crack at this question. The car in the clip is the one Jamal was tearing it up with at the powertrain reveal.
http://blog.caranddriver.com/listen-to-the-ford-mustang-shelby-gt350r-revved-in-anger/
Pure ****ing hellfire!
I absolutely love it. It sounds much better under load though.
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Interesting to note...the Hendrix lyrics quoted above are from Jimi's Voodoo Child (Chile) (Slight Return) which was remarkably a... complete improv. The Return version is the one most Jimi's fans identify with. The original Voodoo Chile song was in fact finely crafted in the studio previously...more a kin to how the Coyote and Voodoo motors came about. Of course, when if comes to serious, heavy metal the Return version is closer to the heart of Ford's new engine.
Don't the stock 5.0 cams form the 2015+ GT Mustang have similar specs to Boss &/or Cobra Jet cams? Not saying they are identical, but I believe I read somewhere that they had similar specs and the TiVCT tuning keeps them tame. That these cams and the newer heads are a big reason the newest 5.0 is making big numbers with just a tune and bolt-ons. Or am I completely off? :-D
I know for sure that at least one of the cam sets has 13mm lift on the 2015 GT, and possibly both intake and exhaust. That's higher lift than the stock Boss, same as the CJ cams. I'm sure the duration isn't as high as the CJ though. Pretty good stock cams nonetheless. That's .512 stock max lift for folks like me. I relate to some things better in SAE still. :/ 14mm is .551 lift. The big gains are in more duration though, not lift.
I have a question about valve sizes. If you have two 38.3mm (1.51") intake valves, is that the same flow as having a single 76.6mm (3.02") intake valve on a two valve motor, or is there a different formula for two valves versus one valve flow?
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You typically compare valves by area, not diameter. Shrouding could throw it all off though.
It's not all about valve sizes. Shrouding plays a roll as SID mentioned. Smaller diameter ports will have higher fluid velocities. Shape of the ports can have an affect. Whether the port walls are smooth or if they are rough to get the "golf ball effect." Two valves is supposed to also help with how the air/fuel mixes in the combustion chamber itself as well compared to one.
I'm sure someone more versed in fluid dynamics can chime in too.
It is clearly explained in the post. They are air cooling the pipes to keep the heat from melting the valence. Think of the external rings as a heat shield only shiny since you get to see it.
Correct, a single 3" diameter valve would actually have 4x the open area of 2x 1.5" diameter valves, so the velocities and flow regime would be very different. But yes, the valve shroud as well as the lift matters as well since that will dictate final hydraulic diameter.
You guys had me going back to a statement that Adam made in an earlier response.
I used Boss valve sizes (37mm/31.8mm) and calculated the area for each valve size for the 5.0 and used Adam's numbers for the 5.2 engine. If the flow increase is indeed "proportional to the valve area increase" then I came up with 7.15% for the intake and 7.03% for the exhaust. I've found flow numbers for the standard Coyote head but not for the Boss head. Anyone have them? Here's the stock, non-Boss numbers I found...
Unfamiliar with discharge coefficient I found it to be "the measure of how efficient a given area is in regards to volume flow verses area, divided by a theoretical maximum." It'd be nice to have all the numbers to plug into a calculator such as this.
AC said:
I used Boss valve sizes (37mm/31.8mm) and calculated the area for each valve size for the 5.0 and used Adam's numbers for the 5.2 engine. If the flow increase is indeed "proportional to the valve area increase" then I came up with 7.15% for the intake and 7.03% for the exhaust. I've found flow numbers for the standard Coyote head but not for the Boss head. Anyone have them? Here's the stock, non-Boss numbers I found...
Unfamiliar with discharge coefficient I found it to be "the measure of how efficient a given area is in regards to volume flow verses area, divided by a theoretical maximum." It'd be nice to have all the numbers to plug into a calculator such as this.
Area of the valves! That was way too simple. I feel dumb.
Livernois has mentioned the stock Boss numbers somewhere before. I have no idea where to find them though.
Livernois has mentioned the stock Boss numbers somewhere before. I have no idea where to find them though.
Is it OK to say that ****ing thing sounds ****ing rambunctious!? or will the board mods get upset with the language
Edited by Staff
Now what do you think?
Edited by Staff
Now what do you think?
All I can find on Boss head flow is something stating 4-6% increase on intake flow and 10% increase on exhaust flow versus 11-14 Coyote heads. If that's accurate, flow @ .50 would be 301-306.8 intake, 221.5 exhaust.
Voodoo may flow somewhere around 322.5-328.7 and 237.1 @ .50 lift.
Voodoo may flow somewhere around 322.5-328.7 and 237.1 @ .50 lift.
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Next time I'm at Bischoff's I'll get my stock flow numbers for the heads. But there are lots of things that can be manipulated to give better CFM numbers. Just like dyno's CFM readings are just for data collection and comparison for changes. CFM is only part of the story. You can actually have a cylinder head that is down on CFM then another head but kill it on the engine dyno.
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