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Old 12-20-2012, 04:59 AM   #31
Poolside
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Originally Posted by roger 04 rt View Post

--My fuel pressure increase is to improve atomization at the injectors . . .
Here's something of note. Atomization doesn't much change the fuel vaporization rate within the atmosphere of the intake tract. But the increased fuel pressure likely creates a somewhat larger spray pattern, and that would make a difference.

The sequence of events goes sort of like this. Fuel leaves the injector, flies through the air, and lands on the intake tract wall where it begins to vaporize. That waiting-to-vaporize fuel is often referred to as 'port wall fuel'. The 'puddle' of fuel if you will, covers some amount area of the intake tract. The vaporization rate of the 'port wall fuel' is based on the surface conditions of the wall.

After spraying from the injector nozzle, some of the sprayed fuel vaporizes based on the low pressure of the intake manifold. That particular vaporization rate is based on manifold pressure and is not significantly dependent on droplet size.

The remaining bulk of the sprayed fuel vaporizes after coming into contact with the inside walls of the throttle body and intake port. That particular vaporization rate is based on a few things. Manifold pressure continues to be a minor factor in fuel vaporization rate, but there are three other larger factors. 1. The temperature of the inside walls of the throttle body and intake port. 2. The the total area of the injector spray pattern. 3. The velocity of the intake air across the 'port wall fuel puddle'.



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Poolside screwed with this post 12-20-2012 at 05:07 AM Reason: Clarity, if that's even possible :-)
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Old 12-20-2012, 05:33 AM   #32
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Thanks PS, pretty interesting they way that works. The Megasquirt site has a good description of the wall-wetting effect for those with further interest: X-Tau Accel Enrichment. It seemed easier to call it better atomization. I've got some charts that show how the Motronic deals with the wall-wetting lag during WOT that I'll post in the next week.
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Old 12-20-2012, 06:02 AM   #33
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Originally Posted by roger 04 rt View Post

Thanks PS, pretty interesting they way that works. The Megasquirt site has a good description of the wall-wetting effect for those with further interest: X-Tau Accel Enrichment. It seemed easier to call it better atomization. I've got some charts that show how the Motronic deals with the wall-wetting lag during WOT that I'll post in the next week.
Sure thing. Yes that Megasquirt site covers a lot of ground. But you know, it's still the internet, and a good portion of the information is misleading or inaccurate. And moderators delete information that strays from the product-selling line, accuracy notwithstanding.

Maybe something regarding your choice of words? The 'wall-wetting lag' is a phenomenon that happens only when the throttle is in motion. A dynamically changing throttle position is often referred to as 'transient throttle'.

When the throttle is held at a constant, and that can be at any position between idle and wide open, there is no 'wall-wetting lag'. When the throttle is held constant, the fuel entering the puddle from the injector, and leaving the puddle through vaporization, is also constant. And the 'time in the puddle' if you will isn't relevant.



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Old 12-20-2012, 06:09 PM   #34
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Originally Posted by Poolside View Post
Here's something of note. Atomization doesn't much change the fuel vaporization rate within the atmosphere of the intake tract. But the increased fuel pressure likely creates a somewhat larger spray pattern, and that would make a difference.

The sequence of events goes sort of like this. Fuel leaves the injector, flies through the air, and lands on the intake tract wall where it begins to vaporize. That waiting-to-vaporize fuel is often referred to as 'port wall fuel'. The 'puddle' of fuel if you will, covers some amount area of the intake tract. The vaporization rate of the 'port wall fuel' is based on the surface conditions of the wall.

After spraying from the injector nozzle, some of the sprayed fuel vaporizes based on the low pressure of the intake manifold. That particular vaporization rate is based on manifold pressure and is not significantly dependent on droplet size.

The remaining bulk of the sprayed fuel vaporizes after coming into contact with the inside walls of the throttle body and intake port. That particular vaporization rate is based on a few things. Manifold pressure continues to be a minor factor in fuel vaporization rate, but there are three other larger factors. 1. The temperature of the inside walls of the throttle body and intake port. 2. The the total area of the injector spray pattern. 3. The velocity of the intake air across the 'port wall fuel puddle'.


And I therefore assume that the textured wall of the intake runner improves fuel atomization by increasing the wall area and also causes eddys sort of like a dimpled golf ball further improving fuel delivery, or am I all wet here?
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Old 12-20-2012, 08:09 PM   #35
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Originally Posted by Poolside View Post
Sure thing. Yes that Megasquirt site covers a lot of ground. But you know, it's still the internet, and a good portion of the information is misleading or inaccurate. And moderators delete information that strays from the product-selling line, accuracy notwithstanding.

Maybe something regarding your choice of words? The 'wall-wetting lag' is a phenomenon that happens only when the throttle is in motion. A dynamically changing throttle position is often referred to as 'transient throttle'.

When the throttle is held at a constant, and that can be at any position between idle and wide open, there is no 'wall-wetting lag'. When the throttle is held constant, the fuel entering the puddle from the injector, and leaving the puddle through vaporization, is also constant. And the 'time in the puddle' if you will isn't relevant.


Grammar wasn't a strong suit in school. Anyway poolside, I see that you're needed over in aisle 9, some customers looking for IIce Cool and/or IIce Smooth. ... Seriously though, any news on when those shelves will be stocked, a Smooth product could be a winner.

roger 04 rt screwed with this post 12-21-2012 at 04:42 AM
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Old 12-21-2012, 08:08 AM   #36
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Quote:
Originally Posted by Poolside View Post
Here's something of note. Atomization doesn't much change the fuel vaporization rate within the atmosphere of the intake tract. But the increased fuel pressure likely creates a somewhat larger spray pattern, and that would make a difference.

The sequence of events goes sort of like this. Fuel leaves the injector, flies through the air, and lands on the intake tract wall where it begins to vaporize. That waiting-to-vaporize fuel is often referred to as 'port wall fuel'. The 'puddle' of fuel if you will, covers some amount area of the intake tract. The vaporization rate of the 'port wall fuel' is based on the surface conditions of the wall.

After spraying from the injector nozzle, some of the sprayed fuel vaporizes based on the low pressure of the intake manifold. That particular vaporization rate is based on manifold pressure and is not significantly dependent on droplet size.

The remaining bulk of the sprayed fuel vaporizes after coming into contact with the inside walls of the throttle body and intake port. That particular vaporization rate is based on a few things. Manifold pressure continues to be a minor factor in fuel vaporization rate, but there are three other larger factors. 1. The temperature of the inside walls of the throttle body and intake port. 2. The the total area of the injector spray pattern. 3. The velocity of the intake air across the 'port wall fuel puddle'.


I would surmise that manifold pressure plays more than a minor factor. Fuel RVP is a critical factor in fuel quality and combustibility. Low RVP fuels don't do well in piston engines especially those with high CRs.
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Old 12-21-2012, 06:39 PM   #37
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And I therefore assume that the textured wall of the intake runner improves fuel atomization by increasing the wall area and also causes eddys sort of like a dimpled golf ball further improving fuel delivery, or am I all wet here?
Ooops. I may may have misled you by saying "surface conditions". I meant the temperature of the surface and the local air pressure. Regarding the smooth or rough 'surface texture', it's more like you mentioned. The surface would need to be as contoured as the surface of a golf ball to make a significant difference.



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