Injector spray
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From: Overland Park Kansas
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Injector spray
Interesting thought....
Recently, I read that the injector ports on our motors were deliberatetly angled to point at the wall of the head intake runner passage. IOW, instead of pointing say,,,directly down the runner, they're pointed at the wall on purpose.
The reason was to provide add'l atomization of the fuel -- thru the pressure of the gas stream hitting that wall. When I started to visualize this, I pictured the difference between a hard jet of water hitting a wall vs a fine mist. That mental image made me realize there must be a point where too much atomization is detrimental.
If you spray a fine mist on a wall, it won't have the power necessary to bounce of that wall. Most of it will "stick", bead up, and roll down the wall. By contrast, a hard jet will hit hard, bounce, and splatter into much smaller "pellets" of fuel.
Make sense? If so, it makes you wonder about the stream-type of injector vs ones that atomize better. Is one really much better than the other? Could it be that the one we'd expect to be better, might not be? After the gasoline jet hits that runner wall, it needs to rebound and stay in a spray -- mixed with the incoming air. If it "sticks" to the runner wall, it can't mix with the incoming air as effectively.
Recently, I read that the injector ports on our motors were deliberatetly angled to point at the wall of the head intake runner passage. IOW, instead of pointing say,,,directly down the runner, they're pointed at the wall on purpose.
The reason was to provide add'l atomization of the fuel -- thru the pressure of the gas stream hitting that wall. When I started to visualize this, I pictured the difference between a hard jet of water hitting a wall vs a fine mist. That mental image made me realize there must be a point where too much atomization is detrimental.
If you spray a fine mist on a wall, it won't have the power necessary to bounce of that wall. Most of it will "stick", bead up, and roll down the wall. By contrast, a hard jet will hit hard, bounce, and splatter into much smaller "pellets" of fuel.
Make sense? If so, it makes you wonder about the stream-type of injector vs ones that atomize better. Is one really much better than the other? Could it be that the one we'd expect to be better, might not be? After the gasoline jet hits that runner wall, it needs to rebound and stay in a spray -- mixed with the incoming air. If it "sticks" to the runner wall, it can't mix with the incoming air as effectively.
Last edited by GREGGPENN; Feb 10, 2010 at 02:05 PM. Reason: Added 2 more sentences for clarity.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
That info has been out there for some time.
On "batch" or "bank" fire setups fuel just sets in the head for most of the ports until the valve opens and it gets sucked in....so I don't think that too much atomization is really an issue.
On "batch" or "bank" fire setups fuel just sets in the head for most of the ports until the valve opens and it gets sucked in....so I don't think that too much atomization is really an issue.
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
Interesting thought....
Recently, I read that the injector ports on our motors were deliberatetly angled to point at the wall of the head intake runner passage. IOW, instead of pointing say,,,directly down the runner, they're pointed at the wall on purpose.
The reason was to provide add'l atomization of the fuel -- thru the pressure of the gas stream hitting that wall. When I started to visualize this, I pictured the difference between a hard jet of water hitting a wall vs a fine mist. That mental image made me realize there must be a point where too much atomization is detrimental.
If you spray a fine mist on a wall, it won't have the power necessary to bounce of that wall. Most of it will "stick", bead up, and roll down the wall. By contrast, a hard jet will hit hard, bounce, and splatter into much smaller "pellets" of fuel.
Make sense? If so, it makes you wonder about the stream-type of injector vs ones that atomize better. Is one really much better than the other? Could it be that the one we'd expect to be better, might not be? After the gasoline jet hits that runner wall, it needs to rebound and stay in a spray -- mixed with the incoming air. If it "sticks" to the runner wall, it can't mix with the incoming air as effectively.
Recently, I read that the injector ports on our motors were deliberatetly angled to point at the wall of the head intake runner passage. IOW, instead of pointing say,,,directly down the runner, they're pointed at the wall on purpose.
The reason was to provide add'l atomization of the fuel -- thru the pressure of the gas stream hitting that wall. When I started to visualize this, I pictured the difference between a hard jet of water hitting a wall vs a fine mist. That mental image made me realize there must be a point where too much atomization is detrimental.
If you spray a fine mist on a wall, it won't have the power necessary to bounce of that wall. Most of it will "stick", bead up, and roll down the wall. By contrast, a hard jet will hit hard, bounce, and splatter into much smaller "pellets" of fuel.
Make sense? If so, it makes you wonder about the stream-type of injector vs ones that atomize better. Is one really much better than the other? Could it be that the one we'd expect to be better, might not be? After the gasoline jet hits that runner wall, it needs to rebound and stay in a spray -- mixed with the incoming air. If it "sticks" to the runner wall, it can't mix with the incoming air as effectively.
we should make flame throwers
or electronic paint guns
Last edited by FICINJECTORS; Feb 10, 2010 at 03:36 PM.
Race Director
Joined: Jun 2004
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From: WI
This is about wet flow. Around a quarter of the fuel is on the walls until it gets past the intake valve, then it is mainly large droplets. It splats on the cyl wall and spreads. There is a lot of research in this, and it's why some combustion chambers are designed the way they are. AFR did some testing and make Hurricane Chambers. I haven't checked into it for a long time though.
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
This is about wet flow. Around a quarter of the fuel is on the walls until it gets past the intake valve, then it is mainly large droplets. It splats on the cyl wall and spreads. There is a lot of research in this, and it's why some combustion chambers are designed the way they are. AFR did some testing and make Hurricane Chambers. I haven't checked into it for a long time though.
