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Thread: Injector End Angle Worksheet

  1. #21

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    Gosh, that is a monster cam!

    I have been trying to understand Injector End Angle (IEA) and can't figure what the rules of the game are for cams with significant valve overlap. I suspect a lot of the information about IEA out there is based on stockish cams with small valve overlap, and those guidelines don't seem to care much when the exhaust valve is open. However, I think us guys with larger overlap do need to pay attention to fueling during the overlap, because a lot of fuel can be drawn out the exhaust at lower engine speed resulting in inconsistent fueling of the engine.

    I notice my engine likes fuel to be injected onto the back of the intake valve at idle, around -180° IEA. At high RPM I have it around -150°, so that the last of the fuel reaches the cylinder at intake centerline (no proven reason, it is just what I did). The problem is I'm not sure how to transition from -180 at idle to low & moderate RPM driving. Seems like I should avoid injection in the region of valve overlap event at low engine speeds, which is a pretty large jump in IEA. This is why I would love to see an example from an old pro that uses a larger cam. *Hint Hint S2H* A good example is worth more than a thousand words.
    Last edited by Qwktrip; 09-27-2016 at 11:47 PM.

  2. #22
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    Quote Originally Posted by Qwktrip View Post
    Gosh, that is a monster cam! I have been trying to understand Injector End Angle (IEA) and can't figure what the rules of the game are for cams with significant valve overlap. I suspect a lot of the information about IEA out there is based on stockish cams with small valve overlap, and those guidelines don't seem to care much when the exhaust valve is open. However, I think us guys with larger overlap do need to pay attention to fueling during the overlap, because a lot of fuel can be drawn out the exhaust at lower engine speed resulting in inconsistent fueling of the engine.
    The amount of fuel burned is what is measured by the WBO2, not the amount of fuel injected.
    So if some of it gets blown out the exhaust port, it just means that not all of what is injected gets burned, and the computer will add more fuel to compensate.
    It doesn't matter if 10% or 80% of your fuel gets blown out the exhaust. The WBO2 doesn't care about unburnt fuel.
    So it doesn't make a difference in actual fueling, it only makes a difference in the smell out the exhaust.

    I notice my engine likes fuel to be injected onto the back of the intake valve at idle, around -180° IEA. At high RPM I have it around -150°, so that the last of the fuel reaches the cylinder at intake centerline (no proven reason, it is just what I did). The problem is I'm not sure how to transition from -180 at idle to low & moderate RPM driving. Seems like I should avoid injection in the region of valve overlap event at low engine speeds, which is a pretty large jump in IEA. This is why I would love to see an example from an old pro that uses a larger cam. *Hint Hint S2H* A good example is worth more than a thousand words.
    Very largely Injector Dependent. An injector that atomizes better won't care where you inject it. So you can inject later to allow all fuel to get into the cylinder while atomized. An injector that sprays like a pencil, doesn't atomize as well, so it needs to be sprayed in a way that allows the fuel to turn to vapor easier. Meaning you use the heat of the back of the valve to boil it into vapor before it gets sucked into the engine.

    At idle, it actually has time to do this. Once you get moving, as RPM & injector duty cycle goes up, it doesn't have enough time to turn the fuel to vapor. But the airflow helps atomize the fuel anyways, so it doesn't need to be sprayed on the back of the valve any more. The key is to find that tipping point on your injectors, which is not always a simple thing to do as every injector and every engine is different.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  3. #23

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    I had some pretty bad bucking today at specific RPM on deceleration & light throttle. Traced it back to Injector End Angle where I had a 90° transition. Looks like I don't have any choice, but to more slowly blend the IEA across the RPM band.

    That means if I want to keep idle at -180°, then my entire IEA table is going to be fairly large numbers (-180° to -150°). The other option is to put idle around -80° (after exhaust closes), and then blend up to -150° at higher RPM. I guess I'll try both and see what the car feels like.

    Earlier this week I drove with IEA at -80° across the board and it seemed to work fine. Although, not sure I could tell the difference from 0° across the board, which is the way my engine was tuned at a local shop.
    Last edited by Qwktrip; 09-29-2016 at 01:04 AM.

  4. #24
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    Quote Originally Posted by Qwktrip View Post
    Looks like I don't have any choice, but to more slowly blend the IEA across the RPM band.
    I didn't know there was another option. See post #17. Why wouldn't you blend significant
    Injector End Table transitions (if they exist)? View your Injector End Angle Table "Graph".

    That means if I want to keep idle at -180°, then my entire IEA table is going to be fairly large numbers (-180° to -150°).
    Why would your Injector End Angle values be −150° at maximum RPM?
    Following your camshaft specs and the directions in the IEA LINK, it's −61.6°.

    The other option is to put idle around -80° (after exhaust closes), and then blend up to -150° at higher RPM.
    My Injector End Angle Table starts at −120° idle (LINK), and ends at −55° WOT.

    Earlier this week I drove with IEA at -80° across the board and it seemed to work fine.
    Although, not sure I could tell the difference from 0° across the board, which is the way my engine was tuned at a local shop.
    Well that should tell you something, as opposed to the engine "bucking" with increased negative values (numerically higher).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #25
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    I'll try experimenting with this RPM & MAP kPa based Injector End Angle Table theory.
    Of course, I can't guarantee it's optimum, but it's at least a good safe starting point.
    A dynamometer is the only way to determine an optimum IEA value at cruise or WOT.
    The Base Fuel Table & Acceleration Enrichment must be well tuned before tuning Injector End Angle.

    Also, ensure the Base Fuel Table is smooth by viewing & blending the Fuel Graph. It's very important to have a smooth Fuel Graph.
    One aspect of viewing the Fuel Graph: It's better to zoom in, by highlighting segments of the Base Fuel Table (left click & drag), and click "Graph".
    This method offers much greater detail. Looking at the entire "Fuel Graph" will almost always look smooth, because it's not as magnified.
    TIP: When the Fuel Graph is smooth, click "Conversion" (VE% Conversion mode) and continue smoothing the general contour of the VE Fuel Graph.

    1) In the 16x16 Injector End Angle Table, enter your modified IEA
    ....idle value (LINK) in the top left corner cell (e.g. −190° or −130°).
    2) Enter this same negative IEA idle value in the bottom left corner cell.
    ....This same idle value can also be used in every cell of the first three RPM columns.
    3) In the top right corner cell (WOT), enter the value from the IEA thread (LINK)
    ....(e.g. −50° or −60°), or a value near your intake lobe centerline (ICL). *
    4) In the bottom right corner cell, enter −100° or the value from "Recalculate".
    ....You can also try entering the IEA idle value in this bottom right corner cell. *
    5) Now highlight (left click & drag) the entire table, or from the 3rd RPM column on,
    ....then right click & select "Fill Selected Values".
    6) Click "Save" (top Toolbar), and cycle the ignition key off-on.
    ....Drive the vehicle, and let us know if the engine feels better.
    * This means you'll have to try it both ways, to see which is better.

    See my successful Injector End Angle Table test results in post #41.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  6. #26

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    Quote Originally Posted by Danny Cabral View Post
    Why would your Injector End Angle values be −150° at maximum RPM?
    Because I'm under the impression that the fuel mixes better during intake valve opening (a moment of high turbulence), and at intake centerline (high velocity). The -150° is about where IEA needs to be for all the fuel to reach the cylinder at intake centerline. Why do you choose to draw in fuel as late as piston BDC? Is there an advantage?

    Following your camshaft specs and the directions in the IEA LINK, it's −61.6°.
    I did use the ideas from that example, but didn't time everything to BDC. I think the only reason he used BDC as a reference point, is to make the example easy to understand. I don't think the intention was for people to actually do it that way.
    Last edited by Qwktrip; 09-29-2016 at 09:29 AM.

  7. #27
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    Quote Originally Posted by Qwktrip View Post
    Because I'm under the impression that the fuel mixes better during intake valve opening (a moment of high turbulence), and at intake centerline (high velocity). The -150° is about where IEA needs to be for all the fuel to reach the cylinder at intake centerline. Why do you choose to draw in fuel as late as piston BDC? Is there an advantage?
    Because airflow velocity is near its highest in the middle of piston travel. And when you have good atomization, you need it to start injecting after the valve is opening and not puddle up on the back of the valve. So the later you can inject and still get it all inside the cylinder, the better it will be for power. It's a very complex dance that you will only understand if you do actual fluid dynamics plotting of an internal combustion engine.

    I did use the ideas from that example, but didn't time everything to BDC. I think the only reason he used BDC as a reference point, is to make the example easy to understand. I don't think the intention was for people to actually do it that way.
    Actually, the intention was to do it that way, but to also provide an easy reference point as well, so that people could adjust as their engine may need something different. The thing to remember...is EVERY ENGINE IS DIFFERENT. And every Driver is different as well. Your driving style and my driving style may require very different fueling, and very different Injector End Angle placement as well.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  8. #28
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    Quote Originally Posted by Qwktrip View Post
    The -150° is about where IEA needs to be for all the fuel to reach the cylinder at intake centerline.
    Your (intake valve open BTDC/close ABDC) camshaft specs are within 10° of mine.
    At −150° Injector End Angle, you're injecting fuel during the overlap period (unless you have very large fuel injectors).

    The IEA Phasing Table is a 16x16 table that dictates when the fuel injector closing event occurs.
    All Injector End Angle values are referenced from BDC (Bottom Dead Center) of the intake stroke.
    A zero degree value indicates the fuel injection event will end at BDC of the intake stroke.
    A positive degree value indicates the fuel injection event will end after BDC of the intake stroke.
    A negative degree value indicates the fuel injection event will end before BDC of the intake stroke.
    Why do you choose to draw in fuel as late as piston BDC? Is there an advantage?
    My Injector End Angle Table isn't at 0.0° at maximum RPM. It's at −55° WOT IEA.

    I did use the ideas from that example, but didn't time everything to BDC.
    The end resulting values are not at BDC (Bottom Dead Center of intake stroke).

    I think the only reason he used BDC as a reference point, is to make the example easy to understand. I don't think the intention was for people to actually do it that way.
    Yes, Scott already answered this above. And my −55° WOT IEA value ends the fuel injection event near the center of the intake stroke.
    Open the Holley EFI software & "Help" Contents (top Toolbar), and read the "Injector Phasing Instructions". Look at the camshaft intake/exhaust valve timing graph.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  9. #29

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    Quote Originally Posted by S2H View Post
    Because airflow velocity is near its highest in the middle of piston travel. And when you have good atomization, you need it to start injecting after the valve is opening and not puddle up on the back of the valve. So the later you can inject and still get it all inside the cylinder, the better it will be for power.
    Good explanation. Thank you. My engine appears to respond well to -180 IEA at idle, maybe more. At some higher RPM, I have to get that IEA angle moved over to much smaller values. Rule of thumb, by what engine speed should I complete the transition? My engine is full strength by 3000 RPM and carries the same torque out to 7000 RPM. I'd say my power band begins around 2500 RPM. Do you think it would be wise to finish the transition before 2500 RPM? Just trying to establish some fences around my neighborhood, so that I don't spend time on the wrong ideas.

  10. #30
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    So I'm a bit slow, but I've been putting a lot of thought into this, while following along on a degree wheel trying to grasp the concept. With my cam, -170° is injecting fuel during overlap. That could be a contributing factor as to why I ran out of gas yesterday. I've moved my idle IEA to -110°, and blended from there. Am I on the right track?
    '81 Mustang Cobra/LSX powerplant
    Poorly built ERL LS454 rebuilt by Extreme Racing Engines
    1.27 60', 9.14@150.47

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