Injector End Angle Worksheet

[Danny Cabral]

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.

Good idea, you're not as slow as you think.

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?

Yes, you're on the right track. This is what post #28 is all about.

[Qwktrip]

Now wait a minute... This is the exact same thing I asked about earlier, but I got a different answer in post #22.

S2H told me to not worry about valve overlap, and just tune it for the amount of fuel the engine wants. And he also advised that the LS type engine has a narrow injector spray pattern with poor atomization at low engine speed, so it is customary to spray on the back of the intake valve to promote atomization at low engine speeds.

[Danny Cabral]

S2H told me to not worry about valve overlap, and just tune it for the amount of fuel the engine wants.

Correct, if it doesn't want (like) it during the overlap period, don't inject it there. If it likes it there, don't worry about it.

And he also advised that the LS type engine has a narrow injector spray pattern with poor atomization at low engine speed, so it is customary to spray on the back of the intake valve to promote atomization at low engine speeds.

Yep, it all refers back to this IEA at idle post: LINK.

[Qwktrip]

Yeah, my engine is definitely responding well at idle to a very early injection event. I just need to get the rest of the table sorted and then I'll be out of your hair. LOL!

Frankly, my engine runs fine if the whole IEA table is after the overlap period, and I have large enough injectors to do it. Heck, it even runs fine at 0° IEA, which is what it was after the last dyno tune. But I keep hearing it can be better, and that's why I keep driving at this. Thanks for your patience.

[S2H]

Now wait a minute... This is the exact same thing I asked about earlier, but I got a different answer in post #22.

S2H told me to not worry about valve overlap, and just tune it for the amount of fuel the engine wants. And he also advised that the LS type engine has a narrow injector spray pattern with poor atomization at low engine speed, so it is customary to spray on the back of the intake valve to promote atomization at low engine speeds.

It's very dependent on the injector used. But stock LS injectors do tend to not be the greatest for atomization at idle.
And part of the reason OEMs spray the back of the valve is for emissions, and sometimes for no other reasons.

Spraying the back of the valve is not to promote atomization (it does very much the opposite...it puddles).
It's to allow it to turn into a vapor more easily as the heat from the valve will partially boil the fuel into a vapor.

[Qwktrip]

I wanted to estimate at what engine speed I can no longer fit the start of injection inside the intake valve event. That appears to be about 4000 RPM for my setup. Maybe you can check my logic.

1. I let the Holley auto-calculate function fill the IEA Table using my Base Fuel Table. I know what position Holley is using for intake centerline, and I know they are centering the fuel pulse on the intake centerline. So I can use that table of data to calculate the duration of the fuel pulse in terms of crank duration.

2. Then I did the auto-calculate again, but with zero fuel in the tables, like the example from S2H. That table ends up being how long it takes for fuel to reach the cylinder at BDC, and it sets a boundary for how far advanced I can place the IEA.

3. Add up the results from Step 1 & 2, and I have the total duration from start of injection until the last of the fuel reaches the cylinder at BDC. Once that value is over about 190°, then I know the start of injection is going to begin before the intake valve opens. That is about 4000 RPM in my case.

What I'm trying to do is break down this IEA Table into smaller bits, so I can work on smaller problems one at a time until I'm done. I can follow S2H's script from 4000 RPM to redline. Then I work on the lower part of my power band between 2500 - 4000 RPM (again, probably not too difficult). And last, figure out how to transition from idle to 2500 RPM (probably the most difficult).

Sorry, I'm just thinking out loud because it helps when you guys catch my mistakes. Thanks.

[Qwktrip]

I tried this IEA Table and car seemed to drive OK. I used S2H's method above 4000 RPM to advance the IEA as far as possible. Below 4000 RPM, I can fit the injection pulse inside the intake valve event so I kept moving the IEA so that the fuel delivery was centered on the intake stroke. At idle, I'm using -180° IEA because the engine likes it, and then blended that into the table by 2250 RPM.

I have a 33° delta from cell to cell when blending from idle. Not sure how much is too much. I know a 90° delta caused a lot of bucking and the IEA angle was very jumpy in the datalog. I might still have a slight stutter off-idle at light throttle, but the IEA doesn't look jumpy at all in the datalog. Need to dig a little bit why the stutter.

[Danny Cabral]

It's funny you posted in this thread again. I just reevaluated my Injector End Angle Table, and had a lot of success this morning. (Driving to & from church was my road test.) I'll post a detailed update when I have more time, but it involves better throttle response off-idle and at cruising speeds.

[Qwktrip]

I look forward to seeing it. Thank you.

[SSSTANG]

I played with mine today too. Let me know if I need to start another thread. This is the IEA Table I was using today:

After a short 10 mile drive, the engine was smooth & driveability was good. I didn't record a datalog but with Base Fuel Learn Gain at 50%
the ECU added fuel. I don't know why the fuel was added, and I don't know that's a good thing or not. Any explanation would be appreciated.

[Danny Cabral]

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.

I'll post a detailed update when I have more time, but it involves better throttle response off-idle and at cruising speeds.

UPDATE: I basically configured my Injector End Angle (IEA) Table as I outlined in post #25. However, I lowered my idle IEA to 100°. I did this in order to fit the idle and cruise injection events between the valve overlap period (LINK), and the intake centerline (ICL) when valve lift & airflow is the greatest. (Earlier this year, I installed larger fuel injectors to help accomplish this.) My engine doesn't respond as well if I inject idle fuel before the valve overlap period, and the idle smells worse. Also, lowering the idle IEA Table values to 100°, minimized the following off-idle & cruise cell column transitions. This alone, eliminated a very slight off-idle hesitation that I thought was due to my very lean Target A/F Ratio Table in that area. My WOT IEA value at maximum RPM is 50°, because I wanted to finish the injection event just past the ICL point (evacuate the intake port clean). This is close to S2H's IEA Table calculation (LINK). Lastly, I entered 100° again in the bottom right corner cell. Because like idle, the injection events are shorter (less lb/hr Base Fuel Table values) toward this region, so the injection event can happen sooner. (I also wanted to try a MAP kPa based IEA Table.) I use the same idle value in every cell of the first three RPM columns. So I highlighted (left click & drag) from the 3rd RPM column to the last column, and right clicked & selected "Fill Selected Values". This is working very well for me. Incidentally, my IEA "Graph" now resembles the contour of my Fuel Graph (Fuel ICF). Maybe this is an additional benefit. I ended up not using S2H's IEA Table calculation, but it did serve me well prior to this change. It's extremely helpful to have your camshaft's valve timing events graph (LINK) on hand, to visualize where the IEA events are happening.

[SSSTANG]

Your reasoning makes sense Danny, I will try this method next. Have you seen any fuel added or subtracted? Should I turn "Learn" off completely?

[Danny Cabral]

Have you seen any fuel added or subtracted?

Nothing significant, the Learn Table is within +/- 3%. (I Transferred Learning To Base and blended the Fuel Graph before testing.)

Should I turn "Learn" off completely?

I personally never turn it off completely; I decrease the Learned Compensation Limits % down very low.

[Qwktrip]

Danny, I tried your idea today, but the idle became weak and sometimes the engine died. I guess what I did in post #37 wasn't half bad after all for my LS style engine. It has been running downright good the last few days which is really encouraging.

[Danny Cabral]

Danny, I tried your idea today, but the idle became weak and sometimes the engine died.

Then you didn't try my idea from post #25. Maybe you tried my IEA idle values from post #41.
So you're supposed to enter an IEA idle value that works well, not a value that causes the engine to stall.
Step #1 is to enter your modified IEA idle value (LINK) in the top left corner cell (e.g. −190° or −130°).
Step #2 is to enter this same negative IEA idle value in the bottom left corner cell.